1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/mm/vmscan.c 4 * 5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 6 * 7 * Swap reorganised 29.12.95, Stephen Tweedie. 8 * kswapd added: 7.1.96 sct 9 * Removed kswapd_ctl limits, and swap out as many pages as needed 10 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 11 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). 12 * Multiqueue VM started 5.8.00, Rik van Riel. 13 */ 14 15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 16 17 #include <linux/mm.h> 18 #include <linux/sched/mm.h> 19 #include <linux/module.h> 20 #include <linux/gfp.h> 21 #include <linux/kernel_stat.h> 22 #include <linux/swap.h> 23 #include <linux/pagemap.h> 24 #include <linux/init.h> 25 #include <linux/highmem.h> 26 #include <linux/vmpressure.h> 27 #include <linux/vmstat.h> 28 #include <linux/file.h> 29 #include <linux/writeback.h> 30 #include <linux/blkdev.h> 31 #include <linux/buffer_head.h> /* for try_to_release_page(), 32 buffer_heads_over_limit */ 33 #include <linux/mm_inline.h> 34 #include <linux/backing-dev.h> 35 #include <linux/rmap.h> 36 #include <linux/topology.h> 37 #include <linux/cpu.h> 38 #include <linux/cpuset.h> 39 #include <linux/compaction.h> 40 #include <linux/notifier.h> 41 #include <linux/rwsem.h> 42 #include <linux/delay.h> 43 #include <linux/kthread.h> 44 #include <linux/freezer.h> 45 #include <linux/memcontrol.h> 46 #include <linux/delayacct.h> 47 #include <linux/sysctl.h> 48 #include <linux/oom.h> 49 #include <linux/pagevec.h> 50 #include <linux/prefetch.h> 51 #include <linux/printk.h> 52 #include <linux/dax.h> 53 #include <linux/psi.h> 54 55 #include <asm/tlbflush.h> 56 #include <asm/div64.h> 57 58 #include <linux/swapops.h> 59 #include <linux/balloon_compaction.h> 60 61 #include "internal.h" 62 63 #define CREATE_TRACE_POINTS 64 #include <trace/events/vmscan.h> 65 66 struct scan_control { 67 /* How many pages shrink_list() should reclaim */ 68 unsigned long nr_to_reclaim; 69 70 /* 71 * Nodemask of nodes allowed by the caller. If NULL, all nodes 72 * are scanned. 73 */ 74 nodemask_t *nodemask; 75 76 /* 77 * The memory cgroup that hit its limit and as a result is the 78 * primary target of this reclaim invocation. 79 */ 80 struct mem_cgroup *target_mem_cgroup; 81 82 /* Writepage batching in laptop mode; RECLAIM_WRITE */ 83 unsigned int may_writepage:1; 84 85 /* Can mapped pages be reclaimed? */ 86 unsigned int may_unmap:1; 87 88 /* Can pages be swapped as part of reclaim? */ 89 unsigned int may_swap:1; 90 91 /* e.g. boosted watermark reclaim leaves slabs alone */ 92 unsigned int may_shrinkslab:1; 93 94 /* 95 * Cgroups are not reclaimed below their configured memory.low, 96 * unless we threaten to OOM. If any cgroups are skipped due to 97 * memory.low and nothing was reclaimed, go back for memory.low. 98 */ 99 unsigned int memcg_low_reclaim:1; 100 unsigned int memcg_low_skipped:1; 101 102 unsigned int hibernation_mode:1; 103 104 /* One of the zones is ready for compaction */ 105 unsigned int compaction_ready:1; 106 107 /* Allocation order */ 108 s8 order; 109 110 /* Scan (total_size >> priority) pages at once */ 111 s8 priority; 112 113 /* The highest zone to isolate pages for reclaim from */ 114 s8 reclaim_idx; 115 116 /* This context's GFP mask */ 117 gfp_t gfp_mask; 118 119 /* Incremented by the number of inactive pages that were scanned */ 120 unsigned long nr_scanned; 121 122 /* Number of pages freed so far during a call to shrink_zones() */ 123 unsigned long nr_reclaimed; 124 125 struct { 126 unsigned int dirty; 127 unsigned int unqueued_dirty; 128 unsigned int congested; 129 unsigned int writeback; 130 unsigned int immediate; 131 unsigned int file_taken; 132 unsigned int taken; 133 } nr; 134 }; 135 136 #ifdef ARCH_HAS_PREFETCH 137 #define prefetch_prev_lru_page(_page, _base, _field) \ 138 do { \ 139 if ((_page)->lru.prev != _base) { \ 140 struct page *prev; \ 141 \ 142 prev = lru_to_page(&(_page->lru)); \ 143 prefetch(&prev->_field); \ 144 } \ 145 } while (0) 146 #else 147 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 148 #endif 149 150 #ifdef ARCH_HAS_PREFETCHW 151 #define prefetchw_prev_lru_page(_page, _base, _field) \ 152 do { \ 153 if ((_page)->lru.prev != _base) { \ 154 struct page *prev; \ 155 \ 156 prev = lru_to_page(&(_page->lru)); \ 157 prefetchw(&prev->_field); \ 158 } \ 159 } while (0) 160 #else 161 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 162 #endif 163 164 /* 165 * From 0 .. 100. Higher means more swappy. 166 */ 167 int vm_swappiness = 60; 168 /* 169 * The total number of pages which are beyond the high watermark within all 170 * zones. 171 */ 172 unsigned long vm_total_pages; 173 174 static LIST_HEAD(shrinker_list); 175 static DECLARE_RWSEM(shrinker_rwsem); 176 177 #ifdef CONFIG_MEMCG_KMEM 178 179 /* 180 * We allow subsystems to populate their shrinker-related 181 * LRU lists before register_shrinker_prepared() is called 182 * for the shrinker, since we don't want to impose 183 * restrictions on their internal registration order. 184 * In this case shrink_slab_memcg() may find corresponding 185 * bit is set in the shrinkers map. 186 * 187 * This value is used by the function to detect registering 188 * shrinkers and to skip do_shrink_slab() calls for them. 189 */ 190 #define SHRINKER_REGISTERING ((struct shrinker *)~0UL) 191 192 static DEFINE_IDR(shrinker_idr); 193 static int shrinker_nr_max; 194 195 static int prealloc_memcg_shrinker(struct shrinker *shrinker) 196 { 197 int id, ret = -ENOMEM; 198 199 down_write(&shrinker_rwsem); 200 /* This may call shrinker, so it must use down_read_trylock() */ 201 id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); 202 if (id < 0) 203 goto unlock; 204 205 if (id >= shrinker_nr_max) { 206 if (memcg_expand_shrinker_maps(id)) { 207 idr_remove(&shrinker_idr, id); 208 goto unlock; 209 } 210 211 shrinker_nr_max = id + 1; 212 } 213 shrinker->id = id; 214 ret = 0; 215 unlock: 216 up_write(&shrinker_rwsem); 217 return ret; 218 } 219 220 static void unregister_memcg_shrinker(struct shrinker *shrinker) 221 { 222 int id = shrinker->id; 223 224 BUG_ON(id < 0); 225 226 down_write(&shrinker_rwsem); 227 idr_remove(&shrinker_idr, id); 228 up_write(&shrinker_rwsem); 229 } 230 #else /* CONFIG_MEMCG_KMEM */ 231 static int prealloc_memcg_shrinker(struct shrinker *shrinker) 232 { 233 return 0; 234 } 235 236 static void unregister_memcg_shrinker(struct shrinker *shrinker) 237 { 238 } 239 #endif /* CONFIG_MEMCG_KMEM */ 240 241 #ifdef CONFIG_MEMCG 242 static bool global_reclaim(struct scan_control *sc) 243 { 244 return !sc->target_mem_cgroup; 245 } 246 247 /** 248 * sane_reclaim - is the usual dirty throttling mechanism operational? 249 * @sc: scan_control in question 250 * 251 * The normal page dirty throttling mechanism in balance_dirty_pages() is 252 * completely broken with the legacy memcg and direct stalling in 253 * shrink_page_list() is used for throttling instead, which lacks all the 254 * niceties such as fairness, adaptive pausing, bandwidth proportional 255 * allocation and configurability. 256 * 257 * This function tests whether the vmscan currently in progress can assume 258 * that the normal dirty throttling mechanism is operational. 259 */ 260 static bool sane_reclaim(struct scan_control *sc) 261 { 262 struct mem_cgroup *memcg = sc->target_mem_cgroup; 263 264 if (!memcg) 265 return true; 266 #ifdef CONFIG_CGROUP_WRITEBACK 267 if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) 268 return true; 269 #endif 270 return false; 271 } 272 273 static void set_memcg_congestion(pg_data_t *pgdat, 274 struct mem_cgroup *memcg, 275 bool congested) 276 { 277 struct mem_cgroup_per_node *mn; 278 279 if (!memcg) 280 return; 281 282 mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id); 283 WRITE_ONCE(mn->congested, congested); 284 } 285 286 static bool memcg_congested(pg_data_t *pgdat, 287 struct mem_cgroup *memcg) 288 { 289 struct mem_cgroup_per_node *mn; 290 291 mn = mem_cgroup_nodeinfo(memcg, pgdat->node_id); 292 return READ_ONCE(mn->congested); 293 294 } 295 #else 296 static bool global_reclaim(struct scan_control *sc) 297 { 298 return true; 299 } 300 301 static bool sane_reclaim(struct scan_control *sc) 302 { 303 return true; 304 } 305 306 static inline void set_memcg_congestion(struct pglist_data *pgdat, 307 struct mem_cgroup *memcg, bool congested) 308 { 309 } 310 311 static inline bool memcg_congested(struct pglist_data *pgdat, 312 struct mem_cgroup *memcg) 313 { 314 return false; 315 316 } 317 #endif 318 319 /* 320 * This misses isolated pages which are not accounted for to save counters. 321 * As the data only determines if reclaim or compaction continues, it is 322 * not expected that isolated pages will be a dominating factor. 323 */ 324 unsigned long zone_reclaimable_pages(struct zone *zone) 325 { 326 unsigned long nr; 327 328 nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) + 329 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE); 330 if (get_nr_swap_pages() > 0) 331 nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) + 332 zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON); 333 334 return nr; 335 } 336 337 /** 338 * lruvec_lru_size - Returns the number of pages on the given LRU list. 339 * @lruvec: lru vector 340 * @lru: lru to use 341 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list) 342 */ 343 unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx) 344 { 345 unsigned long lru_size; 346 int zid; 347 348 if (!mem_cgroup_disabled()) 349 lru_size = mem_cgroup_get_lru_size(lruvec, lru); 350 else 351 lru_size = node_page_state(lruvec_pgdat(lruvec), NR_LRU_BASE + lru); 352 353 for (zid = zone_idx + 1; zid < MAX_NR_ZONES; zid++) { 354 struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid]; 355 unsigned long size; 356 357 if (!managed_zone(zone)) 358 continue; 359 360 if (!mem_cgroup_disabled()) 361 size = mem_cgroup_get_zone_lru_size(lruvec, lru, zid); 362 else 363 size = zone_page_state(&lruvec_pgdat(lruvec)->node_zones[zid], 364 NR_ZONE_LRU_BASE + lru); 365 lru_size -= min(size, lru_size); 366 } 367 368 return lru_size; 369 370 } 371 372 /* 373 * Add a shrinker callback to be called from the vm. 374 */ 375 int prealloc_shrinker(struct shrinker *shrinker) 376 { 377 unsigned int size = sizeof(*shrinker->nr_deferred); 378 379 if (shrinker->flags & SHRINKER_NUMA_AWARE) 380 size *= nr_node_ids; 381 382 shrinker->nr_deferred = kzalloc(size, GFP_KERNEL); 383 if (!shrinker->nr_deferred) 384 return -ENOMEM; 385 386 if (shrinker->flags & SHRINKER_MEMCG_AWARE) { 387 if (prealloc_memcg_shrinker(shrinker)) 388 goto free_deferred; 389 } 390 391 return 0; 392 393 free_deferred: 394 kfree(shrinker->nr_deferred); 395 shrinker->nr_deferred = NULL; 396 return -ENOMEM; 397 } 398 399 void free_prealloced_shrinker(struct shrinker *shrinker) 400 { 401 if (!shrinker->nr_deferred) 402 return; 403 404 if (shrinker->flags & SHRINKER_MEMCG_AWARE) 405 unregister_memcg_shrinker(shrinker); 406 407 kfree(shrinker->nr_deferred); 408 shrinker->nr_deferred = NULL; 409 } 410 411 void register_shrinker_prepared(struct shrinker *shrinker) 412 { 413 down_write(&shrinker_rwsem); 414 list_add_tail(&shrinker->list, &shrinker_list); 415 #ifdef CONFIG_MEMCG_KMEM 416 if (shrinker->flags & SHRINKER_MEMCG_AWARE) 417 idr_replace(&shrinker_idr, shrinker, shrinker->id); 418 #endif 419 up_write(&shrinker_rwsem); 420 } 421 422 int register_shrinker(struct shrinker *shrinker) 423 { 424 int err = prealloc_shrinker(shrinker); 425 426 if (err) 427 return err; 428 register_shrinker_prepared(shrinker); 429 return 0; 430 } 431 EXPORT_SYMBOL(register_shrinker); 432 433 /* 434 * Remove one 435 */ 436 void unregister_shrinker(struct shrinker *shrinker) 437 { 438 if (!shrinker->nr_deferred) 439 return; 440 if (shrinker->flags & SHRINKER_MEMCG_AWARE) 441 unregister_memcg_shrinker(shrinker); 442 down_write(&shrinker_rwsem); 443 list_del(&shrinker->list); 444 up_write(&shrinker_rwsem); 445 kfree(shrinker->nr_deferred); 446 shrinker->nr_deferred = NULL; 447 } 448 EXPORT_SYMBOL(unregister_shrinker); 449 450 #define SHRINK_BATCH 128 451 452 static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, 453 struct shrinker *shrinker, int priority) 454 { 455 unsigned long freed = 0; 456 unsigned long long delta; 457 long total_scan; 458 long freeable; 459 long nr; 460 long new_nr; 461 int nid = shrinkctl->nid; 462 long batch_size = shrinker->batch ? shrinker->batch 463 : SHRINK_BATCH; 464 long scanned = 0, next_deferred; 465 466 if (!(shrinker->flags & SHRINKER_NUMA_AWARE)) 467 nid = 0; 468 469 freeable = shrinker->count_objects(shrinker, shrinkctl); 470 if (freeable == 0 || freeable == SHRINK_EMPTY) 471 return freeable; 472 473 /* 474 * copy the current shrinker scan count into a local variable 475 * and zero it so that other concurrent shrinker invocations 476 * don't also do this scanning work. 477 */ 478 nr = atomic_long_xchg(&shrinker->nr_deferred[nid], 0); 479 480 total_scan = nr; 481 if (shrinker->seeks) { 482 delta = freeable >> priority; 483 delta *= 4; 484 do_div(delta, shrinker->seeks); 485 } else { 486 /* 487 * These objects don't require any IO to create. Trim 488 * them aggressively under memory pressure to keep 489 * them from causing refetches in the IO caches. 490 */ 491 delta = freeable / 2; 492 } 493 494 total_scan += delta; 495 if (total_scan < 0) { 496 pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n", 497 shrinker->scan_objects, total_scan); 498 total_scan = freeable; 499 next_deferred = nr; 500 } else 501 next_deferred = total_scan; 502 503 /* 504 * We need to avoid excessive windup on filesystem shrinkers 505 * due to large numbers of GFP_NOFS allocations causing the 506 * shrinkers to return -1 all the time. This results in a large 507 * nr being built up so when a shrink that can do some work 508 * comes along it empties the entire cache due to nr >>> 509 * freeable. This is bad for sustaining a working set in 510 * memory. 511 * 512 * Hence only allow the shrinker to scan the entire cache when 513 * a large delta change is calculated directly. 514 */ 515 if (delta < freeable / 4) 516 total_scan = min(total_scan, freeable / 2); 517 518 /* 519 * Avoid risking looping forever due to too large nr value: 520 * never try to free more than twice the estimate number of 521 * freeable entries. 522 */ 523 if (total_scan > freeable * 2) 524 total_scan = freeable * 2; 525 526 trace_mm_shrink_slab_start(shrinker, shrinkctl, nr, 527 freeable, delta, total_scan, priority); 528 529 /* 530 * Normally, we should not scan less than batch_size objects in one 531 * pass to avoid too frequent shrinker calls, but if the slab has less 532 * than batch_size objects in total and we are really tight on memory, 533 * we will try to reclaim all available objects, otherwise we can end 534 * up failing allocations although there are plenty of reclaimable 535 * objects spread over several slabs with usage less than the 536 * batch_size. 537 * 538 * We detect the "tight on memory" situations by looking at the total 539 * number of objects we want to scan (total_scan). If it is greater 540 * than the total number of objects on slab (freeable), we must be 541 * scanning at high prio and therefore should try to reclaim as much as 542 * possible. 543 */ 544 while (total_scan >= batch_size || 545 total_scan >= freeable) { 546 unsigned long ret; 547 unsigned long nr_to_scan = min(batch_size, total_scan); 548 549 shrinkctl->nr_to_scan = nr_to_scan; 550 shrinkctl->nr_scanned = nr_to_scan; 551 ret = shrinker->scan_objects(shrinker, shrinkctl); 552 if (ret == SHRINK_STOP) 553 break; 554 freed += ret; 555 556 count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned); 557 total_scan -= shrinkctl->nr_scanned; 558 scanned += shrinkctl->nr_scanned; 559 560 cond_resched(); 561 } 562 563 if (next_deferred >= scanned) 564 next_deferred -= scanned; 565 else 566 next_deferred = 0; 567 /* 568 * move the unused scan count back into the shrinker in a 569 * manner that handles concurrent updates. If we exhausted the 570 * scan, there is no need to do an update. 571 */ 572 if (next_deferred > 0) 573 new_nr = atomic_long_add_return(next_deferred, 574 &shrinker->nr_deferred[nid]); 575 else 576 new_nr = atomic_long_read(&shrinker->nr_deferred[nid]); 577 578 trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan); 579 return freed; 580 } 581 582 #ifdef CONFIG_MEMCG_KMEM 583 static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, 584 struct mem_cgroup *memcg, int priority) 585 { 586 struct memcg_shrinker_map *map; 587 unsigned long ret, freed = 0; 588 int i; 589 590 if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)) 591 return 0; 592 593 if (!down_read_trylock(&shrinker_rwsem)) 594 return 0; 595 596 map = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_map, 597 true); 598 if (unlikely(!map)) 599 goto unlock; 600 601 for_each_set_bit(i, map->map, shrinker_nr_max) { 602 struct shrink_control sc = { 603 .gfp_mask = gfp_mask, 604 .nid = nid, 605 .memcg = memcg, 606 }; 607 struct shrinker *shrinker; 608 609 shrinker = idr_find(&shrinker_idr, i); 610 if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { 611 if (!shrinker) 612 clear_bit(i, map->map); 613 continue; 614 } 615 616 ret = do_shrink_slab(&sc, shrinker, priority); 617 if (ret == SHRINK_EMPTY) { 618 clear_bit(i, map->map); 619 /* 620 * After the shrinker reported that it had no objects to 621 * free, but before we cleared the corresponding bit in 622 * the memcg shrinker map, a new object might have been 623 * added. To make sure, we have the bit set in this 624 * case, we invoke the shrinker one more time and reset 625 * the bit if it reports that it is not empty anymore. 626 * The memory barrier here pairs with the barrier in 627 * memcg_set_shrinker_bit(): 628 * 629 * list_lru_add() shrink_slab_memcg() 630 * list_add_tail() clear_bit() 631 * <MB> <MB> 632 * set_bit() do_shrink_slab() 633 */ 634 smp_mb__after_atomic(); 635 ret = do_shrink_slab(&sc, shrinker, priority); 636 if (ret == SHRINK_EMPTY) 637 ret = 0; 638 else 639 memcg_set_shrinker_bit(memcg, nid, i); 640 } 641 freed += ret; 642 643 if (rwsem_is_contended(&shrinker_rwsem)) { 644 freed = freed ? : 1; 645 break; 646 } 647 } 648 unlock: 649 up_read(&shrinker_rwsem); 650 return freed; 651 } 652 #else /* CONFIG_MEMCG_KMEM */ 653 static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, 654 struct mem_cgroup *memcg, int priority) 655 { 656 return 0; 657 } 658 #endif /* CONFIG_MEMCG_KMEM */ 659 660 /** 661 * shrink_slab - shrink slab caches 662 * @gfp_mask: allocation context 663 * @nid: node whose slab caches to target 664 * @memcg: memory cgroup whose slab caches to target 665 * @priority: the reclaim priority 666 * 667 * Call the shrink functions to age shrinkable caches. 668 * 669 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set, 670 * unaware shrinkers will receive a node id of 0 instead. 671 * 672 * @memcg specifies the memory cgroup to target. Unaware shrinkers 673 * are called only if it is the root cgroup. 674 * 675 * @priority is sc->priority, we take the number of objects and >> by priority 676 * in order to get the scan target. 677 * 678 * Returns the number of reclaimed slab objects. 679 */ 680 static unsigned long shrink_slab(gfp_t gfp_mask, int nid, 681 struct mem_cgroup *memcg, 682 int priority) 683 { 684 unsigned long ret, freed = 0; 685 struct shrinker *shrinker; 686 687 if (!mem_cgroup_is_root(memcg)) 688 return shrink_slab_memcg(gfp_mask, nid, memcg, priority); 689 690 if (!down_read_trylock(&shrinker_rwsem)) 691 goto out; 692 693 list_for_each_entry(shrinker, &shrinker_list, list) { 694 struct shrink_control sc = { 695 .gfp_mask = gfp_mask, 696 .nid = nid, 697 .memcg = memcg, 698 }; 699 700 ret = do_shrink_slab(&sc, shrinker, priority); 701 if (ret == SHRINK_EMPTY) 702 ret = 0; 703 freed += ret; 704 /* 705 * Bail out if someone want to register a new shrinker to 706 * prevent the regsitration from being stalled for long periods 707 * by parallel ongoing shrinking. 708 */ 709 if (rwsem_is_contended(&shrinker_rwsem)) { 710 freed = freed ? : 1; 711 break; 712 } 713 } 714 715 up_read(&shrinker_rwsem); 716 out: 717 cond_resched(); 718 return freed; 719 } 720 721 void drop_slab_node(int nid) 722 { 723 unsigned long freed; 724 725 do { 726 struct mem_cgroup *memcg = NULL; 727 728 freed = 0; 729 memcg = mem_cgroup_iter(NULL, NULL, NULL); 730 do { 731 freed += shrink_slab(GFP_KERNEL, nid, memcg, 0); 732 } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); 733 } while (freed > 10); 734 } 735 736 void drop_slab(void) 737 { 738 int nid; 739 740 for_each_online_node(nid) 741 drop_slab_node(nid); 742 } 743 744 static inline int is_page_cache_freeable(struct page *page) 745 { 746 /* 747 * A freeable page cache page is referenced only by the caller 748 * that isolated the page, the page cache and optional buffer 749 * heads at page->private. 750 */ 751 int page_cache_pins = PageTransHuge(page) && PageSwapCache(page) ? 752 HPAGE_PMD_NR : 1; 753 return page_count(page) - page_has_private(page) == 1 + page_cache_pins; 754 } 755 756 static int may_write_to_inode(struct inode *inode, struct scan_control *sc) 757 { 758 if (current->flags & PF_SWAPWRITE) 759 return 1; 760 if (!inode_write_congested(inode)) 761 return 1; 762 if (inode_to_bdi(inode) == current->backing_dev_info) 763 return 1; 764 return 0; 765 } 766 767 /* 768 * We detected a synchronous write error writing a page out. Probably 769 * -ENOSPC. We need to propagate that into the address_space for a subsequent 770 * fsync(), msync() or close(). 771 * 772 * The tricky part is that after writepage we cannot touch the mapping: nothing 773 * prevents it from being freed up. But we have a ref on the page and once 774 * that page is locked, the mapping is pinned. 775 * 776 * We're allowed to run sleeping lock_page() here because we know the caller has 777 * __GFP_FS. 778 */ 779 static void handle_write_error(struct address_space *mapping, 780 struct page *page, int error) 781 { 782 lock_page(page); 783 if (page_mapping(page) == mapping) 784 mapping_set_error(mapping, error); 785 unlock_page(page); 786 } 787 788 /* possible outcome of pageout() */ 789 typedef enum { 790 /* failed to write page out, page is locked */ 791 PAGE_KEEP, 792 /* move page to the active list, page is locked */ 793 PAGE_ACTIVATE, 794 /* page has been sent to the disk successfully, page is unlocked */ 795 PAGE_SUCCESS, 796 /* page is clean and locked */ 797 PAGE_CLEAN, 798 } pageout_t; 799 800 /* 801 * pageout is called by shrink_page_list() for each dirty page. 802 * Calls ->writepage(). 803 */ 804 static pageout_t pageout(struct page *page, struct address_space *mapping, 805 struct scan_control *sc) 806 { 807 /* 808 * If the page is dirty, only perform writeback if that write 809 * will be non-blocking. To prevent this allocation from being 810 * stalled by pagecache activity. But note that there may be 811 * stalls if we need to run get_block(). We could test 812 * PagePrivate for that. 813 * 814 * If this process is currently in __generic_file_write_iter() against 815 * this page's queue, we can perform writeback even if that 816 * will block. 817 * 818 * If the page is swapcache, write it back even if that would 819 * block, for some throttling. This happens by accident, because 820 * swap_backing_dev_info is bust: it doesn't reflect the 821 * congestion state of the swapdevs. Easy to fix, if needed. 822 */ 823 if (!is_page_cache_freeable(page)) 824 return PAGE_KEEP; 825 if (!mapping) { 826 /* 827 * Some data journaling orphaned pages can have 828 * page->mapping == NULL while being dirty with clean buffers. 829 */ 830 if (page_has_private(page)) { 831 if (try_to_free_buffers(page)) { 832 ClearPageDirty(page); 833 pr_info("%s: orphaned page\n", __func__); 834 return PAGE_CLEAN; 835 } 836 } 837 return PAGE_KEEP; 838 } 839 if (mapping->a_ops->writepage == NULL) 840 return PAGE_ACTIVATE; 841 if (!may_write_to_inode(mapping->host, sc)) 842 return PAGE_KEEP; 843 844 if (clear_page_dirty_for_io(page)) { 845 int res; 846 struct writeback_control wbc = { 847 .sync_mode = WB_SYNC_NONE, 848 .nr_to_write = SWAP_CLUSTER_MAX, 849 .range_start = 0, 850 .range_end = LLONG_MAX, 851 .for_reclaim = 1, 852 }; 853 854 SetPageReclaim(page); 855 res = mapping->a_ops->writepage(page, &wbc); 856 if (res < 0) 857 handle_write_error(mapping, page, res); 858 if (res == AOP_WRITEPAGE_ACTIVATE) { 859 ClearPageReclaim(page); 860 return PAGE_ACTIVATE; 861 } 862 863 if (!PageWriteback(page)) { 864 /* synchronous write or broken a_ops? */ 865 ClearPageReclaim(page); 866 } 867 trace_mm_vmscan_writepage(page); 868 inc_node_page_state(page, NR_VMSCAN_WRITE); 869 return PAGE_SUCCESS; 870 } 871 872 return PAGE_CLEAN; 873 } 874 875 /* 876 * Same as remove_mapping, but if the page is removed from the mapping, it 877 * gets returned with a refcount of 0. 878 */ 879 static int __remove_mapping(struct address_space *mapping, struct page *page, 880 bool reclaimed) 881 { 882 unsigned long flags; 883 int refcount; 884 885 BUG_ON(!PageLocked(page)); 886 BUG_ON(mapping != page_mapping(page)); 887 888 xa_lock_irqsave(&mapping->i_pages, flags); 889 /* 890 * The non racy check for a busy page. 891 * 892 * Must be careful with the order of the tests. When someone has 893 * a ref to the page, it may be possible that they dirty it then 894 * drop the reference. So if PageDirty is tested before page_count 895 * here, then the following race may occur: 896 * 897 * get_user_pages(&page); 898 * [user mapping goes away] 899 * write_to(page); 900 * !PageDirty(page) [good] 901 * SetPageDirty(page); 902 * put_page(page); 903 * !page_count(page) [good, discard it] 904 * 905 * [oops, our write_to data is lost] 906 * 907 * Reversing the order of the tests ensures such a situation cannot 908 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 909 * load is not satisfied before that of page->_refcount. 910 * 911 * Note that if SetPageDirty is always performed via set_page_dirty, 912 * and thus under the i_pages lock, then this ordering is not required. 913 */ 914 if (unlikely(PageTransHuge(page)) && PageSwapCache(page)) 915 refcount = 1 + HPAGE_PMD_NR; 916 else 917 refcount = 2; 918 if (!page_ref_freeze(page, refcount)) 919 goto cannot_free; 920 /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */ 921 if (unlikely(PageDirty(page))) { 922 page_ref_unfreeze(page, refcount); 923 goto cannot_free; 924 } 925 926 if (PageSwapCache(page)) { 927 swp_entry_t swap = { .val = page_private(page) }; 928 mem_cgroup_swapout(page, swap); 929 __delete_from_swap_cache(page, swap); 930 xa_unlock_irqrestore(&mapping->i_pages, flags); 931 put_swap_page(page, swap); 932 } else { 933 void (*freepage)(struct page *); 934 void *shadow = NULL; 935 936 freepage = mapping->a_ops->freepage; 937 /* 938 * Remember a shadow entry for reclaimed file cache in 939 * order to detect refaults, thus thrashing, later on. 940 * 941 * But don't store shadows in an address space that is 942 * already exiting. This is not just an optizimation, 943 * inode reclaim needs to empty out the radix tree or 944 * the nodes are lost. Don't plant shadows behind its 945 * back. 946 * 947 * We also don't store shadows for DAX mappings because the 948 * only page cache pages found in these are zero pages 949 * covering holes, and because we don't want to mix DAX 950 * exceptional entries and shadow exceptional entries in the 951 * same address_space. 952 */ 953 if (reclaimed && page_is_file_cache(page) && 954 !mapping_exiting(mapping) && !dax_mapping(mapping)) 955 shadow = workingset_eviction(page); 956 __delete_from_page_cache(page, shadow); 957 xa_unlock_irqrestore(&mapping->i_pages, flags); 958 959 if (freepage != NULL) 960 freepage(page); 961 } 962 963 return 1; 964 965 cannot_free: 966 xa_unlock_irqrestore(&mapping->i_pages, flags); 967 return 0; 968 } 969 970 /* 971 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 972 * someone else has a ref on the page, abort and return 0. If it was 973 * successfully detached, return 1. Assumes the caller has a single ref on 974 * this page. 975 */ 976 int remove_mapping(struct address_space *mapping, struct page *page) 977 { 978 if (__remove_mapping(mapping, page, false)) { 979 /* 980 * Unfreezing the refcount with 1 rather than 2 effectively 981 * drops the pagecache ref for us without requiring another 982 * atomic operation. 983 */ 984 page_ref_unfreeze(page, 1); 985 return 1; 986 } 987 return 0; 988 } 989 990 /** 991 * putback_lru_page - put previously isolated page onto appropriate LRU list 992 * @page: page to be put back to appropriate lru list 993 * 994 * Add previously isolated @page to appropriate LRU list. 995 * Page may still be unevictable for other reasons. 996 * 997 * lru_lock must not be held, interrupts must be enabled. 998 */ 999 void putback_lru_page(struct page *page) 1000 { 1001 lru_cache_add(page); 1002 put_page(page); /* drop ref from isolate */ 1003 } 1004 1005 enum page_references { 1006 PAGEREF_RECLAIM, 1007 PAGEREF_RECLAIM_CLEAN, 1008 PAGEREF_KEEP, 1009 PAGEREF_ACTIVATE, 1010 }; 1011 1012 static enum page_references page_check_references(struct page *page, 1013 struct scan_control *sc) 1014 { 1015 int referenced_ptes, referenced_page; 1016 unsigned long vm_flags; 1017 1018 referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup, 1019 &vm_flags); 1020 referenced_page = TestClearPageReferenced(page); 1021 1022 /* 1023 * Mlock lost the isolation race with us. Let try_to_unmap() 1024 * move the page to the unevictable list. 1025 */ 1026 if (vm_flags & VM_LOCKED) 1027 return PAGEREF_RECLAIM; 1028 1029 if (referenced_ptes) { 1030 if (PageSwapBacked(page)) 1031 return PAGEREF_ACTIVATE; 1032 /* 1033 * All mapped pages start out with page table 1034 * references from the instantiating fault, so we need 1035 * to look twice if a mapped file page is used more 1036 * than once. 1037 * 1038 * Mark it and spare it for another trip around the 1039 * inactive list. Another page table reference will 1040 * lead to its activation. 1041 * 1042 * Note: the mark is set for activated pages as well 1043 * so that recently deactivated but used pages are 1044 * quickly recovered. 1045 */ 1046 SetPageReferenced(page); 1047 1048 if (referenced_page || referenced_ptes > 1) 1049 return PAGEREF_ACTIVATE; 1050 1051 /* 1052 * Activate file-backed executable pages after first usage. 1053 */ 1054 if (vm_flags & VM_EXEC) 1055 return PAGEREF_ACTIVATE; 1056 1057 return PAGEREF_KEEP; 1058 } 1059 1060 /* Reclaim if clean, defer dirty pages to writeback */ 1061 if (referenced_page && !PageSwapBacked(page)) 1062 return PAGEREF_RECLAIM_CLEAN; 1063 1064 return PAGEREF_RECLAIM; 1065 } 1066 1067 /* Check if a page is dirty or under writeback */ 1068 static void page_check_dirty_writeback(struct page *page, 1069 bool *dirty, bool *writeback) 1070 { 1071 struct address_space *mapping; 1072 1073 /* 1074 * Anonymous pages are not handled by flushers and must be written 1075 * from reclaim context. Do not stall reclaim based on them 1076 */ 1077 if (!page_is_file_cache(page) || 1078 (PageAnon(page) && !PageSwapBacked(page))) { 1079 *dirty = false; 1080 *writeback = false; 1081 return; 1082 } 1083 1084 /* By default assume that the page flags are accurate */ 1085 *dirty = PageDirty(page); 1086 *writeback = PageWriteback(page); 1087 1088 /* Verify dirty/writeback state if the filesystem supports it */ 1089 if (!page_has_private(page)) 1090 return; 1091 1092 mapping = page_mapping(page); 1093 if (mapping && mapping->a_ops->is_dirty_writeback) 1094 mapping->a_ops->is_dirty_writeback(page, dirty, writeback); 1095 } 1096 1097 /* 1098 * shrink_page_list() returns the number of reclaimed pages 1099 */ 1100 static unsigned long shrink_page_list(struct list_head *page_list, 1101 struct pglist_data *pgdat, 1102 struct scan_control *sc, 1103 enum ttu_flags ttu_flags, 1104 struct reclaim_stat *stat, 1105 bool force_reclaim) 1106 { 1107 LIST_HEAD(ret_pages); 1108 LIST_HEAD(free_pages); 1109 unsigned nr_reclaimed = 0; 1110 1111 memset(stat, 0, sizeof(*stat)); 1112 cond_resched(); 1113 1114 while (!list_empty(page_list)) { 1115 struct address_space *mapping; 1116 struct page *page; 1117 int may_enter_fs; 1118 enum page_references references = PAGEREF_RECLAIM_CLEAN; 1119 bool dirty, writeback; 1120 1121 cond_resched(); 1122 1123 page = lru_to_page(page_list); 1124 list_del(&page->lru); 1125 1126 if (!trylock_page(page)) 1127 goto keep; 1128 1129 VM_BUG_ON_PAGE(PageActive(page), page); 1130 1131 sc->nr_scanned++; 1132 1133 if (unlikely(!page_evictable(page))) 1134 goto activate_locked; 1135 1136 if (!sc->may_unmap && page_mapped(page)) 1137 goto keep_locked; 1138 1139 /* Double the slab pressure for mapped and swapcache pages */ 1140 if ((page_mapped(page) || PageSwapCache(page)) && 1141 !(PageAnon(page) && !PageSwapBacked(page))) 1142 sc->nr_scanned++; 1143 1144 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 1145 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 1146 1147 /* 1148 * The number of dirty pages determines if a node is marked 1149 * reclaim_congested which affects wait_iff_congested. kswapd 1150 * will stall and start writing pages if the tail of the LRU 1151 * is all dirty unqueued pages. 1152 */ 1153 page_check_dirty_writeback(page, &dirty, &writeback); 1154 if (dirty || writeback) 1155 stat->nr_dirty++; 1156 1157 if (dirty && !writeback) 1158 stat->nr_unqueued_dirty++; 1159 1160 /* 1161 * Treat this page as congested if the underlying BDI is or if 1162 * pages are cycling through the LRU so quickly that the 1163 * pages marked for immediate reclaim are making it to the 1164 * end of the LRU a second time. 1165 */ 1166 mapping = page_mapping(page); 1167 if (((dirty || writeback) && mapping && 1168 inode_write_congested(mapping->host)) || 1169 (writeback && PageReclaim(page))) 1170 stat->nr_congested++; 1171 1172 /* 1173 * If a page at the tail of the LRU is under writeback, there 1174 * are three cases to consider. 1175 * 1176 * 1) If reclaim is encountering an excessive number of pages 1177 * under writeback and this page is both under writeback and 1178 * PageReclaim then it indicates that pages are being queued 1179 * for IO but are being recycled through the LRU before the 1180 * IO can complete. Waiting on the page itself risks an 1181 * indefinite stall if it is impossible to writeback the 1182 * page due to IO error or disconnected storage so instead 1183 * note that the LRU is being scanned too quickly and the 1184 * caller can stall after page list has been processed. 1185 * 1186 * 2) Global or new memcg reclaim encounters a page that is 1187 * not marked for immediate reclaim, or the caller does not 1188 * have __GFP_FS (or __GFP_IO if it's simply going to swap, 1189 * not to fs). In this case mark the page for immediate 1190 * reclaim and continue scanning. 1191 * 1192 * Require may_enter_fs because we would wait on fs, which 1193 * may not have submitted IO yet. And the loop driver might 1194 * enter reclaim, and deadlock if it waits on a page for 1195 * which it is needed to do the write (loop masks off 1196 * __GFP_IO|__GFP_FS for this reason); but more thought 1197 * would probably show more reasons. 1198 * 1199 * 3) Legacy memcg encounters a page that is already marked 1200 * PageReclaim. memcg does not have any dirty pages 1201 * throttling so we could easily OOM just because too many 1202 * pages are in writeback and there is nothing else to 1203 * reclaim. Wait for the writeback to complete. 1204 * 1205 * In cases 1) and 2) we activate the pages to get them out of 1206 * the way while we continue scanning for clean pages on the 1207 * inactive list and refilling from the active list. The 1208 * observation here is that waiting for disk writes is more 1209 * expensive than potentially causing reloads down the line. 1210 * Since they're marked for immediate reclaim, they won't put 1211 * memory pressure on the cache working set any longer than it 1212 * takes to write them to disk. 1213 */ 1214 if (PageWriteback(page)) { 1215 /* Case 1 above */ 1216 if (current_is_kswapd() && 1217 PageReclaim(page) && 1218 test_bit(PGDAT_WRITEBACK, &pgdat->flags)) { 1219 stat->nr_immediate++; 1220 goto activate_locked; 1221 1222 /* Case 2 above */ 1223 } else if (sane_reclaim(sc) || 1224 !PageReclaim(page) || !may_enter_fs) { 1225 /* 1226 * This is slightly racy - end_page_writeback() 1227 * might have just cleared PageReclaim, then 1228 * setting PageReclaim here end up interpreted 1229 * as PageReadahead - but that does not matter 1230 * enough to care. What we do want is for this 1231 * page to have PageReclaim set next time memcg 1232 * reclaim reaches the tests above, so it will 1233 * then wait_on_page_writeback() to avoid OOM; 1234 * and it's also appropriate in global reclaim. 1235 */ 1236 SetPageReclaim(page); 1237 stat->nr_writeback++; 1238 goto activate_locked; 1239 1240 /* Case 3 above */ 1241 } else { 1242 unlock_page(page); 1243 wait_on_page_writeback(page); 1244 /* then go back and try same page again */ 1245 list_add_tail(&page->lru, page_list); 1246 continue; 1247 } 1248 } 1249 1250 if (!force_reclaim) 1251 references = page_check_references(page, sc); 1252 1253 switch (references) { 1254 case PAGEREF_ACTIVATE: 1255 goto activate_locked; 1256 case PAGEREF_KEEP: 1257 stat->nr_ref_keep++; 1258 goto keep_locked; 1259 case PAGEREF_RECLAIM: 1260 case PAGEREF_RECLAIM_CLEAN: 1261 ; /* try to reclaim the page below */ 1262 } 1263 1264 /* 1265 * Anonymous process memory has backing store? 1266 * Try to allocate it some swap space here. 1267 * Lazyfree page could be freed directly 1268 */ 1269 if (PageAnon(page) && PageSwapBacked(page)) { 1270 if (!PageSwapCache(page)) { 1271 if (!(sc->gfp_mask & __GFP_IO)) 1272 goto keep_locked; 1273 if (PageTransHuge(page)) { 1274 /* cannot split THP, skip it */ 1275 if (!can_split_huge_page(page, NULL)) 1276 goto activate_locked; 1277 /* 1278 * Split pages without a PMD map right 1279 * away. Chances are some or all of the 1280 * tail pages can be freed without IO. 1281 */ 1282 if (!compound_mapcount(page) && 1283 split_huge_page_to_list(page, 1284 page_list)) 1285 goto activate_locked; 1286 } 1287 if (!add_to_swap(page)) { 1288 if (!PageTransHuge(page)) 1289 goto activate_locked; 1290 /* Fallback to swap normal pages */ 1291 if (split_huge_page_to_list(page, 1292 page_list)) 1293 goto activate_locked; 1294 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 1295 count_vm_event(THP_SWPOUT_FALLBACK); 1296 #endif 1297 if (!add_to_swap(page)) 1298 goto activate_locked; 1299 } 1300 1301 may_enter_fs = 1; 1302 1303 /* Adding to swap updated mapping */ 1304 mapping = page_mapping(page); 1305 } 1306 } else if (unlikely(PageTransHuge(page))) { 1307 /* Split file THP */ 1308 if (split_huge_page_to_list(page, page_list)) 1309 goto keep_locked; 1310 } 1311 1312 /* 1313 * The page is mapped into the page tables of one or more 1314 * processes. Try to unmap it here. 1315 */ 1316 if (page_mapped(page)) { 1317 enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH; 1318 1319 if (unlikely(PageTransHuge(page))) 1320 flags |= TTU_SPLIT_HUGE_PMD; 1321 if (!try_to_unmap(page, flags)) { 1322 stat->nr_unmap_fail++; 1323 goto activate_locked; 1324 } 1325 } 1326 1327 if (PageDirty(page)) { 1328 /* 1329 * Only kswapd can writeback filesystem pages 1330 * to avoid risk of stack overflow. But avoid 1331 * injecting inefficient single-page IO into 1332 * flusher writeback as much as possible: only 1333 * write pages when we've encountered many 1334 * dirty pages, and when we've already scanned 1335 * the rest of the LRU for clean pages and see 1336 * the same dirty pages again (PageReclaim). 1337 */ 1338 if (page_is_file_cache(page) && 1339 (!current_is_kswapd() || !PageReclaim(page) || 1340 !test_bit(PGDAT_DIRTY, &pgdat->flags))) { 1341 /* 1342 * Immediately reclaim when written back. 1343 * Similar in principal to deactivate_page() 1344 * except we already have the page isolated 1345 * and know it's dirty 1346 */ 1347 inc_node_page_state(page, NR_VMSCAN_IMMEDIATE); 1348 SetPageReclaim(page); 1349 1350 goto activate_locked; 1351 } 1352 1353 if (references == PAGEREF_RECLAIM_CLEAN) 1354 goto keep_locked; 1355 if (!may_enter_fs) 1356 goto keep_locked; 1357 if (!sc->may_writepage) 1358 goto keep_locked; 1359 1360 /* 1361 * Page is dirty. Flush the TLB if a writable entry 1362 * potentially exists to avoid CPU writes after IO 1363 * starts and then write it out here. 1364 */ 1365 try_to_unmap_flush_dirty(); 1366 switch (pageout(page, mapping, sc)) { 1367 case PAGE_KEEP: 1368 goto keep_locked; 1369 case PAGE_ACTIVATE: 1370 goto activate_locked; 1371 case PAGE_SUCCESS: 1372 if (PageWriteback(page)) 1373 goto keep; 1374 if (PageDirty(page)) 1375 goto keep; 1376 1377 /* 1378 * A synchronous write - probably a ramdisk. Go 1379 * ahead and try to reclaim the page. 1380 */ 1381 if (!trylock_page(page)) 1382 goto keep; 1383 if (PageDirty(page) || PageWriteback(page)) 1384 goto keep_locked; 1385 mapping = page_mapping(page); 1386 case PAGE_CLEAN: 1387 ; /* try to free the page below */ 1388 } 1389 } 1390 1391 /* 1392 * If the page has buffers, try to free the buffer mappings 1393 * associated with this page. If we succeed we try to free 1394 * the page as well. 1395 * 1396 * We do this even if the page is PageDirty(). 1397 * try_to_release_page() does not perform I/O, but it is 1398 * possible for a page to have PageDirty set, but it is actually 1399 * clean (all its buffers are clean). This happens if the 1400 * buffers were written out directly, with submit_bh(). ext3 1401 * will do this, as well as the blockdev mapping. 1402 * try_to_release_page() will discover that cleanness and will 1403 * drop the buffers and mark the page clean - it can be freed. 1404 * 1405 * Rarely, pages can have buffers and no ->mapping. These are 1406 * the pages which were not successfully invalidated in 1407 * truncate_complete_page(). We try to drop those buffers here 1408 * and if that worked, and the page is no longer mapped into 1409 * process address space (page_count == 1) it can be freed. 1410 * Otherwise, leave the page on the LRU so it is swappable. 1411 */ 1412 if (page_has_private(page)) { 1413 if (!try_to_release_page(page, sc->gfp_mask)) 1414 goto activate_locked; 1415 if (!mapping && page_count(page) == 1) { 1416 unlock_page(page); 1417 if (put_page_testzero(page)) 1418 goto free_it; 1419 else { 1420 /* 1421 * rare race with speculative reference. 1422 * the speculative reference will free 1423 * this page shortly, so we may 1424 * increment nr_reclaimed here (and 1425 * leave it off the LRU). 1426 */ 1427 nr_reclaimed++; 1428 continue; 1429 } 1430 } 1431 } 1432 1433 if (PageAnon(page) && !PageSwapBacked(page)) { 1434 /* follow __remove_mapping for reference */ 1435 if (!page_ref_freeze(page, 1)) 1436 goto keep_locked; 1437 if (PageDirty(page)) { 1438 page_ref_unfreeze(page, 1); 1439 goto keep_locked; 1440 } 1441 1442 count_vm_event(PGLAZYFREED); 1443 count_memcg_page_event(page, PGLAZYFREED); 1444 } else if (!mapping || !__remove_mapping(mapping, page, true)) 1445 goto keep_locked; 1446 1447 unlock_page(page); 1448 free_it: 1449 nr_reclaimed++; 1450 1451 /* 1452 * Is there need to periodically free_page_list? It would 1453 * appear not as the counts should be low 1454 */ 1455 if (unlikely(PageTransHuge(page))) { 1456 mem_cgroup_uncharge(page); 1457 (*get_compound_page_dtor(page))(page); 1458 } else 1459 list_add(&page->lru, &free_pages); 1460 continue; 1461 1462 activate_locked: 1463 /* Not a candidate for swapping, so reclaim swap space. */ 1464 if (PageSwapCache(page) && (mem_cgroup_swap_full(page) || 1465 PageMlocked(page))) 1466 try_to_free_swap(page); 1467 VM_BUG_ON_PAGE(PageActive(page), page); 1468 if (!PageMlocked(page)) { 1469 SetPageActive(page); 1470 stat->nr_activate++; 1471 count_memcg_page_event(page, PGACTIVATE); 1472 } 1473 keep_locked: 1474 unlock_page(page); 1475 keep: 1476 list_add(&page->lru, &ret_pages); 1477 VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page); 1478 } 1479 1480 mem_cgroup_uncharge_list(&free_pages); 1481 try_to_unmap_flush(); 1482 free_unref_page_list(&free_pages); 1483 1484 list_splice(&ret_pages, page_list); 1485 count_vm_events(PGACTIVATE, stat->nr_activate); 1486 1487 return nr_reclaimed; 1488 } 1489 1490 unsigned long reclaim_clean_pages_from_list(struct zone *zone, 1491 struct list_head *page_list) 1492 { 1493 struct scan_control sc = { 1494 .gfp_mask = GFP_KERNEL, 1495 .priority = DEF_PRIORITY, 1496 .may_unmap = 1, 1497 }; 1498 struct reclaim_stat dummy_stat; 1499 unsigned long ret; 1500 struct page *page, *next; 1501 LIST_HEAD(clean_pages); 1502 1503 list_for_each_entry_safe(page, next, page_list, lru) { 1504 if (page_is_file_cache(page) && !PageDirty(page) && 1505 !__PageMovable(page)) { 1506 ClearPageActive(page); 1507 list_move(&page->lru, &clean_pages); 1508 } 1509 } 1510 1511 ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, 1512 TTU_IGNORE_ACCESS, &dummy_stat, true); 1513 list_splice(&clean_pages, page_list); 1514 mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret); 1515 return ret; 1516 } 1517 1518 /* 1519 * Attempt to remove the specified page from its LRU. Only take this page 1520 * if it is of the appropriate PageActive status. Pages which are being 1521 * freed elsewhere are also ignored. 1522 * 1523 * page: page to consider 1524 * mode: one of the LRU isolation modes defined above 1525 * 1526 * returns 0 on success, -ve errno on failure. 1527 */ 1528 int __isolate_lru_page(struct page *page, isolate_mode_t mode) 1529 { 1530 int ret = -EINVAL; 1531 1532 /* Only take pages on the LRU. */ 1533 if (!PageLRU(page)) 1534 return ret; 1535 1536 /* Compaction should not handle unevictable pages but CMA can do so */ 1537 if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) 1538 return ret; 1539 1540 ret = -EBUSY; 1541 1542 /* 1543 * To minimise LRU disruption, the caller can indicate that it only 1544 * wants to isolate pages it will be able to operate on without 1545 * blocking - clean pages for the most part. 1546 * 1547 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages 1548 * that it is possible to migrate without blocking 1549 */ 1550 if (mode & ISOLATE_ASYNC_MIGRATE) { 1551 /* All the caller can do on PageWriteback is block */ 1552 if (PageWriteback(page)) 1553 return ret; 1554 1555 if (PageDirty(page)) { 1556 struct address_space *mapping; 1557 bool migrate_dirty; 1558 1559 /* 1560 * Only pages without mappings or that have a 1561 * ->migratepage callback are possible to migrate 1562 * without blocking. However, we can be racing with 1563 * truncation so it's necessary to lock the page 1564 * to stabilise the mapping as truncation holds 1565 * the page lock until after the page is removed 1566 * from the page cache. 1567 */ 1568 if (!trylock_page(page)) 1569 return ret; 1570 1571 mapping = page_mapping(page); 1572 migrate_dirty = !mapping || mapping->a_ops->migratepage; 1573 unlock_page(page); 1574 if (!migrate_dirty) 1575 return ret; 1576 } 1577 } 1578 1579 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) 1580 return ret; 1581 1582 if (likely(get_page_unless_zero(page))) { 1583 /* 1584 * Be careful not to clear PageLRU until after we're 1585 * sure the page is not being freed elsewhere -- the 1586 * page release code relies on it. 1587 */ 1588 ClearPageLRU(page); 1589 ret = 0; 1590 } 1591 1592 return ret; 1593 } 1594 1595 1596 /* 1597 * Update LRU sizes after isolating pages. The LRU size updates must 1598 * be complete before mem_cgroup_update_lru_size due to a santity check. 1599 */ 1600 static __always_inline void update_lru_sizes(struct lruvec *lruvec, 1601 enum lru_list lru, unsigned long *nr_zone_taken) 1602 { 1603 int zid; 1604 1605 for (zid = 0; zid < MAX_NR_ZONES; zid++) { 1606 if (!nr_zone_taken[zid]) 1607 continue; 1608 1609 __update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]); 1610 #ifdef CONFIG_MEMCG 1611 mem_cgroup_update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]); 1612 #endif 1613 } 1614 1615 } 1616 1617 /** 1618 * pgdat->lru_lock is heavily contended. Some of the functions that 1619 * shrink the lists perform better by taking out a batch of pages 1620 * and working on them outside the LRU lock. 1621 * 1622 * For pagecache intensive workloads, this function is the hottest 1623 * spot in the kernel (apart from copy_*_user functions). 1624 * 1625 * Appropriate locks must be held before calling this function. 1626 * 1627 * @nr_to_scan: The number of eligible pages to look through on the list. 1628 * @lruvec: The LRU vector to pull pages from. 1629 * @dst: The temp list to put pages on to. 1630 * @nr_scanned: The number of pages that were scanned. 1631 * @sc: The scan_control struct for this reclaim session 1632 * @mode: One of the LRU isolation modes 1633 * @lru: LRU list id for isolating 1634 * 1635 * returns how many pages were moved onto *@dst. 1636 */ 1637 static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1638 struct lruvec *lruvec, struct list_head *dst, 1639 unsigned long *nr_scanned, struct scan_control *sc, 1640 enum lru_list lru) 1641 { 1642 struct list_head *src = &lruvec->lists[lru]; 1643 unsigned long nr_taken = 0; 1644 unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; 1645 unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; 1646 unsigned long skipped = 0; 1647 unsigned long scan, total_scan, nr_pages; 1648 LIST_HEAD(pages_skipped); 1649 isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED); 1650 1651 scan = 0; 1652 for (total_scan = 0; 1653 scan < nr_to_scan && nr_taken < nr_to_scan && !list_empty(src); 1654 total_scan++) { 1655 struct page *page; 1656 1657 page = lru_to_page(src); 1658 prefetchw_prev_lru_page(page, src, flags); 1659 1660 VM_BUG_ON_PAGE(!PageLRU(page), page); 1661 1662 if (page_zonenum(page) > sc->reclaim_idx) { 1663 list_move(&page->lru, &pages_skipped); 1664 nr_skipped[page_zonenum(page)]++; 1665 continue; 1666 } 1667 1668 /* 1669 * Do not count skipped pages because that makes the function 1670 * return with no isolated pages if the LRU mostly contains 1671 * ineligible pages. This causes the VM to not reclaim any 1672 * pages, triggering a premature OOM. 1673 */ 1674 scan++; 1675 switch (__isolate_lru_page(page, mode)) { 1676 case 0: 1677 nr_pages = hpage_nr_pages(page); 1678 nr_taken += nr_pages; 1679 nr_zone_taken[page_zonenum(page)] += nr_pages; 1680 list_move(&page->lru, dst); 1681 break; 1682 1683 case -EBUSY: 1684 /* else it is being freed elsewhere */ 1685 list_move(&page->lru, src); 1686 continue; 1687 1688 default: 1689 BUG(); 1690 } 1691 } 1692 1693 /* 1694 * Splice any skipped pages to the start of the LRU list. Note that 1695 * this disrupts the LRU order when reclaiming for lower zones but 1696 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX 1697 * scanning would soon rescan the same pages to skip and put the 1698 * system at risk of premature OOM. 1699 */ 1700 if (!list_empty(&pages_skipped)) { 1701 int zid; 1702 1703 list_splice(&pages_skipped, src); 1704 for (zid = 0; zid < MAX_NR_ZONES; zid++) { 1705 if (!nr_skipped[zid]) 1706 continue; 1707 1708 __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); 1709 skipped += nr_skipped[zid]; 1710 } 1711 } 1712 *nr_scanned = total_scan; 1713 trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, 1714 total_scan, skipped, nr_taken, mode, lru); 1715 update_lru_sizes(lruvec, lru, nr_zone_taken); 1716 return nr_taken; 1717 } 1718 1719 /** 1720 * isolate_lru_page - tries to isolate a page from its LRU list 1721 * @page: page to isolate from its LRU list 1722 * 1723 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1724 * vmstat statistic corresponding to whatever LRU list the page was on. 1725 * 1726 * Returns 0 if the page was removed from an LRU list. 1727 * Returns -EBUSY if the page was not on an LRU list. 1728 * 1729 * The returned page will have PageLRU() cleared. If it was found on 1730 * the active list, it will have PageActive set. If it was found on 1731 * the unevictable list, it will have the PageUnevictable bit set. That flag 1732 * may need to be cleared by the caller before letting the page go. 1733 * 1734 * The vmstat statistic corresponding to the list on which the page was 1735 * found will be decremented. 1736 * 1737 * Restrictions: 1738 * 1739 * (1) Must be called with an elevated refcount on the page. This is a 1740 * fundamentnal difference from isolate_lru_pages (which is called 1741 * without a stable reference). 1742 * (2) the lru_lock must not be held. 1743 * (3) interrupts must be enabled. 1744 */ 1745 int isolate_lru_page(struct page *page) 1746 { 1747 int ret = -EBUSY; 1748 1749 VM_BUG_ON_PAGE(!page_count(page), page); 1750 WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"); 1751 1752 if (PageLRU(page)) { 1753 pg_data_t *pgdat = page_pgdat(page); 1754 struct lruvec *lruvec; 1755 1756 spin_lock_irq(&pgdat->lru_lock); 1757 lruvec = mem_cgroup_page_lruvec(page, pgdat); 1758 if (PageLRU(page)) { 1759 int lru = page_lru(page); 1760 get_page(page); 1761 ClearPageLRU(page); 1762 del_page_from_lru_list(page, lruvec, lru); 1763 ret = 0; 1764 } 1765 spin_unlock_irq(&pgdat->lru_lock); 1766 } 1767 return ret; 1768 } 1769 1770 /* 1771 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and 1772 * then get resheduled. When there are massive number of tasks doing page 1773 * allocation, such sleeping direct reclaimers may keep piling up on each CPU, 1774 * the LRU list will go small and be scanned faster than necessary, leading to 1775 * unnecessary swapping, thrashing and OOM. 1776 */ 1777 static int too_many_isolated(struct pglist_data *pgdat, int file, 1778 struct scan_control *sc) 1779 { 1780 unsigned long inactive, isolated; 1781 1782 if (current_is_kswapd()) 1783 return 0; 1784 1785 if (!sane_reclaim(sc)) 1786 return 0; 1787 1788 if (file) { 1789 inactive = node_page_state(pgdat, NR_INACTIVE_FILE); 1790 isolated = node_page_state(pgdat, NR_ISOLATED_FILE); 1791 } else { 1792 inactive = node_page_state(pgdat, NR_INACTIVE_ANON); 1793 isolated = node_page_state(pgdat, NR_ISOLATED_ANON); 1794 } 1795 1796 /* 1797 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they 1798 * won't get blocked by normal direct-reclaimers, forming a circular 1799 * deadlock. 1800 */ 1801 if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS)) 1802 inactive >>= 3; 1803 1804 return isolated > inactive; 1805 } 1806 1807 static noinline_for_stack void 1808 putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) 1809 { 1810 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; 1811 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 1812 LIST_HEAD(pages_to_free); 1813 1814 /* 1815 * Put back any unfreeable pages. 1816 */ 1817 while (!list_empty(page_list)) { 1818 struct page *page = lru_to_page(page_list); 1819 int lru; 1820 1821 VM_BUG_ON_PAGE(PageLRU(page), page); 1822 list_del(&page->lru); 1823 if (unlikely(!page_evictable(page))) { 1824 spin_unlock_irq(&pgdat->lru_lock); 1825 putback_lru_page(page); 1826 spin_lock_irq(&pgdat->lru_lock); 1827 continue; 1828 } 1829 1830 lruvec = mem_cgroup_page_lruvec(page, pgdat); 1831 1832 SetPageLRU(page); 1833 lru = page_lru(page); 1834 add_page_to_lru_list(page, lruvec, lru); 1835 1836 if (is_active_lru(lru)) { 1837 int file = is_file_lru(lru); 1838 int numpages = hpage_nr_pages(page); 1839 reclaim_stat->recent_rotated[file] += numpages; 1840 } 1841 if (put_page_testzero(page)) { 1842 __ClearPageLRU(page); 1843 __ClearPageActive(page); 1844 del_page_from_lru_list(page, lruvec, lru); 1845 1846 if (unlikely(PageCompound(page))) { 1847 spin_unlock_irq(&pgdat->lru_lock); 1848 mem_cgroup_uncharge(page); 1849 (*get_compound_page_dtor(page))(page); 1850 spin_lock_irq(&pgdat->lru_lock); 1851 } else 1852 list_add(&page->lru, &pages_to_free); 1853 } 1854 } 1855 1856 /* 1857 * To save our caller's stack, now use input list for pages to free. 1858 */ 1859 list_splice(&pages_to_free, page_list); 1860 } 1861 1862 /* 1863 * If a kernel thread (such as nfsd for loop-back mounts) services 1864 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE. 1865 * In that case we should only throttle if the backing device it is 1866 * writing to is congested. In other cases it is safe to throttle. 1867 */ 1868 static int current_may_throttle(void) 1869 { 1870 return !(current->flags & PF_LESS_THROTTLE) || 1871 current->backing_dev_info == NULL || 1872 bdi_write_congested(current->backing_dev_info); 1873 } 1874 1875 /* 1876 * shrink_inactive_list() is a helper for shrink_node(). It returns the number 1877 * of reclaimed pages 1878 */ 1879 static noinline_for_stack unsigned long 1880 shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, 1881 struct scan_control *sc, enum lru_list lru) 1882 { 1883 LIST_HEAD(page_list); 1884 unsigned long nr_scanned; 1885 unsigned long nr_reclaimed = 0; 1886 unsigned long nr_taken; 1887 struct reclaim_stat stat; 1888 int file = is_file_lru(lru); 1889 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 1890 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; 1891 bool stalled = false; 1892 1893 while (unlikely(too_many_isolated(pgdat, file, sc))) { 1894 if (stalled) 1895 return 0; 1896 1897 /* wait a bit for the reclaimer. */ 1898 msleep(100); 1899 stalled = true; 1900 1901 /* We are about to die and free our memory. Return now. */ 1902 if (fatal_signal_pending(current)) 1903 return SWAP_CLUSTER_MAX; 1904 } 1905 1906 lru_add_drain(); 1907 1908 spin_lock_irq(&pgdat->lru_lock); 1909 1910 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list, 1911 &nr_scanned, sc, lru); 1912 1913 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); 1914 reclaim_stat->recent_scanned[file] += nr_taken; 1915 1916 if (current_is_kswapd()) { 1917 if (global_reclaim(sc)) 1918 __count_vm_events(PGSCAN_KSWAPD, nr_scanned); 1919 count_memcg_events(lruvec_memcg(lruvec), PGSCAN_KSWAPD, 1920 nr_scanned); 1921 } else { 1922 if (global_reclaim(sc)) 1923 __count_vm_events(PGSCAN_DIRECT, nr_scanned); 1924 count_memcg_events(lruvec_memcg(lruvec), PGSCAN_DIRECT, 1925 nr_scanned); 1926 } 1927 spin_unlock_irq(&pgdat->lru_lock); 1928 1929 if (nr_taken == 0) 1930 return 0; 1931 1932 nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, 0, 1933 &stat, false); 1934 1935 spin_lock_irq(&pgdat->lru_lock); 1936 1937 if (current_is_kswapd()) { 1938 if (global_reclaim(sc)) 1939 __count_vm_events(PGSTEAL_KSWAPD, nr_reclaimed); 1940 count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_KSWAPD, 1941 nr_reclaimed); 1942 } else { 1943 if (global_reclaim(sc)) 1944 __count_vm_events(PGSTEAL_DIRECT, nr_reclaimed); 1945 count_memcg_events(lruvec_memcg(lruvec), PGSTEAL_DIRECT, 1946 nr_reclaimed); 1947 } 1948 1949 putback_inactive_pages(lruvec, &page_list); 1950 1951 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); 1952 1953 spin_unlock_irq(&pgdat->lru_lock); 1954 1955 mem_cgroup_uncharge_list(&page_list); 1956 free_unref_page_list(&page_list); 1957 1958 /* 1959 * If dirty pages are scanned that are not queued for IO, it 1960 * implies that flushers are not doing their job. This can 1961 * happen when memory pressure pushes dirty pages to the end of 1962 * the LRU before the dirty limits are breached and the dirty 1963 * data has expired. It can also happen when the proportion of 1964 * dirty pages grows not through writes but through memory 1965 * pressure reclaiming all the clean cache. And in some cases, 1966 * the flushers simply cannot keep up with the allocation 1967 * rate. Nudge the flusher threads in case they are asleep. 1968 */ 1969 if (stat.nr_unqueued_dirty == nr_taken) 1970 wakeup_flusher_threads(WB_REASON_VMSCAN); 1971 1972 sc->nr.dirty += stat.nr_dirty; 1973 sc->nr.congested += stat.nr_congested; 1974 sc->nr.unqueued_dirty += stat.nr_unqueued_dirty; 1975 sc->nr.writeback += stat.nr_writeback; 1976 sc->nr.immediate += stat.nr_immediate; 1977 sc->nr.taken += nr_taken; 1978 if (file) 1979 sc->nr.file_taken += nr_taken; 1980 1981 trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id, 1982 nr_scanned, nr_reclaimed, &stat, sc->priority, file); 1983 return nr_reclaimed; 1984 } 1985 1986 /* 1987 * This moves pages from the active list to the inactive list. 1988 * 1989 * We move them the other way if the page is referenced by one or more 1990 * processes, from rmap. 1991 * 1992 * If the pages are mostly unmapped, the processing is fast and it is 1993 * appropriate to hold pgdat->lru_lock across the whole operation. But if 1994 * the pages are mapped, the processing is slow (page_referenced()) so we 1995 * should drop pgdat->lru_lock around each page. It's impossible to balance 1996 * this, so instead we remove the pages from the LRU while processing them. 1997 * It is safe to rely on PG_active against the non-LRU pages in here because 1998 * nobody will play with that bit on a non-LRU page. 1999 * 2000 * The downside is that we have to touch page->_refcount against each page. 2001 * But we had to alter page->flags anyway. 2002 * 2003 * Returns the number of pages moved to the given lru. 2004 */ 2005 2006 static unsigned move_active_pages_to_lru(struct lruvec *lruvec, 2007 struct list_head *list, 2008 struct list_head *pages_to_free, 2009 enum lru_list lru) 2010 { 2011 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 2012 struct page *page; 2013 int nr_pages; 2014 int nr_moved = 0; 2015 2016 while (!list_empty(list)) { 2017 page = lru_to_page(list); 2018 lruvec = mem_cgroup_page_lruvec(page, pgdat); 2019 2020 VM_BUG_ON_PAGE(PageLRU(page), page); 2021 SetPageLRU(page); 2022 2023 nr_pages = hpage_nr_pages(page); 2024 update_lru_size(lruvec, lru, page_zonenum(page), nr_pages); 2025 list_move(&page->lru, &lruvec->lists[lru]); 2026 2027 if (put_page_testzero(page)) { 2028 __ClearPageLRU(page); 2029 __ClearPageActive(page); 2030 del_page_from_lru_list(page, lruvec, lru); 2031 2032 if (unlikely(PageCompound(page))) { 2033 spin_unlock_irq(&pgdat->lru_lock); 2034 mem_cgroup_uncharge(page); 2035 (*get_compound_page_dtor(page))(page); 2036 spin_lock_irq(&pgdat->lru_lock); 2037 } else 2038 list_add(&page->lru, pages_to_free); 2039 } else { 2040 nr_moved += nr_pages; 2041 } 2042 } 2043 2044 if (!is_active_lru(lru)) { 2045 __count_vm_events(PGDEACTIVATE, nr_moved); 2046 count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, 2047 nr_moved); 2048 } 2049 2050 return nr_moved; 2051 } 2052 2053 static void shrink_active_list(unsigned long nr_to_scan, 2054 struct lruvec *lruvec, 2055 struct scan_control *sc, 2056 enum lru_list lru) 2057 { 2058 unsigned long nr_taken; 2059 unsigned long nr_scanned; 2060 unsigned long vm_flags; 2061 LIST_HEAD(l_hold); /* The pages which were snipped off */ 2062 LIST_HEAD(l_active); 2063 LIST_HEAD(l_inactive); 2064 struct page *page; 2065 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; 2066 unsigned nr_deactivate, nr_activate; 2067 unsigned nr_rotated = 0; 2068 int file = is_file_lru(lru); 2069 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 2070 2071 lru_add_drain(); 2072 2073 spin_lock_irq(&pgdat->lru_lock); 2074 2075 nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold, 2076 &nr_scanned, sc, lru); 2077 2078 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken); 2079 reclaim_stat->recent_scanned[file] += nr_taken; 2080 2081 __count_vm_events(PGREFILL, nr_scanned); 2082 count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned); 2083 2084 spin_unlock_irq(&pgdat->lru_lock); 2085 2086 while (!list_empty(&l_hold)) { 2087 cond_resched(); 2088 page = lru_to_page(&l_hold); 2089 list_del(&page->lru); 2090 2091 if (unlikely(!page_evictable(page))) { 2092 putback_lru_page(page); 2093 continue; 2094 } 2095 2096 if (unlikely(buffer_heads_over_limit)) { 2097 if (page_has_private(page) && trylock_page(page)) { 2098 if (page_has_private(page)) 2099 try_to_release_page(page, 0); 2100 unlock_page(page); 2101 } 2102 } 2103 2104 if (page_referenced(page, 0, sc->target_mem_cgroup, 2105 &vm_flags)) { 2106 nr_rotated += hpage_nr_pages(page); 2107 /* 2108 * Identify referenced, file-backed active pages and 2109 * give them one more trip around the active list. So 2110 * that executable code get better chances to stay in 2111 * memory under moderate memory pressure. Anon pages 2112 * are not likely to be evicted by use-once streaming 2113 * IO, plus JVM can create lots of anon VM_EXEC pages, 2114 * so we ignore them here. 2115 */ 2116 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 2117 list_add(&page->lru, &l_active); 2118 continue; 2119 } 2120 } 2121 2122 ClearPageActive(page); /* we are de-activating */ 2123 SetPageWorkingset(page); 2124 list_add(&page->lru, &l_inactive); 2125 } 2126 2127 /* 2128 * Move pages back to the lru list. 2129 */ 2130 spin_lock_irq(&pgdat->lru_lock); 2131 /* 2132 * Count referenced pages from currently used mappings as rotated, 2133 * even though only some of them are actually re-activated. This 2134 * helps balance scan pressure between file and anonymous pages in 2135 * get_scan_count. 2136 */ 2137 reclaim_stat->recent_rotated[file] += nr_rotated; 2138 2139 nr_activate = move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru); 2140 nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE); 2141 __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); 2142 spin_unlock_irq(&pgdat->lru_lock); 2143 2144 mem_cgroup_uncharge_list(&l_hold); 2145 free_unref_page_list(&l_hold); 2146 trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate, 2147 nr_deactivate, nr_rotated, sc->priority, file); 2148 } 2149 2150 /* 2151 * The inactive anon list should be small enough that the VM never has 2152 * to do too much work. 2153 * 2154 * The inactive file list should be small enough to leave most memory 2155 * to the established workingset on the scan-resistant active list, 2156 * but large enough to avoid thrashing the aggregate readahead window. 2157 * 2158 * Both inactive lists should also be large enough that each inactive 2159 * page has a chance to be referenced again before it is reclaimed. 2160 * 2161 * If that fails and refaulting is observed, the inactive list grows. 2162 * 2163 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages 2164 * on this LRU, maintained by the pageout code. An inactive_ratio 2165 * of 3 means 3:1 or 25% of the pages are kept on the inactive list. 2166 * 2167 * total target max 2168 * memory ratio inactive 2169 * ------------------------------------- 2170 * 10MB 1 5MB 2171 * 100MB 1 50MB 2172 * 1GB 3 250MB 2173 * 10GB 10 0.9GB 2174 * 100GB 31 3GB 2175 * 1TB 101 10GB 2176 * 10TB 320 32GB 2177 */ 2178 static bool inactive_list_is_low(struct lruvec *lruvec, bool file, 2179 struct scan_control *sc, bool actual_reclaim) 2180 { 2181 enum lru_list active_lru = file * LRU_FILE + LRU_ACTIVE; 2182 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 2183 enum lru_list inactive_lru = file * LRU_FILE; 2184 unsigned long inactive, active; 2185 unsigned long inactive_ratio; 2186 unsigned long refaults; 2187 unsigned long gb; 2188 2189 /* 2190 * If we don't have swap space, anonymous page deactivation 2191 * is pointless. 2192 */ 2193 if (!file && !total_swap_pages) 2194 return false; 2195 2196 inactive = lruvec_lru_size(lruvec, inactive_lru, sc->reclaim_idx); 2197 active = lruvec_lru_size(lruvec, active_lru, sc->reclaim_idx); 2198 2199 /* 2200 * When refaults are being observed, it means a new workingset 2201 * is being established. Disable active list protection to get 2202 * rid of the stale workingset quickly. 2203 */ 2204 refaults = lruvec_page_state(lruvec, WORKINGSET_ACTIVATE); 2205 if (file && actual_reclaim && lruvec->refaults != refaults) { 2206 inactive_ratio = 0; 2207 } else { 2208 gb = (inactive + active) >> (30 - PAGE_SHIFT); 2209 if (gb) 2210 inactive_ratio = int_sqrt(10 * gb); 2211 else 2212 inactive_ratio = 1; 2213 } 2214 2215 if (actual_reclaim) 2216 trace_mm_vmscan_inactive_list_is_low(pgdat->node_id, sc->reclaim_idx, 2217 lruvec_lru_size(lruvec, inactive_lru, MAX_NR_ZONES), inactive, 2218 lruvec_lru_size(lruvec, active_lru, MAX_NR_ZONES), active, 2219 inactive_ratio, file); 2220 2221 return inactive * inactive_ratio < active; 2222 } 2223 2224 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 2225 struct lruvec *lruvec, struct scan_control *sc) 2226 { 2227 if (is_active_lru(lru)) { 2228 if (inactive_list_is_low(lruvec, is_file_lru(lru), sc, true)) 2229 shrink_active_list(nr_to_scan, lruvec, sc, lru); 2230 return 0; 2231 } 2232 2233 return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); 2234 } 2235 2236 enum scan_balance { 2237 SCAN_EQUAL, 2238 SCAN_FRACT, 2239 SCAN_ANON, 2240 SCAN_FILE, 2241 }; 2242 2243 /* 2244 * Determine how aggressively the anon and file LRU lists should be 2245 * scanned. The relative value of each set of LRU lists is determined 2246 * by looking at the fraction of the pages scanned we did rotate back 2247 * onto the active list instead of evict. 2248 * 2249 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan 2250 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan 2251 */ 2252 static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg, 2253 struct scan_control *sc, unsigned long *nr, 2254 unsigned long *lru_pages) 2255 { 2256 int swappiness = mem_cgroup_swappiness(memcg); 2257 struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; 2258 u64 fraction[2]; 2259 u64 denominator = 0; /* gcc */ 2260 struct pglist_data *pgdat = lruvec_pgdat(lruvec); 2261 unsigned long anon_prio, file_prio; 2262 enum scan_balance scan_balance; 2263 unsigned long anon, file; 2264 unsigned long ap, fp; 2265 enum lru_list lru; 2266 2267 /* If we have no swap space, do not bother scanning anon pages. */ 2268 if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) { 2269 scan_balance = SCAN_FILE; 2270 goto out; 2271 } 2272 2273 /* 2274 * Global reclaim will swap to prevent OOM even with no 2275 * swappiness, but memcg users want to use this knob to 2276 * disable swapping for individual groups completely when 2277 * using the memory controller's swap limit feature would be 2278 * too expensive. 2279 */ 2280 if (!global_reclaim(sc) && !swappiness) { 2281 scan_balance = SCAN_FILE; 2282 goto out; 2283 } 2284 2285 /* 2286 * Do not apply any pressure balancing cleverness when the 2287 * system is close to OOM, scan both anon and file equally 2288 * (unless the swappiness setting disagrees with swapping). 2289 */ 2290 if (!sc->priority && swappiness) { 2291 scan_balance = SCAN_EQUAL; 2292 goto out; 2293 } 2294 2295 /* 2296 * Prevent the reclaimer from falling into the cache trap: as 2297 * cache pages start out inactive, every cache fault will tip 2298 * the scan balance towards the file LRU. And as the file LRU 2299 * shrinks, so does the window for rotation from references. 2300 * This means we have a runaway feedback loop where a tiny 2301 * thrashing file LRU becomes infinitely more attractive than 2302 * anon pages. Try to detect this based on file LRU size. 2303 */ 2304 if (global_reclaim(sc)) { 2305 unsigned long pgdatfile; 2306 unsigned long pgdatfree; 2307 int z; 2308 unsigned long total_high_wmark = 0; 2309 2310 pgdatfree = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES); 2311 pgdatfile = node_page_state(pgdat, NR_ACTIVE_FILE) + 2312 node_page_state(pgdat, NR_INACTIVE_FILE); 2313 2314 for (z = 0; z < MAX_NR_ZONES; z++) { 2315 struct zone *zone = &pgdat->node_zones[z]; 2316 if (!managed_zone(zone)) 2317 continue; 2318 2319 total_high_wmark += high_wmark_pages(zone); 2320 } 2321 2322 if (unlikely(pgdatfile + pgdatfree <= total_high_wmark)) { 2323 /* 2324 * Force SCAN_ANON if there are enough inactive 2325 * anonymous pages on the LRU in eligible zones. 2326 * Otherwise, the small LRU gets thrashed. 2327 */ 2328 if (!inactive_list_is_low(lruvec, false, sc, false) && 2329 lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, sc->reclaim_idx) 2330 >> sc->priority) { 2331 scan_balance = SCAN_ANON; 2332 goto out; 2333 } 2334 } 2335 } 2336 2337 /* 2338 * If there is enough inactive page cache, i.e. if the size of the 2339 * inactive list is greater than that of the active list *and* the 2340 * inactive list actually has some pages to scan on this priority, we 2341 * do not reclaim anything from the anonymous working set right now. 2342 * Without the second condition we could end up never scanning an 2343 * lruvec even if it has plenty of old anonymous pages unless the 2344 * system is under heavy pressure. 2345 */ 2346 if (!inactive_list_is_low(lruvec, true, sc, false) && 2347 lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, sc->reclaim_idx) >> sc->priority) { 2348 scan_balance = SCAN_FILE; 2349 goto out; 2350 } 2351 2352 scan_balance = SCAN_FRACT; 2353 2354 /* 2355 * With swappiness at 100, anonymous and file have the same priority. 2356 * This scanning priority is essentially the inverse of IO cost. 2357 */ 2358 anon_prio = swappiness; 2359 file_prio = 200 - anon_prio; 2360 2361 /* 2362 * OK, so we have swap space and a fair amount of page cache 2363 * pages. We use the recently rotated / recently scanned 2364 * ratios to determine how valuable each cache is. 2365 * 2366 * Because workloads change over time (and to avoid overflow) 2367 * we keep these statistics as a floating average, which ends 2368 * up weighing recent references more than old ones. 2369 * 2370 * anon in [0], file in [1] 2371 */ 2372 2373 anon = lruvec_lru_size(lruvec, LRU_ACTIVE_ANON, MAX_NR_ZONES) + 2374 lruvec_lru_size(lruvec, LRU_INACTIVE_ANON, MAX_NR_ZONES); 2375 file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE, MAX_NR_ZONES) + 2376 lruvec_lru_size(lruvec, LRU_INACTIVE_FILE, MAX_NR_ZONES); 2377 2378 spin_lock_irq(&pgdat->lru_lock); 2379 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 2380 reclaim_stat->recent_scanned[0] /= 2; 2381 reclaim_stat->recent_rotated[0] /= 2; 2382 } 2383 2384 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 2385 reclaim_stat->recent_scanned[1] /= 2; 2386 reclaim_stat->recent_rotated[1] /= 2; 2387 } 2388 2389 /* 2390 * The amount of pressure on anon vs file pages is inversely 2391 * proportional to the fraction of recently scanned pages on 2392 * each list that were recently referenced and in active use. 2393 */ 2394 ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1); 2395 ap /= reclaim_stat->recent_rotated[0] + 1; 2396 2397 fp = file_prio * (reclaim_stat->recent_scanned[1] + 1); 2398 fp /= reclaim_stat->recent_rotated[1] + 1; 2399 spin_unlock_irq(&pgdat->lru_lock); 2400 2401 fraction[0] = ap; 2402 fraction[1] = fp; 2403 denominator = ap + fp + 1; 2404 out: 2405 *lru_pages = 0; 2406 for_each_evictable_lru(lru) { 2407 int file = is_file_lru(lru); 2408 unsigned long size; 2409 unsigned long scan; 2410 2411 size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx); 2412 scan = size >> sc->priority; 2413 /* 2414 * If the cgroup's already been deleted, make sure to 2415 * scrape out the remaining cache. 2416 */ 2417 if (!scan && !mem_cgroup_online(memcg)) 2418 scan = min(size, SWAP_CLUSTER_MAX); 2419 2420 switch (scan_balance) { 2421 case SCAN_EQUAL: 2422 /* Scan lists relative to size */ 2423 break; 2424 case SCAN_FRACT: 2425 /* 2426 * Scan types proportional to swappiness and 2427 * their relative recent reclaim efficiency. 2428 * Make sure we don't miss the last page 2429 * because of a round-off error. 2430 */ 2431 scan = DIV64_U64_ROUND_UP(scan * fraction[file], 2432 denominator); 2433 break; 2434 case SCAN_FILE: 2435 case SCAN_ANON: 2436 /* Scan one type exclusively */ 2437 if ((scan_balance == SCAN_FILE) != file) { 2438 size = 0; 2439 scan = 0; 2440 } 2441 break; 2442 default: 2443 /* Look ma, no brain */ 2444 BUG(); 2445 } 2446 2447 *lru_pages += size; 2448 nr[lru] = scan; 2449 } 2450 } 2451 2452 /* 2453 * This is a basic per-node page freer. Used by both kswapd and direct reclaim. 2454 */ 2455 static void shrink_node_memcg(struct pglist_data *pgdat, struct mem_cgroup *memcg, 2456 struct scan_control *sc, unsigned long *lru_pages) 2457 { 2458 struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg); 2459 unsigned long nr[NR_LRU_LISTS]; 2460 unsigned long targets[NR_LRU_LISTS]; 2461 unsigned long nr_to_scan; 2462 enum lru_list lru; 2463 unsigned long nr_reclaimed = 0; 2464 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 2465 struct blk_plug plug; 2466 bool scan_adjusted; 2467 2468 get_scan_count(lruvec, memcg, sc, nr, lru_pages); 2469 2470 /* Record the original scan target for proportional adjustments later */ 2471 memcpy(targets, nr, sizeof(nr)); 2472 2473 /* 2474 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal 2475 * event that can occur when there is little memory pressure e.g. 2476 * multiple streaming readers/writers. Hence, we do not abort scanning 2477 * when the requested number of pages are reclaimed when scanning at 2478 * DEF_PRIORITY on the assumption that the fact we are direct 2479 * reclaiming implies that kswapd is not keeping up and it is best to 2480 * do a batch of work at once. For memcg reclaim one check is made to 2481 * abort proportional reclaim if either the file or anon lru has already 2482 * dropped to zero at the first pass. 2483 */ 2484 scan_adjusted = (global_reclaim(sc) && !current_is_kswapd() && 2485 sc->priority == DEF_PRIORITY); 2486 2487 blk_start_plug(&plug); 2488 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 2489 nr[LRU_INACTIVE_FILE]) { 2490 unsigned long nr_anon, nr_file, percentage; 2491 unsigned long nr_scanned; 2492 2493 for_each_evictable_lru(lru) { 2494 if (nr[lru]) { 2495 nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); 2496 nr[lru] -= nr_to_scan; 2497 2498 nr_reclaimed += shrink_list(lru, nr_to_scan, 2499 lruvec, sc); 2500 } 2501 } 2502 2503 cond_resched(); 2504 2505 if (nr_reclaimed < nr_to_reclaim || scan_adjusted) 2506 continue; 2507 2508 /* 2509 * For kswapd and memcg, reclaim at least the number of pages 2510 * requested. Ensure that the anon and file LRUs are scanned 2511 * proportionally what was requested by get_scan_count(). We 2512 * stop reclaiming one LRU and reduce the amount scanning 2513 * proportional to the original scan target. 2514 */ 2515 nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; 2516 nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; 2517 2518 /* 2519 * It's just vindictive to attack the larger once the smaller 2520 * has gone to zero. And given the way we stop scanning the 2521 * smaller below, this makes sure that we only make one nudge 2522 * towards proportionality once we've got nr_to_reclaim. 2523 */ 2524 if (!nr_file || !nr_anon) 2525 break; 2526 2527 if (nr_file > nr_anon) { 2528 unsigned long scan_target = targets[LRU_INACTIVE_ANON] + 2529 targets[LRU_ACTIVE_ANON] + 1; 2530 lru = LRU_BASE; 2531 percentage = nr_anon * 100 / scan_target; 2532 } else { 2533 unsigned long scan_target = targets[LRU_INACTIVE_FILE] + 2534 targets[LRU_ACTIVE_FILE] + 1; 2535 lru = LRU_FILE; 2536 percentage = nr_file * 100 / scan_target; 2537 } 2538 2539 /* Stop scanning the smaller of the LRU */ 2540 nr[lru] = 0; 2541 nr[lru + LRU_ACTIVE] = 0; 2542 2543 /* 2544 * Recalculate the other LRU scan count based on its original 2545 * scan target and the percentage scanning already complete 2546 */ 2547 lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; 2548 nr_scanned = targets[lru] - nr[lru]; 2549 nr[lru] = targets[lru] * (100 - percentage) / 100; 2550 nr[lru] -= min(nr[lru], nr_scanned); 2551 2552 lru += LRU_ACTIVE; 2553 nr_scanned = targets[lru] - nr[lru]; 2554 nr[lru] = targets[lru] * (100 - percentage) / 100; 2555 nr[lru] -= min(nr[lru], nr_scanned); 2556 2557 scan_adjusted = true; 2558 } 2559 blk_finish_plug(&plug); 2560 sc->nr_reclaimed += nr_reclaimed; 2561 2562 /* 2563 * Even if we did not try to evict anon pages at all, we want to 2564 * rebalance the anon lru active/inactive ratio. 2565 */ 2566 if (inactive_list_is_low(lruvec, false, sc, true)) 2567 shrink_active_list(SWAP_CLUSTER_MAX, lruvec, 2568 sc, LRU_ACTIVE_ANON); 2569 } 2570 2571 /* Use reclaim/compaction for costly allocs or under memory pressure */ 2572 static bool in_reclaim_compaction(struct scan_control *sc) 2573 { 2574 if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && 2575 (sc->order > PAGE_ALLOC_COSTLY_ORDER || 2576 sc->priority < DEF_PRIORITY - 2)) 2577 return true; 2578 2579 return false; 2580 } 2581 2582 /* 2583 * Reclaim/compaction is used for high-order allocation requests. It reclaims 2584 * order-0 pages before compacting the zone. should_continue_reclaim() returns 2585 * true if more pages should be reclaimed such that when the page allocator 2586 * calls try_to_compact_zone() that it will have enough free pages to succeed. 2587 * It will give up earlier than that if there is difficulty reclaiming pages. 2588 */ 2589 static inline bool should_continue_reclaim(struct pglist_data *pgdat, 2590 unsigned long nr_reclaimed, 2591 unsigned long nr_scanned, 2592 struct scan_control *sc) 2593 { 2594 unsigned long pages_for_compaction; 2595 unsigned long inactive_lru_pages; 2596 int z; 2597 2598 /* If not in reclaim/compaction mode, stop */ 2599 if (!in_reclaim_compaction(sc)) 2600 return false; 2601 2602 /* Consider stopping depending on scan and reclaim activity */ 2603 if (sc->gfp_mask & __GFP_RETRY_MAYFAIL) { 2604 /* 2605 * For __GFP_RETRY_MAYFAIL allocations, stop reclaiming if the 2606 * full LRU list has been scanned and we are still failing 2607 * to reclaim pages. This full LRU scan is potentially 2608 * expensive but a __GFP_RETRY_MAYFAIL caller really wants to succeed 2609 */ 2610 if (!nr_reclaimed && !nr_scanned) 2611 return false; 2612 } else { 2613 /* 2614 * For non-__GFP_RETRY_MAYFAIL allocations which can presumably 2615 * fail without consequence, stop if we failed to reclaim 2616 * any pages from the last SWAP_CLUSTER_MAX number of 2617 * pages that were scanned. This will return to the 2618 * caller faster at the risk reclaim/compaction and 2619 * the resulting allocation attempt fails 2620 */ 2621 if (!nr_reclaimed) 2622 return false; 2623 } 2624 2625 /* 2626 * If we have not reclaimed enough pages for compaction and the 2627 * inactive lists are large enough, continue reclaiming 2628 */ 2629 pages_for_compaction = compact_gap(sc->order); 2630 inactive_lru_pages = node_page_state(pgdat, NR_INACTIVE_FILE); 2631 if (get_nr_swap_pages() > 0) 2632 inactive_lru_pages += node_page_state(pgdat, NR_INACTIVE_ANON); 2633 if (sc->nr_reclaimed < pages_for_compaction && 2634 inactive_lru_pages > pages_for_compaction) 2635 return true; 2636 2637 /* If compaction would go ahead or the allocation would succeed, stop */ 2638 for (z = 0; z <= sc->reclaim_idx; z++) { 2639 struct zone *zone = &pgdat->node_zones[z]; 2640 if (!managed_zone(zone)) 2641 continue; 2642 2643 switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) { 2644 case COMPACT_SUCCESS: 2645 case COMPACT_CONTINUE: 2646 return false; 2647 default: 2648 /* check next zone */ 2649 ; 2650 } 2651 } 2652 return true; 2653 } 2654 2655 static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg) 2656 { 2657 return test_bit(PGDAT_CONGESTED, &pgdat->flags) || 2658 (memcg && memcg_congested(pgdat, memcg)); 2659 } 2660 2661 static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc) 2662 { 2663 struct reclaim_state *reclaim_state = current->reclaim_state; 2664 unsigned long nr_reclaimed, nr_scanned; 2665 bool reclaimable = false; 2666 2667 do { 2668 struct mem_cgroup *root = sc->target_mem_cgroup; 2669 struct mem_cgroup_reclaim_cookie reclaim = { 2670 .pgdat = pgdat, 2671 .priority = sc->priority, 2672 }; 2673 unsigned long node_lru_pages = 0; 2674 struct mem_cgroup *memcg; 2675 2676 memset(&sc->nr, 0, sizeof(sc->nr)); 2677 2678 nr_reclaimed = sc->nr_reclaimed; 2679 nr_scanned = sc->nr_scanned; 2680 2681 memcg = mem_cgroup_iter(root, NULL, &reclaim); 2682 do { 2683 unsigned long lru_pages; 2684 unsigned long reclaimed; 2685 unsigned long scanned; 2686 2687 switch (mem_cgroup_protected(root, memcg)) { 2688 case MEMCG_PROT_MIN: 2689 /* 2690 * Hard protection. 2691 * If there is no reclaimable memory, OOM. 2692 */ 2693 continue; 2694 case MEMCG_PROT_LOW: 2695 /* 2696 * Soft protection. 2697 * Respect the protection only as long as 2698 * there is an unprotected supply 2699 * of reclaimable memory from other cgroups. 2700 */ 2701 if (!sc->memcg_low_reclaim) { 2702 sc->memcg_low_skipped = 1; 2703 continue; 2704 } 2705 memcg_memory_event(memcg, MEMCG_LOW); 2706 break; 2707 case MEMCG_PROT_NONE: 2708 break; 2709 } 2710 2711 reclaimed = sc->nr_reclaimed; 2712 scanned = sc->nr_scanned; 2713 shrink_node_memcg(pgdat, memcg, sc, &lru_pages); 2714 node_lru_pages += lru_pages; 2715 2716 if (sc->may_shrinkslab) { 2717 shrink_slab(sc->gfp_mask, pgdat->node_id, 2718 memcg, sc->priority); 2719 } 2720 2721 /* Record the group's reclaim efficiency */ 2722 vmpressure(sc->gfp_mask, memcg, false, 2723 sc->nr_scanned - scanned, 2724 sc->nr_reclaimed - reclaimed); 2725 2726 /* 2727 * Kswapd have to scan all memory cgroups to fulfill 2728 * the overall scan target for the node. 2729 * 2730 * Limit reclaim, on the other hand, only cares about 2731 * nr_to_reclaim pages to be reclaimed and it will 2732 * retry with decreasing priority if one round over the 2733 * whole hierarchy is not sufficient. 2734 */ 2735 if (!current_is_kswapd() && 2736 sc->nr_reclaimed >= sc->nr_to_reclaim) { 2737 mem_cgroup_iter_break(root, memcg); 2738 break; 2739 } 2740 } while ((memcg = mem_cgroup_iter(root, memcg, &reclaim))); 2741 2742 if (reclaim_state) { 2743 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2744 reclaim_state->reclaimed_slab = 0; 2745 } 2746 2747 /* Record the subtree's reclaim efficiency */ 2748 vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true, 2749 sc->nr_scanned - nr_scanned, 2750 sc->nr_reclaimed - nr_reclaimed); 2751 2752 if (sc->nr_reclaimed - nr_reclaimed) 2753 reclaimable = true; 2754 2755 if (current_is_kswapd()) { 2756 /* 2757 * If reclaim is isolating dirty pages under writeback, 2758 * it implies that the long-lived page allocation rate 2759 * is exceeding the page laundering rate. Either the 2760 * global limits are not being effective at throttling 2761 * processes due to the page distribution throughout 2762 * zones or there is heavy usage of a slow backing 2763 * device. The only option is to throttle from reclaim 2764 * context which is not ideal as there is no guarantee 2765 * the dirtying process is throttled in the same way 2766 * balance_dirty_pages() manages. 2767 * 2768 * Once a node is flagged PGDAT_WRITEBACK, kswapd will 2769 * count the number of pages under pages flagged for 2770 * immediate reclaim and stall if any are encountered 2771 * in the nr_immediate check below. 2772 */ 2773 if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken) 2774 set_bit(PGDAT_WRITEBACK, &pgdat->flags); 2775 2776 /* 2777 * Tag a node as congested if all the dirty pages 2778 * scanned were backed by a congested BDI and 2779 * wait_iff_congested will stall. 2780 */ 2781 if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested) 2782 set_bit(PGDAT_CONGESTED, &pgdat->flags); 2783 2784 /* Allow kswapd to start writing pages during reclaim.*/ 2785 if (sc->nr.unqueued_dirty == sc->nr.file_taken) 2786 set_bit(PGDAT_DIRTY, &pgdat->flags); 2787 2788 /* 2789 * If kswapd scans pages marked marked for immediate 2790 * reclaim and under writeback (nr_immediate), it 2791 * implies that pages are cycling through the LRU 2792 * faster than they are written so also forcibly stall. 2793 */ 2794 if (sc->nr.immediate) 2795 congestion_wait(BLK_RW_ASYNC, HZ/10); 2796 } 2797 2798 /* 2799 * Legacy memcg will stall in page writeback so avoid forcibly 2800 * stalling in wait_iff_congested(). 2801 */ 2802 if (!global_reclaim(sc) && sane_reclaim(sc) && 2803 sc->nr.dirty && sc->nr.dirty == sc->nr.congested) 2804 set_memcg_congestion(pgdat, root, true); 2805 2806 /* 2807 * Stall direct reclaim for IO completions if underlying BDIs 2808 * and node is congested. Allow kswapd to continue until it 2809 * starts encountering unqueued dirty pages or cycling through 2810 * the LRU too quickly. 2811 */ 2812 if (!sc->hibernation_mode && !current_is_kswapd() && 2813 current_may_throttle() && pgdat_memcg_congested(pgdat, root)) 2814 wait_iff_congested(BLK_RW_ASYNC, HZ/10); 2815 2816 } while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed, 2817 sc->nr_scanned - nr_scanned, sc)); 2818 2819 /* 2820 * Kswapd gives up on balancing particular nodes after too 2821 * many failures to reclaim anything from them and goes to 2822 * sleep. On reclaim progress, reset the failure counter. A 2823 * successful direct reclaim run will revive a dormant kswapd. 2824 */ 2825 if (reclaimable) 2826 pgdat->kswapd_failures = 0; 2827 2828 return reclaimable; 2829 } 2830 2831 /* 2832 * Returns true if compaction should go ahead for a costly-order request, or 2833 * the allocation would already succeed without compaction. Return false if we 2834 * should reclaim first. 2835 */ 2836 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) 2837 { 2838 unsigned long watermark; 2839 enum compact_result suitable; 2840 2841 suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx); 2842 if (suitable == COMPACT_SUCCESS) 2843 /* Allocation should succeed already. Don't reclaim. */ 2844 return true; 2845 if (suitable == COMPACT_SKIPPED) 2846 /* Compaction cannot yet proceed. Do reclaim. */ 2847 return false; 2848 2849 /* 2850 * Compaction is already possible, but it takes time to run and there 2851 * are potentially other callers using the pages just freed. So proceed 2852 * with reclaim to make a buffer of free pages available to give 2853 * compaction a reasonable chance of completing and allocating the page. 2854 * Note that we won't actually reclaim the whole buffer in one attempt 2855 * as the target watermark in should_continue_reclaim() is lower. But if 2856 * we are already above the high+gap watermark, don't reclaim at all. 2857 */ 2858 watermark = high_wmark_pages(zone) + compact_gap(sc->order); 2859 2860 return zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx); 2861 } 2862 2863 /* 2864 * This is the direct reclaim path, for page-allocating processes. We only 2865 * try to reclaim pages from zones which will satisfy the caller's allocation 2866 * request. 2867 * 2868 * If a zone is deemed to be full of pinned pages then just give it a light 2869 * scan then give up on it. 2870 */ 2871 static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc) 2872 { 2873 struct zoneref *z; 2874 struct zone *zone; 2875 unsigned long nr_soft_reclaimed; 2876 unsigned long nr_soft_scanned; 2877 gfp_t orig_mask; 2878 pg_data_t *last_pgdat = NULL; 2879 2880 /* 2881 * If the number of buffer_heads in the machine exceeds the maximum 2882 * allowed level, force direct reclaim to scan the highmem zone as 2883 * highmem pages could be pinning lowmem pages storing buffer_heads 2884 */ 2885 orig_mask = sc->gfp_mask; 2886 if (buffer_heads_over_limit) { 2887 sc->gfp_mask |= __GFP_HIGHMEM; 2888 sc->reclaim_idx = gfp_zone(sc->gfp_mask); 2889 } 2890 2891 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2892 sc->reclaim_idx, sc->nodemask) { 2893 /* 2894 * Take care memory controller reclaiming has small influence 2895 * to global LRU. 2896 */ 2897 if (global_reclaim(sc)) { 2898 if (!cpuset_zone_allowed(zone, 2899 GFP_KERNEL | __GFP_HARDWALL)) 2900 continue; 2901 2902 /* 2903 * If we already have plenty of memory free for 2904 * compaction in this zone, don't free any more. 2905 * Even though compaction is invoked for any 2906 * non-zero order, only frequent costly order 2907 * reclamation is disruptive enough to become a 2908 * noticeable problem, like transparent huge 2909 * page allocations. 2910 */ 2911 if (IS_ENABLED(CONFIG_COMPACTION) && 2912 sc->order > PAGE_ALLOC_COSTLY_ORDER && 2913 compaction_ready(zone, sc)) { 2914 sc->compaction_ready = true; 2915 continue; 2916 } 2917 2918 /* 2919 * Shrink each node in the zonelist once. If the 2920 * zonelist is ordered by zone (not the default) then a 2921 * node may be shrunk multiple times but in that case 2922 * the user prefers lower zones being preserved. 2923 */ 2924 if (zone->zone_pgdat == last_pgdat) 2925 continue; 2926 2927 /* 2928 * This steals pages from memory cgroups over softlimit 2929 * and returns the number of reclaimed pages and 2930 * scanned pages. This works for global memory pressure 2931 * and balancing, not for a memcg's limit. 2932 */ 2933 nr_soft_scanned = 0; 2934 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone->zone_pgdat, 2935 sc->order, sc->gfp_mask, 2936 &nr_soft_scanned); 2937 sc->nr_reclaimed += nr_soft_reclaimed; 2938 sc->nr_scanned += nr_soft_scanned; 2939 /* need some check for avoid more shrink_zone() */ 2940 } 2941 2942 /* See comment about same check for global reclaim above */ 2943 if (zone->zone_pgdat == last_pgdat) 2944 continue; 2945 last_pgdat = zone->zone_pgdat; 2946 shrink_node(zone->zone_pgdat, sc); 2947 } 2948 2949 /* 2950 * Restore to original mask to avoid the impact on the caller if we 2951 * promoted it to __GFP_HIGHMEM. 2952 */ 2953 sc->gfp_mask = orig_mask; 2954 } 2955 2956 static void snapshot_refaults(struct mem_cgroup *root_memcg, pg_data_t *pgdat) 2957 { 2958 struct mem_cgroup *memcg; 2959 2960 memcg = mem_cgroup_iter(root_memcg, NULL, NULL); 2961 do { 2962 unsigned long refaults; 2963 struct lruvec *lruvec; 2964 2965 lruvec = mem_cgroup_lruvec(pgdat, memcg); 2966 refaults = lruvec_page_state(lruvec, WORKINGSET_ACTIVATE); 2967 lruvec->refaults = refaults; 2968 } while ((memcg = mem_cgroup_iter(root_memcg, memcg, NULL))); 2969 } 2970 2971 /* 2972 * This is the main entry point to direct page reclaim. 2973 * 2974 * If a full scan of the inactive list fails to free enough memory then we 2975 * are "out of memory" and something needs to be killed. 2976 * 2977 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2978 * high - the zone may be full of dirty or under-writeback pages, which this 2979 * caller can't do much about. We kick the writeback threads and take explicit 2980 * naps in the hope that some of these pages can be written. But if the 2981 * allocating task holds filesystem locks which prevent writeout this might not 2982 * work, and the allocation attempt will fail. 2983 * 2984 * returns: 0, if no pages reclaimed 2985 * else, the number of pages reclaimed 2986 */ 2987 static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2988 struct scan_control *sc) 2989 { 2990 int initial_priority = sc->priority; 2991 pg_data_t *last_pgdat; 2992 struct zoneref *z; 2993 struct zone *zone; 2994 retry: 2995 delayacct_freepages_start(); 2996 2997 if (global_reclaim(sc)) 2998 __count_zid_vm_events(ALLOCSTALL, sc->reclaim_idx, 1); 2999 3000 do { 3001 vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, 3002 sc->priority); 3003 sc->nr_scanned = 0; 3004 shrink_zones(zonelist, sc); 3005 3006 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 3007 break; 3008 3009 if (sc->compaction_ready) 3010 break; 3011 3012 /* 3013 * If we're getting trouble reclaiming, start doing 3014 * writepage even in laptop mode. 3015 */ 3016 if (sc->priority < DEF_PRIORITY - 2) 3017 sc->may_writepage = 1; 3018 } while (--sc->priority >= 0); 3019 3020 last_pgdat = NULL; 3021 for_each_zone_zonelist_nodemask(zone, z, zonelist, sc->reclaim_idx, 3022 sc->nodemask) { 3023 if (zone->zone_pgdat == last_pgdat) 3024 continue; 3025 last_pgdat = zone->zone_pgdat; 3026 snapshot_refaults(sc->target_mem_cgroup, zone->zone_pgdat); 3027 set_memcg_congestion(last_pgdat, sc->target_mem_cgroup, false); 3028 } 3029 3030 delayacct_freepages_end(); 3031 3032 if (sc->nr_reclaimed) 3033 return sc->nr_reclaimed; 3034 3035 /* Aborted reclaim to try compaction? don't OOM, then */ 3036 if (sc->compaction_ready) 3037 return 1; 3038 3039 /* Untapped cgroup reserves? Don't OOM, retry. */ 3040 if (sc->memcg_low_skipped) { 3041 sc->priority = initial_priority; 3042 sc->memcg_low_reclaim = 1; 3043 sc->memcg_low_skipped = 0; 3044 goto retry; 3045 } 3046 3047 return 0; 3048 } 3049 3050 static bool allow_direct_reclaim(pg_data_t *pgdat) 3051 { 3052 struct zone *zone; 3053 unsigned long pfmemalloc_reserve = 0; 3054 unsigned long free_pages = 0; 3055 int i; 3056 bool wmark_ok; 3057 3058 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) 3059 return true; 3060 3061 for (i = 0; i <= ZONE_NORMAL; i++) { 3062 zone = &pgdat->node_zones[i]; 3063 if (!managed_zone(zone)) 3064 continue; 3065 3066 if (!zone_reclaimable_pages(zone)) 3067 continue; 3068 3069 pfmemalloc_reserve += min_wmark_pages(zone); 3070 free_pages += zone_page_state(zone, NR_FREE_PAGES); 3071 } 3072 3073 /* If there are no reserves (unexpected config) then do not throttle */ 3074 if (!pfmemalloc_reserve) 3075 return true; 3076 3077 wmark_ok = free_pages > pfmemalloc_reserve / 2; 3078 3079 /* kswapd must be awake if processes are being throttled */ 3080 if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) { 3081 pgdat->kswapd_classzone_idx = min(pgdat->kswapd_classzone_idx, 3082 (enum zone_type)ZONE_NORMAL); 3083 wake_up_interruptible(&pgdat->kswapd_wait); 3084 } 3085 3086 return wmark_ok; 3087 } 3088 3089 /* 3090 * Throttle direct reclaimers if backing storage is backed by the network 3091 * and the PFMEMALLOC reserve for the preferred node is getting dangerously 3092 * depleted. kswapd will continue to make progress and wake the processes 3093 * when the low watermark is reached. 3094 * 3095 * Returns true if a fatal signal was delivered during throttling. If this 3096 * happens, the page allocator should not consider triggering the OOM killer. 3097 */ 3098 static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, 3099 nodemask_t *nodemask) 3100 { 3101 struct zoneref *z; 3102 struct zone *zone; 3103 pg_data_t *pgdat = NULL; 3104 3105 /* 3106 * Kernel threads should not be throttled as they may be indirectly 3107 * responsible for cleaning pages necessary for reclaim to make forward 3108 * progress. kjournald for example may enter direct reclaim while 3109 * committing a transaction where throttling it could forcing other 3110 * processes to block on log_wait_commit(). 3111 */ 3112 if (current->flags & PF_KTHREAD) 3113 goto out; 3114 3115 /* 3116 * If a fatal signal is pending, this process should not throttle. 3117 * It should return quickly so it can exit and free its memory 3118 */ 3119 if (fatal_signal_pending(current)) 3120 goto out; 3121 3122 /* 3123 * Check if the pfmemalloc reserves are ok by finding the first node 3124 * with a usable ZONE_NORMAL or lower zone. The expectation is that 3125 * GFP_KERNEL will be required for allocating network buffers when 3126 * swapping over the network so ZONE_HIGHMEM is unusable. 3127 * 3128 * Throttling is based on the first usable node and throttled processes 3129 * wait on a queue until kswapd makes progress and wakes them. There 3130 * is an affinity then between processes waking up and where reclaim 3131 * progress has been made assuming the process wakes on the same node. 3132 * More importantly, processes running on remote nodes will not compete 3133 * for remote pfmemalloc reserves and processes on different nodes 3134 * should make reasonable progress. 3135 */ 3136 for_each_zone_zonelist_nodemask(zone, z, zonelist, 3137 gfp_zone(gfp_mask), nodemask) { 3138 if (zone_idx(zone) > ZONE_NORMAL) 3139 continue; 3140 3141 /* Throttle based on the first usable node */ 3142 pgdat = zone->zone_pgdat; 3143 if (allow_direct_reclaim(pgdat)) 3144 goto out; 3145 break; 3146 } 3147 3148 /* If no zone was usable by the allocation flags then do not throttle */ 3149 if (!pgdat) 3150 goto out; 3151 3152 /* Account for the throttling */ 3153 count_vm_event(PGSCAN_DIRECT_THROTTLE); 3154 3155 /* 3156 * If the caller cannot enter the filesystem, it's possible that it 3157 * is due to the caller holding an FS lock or performing a journal 3158 * transaction in the case of a filesystem like ext[3|4]. In this case, 3159 * it is not safe to block on pfmemalloc_wait as kswapd could be 3160 * blocked waiting on the same lock. Instead, throttle for up to a 3161 * second before continuing. 3162 */ 3163 if (!(gfp_mask & __GFP_FS)) { 3164 wait_event_interruptible_timeout(pgdat->pfmemalloc_wait, 3165 allow_direct_reclaim(pgdat), HZ); 3166 3167 goto check_pending; 3168 } 3169 3170 /* Throttle until kswapd wakes the process */ 3171 wait_event_killable(zone->zone_pgdat->pfmemalloc_wait, 3172 allow_direct_reclaim(pgdat)); 3173 3174 check_pending: 3175 if (fatal_signal_pending(current)) 3176 return true; 3177 3178 out: 3179 return false; 3180 } 3181 3182 unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 3183 gfp_t gfp_mask, nodemask_t *nodemask) 3184 { 3185 unsigned long nr_reclaimed; 3186 struct scan_control sc = { 3187 .nr_to_reclaim = SWAP_CLUSTER_MAX, 3188 .gfp_mask = current_gfp_context(gfp_mask), 3189 .reclaim_idx = gfp_zone(gfp_mask), 3190 .order = order, 3191 .nodemask = nodemask, 3192 .priority = DEF_PRIORITY, 3193 .may_writepage = !laptop_mode, 3194 .may_unmap = 1, 3195 .may_swap = 1, 3196 .may_shrinkslab = 1, 3197 }; 3198 3199 /* 3200 * scan_control uses s8 fields for order, priority, and reclaim_idx. 3201 * Confirm they are large enough for max values. 3202 */ 3203 BUILD_BUG_ON(MAX_ORDER > S8_MAX); 3204 BUILD_BUG_ON(DEF_PRIORITY > S8_MAX); 3205 BUILD_BUG_ON(MAX_NR_ZONES > S8_MAX); 3206 3207 /* 3208 * Do not enter reclaim if fatal signal was delivered while throttled. 3209 * 1 is returned so that the page allocator does not OOM kill at this 3210 * point. 3211 */ 3212 if (throttle_direct_reclaim(sc.gfp_mask, zonelist, nodemask)) 3213 return 1; 3214 3215 trace_mm_vmscan_direct_reclaim_begin(order, 3216 sc.may_writepage, 3217 sc.gfp_mask, 3218 sc.reclaim_idx); 3219 3220 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 3221 3222 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 3223 3224 return nr_reclaimed; 3225 } 3226 3227 #ifdef CONFIG_MEMCG 3228 3229 unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, 3230 gfp_t gfp_mask, bool noswap, 3231 pg_data_t *pgdat, 3232 unsigned long *nr_scanned) 3233 { 3234 struct scan_control sc = { 3235 .nr_to_reclaim = SWAP_CLUSTER_MAX, 3236 .target_mem_cgroup = memcg, 3237 .may_writepage = !laptop_mode, 3238 .may_unmap = 1, 3239 .reclaim_idx = MAX_NR_ZONES - 1, 3240 .may_swap = !noswap, 3241 .may_shrinkslab = 1, 3242 }; 3243 unsigned long lru_pages; 3244 3245 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 3246 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 3247 3248 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order, 3249 sc.may_writepage, 3250 sc.gfp_mask, 3251 sc.reclaim_idx); 3252 3253 /* 3254 * NOTE: Although we can get the priority field, using it 3255 * here is not a good idea, since it limits the pages we can scan. 3256 * if we don't reclaim here, the shrink_node from balance_pgdat 3257 * will pick up pages from other mem cgroup's as well. We hack 3258 * the priority and make it zero. 3259 */ 3260 shrink_node_memcg(pgdat, memcg, &sc, &lru_pages); 3261 3262 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 3263 3264 *nr_scanned = sc.nr_scanned; 3265 return sc.nr_reclaimed; 3266 } 3267 3268 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, 3269 unsigned long nr_pages, 3270 gfp_t gfp_mask, 3271 bool may_swap) 3272 { 3273 struct zonelist *zonelist; 3274 unsigned long nr_reclaimed; 3275 unsigned long pflags; 3276 int nid; 3277 unsigned int noreclaim_flag; 3278 struct scan_control sc = { 3279 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), 3280 .gfp_mask = (current_gfp_context(gfp_mask) & GFP_RECLAIM_MASK) | 3281 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), 3282 .reclaim_idx = MAX_NR_ZONES - 1, 3283 .target_mem_cgroup = memcg, 3284 .priority = DEF_PRIORITY, 3285 .may_writepage = !laptop_mode, 3286 .may_unmap = 1, 3287 .may_swap = may_swap, 3288 .may_shrinkslab = 1, 3289 }; 3290 3291 /* 3292 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't 3293 * take care of from where we get pages. So the node where we start the 3294 * scan does not need to be the current node. 3295 */ 3296 nid = mem_cgroup_select_victim_node(memcg); 3297 3298 zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK]; 3299 3300 trace_mm_vmscan_memcg_reclaim_begin(0, 3301 sc.may_writepage, 3302 sc.gfp_mask, 3303 sc.reclaim_idx); 3304 3305 psi_memstall_enter(&pflags); 3306 noreclaim_flag = memalloc_noreclaim_save(); 3307 3308 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 3309 3310 memalloc_noreclaim_restore(noreclaim_flag); 3311 psi_memstall_leave(&pflags); 3312 3313 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 3314 3315 return nr_reclaimed; 3316 } 3317 #endif 3318 3319 static void age_active_anon(struct pglist_data *pgdat, 3320 struct scan_control *sc) 3321 { 3322 struct mem_cgroup *memcg; 3323 3324 if (!total_swap_pages) 3325 return; 3326 3327 memcg = mem_cgroup_iter(NULL, NULL, NULL); 3328 do { 3329 struct lruvec *lruvec = mem_cgroup_lruvec(pgdat, memcg); 3330 3331 if (inactive_list_is_low(lruvec, false, sc, true)) 3332 shrink_active_list(SWAP_CLUSTER_MAX, lruvec, 3333 sc, LRU_ACTIVE_ANON); 3334 3335 memcg = mem_cgroup_iter(NULL, memcg, NULL); 3336 } while (memcg); 3337 } 3338 3339 static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx) 3340 { 3341 int i; 3342 struct zone *zone; 3343 3344 /* 3345 * Check for watermark boosts top-down as the higher zones 3346 * are more likely to be boosted. Both watermarks and boosts 3347 * should not be checked at the time time as reclaim would 3348 * start prematurely when there is no boosting and a lower 3349 * zone is balanced. 3350 */ 3351 for (i = classzone_idx; i >= 0; i--) { 3352 zone = pgdat->node_zones + i; 3353 if (!managed_zone(zone)) 3354 continue; 3355 3356 if (zone->watermark_boost) 3357 return true; 3358 } 3359 3360 return false; 3361 } 3362 3363 /* 3364 * Returns true if there is an eligible zone balanced for the request order 3365 * and classzone_idx 3366 */ 3367 static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx) 3368 { 3369 int i; 3370 unsigned long mark = -1; 3371 struct zone *zone; 3372 3373 /* 3374 * Check watermarks bottom-up as lower zones are more likely to 3375 * meet watermarks. 3376 */ 3377 for (i = 0; i <= classzone_idx; i++) { 3378 zone = pgdat->node_zones + i; 3379 3380 if (!managed_zone(zone)) 3381 continue; 3382 3383 mark = high_wmark_pages(zone); 3384 if (zone_watermark_ok_safe(zone, order, mark, classzone_idx)) 3385 return true; 3386 } 3387 3388 /* 3389 * If a node has no populated zone within classzone_idx, it does not 3390 * need balancing by definition. This can happen if a zone-restricted 3391 * allocation tries to wake a remote kswapd. 3392 */ 3393 if (mark == -1) 3394 return true; 3395 3396 return false; 3397 } 3398 3399 /* Clear pgdat state for congested, dirty or under writeback. */ 3400 static void clear_pgdat_congested(pg_data_t *pgdat) 3401 { 3402 clear_bit(PGDAT_CONGESTED, &pgdat->flags); 3403 clear_bit(PGDAT_DIRTY, &pgdat->flags); 3404 clear_bit(PGDAT_WRITEBACK, &pgdat->flags); 3405 } 3406 3407 /* 3408 * Prepare kswapd for sleeping. This verifies that there are no processes 3409 * waiting in throttle_direct_reclaim() and that watermarks have been met. 3410 * 3411 * Returns true if kswapd is ready to sleep 3412 */ 3413 static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, int classzone_idx) 3414 { 3415 /* 3416 * The throttled processes are normally woken up in balance_pgdat() as 3417 * soon as allow_direct_reclaim() is true. But there is a potential 3418 * race between when kswapd checks the watermarks and a process gets 3419 * throttled. There is also a potential race if processes get 3420 * throttled, kswapd wakes, a large process exits thereby balancing the 3421 * zones, which causes kswapd to exit balance_pgdat() before reaching 3422 * the wake up checks. If kswapd is going to sleep, no process should 3423 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If 3424 * the wake up is premature, processes will wake kswapd and get 3425 * throttled again. The difference from wake ups in balance_pgdat() is 3426 * that here we are under prepare_to_wait(). 3427 */ 3428 if (waitqueue_active(&pgdat->pfmemalloc_wait)) 3429 wake_up_all(&pgdat->pfmemalloc_wait); 3430 3431 /* Hopeless node, leave it to direct reclaim */ 3432 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES) 3433 return true; 3434 3435 if (pgdat_balanced(pgdat, order, classzone_idx)) { 3436 clear_pgdat_congested(pgdat); 3437 return true; 3438 } 3439 3440 return false; 3441 } 3442 3443 /* 3444 * kswapd shrinks a node of pages that are at or below the highest usable 3445 * zone that is currently unbalanced. 3446 * 3447 * Returns true if kswapd scanned at least the requested number of pages to 3448 * reclaim or if the lack of progress was due to pages under writeback. 3449 * This is used to determine if the scanning priority needs to be raised. 3450 */ 3451 static bool kswapd_shrink_node(pg_data_t *pgdat, 3452 struct scan_control *sc) 3453 { 3454 struct zone *zone; 3455 int z; 3456 3457 /* Reclaim a number of pages proportional to the number of zones */ 3458 sc->nr_to_reclaim = 0; 3459 for (z = 0; z <= sc->reclaim_idx; z++) { 3460 zone = pgdat->node_zones + z; 3461 if (!managed_zone(zone)) 3462 continue; 3463 3464 sc->nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX); 3465 } 3466 3467 /* 3468 * Historically care was taken to put equal pressure on all zones but 3469 * now pressure is applied based on node LRU order. 3470 */ 3471 shrink_node(pgdat, sc); 3472 3473 /* 3474 * Fragmentation may mean that the system cannot be rebalanced for 3475 * high-order allocations. If twice the allocation size has been 3476 * reclaimed then recheck watermarks only at order-0 to prevent 3477 * excessive reclaim. Assume that a process requested a high-order 3478 * can direct reclaim/compact. 3479 */ 3480 if (sc->order && sc->nr_reclaimed >= compact_gap(sc->order)) 3481 sc->order = 0; 3482 3483 return sc->nr_scanned >= sc->nr_to_reclaim; 3484 } 3485 3486 /* 3487 * For kswapd, balance_pgdat() will reclaim pages across a node from zones 3488 * that are eligible for use by the caller until at least one zone is 3489 * balanced. 3490 * 3491 * Returns the order kswapd finished reclaiming at. 3492 * 3493 * kswapd scans the zones in the highmem->normal->dma direction. It skips 3494 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 3495 * found to have free_pages <= high_wmark_pages(zone), any page in that zone 3496 * or lower is eligible for reclaim until at least one usable zone is 3497 * balanced. 3498 */ 3499 static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) 3500 { 3501 int i; 3502 unsigned long nr_soft_reclaimed; 3503 unsigned long nr_soft_scanned; 3504 unsigned long pflags; 3505 unsigned long nr_boost_reclaim; 3506 unsigned long zone_boosts[MAX_NR_ZONES] = { 0, }; 3507 bool boosted; 3508 struct zone *zone; 3509 struct scan_control sc = { 3510 .gfp_mask = GFP_KERNEL, 3511 .order = order, 3512 .may_unmap = 1, 3513 }; 3514 3515 psi_memstall_enter(&pflags); 3516 __fs_reclaim_acquire(); 3517 3518 count_vm_event(PAGEOUTRUN); 3519 3520 /* 3521 * Account for the reclaim boost. Note that the zone boost is left in 3522 * place so that parallel allocations that are near the watermark will 3523 * stall or direct reclaim until kswapd is finished. 3524 */ 3525 nr_boost_reclaim = 0; 3526 for (i = 0; i <= classzone_idx; i++) { 3527 zone = pgdat->node_zones + i; 3528 if (!managed_zone(zone)) 3529 continue; 3530 3531 nr_boost_reclaim += zone->watermark_boost; 3532 zone_boosts[i] = zone->watermark_boost; 3533 } 3534 boosted = nr_boost_reclaim; 3535 3536 restart: 3537 sc.priority = DEF_PRIORITY; 3538 do { 3539 unsigned long nr_reclaimed = sc.nr_reclaimed; 3540 bool raise_priority = true; 3541 bool balanced; 3542 bool ret; 3543 3544 sc.reclaim_idx = classzone_idx; 3545 3546 /* 3547 * If the number of buffer_heads exceeds the maximum allowed 3548 * then consider reclaiming from all zones. This has a dual 3549 * purpose -- on 64-bit systems it is expected that 3550 * buffer_heads are stripped during active rotation. On 32-bit 3551 * systems, highmem pages can pin lowmem memory and shrinking 3552 * buffers can relieve lowmem pressure. Reclaim may still not 3553 * go ahead if all eligible zones for the original allocation 3554 * request are balanced to avoid excessive reclaim from kswapd. 3555 */ 3556 if (buffer_heads_over_limit) { 3557 for (i = MAX_NR_ZONES - 1; i >= 0; i--) { 3558 zone = pgdat->node_zones + i; 3559 if (!managed_zone(zone)) 3560 continue; 3561 3562 sc.reclaim_idx = i; 3563 break; 3564 } 3565 } 3566 3567 /* 3568 * If the pgdat is imbalanced then ignore boosting and preserve 3569 * the watermarks for a later time and restart. Note that the 3570 * zone watermarks will be still reset at the end of balancing 3571 * on the grounds that the normal reclaim should be enough to 3572 * re-evaluate if boosting is required when kswapd next wakes. 3573 */ 3574 balanced = pgdat_balanced(pgdat, sc.order, classzone_idx); 3575 if (!balanced && nr_boost_reclaim) { 3576 nr_boost_reclaim = 0; 3577 goto restart; 3578 } 3579 3580 /* 3581 * If boosting is not active then only reclaim if there are no 3582 * eligible zones. Note that sc.reclaim_idx is not used as 3583 * buffer_heads_over_limit may have adjusted it. 3584 */ 3585 if (!nr_boost_reclaim && balanced) 3586 goto out; 3587 3588 /* Limit the priority of boosting to avoid reclaim writeback */ 3589 if (nr_boost_reclaim && sc.priority == DEF_PRIORITY - 2) 3590 raise_priority = false; 3591 3592 /* 3593 * Do not writeback or swap pages for boosted reclaim. The 3594 * intent is to relieve pressure not issue sub-optimal IO 3595 * from reclaim context. If no pages are reclaimed, the 3596 * reclaim will be aborted. 3597 */ 3598 sc.may_writepage = !laptop_mode && !nr_boost_reclaim; 3599 sc.may_swap = !nr_boost_reclaim; 3600 sc.may_shrinkslab = !nr_boost_reclaim; 3601 3602 /* 3603 * Do some background aging of the anon list, to give 3604 * pages a chance to be referenced before reclaiming. All 3605 * pages are rotated regardless of classzone as this is 3606 * about consistent aging. 3607 */ 3608 age_active_anon(pgdat, &sc); 3609 3610 /* 3611 * If we're getting trouble reclaiming, start doing writepage 3612 * even in laptop mode. 3613 */ 3614 if (sc.priority < DEF_PRIORITY - 2) 3615 sc.may_writepage = 1; 3616 3617 /* Call soft limit reclaim before calling shrink_node. */ 3618 sc.nr_scanned = 0; 3619 nr_soft_scanned = 0; 3620 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(pgdat, sc.order, 3621 sc.gfp_mask, &nr_soft_scanned); 3622 sc.nr_reclaimed += nr_soft_reclaimed; 3623 3624 /* 3625 * There should be no need to raise the scanning priority if 3626 * enough pages are already being scanned that that high 3627 * watermark would be met at 100% efficiency. 3628 */ 3629 if (kswapd_shrink_node(pgdat, &sc)) 3630 raise_priority = false; 3631 3632 /* 3633 * If the low watermark is met there is no need for processes 3634 * to be throttled on pfmemalloc_wait as they should not be 3635 * able to safely make forward progress. Wake them 3636 */ 3637 if (waitqueue_active(&pgdat->pfmemalloc_wait) && 3638 allow_direct_reclaim(pgdat)) 3639 wake_up_all(&pgdat->pfmemalloc_wait); 3640 3641 /* Check if kswapd should be suspending */ 3642 __fs_reclaim_release(); 3643 ret = try_to_freeze(); 3644 __fs_reclaim_acquire(); 3645 if (ret || kthread_should_stop()) 3646 break; 3647 3648 /* 3649 * Raise priority if scanning rate is too low or there was no 3650 * progress in reclaiming pages 3651 */ 3652 nr_reclaimed = sc.nr_reclaimed - nr_reclaimed; 3653 nr_boost_reclaim -= min(nr_boost_reclaim, nr_reclaimed); 3654 3655 /* 3656 * If reclaim made no progress for a boost, stop reclaim as 3657 * IO cannot be queued and it could be an infinite loop in 3658 * extreme circumstances. 3659 */ 3660 if (nr_boost_reclaim && !nr_reclaimed) 3661 break; 3662 3663 if (raise_priority || !nr_reclaimed) 3664 sc.priority--; 3665 } while (sc.priority >= 1); 3666 3667 if (!sc.nr_reclaimed) 3668 pgdat->kswapd_failures++; 3669 3670 out: 3671 /* If reclaim was boosted, account for the reclaim done in this pass */ 3672 if (boosted) { 3673 unsigned long flags; 3674 3675 for (i = 0; i <= classzone_idx; i++) { 3676 if (!zone_boosts[i]) 3677 continue; 3678 3679 /* Increments are under the zone lock */ 3680 zone = pgdat->node_zones + i; 3681 spin_lock_irqsave(&zone->lock, flags); 3682 zone->watermark_boost -= min(zone->watermark_boost, zone_boosts[i]); 3683 spin_unlock_irqrestore(&zone->lock, flags); 3684 } 3685 3686 /* 3687 * As there is now likely space, wakeup kcompact to defragment 3688 * pageblocks. 3689 */ 3690 wakeup_kcompactd(pgdat, pageblock_order, classzone_idx); 3691 } 3692 3693 snapshot_refaults(NULL, pgdat); 3694 __fs_reclaim_release(); 3695 psi_memstall_leave(&pflags); 3696 /* 3697 * Return the order kswapd stopped reclaiming at as 3698 * prepare_kswapd_sleep() takes it into account. If another caller 3699 * entered the allocator slow path while kswapd was awake, order will 3700 * remain at the higher level. 3701 */ 3702 return sc.order; 3703 } 3704 3705 /* 3706 * pgdat->kswapd_classzone_idx is the highest zone index that a recent 3707 * allocation request woke kswapd for. When kswapd has not woken recently, 3708 * the value is MAX_NR_ZONES which is not a valid index. This compares a 3709 * given classzone and returns it or the highest classzone index kswapd 3710 * was recently woke for. 3711 */ 3712 static enum zone_type kswapd_classzone_idx(pg_data_t *pgdat, 3713 enum zone_type classzone_idx) 3714 { 3715 if (pgdat->kswapd_classzone_idx == MAX_NR_ZONES) 3716 return classzone_idx; 3717 3718 return max(pgdat->kswapd_classzone_idx, classzone_idx); 3719 } 3720 3721 static void kswapd_try_to_sleep(pg_data_t *pgdat, int alloc_order, int reclaim_order, 3722 unsigned int classzone_idx) 3723 { 3724 long remaining = 0; 3725 DEFINE_WAIT(wait); 3726 3727 if (freezing(current) || kthread_should_stop()) 3728 return; 3729 3730 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 3731 3732 /* 3733 * Try to sleep for a short interval. Note that kcompactd will only be 3734 * woken if it is possible to sleep for a short interval. This is 3735 * deliberate on the assumption that if reclaim cannot keep an 3736 * eligible zone balanced that it's also unlikely that compaction will 3737 * succeed. 3738 */ 3739 if (prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) { 3740 /* 3741 * Compaction records what page blocks it recently failed to 3742 * isolate pages from and skips them in the future scanning. 3743 * When kswapd is going to sleep, it is reasonable to assume 3744 * that pages and compaction may succeed so reset the cache. 3745 */ 3746 reset_isolation_suitable(pgdat); 3747 3748 /* 3749 * We have freed the memory, now we should compact it to make 3750 * allocation of the requested order possible. 3751 */ 3752 wakeup_kcompactd(pgdat, alloc_order, classzone_idx); 3753 3754 remaining = schedule_timeout(HZ/10); 3755 3756 /* 3757 * If woken prematurely then reset kswapd_classzone_idx and 3758 * order. The values will either be from a wakeup request or 3759 * the previous request that slept prematurely. 3760 */ 3761 if (remaining) { 3762 pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx); 3763 pgdat->kswapd_order = max(pgdat->kswapd_order, reclaim_order); 3764 } 3765 3766 finish_wait(&pgdat->kswapd_wait, &wait); 3767 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 3768 } 3769 3770 /* 3771 * After a short sleep, check if it was a premature sleep. If not, then 3772 * go fully to sleep until explicitly woken up. 3773 */ 3774 if (!remaining && 3775 prepare_kswapd_sleep(pgdat, reclaim_order, classzone_idx)) { 3776 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 3777 3778 /* 3779 * vmstat counters are not perfectly accurate and the estimated 3780 * value for counters such as NR_FREE_PAGES can deviate from the 3781 * true value by nr_online_cpus * threshold. To avoid the zone 3782 * watermarks being breached while under pressure, we reduce the 3783 * per-cpu vmstat threshold while kswapd is awake and restore 3784 * them before going back to sleep. 3785 */ 3786 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 3787 3788 if (!kthread_should_stop()) 3789 schedule(); 3790 3791 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 3792 } else { 3793 if (remaining) 3794 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 3795 else 3796 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 3797 } 3798 finish_wait(&pgdat->kswapd_wait, &wait); 3799 } 3800 3801 /* 3802 * The background pageout daemon, started as a kernel thread 3803 * from the init process. 3804 * 3805 * This basically trickles out pages so that we have _some_ 3806 * free memory available even if there is no other activity 3807 * that frees anything up. This is needed for things like routing 3808 * etc, where we otherwise might have all activity going on in 3809 * asynchronous contexts that cannot page things out. 3810 * 3811 * If there are applications that are active memory-allocators 3812 * (most normal use), this basically shouldn't matter. 3813 */ 3814 static int kswapd(void *p) 3815 { 3816 unsigned int alloc_order, reclaim_order; 3817 unsigned int classzone_idx = MAX_NR_ZONES - 1; 3818 pg_data_t *pgdat = (pg_data_t*)p; 3819 struct task_struct *tsk = current; 3820 3821 struct reclaim_state reclaim_state = { 3822 .reclaimed_slab = 0, 3823 }; 3824 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 3825 3826 if (!cpumask_empty(cpumask)) 3827 set_cpus_allowed_ptr(tsk, cpumask); 3828 current->reclaim_state = &reclaim_state; 3829 3830 /* 3831 * Tell the memory management that we're a "memory allocator", 3832 * and that if we need more memory we should get access to it 3833 * regardless (see "__alloc_pages()"). "kswapd" should 3834 * never get caught in the normal page freeing logic. 3835 * 3836 * (Kswapd normally doesn't need memory anyway, but sometimes 3837 * you need a small amount of memory in order to be able to 3838 * page out something else, and this flag essentially protects 3839 * us from recursively trying to free more memory as we're 3840 * trying to free the first piece of memory in the first place). 3841 */ 3842 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 3843 set_freezable(); 3844 3845 pgdat->kswapd_order = 0; 3846 pgdat->kswapd_classzone_idx = MAX_NR_ZONES; 3847 for ( ; ; ) { 3848 bool ret; 3849 3850 alloc_order = reclaim_order = pgdat->kswapd_order; 3851 classzone_idx = kswapd_classzone_idx(pgdat, classzone_idx); 3852 3853 kswapd_try_sleep: 3854 kswapd_try_to_sleep(pgdat, alloc_order, reclaim_order, 3855 classzone_idx); 3856 3857 /* Read the new order and classzone_idx */ 3858 alloc_order = reclaim_order = pgdat->kswapd_order; 3859 classzone_idx = kswapd_classzone_idx(pgdat, 0); 3860 pgdat->kswapd_order = 0; 3861 pgdat->kswapd_classzone_idx = MAX_NR_ZONES; 3862 3863 ret = try_to_freeze(); 3864 if (kthread_should_stop()) 3865 break; 3866 3867 /* 3868 * We can speed up thawing tasks if we don't call balance_pgdat 3869 * after returning from the refrigerator 3870 */ 3871 if (ret) 3872 continue; 3873 3874 /* 3875 * Reclaim begins at the requested order but if a high-order 3876 * reclaim fails then kswapd falls back to reclaiming for 3877 * order-0. If that happens, kswapd will consider sleeping 3878 * for the order it finished reclaiming at (reclaim_order) 3879 * but kcompactd is woken to compact for the original 3880 * request (alloc_order). 3881 */ 3882 trace_mm_vmscan_kswapd_wake(pgdat->node_id, classzone_idx, 3883 alloc_order); 3884 reclaim_order = balance_pgdat(pgdat, alloc_order, classzone_idx); 3885 if (reclaim_order < alloc_order) 3886 goto kswapd_try_sleep; 3887 } 3888 3889 tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD); 3890 current->reclaim_state = NULL; 3891 3892 return 0; 3893 } 3894 3895 /* 3896 * A zone is low on free memory or too fragmented for high-order memory. If 3897 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's 3898 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim 3899 * has failed or is not needed, still wake up kcompactd if only compaction is 3900 * needed. 3901 */ 3902 void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order, 3903 enum zone_type classzone_idx) 3904 { 3905 pg_data_t *pgdat; 3906 3907 if (!managed_zone(zone)) 3908 return; 3909 3910 if (!cpuset_zone_allowed(zone, gfp_flags)) 3911 return; 3912 pgdat = zone->zone_pgdat; 3913 pgdat->kswapd_classzone_idx = kswapd_classzone_idx(pgdat, 3914 classzone_idx); 3915 pgdat->kswapd_order = max(pgdat->kswapd_order, order); 3916 if (!waitqueue_active(&pgdat->kswapd_wait)) 3917 return; 3918 3919 /* Hopeless node, leave it to direct reclaim if possible */ 3920 if (pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES || 3921 (pgdat_balanced(pgdat, order, classzone_idx) && 3922 !pgdat_watermark_boosted(pgdat, classzone_idx))) { 3923 /* 3924 * There may be plenty of free memory available, but it's too 3925 * fragmented for high-order allocations. Wake up kcompactd 3926 * and rely on compaction_suitable() to determine if it's 3927 * needed. If it fails, it will defer subsequent attempts to 3928 * ratelimit its work. 3929 */ 3930 if (!(gfp_flags & __GFP_DIRECT_RECLAIM)) 3931 wakeup_kcompactd(pgdat, order, classzone_idx); 3932 return; 3933 } 3934 3935 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, classzone_idx, order, 3936 gfp_flags); 3937 wake_up_interruptible(&pgdat->kswapd_wait); 3938 } 3939 3940 #ifdef CONFIG_HIBERNATION 3941 /* 3942 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 3943 * freed pages. 3944 * 3945 * Rather than trying to age LRUs the aim is to preserve the overall 3946 * LRU order by reclaiming preferentially 3947 * inactive > active > active referenced > active mapped 3948 */ 3949 unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 3950 { 3951 struct reclaim_state reclaim_state; 3952 struct scan_control sc = { 3953 .nr_to_reclaim = nr_to_reclaim, 3954 .gfp_mask = GFP_HIGHUSER_MOVABLE, 3955 .reclaim_idx = MAX_NR_ZONES - 1, 3956 .priority = DEF_PRIORITY, 3957 .may_writepage = 1, 3958 .may_unmap = 1, 3959 .may_swap = 1, 3960 .hibernation_mode = 1, 3961 }; 3962 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 3963 struct task_struct *p = current; 3964 unsigned long nr_reclaimed; 3965 unsigned int noreclaim_flag; 3966 3967 fs_reclaim_acquire(sc.gfp_mask); 3968 noreclaim_flag = memalloc_noreclaim_save(); 3969 reclaim_state.reclaimed_slab = 0; 3970 p->reclaim_state = &reclaim_state; 3971 3972 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 3973 3974 p->reclaim_state = NULL; 3975 memalloc_noreclaim_restore(noreclaim_flag); 3976 fs_reclaim_release(sc.gfp_mask); 3977 3978 return nr_reclaimed; 3979 } 3980 #endif /* CONFIG_HIBERNATION */ 3981 3982 /* It's optimal to keep kswapds on the same CPUs as their memory, but 3983 not required for correctness. So if the last cpu in a node goes 3984 away, we get changed to run anywhere: as the first one comes back, 3985 restore their cpu bindings. */ 3986 static int kswapd_cpu_online(unsigned int cpu) 3987 { 3988 int nid; 3989 3990 for_each_node_state(nid, N_MEMORY) { 3991 pg_data_t *pgdat = NODE_DATA(nid); 3992 const struct cpumask *mask; 3993 3994 mask = cpumask_of_node(pgdat->node_id); 3995 3996 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 3997 /* One of our CPUs online: restore mask */ 3998 set_cpus_allowed_ptr(pgdat->kswapd, mask); 3999 } 4000 return 0; 4001 } 4002 4003 /* 4004 * This kswapd start function will be called by init and node-hot-add. 4005 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 4006 */ 4007 int kswapd_run(int nid) 4008 { 4009 pg_data_t *pgdat = NODE_DATA(nid); 4010 int ret = 0; 4011 4012 if (pgdat->kswapd) 4013 return 0; 4014 4015 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 4016 if (IS_ERR(pgdat->kswapd)) { 4017 /* failure at boot is fatal */ 4018 BUG_ON(system_state < SYSTEM_RUNNING); 4019 pr_err("Failed to start kswapd on node %d\n", nid); 4020 ret = PTR_ERR(pgdat->kswapd); 4021 pgdat->kswapd = NULL; 4022 } 4023 return ret; 4024 } 4025 4026 /* 4027 * Called by memory hotplug when all memory in a node is offlined. Caller must 4028 * hold mem_hotplug_begin/end(). 4029 */ 4030 void kswapd_stop(int nid) 4031 { 4032 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 4033 4034 if (kswapd) { 4035 kthread_stop(kswapd); 4036 NODE_DATA(nid)->kswapd = NULL; 4037 } 4038 } 4039 4040 static int __init kswapd_init(void) 4041 { 4042 int nid, ret; 4043 4044 swap_setup(); 4045 for_each_node_state(nid, N_MEMORY) 4046 kswapd_run(nid); 4047 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, 4048 "mm/vmscan:online", kswapd_cpu_online, 4049 NULL); 4050 WARN_ON(ret < 0); 4051 return 0; 4052 } 4053 4054 module_init(kswapd_init) 4055 4056 #ifdef CONFIG_NUMA 4057 /* 4058 * Node reclaim mode 4059 * 4060 * If non-zero call node_reclaim when the number of free pages falls below 4061 * the watermarks. 4062 */ 4063 int node_reclaim_mode __read_mostly; 4064 4065 #define RECLAIM_OFF 0 4066 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 4067 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 4068 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */ 4069 4070 /* 4071 * Priority for NODE_RECLAIM. This determines the fraction of pages 4072 * of a node considered for each zone_reclaim. 4 scans 1/16th of 4073 * a zone. 4074 */ 4075 #define NODE_RECLAIM_PRIORITY 4 4076 4077 /* 4078 * Percentage of pages in a zone that must be unmapped for node_reclaim to 4079 * occur. 4080 */ 4081 int sysctl_min_unmapped_ratio = 1; 4082 4083 /* 4084 * If the number of slab pages in a zone grows beyond this percentage then 4085 * slab reclaim needs to occur. 4086 */ 4087 int sysctl_min_slab_ratio = 5; 4088 4089 static inline unsigned long node_unmapped_file_pages(struct pglist_data *pgdat) 4090 { 4091 unsigned long file_mapped = node_page_state(pgdat, NR_FILE_MAPPED); 4092 unsigned long file_lru = node_page_state(pgdat, NR_INACTIVE_FILE) + 4093 node_page_state(pgdat, NR_ACTIVE_FILE); 4094 4095 /* 4096 * It's possible for there to be more file mapped pages than 4097 * accounted for by the pages on the file LRU lists because 4098 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 4099 */ 4100 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 4101 } 4102 4103 /* Work out how many page cache pages we can reclaim in this reclaim_mode */ 4104 static unsigned long node_pagecache_reclaimable(struct pglist_data *pgdat) 4105 { 4106 unsigned long nr_pagecache_reclaimable; 4107 unsigned long delta = 0; 4108 4109 /* 4110 * If RECLAIM_UNMAP is set, then all file pages are considered 4111 * potentially reclaimable. Otherwise, we have to worry about 4112 * pages like swapcache and node_unmapped_file_pages() provides 4113 * a better estimate 4114 */ 4115 if (node_reclaim_mode & RECLAIM_UNMAP) 4116 nr_pagecache_reclaimable = node_page_state(pgdat, NR_FILE_PAGES); 4117 else 4118 nr_pagecache_reclaimable = node_unmapped_file_pages(pgdat); 4119 4120 /* If we can't clean pages, remove dirty pages from consideration */ 4121 if (!(node_reclaim_mode & RECLAIM_WRITE)) 4122 delta += node_page_state(pgdat, NR_FILE_DIRTY); 4123 4124 /* Watch for any possible underflows due to delta */ 4125 if (unlikely(delta > nr_pagecache_reclaimable)) 4126 delta = nr_pagecache_reclaimable; 4127 4128 return nr_pagecache_reclaimable - delta; 4129 } 4130 4131 /* 4132 * Try to free up some pages from this node through reclaim. 4133 */ 4134 static int __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) 4135 { 4136 /* Minimum pages needed in order to stay on node */ 4137 const unsigned long nr_pages = 1 << order; 4138 struct task_struct *p = current; 4139 struct reclaim_state reclaim_state; 4140 unsigned int noreclaim_flag; 4141 struct scan_control sc = { 4142 .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), 4143 .gfp_mask = current_gfp_context(gfp_mask), 4144 .order = order, 4145 .priority = NODE_RECLAIM_PRIORITY, 4146 .may_writepage = !!(node_reclaim_mode & RECLAIM_WRITE), 4147 .may_unmap = !!(node_reclaim_mode & RECLAIM_UNMAP), 4148 .may_swap = 1, 4149 .reclaim_idx = gfp_zone(gfp_mask), 4150 }; 4151 4152 cond_resched(); 4153 fs_reclaim_acquire(sc.gfp_mask); 4154 /* 4155 * We need to be able to allocate from the reserves for RECLAIM_UNMAP 4156 * and we also need to be able to write out pages for RECLAIM_WRITE 4157 * and RECLAIM_UNMAP. 4158 */ 4159 noreclaim_flag = memalloc_noreclaim_save(); 4160 p->flags |= PF_SWAPWRITE; 4161 reclaim_state.reclaimed_slab = 0; 4162 p->reclaim_state = &reclaim_state; 4163 4164 if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages) { 4165 /* 4166 * Free memory by calling shrink node with increasing 4167 * priorities until we have enough memory freed. 4168 */ 4169 do { 4170 shrink_node(pgdat, &sc); 4171 } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); 4172 } 4173 4174 p->reclaim_state = NULL; 4175 current->flags &= ~PF_SWAPWRITE; 4176 memalloc_noreclaim_restore(noreclaim_flag); 4177 fs_reclaim_release(sc.gfp_mask); 4178 return sc.nr_reclaimed >= nr_pages; 4179 } 4180 4181 int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order) 4182 { 4183 int ret; 4184 4185 /* 4186 * Node reclaim reclaims unmapped file backed pages and 4187 * slab pages if we are over the defined limits. 4188 * 4189 * A small portion of unmapped file backed pages is needed for 4190 * file I/O otherwise pages read by file I/O will be immediately 4191 * thrown out if the node is overallocated. So we do not reclaim 4192 * if less than a specified percentage of the node is used by 4193 * unmapped file backed pages. 4194 */ 4195 if (node_pagecache_reclaimable(pgdat) <= pgdat->min_unmapped_pages && 4196 node_page_state(pgdat, NR_SLAB_RECLAIMABLE) <= pgdat->min_slab_pages) 4197 return NODE_RECLAIM_FULL; 4198 4199 /* 4200 * Do not scan if the allocation should not be delayed. 4201 */ 4202 if (!gfpflags_allow_blocking(gfp_mask) || (current->flags & PF_MEMALLOC)) 4203 return NODE_RECLAIM_NOSCAN; 4204 4205 /* 4206 * Only run node reclaim on the local node or on nodes that do not 4207 * have associated processors. This will favor the local processor 4208 * over remote processors and spread off node memory allocations 4209 * as wide as possible. 4210 */ 4211 if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id != numa_node_id()) 4212 return NODE_RECLAIM_NOSCAN; 4213 4214 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags)) 4215 return NODE_RECLAIM_NOSCAN; 4216 4217 ret = __node_reclaim(pgdat, gfp_mask, order); 4218 clear_bit(PGDAT_RECLAIM_LOCKED, &pgdat->flags); 4219 4220 if (!ret) 4221 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 4222 4223 return ret; 4224 } 4225 #endif 4226 4227 /* 4228 * page_evictable - test whether a page is evictable 4229 * @page: the page to test 4230 * 4231 * Test whether page is evictable--i.e., should be placed on active/inactive 4232 * lists vs unevictable list. 4233 * 4234 * Reasons page might not be evictable: 4235 * (1) page's mapping marked unevictable 4236 * (2) page is part of an mlocked VMA 4237 * 4238 */ 4239 int page_evictable(struct page *page) 4240 { 4241 int ret; 4242 4243 /* Prevent address_space of inode and swap cache from being freed */ 4244 rcu_read_lock(); 4245 ret = !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); 4246 rcu_read_unlock(); 4247 return ret; 4248 } 4249 4250 /** 4251 * check_move_unevictable_pages - check pages for evictability and move to 4252 * appropriate zone lru list 4253 * @pvec: pagevec with lru pages to check 4254 * 4255 * Checks pages for evictability, if an evictable page is in the unevictable 4256 * lru list, moves it to the appropriate evictable lru list. This function 4257 * should be only used for lru pages. 4258 */ 4259 void check_move_unevictable_pages(struct pagevec *pvec) 4260 { 4261 struct lruvec *lruvec; 4262 struct pglist_data *pgdat = NULL; 4263 int pgscanned = 0; 4264 int pgrescued = 0; 4265 int i; 4266 4267 for (i = 0; i < pvec->nr; i++) { 4268 struct page *page = pvec->pages[i]; 4269 struct pglist_data *pagepgdat = page_pgdat(page); 4270 4271 pgscanned++; 4272 if (pagepgdat != pgdat) { 4273 if (pgdat) 4274 spin_unlock_irq(&pgdat->lru_lock); 4275 pgdat = pagepgdat; 4276 spin_lock_irq(&pgdat->lru_lock); 4277 } 4278 lruvec = mem_cgroup_page_lruvec(page, pgdat); 4279 4280 if (!PageLRU(page) || !PageUnevictable(page)) 4281 continue; 4282 4283 if (page_evictable(page)) { 4284 enum lru_list lru = page_lru_base_type(page); 4285 4286 VM_BUG_ON_PAGE(PageActive(page), page); 4287 ClearPageUnevictable(page); 4288 del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); 4289 add_page_to_lru_list(page, lruvec, lru); 4290 pgrescued++; 4291 } 4292 } 4293 4294 if (pgdat) { 4295 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); 4296 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); 4297 spin_unlock_irq(&pgdat->lru_lock); 4298 } 4299 } 4300 EXPORT_SYMBOL_GPL(check_move_unevictable_pages); 4301