개념 설명 전체 · v6.6 / mm/vmscan.c
1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 4 * 5 * Swap reorganised 29.12.95, Stephen Tweedie. 6 * kswapd added: 7.1.96 sct 7 * Removed kswapd_ctl limits, and swap out as many pages as needed 8 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 9 * Zone aware kswapd started 02/00, Kanoj Sarcar ([email protected]). 10 * Multiqueue VM started 5.8.00, Rik van Riel. 11 */ 12 13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 14 15 #include <linux/mm.h> 16 #include <linux/sched/mm.h> 17 #include <linux/module.h> 18 #include <linux/gfp.h> 19 #include <linux/kernel_stat.h> 20 #include <linux/swap.h> 21 #include <linux/pagemap.h> 22 #include <linux/init.h> 23 #include <linux/highmem.h> 24 #include <linux/vmpressure.h> 25 #include <linux/vmstat.h> 26 #include <linux/file.h> 27 #include <linux/writeback.h> 28 #include <linux/blkdev.h> 29 #include <linux/buffer_head.h> /* for buffer_heads_over_limit */ 30 #include <linux/mm_inline.h> 31 #include <linux/backing-dev.h> 32 #include <linux/rmap.h> 33 #include <linux/topology.h> 34 #include <linux/cpu.h> 35 #include <linux/cpuset.h> 36 #include <linux/compaction.h> 37 #include <linux/notifier.h> 38 #include <linux/rwsem.h> 39 #include <linux/delay.h> 40 #include <linux/kthread.h> 41 #include <linux/freezer.h> 42 #include <linux/memcontrol.h> 43 #include <linux/migrate.h> 44 #include <linux/delayacct.h> 45 #include <linux/sysctl.h> 46 #include <linux/memory-tiers.h> 47 #include <linux/oom.h> 48 #include <linux/pagevec.h> 49 #include <linux/prefetch.h> 50 #include <linux/printk.h> 51 #include <linux/dax.h> 52 #include <linux/psi.h> 53 #include <linux/pagewalk.h> 54 #include <linux/shmem_fs.h> 55 #include <linux/ctype.h> 56 #include <linux/debugfs.h> 57 #include <linux/khugepaged.h> 58 #include <linux/rculist_nulls.h> 59 #include <linux/random.h> 60 61 #include <asm/tlbflush.h> 62 #include <asm/div64.h> 63 64 #include <linux/swapops.h> 65 #include <linux/balloon_compaction.h> 66 #include <linux/sched/sysctl.h> 67 68 #include "internal.h" 69 #include "swap.h" 70 71 #define CREATE_TRACE_POINTS 72 #include <trace/events/vmscan.h> 73 74 struct scan_control { 75 /* How many pages shrink_list() should reclaim */ 76 unsigned long nr_to_reclaim; 77 78 /* 79 * Nodemask of nodes allowed by the caller. If NULL, all nodes 80 * are scanned. 81 */ 82 nodemask_t *nodemask; 83 84 /* 85 * The memory cgroup that hit its limit and as a result is the 86 * primary target of this reclaim invocation. 87 */ 88 struct mem_cgroup *target_mem_cgroup; 89 90 /* 91 * Scan pressure balancing between anon and file LRUs 92 */ 93 unsigned long anon_cost; 94 unsigned long file_cost; 95 96 /* Can active folios be deactivated as part of reclaim? */ 97 #define DEACTIVATE_ANON 1 98 #define DEACTIVATE_FILE 2 99 unsigned int may_deactivate:2; 100 unsigned int force_deactivate:1; 101 unsigned int skipped_deactivate:1; 102 103 /* Writepage batching in laptop mode; RECLAIM_WRITE */ 104 unsigned int may_writepage:1; 105 106 /* Can mapped folios be reclaimed? */ 107 unsigned int may_unmap:1; 108 109 /* Can folios be swapped as part of reclaim? */ 110 unsigned int may_swap:1; 111 112 /* Proactive reclaim invoked by userspace through memory.reclaim */ 113 unsigned int proactive:1; 114 115 /* 116 * Cgroup memory below memory.low is protected as long as we 117 * don't threaten to OOM. If any cgroup is reclaimed at 118 * reduced force or passed over entirely due to its memory.low 119 * setting (memcg_low_skipped), and nothing is reclaimed as a 120 * result, then go back for one more cycle that reclaims the protected 121 * memory (memcg_low_reclaim) to avert OOM. 122 */ 123 unsigned int memcg_low_reclaim:1; 124 unsigned int memcg_low_skipped:1; 125 126 unsigned int hibernation_mode:1; 127 128 /* One of the zones is ready for compaction */ 129 unsigned int compaction_ready:1; 130 131 /* There is easily reclaimable cold cache in the current node */ 132 unsigned int cache_trim_mode:1; 133 134 /* The file folios on the current node are dangerously low */ 135 unsigned int file_is_tiny:1; 136 137 /* Always discard instead of demoting to lower tier memory */ 138 unsigned int no_demotion:1; 139 140 /* Allocation order */ 141 s8 order; 142 143 /* Scan (total_size >> priority) pages at once */ 144 s8 priority; 145 146 /* The highest zone to isolate folios for reclaim from */ 147 s8 reclaim_idx; 148 149 /* This context's GFP mask */ 150 gfp_t gfp_mask; 151 152 /* Incremented by the number of inactive pages that were scanned */ 153 unsigned long nr_scanned; 154 155 /* Number of pages freed so far during a call to shrink_zones() */ 156 unsigned long nr_reclaimed; 157 158 struct { 159 unsigned int dirty; 160 unsigned int unqueued_dirty; 161 unsigned int congested; 162 unsigned int writeback; 163 unsigned int immediate; 164 unsigned int file_taken; 165 unsigned int taken; 166 } nr; 167 168 /* for recording the reclaimed slab by now */ 169 struct reclaim_state reclaim_state; 170 }; 171 172 #ifdef ARCH_HAS_PREFETCHW 173 #define prefetchw_prev_lru_folio(_folio, _base, _field) \ 174 do { \ 175 if ((_folio)->lru.prev != _base) { \ 176 struct folio *prev; \ 177 \ 178 prev = lru_to_folio(&(_folio->lru)); \ 179 prefetchw(&prev->_field); \ 180 } \ 181 } while (0) 182 #else 183 #define prefetchw_prev_lru_folio(_folio, _base, _field) do { } while (0) 184 #endif 185 186 /* 187 * From 0 .. 200. Higher means more swappy. 188 */ 189 int vm_swappiness = 60; 190 191 LIST_HEAD(shrinker_list); 192 DECLARE_RWSEM(shrinker_rwsem); 193 194 #ifdef CONFIG_MEMCG 195 static int shrinker_nr_max; 196 197 /* The shrinker_info is expanded in a batch of BITS_PER_LONG */ 198 static inline int shrinker_map_size(int nr_items) 199 { 200 return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long)); 201 } 202 203 static inline int shrinker_defer_size(int nr_items) 204 { 205 return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t)); 206 } 207 208 static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg, 209 int nid) 210 { 211 return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info, 212 lockdep_is_held(&shrinker_rwsem)); 213 } 214 215 static int expand_one_shrinker_info(struct mem_cgroup *memcg, 216 int map_size, int defer_size, 217 int old_map_size, int old_defer_size, 218 int new_nr_max) 219 { 220 struct shrinker_info *new, *old; 221 struct mem_cgroup_per_node *pn; 222 int nid; 223 int size = map_size + defer_size; 224 225 for_each_node(nid) { 226 pn = memcg->nodeinfo[nid]; 227 old = shrinker_info_protected(memcg, nid); 228 /* Not yet online memcg */ 229 if (!old) 230 return 0; 231 232 /* Already expanded this shrinker_info */ 233 if (new_nr_max <= old->map_nr_max) 234 continue; 235 236 new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid); 237 if (!new) 238 return -ENOMEM; 239 240 new->nr_deferred = (atomic_long_t *)(new + 1); 241 new->map = (void *)new->nr_deferred + defer_size; 242 new->map_nr_max = new_nr_max; 243 244 /* map: set all old bits, clear all new bits */ 245 memset(new->map, (int)0xff, old_map_size); 246 memset((void *)new->map + old_map_size, 0, map_size - old_map_size); 247 /* nr_deferred: copy old values, clear all new values */ 248 memcpy(new->nr_deferred, old->nr_deferred, old_defer_size); 249 memset((void *)new->nr_deferred + old_defer_size, 0, 250 defer_size - old_defer_size); 251 252 rcu_assign_pointer(pn->shrinker_info, new); 253 kvfree_rcu(old, rcu); 254 } 255 256 return 0; 257 } 258 259 void free_shrinker_info(struct mem_cgroup *memcg) 260 { 261 struct mem_cgroup_per_node *pn; 262 struct shrinker_info *info; 263 int nid; 264 265 for_each_node(nid) { 266 pn = memcg->nodeinfo[nid]; 267 info = rcu_dereference_protected(pn->shrinker_info, true); 268 kvfree(info); 269 rcu_assign_pointer(pn->shrinker_info, NULL); 270 } 271 } 272 273 int alloc_shrinker_info(struct mem_cgroup *memcg) 274 { 275 struct shrinker_info *info; 276 int nid, size, ret = 0; 277 int map_size, defer_size = 0; 278 279 down_write(&shrinker_rwsem); 280 map_size = shrinker_map_size(shrinker_nr_max); 281 defer_size = shrinker_defer_size(shrinker_nr_max); 282 size = map_size + defer_size; 283 for_each_node(nid) { 284 info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid); 285 if (!info) { 286 free_shrinker_info(memcg); 287 ret = -ENOMEM; 288 break; 289 } 290 info->nr_deferred = (atomic_long_t *)(info + 1); 291 info->map = (void *)info->nr_deferred + defer_size; 292 info->map_nr_max = shrinker_nr_max; 293 rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info); 294 } 295 up_write(&shrinker_rwsem); 296 297 return ret; 298 } 299 300 static int expand_shrinker_info(int new_id) 301 { 302 int ret = 0; 303 int new_nr_max = round_up(new_id + 1, BITS_PER_LONG); 304 int map_size, defer_size = 0; 305 int old_map_size, old_defer_size = 0; 306 struct mem_cgroup *memcg; 307 308 if (!root_mem_cgroup) 309 goto out; 310 311 lockdep_assert_held(&shrinker_rwsem); 312 313 map_size = shrinker_map_size(new_nr_max); 314 defer_size = shrinker_defer_size(new_nr_max); 315 old_map_size = shrinker_map_size(shrinker_nr_max); 316 old_defer_size = shrinker_defer_size(shrinker_nr_max); 317 318 memcg = mem_cgroup_iter(NULL, NULL, NULL); 319 do { 320 ret = expand_one_shrinker_info(memcg, map_size, defer_size, 321 old_map_size, old_defer_size, 322 new_nr_max); 323 if (ret) { 324 mem_cgroup_iter_break(NULL, memcg); 325 goto out; 326 } 327 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); 328 out: 329 if (!ret) 330 shrinker_nr_max = new_nr_max; 331 332 return ret; 333 } 334 335 void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) 336 { 337 if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) { 338 struct shrinker_info *info; 339 340 rcu_read_lock(); 341 info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info); 342 if (!WARN_ON_ONCE(shrinker_id >= info->map_nr_max)) { 343 /* Pairs with smp mb in shrink_slab() */ 344 smp_mb__before_atomic(); 345 set_bit(shrinker_id, info->map); 346 } 347 rcu_read_unlock(); 348 } 349 } 350 351 static DEFINE_IDR(shrinker_idr); 352 353 static int prealloc_memcg_shrinker(struct shrinker *shrinker) 354 { 355 int id, ret = -ENOMEM; 356 357 if (mem_cgroup_disabled()) 358 return -ENOSYS; 359 360 down_write(&shrinker_rwsem); 361 /* This may call shrinker, so it must use down_read_trylock() */ 362 id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); 363 if (id < 0) 364 goto unlock; 365 366 if (id >= shrinker_nr_max) { 367 if (expand_shrinker_info(id)) { 368 idr_remove(&shrinker_idr, id); 369 goto unlock; 370 } 371 } 372 shrinker->id = id; 373 ret = 0; 374 unlock: 375 up_write(&shrinker_rwsem); 376 return ret; 377 } 378 379 static void unregister_memcg_shrinker(struct shrinker *shrinker) 380 { 381 int id = shrinker->id; 382 383 BUG_ON(id < 0); 384 385 lockdep_assert_held(&shrinker_rwsem); 386 387 idr_remove(&shrinker_idr, id); 388 } 389 390 static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker, 391 struct mem_cgroup *memcg) 392 { 393 struct shrinker_info *info; 394 395 info = shrinker_info_protected(memcg, nid); 396 return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0); 397 } 398 399 static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker, 400 struct mem_cgroup *memcg) 401 { 402 struct shrinker_info *info; 403 404 info = shrinker_info_protected(memcg, nid); 405 return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]); 406 } 407 408 void reparent_shrinker_deferred(struct mem_cgroup *memcg) 409 { 410 int i, nid; 411 long nr; 412 struct mem_cgroup *parent; 413 struct shrinker_info *child_info, *parent_info; 414 415 parent = parent_mem_cgroup(memcg); 416 if (!parent) 417 parent = root_mem_cgroup; 418 419 /* Prevent from concurrent shrinker_info expand */ 420 down_read(&shrinker_rwsem); 421 for_each_node(nid) { 422 child_info = shrinker_info_protected(memcg, nid); 423 parent_info = shrinker_info_protected(parent, nid); 424 for (i = 0; i < child_info->map_nr_max; i++) { 425 nr = atomic_long_read(&child_info->nr_deferred[i]); 426 atomic_long_add(nr, &parent_info->nr_deferred[i]); 427 } 428 } 429 up_read(&shrinker_rwsem); 430 } 431 432 /* Returns true for reclaim through cgroup limits or cgroup interfaces. */ 433 static bool cgroup_reclaim(struct scan_control *sc) 434 { 435 return sc->target_mem_cgroup; 436 } 437 438 /* 439 * Returns true for reclaim on the root cgroup. This is true for direct 440 * allocator reclaim and reclaim through cgroup interfaces on the root cgroup. 441 */ 442 static bool root_reclaim(struct scan_control *sc) 443 { 444 return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_mem_cgroup); 445 } 446 447 /** 448 * writeback_throttling_sane - is the usual dirty throttling mechanism available? 449 * @sc: scan_control in question 450 * 451 * The normal page dirty throttling mechanism in balance_dirty_pages() is 452 * completely broken with the legacy memcg and direct stalling in 453 * shrink_folio_list() is used for throttling instead, which lacks all the 454 * niceties such as fairness, adaptive pausing, bandwidth proportional 455 * allocation and configurability. 456 * 457 * This function tests whether the vmscan currently in progress can assume 458 * that the normal dirty throttling mechanism is operational. 459 */ 460 static bool writeback_throttling_sane(struct scan_control *sc) 461 { 462 if (!cgroup_reclaim(sc)) 463 return true; 464 #ifdef CONFIG_CGROUP_WRITEBACK 465 if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) 466 return true; 467 #endif 468 return false; 469 } 470 #else 471 static int prealloc_memcg_shrinker(struct shrinker *shrinker) 472 { 473 return -ENOSYS; 474 } 475 476 static void unregister_memcg_shrinker(struct shrinker *shrinker) 477 { 478 } 479 480 static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker, 481 struct mem_cgroup *memcg) 482 { 483 return 0; 484 } 485 486 static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker, 487 struct mem_cgroup *memcg) 488 { 489 return 0; 490 } 491 492 static bool cgroup_reclaim(struct scan_control *sc) 493 { 494 return false; 495 } 496 497 static bool root_reclaim(struct scan_control *sc) 498 { 499 return true; 500 } 501 502 static bool writeback_throttling_sane(struct scan_control *sc) 503 { 504 return true; 505 } 506 #endif 507 508 static void set_task_reclaim_state(struct task_struct *task, 509 struct reclaim_state *rs) 510 { 511 /* Check for an overwrite */ 512 WARN_ON_ONCE(rs && task->reclaim_state); 513 514 /* Check for the nulling of an already-nulled member */ 515 WARN_ON_ONCE(!rs && !task->reclaim_state); 516 517 task->reclaim_state = rs; 518 } 519 520 /* 521 * flush_reclaim_state(): add pages reclaimed outside of LRU-based reclaim to 522 * scan_control->nr_reclaimed. 523 */ 524 static void flush_reclaim_state(struct scan_control *sc) 525 { 526 /* 527 * Currently, reclaim_state->reclaimed includes three types of pages 528 * freed outside of vmscan: 529 * (1) Slab pages. 530 * (2) Clean file pages from pruned inodes (on highmem systems). 531 * (3) XFS freed buffer pages. 532 * 533 * For all of these cases, we cannot universally link the pages to a 534 * single memcg. For example, a memcg-aware shrinker can free one object 535 * charged to the target memcg, causing an entire page to be freed. 536 * If we count the entire page as reclaimed from the memcg, we end up 537 * overestimating the reclaimed amount (potentially under-reclaiming). 538 * 539 * Only count such pages for global reclaim to prevent under-reclaiming 540 * from the target memcg; preventing unnecessary retries during memcg 541 * charging and false positives from proactive reclaim. 542 * 543 * For uncommon cases where the freed pages were actually mostly 544 * charged to the target memcg, we end up underestimating the reclaimed 545 * amount. This should be fine. The freed pages will be uncharged 546 * anyway, even if they are not counted here properly, and we will be 547 * able to make forward progress in charging (which is usually in a 548 * retry loop). 549 * 550 * We can go one step further, and report the uncharged objcg pages in 551 * memcg reclaim, to make reporting more accurate and reduce 552 * underestimation, but it's probably not worth the complexity for now. 553 */ 554 if (current->reclaim_state && root_reclaim(sc)) { 555 sc->nr_reclaimed += current->reclaim_state->reclaimed; 556 current->reclaim_state->reclaimed = 0; 557 } 558 } 559 560 static long xchg_nr_deferred(struct shrinker *shrinker, 561 struct shrink_control *sc) 562 { 563 int nid = sc->nid; 564 565 if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) 566 nid = 0; 567 568 if (sc->memcg && 569 (shrinker->flags & SHRINKER_MEMCG_AWARE)) 570 return xchg_nr_deferred_memcg(nid, shrinker, 571 sc->memcg); 572 573 return atomic_long_xchg(&shrinker->nr_deferred[nid], 0); 574 } 575 576 577 static long add_nr_deferred(long nr, struct shrinker *shrinker, 578 struct shrink_control *sc) 579 { 580 int nid = sc->nid; 581 582 if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) 583 nid = 0; 584 585 if (sc->memcg && 586 (shrinker->flags & SHRINKER_MEMCG_AWARE)) 587 return add_nr_deferred_memcg(nr, nid, shrinker, 588 sc->memcg); 589 590 return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]); 591 } 592 593 static bool can_demote(int nid, struct scan_control *sc) 594 { 595 if (!numa_demotion_enabled) 596 return false; 597 if (sc && sc->no_demotion) 598 return false; 599 if (next_demotion_node(nid) == NUMA_NO_NODE) 600 return false; 601 602 return true; 603 } 604 605 static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg, 606 int nid, 607 struct scan_control *sc) 608 { 609 if (memcg == NULL) { 610 /* 611 * For non-memcg reclaim, is there 612 * space in any swap device? 613 */ 614 if (get_nr_swap_pages() > 0) 615 return true; 616 } else { 617 /* Is the memcg below its swap limit? */ 618 if (mem_cgroup_get_nr_swap_pages(memcg) > 0) 619 return true; 620 } 621 622 /* 623 * The page can not be swapped. 624 * 625 * Can it be reclaimed from this node via demotion? 626 */ 627 return can_demote(nid, sc); 628 } 629 630 /* 631 * This misses isolated folios which are not accounted for to save counters. 632 * As the data only determines if reclaim or compaction continues, it is 633 * not expected that isolated folios will be a dominating factor. 634 */ 635 unsigned long zone_reclaimable_pages(struct zone *zone) 636 { 637 unsigned long nr; 638 639 nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) + 640 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE); 641 if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL)) 642 nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) + 643 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON); 644 645 return nr; 646 } 647 648 /** 649 * lruvec_lru_size - Returns the number of pages on the given LRU list. 650 * @lruvec: lru vector 651 * @lru: lru to use 652 * @zone_idx: zones to consider (use MAX_NR_ZONES - 1 for the whole LRU list) 653 */ 654 static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, 655 int zone_idx) 656 { 657 unsigned long size = 0; 658 int zid; 659 660 for (zid = 0; zid <= zone_idx; zid++) { 661 struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid]; 662 663 if (!managed_zone(zone)) 664 continue; 665 666 if (!mem_cgroup_disabled()) 667 size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid); 668 else 669 size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru); 670 } 671 return size; 672 } 673 674 /* 675 * Add a shrinker callback to be called from the vm. 676 */ 677 static int __prealloc_shrinker(struct shrinker *shrinker) 678 { 679 unsigned int size; 680 int err; 681 682 if (shrinker->flags & SHRINKER_MEMCG_AWARE) { 683 err = prealloc_memcg_shrinker(shrinker); 684 if (err != -ENOSYS) 685 return err; 686 687 shrinker->flags &= ~SHRINKER_MEMCG_AWARE; 688 } 689 690 size = sizeof(*shrinker->nr_deferred); 691 if (shrinker->flags & SHRINKER_NUMA_AWARE) 692 size *= nr_node_ids; 693 694 shrinker->nr_deferred = kzalloc(size, GFP_KERNEL); 695 if (!shrinker->nr_deferred) 696 return -ENOMEM; 697 698 return 0; 699 } 700 701 #ifdef CONFIG_SHRINKER_DEBUG 702 int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...) 703 { 704 va_list ap; 705 int err; 706 707 va_start(ap, fmt); 708 shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap); 709 va_end(ap); 710 if (!shrinker->name) 711 return -ENOMEM; 712 713 err = __prealloc_shrinker(shrinker); 714 if (err) { 715 kfree_const(shrinker->name); 716 shrinker->name = NULL; 717 } 718 719 return err; 720 } 721 #else 722 int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...) 723 { 724 return __prealloc_shrinker(shrinker); 725 } 726 #endif 727 728 void free_prealloced_shrinker(struct shrinker *shrinker) 729 { 730 #ifdef CONFIG_SHRINKER_DEBUG 731 kfree_const(shrinker->name); 732 shrinker->name = NULL; 733 #endif 734 if (shrinker->flags & SHRINKER_MEMCG_AWARE) { 735 down_write(&shrinker_rwsem); 736 unregister_memcg_shrinker(shrinker); 737 up_write(&shrinker_rwsem); 738 return; 739 } 740 741 kfree(shrinker->nr_deferred); 742 shrinker->nr_deferred = NULL; 743 } 744 745 void register_shrinker_prepared(struct shrinker *shrinker) 746 { 747 down_write(&shrinker_rwsem); 748 list_add_tail(&shrinker->list, &shrinker_list); 749 shrinker->flags |= SHRINKER_REGISTERED; 750 shrinker_debugfs_add(shrinker); 751 up_write(&shrinker_rwsem); 752 } 753 754 static int __register_shrinker(struct shrinker *shrinker) 755 { 756 int err = __prealloc_shrinker(shrinker); 757 758 if (err) 759 return err; 760 register_shrinker_prepared(shrinker); 761 return 0; 762 } 763 764 #ifdef CONFIG_SHRINKER_DEBUG 765 int register_shrinker(struct shrinker *shrinker, const char *fmt, ...) 766 { 767 va_list ap; 768 int err; 769 770 va_start(ap, fmt); 771 shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap); 772 va_end(ap); 773 if (!shrinker->name) 774 return -ENOMEM; 775 776 err = __register_shrinker(shrinker); 777 if (err) { 778 kfree_const(shrinker->name); 779 shrinker->name = NULL; 780 } 781 return err; 782 } 783 #else 784 int register_shrinker(struct shrinker *shrinker, const char *fmt, ...) 785 { 786 return __register_shrinker(shrinker); 787 } 788 #endif 789 EXPORT_SYMBOL(register_shrinker); 790 791 /* 792 * Remove one 793 */ 794 void unregister_shrinker(struct shrinker *shrinker) 795 { 796 struct dentry *debugfs_entry; 797 int debugfs_id; 798 799 if (!(shrinker->flags & SHRINKER_REGISTERED)) 800 return; 801 802 down_write(&shrinker_rwsem); 803 list_del(&shrinker->list); 804 shrinker->flags &= ~SHRINKER_REGISTERED; 805 if (shrinker->flags & SHRINKER_MEMCG_AWARE) 806 unregister_memcg_shrinker(shrinker); 807 debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id); 808 up_write(&shrinker_rwsem); 809 810 shrinker_debugfs_remove(debugfs_entry, debugfs_id); 811 812 kfree(shrinker->nr_deferred); 813 shrinker->nr_deferred = NULL; 814 } 815 EXPORT_SYMBOL(unregister_shrinker); 816 817 /** 818 * synchronize_shrinkers - Wait for all running shrinkers to complete. 819 * 820 * This is equivalent to calling unregister_shrink() and register_shrinker(), 821 * but atomically and with less overhead. This is useful to guarantee that all 822 * shrinker invocations have seen an update, before freeing memory, similar to 823 * rcu. 824 */ 825 void synchronize_shrinkers(void) 826 { 827 down_write(&shrinker_rwsem); 828 up_write(&shrinker_rwsem); 829 } 830 EXPORT_SYMBOL(synchronize_shrinkers); 831 832 #define SHRINK_BATCH 128 833 834 static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, 835 struct shrinker *shrinker, int priority) 836 { 837 unsigned long freed = 0; 838 unsigned long long delta; 839 long total_scan; 840 long freeable; 841 long nr; 842 long new_nr; 843 long batch_size = shrinker->batch ? shrinker->batch 844 : SHRINK_BATCH; 845 long scanned = 0, next_deferred; 846 847 freeable = shrinker->count_objects(shrinker, shrinkctl); 848 if (freeable == 0 || freeable == SHRINK_EMPTY) 849 return freeable; 850 851 /* 852 * copy the current shrinker scan count into a local variable 853 * and zero it so that other concurrent shrinker invocations 854 * don't also do this scanning work. 855 */ 856 nr = xchg_nr_deferred(shrinker, shrinkctl); 857 858 if (shrinker->seeks) { 859 delta = freeable >> priority; 860 delta *= 4; 861 do_div(delta, shrinker->seeks); 862 } else { 863 /* 864 * These objects don't require any IO to create. Trim 865 * them aggressively under memory pressure to keep 866 * them from causing refetches in the IO caches. 867 */ 868 delta = freeable / 2; 869 } 870 871 total_scan = nr >> priority; 872 total_scan += delta; 873 total_scan = min(total_scan, (2 * freeable)); 874 875 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, 876 freeable, delta, total_scan, priority); 877 878 /* 879 * Normally, we should not scan less than batch_size objects in one 880 * pass to avoid too frequent shrinker calls, but if the slab has less 881 * than batch_size objects in total and we are really tight on memory, 882 * we will try to reclaim all available objects, otherwise we can end 883 * up failing allocations although there are plenty of reclaimable 884 * objects spread over several slabs with usage less than the 885 * batch_size. 886 * 887 * We detect the "tight on memory" situations by looking at the total 888 * number of objects we want to scan (total_scan). If it is greater 889 * than the total number of objects on slab (freeable), we must be 890 * scanning at high prio and therefore should try to reclaim as much as 891 * possible. 892 */ 893 while (total_scan >= batch_size || 894 total_scan >= freeable) { 895 unsigned long ret; 896 unsigned long nr_to_scan = min(batch_size, total_scan); 897 898 shrinkctl->nr_to_scan = nr_to_scan; 899 shrinkctl->nr_scanned = nr_to_scan; 900 ret = shrinker->scan_objects(shrinker, shrinkctl); 901 if (ret == SHRINK_STOP) 902 break; 903 freed += ret; 904 905 count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned); 906 total_scan -= shrinkctl->nr_scanned; 907 scanned += shrinkctl->nr_scanned; 908 909 cond_resched(); 910 } 911 912 /* 913 * The deferred work is increased by any new work (delta) that wasn't 914 * done, decreased by old deferred work that was done now. 915 * 916 * And it is capped to two times of the freeable items. 917 */ 918 next_deferred = max_t(long, (nr + delta - scanned), 0); 919 next_deferred = min(next_deferred, (2 * freeable)); 920 921 /* 922 * move the unused scan count back into the shrinker in a 923 * manner that handles concurrent updates. 924 */ 925 new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl); 926 927 trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan); 928 return freed; 929 } 930 931 #ifdef CONFIG_MEMCG 932 static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, 933 struct mem_cgroup *memcg, int priority) 934 { 935 struct shrinker_info *info; 936 unsigned long ret, freed = 0; 937 int i; 938 939 if (!mem_cgroup_online(memcg)) 940 return 0; 941 942 if (!down_read_trylock(&shrinker_rwsem)) 943 return 0; 944 945 info = shrinker_info_protected(memcg, nid); 946 if (unlikely(!info)) 947 goto unlock; 948 949 for_each_set_bit(i, info->map, info->map_nr_max) { 950 struct shrink_control sc = { 951 .gfp_mask = gfp_mask, 952 .nid = nid, 953 .memcg = memcg, 954 }; 955 struct shrinker *shrinker; 956 957 shrinker = idr_find(&shrinker_idr, i); 958 if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { 959 if (!shrinker) 960 clear_bit(i, info->map); 961 continue; 962 } 963 964 /* Call non-slab shrinkers even though kmem is disabled */ 965 if (!memcg_kmem_online() && 966 !(shrinker->flags & SHRINKER_NONSLAB)) 967 continue; 968 969 ret = do_shrink_slab(&sc, shrinker, priority); 970 if (ret == SHRINK_EMPTY) { 971 clear_bit(i, info->map); 972 /* 973 * After the shrinker reported that it had no objects to 974 * free, but before we cleared the corresponding bit in 975 * the memcg shrinker map, a new object might have been 976 * added. To make sure, we have the bit set in this 977 * case, we invoke the shrinker one more time and reset 978 * the bit if it reports that it is not empty anymore. 979 * The memory barrier here pairs with the barrier in 980 * set_shrinker_bit(): 981 * 982 * list_lru_add() shrink_slab_memcg() 983 * list_add_tail() clear_bit() 984 * <MB> <MB> 985 * set_bit() do_shrink_slab() 986 */ 987 smp_mb__after_atomic(); 988 ret = do_shrink_slab(&sc, shrinker, priority); 989 if (ret == SHRINK_EMPTY) 990 ret = 0; 991 else 992 set_shrinker_bit(memcg, nid, i); 993 } 994 freed += ret; 995 996 if (rwsem_is_contended(&shrinker_rwsem)) { 997 freed = freed ? : 1; 998 break; 999 } 1000 } 1001 unlock: 1002 up_read(&shrinker_rwsem); 1003 return freed; 1004 } 1005 #else /* CONFIG_MEMCG */ 1006 static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, 1007 struct mem_cgroup *memcg, int priority) 1008 { 1009 return 0; 1010 } 1011 #endif /* CONFIG_MEMCG */ 1012 1013 /** 1014 * shrink_slab - shrink slab caches 1015 * @gfp_mask: allocation context 1016 * @nid: node whose slab caches to target 1017 * @memcg: memory cgroup whose slab caches to target 1018 * @priority: the reclaim priority 1019 * 1020 * Call the shrink functions to age shrinkable caches. 1021 * 1022 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set, 1023 * unaware shrinkers will receive a node id of 0 instead. 1024 * 1025 * @memcg specifies the memory cgroup to target. Unaware shrinkers 1026 * are called only if it is the root cgroup. 1027 * 1028 * @priority is sc->priority, we take the number of objects and >> by priority 1029 * in order to get the scan target. 1030 * 1031 * Returns the number of reclaimed slab objects. 1032 */ 1033 static unsigned long shrink_slab(gfp_t gfp_mask, int nid, 1034 struct mem_cgroup *memcg, 1035 int priority) 1036 { 1037 unsigned long ret, freed = 0; 1038 struct shrinker *shrinker; 1039 1040 /* 1041 * The root memcg might be allocated even though memcg is disabled 1042 * via "cgroup_disable=memory" boot parameter. This could make 1043 * mem_cgroup_is_root() return false, then just run memcg slab 1044 * shrink, but skip global shrink. This may result in premature 1045 * oom. 1046 */ 1047 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg)) 1048 return shrink_slab_memcg(gfp_mask, nid, memcg, priority); 1049 1050 if (!down_read_trylock(&shrinker_rwsem)) 1051 goto out; 1052 1053 list_for_each_entry(shrinker, &shrinker_list, list) { 1054 struct shrink_control sc = { 1055 .gfp_mask = gfp_mask, 1056 .nid = nid, 1057 .memcg = memcg, 1058 }; 1059 1060 ret = do_shrink_slab(&sc, shrinker, priority); 1061 if (ret == SHRINK_EMPTY) 1062 ret = 0; 1063 freed += ret; 1064 /* 1065 * Bail out if someone want to register a new shrinker to 1066 * prevent the registration from being stalled for long periods 1067 * by parallel ongoing shrinking. 1068 */ 1069 if (rwsem_is_contended(&shrinker_rwsem)) { 1070 freed = freed ? : 1; 1071 break; 1072 } 1073 } 1074 1075 up_read(&shrinker_rwsem); 1076 out: 1077 cond_resched(); 1078 return freed; 1079 } 1080 1081 static unsigned long drop_slab_node(int nid) 1082 { 1083 unsigned long freed = 0; 1084 struct mem_cgroup *memcg = NULL; 1085 1086 memcg = mem_cgroup_iter(NULL, NULL, NULL); 1087 do { 1088 freed += shrink_slab(GFP_KERNEL, nid, memcg, 0); 1089 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); 1090 1091 return freed; 1092 } 1093 1094 void drop_slab(void) 1095 { 1096 int nid; 1097 int shift = 0; 1098 unsigned long freed; 1099 1100 do { 1101 freed = 0; 1102 for_each_online_node(nid) { 1103 if (fatal_signal_pending(current)) 1104 return; 1105 1106 freed += drop_slab_node(nid); 1107 } 1108 } while ((freed >> shift++) > 1); 1109 } 1110 1111 static int reclaimer_offset(void) 1112 { 1113 BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD != 1114 PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD); 1115 BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD != 1116 PGSCAN_DIRECT - PGSCAN_KSWAPD); 1117 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD != 1118 PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD); 1119 BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD != 1120 PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD); 1121 1122 if (current_is_kswapd()) 1123 return 0; 1124 if (current_is_khugepaged()) 1125 return PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD; 1126 return PGSTEAL_DIRECT - PGSTEAL_KSWAPD; 1127 } 1128 1129 static inline int is_page_cache_freeable(struct folio *folio) 1130 { 1131 /* 1132 * A freeable page cache folio is referenced only by the caller 1133 * that isolated the folio, the page cache and optional filesystem 1134 * private data at folio->private. 1135 */ 1136 return folio_ref_count(folio) - folio_test_private(folio) == 1137 1 + folio_nr_pages(folio); 1138 } 1139 1140 /* 1141 * We detected a synchronous write error writing a folio out. Probably 1142 * -ENOSPC. We need to propagate that into the address_space for a subsequent 1143 * fsync(), msync() or close(). 1144 * 1145 * The tricky part is that after writepage we cannot touch the mapping: nothing 1146 * prevents it from being freed up. But we have a ref on the folio and once 1147 * that folio is locked, the mapping is pinned. 1148 * 1149 * We're allowed to run sleeping folio_lock() here because we know the caller has 1150 * __GFP_FS. 1151 */ 1152 static void handle_write_error(struct address_space *mapping, 1153 struct folio *folio, int error) 1154 { 1155 folio_lock(folio); 1156 if (folio_mapping(folio) == mapping) 1157 mapping_set_error(mapping, error); 1158 folio_unlock(folio); 1159 } 1160 1161 static bool skip_throttle_noprogress(pg_data_t *pgdat) 1162 { 1163 int reclaimable = 0, write_pending = 0; 1164 int i; 1165 1166 /* 1167 * If kswapd is disabled, reschedule if necessary but do not 1168 * throttle as the system is likely near OOM. 1169 */ 1170 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) 1171 return true; 1172 1173 /* 1174 * If there are a lot of dirty/writeback folios then do not 1175 * throttle as throttling will occur when the folios cycle 1176 * towards the end of the LRU if still under writeback. 1177 */ 1178 for (i = 0; i < MAX_NR_ZONES; i++) { 1179 struct zone *zone = pgdat->node_zones + i; 1180 1181 if (!managed_zone(zone)) 1182 continue; 1183 1184 reclaimable += zone_reclaimable_pages(zone); 1185 write_pending += zone_page_state_snapshot(zone, 1186 NR_ZONE_WRITE_PENDING); 1187 } 1188 if (2 * write_pending <= reclaimable) 1189 return true; 1190 1191 return false; 1192 } 1193 1194 void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason) 1195 { 1196 wait_queue_head_t *wqh = &pgdat->reclaim_wait[reason]; 1197 long timeout, ret; 1198 DEFINE_WAIT(wait); 1199 1200 /* 1201 * Do not throttle user workers, kthreads other than kswapd or 1202 * workqueues. They may be required for reclaim to make 1203 * forward progress (e.g. journalling workqueues or kthreads). 1204 */ 1205 if (!current_is_kswapd() && 1206 current->flags & (PF_USER_WORKER|PF_KTHREAD)) { 1207 cond_resched(); 1208 return; 1209 } 1210 1211 /* 1212 * These figures are pulled out of thin air. 1213 * VMSCAN_THROTTLE_ISOLATED is a transient condition based on too many 1214 * parallel reclaimers which is a short-lived event so the timeout is 1215 * short. Failing to make progress or waiting on writeback are 1216 * potentially long-lived events so use a longer timeout. This is shaky 1217 * logic as a failure to make progress could be due to anything from 1218 * writeback to a slow device to excessive referenced folios at the tail 1219 * of the inactive LRU. 1220 */ 1221 switch(reason) { 1222 case VMSCAN_THROTTLE_WRITEBACK: 1223 timeout = HZ/10; 1224 1225 if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) { 1226 WRITE_ONCE(pgdat->nr_reclaim_start, 1227 node_page_state(pgdat, NR_THROTTLED_WRITTEN)); 1228 } 1229 1230 break; 1231 case VMSCAN_THROTTLE_CONGESTED: 1232 fallthrough; 1233 case VMSCAN_THROTTLE_NOPROGRESS: 1234 if (skip_throttle_noprogress(pgdat)) { 1235 cond_resched(); 1236 return; 1237 } 1238 1239 timeout = 1; 1240 1241 break; 1242 case VMSCAN_THROTTLE_ISOLATED: 1243 timeout = HZ/50; 1244 break; 1245 default: 1246 WARN_ON_ONCE(1); 1247 timeout = HZ; 1248 break; 1249 } 1250 1251 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); 1252 ret = schedule_timeout(timeout); 1253 finish_wait(wqh, &wait); 1254 1255 if (reason == VMSCAN_THROTTLE_WRITEBACK) 1256 atomic_dec(&pgdat->nr_writeback_throttled); 1257 1258 trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout), 1259 jiffies_to_usecs(timeout - ret), 1260 reason); 1261 } 1262 1263 /* 1264 * Account for folios written if tasks are throttled waiting on dirty 1265 * folios to clean. If enough folios have been cleaned since throttling 1266 * started then wakeup the throttled tasks. 1267 */ 1268 void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio, 1269 int nr_throttled) 1270 { 1271 unsigned long nr_written; 1272 1273 node_stat_add_folio(folio, NR_THROTTLED_WRITTEN); 1274 1275 /* 1276 * This is an inaccurate read as the per-cpu deltas may not 1277 * be synchronised. However, given that the system is 1278 * writeback throttled, it is not worth taking the penalty 1279 * of getting an accurate count. At worst, the throttle 1280 * timeout guarantees forward progress. 1281 */ 1282 nr_written = node_page_state(pgdat, NR_THROTTLED_WRITTEN) - 1283 READ_ONCE(pgdat->nr_reclaim_start); 1284 1285 if (nr_written > SWAP_CLUSTER_MAX * nr_throttled) 1286 wake_up(&pgdat->reclaim_wait[VMSCAN_THROTTLE_WRITEBACK]); 1287 } 1288 1289 /* possible outcome of pageout() */ 1290 typedef enum { 1291 /* failed to write folio out, folio is locked */ 1292 PAGE_KEEP, 1293 /* move folio to the active list, folio is locked */ 1294 PAGE_ACTIVATE, 1295 /* folio has been sent to the disk successfully, folio is unlocked */ 1296 PAGE_SUCCESS, 1297 /* folio is clean and locked */ 1298 PAGE_CLEAN, 1299 } pageout_t; 1300 1301 /* 1302 * pageout is called by shrink_folio_list() for each dirty folio. 1303 * Calls ->writepage(). 1304 */ 1305 static pageout_t pageout(struct folio *folio, struct address_space *mapping, 1306 struct swap_iocb **plug) 1307 { 1308 /* 1309 * If the folio is dirty, only perform writeback if that write 1310 * will be non-blocking. To prevent this allocation from being 1311 * stalled by pagecache activity. But note that there may be 1312 * stalls if we need to run get_block(). We could test 1313 * PagePrivate for that. 1314 * 1315 * If this process is currently in __generic_file_write_iter() against 1316 * this folio's queue, we can perform writeback even if that 1317 * will block. 1318 * 1319 * If the folio is swapcache, write it back even if that would 1320 * block, for some throttling. This happens by accident, because 1321 * swap_backing_dev_info is bust: it doesn't reflect the 1322 * congestion state of the swapdevs. Easy to fix, if needed. 1323 */ 1324 if (!is_page_cache_freeable(folio)) 1325 return PAGE_KEEP; 1326 if (!mapping) { 1327 /* 1328 * Some data journaling orphaned folios can have 1329 * folio->mapping == NULL while being dirty with clean buffers. 1330 */ 1331 if (folio_test_private(folio)) { 1332 if (try_to_free_buffers(folio)) { 1333 folio_clear_dirty(folio); 1334 pr_info("%s: orphaned folio\n", __func__); 1335 return PAGE_CLEAN; 1336 } 1337 } 1338 return PAGE_KEEP; 1339 } 1340 if (mapping->a_ops->writepage == NULL) 1341 return PAGE_ACTIVATE; 1342 1343 if (folio_clear_dirty_for_io(folio)) { 1344 int res; 1345 struct writeback_control wbc = { 1346 .sync_mode = WB_SYNC_NONE, 1347 .nr_to_write = SWAP_CLUSTER_MAX, 1348 .range_start = 0, 1349 .range_end = LLONG_MAX, 1350 .for_reclaim = 1, 1351 .swap_plug = plug, 1352 }; 1353 1354 folio_set_reclaim(folio); 1355 res = mapping->a_ops->writepage(&folio->page, &wbc); 1356 if (res < 0) 1357 handle_write_error(mapping, folio, res); 1358 if (res == AOP_WRITEPAGE_ACTIVATE) { 1359 folio_clear_reclaim(folio); 1360 return PAGE_ACTIVATE; 1361 } 1362 1363 if (!folio_test_writeback(folio)) { 1364 /* synchronous write or broken a_ops? */ 1365 folio_clear_reclaim(folio); 1366 } 1367 trace_mm_vmscan_write_folio(folio); 1368 node_stat_add_folio(folio, NR_VMSCAN_WRITE); 1369 return PAGE_SUCCESS; 1370 } 1371 1372 return PAGE_CLEAN; 1373 } 1374 1375 /* 1376 * Same as remove_mapping, but if the folio is removed from the mapping, it 1377 * gets returned with a refcount of 0. 1378 */ 1379 static int __remove_mapping(struct address_space *mapping, struct folio *folio, 1380 bool reclaimed, struct mem_cgroup *target_memcg) 1381 { 1382 int refcount; 1383 void *shadow = NULL; 1384 1385 BUG_ON(!folio_test_locked(folio)); 1386 BUG_ON(mapping != folio_mapping(folio)); 1387 1388 if (!folio_test_swapcache(folio)) 1389 spin_lock(&mapping->host->i_lock); 1390 xa_lock_irq(&mapping->i_pages); 1391 /* 1392 * The non racy check for a busy folio. 1393 * 1394 * Must be careful with the order of the tests. When someone has 1395 * a ref to the folio, it may be possible that they dirty it then 1396 * drop the reference. So if the dirty flag is tested before the 1397 * refcount here, then the following race may occur: 1398 * 1399 * get_user_pages(&page); 1400 * [user mapping goes away] 1401 * write_to(page); 1402 * !folio_test_dirty(folio) [good] 1403 * folio_set_dirty(folio); 1404 * folio_put(folio); 1405 * !refcount(folio) [good, discard it] 1406 * 1407 * [oops, our write_to data is lost] 1408 * 1409 * Reversing the order of the tests ensures such a situation cannot 1410 * escape unnoticed. The smp_rmb is needed to ensure the folio->flags 1411 * load is not satisfied before that of folio->_refcount. 1412 * 1413 * Note that if the dirty flag is always set via folio_mark_dirty, 1414 * and thus under the i_pages lock, then this ordering is not required. 1415 */ 1416 refcount = 1 + folio_nr_pages(folio); 1417 if (!folio_ref_freeze(folio, refcount)) 1418 goto cannot_free; 1419 /* note: atomic_cmpxchg in folio_ref_freeze provides the smp_rmb */ 1420 if (unlikely(folio_test_dirty(folio))) { 1421 folio_ref_unfreeze(folio, refcount); 1422 goto cannot_free; 1423 } 1424 1425 if (folio_test_swapcache(folio)) { 1426 swp_entry_t swap = folio->swap; 1427 1428 if (reclaimed && !mapping_exiting(mapping)) 1429 shadow = workingset_eviction(folio, target_memcg); 1430 __delete_from_swap_cache(folio, swap, shadow); 1431 mem_cgroup_swapout(folio, swap); 1432 xa_unlock_irq(&mapping->i_pages); 1433 put_swap_folio(folio, swap); 1434 } else { 1435 void (*free_folio)(struct folio *); 1436 1437 free_folio = mapping->a_ops->free_folio; 1438 /* 1439 * Remember a shadow entry for reclaimed file cache in 1440 * order to detect refaults, thus thrashing, later on. 1441 * 1442 * But don't store shadows in an address space that is 1443 * already exiting. This is not just an optimization, 1444 * inode reclaim needs to empty out the radix tree or 1445 * the nodes are lost. Don't plant shadows behind its 1446 * back. 1447 * 1448 * We also don't store shadows for DAX mappings because the 1449 * only page cache folios found in these are zero pages 1450 * covering holes, and because we don't want to mix DAX 1451 * exceptional entries and shadow exceptional entries in the 1452 * same address_space. 1453 */ 1454 if (reclaimed && folio_is_file_lru(folio) && 1455 !mapping_exiting(mapping) && !dax_mapping(mapping)) 1456 shadow = workingset_eviction(folio, target_memcg); 1457 __filemap_remove_folio(folio, shadow); 1458 xa_unlock_irq(&mapping->i_pages); 1459 if (mapping_shrinkable(mapping)) 1460 inode_add_lru(mapping->host); 1461 spin_unlock(&mapping->host->i_lock); 1462 1463 if (free_folio) 1464 free_folio(folio); 1465 } 1466 1467 return 1; 1468 1469 cannot_free: 1470 xa_unlock_irq(&mapping->i_pages); 1471 if (!folio_test_swapcache(folio)) 1472 spin_unlock(&mapping->host->i_lock); 1473 return 0; 1474 } 1475 1476 /** 1477 * remove_mapping() - Attempt to remove a folio from its mapping. 1478 * @mapping: The address space. 1479 * @folio: The folio to remove. 1480 * 1481 * If the folio is dirty, under writeback or if someone else has a ref 1482 * on it, removal will fail. 1483 * Return: The number of pages removed from the mapping. 0 if the folio 1484 * could not be removed. 1485 * Context: The caller should have a single refcount on the folio and 1486 * hold its lock. 1487 */ 1488 long remove_mapping(struct address_space *mapping, struct folio *folio) 1489 { 1490 if (__remove_mapping(mapping, folio, false, NULL)) { 1491 /* 1492 * Unfreezing the refcount with 1 effectively 1493 * drops the pagecache ref for us without requiring another 1494 * atomic operation. 1495 */ 1496 folio_ref_unfreeze(folio, 1); 1497 return folio_nr_pages(folio); 1498 } 1499 return 0; 1500 } 1501 1502 /** 1503 * folio_putback_lru - Put previously isolated folio onto appropriate LRU list. 1504 * @folio: Folio to be returned to an LRU list. 1505 * 1506 * Add previously isolated @folio to appropriate LRU list. 1507 * The folio may still be unevictable for other reasons. 1508 * 1509 * Context: lru_lock must not be held, interrupts must be enabled. 1510 */ 1511 void folio_putback_lru(struct folio *folio) 1512 { 1513 folio_add_lru(folio); 1514 folio_put(folio); /* drop ref from isolate */ 1515 } 1516 1517 enum folio_references { 1518 FOLIOREF_RECLAIM, 1519 FOLIOREF_RECLAIM_CLEAN, 1520 FOLIOREF_KEEP, 1521 FOLIOREF_ACTIVATE, 1522 }; 1523 1524 static enum folio_references folio_check_references(struct folio *folio, 1525 struct scan_control *sc) 1526 { 1527 int referenced_ptes, referenced_folio; 1528 unsigned long vm_flags; 1529 1530 referenced_ptes = folio_referenced(folio, 1, sc->target_mem_cgroup, 1531 &vm_flags); 1532 referenced_folio = folio_test_clear_referenced(folio); 1533 1534 /* 1535 * The supposedly reclaimable folio was found to be in a VM_LOCKED vma. 1536 * Let the folio, now marked Mlocked, be moved to the unevictable list. 1537 */ 1538 if (vm_flags & VM_LOCKED) 1539 return FOLIOREF_ACTIVATE; 1540 1541 /* rmap lock contention: rotate */ 1542 if (referenced_ptes == -1) 1543 return FOLIOREF_KEEP; 1544 1545 if (referenced_ptes) { 1546 /* 1547 * All mapped folios start out with page table 1548 * references from the instantiating fault, so we need 1549 * to look twice if a mapped file/anon folio is used more 1550 * than once. 1551 * 1552 * Mark it and spare it for another trip around the 1553 * inactive list. Another page table reference will 1554 * lead to its activation. 1555 * 1556 * Note: the mark is set for activated folios as well 1557 * so that recently deactivated but used folios are 1558 * quickly recovered. 1559 */ 1560 folio_set_referenced(folio); 1561 1562 if (referenced_folio || referenced_ptes > 1) 1563 return FOLIOREF_ACTIVATE; 1564 1565 /* 1566 * Activate file-backed executable folios after first usage. 1567 */ 1568 if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) 1569 return FOLIOREF_ACTIVATE; 1570 1571 return FOLIOREF_KEEP; 1572 } 1573 1574 /* Reclaim if clean, defer dirty folios to writeback */ 1575 if (referenced_folio && folio_is_file_lru(folio)) 1576 return FOLIOREF_RECLAIM_CLEAN; 1577 1578 return FOLIOREF_RECLAIM; 1579 } 1580 1581 /* Check if a folio is dirty or under writeback */ 1582 static void folio_check_dirty_writeback(struct folio *folio, 1583 bool *dirty, bool *writeback) 1584 { 1585 struct address_space *mapping; 1586 1587 /* 1588 * Anonymous folios are not handled by flushers and must be written 1589 * from reclaim context. Do not stall reclaim based on them. 1590 * MADV_FREE anonymous folios are put into inactive file list too. 1591 * They could be mistakenly treated as file lru. So further anon 1592 * test is needed. 1593 */ 1594 if (!folio_is_file_lru(folio) || 1595 (folio_test_anon(folio) && !folio_test_swapbacked(folio))) { 1596 *dirty = false; 1597 *writeback = false; 1598 return; 1599 } 1600 1601 /* By default assume that the folio flags are accurate */ 1602 *dirty = folio_test_dirty(folio); 1603 *writeback = folio_test_writeback(folio); 1604 1605 /* Verify dirty/writeback state if the filesystem supports it */ 1606 if (!folio_test_private(folio)) 1607 return; 1608 1609 mapping = folio_mapping(folio); 1610 if (mapping && mapping->a_ops->is_dirty_writeback) 1611 mapping->a_ops->is_dirty_writeback(folio, dirty, writeback); 1612 } 1613 1614 static struct folio *alloc_demote_folio(struct folio *src, 1615 unsigned long private) 1616 { 1617 struct folio *dst; 1618 nodemask_t *allowed_mask; 1619 struct migration_target_control *mtc; 1620 1621 mtc = (struct migration_target_control *)private; 1622 1623 allowed_mask = mtc->nmask; 1624 /* 1625 * make sure we allocate from the target node first also trying to 1626 * demote or reclaim pages from the target node via kswapd if we are 1627 * low on free memory on target node. If we don't do this and if 1628 * we have free memory on the slower(lower) memtier, we would start 1629 * allocating pages from slower(lower) memory tiers without even forcing 1630 * a demotion of cold pages from the target memtier. This can result 1631 * in the kernel placing hot pages in slower(lower) memory tiers. 1632 */ 1633 mtc->nmask = NULL; 1634 mtc->gfp_mask |= __GFP_THISNODE; 1635 dst = alloc_migration_target(src, (unsigned long)mtc); 1636 if (dst) 1637 return dst; 1638 1639 mtc->gfp_mask &= ~__GFP_THISNODE; 1640 mtc->nmask = allowed_mask; 1641 1642 return alloc_migration_target(src, (unsigned long)mtc); 1643 } 1644 1645 /* 1646 * Take folios on @demote_folios and attempt to demote them to another node. 1647 * Folios which are not demoted are left on @demote_folios. 1648 */ 1649 static unsigned int demote_folio_list(struct list_head *demote_folios, 1650 struct pglist_data *pgdat) 1651 { 1652 int target_nid = next_demotion_node(pgdat->node_id); 1653 unsigned int nr_succeeded; 1654 nodemask_t allowed_mask; 1655 1656 struct migration_target_control mtc = { 1657 /* 1658 * Allocate from 'node', or fail quickly and quietly. 1659 * When this happens, 'page' will likely just be discarded 1660 * instead of migrated. 1661 */ 1662 .gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) | __GFP_NOWARN | 1663 __GFP_NOMEMALLOC | GFP_NOWAIT, 1664 .nid = target_nid, 1665 .nmask = &allowed_mask 1666 }; 1667 1668 if (list_empty(demote_folios)) 1669 return 0; 1670 1671 if (target_nid == NUMA_NO_NODE) 1672 return 0; 1673 1674 node_get_allowed_targets(pgdat, &allowed_mask); 1675 1676 /* Demotion ignores all cpuset and mempolicy settings */ 1677 migrate_pages(demote_folios, alloc_demote_folio, NULL, 1678 (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION, 1679 &nr_succeeded); 1680 1681 __count_vm_events(PGDEMOTE_KSWAPD + reclaimer_offset(), nr_succeeded); 1682 1683 return nr_succeeded; 1684 } 1685 1686 static bool may_enter_fs(struct folio *folio, gfp_t gfp_mask) 1687 { 1688 if (gfp_mask & __GFP_FS) 1689 return true; 1690 if (!folio_test_swapcache(folio) || !(gfp_mask & __GFP_IO)) 1691 return false; 1692 /* 1693 * We can "enter_fs" for swap-cache with only __GFP_IO 1694 * providing this isn't SWP_FS_OPS. 1695 * ->flags can be updated non-atomicially (scan_swap_map_slots), 1696 * but that will never affect SWP_FS_OPS, so the data_race 1697 * is safe. 1698 */ 1699 return !data_race(folio_swap_flags(folio) & SWP_FS_OPS); 1700 } 1701 1702 /* 1703 * shrink_folio_list() returns the number of reclaimed pages 1704 */ 1705 static unsigned int shrink_folio_list(struct list_head *folio_list, 1706 struct pglist_data *pgdat, struct scan_control *sc, 1707 struct reclaim_stat *stat, bool ignore_references) 1708 { 1709 LIST_HEAD(ret_folios); 1710 LIST_HEAD(free_folios); 1711 LIST_HEAD(demote_folios); 1712 unsigned int nr_reclaimed = 0; 1713 unsigned int pgactivate = 0; 1714 bool do_demote_pass; 1715 struct swap_iocb *plug = NULL; 1716 1717 memset(stat, 0, sizeof(*stat)); 1718 cond_resched(); 1719 do_demote_pass = can_demote(pgdat->node_id, sc); 1720 1721 retry: 1722 while (!list_empty(folio_list)) { 1723 struct address_space *mapping; 1724 struct folio *folio; 1725 enum folio_references references = FOLIOREF_RECLAIM; 1726 bool dirty, writeback; 1727 unsigned int nr_pages; 1728 1729 cond_resched(); 1730 1731 folio = lru_to_folio(folio_list); 1732 list_del(&folio->lru); 1733 1734 if (!folio_trylock(folio)) 1735 goto keep; 1736 1737 VM_BUG_ON_FOLIO(folio_test_active(folio), folio); 1738 1739 nr_pages = folio_nr_pages(folio); 1740 1741 /* Account the number of base pages */ 1742 sc->nr_scanned += nr_pages; 1743 1744 if (unlikely(!folio_evictable(folio))) 1745 goto activate_locked; 1746 1747 if (!sc->may_unmap && folio_mapped(folio)) 1748 goto keep_locked; 1749 1750 /* folio_update_gen() tried to promote this page? */ 1751 if (lru_gen_enabled() && !ignore_references && 1752 folio_mapped(folio) && folio_test_referenced(folio)) 1753 goto keep_locked; 1754 1755 /* 1756 * The number of dirty pages determines if a node is marked 1757 * reclaim_congested. kswapd will stall and start writing 1758 * folios if the tail of the LRU is all dirty unqueued folios. 1759 */ 1760 folio_check_dirty_writeback(folio, &dirty, &writeback); 1761 if (dirty || writeback) 1762 stat->nr_dirty += nr_pages; 1763 1764 if (dirty && !writeback) 1765 stat->nr_unqueued_dirty += nr_pages; 1766 1767 /* 1768 * Treat this folio as congested if folios are cycling 1769 * through the LRU so quickly that the folios marked 1770 * for immediate reclaim are making it to the end of 1771 * the LRU a second time. 1772 */ 1773 if (writeback && folio_test_reclaim(folio)) 1774 stat->nr_congested += nr_pages; 1775 1776 /* 1777 * If a folio at the tail of the LRU is under writeback, there 1778 * are three cases to consider. 1779 * 1780 * 1) If reclaim is encountering an excessive number 1781 * of folios under writeback and this folio has both 1782 * the writeback and reclaim flags set, then it 1783 * indicates that folios are being queued for I/O but 1784 * are being recycled through the LRU before the I/O 1785 * can complete. Waiting on the folio itself risks an 1786 * indefinite stall if it is impossible to writeback 1787 * the folio due to I/O error or disconnected storage 1788 * so instead note that the LRU is being scanned too 1789 * quickly and the caller can stall after the folio 1790 * list has been processed. 1791 * 1792 * 2) Global or new memcg reclaim encounters a folio that is 1793 * not marked for immediate reclaim, or the caller does not 1794 * have __GFP_FS (or __GFP_IO if it's simply going to swap, 1795 * not to fs). In this case mark the folio for immediate 1796 * reclaim and continue scanning. 1797 * 1798 * Require may_enter_fs() because we would wait on fs, which 1799 * may not have submitted I/O yet. And the loop driver might 1800 * enter reclaim, and deadlock if it waits on a folio for 1801 * which it is needed to do the write (loop masks off 1802 * __GFP_IO|__GFP_FS for this reason); but more thought 1803 * would probably show more reasons. 1804 * 1805 * 3) Legacy memcg encounters a folio that already has the 1806 * reclaim flag set. memcg does not have any dirty folio 1807 * throttling so we could easily OOM just because too many 1808 * folios are in writeback and there is nothing else to 1809 * reclaim. Wait for the writeback to complete. 1810 * 1811 * In cases 1) and 2) we activate the folios to get them out of 1812 * the way while we continue scanning for clean folios on the 1813 * inactive list and refilling from the active list. The 1814 * observation here is that waiting for disk writes is more 1815 * expensive than potentially causing reloads down the line. 1816 * Since they're marked for immediate reclaim, they won't put 1817 * memory pressure on the cache working set any longer than it 1818 * takes to write them to disk. 1819 */ 1820 if (folio_test_writeback(folio)) { 1821 /* Case 1 above */ 1822 if (current_is_kswapd() && 1823 folio_test_reclaim(folio) && 1824 test_bit(PGDAT_WRITEBACK, &pgdat->flags)) { 1825 stat->nr_immediate += nr_pages; 1826 goto activate_locked; 1827 1828 /* Case 2 above */ 1829 } else if (writeback_throttling_sane(sc) || 1830 !folio_test_reclaim(folio) || 1831 !may_enter_fs(folio, sc->gfp_mask)) { 1832 /* 1833 * This is slightly racy - 1834 * folio_end_writeback() might have 1835 * just cleared the reclaim flag, then 1836 * setting the reclaim flag here ends up 1837 * interpreted as the readahead flag - but 1838 * that does not matter enough to care. 1839 * What we do want is for this folio to 1840 * have the reclaim flag set next time 1841 * memcg reclaim reaches the tests above, 1842 * so it will then wait for writeback to 1843 * avoid OOM; and it's also appropriate 1844 * in global reclaim. 1845 */ 1846 folio_set_reclaim(folio); 1847 stat->nr_writeback += nr_pages; 1848 goto activate_locked; 1849 1850 /* Case 3 above */ 1851 } else { 1852 folio_unlock(folio); 1853 folio_wait_writeback(folio); 1854 /* then go back and try same folio again */ 1855 list_add_tail(&folio->lru, folio_list); 1856 continue; 1857 } 1858 } 1859 1860 if (!ignore_references) 1861 references = folio_check_references(folio, sc); 1862 1863 switch (references) { 1864 case FOLIOREF_ACTIVATE: 1865 goto activate_locked; 1866 case FOLIOREF_KEEP: 1867 stat->nr_ref_keep += nr_pages; 1868 goto keep_locked; 1869 case FOLIOREF_RECLAIM: 1870 case FOLIOREF_RECLAIM_CLEAN: 1871 ; /* try to reclaim the folio below */ 1872 } 1873 1874 /* 1875 * Before reclaiming the folio, try to relocate 1876 * its contents to another node. 1877 */ 1878 if (do_demote_pass && 1879 (thp_migration_supported() || !folio_test_large(folio))) { 1880 list_add(&folio->lru, &demote_folios); 1881 folio_unlock(folio); 1882 continue; 1883 } 1884 1885 /* 1886 * Anonymous process memory has backing store? 1887 * Try to allocate it some swap space here. 1888 * Lazyfree folio could be freed directly 1889 */ 1890 if (folio_test_anon(folio) && folio_test_swapbacked(folio)) { 1891 if (!folio_test_swapcache(folio)) { 1892 if (!(sc->gfp_mask & __GFP_IO)) 1893 goto keep_locked; 1894 if (folio_maybe_dma_pinned(folio)) 1895 goto keep_locked; 1896 if (folio_test_large(folio)) { 1897 /* cannot split folio, skip it */ 1898 if (!can_split_folio(folio, NULL)) 1899 goto activate_locked; 1900 /* 1901 * Split folios without a PMD map right 1902 * away. Chances are some or all of the 1903 * tail pages can be freed without IO. 1904 */ 1905 if (!folio_entire_mapcount(folio) && 1906 split_folio_to_list(folio, 1907 folio_list)) 1908 goto activate_locked; 1909 } 1910 if (!add_to_swap(folio)) { 1911 if (!folio_test_large(folio)) 1912 goto activate_locked_split; 1913 /* Fallback to swap normal pages */ 1914 if (split_folio_to_list(folio, 1915 folio_list)) 1916 goto activate_locked; 1917 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 1918 count_vm_event(THP_SWPOUT_FALLBACK); 1919 #endif 1920 if (!add_to_swap(folio)) 1921 goto activate_locked_split; 1922 } 1923 } 1924 } else if (folio_test_swapbacked(folio) && 1925 folio_test_large(folio)) { 1926 /* Split shmem folio */ 1927 if (split_folio_to_list(folio, folio_list)) 1928 goto keep_locked; 1929 } 1930 1931 /* 1932 * If the folio was split above, the tail pages will make 1933 * their own pass through this function and be accounted 1934 * then. 1935 */ 1936 if ((nr_pages > 1) && !folio_test_large(folio)) { 1937 sc->nr_scanned -= (nr_pages - 1); 1938 nr_pages = 1; 1939 } 1940 1941 /* 1942 * The folio is mapped into the page tables of one or more 1943 * processes. Try to unmap it here. 1944 */ 1945 if (folio_mapped(folio)) { 1946 enum ttu_flags flags = TTU_BATCH_FLUSH; 1947 bool was_swapbacked = folio_test_swapbacked(folio); 1948 1949 if (folio_test_pmd_mappable(folio)) 1950 flags |= TTU_SPLIT_HUGE_PMD; 1951 1952 try_to_unmap(folio, flags); 1953 if (folio_mapped(folio)) { 1954 stat->nr_unmap_fail += nr_pages; 1955 if (!was_swapbacked && 1956 folio_test_swapbacked(folio)) 1957 stat->nr_lazyfree_fail += nr_pages; 1958 goto activate_locked; 1959 } 1960 } 1961 1962 /* 1963 * Folio is unmapped now so it cannot be newly pinned anymore. 1964 * No point in trying to reclaim folio if it is pinned. 1965 * Furthermore we don't want to reclaim underlying fs metadata 1966 * if the folio is pinned and thus potentially modified by the 1967 * pinning process as that may upset the filesystem. 1968 */ 1969 if (folio_maybe_dma_pinned(folio)) 1970 goto activate_locked; 1971 1972 mapping = folio_mapping(folio); 1973 if (folio_test_dirty(folio)) { 1974 /* 1975 * Only kswapd can writeback filesystem folios 1976 * to avoid risk of stack overflow. But avoid 1977 * injecting inefficient single-folio I/O into 1978 * flusher writeback as much as possible: only 1979 * write folios when we've encountered many 1980 * dirty folios, and when we've already scanned 1981 * the rest of the LRU for clean folios and see 1982 * the same dirty folios again (with the reclaim 1983 * flag set). 1984 */ 1985 if (folio_is_file_lru(folio) && 1986 (!current_is_kswapd() || 1987 !folio_test_reclaim(folio) || 1988 !test_bit(PGDAT_DIRTY, &pgdat->flags))) { 1989 /* 1990 * Immediately reclaim when written back. 1991 * Similar in principle to folio_deactivate() 1992 * except we already have the folio isolated 1993 * and know it's dirty 1994 */ 1995 node_stat_mod_folio(folio, NR_VMSCAN_IMMEDIATE, 1996 nr_pages); 1997 folio_set_reclaim(folio); 1998 1999 goto activate_locked; 2000 } 2001 2002 if (references == FOLIOREF_RECLAIM_CLEAN) 2003 goto keep_locked; 2004 if (!may_enter_fs(folio, sc->gfp_mask)) 2005 goto keep_locked; 2006 if (!sc->may_writepage) 2007 goto keep_locked; 2008 2009 /* 2010 * Folio is dirty. Flush the TLB if a writable entry 2011 * potentially exists to avoid CPU writes after I/O 2012 * starts and then write it out here. 2013 */ 2014 try_to_unmap_flush_dirty(); 2015 switch (pageout(folio, mapping, &plug)) { 2016 case PAGE_KEEP: 2017 goto keep_locked; 2018 case PAGE_ACTIVATE: 2019 goto activate_locked; 2020 case PAGE_SUCCESS: 2021 stat->nr_pageout += nr_pages; 2022 2023 if (folio_test_writeback(folio)) 2024 goto keep; 2025 if (folio_test_dirty(folio)) 2026 goto keep; 2027 2028 /* 2029 * A synchronous write - probably a ramdisk. Go 2030 * ahead and try to reclaim the folio. 2031 */ 2032 if (!folio_trylock(folio)) 2033 goto keep; 2034 if (folio_test_dirty(folio) || 2035 folio_test_writeback(folio)) 2036 goto keep_locked; 2037 mapping = folio_mapping(folio); 2038 fallthrough; 2039 case PAGE_CLEAN: 2040 ; /* try to free the folio below */ 2041 } 2042 } 2043 2044 /* 2045 * If the folio has buffers, try to free the buffer 2046 * mappings associated with this folio. If we succeed 2047 * we try to free the folio as well. 2048 * 2049 * We do this even if the folio is dirty. 2050 * filemap_release_folio() does not perform I/O, but it 2051 * is possible for a folio to have the dirty flag set, 2052 * but it is actually clean (all its buffers are clean). 2053 * This happens if the buffers were written out directly, 2054 * with submit_bh(). ext3 will do this, as well as 2055 * the blockdev mapping. filemap_release_folio() will 2056 * discover that cleanness and will drop the buffers 2057 * and mark the folio clean - it can be freed. 2058 * 2059 * Rarely, folios can have buffers and no ->mapping. 2060 * These are the folios which were not successfully 2061 * invalidated in truncate_cleanup_folio(). We try to 2062 * drop those buffers here and if that worked, and the 2063 * folio is no longer mapped into process address space 2064 * (refcount == 1) it can be freed. Otherwise, leave 2065 * the folio on the LRU so it is swappable. 2066 */ 2067 if (folio_needs_release(folio)) { 2068 if (!filemap_release_folio(folio, sc->gfp_mask)) 2069 goto activate_locked; 2070 if (!mapping && folio_ref_count(folio) == 1) { 2071 folio_unlock(folio); 2072 if (folio_put_testzero(folio)) 2073 goto free_it; 2074 else { 2075 /* 2076 * rare race with speculative reference. 2077 * the speculative reference will free 2078 * this folio shortly, so we may 2079 * increment nr_reclaimed here (and 2080 * leave it off the LRU). 2081 */ 2082 nr_reclaimed += nr_pages; 2083 continue; 2084 } 2085 } 2086 } 2087 2088 if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) { 2089 /* follow __remove_mapping for reference */ 2090 if (!folio_ref_freeze(folio, 1)) 2091 goto keep_locked; 2092 /* 2093 * The folio has only one reference left, which is 2094 * from the isolation. After the caller puts the 2095 * folio back on the lru and drops the reference, the 2096 * folio will be freed anyway. It doesn't matter 2097 * which lru it goes on. So we don't bother checking 2098 * the dirty flag here. 2099 */ 2100 count_vm_events(PGLAZYFREED, nr_pages); 2101 count_memcg_folio_events(folio, PGLAZYFREED, nr_pages); 2102 } else if (!mapping || !__remove_mapping(mapping, folio, true, 2103 sc->target_mem_cgroup)) 2104 goto keep_locked; 2105 2106 folio_unlock(folio); 2107 free_it: 2108 /* 2109 * Folio may get swapped out as a whole, need to account 2110 * all pages in it. 2111 */ 2112 nr_reclaimed += nr_pages; 2113 2114 /* 2115 * Is there need to periodically free_folio_list? It would 2116 * appear not as the counts should be low 2117 */ 2118 if (unlikely(folio_test_large(folio))) 2119 destroy_large_folio(folio); 2120 else 2121 list_add(&folio->lru, &free_folios); 2122 continue; 2123 2124 activate_locked_split: 2125 /* 2126 * The tail pages that are failed to add into swap cache 2127 * reach here. Fixup nr_scanned and nr_pages. 2128 */ 2129 if (nr_pages > 1) { 2130 sc->nr_scanned -= (nr_pages - 1); 2131 nr_pages = 1; 2132 } 2133 activate_locked: 2134 /* Not a candidate for swapping, so reclaim swap space. */ 2135 if (folio_test_swapcache(folio) && 2136 (mem_cgroup_swap_full(folio) || folio_test_mlocked(folio))) 2137 folio_free_swap(folio); 2138 VM_BUG_ON_FOLIO(folio_test_active(folio), folio); 2139 if (!folio_test_mlocked(folio)) { 2140 int type = folio_is_file_lru(folio); 2141 folio_set_active(folio); 2142 stat->nr_activate[type] += nr_pages; 2143 count_memcg_folio_events(folio, PGACTIVATE, nr_pages); 2144 } 2145 keep_locked: 2146 folio_unlock(folio); 2147 keep: 2148 list_add(&folio->lru, &ret_folios); 2149 VM_BUG_ON_FOLIO(folio_test_lru(folio) || 2150 folio_test_unevictable(folio), folio); 2151 } 2152 /* 'folio_list' is always empty here */ 2153 2154 /* Migrate folios selected for demotion */ 2155 nr_reclaimed += demote_folio_list(&demote_folios, pgdat); 2156 /* Folios that could not be demoted are still in @demote_folios */ 2157 if (!list_empty(&demote_folios)) { 2158 /* Folios which weren't demoted go back on @folio_list */ 2159 list_splice_init(&demote_folios, folio_list); 2160 2161 /* 2162 * goto retry to reclaim the undemoted folios in folio_list if 2163 * desired. 2164 * 2165 * Reclaiming directly from top tier nodes is not often desired 2166 * due to it breaking the LRU ordering: in general memory 2167 * should be reclaimed from lower tier nodes and demoted from 2168 * top tier nodes. 2169 * 2170 * However, disabling reclaim from top tier nodes entirely 2171 * would cause ooms in edge scenarios where lower tier memory 2172 * is unreclaimable for whatever reason, eg memory being 2173 * mlocked or too hot to reclaim. We can disable reclaim 2174 * from top tier nodes in proactive reclaim though as that is 2175 * not real memory pressure. 2176 */ 2177 if (!sc->proactive) { 2178 do_demote_pass = false; 2179 goto retry; 2180 } 2181 } 2182 2183 pgactivate = stat->nr_activate[0] + stat->nr_activate[1]; 2184 2185 mem_cgroup_uncharge_list(&free_folios); 2186 try_to_unmap_flush(); 2187 free_unref_page_list(&free_folios); 2188 2189 list_splice(&ret_folios, folio_list); 2190 count_vm_events(PGACTIVATE, pgactivate); 2191 2192 if (plug) 2193 swap_write_unplug(plug); 2194 return nr_reclaimed; 2195 } 2196 2197 unsigned int reclaim_clean_pages_from_list(struct zone *zone, 2198 struct list_head *folio_list) 2199 { 2200 struct scan_control sc = { 2201 .gfp_mask = GFP_KERNEL, 2202 .may_unmap = 1, 2203 }; 2204 struct reclaim_stat stat; 2205 unsigned int nr_reclaimed; 2206 struct folio *folio, *next; 2207 LIST_HEAD(clean_folios); 2208 unsigned int noreclaim_flag; 2209 2210 list_for_each_entry_safe(folio, next, folio_list, lru) { 2211 if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) && 2212 !folio_test_dirty(folio) && !__folio_test_movable(folio) && 2213 !folio_test_unevictable(folio)) { 2214 folio_clear_active(folio); 2215 list_move(&folio->lru, &clean_folios); 2216 } 2217 } 2218 2219 /* 2220 * We should be safe here since we are only dealing with file pages and 2221 * we are not kswapd and therefore cannot write dirty file pages. But 2222 * call memalloc_noreclaim_save() anyway, just in case these conditions 2223 * change in the future. 2224 */ 2225 noreclaim_flag = memalloc_noreclaim_save(); 2226 nr_reclaimed = shrink_folio_list(&clean_folios, zone->zone_pgdat, &sc, 2227 &stat, true); 2228 memalloc_noreclaim_restore(noreclaim_flag); 2229 2230 list_splice(&clean_folios, folio_list); 2231 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, 2232 -(long)nr_reclaimed); 2233 /* 2234 * Since lazyfree pages are isolated from file LRU from the beginning, 2235 * they will rotate back to anonymous LRU in the end if it failed to 2236 * discard so isolated count will be mismatched. 2237 * Compensate the isolated count for both LRU lists. 2238 */ 2239 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON, 2240 stat.nr_lazyfree_fail); 2241 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, 2242 -(long)stat.nr_lazyfree_fail); 2243 return nr_reclaimed; 2244 } 2245 2246 /* 2247 * Update LRU sizes after isolating pages. The LRU size updates must 2248 * be complete before mem_cgroup_update_lru_size due to a sanity check. 2249 */ 2250 static __always_inline void update_lru_sizes(struct lruvec *lruvec, 2251 enum lru_list lru, unsigned long *nr_zone_taken) 2252 { 2253 int zid; 2254 2255 for (zid = 0; zid < MAX_NR_ZONES; zid++) { 2256 if (!nr_zone_taken[zid]) 2257 continue; 2258 2259 update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]); 2260 } 2261 2262 } 2263 2264 #ifdef CONFIG_CMA 2265 /* 2266 * It is waste of effort to scan and reclaim CMA pages if it is not available 2267 * for current allocation context. Kswapd can not be enrolled as it can not 2268 * distinguish this scenario by using sc->gfp_mask = GFP_KERNEL 2269 */ 2270 static bool skip_cma(struct folio *folio, struct scan_control *sc) 2271 { 2272 return !current_is_kswapd() && 2273 gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE && 2274 get_pageblock_migratetype(&folio->page) == MIGRATE_CMA; 2275 } 2276 #else 2277 static bool skip_cma(struct folio *folio, struct scan_control *sc) 2278 { 2279 return false; 2280 } 2281 #endif 2282 2283 /* 2284 * Isolating page from the lruvec to fill in @dst list by nr_to_scan times. 2285 * 2286 * lruvec->lru_lock is heavily contended. Some of the functions that 2287 * shrink the lists perform better by taking out a batch of pages 2288 * and working on them outside the LRU lock. 2289 * 2290 * For pagecache intensive workloads, this function is the hottest 2291 * spot in the kernel (apart from copy_*_user functions). 2292 * 2293 * Lru_lock must be held before calling this function. 2294 * 2295 * @nr_to_scan: The number of eligible pages to look through on the list. 2296 * @lruvec: The LRU vector to pull pages from. 2297 * @dst: The temp list to put pages on to. 2298 * @nr_scanned: The number of pages that were scanned. 2299 * @sc: The scan_control struct for this reclaim session 2300 * @lru: LRU list id for isolating 2301 * 2302 * returns how many pages were moved onto *@dst. 2303 */ 2304 static unsigned long isolate_lru_folios(unsigned long nr_to_scan, 2305 struct lruvec *lruvec, struct list_head *dst, 2306 unsigned long *nr_scanned, struct scan_control *sc, 2307 enum lru_list lru) 2308 { 2309 struct list_head *src = &lruvec->lists[lru]; 2310 unsigned long nr_taken = 0; 2311 unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; 2312 unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; 2313 unsigned long skipped = 0; 2314 unsigned long scan, total_scan, nr_pages; 2315 LIST_HEAD(folios_skipped); 2316 2317 total_scan = 0; 2318 scan = 0; 2319 while (scan < nr_to_scan && !list_empty(src)) { 2320 struct list_head *move_to = src; 2321 struct folio *folio; 2322 2323 folio = lru_to_folio(src); 2324 prefetchw_prev_lru_folio(folio, src, flags); 2325 2326 nr_pages = folio_nr_pages(folio); 2327 total_scan += nr_pages; 2328 2329 if (folio_zonenum(folio) > sc->reclaim_idx || 2330 skip_cma(folio, sc)) { 2331 nr_skipped[folio_zonenum(folio)] += nr_pages; 2332 move_to = &folios_skipped; 2333 goto move; 2334 } 2335 2336 /* 2337 * Do not count skipped folios because that makes the function 2338 * return with no isolated folios if the LRU mostly contains 2339 * ineligible folios. This causes the VM to not reclaim any 2340 * folios, triggering a premature OOM. 2341 * Account all pages in a folio. 2342 */ 2343 scan += nr_pages; 2344 2345 if (!folio_test_lru(folio)) 2346 goto move; 2347 if (!sc->may_unmap && folio_mapped(folio)) 2348 goto move; 2349 2350 /* 2351 * Be careful not to clear the lru flag until after we're 2352 * sure the folio is not being freed elsewhere -- the 2353 * folio release code relies on it. 2354 */ 2355 if (unlikely(!folio_try_get(folio))) 2356 goto move; 2357 2358 if (!folio_test_clear_lru(folio)) { 2359 /* Another thread is already isolating this folio */ 2360 folio_put(folio); 2361 goto move; 2362 } 2363 2364 nr_taken += nr_pages; 2365 nr_zone_taken[folio_zonenum(folio)] += nr_pages; 2366 move_to = dst; 2367 move: 2368 list_move(&folio->lru, move_to); 2369 } 2370 2371 /* 2372 * Splice any skipped folios to the start of the LRU list. Note that 2373 * this disrupts the LRU order when reclaiming for lower zones but 2374 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX 2375 * scanning would soon rescan the same folios to skip and waste lots 2376 * of cpu cycles. 2377 */ 2378 if (!list_empty(&folios_skipped)) { 2379 int zid; 2380 2381 list_splice(&folios_skipped, src); 2382 for (zid = 0; zid < MAX_NR_ZONES; zid++) { 2383 if (!nr_skipped[zid]) 2384 continue; 2385 2386 __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); 2387 skipped += nr_skipped[zid]; 2388 } 2389 } 2390 *nr_scanned = total_scan; 2391 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, 2392 total_scan, skipped, nr_taken, 2393 sc->may_unmap ? 0 : ISOLATE_UNMAPPED, lru); 2394 update_lru_sizes(lruvec, lru, nr_zone_taken); 2395 return nr_taken; 2396 } 2397 2398 /** 2399 * folio_isolate_lru() - Try to isolate a folio from its LRU list. 2400 * @folio: Folio to isolate from its LRU list. 2401 * 2402 * Isolate a @folio from an LRU list and adjust the vmstat statistic 2403 * corresponding to whatever LRU list the folio was on. 2404 * 2405 * The folio will have its LRU flag cleared. If it was found on the 2406 * active list, it will have the Active flag set. If it was found on the 2407 * unevictable list, it will have the Unevictable flag set. These flags 2408 * may need to be cleared by the caller before letting the page go. 2409 * 2410 * Context: 2411 * 2412 * (1) Must be called with an elevated refcount on the folio. This is a 2413 * fundamental difference from isolate_lru_folios() (which is called 2414 * without a stable reference). 2415 * (2) The lru_lock must not be held. 2416 * (3) Interrupts must be enabled. 2417 * 2418 * Return: true if the folio was removed from an LRU list. 2419 * false if the folio was not on an LRU list. 2420 */ 2421 bool folio_isolate_lru(struct folio *folio) 2422 { 2423 bool ret = false; 2424 2425 VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio); 2426 2427 if (folio_test_clear_lru(folio)) { 2428 struct lruvec *lruvec; 2429 2430 folio_get(folio); 2431 lruvec = folio_lruvec_lock_irq(folio); 2432 lruvec_del_folio(lruvec, folio); 2433 unlock_page_lruvec_irq(lruvec); 2434 ret = true; 2435 } 2436 2437 return ret; 2438 } 2439 2440 /* 2441 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and 2442 * then get rescheduled. When there are massive number of tasks doing page 2443 * allocation, such sleeping direct reclaimers may keep piling up on each CPU, 2444 * the LRU list will go small and be scanned faster than necessary, leading to 2445 * unnecessary swapping, thrashing and OOM. 2446 */ 2447 static int too_many_isolated(struct pglist_data *pgdat, int file, 2448 struct scan_control *sc) 2449 { 2450 unsigned long inactive, isolated; 2451 bool too_many; 2452 2453 if (current_is_kswapd()) 2454 return 0; 2455 2456 if (!writeback_throttling_sane(sc)) 2457 return 0; 2458 2459 if (file) { 2460 inactive = node_page_state(pgdat, NR_INACTIVE_FILE); 2461 isolated = node_page_state(pgdat, NR_ISOLATED_FILE); 2462 } else { 2463 inactive = node_page_state(pgdat, NR_INACTIVE_ANON); 2464 isolated = node_page_state(pgdat, NR_ISOLATED_ANON); 2465 } 2466 2467 /* 2468 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they 2469 * won't get blocked by normal direct-reclaimers, forming a circular 2470 * deadlock. 2471 */ 2472 if (gfp_has_io_fs(sc->gfp_mask)) 2473 inactive >>= 3; 2474 2475 too_many = isolated > inactive; 2476 2477 /* Wake up tasks throttled due to too_many_isolated. */ 2478 if (!too_many) 2479 wake_throttle_isolated(pgdat); 2480 2481 return too_many; 2482 } 2483 2484 /* 2485 * move_folios_to_lru() moves folios from private @list to appropriate LRU list. 2486 * On return, @list is reused as a list of folios to be freed by the caller. 2487 * 2488 * Returns the number of pages moved to the given lruvec. 2489 */ 2490 static unsigned int move_folios_to_lru(struct lruvec *lruvec, 2491 struct list_head *list) 2492 { 2493 int nr_pages, nr_moved = 0; 2494 LIST_HEAD(folios_to_free); 2495 2496 while (!list_empty(list)) { 2497 struct folio *folio = lru_to_folio(list); 2498 2499 VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); 2500 list_del(&folio->lru); 2501 if (unlikely(!folio_evictable(folio))) { 2502 spin_unlock_irq(&lruvec->lru_lock); 2503 folio_putback_lru(folio); 2504 spin_lock_irq(&lruvec->lru_lock); 2505 continue; 2506 } 2507 2508 /* 2509 * The folio_set_lru needs to be kept here for list integrity. 2510 * Otherwise: 2511 * #0 move_folios_to_lru #1 release_pages 2512 * if (!folio_put_testzero()) 2513 * if (folio_put_testzero()) 2514 * !lru //skip lru_lock 2515 * folio_set_lru() 2516 * list_add(&folio->lru,) 2517 * list_add(&folio->lru,) 2518 */ 2519 folio_set_lru(folio); 2520 2521 if (unlikely(folio_put_testzero(folio))) { 2522 __folio_clear_lru_flags(folio); 2523 2524 if (unlikely(folio_test_large(folio))) { 2525 spin_unlock_irq(&lruvec->lru_lock); 2526 destroy_large_folio(folio); 2527 spin_lock_irq(&lruvec->lru_lock); 2528 } else 2529 list_add(&folio->lru, &folios_to_free); 2530 2531 continue; 2532 } 2533 2534 /* 2535 * All pages were isolated from the same lruvec (and isolation 2536 * inhibits memcg migration). 2537 */ 2538 VM_BUG_ON_FOLIO(!folio_matches_lruvec(folio, lruvec), folio); 2539 lruvec_add_folio(lruvec, folio); 2540 nr_pages = folio_nr_pages(folio); 2541 nr_moved += nr_pages; 2542 if (folio_test_active(folio)) 2543 workingset_age_nonresident(lruvec, nr_pages); 2544 } 2545 2546 /* 2547 * To save our caller's stack, now use input list for pages to free. 2548 */ 2549 list_splice(&folios_to_free, list); 2550 2551 return nr_moved; 2552 } 2553 2554 /* 2555 * If a kernel thread (such as nfsd for loop-back mounts) services a backing 2556 * device by writing to the page cache it sets PF_LOCAL_THROTTLE. In this case 2557 * we should not throttle. Otherwise it is safe to do so. 2558 */ 2559 static int current_may_throttle(void) 2560 { 2561 return !(current->flags & PF_LOCAL_THROTTLE); 2562 } 2563 2564 /* 2565 * shrink_inactive_list() is a helper for shrink_node(). It returns the number 2566 * of reclaimed pages 2567 */ 2568 static unsigned long shrink_inactive_list(unsigned long nr_to_scan, 2569 struct lruvec *lruvec, struct scan_control *sc, 2570 enum lru_list lru) 2571 { 2572 LIST_HEAD(folio_list); 2573 unsigned long nr_scanned; 2574 unsigned int nr_reclaimed = 0; 2575 unsigned long nr_taken; 2576 struct reclaim_stat stat; 2577 bool file = is_file_lru(lru); 2578 enum vm_event_item item; 2579 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 2580 bool stalled = false; 2581 2582 while (unlikely(too_many_isolated(pgdat, file, sc))) { 2583 if (stalled) 2584 return 0; 2585 2586 /* wait a bit for the reclaimer. */ 2587 stalled = true; 2588 reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED); 2589 2590 /* We are about to die and free our memory. Return now. */ 2591 if (fatal_signal_pending(current)) 2592 return SWAP_CLUSTER_MAX; 2593 } 2594 2595 lru_add_drain(); 2596 2597 spin_lock_irq(&lruvec->lru_lock); 2598 2599 nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &folio_list, 2600 &nr_scanned, sc, lru); 2601 2602 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); 2603 item = PGSCAN_KSWAPD + reclaimer_offset(); 2604 if (!cgroup_reclaim(sc)) 2605 __count_vm_events(item, nr_scanned); 2606 __count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned); 2607 __count_vm_events(PGSCAN_ANON + file, nr_scanned); 2608 2609 spin_unlock_irq(&lruvec->lru_lock); 2610 2611 if (nr_taken == 0) 2612 return 0; 2613 2614 nr_reclaimed = shrink_folio_list(&folio_list, pgdat, sc, &stat, false); 2615 2616 spin_lock_irq(&lruvec->lru_lock); 2617 move_folios_to_lru(lruvec, &folio_list); 2618 2619 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); 2620 item = PGSTEAL_KSWAPD + reclaimer_offset(); 2621 if (!cgroup_reclaim(sc)) 2622 __count_vm_events(item, nr_reclaimed); 2623 __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed); 2624 __count_vm_events(PGSTEAL_ANON + file, nr_reclaimed); 2625 spin_unlock_irq(&lruvec->lru_lock); 2626 2627 lru_note_cost(lruvec, file, stat.nr_pageout, nr_scanned - nr_reclaimed); 2628 mem_cgroup_uncharge_list(&folio_list); 2629 free_unref_page_list(&folio_list); 2630 2631 /* 2632 * If dirty folios are scanned that are not queued for IO, it 2633 * implies that flushers are not doing their job. This can 2634 * happen when memory pressure pushes dirty folios to the end of 2635 * the LRU before the dirty limits are breached and the dirty 2636 * data has expired. It can also happen when the proportion of 2637 * dirty folios grows not through writes but through memory 2638 * pressure reclaiming all the clean cache. And in some cases, 2639 * the flushers simply cannot keep up with the allocation 2640 * rate. Nudge the flusher threads in case they are asleep. 2641 */ 2642 if (stat.nr_unqueued_dirty == nr_taken) { 2643 wakeup_flusher_threads(WB_REASON_VMSCAN); 2644 /* 2645 * For cgroupv1 dirty throttling is achieved by waking up 2646 * the kernel flusher here and later waiting on folios 2647 * which are in writeback to finish (see shrink_folio_list()). 2648 * 2649 * Flusher may not be able to issue writeback quickly 2650 * enough for cgroupv1 writeback throttling to work 2651 * on a large system. 2652 */ 2653 if (!writeback_throttling_sane(sc)) 2654 reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); 2655 } 2656 2657 sc->nr.dirty += stat.nr_dirty; 2658 sc->nr.congested += stat.nr_congested; 2659 sc->nr.unqueued_dirty += stat.nr_unqueued_dirty; 2660 sc->nr.writeback += stat.nr_writeback; 2661 sc->nr.immediate += stat.nr_immediate; 2662 sc->nr.taken += nr_taken; 2663 if (file) 2664 sc->nr.file_taken += nr_taken; 2665 2666 trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, 2667 nr_scanned, nr_reclaimed, &stat, sc->priority, file); 2668 return nr_reclaimed; 2669 } 2670 2671 /* 2672 * shrink_active_list() moves folios from the active LRU to the inactive LRU. 2673 * 2674 * We move them the other way if the folio is referenced by one or more 2675 * processes. 2676 * 2677 * If the folios are mostly unmapped, the processing is fast and it is 2678 * appropriate to hold lru_lock across the whole operation. But if 2679 * the folios are mapped, the processing is slow (folio_referenced()), so 2680 * we should drop lru_lock around each folio. It's impossible to balance 2681 * this, so instead we remove the folios from the LRU while processing them. 2682 * It is safe to rely on the active flag against the non-LRU folios in here 2683 * because nobody will play with that bit on a non-LRU folio. 2684 * 2685 * The downside is that we have to touch folio->_refcount against each folio. 2686 * But we had to alter folio->flags anyway. 2687 */ 2688 static void shrink_active_list(unsigned long nr_to_scan, 2689 struct lruvec *lruvec, 2690 struct scan_control *sc, 2691 enum lru_list lru) 2692 { 2693 unsigned long nr_taken; 2694 unsigned long nr_scanned; 2695 unsigned long vm_flags; 2696 LIST_HEAD(l_hold); /* The folios which were snipped off */ 2697 LIST_HEAD(l_active); 2698 LIST_HEAD(l_inactive); 2699 unsigned nr_deactivate, nr_activate; 2700 unsigned nr_rotated = 0; 2701 int file = is_file_lru(lru); 2702 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 2703 2704 lru_add_drain(); 2705 2706 spin_lock_irq(&lruvec->lru_lock); 2707 2708 nr_taken = isolate_lru_folios(nr_to_scan, lruvec, &l_hold, 2709 &nr_scanned, sc, lru); 2710 2711 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); 2712 2713 if (!cgroup_reclaim(sc)) 2714 __count_vm_events(PGREFILL, nr_scanned); 2715 __count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned); 2716 2717 spin_unlock_irq(&lruvec->lru_lock); 2718 2719 while (!list_empty(&l_hold)) { 2720 struct folio *folio; 2721 2722 cond_resched(); 2723 folio = lru_to_folio(&l_hold); 2724 list_del(&folio->lru); 2725 2726 if (unlikely(!folio_evictable(folio))) { 2727 folio_putback_lru(folio); 2728 continue; 2729 } 2730 2731 if (unlikely(buffer_heads_over_limit)) { 2732 if (folio_needs_release(folio) && 2733 folio_trylock(folio)) { 2734 filemap_release_folio(folio, 0); 2735 folio_unlock(folio); 2736 } 2737 } 2738 2739 /* Referenced or rmap lock contention: rotate */ 2740 if (folio_referenced(folio, 0, sc->target_mem_cgroup, 2741 &vm_flags) != 0) { 2742 /* 2743 * Identify referenced, file-backed active folios and 2744 * give them one more trip around the active list. So 2745 * that executable code get better chances to stay in 2746 * memory under moderate memory pressure. Anon folios 2747 * are not likely to be evicted by use-once streaming 2748 * IO, plus JVM can create lots of anon VM_EXEC folios, 2749 * so we ignore them here. 2750 */ 2751 if ((vm_flags & VM_EXEC) && folio_is_file_lru(folio)) { 2752 nr_rotated += folio_nr_pages(folio); 2753 list_add(&folio->lru, &l_active); 2754 continue; 2755 } 2756 } 2757 2758 folio_clear_active(folio); /* we are de-activating */ 2759 folio_set_workingset(folio); 2760 list_add(&folio->lru, &l_inactive); 2761 } 2762 2763 /* 2764 * Move folios back to the lru list. 2765 */ 2766 spin_lock_irq(&lruvec->lru_lock); 2767 2768 nr_activate = move_folios_to_lru(lruvec, &l_active); 2769 nr_deactivate = move_folios_to_lru(lruvec, &l_inactive); 2770 /* Keep all free folios in l_active list */ 2771 list_splice(&l_inactive, &l_active); 2772 2773 __count_vm_events(PGDEACTIVATE, nr_deactivate); 2774 __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate); 2775 2776 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); 2777 spin_unlock_irq(&lruvec->lru_lock); 2778 2779 if (nr_rotated) 2780 lru_note_cost(lruvec, file, 0, nr_rotated); 2781 mem_cgroup_uncharge_list(&l_active); 2782 free_unref_page_list(&l_active); 2783 trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate, 2784 nr_deactivate, nr_rotated, sc->priority, file); 2785 } 2786 2787 static unsigned int reclaim_folio_list(struct list_head *folio_list, 2788 struct pglist_data *pgdat) 2789 { 2790 struct reclaim_stat dummy_stat; 2791 unsigned int nr_reclaimed; 2792 struct folio *folio; 2793 struct scan_control sc = { 2794 .gfp_mask = GFP_KERNEL, 2795 .may_writepage = 1, 2796 .may_unmap = 1, 2797 .may_swap = 1, 2798 .no_demotion = 1, 2799 }; 2800 2801 nr_reclaimed = shrink_folio_list(folio_list, pgdat, &sc, &dummy_stat, false); 2802 while (!list_empty(folio_list)) { 2803 folio = lru_to_folio(folio_list); 2804 list_del(&folio->lru); 2805 folio_putback_lru(folio); 2806 } 2807 2808 return nr_reclaimed; 2809 } 2810 2811 unsigned long reclaim_pages(struct list_head *folio_list) 2812 { 2813 int nid; 2814 unsigned int nr_reclaimed = 0; 2815 LIST_HEAD(node_folio_list); 2816 unsigned int noreclaim_flag; 2817 2818 if (list_empty(folio_list)) 2819 return nr_reclaimed; 2820 2821 noreclaim_flag = memalloc_noreclaim_save(); 2822 2823 nid = folio_nid(lru_to_folio(folio_list)); 2824 do { 2825 struct folio *folio = lru_to_folio(folio_list); 2826 2827 if (nid == folio_nid(folio)) { 2828 folio_clear_active(folio); 2829 list_move(&folio->lru, &node_folio_list); 2830 continue; 2831 } 2832 2833 nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid)); 2834 nid = folio_nid(lru_to_folio(folio_list)); 2835 } while (!list_empty(folio_list)); 2836 2837 nr_reclaimed += reclaim_folio_list(&node_folio_list, NODE_DATA(nid)); 2838 2839 memalloc_noreclaim_restore(noreclaim_flag); 2840 2841 return nr_reclaimed; 2842 } 2843 2844 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 2845 struct lruvec *lruvec, struct scan_control *sc) 2846 { 2847 if (is_active_lru(lru)) { 2848 if (sc->may_deactivate & (1 << is_file_lru(lru))) 2849 shrink_active_list(nr_to_scan, lruvec, sc, lru); 2850 else 2851 sc->skipped_deactivate = 1; 2852 return 0; 2853 } 2854 2855 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); 2856 } 2857 2858 /* 2859 * The inactive anon list should be small enough that the VM never has 2860 * to do too much work. 2861 * 2862 * The inactive file list should be small enough to leave most memory 2863 * to the established workingset on the scan-resistant active list, 2864 * but large enough to avoid thrashing the aggregate readahead window. 2865 * 2866 * Both inactive lists should also be large enough that each inactive 2867 * folio has a chance to be referenced again before it is reclaimed. 2868 * 2869 * If that fails and refaulting is observed, the inactive list grows. 2870 * 2871 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE folios 2872 * on this LRU, maintained by the pageout code. An inactive_ratio 2873 * of 3 means 3:1 or 25% of the folios are kept on the inactive list. 2874 * 2875 * total target max 2876 * memory ratio inactive 2877 * ------------------------------------- 2878 * 10MB 1 5MB 2879 * 100MB 1 50MB 2880 * 1GB 3 250MB 2881 * 10GB 10 0.9GB 2882 * 100GB 31 3GB 2883 * 1TB 101 10GB 2884 * 10TB 320 32GB 2885 */ 2886 static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru) 2887 { 2888 enum lru_list active_lru = inactive_lru + LRU_ACTIVE; 2889 unsigned long inactive, active; 2890 unsigned long inactive_ratio; 2891 unsigned long gb; 2892 2893 inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru); 2894 active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru); 2895 2896 gb = (inactive + active) >> (30 - PAGE_SHIFT); 2897 if (gb) 2898 inactive_ratio = int_sqrt(10 * gb); 2899 else 2900 inactive_ratio = 1; 2901 2902 return inactive * inactive_ratio < active; 2903 } 2904 2905 enum scan_balance { 2906 SCAN_EQUAL, 2907 SCAN_FRACT, 2908 SCAN_ANON, 2909 SCAN_FILE, 2910 }; 2911 2912 static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc) 2913 { 2914 unsigned long file; 2915 struct lruvec *target_lruvec; 2916 2917 if (lru_gen_enabled()) 2918 return; 2919 2920 target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); 2921 2922 /* 2923 * Flush the memory cgroup stats, so that we read accurate per-memcg 2924 * lruvec stats for heuristics. 2925 */ 2926 mem_cgroup_flush_stats(); 2927 2928 /* 2929 * Determine the scan balance between anon and file LRUs. 2930 */ 2931 spin_lock_irq(&target_lruvec->lru_lock); 2932 sc->anon_cost = target_lruvec->anon_cost; 2933 sc->file_cost = target_lruvec->file_cost; 2934 spin_unlock_irq(&target_lruvec->lru_lock); 2935 2936 /* 2937 * Target desirable inactive:active list ratios for the anon 2938 * and file LRU lists. 2939 */ 2940 if (!sc->force_deactivate) { 2941 unsigned long refaults; 2942 2943 /* 2944 * When refaults are being observed, it means a new 2945 * workingset is being established. Deactivate to get 2946 * rid of any stale active pages quickly. 2947 */ 2948 refaults = lruvec_page_state(target_lruvec, 2949 WORKINGSET_ACTIVATE_ANON); 2950 if (refaults != target_lruvec->refaults[WORKINGSET_ANON] || 2951 inactive_is_low(target_lruvec, LRU_INACTIVE_ANON)) 2952 sc->may_deactivate |= DEACTIVATE_ANON; 2953 else 2954 sc->may_deactivate &= ~DEACTIVATE_ANON; 2955 2956 refaults = lruvec_page_state(target_lruvec, 2957 WORKINGSET_ACTIVATE_FILE); 2958 if (refaults != target_lruvec->refaults[WORKINGSET_FILE] || 2959 inactive_is_low(target_lruvec, LRU_INACTIVE_FILE)) 2960 sc->may_deactivate |= DEACTIVATE_FILE; 2961 else 2962 sc->may_deactivate &= ~DEACTIVATE_FILE; 2963 } else 2964 sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE; 2965 2966 /* 2967 * If we have plenty of inactive file pages that aren't 2968 * thrashing, try to reclaim those first before touching 2969 * anonymous pages. 2970 */ 2971 file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE); 2972 if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE)) 2973 sc->cache_trim_mode = 1; 2974 else 2975 sc->cache_trim_mode = 0; 2976 2977 /* 2978 * Prevent the reclaimer from falling into the cache trap: as 2979 * cache pages start out inactive, every cache fault will tip 2980 * the scan balance towards the file LRU. And as the file LRU 2981 * shrinks, so does the window for rotation from references. 2982 * This means we have a runaway feedback loop where a tiny 2983 * thrashing file LRU becomes infinitely more attractive than 2984 * anon pages. Try to detect this based on file LRU size. 2985 */ 2986 if (!cgroup_reclaim(sc)) { 2987 unsigned long total_high_wmark = 0; 2988 unsigned long free, anon; 2989 int z; 2990 2991 free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES); 2992 file = node_page_state(pgdat, NR_ACTIVE_FILE) + 2993 node_page_state(pgdat, NR_INACTIVE_FILE); 2994 2995 for (z = 0; z < MAX_NR_ZONES; z++) { 2996 struct zone *zone = &pgdat->node_zones[z]; 2997 2998 if (!managed_zone(zone)) 2999 continue; 3000 3001 total_high_wmark += high_wmark_pages(zone); 3002 } 3003 3004 /* 3005 * Consider anon: if that's low too, this isn't a 3006 * runaway file reclaim problem, but rather just 3007 * extreme pressure. Reclaim as per usual then. 3008 */ 3009 anon = node_page_state(pgdat, NR_INACTIVE_ANON); 3010 3011 sc->file_is_tiny = 3012 file + free <= total_high_wmark && 3013 !(sc->may_deactivate & DEACTIVATE_ANON) && 3014 anon >> sc->priority; 3015 } 3016 } 3017 3018 /* 3019 * Determine how aggressively the anon and file LRU lists should be 3020 * scanned. 3021 * 3022 * nr[0] = anon inactive folios to scan; nr[1] = anon active folios to scan 3023 * nr[2] = file inactive folios to scan; nr[3] = file active folios to scan 3024 */ 3025 static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, 3026 unsigned long *nr) 3027 { 3028 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 3029 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 3030 unsigned long anon_cost, file_cost, total_cost; 3031 int swappiness = mem_cgroup_swappiness(memcg); 3032 u64 fraction[ANON_AND_FILE]; 3033 u64 denominator = 0; /* gcc */ 3034 enum scan_balance scan_balance; 3035 unsigned long ap, fp; 3036 enum lru_list lru; 3037 3038 /* If we have no swap space, do not bother scanning anon folios. */ 3039 if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) { 3040 scan_balance = SCAN_FILE; 3041 goto out; 3042 } 3043 3044 /* 3045 * Global reclaim will swap to prevent OOM even with no 3046 * swappiness, but memcg users want to use this knob to 3047 * disable swapping for individual groups completely when 3048 * using the memory controller's swap limit feature would be 3049 * too expensive. 3050 */ 3051 if (cgroup_reclaim(sc) && !swappiness) { 3052 scan_balance = SCAN_FILE; 3053 goto out; 3054 } 3055 3056 /* 3057 * Do not apply any pressure balancing cleverness when the 3058 * system is close to OOM, scan both anon and file equally 3059 * (unless the swappiness setting disagrees with swapping). 3060 */ 3061 if (!sc->priority && swappiness) { 3062 scan_balance = SCAN_EQUAL; 3063 goto out; 3064 } 3065 3066 /* 3067 * If the system is almost out of file pages, force-scan anon. 3068 */ 3069 if (sc->file_is_tiny) { 3070 scan_balance = SCAN_ANON; 3071 goto out; 3072 } 3073 3074 /* 3075 * If there is enough inactive page cache, we do not reclaim 3076 * anything from the anonymous working right now. 3077 */ 3078 if (sc->cache_trim_mode) { 3079 scan_balance = SCAN_FILE; 3080 goto out; 3081 } 3082 3083 scan_balance = SCAN_FRACT; 3084 /* 3085 * Calculate the pressure balance between anon and file pages. 3086 * 3087 * The amount of pressure we put on each LRU is inversely 3088 * proportional to the cost of reclaiming each list, as 3089 * determined by the share of pages that are refaulting, times 3090 * the relative IO cost of bringing back a swapped out 3091 * anonymous page vs reloading a filesystem page (swappiness). 3092 * 3093 * Although we limit that influence to ensure no list gets 3094 * left behind completely: at least a third of the pressure is 3095 * applied, before swappiness. 3096 * 3097 * With swappiness at 100, anon and file have equal IO cost. 3098 */ 3099 total_cost = sc->anon_cost + sc->file_cost; 3100 anon_cost = total_cost + sc->anon_cost; 3101 file_cost = total_cost + sc->file_cost; 3102 total_cost = anon_cost + file_cost; 3103 3104 ap = swappiness * (total_cost + 1); 3105 ap /= anon_cost + 1; 3106 3107 fp = (200 - swappiness) * (total_cost + 1); 3108 fp /= file_cost + 1; 3109 3110 fraction[0] = ap; 3111 fraction[1] = fp; 3112 denominator = ap + fp; 3113 out: 3114 for_each_evictable_lru(lru) { 3115 int file = is_file_lru(lru); 3116 unsigned long lruvec_size; 3117 unsigned long low, min; 3118 unsigned long scan; 3119 3120 lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); 3121 mem_cgroup_protection(sc->target_mem_cgroup, memcg, 3122 &min, &low); 3123 3124 if (min || low) { 3125 /* 3126 * Scale a cgroup's reclaim pressure by proportioning 3127 * its current usage to its memory.low or memory.min 3128 * setting. 3129 * 3130 * This is important, as otherwise scanning aggression 3131 * becomes extremely binary -- from nothing as we 3132 * approach the memory protection threshold, to totally 3133 * nominal as we exceed it. This results in requiring 3134 * setting extremely liberal protection thresholds. It 3135 * also means we simply get no protection at all if we 3136 * set it too low, which is not ideal. 3137 * 3138 * If there is any protection in place, we reduce scan 3139 * pressure by how much of the total memory used is 3140 * within protection thresholds. 3141 * 3142 * There is one special case: in the first reclaim pass, 3143 * we skip over all groups that are within their low 3144 * protection. If that fails to reclaim enough pages to 3145 * satisfy the reclaim goal, we come back and override 3146 * the best-effort low protection. However, we still 3147 * ideally want to honor how well-behaved groups are in 3148 * that case instead of simply punishing them all 3149 * equally. As such, we reclaim them based on how much 3150 * memory they are using, reducing the scan pressure 3151 * again by how much of the total memory used is under 3152 * hard protection. 3153 */ 3154 unsigned long cgroup_size = mem_cgroup_size(memcg); 3155 unsigned long protection; 3156 3157 /* memory.low scaling, make sure we retry before OOM */ 3158 if (!sc->memcg_low_reclaim && low > min) { 3159 protection = low; 3160 sc->memcg_low_skipped = 1; 3161 } else { 3162 protection = min; 3163 } 3164 3165 /* Avoid TOCTOU with earlier protection check */ 3166 cgroup_size = max(cgroup_size, protection); 3167 3168 scan = lruvec_size - lruvec_size * protection / 3169 (cgroup_size + 1); 3170 3171 /* 3172 * Minimally target SWAP_CLUSTER_MAX pages to keep 3173 * reclaim moving forwards, avoiding decrementing 3174 * sc->priority further than desirable. 3175 */ 3176 scan = max(scan, SWAP_CLUSTER_MAX); 3177 } else { 3178 scan = lruvec_size; 3179 } 3180 3181 scan >>= sc->priority; 3182 3183 /* 3184 * If the cgroup's already been deleted, make sure to 3185 * scrape out the remaining cache. 3186 */ 3187 if (!scan && !mem_cgroup_online(memcg)) 3188 scan = min(lruvec_size, SWAP_CLUSTER_MAX); 3189 3190 switch (scan_balance) { 3191 case SCAN_EQUAL: 3192 /* Scan lists relative to size */ 3193 break; 3194 case SCAN_FRACT: 3195 /* 3196 * Scan types proportional to swappiness and 3197 * their relative recent reclaim efficiency. 3198 * Make sure we don't miss the last page on 3199 * the offlined memory cgroups because of a 3200 * round-off error. 3201 */ 3202 scan = mem_cgroup_online(memcg) ? 3203 div64_u64(scan * fraction[file], denominator) : 3204 DIV64_U64_ROUND_UP(scan * fraction[file], 3205 denominator); 3206 break; 3207 case SCAN_FILE: 3208 case SCAN_ANON: 3209 /* Scan one type exclusively */ 3210 if ((scan_balance == SCAN_FILE) != file) 3211 scan = 0; 3212 break; 3213 default: 3214 /* Look ma, no brain */ 3215 BUG(); 3216 } 3217 3218 nr[lru] = scan; 3219 } 3220 } 3221 3222 /* 3223 * Anonymous LRU management is a waste if there is 3224 * ultimately no way to reclaim the memory. 3225 */ 3226 static bool can_age_anon_pages(struct pglist_data *pgdat, 3227 struct scan_control *sc) 3228 { 3229 /* Aging the anon LRU is valuable if swap is present: */ 3230 if (total_swap_pages > 0) 3231 return true; 3232 3233 /* Also valuable if anon pages can be demoted: */ 3234 return can_demote(pgdat->node_id, sc); 3235 } 3236 3237 #ifdef CONFIG_LRU_GEN 3238 3239 #ifdef CONFIG_LRU_GEN_ENABLED 3240 DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS); 3241 #define get_cap(cap) static_branch_likely(&lru_gen_caps[cap]) 3242 #else 3243 DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS); 3244 #define get_cap(cap) static_branch_unlikely(&lru_gen_caps[cap]) 3245 #endif 3246 3247 static bool should_walk_mmu(void) 3248 { 3249 return arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK); 3250 } 3251 3252 static bool should_clear_pmd_young(void) 3253 { 3254 return arch_has_hw_nonleaf_pmd_young() && get_cap(LRU_GEN_NONLEAF_YOUNG); 3255 } 3256 3257 /****************************************************************************** 3258 * shorthand helpers 3259 ******************************************************************************/ 3260 3261 #define LRU_REFS_FLAGS (BIT(PG_referenced) | BIT(PG_workingset)) 3262 3263 #define DEFINE_MAX_SEQ(lruvec) \ 3264 unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq) 3265 3266 #define DEFINE_MIN_SEQ(lruvec) \ 3267 unsigned long min_seq[ANON_AND_FILE] = { \ 3268 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \ 3269 READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \ 3270 } 3271 3272 #define for_each_gen_type_zone(gen, type, zone) \ 3273 for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \ 3274 for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \ 3275 for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++) 3276 3277 #define get_memcg_gen(seq) ((seq) % MEMCG_NR_GENS) 3278 #define get_memcg_bin(bin) ((bin) % MEMCG_NR_BINS) 3279 3280 static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid) 3281 { 3282 struct pglist_data *pgdat = NODE_DATA(nid); 3283 3284 #ifdef CONFIG_MEMCG 3285 if (memcg) { 3286 struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec; 3287 3288 /* see the comment in mem_cgroup_lruvec() */ 3289 if (!lruvec->pgdat) 3290 lruvec->pgdat = pgdat; 3291 3292 return lruvec; 3293 } 3294 #endif 3295 VM_WARN_ON_ONCE(!mem_cgroup_disabled()); 3296 3297 return &pgdat->__lruvec; 3298 } 3299 3300 static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc) 3301 { 3302 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 3303 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 3304 3305 if (!sc->may_swap) 3306 return 0; 3307 3308 if (!can_demote(pgdat->node_id, sc) && 3309 mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH) 3310 return 0; 3311 3312 return mem_cgroup_swappiness(memcg); 3313 } 3314 3315 static int get_nr_gens(struct lruvec *lruvec, int type) 3316 { 3317 return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1; 3318 } 3319 3320 static bool __maybe_unused seq_is_valid(struct lruvec *lruvec) 3321 { 3322 /* see the comment on lru_gen_folio */ 3323 return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS && 3324 get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) && 3325 get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS; 3326 } 3327 3328 /****************************************************************************** 3329 * Bloom filters 3330 ******************************************************************************/ 3331 3332 /* 3333 * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when 3334 * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of 3335 * bits in a bitmap, k is the number of hash functions and n is the number of 3336 * inserted items. 3337 * 3338 * Page table walkers use one of the two filters to reduce their search space. 3339 * To get rid of non-leaf entries that no longer have enough leaf entries, the 3340 * aging uses the double-buffering technique to flip to the other filter each 3341 * time it produces a new generation. For non-leaf entries that have enough 3342 * leaf entries, the aging carries them over to the next generation in 3343 * walk_pmd_range(); the eviction also report them when walking the rmap 3344 * in lru_gen_look_around(). 3345 * 3346 * For future optimizations: 3347 * 1. It's not necessary to keep both filters all the time. The spare one can be 3348 * freed after the RCU grace period and reallocated if needed again. 3349 * 2. And when reallocating, it's worth scaling its size according to the number 3350 * of inserted entries in the other filter, to reduce the memory overhead on 3351 * small systems and false positives on large systems. 3352 * 3. Jenkins' hash function is an alternative to Knuth's. 3353 */ 3354 #define BLOOM_FILTER_SHIFT 15 3355 3356 static inline int filter_gen_from_seq(unsigned long seq) 3357 { 3358 return seq % NR_BLOOM_FILTERS; 3359 } 3360 3361 static void get_item_key(void *item, int *key) 3362 { 3363 u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2); 3364 3365 BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32)); 3366 3367 key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1); 3368 key[1] = hash >> BLOOM_FILTER_SHIFT; 3369 } 3370 3371 static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item) 3372 { 3373 int key[2]; 3374 unsigned long *filter; 3375 int gen = filter_gen_from_seq(seq); 3376 3377 filter = READ_ONCE(lruvec->mm_state.filters[gen]); 3378 if (!filter) 3379 return true; 3380 3381 get_item_key(item, key); 3382 3383 return test_bit(key[0], filter) && test_bit(key[1], filter); 3384 } 3385 3386 static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item) 3387 { 3388 int key[2]; 3389 unsigned long *filter; 3390 int gen = filter_gen_from_seq(seq); 3391 3392 filter = READ_ONCE(lruvec->mm_state.filters[gen]); 3393 if (!filter) 3394 return; 3395 3396 get_item_key(item, key); 3397 3398 if (!test_bit(key[0], filter)) 3399 set_bit(key[0], filter); 3400 if (!test_bit(key[1], filter)) 3401 set_bit(key[1], filter); 3402 } 3403 3404 static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq) 3405 { 3406 unsigned long *filter; 3407 int gen = filter_gen_from_seq(seq); 3408 3409 filter = lruvec->mm_state.filters[gen]; 3410 if (filter) { 3411 bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT)); 3412 return; 3413 } 3414 3415 filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT), 3416 __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN); 3417 WRITE_ONCE(lruvec->mm_state.filters[gen], filter); 3418 } 3419 3420 /****************************************************************************** 3421 * mm_struct list 3422 ******************************************************************************/ 3423 3424 static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg) 3425 { 3426 static struct lru_gen_mm_list mm_list = { 3427 .fifo = LIST_HEAD_INIT(mm_list.fifo), 3428 .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock), 3429 }; 3430 3431 #ifdef CONFIG_MEMCG 3432 if (memcg) 3433 return &memcg->mm_list; 3434 #endif 3435 VM_WARN_ON_ONCE(!mem_cgroup_disabled()); 3436 3437 return &mm_list; 3438 } 3439 3440 void lru_gen_add_mm(struct mm_struct *mm) 3441 { 3442 int nid; 3443 struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm); 3444 struct lru_gen_mm_list *mm_list = get_mm_list(memcg); 3445 3446 VM_WARN_ON_ONCE(!list_empty(&mm->lru_gen.list)); 3447 #ifdef CONFIG_MEMCG 3448 VM_WARN_ON_ONCE(mm->lru_gen.memcg); 3449 mm->lru_gen.memcg = memcg; 3450 #endif 3451 spin_lock(&mm_list->lock); 3452 3453 for_each_node_state(nid, N_MEMORY) { 3454 struct lruvec *lruvec = get_lruvec(memcg, nid); 3455 3456 /* the first addition since the last iteration */ 3457 if (lruvec->mm_state.tail == &mm_list->fifo) 3458 lruvec->mm_state.tail = &mm->lru_gen.list; 3459 } 3460 3461 list_add_tail(&mm->lru_gen.list, &mm_list->fifo); 3462 3463 spin_unlock(&mm_list->lock); 3464 } 3465 3466 void lru_gen_del_mm(struct mm_struct *mm) 3467 { 3468 int nid; 3469 struct lru_gen_mm_list *mm_list; 3470 struct mem_cgroup *memcg = NULL; 3471 3472 if (list_empty(&mm->lru_gen.list)) 3473 return; 3474 3475 #ifdef CONFIG_MEMCG 3476 memcg = mm->lru_gen.memcg; 3477 #endif 3478 mm_list = get_mm_list(memcg); 3479 3480 spin_lock(&mm_list->lock); 3481 3482 for_each_node(nid) { 3483 struct lruvec *lruvec = get_lruvec(memcg, nid); 3484 3485 /* where the current iteration continues after */ 3486 if (lruvec->mm_state.head == &mm->lru_gen.list) 3487 lruvec->mm_state.head = lruvec->mm_state.head->prev; 3488 3489 /* where the last iteration ended before */ 3490 if (lruvec->mm_state.tail == &mm->lru_gen.list) 3491 lruvec->mm_state.tail = lruvec->mm_state.tail->next; 3492 } 3493 3494 list_del_init(&mm->lru_gen.list); 3495 3496 spin_unlock(&mm_list->lock); 3497 3498 #ifdef CONFIG_MEMCG 3499 mem_cgroup_put(mm->lru_gen.memcg); 3500 mm->lru_gen.memcg = NULL; 3501 #endif 3502 } 3503 3504 #ifdef CONFIG_MEMCG 3505 void lru_gen_migrate_mm(struct mm_struct *mm) 3506 { 3507 struct mem_cgroup *memcg; 3508 struct task_struct *task = rcu_dereference_protected(mm->owner, true); 3509 3510 VM_WARN_ON_ONCE(task->mm != mm); 3511 lockdep_assert_held(&task->alloc_lock); 3512 3513 /* for mm_update_next_owner() */ 3514 if (mem_cgroup_disabled()) 3515 return; 3516 3517 /* migration can happen before addition */ 3518 if (!mm->lru_gen.memcg) 3519 return; 3520 3521 rcu_read_lock(); 3522 memcg = mem_cgroup_from_task(task); 3523 rcu_read_unlock(); 3524 if (memcg == mm->lru_gen.memcg) 3525 return; 3526 3527 VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list)); 3528 3529 lru_gen_del_mm(mm); 3530 lru_gen_add_mm(mm); 3531 } 3532 #endif 3533 3534 static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last) 3535 { 3536 int i; 3537 int hist; 3538 3539 lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock); 3540 3541 if (walk) { 3542 hist = lru_hist_from_seq(walk->max_seq); 3543 3544 for (i = 0; i < NR_MM_STATS; i++) { 3545 WRITE_ONCE(lruvec->mm_state.stats[hist][i], 3546 lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]); 3547 walk->mm_stats[i] = 0; 3548 } 3549 } 3550 3551 if (NR_HIST_GENS > 1 && last) { 3552 hist = lru_hist_from_seq(lruvec->mm_state.seq + 1); 3553 3554 for (i = 0; i < NR_MM_STATS; i++) 3555 WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0); 3556 } 3557 } 3558 3559 static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk) 3560 { 3561 int type; 3562 unsigned long size = 0; 3563 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); 3564 int key = pgdat->node_id % BITS_PER_TYPE(mm->lru_gen.bitmap); 3565 3566 if (!walk->force_scan && !test_bit(key, &mm->lru_gen.bitmap)) 3567 return true; 3568 3569 clear_bit(key, &mm->lru_gen.bitmap); 3570 3571 for (type = !walk->can_swap; type < ANON_AND_FILE; type++) { 3572 size += type ? get_mm_counter(mm, MM_FILEPAGES) : 3573 get_mm_counter(mm, MM_ANONPAGES) + 3574 get_mm_counter(mm, MM_SHMEMPAGES); 3575 } 3576 3577 if (size < MIN_LRU_BATCH) 3578 return true; 3579 3580 return !mmget_not_zero(mm); 3581 } 3582 3583 static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, 3584 struct mm_struct **iter) 3585 { 3586 bool first = false; 3587 bool last = false; 3588 struct mm_struct *mm = NULL; 3589 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 3590 struct lru_gen_mm_list *mm_list = get_mm_list(memcg); 3591 struct lru_gen_mm_state *mm_state = &lruvec->mm_state; 3592 3593 /* 3594 * mm_state->seq is incremented after each iteration of mm_list. There 3595 * are three interesting cases for this page table walker: 3596 * 1. It tries to start a new iteration with a stale max_seq: there is 3597 * nothing left to do. 3598 * 2. It started the next iteration: it needs to reset the Bloom filter 3599 * so that a fresh set of PTE tables can be recorded. 3600 * 3. It ended the current iteration: it needs to reset the mm stats 3601 * counters and tell its caller to increment max_seq. 3602 */ 3603 spin_lock(&mm_list->lock); 3604 3605 VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->max_seq); 3606 3607 if (walk->max_seq <= mm_state->seq) 3608 goto done; 3609 3610 if (!mm_state->head) 3611 mm_state->head = &mm_list->fifo; 3612 3613 if (mm_state->head == &mm_list->fifo) 3614 first = true; 3615 3616 do { 3617 mm_state->head = mm_state->head->next; 3618 if (mm_state->head == &mm_list->fifo) { 3619 WRITE_ONCE(mm_state->seq, mm_state->seq + 1); 3620 last = true; 3621 break; 3622 } 3623 3624 /* force scan for those added after the last iteration */ 3625 if (!mm_state->tail || mm_state->tail == mm_state->head) { 3626 mm_state->tail = mm_state->head->next; 3627 walk->force_scan = true; 3628 } 3629 3630 mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list); 3631 if (should_skip_mm(mm, walk)) 3632 mm = NULL; 3633 } while (!mm); 3634 done: 3635 if (*iter || last) 3636 reset_mm_stats(lruvec, walk, last); 3637 3638 spin_unlock(&mm_list->lock); 3639 3640 if (mm && first) 3641 reset_bloom_filter(lruvec, walk->max_seq + 1); 3642 3643 if (*iter) 3644 mmput_async(*iter); 3645 3646 *iter = mm; 3647 3648 return last; 3649 } 3650 3651 static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq) 3652 { 3653 bool success = false; 3654 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 3655 struct lru_gen_mm_list *mm_list = get_mm_list(memcg); 3656 struct lru_gen_mm_state *mm_state = &lruvec->mm_state; 3657 3658 spin_lock(&mm_list->lock); 3659 3660 VM_WARN_ON_ONCE(mm_state->seq + 1 < max_seq); 3661 3662 if (max_seq > mm_state->seq) { 3663 mm_state->head = NULL; 3664 mm_state->tail = NULL; 3665 WRITE_ONCE(mm_state->seq, mm_state->seq + 1); 3666 reset_mm_stats(lruvec, NULL, true); 3667 success = true; 3668 } 3669 3670 spin_unlock(&mm_list->lock); 3671 3672 return success; 3673 } 3674 3675 /****************************************************************************** 3676 * PID controller 3677 ******************************************************************************/ 3678 3679 /* 3680 * A feedback loop based on Proportional-Integral-Derivative (PID) controller. 3681 * 3682 * The P term is refaulted/(evicted+protected) from a tier in the generation 3683 * currently being evicted; the I term is the exponential moving average of the 3684 * P term over the generations previously evicted, using the smoothing factor 3685 * 1/2; the D term isn't supported. 3686 * 3687 * The setpoint (SP) is always the first tier of one type; the process variable 3688 * (PV) is either any tier of the other type or any other tier of the same 3689 * type. 3690 * 3691 * The error is the difference between the SP and the PV; the correction is to 3692 * turn off protection when SP>PV or turn on protection when SP<PV. 3693 * 3694 * For future optimizations: 3695 * 1. The D term may discount the other two terms over time so that long-lived 3696 * generations can resist stale information. 3697 */ 3698 struct ctrl_pos { 3699 unsigned long refaulted; 3700 unsigned long total; 3701 int gain; 3702 }; 3703 3704 static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain, 3705 struct ctrl_pos *pos) 3706 { 3707 struct lru_gen_folio *lrugen = &lruvec->lrugen; 3708 int hist = lru_hist_from_seq(lrugen->min_seq[type]); 3709 3710 pos->refaulted = lrugen->avg_refaulted[type][tier] + 3711 atomic_long_read(&lrugen->refaulted[hist][type][tier]); 3712 pos->total = lrugen->avg_total[type][tier] + 3713 atomic_long_read(&lrugen->evicted[hist][type][tier]); 3714 if (tier) 3715 pos->total += lrugen->protected[hist][type][tier - 1]; 3716 pos->gain = gain; 3717 } 3718 3719 static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover) 3720 { 3721 int hist, tier; 3722 struct lru_gen_folio *lrugen = &lruvec->lrugen; 3723 bool clear = carryover ? NR_HIST_GENS == 1 : NR_HIST_GENS > 1; 3724 unsigned long seq = carryover ? lrugen->min_seq[type] : lrugen->max_seq + 1; 3725 3726 lockdep_assert_held(&lruvec->lru_lock); 3727 3728 if (!carryover && !clear) 3729 return; 3730 3731 hist = lru_hist_from_seq(seq); 3732 3733 for (tier = 0; tier < MAX_NR_TIERS; tier++) { 3734 if (carryover) { 3735 unsigned long sum; 3736 3737 sum = lrugen->avg_refaulted[type][tier] + 3738 atomic_long_read(&lrugen->refaulted[hist][type][tier]); 3739 WRITE_ONCE(lrugen->avg_refaulted[type][tier], sum / 2); 3740 3741 sum = lrugen->avg_total[type][tier] + 3742 atomic_long_read(&lrugen->evicted[hist][type][tier]); 3743 if (tier) 3744 sum += lrugen->protected[hist][type][tier - 1]; 3745 WRITE_ONCE(lrugen->avg_total[type][tier], sum / 2); 3746 } 3747 3748 if (clear) { 3749 atomic_long_set(&lrugen->refaulted[hist][type][tier], 0); 3750 atomic_long_set(&lrugen->evicted[hist][type][tier], 0); 3751 if (tier) 3752 WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 0); 3753 } 3754 } 3755 } 3756 3757 static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv) 3758 { 3759 /* 3760 * Return true if the PV has a limited number of refaults or a lower 3761 * refaulted/total than the SP. 3762 */ 3763 return pv->refaulted < MIN_LRU_BATCH || 3764 pv->refaulted * (sp->total + MIN_LRU_BATCH) * sp->gain <= 3765 (sp->refaulted + 1) * pv->total * pv->gain; 3766 } 3767 3768 /****************************************************************************** 3769 * the aging 3770 ******************************************************************************/ 3771 3772 /* promote pages accessed through page tables */ 3773 static int folio_update_gen(struct folio *folio, int gen) 3774 { 3775 unsigned long new_flags, old_flags = READ_ONCE(folio->flags); 3776 3777 VM_WARN_ON_ONCE(gen >= MAX_NR_GENS); 3778 VM_WARN_ON_ONCE(!rcu_read_lock_held()); 3779 3780 do { 3781 /* lru_gen_del_folio() has isolated this page? */ 3782 if (!(old_flags & LRU_GEN_MASK)) { 3783 /* for shrink_folio_list() */ 3784 new_flags = old_flags | BIT(PG_referenced); 3785 continue; 3786 } 3787 3788 new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS); 3789 new_flags |= (gen + 1UL) << LRU_GEN_PGOFF; 3790 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags)); 3791 3792 return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; 3793 } 3794 3795 /* protect pages accessed multiple times through file descriptors */ 3796 static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming) 3797 { 3798 int type = folio_is_file_lru(folio); 3799 struct lru_gen_folio *lrugen = &lruvec->lrugen; 3800 int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); 3801 unsigned long new_flags, old_flags = READ_ONCE(folio->flags); 3802 3803 VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio); 3804 3805 do { 3806 new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1; 3807 /* folio_update_gen() has promoted this page? */ 3808 if (new_gen >= 0 && new_gen != old_gen) 3809 return new_gen; 3810 3811 new_gen = (old_gen + 1) % MAX_NR_GENS; 3812 3813 new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_MASK | LRU_REFS_FLAGS); 3814 new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF; 3815 /* for folio_end_writeback() */ 3816 if (reclaiming) 3817 new_flags |= BIT(PG_reclaim); 3818 } while (!try_cmpxchg(&folio->flags, &old_flags, new_flags)); 3819 3820 lru_gen_update_size(lruvec, folio, old_gen, new_gen); 3821 3822 return new_gen; 3823 } 3824 3825 static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio, 3826 int old_gen, int new_gen) 3827 { 3828 int type = folio_is_file_lru(folio); 3829 int zone = folio_zonenum(folio); 3830 int delta = folio_nr_pages(folio); 3831 3832 VM_WARN_ON_ONCE(old_gen >= MAX_NR_GENS); 3833 VM_WARN_ON_ONCE(new_gen >= MAX_NR_GENS); 3834 3835 walk->batched++; 3836 3837 walk->nr_pages[old_gen][type][zone] -= delta; 3838 walk->nr_pages[new_gen][type][zone] += delta; 3839 } 3840 3841 static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk) 3842 { 3843 int gen, type, zone; 3844 struct lru_gen_folio *lrugen = &lruvec->lrugen; 3845 3846 walk->batched = 0; 3847 3848 for_each_gen_type_zone(gen, type, zone) { 3849 enum lru_list lru = type * LRU_INACTIVE_FILE; 3850 int delta = walk->nr_pages[gen][type][zone]; 3851 3852 if (!delta) 3853 continue; 3854 3855 walk->nr_pages[gen][type][zone] = 0; 3856 WRITE_ONCE(lrugen->nr_pages[gen][type][zone], 3857 lrugen->nr_pages[gen][type][zone] + delta); 3858 3859 if (lru_gen_is_active(lruvec, gen)) 3860 lru += LRU_ACTIVE; 3861 __update_lru_size(lruvec, lru, zone, delta); 3862 } 3863 } 3864 3865 static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *args) 3866 { 3867 struct address_space *mapping; 3868 struct vm_area_struct *vma = args->vma; 3869 struct lru_gen_mm_walk *walk = args->private; 3870 3871 if (!vma_is_accessible(vma)) 3872 return true; 3873 3874 if (is_vm_hugetlb_page(vma)) 3875 return true; 3876 3877 if (!vma_has_recency(vma)) 3878 return true; 3879 3880 if (vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) 3881 return true; 3882 3883 if (vma == get_gate_vma(vma->vm_mm)) 3884 return true; 3885 3886 if (vma_is_anonymous(vma)) 3887 return !walk->can_swap; 3888 3889 if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping)) 3890 return true; 3891 3892 mapping = vma->vm_file->f_mapping; 3893 if (mapping_unevictable(mapping)) 3894 return true; 3895 3896 if (shmem_mapping(mapping)) 3897 return !walk->can_swap; 3898 3899 /* to exclude special mappings like dax, etc. */ 3900 return !mapping->a_ops->read_folio; 3901 } 3902 3903 /* 3904 * Some userspace memory allocators map many single-page VMAs. Instead of 3905 * returning back to the PGD table for each of such VMAs, finish an entire PMD 3906 * table to reduce zigzags and improve cache performance. 3907 */ 3908 static bool get_next_vma(unsigned long mask, unsigned long size, struct mm_walk *args, 3909 unsigned long *vm_start, unsigned long *vm_end) 3910 { 3911 unsigned long start = round_up(*vm_end, size); 3912 unsigned long end = (start | ~mask) + 1; 3913 VMA_ITERATOR(vmi, args->mm, start); 3914 3915 VM_WARN_ON_ONCE(mask & size); 3916 VM_WARN_ON_ONCE((start & mask) != (*vm_start & mask)); 3917 3918 for_each_vma(vmi, args->vma) { 3919 if (end && end <= args->vma->vm_start) 3920 return false; 3921 3922 if (should_skip_vma(args->vma->vm_start, args->vma->vm_end, args)) 3923 continue; 3924 3925 *vm_start = max(start, args->vma->vm_start); 3926 *vm_end = min(end - 1, args->vma->vm_end - 1) + 1; 3927 3928 return true; 3929 } 3930 3931 return false; 3932 } 3933 3934 static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned long addr) 3935 { 3936 unsigned long pfn = pte_pfn(pte); 3937 3938 VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end); 3939 3940 if (!pte_present(pte) || is_zero_pfn(pfn)) 3941 return -1; 3942 3943 if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte))) 3944 return -1; 3945 3946 if (WARN_ON_ONCE(!pfn_valid(pfn))) 3947 return -1; 3948 3949 return pfn; 3950 } 3951 3952 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) 3953 static unsigned long get_pmd_pfn(pmd_t pmd, struct vm_area_struct *vma, unsigned long addr) 3954 { 3955 unsigned long pfn = pmd_pfn(pmd); 3956 3957 VM_WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end); 3958 3959 if (!pmd_present(pmd) || is_huge_zero_pmd(pmd)) 3960 return -1; 3961 3962 if (WARN_ON_ONCE(pmd_devmap(pmd))) 3963 return -1; 3964 3965 if (WARN_ON_ONCE(!pfn_valid(pfn))) 3966 return -1; 3967 3968 return pfn; 3969 } 3970 #endif 3971 3972 static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg, 3973 struct pglist_data *pgdat, bool can_swap) 3974 { 3975 struct folio *folio; 3976 3977 /* try to avoid unnecessary memory loads */ 3978 if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) 3979 return NULL; 3980 3981 folio = pfn_folio(pfn); 3982 if (folio_nid(folio) != pgdat->node_id) 3983 return NULL; 3984 3985 if (folio_memcg_rcu(folio) != memcg) 3986 return NULL; 3987 3988 /* file VMAs can contain anon pages from COW */ 3989 if (!folio_is_file_lru(folio) && !can_swap) 3990 return NULL; 3991 3992 return folio; 3993 } 3994 3995 static bool suitable_to_scan(int total, int young) 3996 { 3997 int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8); 3998 3999 /* suitable if the average number of young PTEs per cacheline is >=1 */ 4000 return young * n >= total; 4001 } 4002 4003 static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end, 4004 struct mm_walk *args) 4005 { 4006 int i; 4007 pte_t *pte; 4008 spinlock_t *ptl; 4009 unsigned long addr; 4010 int total = 0; 4011 int young = 0; 4012 struct lru_gen_mm_walk *walk = args->private; 4013 struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec); 4014 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); 4015 int old_gen, new_gen = lru_gen_from_seq(walk->max_seq); 4016 4017 pte = pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl); 4018 if (!pte) 4019 return false; 4020 if (!spin_trylock(ptl)) { 4021 pte_unmap(pte); 4022 return false; 4023 } 4024 4025 arch_enter_lazy_mmu_mode(); 4026 restart: 4027 for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) { 4028 unsigned long pfn; 4029 struct folio *folio; 4030 pte_t ptent = ptep_get(pte + i); 4031 4032 total++; 4033 walk->mm_stats[MM_LEAF_TOTAL]++; 4034 4035 pfn = get_pte_pfn(ptent, args->vma, addr); 4036 if (pfn == -1) 4037 continue; 4038 4039 if (!pte_young(ptent)) { 4040 walk->mm_stats[MM_LEAF_OLD]++; 4041 continue; 4042 } 4043 4044 folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); 4045 if (!folio) 4046 continue; 4047 4048 if (!ptep_test_and_clear_young(args->vma, addr, pte + i)) 4049 VM_WARN_ON_ONCE(true); 4050 4051 young++; 4052 walk->mm_stats[MM_LEAF_YOUNG]++; 4053 4054 if (pte_dirty(ptent) && !folio_test_dirty(folio) && 4055 !(folio_test_anon(folio) && folio_test_swapbacked(folio) && 4056 !folio_test_swapcache(folio))) 4057 folio_mark_dirty(folio); 4058 4059 old_gen = folio_update_gen(folio, new_gen); 4060 if (old_gen >= 0 && old_gen != new_gen) 4061 update_batch_size(walk, folio, old_gen, new_gen); 4062 } 4063 4064 if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end)) 4065 goto restart; 4066 4067 arch_leave_lazy_mmu_mode(); 4068 pte_unmap_unlock(pte, ptl); 4069 4070 return suitable_to_scan(total, young); 4071 } 4072 4073 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) 4074 static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma, 4075 struct mm_walk *args, unsigned long *bitmap, unsigned long *first) 4076 { 4077 int i; 4078 pmd_t *pmd; 4079 spinlock_t *ptl; 4080 struct lru_gen_mm_walk *walk = args->private; 4081 struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec); 4082 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); 4083 int old_gen, new_gen = lru_gen_from_seq(walk->max_seq); 4084 4085 VM_WARN_ON_ONCE(pud_leaf(*pud)); 4086 4087 /* try to batch at most 1+MIN_LRU_BATCH+1 entries */ 4088 if (*first == -1) { 4089 *first = addr; 4090 bitmap_zero(bitmap, MIN_LRU_BATCH); 4091 return; 4092 } 4093 4094 i = addr == -1 ? 0 : pmd_index(addr) - pmd_index(*first); 4095 if (i && i <= MIN_LRU_BATCH) { 4096 __set_bit(i - 1, bitmap); 4097 return; 4098 } 4099 4100 pmd = pmd_offset(pud, *first); 4101 4102 ptl = pmd_lockptr(args->mm, pmd); 4103 if (!spin_trylock(ptl)) 4104 goto done; 4105 4106 arch_enter_lazy_mmu_mode(); 4107 4108 do { 4109 unsigned long pfn; 4110 struct folio *folio; 4111 4112 /* don't round down the first address */ 4113 addr = i ? (*first & PMD_MASK) + i * PMD_SIZE : *first; 4114 4115 pfn = get_pmd_pfn(pmd[i], vma, addr); 4116 if (pfn == -1) 4117 goto next; 4118 4119 if (!pmd_trans_huge(pmd[i])) { 4120 if (should_clear_pmd_young()) 4121 pmdp_test_and_clear_young(vma, addr, pmd + i); 4122 goto next; 4123 } 4124 4125 folio = get_pfn_folio(pfn, memcg, pgdat, walk->can_swap); 4126 if (!folio) 4127 goto next; 4128 4129 if (!pmdp_test_and_clear_young(vma, addr, pmd + i)) 4130 goto next; 4131 4132 walk->mm_stats[MM_LEAF_YOUNG]++; 4133 4134 if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) && 4135 !(folio_test_anon(folio) && folio_test_swapbacked(folio) && 4136 !folio_test_swapcache(folio))) 4137 folio_mark_dirty(folio); 4138 4139 old_gen = folio_update_gen(folio, new_gen); 4140 if (old_gen >= 0 && old_gen != new_gen) 4141 update_batch_size(walk, folio, old_gen, new_gen); 4142 next: 4143 i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1; 4144 } while (i <= MIN_LRU_BATCH); 4145 4146 arch_leave_lazy_mmu_mode(); 4147 spin_unlock(ptl); 4148 done: 4149 *first = -1; 4150 } 4151 #else 4152 static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area_struct *vma, 4153 struct mm_walk *args, unsigned long *bitmap, unsigned long *first) 4154 { 4155 } 4156 #endif 4157 4158 static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, 4159 struct mm_walk *args) 4160 { 4161 int i; 4162 pmd_t *pmd; 4163 unsigned long next; 4164 unsigned long addr; 4165 struct vm_area_struct *vma; 4166 DECLARE_BITMAP(bitmap, MIN_LRU_BATCH); 4167 unsigned long first = -1; 4168 struct lru_gen_mm_walk *walk = args->private; 4169 4170 VM_WARN_ON_ONCE(pud_leaf(*pud)); 4171 4172 /* 4173 * Finish an entire PMD in two passes: the first only reaches to PTE 4174 * tables to avoid taking the PMD lock; the second, if necessary, takes 4175 * the PMD lock to clear the accessed bit in PMD entries. 4176 */ 4177 pmd = pmd_offset(pud, start & PUD_MASK); 4178 restart: 4179 /* walk_pte_range() may call get_next_vma() */ 4180 vma = args->vma; 4181 for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) { 4182 pmd_t val = pmdp_get_lockless(pmd + i); 4183 4184 next = pmd_addr_end(addr, end); 4185 4186 if (!pmd_present(val) || is_huge_zero_pmd(val)) { 4187 walk->mm_stats[MM_LEAF_TOTAL]++; 4188 continue; 4189 } 4190 4191 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 4192 if (pmd_trans_huge(val)) { 4193 unsigned long pfn = pmd_pfn(val); 4194 struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec); 4195 4196 walk->mm_stats[MM_LEAF_TOTAL]++; 4197 4198 if (!pmd_young(val)) { 4199 walk->mm_stats[MM_LEAF_OLD]++; 4200 continue; 4201 } 4202 4203 /* try to avoid unnecessary memory loads */ 4204 if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat)) 4205 continue; 4206 4207 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); 4208 continue; 4209 } 4210 #endif 4211 walk->mm_stats[MM_NONLEAF_TOTAL]++; 4212 4213 if (should_clear_pmd_young()) { 4214 if (!pmd_young(val)) 4215 continue; 4216 4217 walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); 4218 } 4219 4220 if (!walk->force_scan && !test_bloom_filter(walk->lruvec, walk->max_seq, pmd + i)) 4221 continue; 4222 4223 walk->mm_stats[MM_NONLEAF_FOUND]++; 4224 4225 if (!walk_pte_range(&val, addr, next, args)) 4226 continue; 4227 4228 walk->mm_stats[MM_NONLEAF_ADDED]++; 4229 4230 /* carry over to the next generation */ 4231 update_bloom_filter(walk->lruvec, walk->max_seq + 1, pmd + i); 4232 } 4233 4234 walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first); 4235 4236 if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &end)) 4237 goto restart; 4238 } 4239 4240 static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end, 4241 struct mm_walk *args) 4242 { 4243 int i; 4244 pud_t *pud; 4245 unsigned long addr; 4246 unsigned long next; 4247 struct lru_gen_mm_walk *walk = args->private; 4248 4249 VM_WARN_ON_ONCE(p4d_leaf(*p4d)); 4250 4251 pud = pud_offset(p4d, start & P4D_MASK); 4252 restart: 4253 for (i = pud_index(start), addr = start; addr != end; i++, addr = next) { 4254 pud_t val = READ_ONCE(pud[i]); 4255 4256 next = pud_addr_end(addr, end); 4257 4258 if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val))) 4259 continue; 4260 4261 walk_pmd_range(&val, addr, next, args); 4262 4263 if (need_resched() || walk->batched >= MAX_LRU_BATCH) { 4264 end = (addr | ~PUD_MASK) + 1; 4265 goto done; 4266 } 4267 } 4268 4269 if (i < PTRS_PER_PUD && get_next_vma(P4D_MASK, PUD_SIZE, args, &start, &end)) 4270 goto restart; 4271 4272 end = round_up(end, P4D_SIZE); 4273 done: 4274 if (!end || !args->vma) 4275 return 1; 4276 4277 walk->next_addr = max(end, args->vma->vm_start); 4278 4279 return -EAGAIN; 4280 } 4281 4282 static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk) 4283 { 4284 static const struct mm_walk_ops mm_walk_ops = { 4285 .test_walk = should_skip_vma, 4286 .p4d_entry = walk_pud_range, 4287 .walk_lock = PGWALK_RDLOCK, 4288 }; 4289 4290 int err; 4291 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 4292 4293 walk->next_addr = FIRST_USER_ADDRESS; 4294 4295 do { 4296 DEFINE_MAX_SEQ(lruvec); 4297 4298 err = -EBUSY; 4299 4300 /* another thread might have called inc_max_seq() */ 4301 if (walk->max_seq != max_seq) 4302 break; 4303 4304 /* folio_update_gen() requires stable folio_memcg() */ 4305 if (!mem_cgroup_trylock_pages(memcg)) 4306 break; 4307 4308 /* the caller might be holding the lock for write */ 4309 if (mmap_read_trylock(mm)) { 4310 err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk); 4311 4312 mmap_read_unlock(mm); 4313 } 4314 4315 mem_cgroup_unlock_pages(); 4316 4317 if (walk->batched) { 4318 spin_lock_irq(&lruvec->lru_lock); 4319 reset_batch_size(lruvec, walk); 4320 spin_unlock_irq(&lruvec->lru_lock); 4321 } 4322 4323 cond_resched(); 4324 } while (err == -EAGAIN); 4325 } 4326 4327 static struct lru_gen_mm_walk *set_mm_walk(struct pglist_data *pgdat, bool force_alloc) 4328 { 4329 struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk; 4330 4331 if (pgdat && current_is_kswapd()) { 4332 VM_WARN_ON_ONCE(walk); 4333 4334 walk = &pgdat->mm_walk; 4335 } else if (!walk && force_alloc) { 4336 VM_WARN_ON_ONCE(current_is_kswapd()); 4337 4338 walk = kzalloc(sizeof(*walk), __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN); 4339 } 4340 4341 current->reclaim_state->mm_walk = walk; 4342 4343 return walk; 4344 } 4345 4346 static void clear_mm_walk(void) 4347 { 4348 struct lru_gen_mm_walk *walk = current->reclaim_state->mm_walk; 4349 4350 VM_WARN_ON_ONCE(walk && memchr_inv(walk->nr_pages, 0, sizeof(walk->nr_pages))); 4351 VM_WARN_ON_ONCE(walk && memchr_inv(walk->mm_stats, 0, sizeof(walk->mm_stats))); 4352 4353 current->reclaim_state->mm_walk = NULL; 4354 4355 if (!current_is_kswapd()) 4356 kfree(walk); 4357 } 4358 4359 static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap) 4360 { 4361 int zone; 4362 int remaining = MAX_LRU_BATCH; 4363 struct lru_gen_folio *lrugen = &lruvec->lrugen; 4364 int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); 4365 4366 if (type == LRU_GEN_ANON && !can_swap) 4367 goto done; 4368 4369 /* prevent cold/hot inversion if force_scan is true */ 4370 for (zone = 0; zone < MAX_NR_ZONES; zone++) { 4371 struct list_head *head = &lrugen->folios[old_gen][type][zone]; 4372 4373 while (!list_empty(head)) { 4374 struct folio *folio = lru_to_folio(head); 4375 4376 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); 4377 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); 4378 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); 4379 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); 4380 4381 new_gen = folio_inc_gen(lruvec, folio, false); 4382 list_move_tail(&folio->lru, &lrugen->folios[new_gen][type][zone]); 4383 4384 if (!--remaining) 4385 return false; 4386 } 4387 } 4388 done: 4389 reset_ctrl_pos(lruvec, type, true); 4390 WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1); 4391 4392 return true; 4393 } 4394 4395 static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) 4396 { 4397 int gen, type, zone; 4398 bool success = false; 4399 struct lru_gen_folio *lrugen = &lruvec->lrugen; 4400 DEFINE_MIN_SEQ(lruvec); 4401 4402 VM_WARN_ON_ONCE(!seq_is_valid(lruvec)); 4403 4404 /* find the oldest populated generation */ 4405 for (type = !can_swap; type < ANON_AND_FILE; type++) { 4406 while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) { 4407 gen = lru_gen_from_seq(min_seq[type]); 4408 4409 for (zone = 0; zone < MAX_NR_ZONES; zone++) { 4410 if (!list_empty(&lrugen->folios[gen][type][zone])) 4411 goto next; 4412 } 4413 4414 min_seq[type]++; 4415 } 4416 next: 4417 ; 4418 } 4419 4420 /* see the comment on lru_gen_folio */ 4421 if (can_swap) { 4422 min_seq[LRU_GEN_ANON] = min(min_seq[LRU_GEN_ANON], min_seq[LRU_GEN_FILE]); 4423 min_seq[LRU_GEN_FILE] = max(min_seq[LRU_GEN_ANON], lrugen->min_seq[LRU_GEN_FILE]); 4424 } 4425 4426 for (type = !can_swap; type < ANON_AND_FILE; type++) { 4427 if (min_seq[type] == lrugen->min_seq[type]) 4428 continue; 4429 4430 reset_ctrl_pos(lruvec, type, true); 4431 WRITE_ONCE(lrugen->min_seq[type], min_seq[type]); 4432 success = true; 4433 } 4434 4435 return success; 4436 } 4437 4438 static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan) 4439 { 4440 int prev, next; 4441 int type, zone; 4442 struct lru_gen_folio *lrugen = &lruvec->lrugen; 4443 restart: 4444 spin_lock_irq(&lruvec->lru_lock); 4445 4446 VM_WARN_ON_ONCE(!seq_is_valid(lruvec)); 4447 4448 for (type = ANON_AND_FILE - 1; type >= 0; type--) { 4449 if (get_nr_gens(lruvec, type) != MAX_NR_GENS) 4450 continue; 4451 4452 VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap)); 4453 4454 if (inc_min_seq(lruvec, type, can_swap)) 4455 continue; 4456 4457 spin_unlock_irq(&lruvec->lru_lock); 4458 cond_resched(); 4459 goto restart; 4460 } 4461 4462 /* 4463 * Update the active/inactive LRU sizes for compatibility. Both sides of 4464 * the current max_seq need to be covered, since max_seq+1 can overlap 4465 * with min_seq[LRU_GEN_ANON] if swapping is constrained. And if they do 4466 * overlap, cold/hot inversion happens. 4467 */ 4468 prev = lru_gen_from_seq(lrugen->max_seq - 1); 4469 next = lru_gen_from_seq(lrugen->max_seq + 1); 4470 4471 for (type = 0; type < ANON_AND_FILE; type++) { 4472 for (zone = 0; zone < MAX_NR_ZONES; zone++) { 4473 enum lru_list lru = type * LRU_INACTIVE_FILE; 4474 long delta = lrugen->nr_pages[prev][type][zone] - 4475 lrugen->nr_pages[next][type][zone]; 4476 4477 if (!delta) 4478 continue; 4479 4480 __update_lru_size(lruvec, lru, zone, delta); 4481 __update_lru_size(lruvec, lru + LRU_ACTIVE, zone, -delta); 4482 } 4483 } 4484 4485 for (type = 0; type < ANON_AND_FILE; type++) 4486 reset_ctrl_pos(lruvec, type, false); 4487 4488 WRITE_ONCE(lrugen->timestamps[next], jiffies); 4489 /* make sure preceding modifications appear */ 4490 smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1); 4491 4492 spin_unlock_irq(&lruvec->lru_lock); 4493 } 4494 4495 static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, 4496 struct scan_control *sc, bool can_swap, bool force_scan) 4497 { 4498 bool success; 4499 struct lru_gen_mm_walk *walk; 4500 struct mm_struct *mm = NULL; 4501 struct lru_gen_folio *lrugen = &lruvec->lrugen; 4502 4503 VM_WARN_ON_ONCE(max_seq > READ_ONCE(lrugen->max_seq)); 4504 4505 /* see the comment in iterate_mm_list() */ 4506 if (max_seq <= READ_ONCE(lruvec->mm_state.seq)) { 4507 success = false; 4508 goto done; 4509 } 4510 4511 /* 4512 * If the hardware doesn't automatically set the accessed bit, fallback 4513 * to lru_gen_look_around(), which only clears the accessed bit in a 4514 * handful of PTEs. Spreading the work out over a period of time usually 4515 * is less efficient, but it avoids bursty page faults. 4516 */ 4517 if (!should_walk_mmu()) { 4518 success = iterate_mm_list_nowalk(lruvec, max_seq); 4519 goto done; 4520 } 4521 4522 walk = set_mm_walk(NULL, true); 4523 if (!walk) { 4524 success = iterate_mm_list_nowalk(lruvec, max_seq); 4525 goto done; 4526 } 4527 4528 walk->lruvec = lruvec; 4529 walk->max_seq = max_seq; 4530 walk->can_swap = can_swap; 4531 walk->force_scan = force_scan; 4532 4533 do { 4534 success = iterate_mm_list(lruvec, walk, &mm); 4535 if (mm) 4536 walk_mm(lruvec, mm, walk); 4537 } while (mm); 4538 done: 4539 if (success) 4540 inc_max_seq(lruvec, can_swap, force_scan); 4541 4542 return success; 4543 } 4544 4545 /****************************************************************************** 4546 * working set protection 4547 ******************************************************************************/ 4548 4549 static bool lruvec_is_sizable(struct lruvec *lruvec, struct scan_control *sc) 4550 { 4551 int gen, type, zone; 4552 unsigned long total = 0; 4553 bool can_swap = get_swappiness(lruvec, sc); 4554 struct lru_gen_folio *lrugen = &lruvec->lrugen; 4555 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 4556 DEFINE_MAX_SEQ(lruvec); 4557 DEFINE_MIN_SEQ(lruvec); 4558 4559 for (type = !can_swap; type < ANON_AND_FILE; type++) { 4560 unsigned long seq; 4561 4562 for (seq = min_seq[type]; seq <= max_seq; seq++) { 4563 gen = lru_gen_from_seq(seq); 4564 4565 for (zone = 0; zone < MAX_NR_ZONES; zone++) 4566 total += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); 4567 } 4568 } 4569 4570 /* whether the size is big enough to be helpful */ 4571 return mem_cgroup_online(memcg) ? (total >> sc->priority) : total; 4572 } 4573 4574 static bool lruvec_is_reclaimable(struct lruvec *lruvec, struct scan_control *sc, 4575 unsigned long min_ttl) 4576 { 4577 int gen; 4578 unsigned long birth; 4579 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 4580 DEFINE_MIN_SEQ(lruvec); 4581 4582 /* see the comment on lru_gen_folio */ 4583 gen = lru_gen_from_seq(min_seq[LRU_GEN_FILE]); 4584 birth = READ_ONCE(lruvec->lrugen.timestamps[gen]); 4585 4586 if (time_is_after_jiffies(birth + min_ttl)) 4587 return false; 4588 4589 if (!lruvec_is_sizable(lruvec, sc)) 4590 return false; 4591 4592 mem_cgroup_calculate_protection(NULL, memcg); 4593 4594 return !mem_cgroup_below_min(NULL, memcg); 4595 } 4596 4597 /* to protect the working set of the last N jiffies */ 4598 static unsigned long lru_gen_min_ttl __read_mostly; 4599 4600 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) 4601 { 4602 struct mem_cgroup *memcg; 4603 unsigned long min_ttl = READ_ONCE(lru_gen_min_ttl); 4604 4605 VM_WARN_ON_ONCE(!current_is_kswapd()); 4606 4607 /* check the order to exclude compaction-induced reclaim */ 4608 if (!min_ttl || sc->order || sc->priority == DEF_PRIORITY) 4609 return; 4610 4611 memcg = mem_cgroup_iter(NULL, NULL, NULL); 4612 do { 4613 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); 4614 4615 if (lruvec_is_reclaimable(lruvec, sc, min_ttl)) { 4616 mem_cgroup_iter_break(NULL, memcg); 4617 return; 4618 } 4619 4620 cond_resched(); 4621 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); 4622 4623 /* 4624 * The main goal is to OOM kill if every generation from all memcgs is 4625 * younger than min_ttl. However, another possibility is all memcgs are 4626 * either too small or below min. 4627 */ 4628 if (mutex_trylock(&oom_lock)) { 4629 struct oom_control oc = { 4630 .gfp_mask = sc->gfp_mask, 4631 }; 4632 4633 out_of_memory(&oc); 4634 4635 mutex_unlock(&oom_lock); 4636 } 4637 } 4638 4639 /****************************************************************************** 4640 * rmap/PT walk feedback 4641 ******************************************************************************/ 4642 4643 /* 4644 * This function exploits spatial locality when shrink_folio_list() walks the 4645 * rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages. If 4646 * the scan was done cacheline efficiently, it adds the PMD entry pointing to 4647 * the PTE table to the Bloom filter. This forms a feedback loop between the 4648 * eviction and the aging. 4649 */ 4650 void lru_gen_look_around(struct page_vma_mapped_walk *pvmw) 4651 { 4652 int i; 4653 unsigned long start; 4654 unsigned long end; 4655 struct lru_gen_mm_walk *walk; 4656 int young = 0; 4657 pte_t *pte = pvmw->pte; 4658 unsigned long addr = pvmw->address; 4659 struct folio *folio = pfn_folio(pvmw->pfn); 4660 bool can_swap = !folio_is_file_lru(folio); 4661 struct mem_cgroup *memcg = folio_memcg(folio); 4662 struct pglist_data *pgdat = folio_pgdat(folio); 4663 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); 4664 DEFINE_MAX_SEQ(lruvec); 4665 int old_gen, new_gen = lru_gen_from_seq(max_seq); 4666 4667 lockdep_assert_held(pvmw->ptl); 4668 VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio); 4669 4670 if (spin_is_contended(pvmw->ptl)) 4671 return; 4672 4673 /* avoid taking the LRU lock under the PTL when possible */ 4674 walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL; 4675 4676 start = max(addr & PMD_MASK, pvmw->vma->vm_start); 4677 end = min(addr | ~PMD_MASK, pvmw->vma->vm_end - 1) + 1; 4678 4679 if (end - start > MIN_LRU_BATCH * PAGE_SIZE) { 4680 if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2) 4681 end = start + MIN_LRU_BATCH * PAGE_SIZE; 4682 else if (end - addr < MIN_LRU_BATCH * PAGE_SIZE / 2) 4683 start = end - MIN_LRU_BATCH * PAGE_SIZE; 4684 else { 4685 start = addr - MIN_LRU_BATCH * PAGE_SIZE / 2; 4686 end = addr + MIN_LRU_BATCH * PAGE_SIZE / 2; 4687 } 4688 } 4689 4690 /* folio_update_gen() requires stable folio_memcg() */ 4691 if (!mem_cgroup_trylock_pages(memcg)) 4692 return; 4693 4694 arch_enter_lazy_mmu_mode(); 4695 4696 pte -= (addr - start) / PAGE_SIZE; 4697 4698 for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) { 4699 unsigned long pfn; 4700 pte_t ptent = ptep_get(pte + i); 4701 4702 pfn = get_pte_pfn(ptent, pvmw->vma, addr); 4703 if (pfn == -1) 4704 continue; 4705 4706 if (!pte_young(ptent)) 4707 continue; 4708 4709 folio = get_pfn_folio(pfn, memcg, pgdat, can_swap); 4710 if (!folio) 4711 continue; 4712 4713 if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i)) 4714 VM_WARN_ON_ONCE(true); 4715 4716 young++; 4717 4718 if (pte_dirty(ptent) && !folio_test_dirty(folio) && 4719 !(folio_test_anon(folio) && folio_test_swapbacked(folio) && 4720 !folio_test_swapcache(folio))) 4721 folio_mark_dirty(folio); 4722 4723 if (walk) { 4724 old_gen = folio_update_gen(folio, new_gen); 4725 if (old_gen >= 0 && old_gen != new_gen) 4726 update_batch_size(walk, folio, old_gen, new_gen); 4727 4728 continue; 4729 } 4730 4731 old_gen = folio_lru_gen(folio); 4732 if (old_gen < 0) 4733 folio_set_referenced(folio); 4734 else if (old_gen != new_gen) 4735 folio_activate(folio); 4736 } 4737 4738 arch_leave_lazy_mmu_mode(); 4739 mem_cgroup_unlock_pages(); 4740 4741 /* feedback from rmap walkers to page table walkers */ 4742 if (suitable_to_scan(i, young)) 4743 update_bloom_filter(lruvec, max_seq, pvmw->pmd); 4744 } 4745 4746 /****************************************************************************** 4747 * memcg LRU 4748 ******************************************************************************/ 4749 4750 /* see the comment on MEMCG_NR_GENS */ 4751 enum { 4752 MEMCG_LRU_NOP, 4753 MEMCG_LRU_HEAD, 4754 MEMCG_LRU_TAIL, 4755 MEMCG_LRU_OLD, 4756 MEMCG_LRU_YOUNG, 4757 }; 4758 4759 #ifdef CONFIG_MEMCG 4760 4761 static int lru_gen_memcg_seg(struct lruvec *lruvec) 4762 { 4763 return READ_ONCE(lruvec->lrugen.seg); 4764 } 4765 4766 static void lru_gen_rotate_memcg(struct lruvec *lruvec, int op) 4767 { 4768 int seg; 4769 int old, new; 4770 unsigned long flags; 4771 int bin = get_random_u32_below(MEMCG_NR_BINS); 4772 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 4773 4774 spin_lock_irqsave(&pgdat->memcg_lru.lock, flags); 4775 4776 VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list)); 4777 4778 seg = 0; 4779 new = old = lruvec->lrugen.gen; 4780 4781 /* see the comment on MEMCG_NR_GENS */ 4782 if (op == MEMCG_LRU_HEAD) 4783 seg = MEMCG_LRU_HEAD; 4784 else if (op == MEMCG_LRU_TAIL) 4785 seg = MEMCG_LRU_TAIL; 4786 else if (op == MEMCG_LRU_OLD) 4787 new = get_memcg_gen(pgdat->memcg_lru.seq); 4788 else if (op == MEMCG_LRU_YOUNG) 4789 new = get_memcg_gen(pgdat->memcg_lru.seq + 1); 4790 else 4791 VM_WARN_ON_ONCE(true); 4792 4793 hlist_nulls_del_rcu(&lruvec->lrugen.list); 4794 4795 if (op == MEMCG_LRU_HEAD || op == MEMCG_LRU_OLD) 4796 hlist_nulls_add_head_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]); 4797 else 4798 hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[new][bin]); 4799 4800 pgdat->memcg_lru.nr_memcgs[old]--; 4801 pgdat->memcg_lru.nr_memcgs[new]++; 4802 4803 lruvec->lrugen.gen = new; 4804 WRITE_ONCE(lruvec->lrugen.seg, seg); 4805 4806 if (!pgdat->memcg_lru.nr_memcgs[old] && old == get_memcg_gen(pgdat->memcg_lru.seq)) 4807 WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1); 4808 4809 spin_unlock_irqrestore(&pgdat->memcg_lru.lock, flags); 4810 } 4811 4812 void lru_gen_online_memcg(struct mem_cgroup *memcg) 4813 { 4814 int gen; 4815 int nid; 4816 int bin = get_random_u32_below(MEMCG_NR_BINS); 4817 4818 for_each_node(nid) { 4819 struct pglist_data *pgdat = NODE_DATA(nid); 4820 struct lruvec *lruvec = get_lruvec(memcg, nid); 4821 4822 spin_lock_irq(&pgdat->memcg_lru.lock); 4823 4824 VM_WARN_ON_ONCE(!hlist_nulls_unhashed(&lruvec->lrugen.list)); 4825 4826 gen = get_memcg_gen(pgdat->memcg_lru.seq); 4827 4828 hlist_nulls_add_tail_rcu(&lruvec->lrugen.list, &pgdat->memcg_lru.fifo[gen][bin]); 4829 pgdat->memcg_lru.nr_memcgs[gen]++; 4830 4831 lruvec->lrugen.gen = gen; 4832 4833 spin_unlock_irq(&pgdat->memcg_lru.lock); 4834 } 4835 } 4836 4837 void lru_gen_offline_memcg(struct mem_cgroup *memcg) 4838 { 4839 int nid; 4840 4841 for_each_node(nid) { 4842 struct lruvec *lruvec = get_lruvec(memcg, nid); 4843 4844 lru_gen_rotate_memcg(lruvec, MEMCG_LRU_OLD); 4845 } 4846 } 4847 4848 void lru_gen_release_memcg(struct mem_cgroup *memcg) 4849 { 4850 int gen; 4851 int nid; 4852 4853 for_each_node(nid) { 4854 struct pglist_data *pgdat = NODE_DATA(nid); 4855 struct lruvec *lruvec = get_lruvec(memcg, nid); 4856 4857 spin_lock_irq(&pgdat->memcg_lru.lock); 4858 4859 if (hlist_nulls_unhashed(&lruvec->lrugen.list)) 4860 goto unlock; 4861 4862 gen = lruvec->lrugen.gen; 4863 4864 hlist_nulls_del_init_rcu(&lruvec->lrugen.list); 4865 pgdat->memcg_lru.nr_memcgs[gen]--; 4866 4867 if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq)) 4868 WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1); 4869 unlock: 4870 spin_unlock_irq(&pgdat->memcg_lru.lock); 4871 } 4872 } 4873 4874 void lru_gen_soft_reclaim(struct mem_cgroup *memcg, int nid) 4875 { 4876 struct lruvec *lruvec = get_lruvec(memcg, nid); 4877 4878 /* see the comment on MEMCG_NR_GENS */ 4879 if (lru_gen_memcg_seg(lruvec) != MEMCG_LRU_HEAD) 4880 lru_gen_rotate_memcg(lruvec, MEMCG_LRU_HEAD); 4881 } 4882 4883 #else /* !CONFIG_MEMCG */ 4884 4885 static int lru_gen_memcg_seg(struct lruvec *lruvec) 4886 { 4887 return 0; 4888 } 4889 4890 #endif 4891 4892 /****************************************************************************** 4893 * the eviction 4894 ******************************************************************************/ 4895 4896 static bool sort_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc, 4897 int tier_idx) 4898 { 4899 bool success; 4900 int gen = folio_lru_gen(folio); 4901 int type = folio_is_file_lru(folio); 4902 int zone = folio_zonenum(folio); 4903 int delta = folio_nr_pages(folio); 4904 int refs = folio_lru_refs(folio); 4905 int tier = lru_tier_from_refs(refs); 4906 struct lru_gen_folio *lrugen = &lruvec->lrugen; 4907 4908 VM_WARN_ON_ONCE_FOLIO(gen >= MAX_NR_GENS, folio); 4909 4910 /* unevictable */ 4911 if (!folio_evictable(folio)) { 4912 success = lru_gen_del_folio(lruvec, folio, true); 4913 VM_WARN_ON_ONCE_FOLIO(!success, folio); 4914 folio_set_unevictable(folio); 4915 lruvec_add_folio(lruvec, folio); 4916 __count_vm_events(UNEVICTABLE_PGCULLED, delta); 4917 return true; 4918 } 4919 4920 /* dirty lazyfree */ 4921 if (type == LRU_GEN_FILE && folio_test_anon(folio) && folio_test_dirty(folio)) { 4922 success = lru_gen_del_folio(lruvec, folio, true); 4923 VM_WARN_ON_ONCE_FOLIO(!success, folio); 4924 folio_set_swapbacked(folio); 4925 lruvec_add_folio_tail(lruvec, folio); 4926 return true; 4927 } 4928 4929 /* promoted */ 4930 if (gen != lru_gen_from_seq(lrugen->min_seq[type])) { 4931 list_move(&folio->lru, &lrugen->folios[gen][type][zone]); 4932 return true; 4933 } 4934 4935 /* protected */ 4936 if (tier > tier_idx) { 4937 int hist = lru_hist_from_seq(lrugen->min_seq[type]); 4938 4939 gen = folio_inc_gen(lruvec, folio, false); 4940 list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]); 4941 4942 WRITE_ONCE(lrugen->protected[hist][type][tier - 1], 4943 lrugen->protected[hist][type][tier - 1] + delta); 4944 return true; 4945 } 4946 4947 /* ineligible */ 4948 if (zone > sc->reclaim_idx || skip_cma(folio, sc)) { 4949 gen = folio_inc_gen(lruvec, folio, false); 4950 list_move_tail(&folio->lru, &lrugen->folios[gen][type][zone]); 4951 return true; 4952 } 4953 4954 /* waiting for writeback */ 4955 if (folio_test_locked(folio) || folio_test_writeback(folio) || 4956 (type == LRU_GEN_FILE && folio_test_dirty(folio))) { 4957 gen = folio_inc_gen(lruvec, folio, true); 4958 list_move(&folio->lru, &lrugen->folios[gen][type][zone]); 4959 return true; 4960 } 4961 4962 return false; 4963 } 4964 4965 static bool isolate_folio(struct lruvec *lruvec, struct folio *folio, struct scan_control *sc) 4966 { 4967 bool success; 4968 4969 /* swapping inhibited */ 4970 if (!(sc->gfp_mask & __GFP_IO) && 4971 (folio_test_dirty(folio) || 4972 (folio_test_anon(folio) && !folio_test_swapcache(folio)))) 4973 return false; 4974 4975 /* raced with release_pages() */ 4976 if (!folio_try_get(folio)) 4977 return false; 4978 4979 /* raced with another isolation */ 4980 if (!folio_test_clear_lru(folio)) { 4981 folio_put(folio); 4982 return false; 4983 } 4984 4985 /* see the comment on MAX_NR_TIERS */ 4986 if (!folio_test_referenced(folio)) 4987 set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 0); 4988 4989 /* for shrink_folio_list() */ 4990 folio_clear_reclaim(folio); 4991 folio_clear_referenced(folio); 4992 4993 success = lru_gen_del_folio(lruvec, folio, true); 4994 VM_WARN_ON_ONCE_FOLIO(!success, folio); 4995 4996 return true; 4997 } 4998 4999 static int scan_folios(struct lruvec *lruvec, struct scan_control *sc, 5000 int type, int tier, struct list_head *list) 5001 { 5002 int i; 5003 int gen; 5004 enum vm_event_item item; 5005 int sorted = 0; 5006 int scanned = 0; 5007 int isolated = 0; 5008 int remaining = MAX_LRU_BATCH; 5009 struct lru_gen_folio *lrugen = &lruvec->lrugen; 5010 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 5011 5012 VM_WARN_ON_ONCE(!list_empty(list)); 5013 5014 if (get_nr_gens(lruvec, type) == MIN_NR_GENS) 5015 return 0; 5016 5017 gen = lru_gen_from_seq(lrugen->min_seq[type]); 5018 5019 for (i = MAX_NR_ZONES; i > 0; i--) { 5020 LIST_HEAD(moved); 5021 int skipped = 0; 5022 int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES; 5023 struct list_head *head = &lrugen->folios[gen][type][zone]; 5024 5025 while (!list_empty(head)) { 5026 struct folio *folio = lru_to_folio(head); 5027 int delta = folio_nr_pages(folio); 5028 5029 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); 5030 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); 5031 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); 5032 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); 5033 5034 scanned += delta; 5035 5036 if (sort_folio(lruvec, folio, sc, tier)) 5037 sorted += delta; 5038 else if (isolate_folio(lruvec, folio, sc)) { 5039 list_add(&folio->lru, list); 5040 isolated += delta; 5041 } else { 5042 list_move(&folio->lru, &moved); 5043 skipped += delta; 5044 } 5045 5046 if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH) 5047 break; 5048 } 5049 5050 if (skipped) { 5051 list_splice(&moved, head); 5052 __count_zid_vm_events(PGSCAN_SKIP, zone, skipped); 5053 } 5054 5055 if (!remaining || isolated >= MIN_LRU_BATCH) 5056 break; 5057 } 5058 5059 item = PGSCAN_KSWAPD + reclaimer_offset(); 5060 if (!cgroup_reclaim(sc)) { 5061 __count_vm_events(item, isolated); 5062 __count_vm_events(PGREFILL, sorted); 5063 } 5064 __count_memcg_events(memcg, item, isolated); 5065 __count_memcg_events(memcg, PGREFILL, sorted); 5066 __count_vm_events(PGSCAN_ANON + type, isolated); 5067 5068 /* 5069 * There might not be eligible folios due to reclaim_idx. Check the 5070 * remaining to prevent livelock if it's not making progress. 5071 */ 5072 return isolated || !remaining ? scanned : 0; 5073 } 5074 5075 static int get_tier_idx(struct lruvec *lruvec, int type) 5076 { 5077 int tier; 5078 struct ctrl_pos sp, pv; 5079 5080 /* 5081 * To leave a margin for fluctuations, use a larger gain factor (1:2). 5082 * This value is chosen because any other tier would have at least twice 5083 * as many refaults as the first tier. 5084 */ 5085 read_ctrl_pos(lruvec, type, 0, 1, &sp); 5086 for (tier = 1; tier < MAX_NR_TIERS; tier++) { 5087 read_ctrl_pos(lruvec, type, tier, 2, &pv); 5088 if (!positive_ctrl_err(&sp, &pv)) 5089 break; 5090 } 5091 5092 return tier - 1; 5093 } 5094 5095 static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx) 5096 { 5097 int type, tier; 5098 struct ctrl_pos sp, pv; 5099 int gain[ANON_AND_FILE] = { swappiness, 200 - swappiness }; 5100 5101 /* 5102 * Compare the first tier of anon with that of file to determine which 5103 * type to scan. Also need to compare other tiers of the selected type 5104 * with the first tier of the other type to determine the last tier (of 5105 * the selected type) to evict. 5106 */ 5107 read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp); 5108 read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv); 5109 type = positive_ctrl_err(&sp, &pv); 5110 5111 read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp); 5112 for (tier = 1; tier < MAX_NR_TIERS; tier++) { 5113 read_ctrl_pos(lruvec, type, tier, gain[type], &pv); 5114 if (!positive_ctrl_err(&sp, &pv)) 5115 break; 5116 } 5117 5118 *tier_idx = tier - 1; 5119 5120 return type; 5121 } 5122 5123 static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness, 5124 int *type_scanned, struct list_head *list) 5125 { 5126 int i; 5127 int type; 5128 int scanned; 5129 int tier = -1; 5130 DEFINE_MIN_SEQ(lruvec); 5131 5132 /* 5133 * Try to make the obvious choice first. When anon and file are both 5134 * available from the same generation, interpret swappiness 1 as file 5135 * first and 200 as anon first. 5136 */ 5137 if (!swappiness) 5138 type = LRU_GEN_FILE; 5139 else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE]) 5140 type = LRU_GEN_ANON; 5141 else if (swappiness == 1) 5142 type = LRU_GEN_FILE; 5143 else if (swappiness == 200) 5144 type = LRU_GEN_ANON; 5145 else 5146 type = get_type_to_scan(lruvec, swappiness, &tier); 5147 5148 for (i = !swappiness; i < ANON_AND_FILE; i++) { 5149 if (tier < 0) 5150 tier = get_tier_idx(lruvec, type); 5151 5152 scanned = scan_folios(lruvec, sc, type, tier, list); 5153 if (scanned) 5154 break; 5155 5156 type = !type; 5157 tier = -1; 5158 } 5159 5160 *type_scanned = type; 5161 5162 return scanned; 5163 } 5164 5165 static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness) 5166 { 5167 int type; 5168 int scanned; 5169 int reclaimed; 5170 LIST_HEAD(list); 5171 LIST_HEAD(clean); 5172 struct folio *folio; 5173 struct folio *next; 5174 enum vm_event_item item; 5175 struct reclaim_stat stat; 5176 struct lru_gen_mm_walk *walk; 5177 bool skip_retry = false; 5178 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 5179 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 5180 5181 spin_lock_irq(&lruvec->lru_lock); 5182 5183 scanned = isolate_folios(lruvec, sc, swappiness, &type, &list); 5184 5185 scanned += try_to_inc_min_seq(lruvec, swappiness); 5186 5187 if (get_nr_gens(lruvec, !swappiness) == MIN_NR_GENS) 5188 scanned = 0; 5189 5190 spin_unlock_irq(&lruvec->lru_lock); 5191 5192 if (list_empty(&list)) 5193 return scanned; 5194 retry: 5195 reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false); 5196 sc->nr_reclaimed += reclaimed; 5197 5198 list_for_each_entry_safe_reverse(folio, next, &list, lru) { 5199 if (!folio_evictable(folio)) { 5200 list_del(&folio->lru); 5201 folio_putback_lru(folio); 5202 continue; 5203 } 5204 5205 if (folio_test_reclaim(folio) && 5206 (folio_test_dirty(folio) || folio_test_writeback(folio))) { 5207 /* restore LRU_REFS_FLAGS cleared by isolate_folio() */ 5208 if (folio_test_workingset(folio)) 5209 folio_set_referenced(folio); 5210 continue; 5211 } 5212 5213 if (skip_retry || folio_test_active(folio) || folio_test_referenced(folio) || 5214 folio_mapped(folio) || folio_test_locked(folio) || 5215 folio_test_dirty(folio) || folio_test_writeback(folio)) { 5216 /* don't add rejected folios to the oldest generation */ 5217 set_mask_bits(&folio->flags, LRU_REFS_MASK | LRU_REFS_FLAGS, 5218 BIT(PG_active)); 5219 continue; 5220 } 5221 5222 /* retry folios that may have missed folio_rotate_reclaimable() */ 5223 list_move(&folio->lru, &clean); 5224 sc->nr_scanned -= folio_nr_pages(folio); 5225 } 5226 5227 spin_lock_irq(&lruvec->lru_lock); 5228 5229 move_folios_to_lru(lruvec, &list); 5230 5231 walk = current->reclaim_state->mm_walk; 5232 if (walk && walk->batched) 5233 reset_batch_size(lruvec, walk); 5234 5235 item = PGSTEAL_KSWAPD + reclaimer_offset(); 5236 if (!cgroup_reclaim(sc)) 5237 __count_vm_events(item, reclaimed); 5238 __count_memcg_events(memcg, item, reclaimed); 5239 __count_vm_events(PGSTEAL_ANON + type, reclaimed); 5240 5241 spin_unlock_irq(&lruvec->lru_lock); 5242 5243 mem_cgroup_uncharge_list(&list); 5244 free_unref_page_list(&list); 5245 5246 INIT_LIST_HEAD(&list); 5247 list_splice_init(&clean, &list); 5248 5249 if (!list_empty(&list)) { 5250 skip_retry = true; 5251 goto retry; 5252 } 5253 5254 return scanned; 5255 } 5256 5257 static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq, 5258 struct scan_control *sc, bool can_swap, unsigned long *nr_to_scan) 5259 { 5260 int gen, type, zone; 5261 unsigned long old = 0; 5262 unsigned long young = 0; 5263 unsigned long total = 0; 5264 struct lru_gen_folio *lrugen = &lruvec->lrugen; 5265 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 5266 DEFINE_MIN_SEQ(lruvec); 5267 5268 /* whether this lruvec is completely out of cold folios */ 5269 if (min_seq[!can_swap] + MIN_NR_GENS > max_seq) { 5270 *nr_to_scan = 0; 5271 return true; 5272 } 5273 5274 for (type = !can_swap; type < ANON_AND_FILE; type++) { 5275 unsigned long seq; 5276 5277 for (seq = min_seq[type]; seq <= max_seq; seq++) { 5278 unsigned long size = 0; 5279 5280 gen = lru_gen_from_seq(seq); 5281 5282 for (zone = 0; zone < MAX_NR_ZONES; zone++) 5283 size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); 5284 5285 total += size; 5286 if (seq == max_seq) 5287 young += size; 5288 else if (seq + MIN_NR_GENS == max_seq) 5289 old += size; 5290 } 5291 } 5292 5293 /* try to scrape all its memory if this memcg was deleted */ 5294 *nr_to_scan = mem_cgroup_online(memcg) ? (total >> sc->priority) : total; 5295 5296 /* 5297 * The aging tries to be lazy to reduce the overhead, while the eviction 5298 * stalls when the number of generations reaches MIN_NR_GENS. Hence, the 5299 * ideal number of generations is MIN_NR_GENS+1. 5300 */ 5301 if (min_seq[!can_swap] + MIN_NR_GENS < max_seq) 5302 return false; 5303 5304 /* 5305 * It's also ideal to spread pages out evenly, i.e., 1/(MIN_NR_GENS+1) 5306 * of the total number of pages for each generation. A reasonable range 5307 * for this average portion is [1/MIN_NR_GENS, 1/(MIN_NR_GENS+2)]. The 5308 * aging cares about the upper bound of hot pages, while the eviction 5309 * cares about the lower bound of cold pages. 5310 */ 5311 if (young * MIN_NR_GENS > total) 5312 return true; 5313 if (old * (MIN_NR_GENS + 2) < total) 5314 return true; 5315 5316 return false; 5317 } 5318 5319 /* 5320 * For future optimizations: 5321 * 1. Defer try_to_inc_max_seq() to workqueues to reduce latency for memcg 5322 * reclaim. 5323 */ 5324 static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool can_swap) 5325 { 5326 unsigned long nr_to_scan; 5327 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 5328 DEFINE_MAX_SEQ(lruvec); 5329 5330 if (mem_cgroup_below_min(sc->target_mem_cgroup, memcg)) 5331 return 0; 5332 5333 if (!should_run_aging(lruvec, max_seq, sc, can_swap, &nr_to_scan)) 5334 return nr_to_scan; 5335 5336 /* skip the aging path at the default priority */ 5337 if (sc->priority == DEF_PRIORITY) 5338 return nr_to_scan; 5339 5340 /* skip this lruvec as it's low on cold folios */ 5341 return try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false) ? -1 : 0; 5342 } 5343 5344 static unsigned long get_nr_to_reclaim(struct scan_control *sc) 5345 { 5346 /* don't abort memcg reclaim to ensure fairness */ 5347 if (!root_reclaim(sc)) 5348 return -1; 5349 5350 return max(sc->nr_to_reclaim, compact_gap(sc->order)); 5351 } 5352 5353 static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) 5354 { 5355 long nr_to_scan; 5356 unsigned long scanned = 0; 5357 unsigned long nr_to_reclaim = get_nr_to_reclaim(sc); 5358 int swappiness = get_swappiness(lruvec, sc); 5359 5360 /* clean file folios are more likely to exist */ 5361 if (swappiness && !(sc->gfp_mask & __GFP_IO)) 5362 swappiness = 1; 5363 5364 while (true) { 5365 int delta; 5366 5367 nr_to_scan = get_nr_to_scan(lruvec, sc, swappiness); 5368 if (nr_to_scan <= 0) 5369 break; 5370 5371 delta = evict_folios(lruvec, sc, swappiness); 5372 if (!delta) 5373 break; 5374 5375 scanned += delta; 5376 if (scanned >= nr_to_scan) 5377 break; 5378 5379 if (sc->nr_reclaimed >= nr_to_reclaim) 5380 break; 5381 5382 cond_resched(); 5383 } 5384 5385 /* whether try_to_inc_max_seq() was successful */ 5386 return nr_to_scan < 0; 5387 } 5388 5389 static int shrink_one(struct lruvec *lruvec, struct scan_control *sc) 5390 { 5391 bool success; 5392 unsigned long scanned = sc->nr_scanned; 5393 unsigned long reclaimed = sc->nr_reclaimed; 5394 int seg = lru_gen_memcg_seg(lruvec); 5395 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 5396 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 5397 5398 /* see the comment on MEMCG_NR_GENS */ 5399 if (!lruvec_is_sizable(lruvec, sc)) 5400 return seg != MEMCG_LRU_TAIL ? MEMCG_LRU_TAIL : MEMCG_LRU_YOUNG; 5401 5402 mem_cgroup_calculate_protection(NULL, memcg); 5403 5404 if (mem_cgroup_below_min(NULL, memcg)) 5405 return MEMCG_LRU_YOUNG; 5406 5407 if (mem_cgroup_below_low(NULL, memcg)) { 5408 /* see the comment on MEMCG_NR_GENS */ 5409 if (seg != MEMCG_LRU_TAIL) 5410 return MEMCG_LRU_TAIL; 5411 5412 memcg_memory_event(memcg, MEMCG_LOW); 5413 } 5414 5415 success = try_to_shrink_lruvec(lruvec, sc); 5416 5417 shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, sc->priority); 5418 5419 if (!sc->proactive) 5420 vmpressure(sc->gfp_mask, memcg, false, sc->nr_scanned - scanned, 5421 sc->nr_reclaimed - reclaimed); 5422 5423 flush_reclaim_state(sc); 5424 5425 return success ? MEMCG_LRU_YOUNG : 0; 5426 } 5427 5428 #ifdef CONFIG_MEMCG 5429 5430 static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) 5431 { 5432 int op; 5433 int gen; 5434 int bin; 5435 int first_bin; 5436 struct lruvec *lruvec; 5437 struct lru_gen_folio *lrugen; 5438 struct mem_cgroup *memcg; 5439 const struct hlist_nulls_node *pos; 5440 unsigned long nr_to_reclaim = get_nr_to_reclaim(sc); 5441 5442 bin = first_bin = get_random_u32_below(MEMCG_NR_BINS); 5443 restart: 5444 op = 0; 5445 memcg = NULL; 5446 gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq)); 5447 5448 rcu_read_lock(); 5449 5450 hlist_nulls_for_each_entry_rcu(lrugen, pos, &pgdat->memcg_lru.fifo[gen][bin], list) { 5451 if (op) { 5452 lru_gen_rotate_memcg(lruvec, op); 5453 op = 0; 5454 } 5455 5456 mem_cgroup_put(memcg); 5457 5458 lruvec = container_of(lrugen, struct lruvec, lrugen); 5459 memcg = lruvec_memcg(lruvec); 5460 5461 if (!mem_cgroup_tryget(memcg)) { 5462 lru_gen_release_memcg(memcg); 5463 memcg = NULL; 5464 continue; 5465 } 5466 5467 rcu_read_unlock(); 5468 5469 op = shrink_one(lruvec, sc); 5470 5471 rcu_read_lock(); 5472 5473 if (sc->nr_reclaimed >= nr_to_reclaim) 5474 break; 5475 } 5476 5477 rcu_read_unlock(); 5478 5479 if (op) 5480 lru_gen_rotate_memcg(lruvec, op); 5481 5482 mem_cgroup_put(memcg); 5483 5484 if (sc->nr_reclaimed >= nr_to_reclaim) 5485 return; 5486 5487 /* restart if raced with lru_gen_rotate_memcg() */ 5488 if (gen != get_nulls_value(pos)) 5489 goto restart; 5490 5491 /* try the rest of the bins of the current generation */ 5492 bin = get_memcg_bin(bin + 1); 5493 if (bin != first_bin) 5494 goto restart; 5495 } 5496 5497 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) 5498 { 5499 struct blk_plug plug; 5500 5501 VM_WARN_ON_ONCE(root_reclaim(sc)); 5502 VM_WARN_ON_ONCE(!sc->may_writepage || !sc->may_unmap); 5503 5504 lru_add_drain(); 5505 5506 blk_start_plug(&plug); 5507 5508 set_mm_walk(NULL, sc->proactive); 5509 5510 if (try_to_shrink_lruvec(lruvec, sc)) 5511 lru_gen_rotate_memcg(lruvec, MEMCG_LRU_YOUNG); 5512 5513 clear_mm_walk(); 5514 5515 blk_finish_plug(&plug); 5516 } 5517 5518 #else /* !CONFIG_MEMCG */ 5519 5520 static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) 5521 { 5522 BUILD_BUG(); 5523 } 5524 5525 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) 5526 { 5527 BUILD_BUG(); 5528 } 5529 5530 #endif 5531 5532 static void set_initial_priority(struct pglist_data *pgdat, struct scan_control *sc) 5533 { 5534 int priority; 5535 unsigned long reclaimable; 5536 struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat); 5537 5538 if (sc->priority != DEF_PRIORITY || sc->nr_to_reclaim < MIN_LRU_BATCH) 5539 return; 5540 /* 5541 * Determine the initial priority based on ((total / MEMCG_NR_GENS) >> 5542 * priority) * reclaimed_to_scanned_ratio = nr_to_reclaim, where the 5543 * estimated reclaimed_to_scanned_ratio = inactive / total. 5544 */ 5545 reclaimable = node_page_state(pgdat, NR_INACTIVE_FILE); 5546 if (get_swappiness(lruvec, sc)) 5547 reclaimable += node_page_state(pgdat, NR_INACTIVE_ANON); 5548 5549 reclaimable /= MEMCG_NR_GENS; 5550 5551 /* round down reclaimable and round up sc->nr_to_reclaim */ 5552 priority = fls_long(reclaimable) - 1 - fls_long(sc->nr_to_reclaim - 1); 5553 5554 sc->priority = clamp(priority, 0, DEF_PRIORITY); 5555 } 5556 5557 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc) 5558 { 5559 struct blk_plug plug; 5560 unsigned long reclaimed = sc->nr_reclaimed; 5561 5562 VM_WARN_ON_ONCE(!root_reclaim(sc)); 5563 5564 /* 5565 * Unmapped clean folios are already prioritized. Scanning for more of 5566 * them is likely futile and can cause high reclaim latency when there 5567 * is a large number of memcgs. 5568 */ 5569 if (!sc->may_writepage || !sc->may_unmap) 5570 goto done; 5571 5572 lru_add_drain(); 5573 5574 blk_start_plug(&plug); 5575 5576 set_mm_walk(pgdat, sc->proactive); 5577 5578 set_initial_priority(pgdat, sc); 5579 5580 if (current_is_kswapd()) 5581 sc->nr_reclaimed = 0; 5582 5583 if (mem_cgroup_disabled()) 5584 shrink_one(&pgdat->__lruvec, sc); 5585 else 5586 shrink_many(pgdat, sc); 5587 5588 if (current_is_kswapd()) 5589 sc->nr_reclaimed += reclaimed; 5590 5591 clear_mm_walk(); 5592 5593 blk_finish_plug(&plug); 5594 done: 5595 /* kswapd should never fail */ 5596 pgdat->kswapd_failures = 0; 5597 } 5598 5599 /****************************************************************************** 5600 * state change 5601 ******************************************************************************/ 5602 5603 static bool __maybe_unused state_is_valid(struct lruvec *lruvec) 5604 { 5605 struct lru_gen_folio *lrugen = &lruvec->lrugen; 5606 5607 if (lrugen->enabled) { 5608 enum lru_list lru; 5609 5610 for_each_evictable_lru(lru) { 5611 if (!list_empty(&lruvec->lists[lru])) 5612 return false; 5613 } 5614 } else { 5615 int gen, type, zone; 5616 5617 for_each_gen_type_zone(gen, type, zone) { 5618 if (!list_empty(&lrugen->folios[gen][type][zone])) 5619 return false; 5620 } 5621 } 5622 5623 return true; 5624 } 5625 5626 static bool fill_evictable(struct lruvec *lruvec) 5627 { 5628 enum lru_list lru; 5629 int remaining = MAX_LRU_BATCH; 5630 5631 for_each_evictable_lru(lru) { 5632 int type = is_file_lru(lru); 5633 bool active = is_active_lru(lru); 5634 struct list_head *head = &lruvec->lists[lru]; 5635 5636 while (!list_empty(head)) { 5637 bool success; 5638 struct folio *folio = lru_to_folio(head); 5639 5640 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); 5641 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio) != active, folio); 5642 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); 5643 VM_WARN_ON_ONCE_FOLIO(folio_lru_gen(folio) != -1, folio); 5644 5645 lruvec_del_folio(lruvec, folio); 5646 success = lru_gen_add_folio(lruvec, folio, false); 5647 VM_WARN_ON_ONCE(!success); 5648 5649 if (!--remaining) 5650 return false; 5651 } 5652 } 5653 5654 return true; 5655 } 5656 5657 static bool drain_evictable(struct lruvec *lruvec) 5658 { 5659 int gen, type, zone; 5660 int remaining = MAX_LRU_BATCH; 5661 5662 for_each_gen_type_zone(gen, type, zone) { 5663 struct list_head *head = &lruvec->lrugen.folios[gen][type][zone]; 5664 5665 while (!list_empty(head)) { 5666 bool success; 5667 struct folio *folio = lru_to_folio(head); 5668 5669 VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); 5670 VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); 5671 VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); 5672 VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); 5673 5674 success = lru_gen_del_folio(lruvec, folio, false); 5675 VM_WARN_ON_ONCE(!success); 5676 lruvec_add_folio(lruvec, folio); 5677 5678 if (!--remaining) 5679 return false; 5680 } 5681 } 5682 5683 return true; 5684 } 5685 5686 static void lru_gen_change_state(bool enabled) 5687 { 5688 static DEFINE_MUTEX(state_mutex); 5689 5690 struct mem_cgroup *memcg; 5691 5692 cgroup_lock(); 5693 cpus_read_lock(); 5694 get_online_mems(); 5695 mutex_lock(&state_mutex); 5696 5697 if (enabled == lru_gen_enabled()) 5698 goto unlock; 5699 5700 if (enabled) 5701 static_branch_enable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]); 5702 else 5703 static_branch_disable_cpuslocked(&lru_gen_caps[LRU_GEN_CORE]); 5704 5705 memcg = mem_cgroup_iter(NULL, NULL, NULL); 5706 do { 5707 int nid; 5708 5709 for_each_node(nid) { 5710 struct lruvec *lruvec = get_lruvec(memcg, nid); 5711 5712 spin_lock_irq(&lruvec->lru_lock); 5713 5714 VM_WARN_ON_ONCE(!seq_is_valid(lruvec)); 5715 VM_WARN_ON_ONCE(!state_is_valid(lruvec)); 5716 5717 lruvec->lrugen.enabled = enabled; 5718 5719 while (!(enabled ? fill_evictable(lruvec) : drain_evictable(lruvec))) { 5720 spin_unlock_irq(&lruvec->lru_lock); 5721 cond_resched(); 5722 spin_lock_irq(&lruvec->lru_lock); 5723 } 5724 5725 spin_unlock_irq(&lruvec->lru_lock); 5726 } 5727 5728 cond_resched(); 5729 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); 5730 unlock: 5731 mutex_unlock(&state_mutex); 5732 put_online_mems(); 5733 cpus_read_unlock(); 5734 cgroup_unlock(); 5735 } 5736 5737 /****************************************************************************** 5738 * sysfs interface 5739 ******************************************************************************/ 5740 5741 static ssize_t min_ttl_ms_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) 5742 { 5743 return sysfs_emit(buf, "%u\n", jiffies_to_msecs(READ_ONCE(lru_gen_min_ttl))); 5744 } 5745 5746 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */ 5747 static ssize_t min_ttl_ms_store(struct kobject *kobj, struct kobj_attribute *attr, 5748 const char *buf, size_t len) 5749 { 5750 unsigned int msecs; 5751 5752 if (kstrtouint(buf, 0, &msecs)) 5753 return -EINVAL; 5754 5755 WRITE_ONCE(lru_gen_min_ttl, msecs_to_jiffies(msecs)); 5756 5757 return len; 5758 } 5759 5760 static struct kobj_attribute lru_gen_min_ttl_attr = __ATTR_RW(min_ttl_ms); 5761 5762 static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) 5763 { 5764 unsigned int caps = 0; 5765 5766 if (get_cap(LRU_GEN_CORE)) 5767 caps |= BIT(LRU_GEN_CORE); 5768 5769 if (should_walk_mmu()) 5770 caps |= BIT(LRU_GEN_MM_WALK); 5771 5772 if (should_clear_pmd_young()) 5773 caps |= BIT(LRU_GEN_NONLEAF_YOUNG); 5774 5775 return sysfs_emit(buf, "0x%04x\n", caps); 5776 } 5777 5778 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */ 5779 static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, 5780 const char *buf, size_t len) 5781 { 5782 int i; 5783 unsigned int caps; 5784 5785 if (tolower(*buf) == 'n') 5786 caps = 0; 5787 else if (tolower(*buf) == 'y') 5788 caps = -1; 5789 else if (kstrtouint(buf, 0, &caps)) 5790 return -EINVAL; 5791 5792 for (i = 0; i < NR_LRU_GEN_CAPS; i++) { 5793 bool enabled = caps & BIT(i); 5794 5795 if (i == LRU_GEN_CORE) 5796 lru_gen_change_state(enabled); 5797 else if (enabled) 5798 static_branch_enable(&lru_gen_caps[i]); 5799 else 5800 static_branch_disable(&lru_gen_caps[i]); 5801 } 5802 5803 return len; 5804 } 5805 5806 static struct kobj_attribute lru_gen_enabled_attr = __ATTR_RW(enabled); 5807 5808 static struct attribute *lru_gen_attrs[] = { 5809 &lru_gen_min_ttl_attr.attr, 5810 &lru_gen_enabled_attr.attr, 5811 NULL 5812 }; 5813 5814 static const struct attribute_group lru_gen_attr_group = { 5815 .name = "lru_gen", 5816 .attrs = lru_gen_attrs, 5817 }; 5818 5819 /****************************************************************************** 5820 * debugfs interface 5821 ******************************************************************************/ 5822 5823 static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos) 5824 { 5825 struct mem_cgroup *memcg; 5826 loff_t nr_to_skip = *pos; 5827 5828 m->private = kvmalloc(PATH_MAX, GFP_KERNEL); 5829 if (!m->private) 5830 return ERR_PTR(-ENOMEM); 5831 5832 memcg = mem_cgroup_iter(NULL, NULL, NULL); 5833 do { 5834 int nid; 5835 5836 for_each_node_state(nid, N_MEMORY) { 5837 if (!nr_to_skip--) 5838 return get_lruvec(memcg, nid); 5839 } 5840 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); 5841 5842 return NULL; 5843 } 5844 5845 static void lru_gen_seq_stop(struct seq_file *m, void *v) 5846 { 5847 if (!IS_ERR_OR_NULL(v)) 5848 mem_cgroup_iter_break(NULL, lruvec_memcg(v)); 5849 5850 kvfree(m->private); 5851 m->private = NULL; 5852 } 5853 5854 static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos) 5855 { 5856 int nid = lruvec_pgdat(v)->node_id; 5857 struct mem_cgroup *memcg = lruvec_memcg(v); 5858 5859 ++*pos; 5860 5861 nid = next_memory_node(nid); 5862 if (nid == MAX_NUMNODES) { 5863 memcg = mem_cgroup_iter(NULL, memcg, NULL); 5864 if (!memcg) 5865 return NULL; 5866 5867 nid = first_memory_node; 5868 } 5869 5870 return get_lruvec(memcg, nid); 5871 } 5872 5873 static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, 5874 unsigned long max_seq, unsigned long *min_seq, 5875 unsigned long seq) 5876 { 5877 int i; 5878 int type, tier; 5879 int hist = lru_hist_from_seq(seq); 5880 struct lru_gen_folio *lrugen = &lruvec->lrugen; 5881 5882 for (tier = 0; tier < MAX_NR_TIERS; tier++) { 5883 seq_printf(m, " %10d", tier); 5884 for (type = 0; type < ANON_AND_FILE; type++) { 5885 const char *s = " "; 5886 unsigned long n[3] = {}; 5887 5888 if (seq == max_seq) { 5889 s = "RT "; 5890 n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); 5891 n[1] = READ_ONCE(lrugen->avg_total[type][tier]); 5892 } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { 5893 s = "rep"; 5894 n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]); 5895 n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]); 5896 if (tier) 5897 n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]); 5898 } 5899 5900 for (i = 0; i < 3; i++) 5901 seq_printf(m, " %10lu%c", n[i], s[i]); 5902 } 5903 seq_putc(m, '\n'); 5904 } 5905 5906 seq_puts(m, " "); 5907 for (i = 0; i < NR_MM_STATS; i++) { 5908 const char *s = " "; 5909 unsigned long n = 0; 5910 5911 if (seq == max_seq && NR_HIST_GENS == 1) { 5912 s = "LOYNFA"; 5913 n = READ_ONCE(lruvec->mm_state.stats[hist][i]); 5914 } else if (seq != max_seq && NR_HIST_GENS > 1) { 5915 s = "loynfa"; 5916 n = READ_ONCE(lruvec->mm_state.stats[hist][i]); 5917 } 5918 5919 seq_printf(m, " %10lu%c", n, s[i]); 5920 } 5921 seq_putc(m, '\n'); 5922 } 5923 5924 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */ 5925 static int lru_gen_seq_show(struct seq_file *m, void *v) 5926 { 5927 unsigned long seq; 5928 bool full = !debugfs_real_fops(m->file)->write; 5929 struct lruvec *lruvec = v; 5930 struct lru_gen_folio *lrugen = &lruvec->lrugen; 5931 int nid = lruvec_pgdat(lruvec)->node_id; 5932 struct mem_cgroup *memcg = lruvec_memcg(lruvec); 5933 DEFINE_MAX_SEQ(lruvec); 5934 DEFINE_MIN_SEQ(lruvec); 5935 5936 if (nid == first_memory_node) { 5937 const char *path = memcg ? m->private : ""; 5938 5939 #ifdef CONFIG_MEMCG 5940 if (memcg) 5941 cgroup_path(memcg->css.cgroup, m->private, PATH_MAX); 5942 #endif 5943 seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path); 5944 } 5945 5946 seq_printf(m, " node %5d\n", nid); 5947 5948 if (!full) 5949 seq = min_seq[LRU_GEN_ANON]; 5950 else if (max_seq >= MAX_NR_GENS) 5951 seq = max_seq - MAX_NR_GENS + 1; 5952 else 5953 seq = 0; 5954 5955 for (; seq <= max_seq; seq++) { 5956 int type, zone; 5957 int gen = lru_gen_from_seq(seq); 5958 unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]); 5959 5960 seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth)); 5961 5962 for (type = 0; type < ANON_AND_FILE; type++) { 5963 unsigned long size = 0; 5964 char mark = full && seq < min_seq[type] ? 'x' : ' '; 5965 5966 for (zone = 0; zone < MAX_NR_ZONES; zone++) 5967 size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); 5968 5969 seq_printf(m, " %10lu%c", size, mark); 5970 } 5971 5972 seq_putc(m, '\n'); 5973 5974 if (full) 5975 lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq); 5976 } 5977 5978 return 0; 5979 } 5980 5981 static const struct seq_operations lru_gen_seq_ops = { 5982 .start = lru_gen_seq_start, 5983 .stop = lru_gen_seq_stop, 5984 .next = lru_gen_seq_next, 5985 .show = lru_gen_seq_show, 5986 }; 5987 5988 static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, 5989 bool can_swap, bool force_scan) 5990 { 5991 DEFINE_MAX_SEQ(lruvec); 5992 DEFINE_MIN_SEQ(lruvec); 5993 5994 if (seq < max_seq) 5995 return 0; 5996 5997 if (seq > max_seq) 5998 return -EINVAL; 5999 6000 if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq) 6001 return -ERANGE; 6002 6003 try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, force_scan); 6004 6005 return 0; 6006 } 6007 6008 static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, 6009 int swappiness, unsigned long nr_to_reclaim) 6010 { 6011 DEFINE_MAX_SEQ(lruvec); 6012 6013 if (seq + MIN_NR_GENS > max_seq) 6014 return -EINVAL; 6015 6016 sc->nr_reclaimed = 0; 6017 6018 while (!signal_pending(current)) { 6019 DEFINE_MIN_SEQ(lruvec); 6020 6021 if (seq < min_seq[!swappiness]) 6022 return 0; 6023 6024 if (sc->nr_reclaimed >= nr_to_reclaim) 6025 return 0; 6026 6027 if (!evict_folios(lruvec, sc, swappiness)) 6028 return 0; 6029 6030 cond_resched(); 6031 } 6032 6033 return -EINTR; 6034 } 6035 6036 static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq, 6037 struct scan_control *sc, int swappiness, unsigned long opt) 6038 { 6039 struct lruvec *lruvec; 6040 int err = -EINVAL; 6041 struct mem_cgroup *memcg = NULL; 6042 6043 if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY)) 6044 return -EINVAL; 6045 6046 if (!mem_cgroup_disabled()) { 6047 rcu_read_lock(); 6048 6049 memcg = mem_cgroup_from_id(memcg_id); 6050 if (!mem_cgroup_tryget(memcg)) 6051 memcg = NULL; 6052 6053 rcu_read_unlock(); 6054 6055 if (!memcg) 6056 return -EINVAL; 6057 } 6058 6059 if (memcg_id != mem_cgroup_id(memcg)) 6060 goto done; 6061 6062 lruvec = get_lruvec(memcg, nid); 6063 6064 if (swappiness < 0) 6065 swappiness = get_swappiness(lruvec, sc); 6066 else if (swappiness > 200) 6067 goto done; 6068 6069 switch (cmd) { 6070 case '+': 6071 err = run_aging(lruvec, seq, sc, swappiness, opt); 6072 break; 6073 case '-': 6074 err = run_eviction(lruvec, seq, sc, swappiness, opt); 6075 break; 6076 } 6077 done: 6078 mem_cgroup_put(memcg); 6079 6080 return err; 6081 } 6082 6083 /* see Documentation/admin-guide/mm/multigen_lru.rst for details */ 6084 static ssize_t lru_gen_seq_write(struct file *file, const char __user *src, 6085 size_t len, loff_t *pos) 6086 { 6087 void *buf; 6088 char *cur, *next; 6089 unsigned int flags; 6090 struct blk_plug plug; 6091 int err = -EINVAL; 6092 struct scan_control sc = { 6093 .may_writepage = true, 6094 .may_unmap = true, 6095 .may_swap = true, 6096 .reclaim_idx = MAX_NR_ZONES - 1, 6097 .gfp_mask = GFP_KERNEL, 6098 }; 6099 6100 buf = kvmalloc(len + 1, GFP_KERNEL); 6101 if (!buf) 6102 return -ENOMEM; 6103 6104 if (copy_from_user(buf, src, len)) { 6105 kvfree(buf); 6106 return -EFAULT; 6107 } 6108 6109 set_task_reclaim_state(current, &sc.reclaim_state); 6110 flags = memalloc_noreclaim_save(); 6111 blk_start_plug(&plug); 6112 if (!set_mm_walk(NULL, true)) { 6113 err = -ENOMEM; 6114 goto done; 6115 } 6116 6117 next = buf; 6118 next[len] = '\0'; 6119 6120 while ((cur = strsep(&next, ",;\n"))) { 6121 int n; 6122 int end; 6123 char cmd; 6124 unsigned int memcg_id; 6125 unsigned int nid; 6126 unsigned long seq; 6127 unsigned int swappiness = -1; 6128 unsigned long opt = -1; 6129 6130 cur = skip_spaces(cur); 6131 if (!*cur) 6132 continue; 6133 6134 n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid, 6135 &seq, &end, &swappiness, &end, &opt, &end); 6136 if (n < 4 || cur[end]) { 6137 err = -EINVAL; 6138 break; 6139 } 6140 6141 err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt); 6142 if (err) 6143 break; 6144 } 6145 done: 6146 clear_mm_walk(); 6147 blk_finish_plug(&plug); 6148 memalloc_noreclaim_restore(flags); 6149 set_task_reclaim_state(current, NULL); 6150 6151 kvfree(buf); 6152 6153 return err ? : len; 6154 } 6155 6156 static int lru_gen_seq_open(struct inode *inode, struct file *file) 6157 { 6158 return seq_open(file, &lru_gen_seq_ops); 6159 } 6160 6161 static const struct file_operations lru_gen_rw_fops = { 6162 .open = lru_gen_seq_open, 6163 .read = seq_read, 6164 .write = lru_gen_seq_write, 6165 .llseek = seq_lseek, 6166 .release = seq_release, 6167 }; 6168 6169 static const struct file_operations lru_gen_ro_fops = { 6170 .open = lru_gen_seq_open, 6171 .read = seq_read, 6172 .llseek = seq_lseek, 6173 .release = seq_release, 6174 }; 6175 6176 /****************************************************************************** 6177 * initialization 6178 ******************************************************************************/ 6179 6180 void lru_gen_init_lruvec(struct lruvec *lruvec) 6181 { 6182 int i; 6183 int gen, type, zone; 6184 struct lru_gen_folio *lrugen = &lruvec->lrugen; 6185 6186 lrugen->max_seq = MIN_NR_GENS + 1; 6187 lrugen->enabled = lru_gen_enabled(); 6188 6189 for (i = 0; i <= MIN_NR_GENS + 1; i++) 6190 lrugen->timestamps[i] = jiffies; 6191 6192 for_each_gen_type_zone(gen, type, zone) 6193 INIT_LIST_HEAD(&lrugen->folios[gen][type][zone]); 6194 6195 lruvec->mm_state.seq = MIN_NR_GENS; 6196 } 6197 6198 #ifdef CONFIG_MEMCG 6199 6200 void lru_gen_init_pgdat(struct pglist_data *pgdat) 6201 { 6202 int i, j; 6203 6204 spin_lock_init(&pgdat->memcg_lru.lock); 6205 6206 for (i = 0; i < MEMCG_NR_GENS; i++) { 6207 for (j = 0; j < MEMCG_NR_BINS; j++) 6208 INIT_HLIST_NULLS_HEAD(&pgdat->memcg_lru.fifo[i][j], i); 6209 } 6210 } 6211 6212 void lru_gen_init_memcg(struct mem_cgroup *memcg) 6213 { 6214 INIT_LIST_HEAD(&memcg->mm_list.fifo); 6215 spin_lock_init(&memcg->mm_list.lock); 6216 } 6217 6218 void lru_gen_exit_memcg(struct mem_cgroup *memcg) 6219 { 6220 int i; 6221 int nid; 6222 6223 VM_WARN_ON_ONCE(!list_empty(&memcg->mm_list.fifo)); 6224 6225 for_each_node(nid) { 6226 struct lruvec *lruvec = get_lruvec(memcg, nid); 6227 6228 VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0, 6229 sizeof(lruvec->lrugen.nr_pages))); 6230 6231 lruvec->lrugen.list.next = LIST_POISON1; 6232 6233 for (i = 0; i < NR_BLOOM_FILTERS; i++) { 6234 bitmap_free(lruvec->mm_state.filters[i]); 6235 lruvec->mm_state.filters[i] = NULL; 6236 } 6237 } 6238 } 6239 6240 #endif /* CONFIG_MEMCG */ 6241 6242 static int __init init_lru_gen(void) 6243 { 6244 BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS); 6245 BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS); 6246 6247 if (sysfs_create_group(mm_kobj, &lru_gen_attr_group)) 6248 pr_err("lru_gen: failed to create sysfs group\n"); 6249 6250 debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops); 6251 debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops); 6252 6253 return 0; 6254 }; 6255 late_initcall(init_lru_gen); 6256 6257 #else /* !CONFIG_LRU_GEN */ 6258 6259 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc) 6260 { 6261 } 6262 6263 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) 6264 { 6265 } 6266 6267 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc) 6268 { 6269 } 6270 6271 #endif /* CONFIG_LRU_GEN */ 6272 6273 static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) 6274 { 6275 unsigned long nr[NR_LRU_LISTS]; 6276 unsigned long targets[NR_LRU_LISTS]; 6277 unsigned long nr_to_scan; 6278 enum lru_list lru; 6279 unsigned long nr_reclaimed = 0; 6280 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 6281 bool proportional_reclaim; 6282 struct blk_plug plug; 6283 6284 if (lru_gen_enabled() && !root_reclaim(sc)) { 6285 lru_gen_shrink_lruvec(lruvec, sc); 6286 return; 6287 } 6288 6289 get_scan_count(lruvec, sc, nr); 6290 6291 /* Record the original scan target for proportional adjustments later */ 6292 memcpy(targets, nr, sizeof(nr)); 6293 6294 /* 6295 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal 6296 * event that can occur when there is little memory pressure e.g. 6297 * multiple streaming readers/writers. Hence, we do not abort scanning 6298 * when the requested number of pages are reclaimed when scanning at 6299 * DEF_PRIORITY on the assumption that the fact we are direct 6300 * reclaiming implies that kswapd is not keeping up and it is best to 6301 * do a batch of work at once. For memcg reclaim one check is made to 6302 * abort proportional reclaim if either the file or anon lru has already 6303 * dropped to zero at the first pass. 6304 */ 6305 proportional_reclaim = (!cgroup_reclaim(sc) && !current_is_kswapd() && 6306 sc->priority == DEF_PRIORITY); 6307 6308 blk_start_plug(&plug); 6309 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 6310 nr[LRU_INACTIVE_FILE]) { 6311 unsigned long nr_anon, nr_file, percentage; 6312 unsigned long nr_scanned; 6313 6314 for_each_evictable_lru(lru) { 6315 if (nr[lru]) { 6316 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); 6317 nr[lru] -= nr_to_scan; 6318 6319 nr_reclaimed += shrink_list(lru, nr_to_scan, 6320 lruvec, sc); 6321 } 6322 } 6323 6324 cond_resched(); 6325 6326 if (nr_reclaimed < nr_to_reclaim || proportional_reclaim) 6327 continue; 6328 6329 /* 6330 * For kswapd and memcg, reclaim at least the number of pages 6331 * requested. Ensure that the anon and file LRUs are scanned 6332 * proportionally what was requested by get_scan_count(). We 6333 * stop reclaiming one LRU and reduce the amount scanning 6334 * proportional to the original scan target. 6335 */ 6336 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; 6337 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; 6338 6339 /* 6340 * It's just vindictive to attack the larger once the smaller 6341 * has gone to zero. And given the way we stop scanning the 6342 * smaller below, this makes sure that we only make one nudge 6343 * towards proportionality once we've got nr_to_reclaim. 6344 */ 6345 if (!nr_file || !nr_anon) 6346 break; 6347 6348 if (nr_file > nr_anon) { 6349 unsigned long scan_target = targets[LRU_INACTIVE_ANON] + 6350 targets[LRU_ACTIVE_ANON] + 1; 6351 lru = LRU_BASE; 6352 percentage = nr_anon * 100 / scan_target; 6353 } else { 6354 unsigned long scan_target = targets[LRU_INACTIVE_FILE] + 6355 targets[LRU_ACTIVE_FILE] + 1; 6356 lru = LRU_FILE; 6357 percentage = nr_file * 100 / scan_target; 6358 } 6359 6360 /* Stop scanning the smaller of the LRU */ 6361 nr[lru] = 0; 6362 nr[lru + LRU_ACTIVE] = 0; 6363 6364 /* 6365 * Recalculate the other LRU scan count based on its original 6366 * scan target and the percentage scanning already complete 6367 */ 6368 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; 6369 nr_scanned = targets[lru] - nr[lru]; 6370 nr[lru] = targets[lru] * (100 - percentage) / 100; 6371 nr[lru] -= min(nr[lru], nr_scanned); 6372 6373 lru += LRU_ACTIVE; 6374 nr_scanned = targets[lru] - nr[lru]; 6375 nr[lru] = targets[lru] * (100 - percentage) / 100; 6376 nr[lru] -= min(nr[lru], nr_scanned); 6377 } 6378 blk_finish_plug(&plug); 6379 sc->nr_reclaimed += nr_reclaimed; 6380 6381 /* 6382 * Even if we did not try to evict anon pages at all, we want to 6383 * rebalance the anon lru active/inactive ratio. 6384 */ 6385 if (can_age_anon_pages(lruvec_pgdat(lruvec), sc) && 6386 inactive_is_low(lruvec, LRU_INACTIVE_ANON)) 6387 shrink_active_list(SWAP_CLUSTER_MAX, lruvec, 6388 sc, LRU_ACTIVE_ANON); 6389 } 6390 6391 /* Use reclaim/compaction for costly allocs or under memory pressure */ 6392 static bool in_reclaim_compaction(struct scan_control *sc) 6393 { 6394 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && 6395 (sc->order > PAGE_ALLOC_COSTLY_ORDER || 6396 sc->priority < DEF_PRIORITY - 2)) 6397 return true; 6398 6399 return false; 6400 } 6401 6402 /* 6403 * Reclaim/compaction is used for high-order allocation requests. It reclaims 6404 * order-0 pages before compacting the zone. should_continue_reclaim() returns 6405 * true if more pages should be reclaimed such that when the page allocator 6406 * calls try_to_compact_pages() that it will have enough free pages to succeed. 6407 * It will give up earlier than that if there is difficulty reclaiming pages. 6408 */ 6409 static inline bool should_continue_reclaim(struct pglist_data *pgdat, 6410 unsigned long nr_reclaimed, 6411 struct scan_control *sc) 6412 { 6413 unsigned long pages_for_compaction; 6414 unsigned long inactive_lru_pages; 6415 int z; 6416 6417 /* If not in reclaim/compaction mode, stop */ 6418 if (!in_reclaim_compaction(sc)) 6419 return false; 6420 6421 /* 6422 * Stop if we failed to reclaim any pages from the last SWAP_CLUSTER_MAX 6423 * number of pages that were scanned. This will return to the caller 6424 * with the risk reclaim/compaction and the resulting allocation attempt 6425 * fails. In the past we have tried harder for __GFP_RETRY_MAYFAIL 6426 * allocations through requiring that the full LRU list has been scanned 6427 * first, by assuming that zero delta of sc->nr_scanned means full LRU 6428 * scan, but that approximation was wrong, and there were corner cases 6429 * where always a non-zero amount of pages were scanned. 6430 */ 6431 if (!nr_reclaimed) 6432 return false; 6433 6434 /* If compaction would go ahead or the allocation would succeed, stop */ 6435 for (z = 0; z <= sc->reclaim_idx; z++) { 6436 struct zone *zone = &pgdat->node_zones[z]; 6437 if (!managed_zone(zone)) 6438 continue; 6439 6440 /* Allocation can already succeed, nothing to do */ 6441 if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone), 6442 sc->reclaim_idx, 0)) 6443 return false; 6444 6445 if (compaction_suitable(zone, sc->order, sc->reclaim_idx)) 6446 return false; 6447 } 6448 6449 /* 6450 * If we have not reclaimed enough pages for compaction and the 6451 * inactive lists are large enough, continue reclaiming 6452 */ 6453 pages_for_compaction = compact_gap(sc->order); 6454 inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); 6455 if (can_reclaim_anon_pages(NULL, pgdat->node_id, sc)) 6456 inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); 6457 6458 return inactive_lru_pages > pages_for_compaction; 6459 } 6460 6461 static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) 6462 { 6463 struct mem_cgroup *target_memcg = sc->target_mem_cgroup; 6464 struct mem_cgroup *memcg; 6465 6466 memcg = mem_cgroup_iter(target_memcg, NULL, NULL); 6467 do { 6468 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); 6469 unsigned long reclaimed; 6470 unsigned long scanned; 6471 6472 /* 6473 * This loop can become CPU-bound when target memcgs 6474 * aren't eligible for reclaim - either because they 6475 * don't have any reclaimable pages, or because their 6476 * memory is explicitly protected. Avoid soft lockups. 6477 */ 6478 cond_resched(); 6479 6480 mem_cgroup_calculate_protection(target_memcg, memcg); 6481 6482 if (mem_cgroup_below_min(target_memcg, memcg)) { 6483 /* 6484 * Hard protection. 6485 * If there is no reclaimable memory, OOM. 6486 */ 6487 continue; 6488 } else if (mem_cgroup_below_low(target_memcg, memcg)) { 6489 /* 6490 * Soft protection. 6491 * Respect the protection only as long as 6492 * there is an unprotected supply 6493 * of reclaimable memory from other cgroups. 6494 */ 6495 if (!sc->memcg_low_reclaim) { 6496 sc->memcg_low_skipped = 1; 6497 continue; 6498 } 6499 memcg_memory_event(memcg, MEMCG_LOW); 6500 } 6501 6502 reclaimed = sc->nr_reclaimed; 6503 scanned = sc->nr_scanned; 6504 6505 shrink_lruvec(lruvec, sc); 6506 6507 shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, 6508 sc->priority); 6509 6510 /* Record the group's reclaim efficiency */ 6511 if (!sc->proactive) 6512 vmpressure(sc->gfp_mask, memcg, false, 6513 sc->nr_scanned - scanned, 6514 sc->nr_reclaimed - reclaimed); 6515 6516 } while ((memcg = mem_cgroup_iter(target_memcg, memcg, NULL))); 6517 } 6518 6519 static void shrink_node(pg_data_t *pgdat, struct scan_control *sc) 6520 { 6521 unsigned long nr_reclaimed, nr_scanned, nr_node_reclaimed; 6522 struct lruvec *target_lruvec; 6523 bool reclaimable = false; 6524 6525 if (lru_gen_enabled() && root_reclaim(sc)) { 6526 lru_gen_shrink_node(pgdat, sc); 6527 return; 6528 } 6529 6530 target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat); 6531 6532 again: 6533 memset(&sc->nr, 0, sizeof(sc->nr)); 6534 6535 nr_reclaimed = sc->nr_reclaimed; 6536 nr_scanned = sc->nr_scanned; 6537 6538 prepare_scan_count(pgdat, sc); 6539 6540 shrink_node_memcgs(pgdat, sc); 6541 6542 flush_reclaim_state(sc); 6543 6544 nr_node_reclaimed = sc->nr_reclaimed - nr_reclaimed; 6545 6546 /* Record the subtree's reclaim efficiency */ 6547 if (!sc->proactive) 6548 vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, 6549 sc->nr_scanned - nr_scanned, nr_node_reclaimed); 6550 6551 if (nr_node_reclaimed) 6552 reclaimable = true; 6553 6554 if (current_is_kswapd()) { 6555 /* 6556 * If reclaim is isolating dirty pages under writeback, 6557 * it implies that the long-lived page allocation rate 6558 * is exceeding the page laundering rate. Either the 6559 * global limits are not being effective at throttling 6560 * processes due to the page distribution throughout 6561 * zones or there is heavy usage of a slow backing 6562 * device. The only option is to throttle from reclaim 6563 * context which is not ideal as there is no guarantee 6564 * the dirtying process is throttled in the same way 6565 * balance_dirty_pages() manages. 6566 * 6567 * Once a node is flagged PGDAT_WRITEBACK, kswapd will 6568 * count the number of pages under pages flagged for 6569 * immediate reclaim and stall if any are encountered 6570 * in the nr_immediate check below. 6571 */ 6572 if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken) 6573 set_bit(PGDAT_WRITEBACK, &pgdat->flags); 6574 6575 /* Allow kswapd to start writing pages during reclaim.*/ 6576 if (sc->nr.unqueued_dirty == sc->nr.file_taken) 6577 set_bit(PGDAT_DIRTY, &pgdat->flags); 6578 6579 /* 6580 * If kswapd scans pages marked for immediate 6581 * reclaim and under writeback (nr_immediate), it 6582 * implies that pages are cycling through the LRU 6583 * faster than they are written so forcibly stall 6584 * until some pages complete writeback. 6585 */ 6586 if (sc->nr.immediate) 6587 reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK); 6588 } 6589 6590 /* 6591 * Tag a node/memcg as congested if all the dirty pages were marked 6592 * for writeback and immediate reclaim (counted in nr.congested). 6593 * 6594 * Legacy memcg will stall in page writeback so avoid forcibly 6595 * stalling in reclaim_throttle(). 6596 */ 6597 if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) { 6598 if (cgroup_reclaim(sc) && writeback_throttling_sane(sc)) 6599 set_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags); 6600 6601 if (current_is_kswapd()) 6602 set_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags); 6603 } 6604 6605 /* 6606 * Stall direct reclaim for IO completions if the lruvec is 6607 * node is congested. Allow kswapd to continue until it 6608 * starts encountering unqueued dirty pages or cycling through 6609 * the LRU too quickly. 6610 */ 6611 if (!current_is_kswapd() && current_may_throttle() && 6612 !sc->hibernation_mode && 6613 (test_bit(LRUVEC_CGROUP_CONGESTED, &target_lruvec->flags) || 6614 test_bit(LRUVEC_NODE_CONGESTED, &target_lruvec->flags))) 6615 reclaim_throttle(pgdat, VMSCAN_THROTTLE_CONGESTED); 6616 6617 if (should_continue_reclaim(pgdat, nr_node_reclaimed, sc)) 6618 goto again; 6619 6620 /* 6621 * Kswapd gives up on balancing particular nodes after too 6622 * many failures to reclaim anything from them and goes to 6623 * sleep. On reclaim progress, reset the failure counter. A 6624 * successful direct reclaim run will revive a dormant kswapd. 6625 */ 6626 if (reclaimable) 6627 pgdat->kswapd_failures = 0; 6628 } 6629 6630 /* 6631 * Returns true if compaction should go ahead for a costly-order request, or 6632 * the allocation would already succeed without compaction. Return false if we 6633 * should reclaim first. 6634 */ 6635 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) 6636 { 6637 unsigned long watermark; 6638 6639 /* Allocation can already succeed, nothing to do */ 6640 if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone), 6641 sc->reclaim_idx, 0)) 6642 return true; 6643 6644 /* Compaction cannot yet proceed. Do reclaim. */ 6645 if (!compaction_suitable(zone, sc->order, sc->reclaim_idx)) 6646 return false; 6647 6648 /* 6649 * Compaction is already possible, but it takes time to run and there 6650 * are potentially other callers using the pages just freed. So proceed 6651 * with reclaim to make a buffer of free pages available to give 6652 * compaction a reasonable chance of completing and allocating the page. 6653 * Note that we won't actually reclaim the whole buffer in one attempt 6654 * as the target watermark in should_continue_reclaim() is lower. But if 6655 * we are already above the high+gap watermark, don't reclaim at all. 6656 */ 6657 watermark = high_wmark_pages(zone) + compact_gap(sc->order); 6658 6659 return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx); 6660 } 6661 6662 static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc) 6663 { 6664 /* 6665 * If reclaim is making progress greater than 12% efficiency then 6666 * wake all the NOPROGRESS throttled tasks. 6667 */ 6668 if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) { 6669 wait_queue_head_t *wqh; 6670 6671 wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS]; 6672 if (waitqueue_active(wqh)) 6673 wake_up(wqh); 6674 6675 return; 6676 } 6677 6678 /* 6679 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will 6680 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages 6681 * under writeback and marked for immediate reclaim at the tail of the 6682 * LRU. 6683 */ 6684 if (current_is_kswapd() || cgroup_reclaim(sc)) 6685 return; 6686 6687 /* Throttle if making no progress at high prioities. */ 6688 if (sc->priority == 1 && !sc->nr_reclaimed) 6689 reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS); 6690 } 6691 6692 /* 6693 * This is the direct reclaim path, for page-allocating processes. We only 6694 * try to reclaim pages from zones which will satisfy the caller's allocation 6695 * request. 6696 * 6697 * If a zone is deemed to be full of pinned pages then just give it a light 6698 * scan then give up on it. 6699 */ 6700 static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) 6701 { 6702 struct zoneref *z; 6703 struct zone *zone; 6704 unsigned long nr_soft_reclaimed; 6705 unsigned long nr_soft_scanned; 6706 gfp_t orig_mask; 6707 pg_data_t *last_pgdat = NULL; 6708 pg_data_t *first_pgdat = NULL; 6709 6710 /* 6711 * If the number of buffer_heads in the machine exceeds the maximum 6712 * allowed level, force direct reclaim to scan the highmem zone as 6713 * highmem pages could be pinning lowmem pages storing buffer_heads 6714 */ 6715 orig_mask = sc->gfp_mask; 6716 if (buffer_heads_over_limit) { 6717 sc->gfp_mask |= __GFP_HIGHMEM; 6718 sc->reclaim_idx = gfp_zone(sc->gfp_mask); 6719 } 6720 6721 for_each_zone_zonelist_nodemask(zone, z, zonelist, 6722 sc->reclaim_idx, sc->nodemask) { 6723 /* 6724 * Take care memory controller reclaiming has small influence 6725 * to global LRU. 6726 */ 6727 if (!cgroup_reclaim(sc)) { 6728 if (!cpuset_zone_allowed(zone, 6729 GFP_KERNEL | __GFP_HARDWALL)) 6730 continue; 6731 6732 /* 6733 * If we already have plenty of memory free for 6734 * compaction in this zone, don't free any more. 6735 * Even though compaction is invoked for any 6736 * non-zero order, only frequent costly order 6737 * reclamation is disruptive enough to become a 6738 * noticeable problem, like transparent huge 6739 * page allocations. 6740 */ 6741 if (IS_ENABLED(CONFIG_COMPACTION) && 6742 sc->order > PAGE_ALLOC_COSTLY_ORDER && 6743 compaction_ready(zone, sc)) { 6744 sc->compaction_ready = true; 6745 continue; 6746 } 6747 6748 /* 6749 * Shrink each node in the zonelist once. If the 6750 * zonelist is ordered by zone (not the default) then a 6751 * node may be shrunk multiple times but in that case 6752 * the user prefers lower zones being preserved. 6753 */ 6754 if (zone->zone_pgdat == last_pgdat) 6755 continue; 6756 6757 /* 6758 * This steals pages from memory cgroups over softlimit 6759 * and returns the number of reclaimed pages and 6760 * scanned pages. This works for global memory pressure 6761 * and balancing, not for a memcg's limit. 6762 */ 6763 nr_soft_scanned = 0; 6764 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat, 6765 sc->order, sc->gfp_mask, 6766 &nr_soft_scanned); 6767 sc->nr_reclaimed += nr_soft_reclaimed; 6768 sc->nr_scanned += nr_soft_scanned; 6769 /* need some check for avoid more shrink_zone() */ 6770 } 6771 6772 if (!first_pgdat) 6773 first_pgdat = zone->zone_pgdat; 6774 6775 /* See comment about same check for global reclaim above */ 6776 if (zone->zone_pgdat == last_pgdat) 6777 continue; 6778 last_pgdat = zone->zone_pgdat; 6779 shrink_node(zone->zone_pgdat, sc); 6780 } 6781 6782 if (first_pgdat) 6783 consider_reclaim_throttle(first_pgdat, sc); 6784 6785 /* 6786 * Restore to original mask to avoid the impact on the caller if we 6787 * promoted it to __GFP_HIGHMEM. 6788 */ 6789 sc->gfp_mask = orig_mask; 6790 } 6791 6792 static void snapshot_refaults(struct mem_cgroup *target_memcg, pg_data_t *pgdat) 6793 { 6794 struct lruvec *target_lruvec; 6795 unsigned long refaults; 6796 6797 if (lru_gen_enabled()) 6798 return; 6799 6800 target_lruvec = mem_cgroup_lruvec(target_memcg, pgdat); 6801 refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_ANON); 6802 target_lruvec->refaults[WORKINGSET_ANON] = refaults; 6803 refaults = lruvec_page_state(target_lruvec, WORKINGSET_ACTIVATE_FILE); 6804 target_lruvec->refaults[WORKINGSET_FILE] = refaults; 6805 } 6806 6807 /* 6808 * This is the main entry point to direct page reclaim. 6809 * 6810 * If a full scan of the inactive list fails to free enough memory then we 6811 * are "out of memory" and something needs to be killed. 6812 * 6813 * If the caller is !__GFP_FS then the probability of a failure is reasonably 6814 * high - the zone may be full of dirty or under-writeback pages, which this 6815 * caller can't do much about. We kick the writeback threads and take explicit 6816 * naps in the hope that some of these pages can be written. But if the 6817 * allocating task holds filesystem locks which prevent writeout this might not 6818 * work, and the allocation attempt will fail. 6819 * 6820 * returns: 0, if no pages reclaimed 6821 * else, the number of pages reclaimed 6822 */ 6823 static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 6824 struct scan_control *sc) 6825 { 6826 int initial_priority = sc->priority; 6827 pg_data_t *last_pgdat; 6828 struct zoneref *z; 6829 struct zone *zone; 6830 retry: 6831 delayacct_freepages_start(); 6832 6833 if (!cgroup_reclaim(sc)) 6834 __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1); 6835 6836 do { 6837 if (!sc->proactive) 6838 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, 6839 sc->priority); 6840 sc->nr_scanned = 0; 6841 shrink_zones(zonelist, sc); 6842 6843 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 6844 break; 6845 6846 if (sc->compaction_ready) 6847 break; 6848 6849 /* 6850 * If we're getting trouble reclaiming, start doing 6851 * writepage even in laptop mode. 6852 */ 6853 if (sc->priority < DEF_PRIORITY - 2) 6854 sc->may_writepage = 1; 6855 } while (--sc->priority >= 0); 6856 6857 last_pgdat = NULL; 6858 for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx, 6859 sc->nodemask) { 6860 if (zone->zone_pgdat == last_pgdat) 6861 continue; 6862 last_pgdat = zone->zone_pgdat; 6863 6864 snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat); 6865 6866 if (cgroup_reclaim(sc)) { 6867 struct lruvec *lruvec; 6868 6869 lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, 6870 zone->zone_pgdat); 6871 clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags); 6872 } 6873 } 6874 6875 delayacct_freepages_end(); 6876 6877 if (sc->nr_reclaimed) 6878 return sc->nr_reclaimed; 6879 6880 /* Aborted reclaim to try compaction? don't OOM, then */ 6881 if (sc->compaction_ready) 6882 return 1; 6883 6884 /* 6885 * We make inactive:active ratio decisions based on the node's 6886 * composition of memory, but a restrictive reclaim_idx or a 6887 * memory.low cgroup setting can exempt large amounts of 6888 * memory from reclaim. Neither of which are very common, so 6889 * instead of doing costly eligibility calculations of the 6890 * entire cgroup subtree up front, we assume the estimates are 6891 * good, and retry with forcible deactivation if that fails. 6892 */ 6893 if (sc->skipped_deactivate) { 6894 sc->priority = initial_priority; 6895 sc->force_deactivate = 1; 6896 sc->skipped_deactivate = 0; 6897 goto retry; 6898 } 6899 6900 /* Untapped cgroup reserves? Don't OOM, retry. */ 6901 if (sc->memcg_low_skipped) { 6902 sc->priority = initial_priority; 6903 sc->force_deactivate = 0; 6904 sc->memcg_low_reclaim = 1; 6905 sc->memcg_low_skipped = 0; 6906 goto retry; 6907 } 6908 6909 return 0; 6910 } 6911 6912 static bool allow_direct_reclaim(pg_data_t *pgdat) 6913 { 6914 struct zone *zone; 6915 unsigned long pfmemalloc_reserve = 0; 6916 unsigned long free_pages = 0; 6917 int i; 6918 bool wmark_ok; 6919 6920 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) 6921 return true; 6922 6923 for (i = 0; i <= ZONE_NORMAL; i++) { 6924 zone = &pgdat->node_zones[i]; 6925 if (!managed_zone(zone)) 6926 continue; 6927 6928 if (!zone_reclaimable_pages(zone)) 6929 continue; 6930 6931 pfmemalloc_reserve += min_wmark_pages(zone); 6932 free_pages += zone_page_state_snapshot(zone, NR_FREE_PAGES); 6933 } 6934 6935 /* If there are no reserves (unexpected config) then do not throttle */ 6936 if (!pfmemalloc_reserve) 6937 return true; 6938 6939 wmark_ok = free_pages > pfmemalloc_reserve / 2; 6940 6941 /* kswapd must be awake if processes are being throttled */ 6942 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) { 6943 if (READ_ONCE(pgdat->kswapd_highest_zoneidx) > ZONE_NORMAL) 6944 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, ZONE_NORMAL); 6945 6946 wake_up_interruptible(&pgdat->kswapd_wait); 6947 } 6948 6949 return wmark_ok; 6950 } 6951 6952 /* 6953 * Throttle direct reclaimers if backing storage is backed by the network 6954 * and the PFMEMALLOC reserve for the preferred node is getting dangerously 6955 * depleted. kswapd will continue to make progress and wake the processes 6956 * when the low watermark is reached. 6957 * 6958 * Returns true if a fatal signal was delivered during throttling. If this 6959 * happens, the page allocator should not consider triggering the OOM killer. 6960 */ 6961 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, 6962 nodemask_t *nodemask) 6963 { 6964 struct zoneref *z; 6965 struct zone *zone; 6966 pg_data_t *pgdat = NULL; 6967 6968 /* 6969 * Kernel threads should not be throttled as they may be indirectly 6970 * responsible for cleaning pages necessary for reclaim to make forward 6971 * progress. kjournald for example may enter direct reclaim while 6972 * committing a transaction where throttling it could forcing other 6973 * processes to block on log_wait_commit(). 6974 */ 6975 if (current->flags & PF_KTHREAD) 6976 goto out; 6977 6978 /* 6979 * If a fatal signal is pending, this process should not throttle. 6980 * It should return quickly so it can exit and free its memory 6981 */ 6982 if (fatal_signal_pending(current)) 6983 goto out; 6984 6985 /* 6986 * Check if the pfmemalloc reserves are ok by finding the first node 6987 * with a usable ZONE_NORMAL or lower zone. The expectation is that 6988 * GFP_KERNEL will be required for allocating network buffers when 6989 * swapping over the network so ZONE_HIGHMEM is unusable. 6990 * 6991 * Throttling is based on the first usable node and throttled processes 6992 * wait on a queue until kswapd makes progress and wakes them. There 6993 * is an affinity then between processes waking up and where reclaim 6994 * progress has been made assuming the process wakes on the same node. 6995 * More importantly, processes running on remote nodes will not compete 6996 * for remote pfmemalloc reserves and processes on different nodes 6997 * should make reasonable progress. 6998 */ 6999 for_each_zone_zonelist_nodemask(zone, z, zonelist, 7000 gfp_zone(gfp_mask), nodemask) { 7001 if (zone_idx(zone) > ZONE_NORMAL) 7002 continue; 7003 7004 /* Throttle based on the first usable node */ 7005 pgdat = zone->zone_pgdat; 7006 if (allow_direct_reclaim(pgdat)) 7007 goto out; 7008 break; 7009 } 7010 7011 /* If no zone was usable by the allocation flags then do not throttle */ 7012 if (!pgdat) 7013 goto out; 7014 7015 /* Account for the throttling */ 7016 count_vm_event(PGSCAN_DIRECT_THROTTLE); 7017 7018 /* 7019 * If the caller cannot enter the filesystem, it's possible that it 7020 * is due to the caller holding an FS lock or performing a journal 7021 * transaction in the case of a filesystem like ext[3|4]. In this case, 7022 * it is not safe to block on pfmemalloc_wait as kswapd could be 7023 * blocked waiting on the same lock. Instead, throttle for up to a 7024 * second before continuing. 7025 */ 7026 if (!(gfp_mask & __GFP_FS)) 7027 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait, 7028 allow_direct_reclaim(pgdat), HZ); 7029 else 7030 /* Throttle until kswapd wakes the process */ 7031 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait, 7032 allow_direct_reclaim(pgdat)); 7033 7034 if (fatal_signal_pending(current)) 7035 return true; 7036 7037 out: 7038 return false; 7039 } 7040 7041 unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 7042 gfp_t gfp_mask, nodemask_t *nodemask) 7043 { 7044 unsigned long nr_reclaimed; 7045 struct scan_control sc = { 7046 .nr_to_reclaim = SWAP_CLUSTER_MAX, 7047 .gfp_mask = current_gfp_context(gfp_mask), 7048 .reclaim_idx = gfp_zone(gfp_mask), 7049 .order = order, 7050 .nodemask = nodemask, 7051 .priority = DEF_PRIORITY, 7052 .may_writepage = !laptop_mode, 7053 .may_unmap = 1, 7054 .may_swap = 1, 7055 }; 7056 7057 /* 7058 * scan_control uses s8 fields for order, priority, and reclaim_idx. 7059 * Confirm they are large enough for max values. 7060 */ 7061 BUILD_BUG_ON(MAX_ORDER >= S8_MAX); 7062 BUILD_BUG_ON(DEF_PRIORITY > S8_MAX); 7063 BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX); 7064 7065 /* 7066 * Do not enter reclaim if fatal signal was delivered while throttled. 7067 * 1 is returned so that the page allocator does not OOM kill at this 7068 * point. 7069 */ 7070 if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask)) 7071 return 1; 7072 7073 set_task_reclaim_state(current, &sc.reclaim_state); 7074 trace_mm_vmscan_direct_reclaim_begin(order, sc.gfp_mask); 7075 7076 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 7077 7078 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 7079 set_task_reclaim_state(current, NULL); 7080 7081 return nr_reclaimed; 7082 } 7083 7084 #ifdef CONFIG_MEMCG 7085 7086 /* Only used by soft limit reclaim. Do not reuse for anything else. */ 7087 unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, 7088 gfp_t gfp_mask, bool noswap, 7089 pg_data_t *pgdat, 7090 unsigned long *nr_scanned) 7091 { 7092 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); 7093 struct scan_control sc = { 7094 .nr_to_reclaim = SWAP_CLUSTER_MAX, 7095 .target_mem_cgroup = memcg, 7096 .may_writepage = !laptop_mode, 7097 .may_unmap = 1, 7098 .reclaim_idx = MAX_NR_ZONES - 1, 7099 .may_swap = !noswap, 7100 }; 7101 7102 WARN_ON_ONCE(!current->reclaim_state); 7103 7104 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 7105 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 7106 7107 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order, 7108 sc.gfp_mask); 7109 7110 /* 7111 * NOTE: Although we can get the priority field, using it 7112 * here is not a good idea, since it limits the pages we can scan. 7113 * if we don't reclaim here, the shrink_node from balance_pgdat 7114 * will pick up pages from other mem cgroup's as well. We hack 7115 * the priority and make it zero. 7116 */ 7117 shrink_lruvec(lruvec, &sc); 7118 7119 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 7120 7121 *nr_scanned = sc.nr_scanned; 7122 7123 return sc.nr_reclaimed; 7124 } 7125 7126 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, 7127 unsigned long nr_pages, 7128 gfp_t gfp_mask, 7129 unsigned int reclaim_options) 7130 { 7131 unsigned long nr_reclaimed; 7132 unsigned int noreclaim_flag; 7133 struct scan_control sc = { 7134 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), 7135 .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) | 7136 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), 7137 .reclaim_idx = MAX_NR_ZONES - 1, 7138 .target_mem_cgroup = memcg, 7139 .priority = DEF_PRIORITY, 7140 .may_writepage = !laptop_mode, 7141 .may_unmap = 1, 7142 .may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP), 7143 .proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE), 7144 }; 7145 /* 7146 * Traverse the ZONELIST_FALLBACK zonelist of the current node to put 7147 * equal pressure on all the nodes. This is based on the assumption that 7148 * the reclaim does not bail out early. 7149 */ 7150 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 7151 7152 set_task_reclaim_state(current, &sc.reclaim_state); 7153 trace_mm_vmscan_memcg_reclaim_begin(0, sc.gfp_mask); 7154 noreclaim_flag = memalloc_noreclaim_save(); 7155 7156 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 7157 7158 memalloc_noreclaim_restore(noreclaim_flag); 7159 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 7160 set_task_reclaim_state(current, NULL); 7161 7162 return nr_reclaimed; 7163 } 7164 #endif 7165 7166 static void kswapd_age_node(struct pglist_data *pgdat, struct scan_control *sc) 7167 { 7168 struct mem_cgroup *memcg; 7169 struct lruvec *lruvec; 7170 7171 if (lru_gen_enabled()) { 7172 lru_gen_age_node(pgdat, sc); 7173 return; 7174 } 7175 7176 if (!can_age_anon_pages(pgdat, sc)) 7177 return; 7178 7179 lruvec = mem_cgroup_lruvec(NULL, pgdat); 7180 if (!inactive_is_low(lruvec, LRU_INACTIVE_ANON)) 7181 return; 7182 7183 memcg = mem_cgroup_iter(NULL, NULL, NULL); 7184 do { 7185 lruvec = mem_cgroup_lruvec(memcg, pgdat); 7186 shrink_active_list(SWAP_CLUSTER_MAX, lruvec, 7187 sc, LRU_ACTIVE_ANON); 7188 memcg = mem_cgroup_iter(NULL, memcg, NULL); 7189 } while (memcg); 7190 } 7191 7192 static bool pgdat_watermark_boosted(pg_data_t *pgdat, int highest_zoneidx) 7193 { 7194 int i; 7195 struct zone *zone; 7196 7197 /* 7198 * Check for watermark boosts top-down as the higher zones 7199 * are more likely to be boosted. Both watermarks and boosts 7200 * should not be checked at the same time as reclaim would 7201 * start prematurely when there is no boosting and a lower 7202 * zone is balanced. 7203 */ 7204 for (i = highest_zoneidx; i >= 0; i--) { 7205 zone = pgdat->node_zones + i; 7206 if (!managed_zone(zone)) 7207 continue; 7208 7209 if (zone->watermark_boost) 7210 return true; 7211 } 7212 7213 return false; 7214 } 7215 7216 /* 7217 * Returns true if there is an eligible zone balanced for the request order 7218 * and highest_zoneidx 7219 */ 7220 static bool pgdat_balanced(pg_data_t *pgdat, int order, int highest_zoneidx) 7221 { 7222 int i; 7223 unsigned long mark = -1; 7224 struct zone *zone; 7225 7226 /* 7227 * Check watermarks bottom-up as lower zones are more likely to 7228 * meet watermarks. 7229 */ 7230 for (i = 0; i <= highest_zoneidx; i++) { 7231 zone = pgdat->node_zones + i; 7232 7233 if (!managed_zone(zone)) 7234 continue; 7235 7236 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) 7237 mark = wmark_pages(zone, WMARK_PROMO); 7238 else 7239 mark = high_wmark_pages(zone); 7240 if (zone_watermark_ok_safe(zone, order, mark, highest_zoneidx)) 7241 return true; 7242 } 7243 7244 /* 7245 * If a node has no managed zone within highest_zoneidx, it does not 7246 * need balancing by definition. This can happen if a zone-restricted 7247 * allocation tries to wake a remote kswapd. 7248 */ 7249 if (mark == -1) 7250 return true; 7251 7252 return false; 7253 } 7254 7255 /* Clear pgdat state for congested, dirty or under writeback. */ 7256 static void clear_pgdat_congested(pg_data_t *pgdat) 7257 { 7258 struct lruvec *lruvec = mem_cgroup_lruvec(NULL, pgdat); 7259 7260 clear_bit(LRUVEC_NODE_CONGESTED, &lruvec->flags); 7261 clear_bit(LRUVEC_CGROUP_CONGESTED, &lruvec->flags); 7262 clear_bit(PGDAT_DIRTY, &pgdat->flags); 7263 clear_bit(PGDAT_WRITEBACK, &pgdat->flags); 7264 } 7265 7266 /* 7267 * Prepare kswapd for sleeping. This verifies that there are no processes 7268 * waiting in throttle_direct_reclaim() and that watermarks have been met. 7269 * 7270 * Returns true if kswapd is ready to sleep 7271 */ 7272 static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, 7273 int highest_zoneidx) 7274 { 7275 /* 7276 * The throttled processes are normally woken up in balance_pgdat() as 7277 * soon as allow_direct_reclaim() is true. But there is a potential 7278 * race between when kswapd checks the watermarks and a process gets 7279 * throttled. There is also a potential race if processes get 7280 * throttled, kswapd wakes, a large process exits thereby balancing the 7281 * zones, which causes kswapd to exit balance_pgdat() before reaching 7282 * the wake up checks. If kswapd is going to sleep, no process should 7283 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If 7284 * the wake up is premature, processes will wake kswapd and get 7285 * throttled again. The difference from wake ups in balance_pgdat() is 7286 * that here we are under prepare_to_wait(). 7287 */ 7288 if (waitqueue_active(&pgdat->pfmemalloc_wait)) 7289 wake_up_all(&pgdat->pfmemalloc_wait); 7290 7291 /* Hopeless node, leave it to direct reclaim */ 7292 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) 7293 return true; 7294 7295 if (pgdat_balanced(pgdat, order, highest_zoneidx)) { 7296 clear_pgdat_congested(pgdat); 7297 return true; 7298 } 7299 7300 return false; 7301 } 7302 7303 /* 7304 * kswapd shrinks a node of pages that are at or below the highest usable 7305 * zone that is currently unbalanced. 7306 * 7307 * Returns true if kswapd scanned at least the requested number of pages to 7308 * reclaim or if the lack of progress was due to pages under writeback. 7309 * This is used to determine if the scanning priority needs to be raised. 7310 */ 7311 static bool kswapd_shrink_node(pg_data_t *pgdat, 7312 struct scan_control *sc) 7313 { 7314 struct zone *zone; 7315 int z; 7316 7317 /* Reclaim a number of pages proportional to the number of zones */ 7318 sc->nr_to_reclaim = 0; 7319 for (z = 0; z <= sc->reclaim_idx; z++) { 7320 zone = pgdat->node_zones + z; 7321 if (!managed_zone(zone)) 7322 continue; 7323 7324 sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX); 7325 } 7326 7327 /* 7328 * Historically care was taken to put equal pressure on all zones but 7329 * now pressure is applied based on node LRU order. 7330 */ 7331 shrink_node(pgdat, sc); 7332 7333 /* 7334 * Fragmentation may mean that the system cannot be rebalanced for 7335 * high-order allocations. If twice the allocation size has been 7336 * reclaimed then recheck watermarks only at order-0 to prevent 7337 * excessive reclaim. Assume that a process requested a high-order 7338 * can direct reclaim/compact. 7339 */ 7340 if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order)) 7341 sc->order = 0; 7342 7343 return sc->nr_scanned >= sc->nr_to_reclaim; 7344 } 7345 7346 /* Page allocator PCP high watermark is lowered if reclaim is active. */ 7347 static inline void 7348 update_reclaim_active(pg_data_t *pgdat, int highest_zoneidx, bool active) 7349 { 7350 int i; 7351 struct zone *zone; 7352 7353 for (i = 0; i <= highest_zoneidx; i++) { 7354 zone = pgdat->node_zones + i; 7355 7356 if (!managed_zone(zone)) 7357 continue; 7358 7359 if (active) 7360 set_bit(ZONE_RECLAIM_ACTIVE, &zone->flags); 7361 else 7362 clear_bit(ZONE_RECLAIM_ACTIVE, &zone->flags); 7363 } 7364 } 7365 7366 static inline void 7367 set_reclaim_active(pg_data_t *pgdat, int highest_zoneidx) 7368 { 7369 update_reclaim_active(pgdat, highest_zoneidx, true); 7370 } 7371 7372 static inline void 7373 clear_reclaim_active(pg_data_t *pgdat, int highest_zoneidx) 7374 { 7375 update_reclaim_active(pgdat, highest_zoneidx, false); 7376 } 7377 7378 /* 7379 * For kswapd, balance_pgdat() will reclaim pages across a node from zones 7380 * that are eligible for use by the caller until at least one zone is 7381 * balanced. 7382 * 7383 * Returns the order kswapd finished reclaiming at. 7384 * 7385 * kswapd scans the zones in the highmem->normal->dma direction. It skips 7386 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 7387 * found to have free_pages <= high_wmark_pages(zone), any page in that zone 7388 * or lower is eligible for reclaim until at least one usable zone is 7389 * balanced. 7390 */ 7391 static int balance_pgdat(pg_data_t *pgdat, int order, int highest_zoneidx) 7392 { 7393 int i; 7394 unsigned long nr_soft_reclaimed; 7395 unsigned long nr_soft_scanned; 7396 unsigned long pflags; 7397 unsigned long nr_boost_reclaim; 7398 unsigned long zone_boosts[MAX_NR_ZONES] = { 0, }; 7399 bool boosted; 7400 struct zone *zone; 7401 struct scan_control sc = { 7402 .gfp_mask = GFP_KERNEL, 7403 .order = order, 7404 .may_unmap = 1, 7405 }; 7406 7407 set_task_reclaim_state(current, &sc.reclaim_state); 7408 psi_memstall_enter(&pflags); 7409 __fs_reclaim_acquire(_THIS_IP_); 7410 7411 count_vm_event(PAGEOUTRUN); 7412 7413 /* 7414 * Account for the reclaim boost. Note that the zone boost is left in 7415 * place so that parallel allocations that are near the watermark will 7416 * stall or direct reclaim until kswapd is finished. 7417 */ 7418 nr_boost_reclaim = 0; 7419 for (i = 0; i <= highest_zoneidx; i++) { 7420 zone = pgdat->node_zones + i; 7421 if (!managed_zone(zone)) 7422 continue; 7423 7424 nr_boost_reclaim += zone->watermark_boost; 7425 zone_boosts[i] = zone->watermark_boost; 7426 } 7427 boosted = nr_boost_reclaim; 7428 7429 restart: 7430 set_reclaim_active(pgdat, highest_zoneidx); 7431 sc.priority = DEF_PRIORITY; 7432 do { 7433 unsigned long nr_reclaimed = sc.nr_reclaimed; 7434 bool raise_priority = true; 7435 bool balanced; 7436 bool ret; 7437 7438 sc.reclaim_idx = highest_zoneidx; 7439 7440 /* 7441 * If the number of buffer_heads exceeds the maximum allowed 7442 * then consider reclaiming from all zones. This has a dual 7443 * purpose -- on 64-bit systems it is expected that 7444 * buffer_heads are stripped during active rotation. On 32-bit 7445 * systems, highmem pages can pin lowmem memory and shrinking 7446 * buffers can relieve lowmem pressure. Reclaim may still not 7447 * go ahead if all eligible zones for the original allocation 7448 * request are balanced to avoid excessive reclaim from kswapd. 7449 */ 7450 if (buffer_heads_over_limit) { 7451 for (i = MAX_NR_ZONES - 1; i >= 0; i--) { 7452 zone = pgdat->node_zones + i; 7453 if (!managed_zone(zone)) 7454 continue; 7455 7456 sc.reclaim_idx = i; 7457 break; 7458 } 7459 } 7460 7461 /* 7462 * If the pgdat is imbalanced then ignore boosting and preserve 7463 * the watermarks for a later time and restart. Note that the 7464 * zone watermarks will be still reset at the end of balancing 7465 * on the grounds that the normal reclaim should be enough to 7466 * re-evaluate if boosting is required when kswapd next wakes. 7467 */ 7468 balanced = pgdat_balanced(pgdat, sc.order, highest_zoneidx); 7469 if (!balanced && nr_boost_reclaim) { 7470 nr_boost_reclaim = 0; 7471 goto restart; 7472 } 7473 7474 /* 7475 * If boosting is not active then only reclaim if there are no 7476 * eligible zones. Note that sc.reclaim_idx is not used as 7477 * buffer_heads_over_limit may have adjusted it. 7478 */ 7479 if (!nr_boost_reclaim && balanced) 7480 goto out; 7481 7482 /* Limit the priority of boosting to avoid reclaim writeback */ 7483 if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2) 7484 raise_priority = false; 7485 7486 /* 7487 * Do not writeback or swap pages for boosted reclaim. The 7488 * intent is to relieve pressure not issue sub-optimal IO 7489 * from reclaim context. If no pages are reclaimed, the 7490 * reclaim will be aborted. 7491 */ 7492 sc.may_writepage = !laptop_mode && !nr_boost_reclaim; 7493 sc.may_swap = !nr_boost_reclaim; 7494 7495 /* 7496 * Do some background aging, to give pages a chance to be 7497 * referenced before reclaiming. All pages are rotated 7498 * regardless of classzone as this is about consistent aging. 7499 */ 7500 kswapd_age_node(pgdat, &sc); 7501 7502 /* 7503 * If we're getting trouble reclaiming, start doing writepage 7504 * even in laptop mode. 7505 */ 7506 if (sc.priority < DEF_PRIORITY - 2) 7507 sc.may_writepage = 1; 7508 7509 /* Call soft limit reclaim before calling shrink_node. */ 7510 sc.nr_scanned = 0; 7511 nr_soft_scanned = 0; 7512 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order, 7513 sc.gfp_mask, &nr_soft_scanned); 7514 sc.nr_reclaimed += nr_soft_reclaimed; 7515 7516 /* 7517 * There should be no need to raise the scanning priority if 7518 * enough pages are already being scanned that that high 7519 * watermark would be met at 100% efficiency. 7520 */ 7521 if (kswapd_shrink_node(pgdat, &sc)) 7522 raise_priority = false; 7523 7524 /* 7525 * If the low watermark is met there is no need for processes 7526 * to be throttled on pfmemalloc_wait as they should not be 7527 * able to safely make forward progress. Wake them 7528 */ 7529 if (waitqueue_active(&pgdat->pfmemalloc_wait) && 7530 allow_direct_reclaim(pgdat)) 7531 wake_up_all(&pgdat->pfmemalloc_wait); 7532 7533 /* Check if kswapd should be suspending */ 7534 __fs_reclaim_release(_THIS_IP_); 7535 ret = try_to_freeze(); 7536 __fs_reclaim_acquire(_THIS_IP_); 7537 if (ret || kthread_should_stop()) 7538 break; 7539 7540 /* 7541 * Raise priority if scanning rate is too low or there was no 7542 * progress in reclaiming pages 7543 */ 7544 nr_reclaimed = sc.nr_reclaimed - nr_reclaimed; 7545 nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed); 7546 7547 /* 7548 * If reclaim made no progress for a boost, stop reclaim as 7549 * IO cannot be queued and it could be an infinite loop in 7550 * extreme circumstances. 7551 */ 7552 if (nr_boost_reclaim && !nr_reclaimed) 7553 break; 7554 7555 if (raise_priority || !nr_reclaimed) 7556 sc.priority--; 7557 } while (sc.priority >= 1); 7558 7559 if (!sc.nr_reclaimed) 7560 pgdat->kswapd_failures++; 7561 7562 out: 7563 clear_reclaim_active(pgdat, highest_zoneidx); 7564 7565 /* If reclaim was boosted, account for the reclaim done in this pass */ 7566 if (boosted) { 7567 unsigned long flags; 7568 7569 for (i = 0; i <= highest_zoneidx; i++) { 7570 if (!zone_boosts[i]) 7571 continue; 7572 7573 /* Increments are under the zone lock */ 7574 zone = pgdat->node_zones + i; 7575 spin_lock_irqsave(&zone->lock, flags); 7576 zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]); 7577 spin_unlock_irqrestore(&zone->lock, flags); 7578 } 7579 7580 /* 7581 * As there is now likely space, wakeup kcompact to defragment 7582 * pageblocks. 7583 */ 7584 wakeup_kcompactd(pgdat, pageblock_order, highest_zoneidx); 7585 } 7586 7587 snapshot_refaults(NULL, pgdat); 7588 __fs_reclaim_release(_THIS_IP_); 7589 psi_memstall_leave(&pflags); 7590 set_task_reclaim_state(current, NULL); 7591 7592 /* 7593 * Return the order kswapd stopped reclaiming at as 7594 * prepare_kswapd_sleep() takes it into account. If another caller 7595 * entered the allocator slow path while kswapd was awake, order will 7596 * remain at the higher level. 7597 */ 7598 return sc.order; 7599 } 7600 7601 /* 7602 * The pgdat->kswapd_highest_zoneidx is used to pass the highest zone index to 7603 * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is 7604 * not a valid index then either kswapd runs for first time or kswapd couldn't 7605 * sleep after previous reclaim attempt (node is still unbalanced). In that 7606 * case return the zone index of the previous kswapd reclaim cycle. 7607 */ 7608 static enum zone_type kswapd_highest_zoneidx(pg_data_t *pgdat, 7609 enum zone_type prev_highest_zoneidx) 7610 { 7611 enum zone_type curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx); 7612 7613 return curr_idx == MAX_NR_ZONES ? prev_highest_zoneidx : curr_idx; 7614 } 7615 7616 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order, 7617 unsigned int highest_zoneidx) 7618 { 7619 long remaining = 0; 7620 DEFINE_WAIT(wait); 7621 7622 if (freezing(current) || kthread_should_stop()) 7623 return; 7624 7625 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 7626 7627 /* 7628 * Try to sleep for a short interval. Note that kcompactd will only be 7629 * woken if it is possible to sleep for a short interval. This is 7630 * deliberate on the assumption that if reclaim cannot keep an 7631 * eligible zone balanced that it's also unlikely that compaction will 7632 * succeed. 7633 */ 7634 if (prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) { 7635 /* 7636 * Compaction records what page blocks it recently failed to 7637 * isolate pages from and skips them in the future scanning. 7638 * When kswapd is going to sleep, it is reasonable to assume 7639 * that pages and compaction may succeed so reset the cache. 7640 */ 7641 reset_isolation_suitable(pgdat); 7642 7643 /* 7644 * We have freed the memory, now we should compact it to make 7645 * allocation of the requested order possible. 7646 */ 7647 wakeup_kcompactd(pgdat, alloc_order, highest_zoneidx); 7648 7649 remaining = schedule_timeout(HZ/10); 7650 7651 /* 7652 * If woken prematurely then reset kswapd_highest_zoneidx and 7653 * order. The values will either be from a wakeup request or 7654 * the previous request that slept prematurely. 7655 */ 7656 if (remaining) { 7657 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, 7658 kswapd_highest_zoneidx(pgdat, 7659 highest_zoneidx)); 7660 7661 if (READ_ONCE(pgdat->kswapd_order) < reclaim_order) 7662 WRITE_ONCE(pgdat->kswapd_order, reclaim_order); 7663 } 7664 7665 finish_wait(&pgdat->kswapd_wait, &wait); 7666 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 7667 } 7668 7669 /* 7670 * After a short sleep, check if it was a premature sleep. If not, then 7671 * go fully to sleep until explicitly woken up. 7672 */ 7673 if (!remaining && 7674 prepare_kswapd_sleep(pgdat, reclaim_order, highest_zoneidx)) { 7675 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 7676 7677 /* 7678 * vmstat counters are not perfectly accurate and the estimated 7679 * value for counters such as NR_FREE_PAGES can deviate from the 7680 * true value by nr_online_cpus * threshold. To avoid the zone 7681 * watermarks being breached while under pressure, we reduce the 7682 * per-cpu vmstat threshold while kswapd is awake and restore 7683 * them before going back to sleep. 7684 */ 7685 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 7686 7687 if (!kthread_should_stop()) 7688 schedule(); 7689 7690 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 7691 } else { 7692 if (remaining) 7693 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 7694 else 7695 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 7696 } 7697 finish_wait(&pgdat->kswapd_wait, &wait); 7698 } 7699 7700 /* 7701 * The background pageout daemon, started as a kernel thread 7702 * from the init process. 7703 * 7704 * This basically trickles out pages so that we have _some_ 7705 * free memory available even if there is no other activity 7706 * that frees anything up. This is needed for things like routing 7707 * etc, where we otherwise might have all activity going on in 7708 * asynchronous contexts that cannot page things out. 7709 * 7710 * If there are applications that are active memory-allocators 7711 * (most normal use), this basically shouldn't matter. 7712 */ 7713 static int kswapd(void *p) 7714 { 7715 unsigned int alloc_order, reclaim_order; 7716 unsigned int highest_zoneidx = MAX_NR_ZONES - 1; 7717 pg_data_t *pgdat = (pg_data_t *)p; 7718 struct task_struct *tsk = current; 7719 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 7720 7721 if (!cpumask_empty(cpumask)) 7722 set_cpus_allowed_ptr(tsk, cpumask); 7723 7724 /* 7725 * Tell the memory management that we're a "memory allocator", 7726 * and that if we need more memory we should get access to it 7727 * regardless (see "__alloc_pages()"). "kswapd" should 7728 * never get caught in the normal page freeing logic. 7729 * 7730 * (Kswapd normally doesn't need memory anyway, but sometimes 7731 * you need a small amount of memory in order to be able to 7732 * page out something else, and this flag essentially protects 7733 * us from recursively trying to free more memory as we're 7734 * trying to free the first piece of memory in the first place). 7735 */ 7736 tsk->flags |= PF_MEMALLOC | PF_KSWAPD; 7737 set_freezable(); 7738 7739 WRITE_ONCE(pgdat->kswapd_order, 0); 7740 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES); 7741 atomic_set(&pgdat->nr_writeback_throttled, 0); 7742 for ( ; ; ) { 7743 bool ret; 7744 7745 alloc_order = reclaim_order = READ_ONCE(pgdat->kswapd_order); 7746 highest_zoneidx = kswapd_highest_zoneidx(pgdat, 7747 highest_zoneidx); 7748 7749 kswapd_try_sleep: 7750 kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order, 7751 highest_zoneidx); 7752 7753 /* Read the new order and highest_zoneidx */ 7754 alloc_order = READ_ONCE(pgdat->kswapd_order); 7755 highest_zoneidx = kswapd_highest_zoneidx(pgdat, 7756 highest_zoneidx); 7757 WRITE_ONCE(pgdat->kswapd_order, 0); 7758 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, MAX_NR_ZONES); 7759 7760 ret = try_to_freeze(); 7761 if (kthread_should_stop()) 7762 break; 7763 7764 /* 7765 * We can speed up thawing tasks if we don't call balance_pgdat 7766 * after returning from the refrigerator 7767 */ 7768 if (ret) 7769 continue; 7770 7771 /* 7772 * Reclaim begins at the requested order but if a high-order 7773 * reclaim fails then kswapd falls back to reclaiming for 7774 * order-0. If that happens, kswapd will consider sleeping 7775 * for the order it finished reclaiming at (reclaim_order) 7776 * but kcompactd is woken to compact for the original 7777 * request (alloc_order). 7778 */ 7779 trace_mm_vmscan_kswapd_wake(pgdat->node_id, highest_zoneidx, 7780 alloc_order); 7781 reclaim_order = balance_pgdat(pgdat, alloc_order, 7782 highest_zoneidx); 7783 if (reclaim_order < alloc_order) 7784 goto kswapd_try_sleep; 7785 } 7786 7787 tsk->flags &= ~(PF_MEMALLOC | PF_KSWAPD); 7788 7789 return 0; 7790 } 7791 7792 /* 7793 * A zone is low on free memory or too fragmented for high-order memory. If 7794 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's 7795 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim 7796 * has failed or is not needed, still wake up kcompactd if only compaction is 7797 * needed. 7798 */ 7799 void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order, 7800 enum zone_type highest_zoneidx) 7801 { 7802 pg_data_t *pgdat; 7803 enum zone_type curr_idx; 7804 7805 if (!managed_zone(zone)) 7806 return; 7807 7808 if (!cpuset_zone_allowed(zone, gfp_flags)) 7809 return; 7810 7811 pgdat = zone->zone_pgdat; 7812 curr_idx = READ_ONCE(pgdat->kswapd_highest_zoneidx); 7813 7814 if (curr_idx == MAX_NR_ZONES || curr_idx < highest_zoneidx) 7815 WRITE_ONCE(pgdat->kswapd_highest_zoneidx, highest_zoneidx); 7816 7817 if (READ_ONCE(pgdat->kswapd_order) < order) 7818 WRITE_ONCE(pgdat->kswapd_order, order); 7819 7820 if (!waitqueue_active(&pgdat->kswapd_wait)) 7821 return; 7822 7823 /* Hopeless node, leave it to direct reclaim if possible */ 7824 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES || 7825 (pgdat_balanced(pgdat, order, highest_zoneidx) && 7826 !pgdat_watermark_boosted(pgdat, highest_zoneidx))) { 7827 /* 7828 * There may be plenty of free memory available, but it's too 7829 * fragmented for high-order allocations. Wake up kcompactd 7830 * and rely on compaction_suitable() to determine if it's 7831 * needed. If it fails, it will defer subsequent attempts to 7832 * ratelimit its work. 7833 */ 7834 if (!(gfp_flags & __GFP_DIRECT_RECLAIM)) 7835 wakeup_kcompactd(pgdat, order, highest_zoneidx); 7836 return; 7837 } 7838 7839 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, highest_zoneidx, order, 7840 gfp_flags); 7841 wake_up_interruptible(&pgdat->kswapd_wait); 7842 } 7843 7844 #ifdef CONFIG_HIBERNATION 7845 /* 7846 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 7847 * freed pages. 7848 * 7849 * Rather than trying to age LRUs the aim is to preserve the overall 7850 * LRU order by reclaiming preferentially 7851 * inactive > active > active referenced > active mapped 7852 */ 7853 unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 7854 { 7855 struct scan_control sc = { 7856 .nr_to_reclaim = nr_to_reclaim, 7857 .gfp_mask = GFP_HIGHUSER_MOVABLE, 7858 .reclaim_idx = MAX_NR_ZONES - 1, 7859 .priority = DEF_PRIORITY, 7860 .may_writepage = 1, 7861 .may_unmap = 1, 7862 .may_swap = 1, 7863 .hibernation_mode = 1, 7864 }; 7865 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 7866 unsigned long nr_reclaimed; 7867 unsigned int noreclaim_flag; 7868 7869 fs_reclaim_acquire(sc.gfp_mask); 7870 noreclaim_flag = memalloc_noreclaim_save(); 7871 set_task_reclaim_state(current, &sc.reclaim_state); 7872 7873 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 7874 7875 set_task_reclaim_state(current, NULL); 7876 memalloc_noreclaim_restore(noreclaim_flag); 7877 fs_reclaim_release(sc.gfp_mask); 7878 7879 return nr_reclaimed; 7880 } 7881 #endif /* CONFIG_HIBERNATION */ 7882 7883 /* 7884 * This kswapd start function will be called by init and node-hot-add. 7885 */ 7886 void __meminit kswapd_run(int nid) 7887 { 7888 pg_data_t *pgdat = NODE_DATA(nid); 7889 7890 pgdat_kswapd_lock(pgdat); 7891 if (!pgdat->kswapd) { 7892 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 7893 if (IS_ERR(pgdat->kswapd)) { 7894 /* failure at boot is fatal */ 7895 BUG_ON(system_state < SYSTEM_RUNNING); 7896 pr_err("Failed to start kswapd on node %d\n", nid); 7897 pgdat->kswapd = NULL; 7898 } 7899 } 7900 pgdat_kswapd_unlock(pgdat); 7901 } 7902 7903 /* 7904 * Called by memory hotplug when all memory in a node is offlined. Caller must 7905 * be holding mem_hotplug_begin/done(). 7906 */ 7907 void __meminit kswapd_stop(int nid) 7908 { 7909 pg_data_t *pgdat = NODE_DATA(nid); 7910 struct task_struct *kswapd; 7911 7912 pgdat_kswapd_lock(pgdat); 7913 kswapd = pgdat->kswapd; 7914 if (kswapd) { 7915 kthread_stop(kswapd); 7916 pgdat->kswapd = NULL; 7917 } 7918 pgdat_kswapd_unlock(pgdat); 7919 } 7920 7921 static int __init kswapd_init(void) 7922 { 7923 int nid; 7924 7925 swap_setup(); 7926 for_each_node_state(nid, N_MEMORY) 7927 kswapd_run(nid); 7928 return 0; 7929 } 7930 7931 module_init(kswapd_init) 7932 7933 #ifdef CONFIG_NUMA 7934 /* 7935 * Node reclaim mode 7936 * 7937 * If non-zero call node_reclaim when the number of free pages falls below 7938 * the watermarks. 7939 */ 7940 int node_reclaim_mode __read_mostly; 7941 7942 /* 7943 * Priority for NODE_RECLAIM. This determines the fraction of pages 7944 * of a node considered for each zone_reclaim. 4 scans 1/16th of 7945 * a zone. 7946 */ 7947 #define NODE_RECLAIM_PRIORITY 4 7948 7949 /* 7950 * Percentage of pages in a zone that must be unmapped for node_reclaim to 7951 * occur. 7952 */ 7953 int sysctl_min_unmapped_ratio = 1; 7954 7955 /* 7956 * If the number of slab pages in a zone grows beyond this percentage then 7957 * slab reclaim needs to occur. 7958 */ 7959 int sysctl_min_slab_ratio = 5; 7960 7961 static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat) 7962 { 7963 unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED); 7964 unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) + 7965 node_page_state(pgdat, NR_ACTIVE_FILE); 7966 7967 /* 7968 * It's possible for there to be more file mapped pages than 7969 * accounted for by the pages on the file LRU lists because 7970 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 7971 */ 7972 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 7973 } 7974 7975 /* Work out how many page cache pages we can reclaim in this reclaim_mode */ 7976 static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat) 7977 { 7978 unsigned long nr_pagecache_reclaimable; 7979 unsigned long delta = 0; 7980 7981 /* 7982 * If RECLAIM_UNMAP is set, then all file pages are considered 7983 * potentially reclaimable. Otherwise, we have to worry about 7984 * pages like swapcache and node_unmapped_file_pages() provides 7985 * a better estimate 7986 */ 7987 if (node_reclaim_mode & RECLAIM_UNMAP) 7988 nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES); 7989 else 7990 nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat); 7991 7992 /* If we can't clean pages, remove dirty pages from consideration */ 7993 if (!(node_reclaim_mode & RECLAIM_WRITE)) 7994 delta += node_page_state(pgdat, NR_FILE_DIRTY); 7995 7996 /* Watch for any possible underflows due to delta */ 7997 if (unlikely(delta > nr_pagecache_reclaimable)) 7998 delta = nr_pagecache_reclaimable; 7999 8000 return nr_pagecache_reclaimable - delta; 8001 } 8002 8003 /* 8004 * Try to free up some pages from this node through reclaim. 8005 */ 8006 static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) 8007 { 8008 /* Minimum pages needed in order to stay on node */ 8009 const unsigned long nr_pages = 1 << order; 8010 struct task_struct *p = current; 8011 unsigned int noreclaim_flag; 8012 struct scan_control sc = { 8013 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), 8014 .gfp_mask = current_gfp_context(gfp_mask), 8015 .order = order, 8016 .priority = NODE_RECLAIM_PRIORITY, 8017 .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE), 8018 .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP), 8019 .may_swap = 1, 8020 .reclaim_idx = gfp_zone(gfp_mask), 8021 }; 8022 unsigned long pflags; 8023 8024 trace_mm_vmscan_node_reclaim_begin(pgdat->node_id, order, 8025 sc.gfp_mask); 8026 8027 cond_resched(); 8028 psi_memstall_enter(&pflags); 8029 fs_reclaim_acquire(sc.gfp_mask); 8030 /* 8031 * We need to be able to allocate from the reserves for RECLAIM_UNMAP 8032 */ 8033 noreclaim_flag = memalloc_noreclaim_save(); 8034 set_task_reclaim_state(p, &sc.reclaim_state); 8035 8036 if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages || 8037 node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) { 8038 /* 8039 * Free memory by calling shrink node with increasing 8040 * priorities until we have enough memory freed. 8041 */ 8042 do { 8043 shrink_node(pgdat, &sc); 8044 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); 8045 } 8046 8047 set_task_reclaim_state(p, NULL); 8048 memalloc_noreclaim_restore(noreclaim_flag); 8049 fs_reclaim_release(sc.gfp_mask); 8050 psi_memstall_leave(&pflags); 8051 8052 trace_mm_vmscan_node_reclaim_end(sc.nr_reclaimed); 8053 8054 return sc.nr_reclaimed >= nr_pages; 8055 } 8056 8057 int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) 8058 { 8059 int ret; 8060 8061 /* 8062 * Node reclaim reclaims unmapped file backed pages and 8063 * slab pages if we are over the defined limits. 8064 * 8065 * A small portion of unmapped file backed pages is needed for 8066 * file I/O otherwise pages read by file I/O will be immediately 8067 * thrown out if the node is overallocated. So we do not reclaim 8068 * if less than a specified percentage of the node is used by 8069 * unmapped file backed pages. 8070 */ 8071 if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages && 8072 node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) <= 8073 pgdat->min_slab_pages) 8074 return NODE_RECLAIM_FULL; 8075 8076 /* 8077 * Do not scan if the allocation should not be delayed. 8078 */ 8079 if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC)) 8080 return NODE_RECLAIM_NOSCAN; 8081 8082 /* 8083 * Only run node reclaim on the local node or on nodes that do not 8084 * have associated processors. This will favor the local processor 8085 * over remote processors and spread off node memory allocations 8086 * as wide as possible. 8087 */ 8088 if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id()) 8089 return NODE_RECLAIM_NOSCAN; 8090 8091 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags)) 8092 return NODE_RECLAIM_NOSCAN; 8093 8094 ret = __node_reclaim(pgdat, gfp_mask, order); 8095 clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags); 8096 8097 if (!ret) 8098 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 8099 8100 return ret; 8101 } 8102 #endif 8103 8104 /** 8105 * check_move_unevictable_folios - Move evictable folios to appropriate zone 8106 * lru list 8107 * @fbatch: Batch of lru folios to check. 8108 * 8109 * Checks folios for evictability, if an evictable folio is in the unevictable 8110 * lru list, moves it to the appropriate evictable lru list. This function 8111 * should be only used for lru folios. 8112 */ 8113 void check_move_unevictable_folios(struct folio_batch *fbatch) 8114 { 8115 struct lruvec *lruvec = NULL; 8116 int pgscanned = 0; 8117 int pgrescued = 0; 8118 int i; 8119 8120 for (i = 0; i < fbatch->nr; i++) { 8121 struct folio *folio = fbatch->folios[i]; 8122 int nr_pages = folio_nr_pages(folio); 8123 8124 pgscanned += nr_pages; 8125 8126 /* block memcg migration while the folio moves between lrus */ 8127 if (!folio_test_clear_lru(folio)) 8128 continue; 8129 8130 lruvec = folio_lruvec_relock_irq(folio, lruvec); 8131 if (folio_evictable(folio) && folio_test_unevictable(folio)) { 8132 lruvec_del_folio(lruvec, folio); 8133 folio_clear_unevictable(folio); 8134 lruvec_add_folio(lruvec, folio); 8135 pgrescued += nr_pages; 8136 } 8137 folio_set_lru(folio); 8138 } 8139 8140 if (lruvec) { 8141 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); 8142 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); 8143 unlock_page_lruvec_irq(lruvec); 8144 } else if (pgscanned) { 8145 count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); 8146 } 8147 } 8148 EXPORT_SYMBOL_GPL(check_move_unevictable_folios);