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