vmscan.c revision d6c438b6cd733834a3cec55af8577a8fc3548016
1/* 2 * linux/mm/vmscan.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * 6 * Swap reorganised 29.12.95, Stephen Tweedie. 7 * kswapd added: 7.1.96 sct 8 * Removed kswapd_ctl limits, and swap out as many pages as needed 9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). 11 * Multiqueue VM started 5.8.00, Rik van Riel. 12 */ 13 14#include <linux/mm.h> 15#include <linux/module.h> 16#include <linux/gfp.h> 17#include <linux/kernel_stat.h> 18#include <linux/swap.h> 19#include <linux/pagemap.h> 20#include <linux/init.h> 21#include <linux/highmem.h> 22#include <linux/vmstat.h> 23#include <linux/file.h> 24#include <linux/writeback.h> 25#include <linux/blkdev.h> 26#include <linux/buffer_head.h> /* for try_to_release_page(), 27 buffer_heads_over_limit */ 28#include <linux/mm_inline.h> 29#include <linux/pagevec.h> 30#include <linux/backing-dev.h> 31#include <linux/rmap.h> 32#include <linux/topology.h> 33#include <linux/cpu.h> 34#include <linux/cpuset.h> 35#include <linux/compaction.h> 36#include <linux/notifier.h> 37#include <linux/rwsem.h> 38#include <linux/delay.h> 39#include <linux/kthread.h> 40#include <linux/freezer.h> 41#include <linux/memcontrol.h> 42#include <linux/delayacct.h> 43#include <linux/sysctl.h> 44#include <linux/oom.h> 45 46#include <asm/tlbflush.h> 47#include <asm/div64.h> 48 49#include <linux/swapops.h> 50 51#include "internal.h" 52 53#define CREATE_TRACE_POINTS 54#include <trace/events/vmscan.h> 55 56/* 57 * reclaim_mode determines how the inactive list is shrunk 58 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages 59 * RECLAIM_MODE_ASYNC: Do not block 60 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback 61 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference 62 * page from the LRU and reclaim all pages within a 63 * naturally aligned range 64 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of 65 * order-0 pages and then compact the zone 66 */ 67typedef unsigned __bitwise__ reclaim_mode_t; 68#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) 69#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) 70#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) 71#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) 72#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) 73 74struct scan_control { 75 /* Incremented by the number of inactive pages that were scanned */ 76 unsigned long nr_scanned; 77 78 /* Number of pages freed so far during a call to shrink_zones() */ 79 unsigned long nr_reclaimed; 80 81 /* How many pages shrink_list() should reclaim */ 82 unsigned long nr_to_reclaim; 83 84 unsigned long hibernation_mode; 85 86 /* This context's GFP mask */ 87 gfp_t gfp_mask; 88 89 int may_writepage; 90 91 /* Can mapped pages be reclaimed? */ 92 int may_unmap; 93 94 /* Can pages be swapped as part of reclaim? */ 95 int may_swap; 96 97 int swappiness; 98 99 int order; 100 101 /* 102 * Intend to reclaim enough continuous memory rather than reclaim 103 * enough amount of memory. i.e, mode for high order allocation. 104 */ 105 reclaim_mode_t reclaim_mode; 106 107 /* Which cgroup do we reclaim from */ 108 struct mem_cgroup *mem_cgroup; 109 110 /* 111 * Nodemask of nodes allowed by the caller. If NULL, all nodes 112 * are scanned. 113 */ 114 nodemask_t *nodemask; 115}; 116 117#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 118 119#ifdef ARCH_HAS_PREFETCH 120#define prefetch_prev_lru_page(_page, _base, _field) \ 121 do { \ 122 if ((_page)->lru.prev != _base) { \ 123 struct page *prev; \ 124 \ 125 prev = lru_to_page(&(_page->lru)); \ 126 prefetch(&prev->_field); \ 127 } \ 128 } while (0) 129#else 130#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 131#endif 132 133#ifdef ARCH_HAS_PREFETCHW 134#define prefetchw_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 prefetchw(&prev->_field); \ 141 } \ 142 } while (0) 143#else 144#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 145#endif 146 147/* 148 * From 0 .. 100. Higher means more swappy. 149 */ 150int vm_swappiness = 60; 151long vm_total_pages; /* The total number of pages which the VM controls */ 152 153static LIST_HEAD(shrinker_list); 154static DECLARE_RWSEM(shrinker_rwsem); 155 156#ifdef CONFIG_CGROUP_MEM_RES_CTLR 157#define scanning_global_lru(sc) (!(sc)->mem_cgroup) 158#else 159#define scanning_global_lru(sc) (1) 160#endif 161 162static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 163 struct scan_control *sc) 164{ 165 if (!scanning_global_lru(sc)) 166 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 167 168 return &zone->reclaim_stat; 169} 170 171static unsigned long zone_nr_lru_pages(struct zone *zone, 172 struct scan_control *sc, enum lru_list lru) 173{ 174 if (!scanning_global_lru(sc)) 175 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); 176 177 return zone_page_state(zone, NR_LRU_BASE + lru); 178} 179 180 181/* 182 * Add a shrinker callback to be called from the vm 183 */ 184void register_shrinker(struct shrinker *shrinker) 185{ 186 shrinker->nr = 0; 187 down_write(&shrinker_rwsem); 188 list_add_tail(&shrinker->list, &shrinker_list); 189 up_write(&shrinker_rwsem); 190} 191EXPORT_SYMBOL(register_shrinker); 192 193/* 194 * Remove one 195 */ 196void unregister_shrinker(struct shrinker *shrinker) 197{ 198 down_write(&shrinker_rwsem); 199 list_del(&shrinker->list); 200 up_write(&shrinker_rwsem); 201} 202EXPORT_SYMBOL(unregister_shrinker); 203 204#define SHRINK_BATCH 128 205/* 206 * Call the shrink functions to age shrinkable caches 207 * 208 * Here we assume it costs one seek to replace a lru page and that it also 209 * takes a seek to recreate a cache object. With this in mind we age equal 210 * percentages of the lru and ageable caches. This should balance the seeks 211 * generated by these structures. 212 * 213 * If the vm encountered mapped pages on the LRU it increase the pressure on 214 * slab to avoid swapping. 215 * 216 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 217 * 218 * `lru_pages' represents the number of on-LRU pages in all the zones which 219 * are eligible for the caller's allocation attempt. It is used for balancing 220 * slab reclaim versus page reclaim. 221 * 222 * Returns the number of slab objects which we shrunk. 223 */ 224unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, 225 unsigned long lru_pages) 226{ 227 struct shrinker *shrinker; 228 unsigned long ret = 0; 229 230 if (scanned == 0) 231 scanned = SWAP_CLUSTER_MAX; 232 233 if (!down_read_trylock(&shrinker_rwsem)) 234 return 1; /* Assume we'll be able to shrink next time */ 235 236 list_for_each_entry(shrinker, &shrinker_list, list) { 237 unsigned long long delta; 238 unsigned long total_scan; 239 unsigned long max_pass; 240 241 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask); 242 delta = (4 * scanned) / shrinker->seeks; 243 delta *= max_pass; 244 do_div(delta, lru_pages + 1); 245 shrinker->nr += delta; 246 if (shrinker->nr < 0) { 247 printk(KERN_ERR "shrink_slab: %pF negative objects to " 248 "delete nr=%ld\n", 249 shrinker->shrink, shrinker->nr); 250 shrinker->nr = max_pass; 251 } 252 253 /* 254 * Avoid risking looping forever due to too large nr value: 255 * never try to free more than twice the estimate number of 256 * freeable entries. 257 */ 258 if (shrinker->nr > max_pass * 2) 259 shrinker->nr = max_pass * 2; 260 261 total_scan = shrinker->nr; 262 shrinker->nr = 0; 263 264 while (total_scan >= SHRINK_BATCH) { 265 long this_scan = SHRINK_BATCH; 266 int shrink_ret; 267 int nr_before; 268 269 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); 270 shrink_ret = (*shrinker->shrink)(shrinker, this_scan, 271 gfp_mask); 272 if (shrink_ret == -1) 273 break; 274 if (shrink_ret < nr_before) 275 ret += nr_before - shrink_ret; 276 count_vm_events(SLABS_SCANNED, this_scan); 277 total_scan -= this_scan; 278 279 cond_resched(); 280 } 281 282 shrinker->nr += total_scan; 283 } 284 up_read(&shrinker_rwsem); 285 return ret; 286} 287 288static void set_reclaim_mode(int priority, struct scan_control *sc, 289 bool sync) 290{ 291 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 292 293 /* 294 * Initially assume we are entering either lumpy reclaim or 295 * reclaim/compaction.Depending on the order, we will either set the 296 * sync mode or just reclaim order-0 pages later. 297 */ 298 if (COMPACTION_BUILD) 299 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 300 else 301 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 302 303 /* 304 * Avoid using lumpy reclaim or reclaim/compaction if possible by 305 * restricting when its set to either costly allocations or when 306 * under memory pressure 307 */ 308 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 309 sc->reclaim_mode |= syncmode; 310 else if (sc->order && priority < DEF_PRIORITY - 2) 311 sc->reclaim_mode |= syncmode; 312 else 313 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 314} 315 316static void reset_reclaim_mode(struct scan_control *sc) 317{ 318 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 319} 320 321static inline int is_page_cache_freeable(struct page *page) 322{ 323 /* 324 * A freeable page cache page is referenced only by the caller 325 * that isolated the page, the page cache radix tree and 326 * optional buffer heads at page->private. 327 */ 328 return page_count(page) - page_has_private(page) == 2; 329} 330 331static int may_write_to_queue(struct backing_dev_info *bdi, 332 struct scan_control *sc) 333{ 334 if (current->flags & PF_SWAPWRITE) 335 return 1; 336 if (!bdi_write_congested(bdi)) 337 return 1; 338 if (bdi == current->backing_dev_info) 339 return 1; 340 341 /* lumpy reclaim for hugepage often need a lot of write */ 342 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 343 return 1; 344 return 0; 345} 346 347/* 348 * We detected a synchronous write error writing a page out. Probably 349 * -ENOSPC. We need to propagate that into the address_space for a subsequent 350 * fsync(), msync() or close(). 351 * 352 * The tricky part is that after writepage we cannot touch the mapping: nothing 353 * prevents it from being freed up. But we have a ref on the page and once 354 * that page is locked, the mapping is pinned. 355 * 356 * We're allowed to run sleeping lock_page() here because we know the caller has 357 * __GFP_FS. 358 */ 359static void handle_write_error(struct address_space *mapping, 360 struct page *page, int error) 361{ 362 lock_page(page); 363 if (page_mapping(page) == mapping) 364 mapping_set_error(mapping, error); 365 unlock_page(page); 366} 367 368/* possible outcome of pageout() */ 369typedef enum { 370 /* failed to write page out, page is locked */ 371 PAGE_KEEP, 372 /* move page to the active list, page is locked */ 373 PAGE_ACTIVATE, 374 /* page has been sent to the disk successfully, page is unlocked */ 375 PAGE_SUCCESS, 376 /* page is clean and locked */ 377 PAGE_CLEAN, 378} pageout_t; 379 380/* 381 * pageout is called by shrink_page_list() for each dirty page. 382 * Calls ->writepage(). 383 */ 384static pageout_t pageout(struct page *page, struct address_space *mapping, 385 struct scan_control *sc) 386{ 387 /* 388 * If the page is dirty, only perform writeback if that write 389 * will be non-blocking. To prevent this allocation from being 390 * stalled by pagecache activity. But note that there may be 391 * stalls if we need to run get_block(). We could test 392 * PagePrivate for that. 393 * 394 * If this process is currently in __generic_file_aio_write() against 395 * this page's queue, we can perform writeback even if that 396 * will block. 397 * 398 * If the page is swapcache, write it back even if that would 399 * block, for some throttling. This happens by accident, because 400 * swap_backing_dev_info is bust: it doesn't reflect the 401 * congestion state of the swapdevs. Easy to fix, if needed. 402 */ 403 if (!is_page_cache_freeable(page)) 404 return PAGE_KEEP; 405 if (!mapping) { 406 /* 407 * Some data journaling orphaned pages can have 408 * page->mapping == NULL while being dirty with clean buffers. 409 */ 410 if (page_has_private(page)) { 411 if (try_to_free_buffers(page)) { 412 ClearPageDirty(page); 413 printk("%s: orphaned page\n", __func__); 414 return PAGE_CLEAN; 415 } 416 } 417 return PAGE_KEEP; 418 } 419 if (mapping->a_ops->writepage == NULL) 420 return PAGE_ACTIVATE; 421 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 422 return PAGE_KEEP; 423 424 if (clear_page_dirty_for_io(page)) { 425 int res; 426 struct writeback_control wbc = { 427 .sync_mode = WB_SYNC_NONE, 428 .nr_to_write = SWAP_CLUSTER_MAX, 429 .range_start = 0, 430 .range_end = LLONG_MAX, 431 .for_reclaim = 1, 432 }; 433 434 SetPageReclaim(page); 435 res = mapping->a_ops->writepage(page, &wbc); 436 if (res < 0) 437 handle_write_error(mapping, page, res); 438 if (res == AOP_WRITEPAGE_ACTIVATE) { 439 ClearPageReclaim(page); 440 return PAGE_ACTIVATE; 441 } 442 443 /* 444 * Wait on writeback if requested to. This happens when 445 * direct reclaiming a large contiguous area and the 446 * first attempt to free a range of pages fails. 447 */ 448 if (PageWriteback(page) && 449 (sc->reclaim_mode & RECLAIM_MODE_SYNC)) 450 wait_on_page_writeback(page); 451 452 if (!PageWriteback(page)) { 453 /* synchronous write or broken a_ops? */ 454 ClearPageReclaim(page); 455 } 456 trace_mm_vmscan_writepage(page, 457 trace_reclaim_flags(page, sc->reclaim_mode)); 458 inc_zone_page_state(page, NR_VMSCAN_WRITE); 459 return PAGE_SUCCESS; 460 } 461 462 return PAGE_CLEAN; 463} 464 465/* 466 * Same as remove_mapping, but if the page is removed from the mapping, it 467 * gets returned with a refcount of 0. 468 */ 469static int __remove_mapping(struct address_space *mapping, struct page *page) 470{ 471 BUG_ON(!PageLocked(page)); 472 BUG_ON(mapping != page_mapping(page)); 473 474 spin_lock_irq(&mapping->tree_lock); 475 /* 476 * The non racy check for a busy page. 477 * 478 * Must be careful with the order of the tests. When someone has 479 * a ref to the page, it may be possible that they dirty it then 480 * drop the reference. So if PageDirty is tested before page_count 481 * here, then the following race may occur: 482 * 483 * get_user_pages(&page); 484 * [user mapping goes away] 485 * write_to(page); 486 * !PageDirty(page) [good] 487 * SetPageDirty(page); 488 * put_page(page); 489 * !page_count(page) [good, discard it] 490 * 491 * [oops, our write_to data is lost] 492 * 493 * Reversing the order of the tests ensures such a situation cannot 494 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 495 * load is not satisfied before that of page->_count. 496 * 497 * Note that if SetPageDirty is always performed via set_page_dirty, 498 * and thus under tree_lock, then this ordering is not required. 499 */ 500 if (!page_freeze_refs(page, 2)) 501 goto cannot_free; 502 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 503 if (unlikely(PageDirty(page))) { 504 page_unfreeze_refs(page, 2); 505 goto cannot_free; 506 } 507 508 if (PageSwapCache(page)) { 509 swp_entry_t swap = { .val = page_private(page) }; 510 __delete_from_swap_cache(page); 511 spin_unlock_irq(&mapping->tree_lock); 512 swapcache_free(swap, page); 513 } else { 514 void (*freepage)(struct page *); 515 516 freepage = mapping->a_ops->freepage; 517 518 __delete_from_page_cache(page); 519 spin_unlock_irq(&mapping->tree_lock); 520 mem_cgroup_uncharge_cache_page(page); 521 522 if (freepage != NULL) 523 freepage(page); 524 } 525 526 return 1; 527 528cannot_free: 529 spin_unlock_irq(&mapping->tree_lock); 530 return 0; 531} 532 533/* 534 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 535 * someone else has a ref on the page, abort and return 0. If it was 536 * successfully detached, return 1. Assumes the caller has a single ref on 537 * this page. 538 */ 539int remove_mapping(struct address_space *mapping, struct page *page) 540{ 541 if (__remove_mapping(mapping, page)) { 542 /* 543 * Unfreezing the refcount with 1 rather than 2 effectively 544 * drops the pagecache ref for us without requiring another 545 * atomic operation. 546 */ 547 page_unfreeze_refs(page, 1); 548 return 1; 549 } 550 return 0; 551} 552 553/** 554 * putback_lru_page - put previously isolated page onto appropriate LRU list 555 * @page: page to be put back to appropriate lru list 556 * 557 * Add previously isolated @page to appropriate LRU list. 558 * Page may still be unevictable for other reasons. 559 * 560 * lru_lock must not be held, interrupts must be enabled. 561 */ 562void putback_lru_page(struct page *page) 563{ 564 int lru; 565 int active = !!TestClearPageActive(page); 566 int was_unevictable = PageUnevictable(page); 567 568 VM_BUG_ON(PageLRU(page)); 569 570redo: 571 ClearPageUnevictable(page); 572 573 if (page_evictable(page, NULL)) { 574 /* 575 * For evictable pages, we can use the cache. 576 * In event of a race, worst case is we end up with an 577 * unevictable page on [in]active list. 578 * We know how to handle that. 579 */ 580 lru = active + page_lru_base_type(page); 581 lru_cache_add_lru(page, lru); 582 } else { 583 /* 584 * Put unevictable pages directly on zone's unevictable 585 * list. 586 */ 587 lru = LRU_UNEVICTABLE; 588 add_page_to_unevictable_list(page); 589 /* 590 * When racing with an mlock clearing (page is 591 * unlocked), make sure that if the other thread does 592 * not observe our setting of PG_lru and fails 593 * isolation, we see PG_mlocked cleared below and move 594 * the page back to the evictable list. 595 * 596 * The other side is TestClearPageMlocked(). 597 */ 598 smp_mb(); 599 } 600 601 /* 602 * page's status can change while we move it among lru. If an evictable 603 * page is on unevictable list, it never be freed. To avoid that, 604 * check after we added it to the list, again. 605 */ 606 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 607 if (!isolate_lru_page(page)) { 608 put_page(page); 609 goto redo; 610 } 611 /* This means someone else dropped this page from LRU 612 * So, it will be freed or putback to LRU again. There is 613 * nothing to do here. 614 */ 615 } 616 617 if (was_unevictable && lru != LRU_UNEVICTABLE) 618 count_vm_event(UNEVICTABLE_PGRESCUED); 619 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 620 count_vm_event(UNEVICTABLE_PGCULLED); 621 622 put_page(page); /* drop ref from isolate */ 623} 624 625enum page_references { 626 PAGEREF_RECLAIM, 627 PAGEREF_RECLAIM_CLEAN, 628 PAGEREF_KEEP, 629 PAGEREF_ACTIVATE, 630}; 631 632static enum page_references page_check_references(struct page *page, 633 struct scan_control *sc) 634{ 635 int referenced_ptes, referenced_page; 636 unsigned long vm_flags; 637 638 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 639 referenced_page = TestClearPageReferenced(page); 640 641 /* Lumpy reclaim - ignore references */ 642 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 643 return PAGEREF_RECLAIM; 644 645 /* 646 * Mlock lost the isolation race with us. Let try_to_unmap() 647 * move the page to the unevictable list. 648 */ 649 if (vm_flags & VM_LOCKED) 650 return PAGEREF_RECLAIM; 651 652 if (referenced_ptes) { 653 if (PageAnon(page)) 654 return PAGEREF_ACTIVATE; 655 /* 656 * All mapped pages start out with page table 657 * references from the instantiating fault, so we need 658 * to look twice if a mapped file page is used more 659 * than once. 660 * 661 * Mark it and spare it for another trip around the 662 * inactive list. Another page table reference will 663 * lead to its activation. 664 * 665 * Note: the mark is set for activated pages as well 666 * so that recently deactivated but used pages are 667 * quickly recovered. 668 */ 669 SetPageReferenced(page); 670 671 if (referenced_page) 672 return PAGEREF_ACTIVATE; 673 674 return PAGEREF_KEEP; 675 } 676 677 /* Reclaim if clean, defer dirty pages to writeback */ 678 if (referenced_page && !PageSwapBacked(page)) 679 return PAGEREF_RECLAIM_CLEAN; 680 681 return PAGEREF_RECLAIM; 682} 683 684static noinline_for_stack void free_page_list(struct list_head *free_pages) 685{ 686 struct pagevec freed_pvec; 687 struct page *page, *tmp; 688 689 pagevec_init(&freed_pvec, 1); 690 691 list_for_each_entry_safe(page, tmp, free_pages, lru) { 692 list_del(&page->lru); 693 if (!pagevec_add(&freed_pvec, page)) { 694 __pagevec_free(&freed_pvec); 695 pagevec_reinit(&freed_pvec); 696 } 697 } 698 699 pagevec_free(&freed_pvec); 700} 701 702/* 703 * shrink_page_list() returns the number of reclaimed pages 704 */ 705static unsigned long shrink_page_list(struct list_head *page_list, 706 struct zone *zone, 707 struct scan_control *sc) 708{ 709 LIST_HEAD(ret_pages); 710 LIST_HEAD(free_pages); 711 int pgactivate = 0; 712 unsigned long nr_dirty = 0; 713 unsigned long nr_congested = 0; 714 unsigned long nr_reclaimed = 0; 715 716 cond_resched(); 717 718 while (!list_empty(page_list)) { 719 enum page_references references; 720 struct address_space *mapping; 721 struct page *page; 722 int may_enter_fs; 723 724 cond_resched(); 725 726 page = lru_to_page(page_list); 727 list_del(&page->lru); 728 729 if (!trylock_page(page)) 730 goto keep; 731 732 VM_BUG_ON(PageActive(page)); 733 VM_BUG_ON(page_zone(page) != zone); 734 735 sc->nr_scanned++; 736 737 if (unlikely(!page_evictable(page, NULL))) 738 goto cull_mlocked; 739 740 if (!sc->may_unmap && page_mapped(page)) 741 goto keep_locked; 742 743 /* Double the slab pressure for mapped and swapcache pages */ 744 if (page_mapped(page) || PageSwapCache(page)) 745 sc->nr_scanned++; 746 747 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 748 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 749 750 if (PageWriteback(page)) { 751 /* 752 * Synchronous reclaim is performed in two passes, 753 * first an asynchronous pass over the list to 754 * start parallel writeback, and a second synchronous 755 * pass to wait for the IO to complete. Wait here 756 * for any page for which writeback has already 757 * started. 758 */ 759 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 760 may_enter_fs) 761 wait_on_page_writeback(page); 762 else { 763 unlock_page(page); 764 goto keep_lumpy; 765 } 766 } 767 768 references = page_check_references(page, sc); 769 switch (references) { 770 case PAGEREF_ACTIVATE: 771 goto activate_locked; 772 case PAGEREF_KEEP: 773 goto keep_locked; 774 case PAGEREF_RECLAIM: 775 case PAGEREF_RECLAIM_CLEAN: 776 ; /* try to reclaim the page below */ 777 } 778 779 /* 780 * Anonymous process memory has backing store? 781 * Try to allocate it some swap space here. 782 */ 783 if (PageAnon(page) && !PageSwapCache(page)) { 784 if (!(sc->gfp_mask & __GFP_IO)) 785 goto keep_locked; 786 if (!add_to_swap(page)) 787 goto activate_locked; 788 may_enter_fs = 1; 789 } 790 791 mapping = page_mapping(page); 792 793 /* 794 * The page is mapped into the page tables of one or more 795 * processes. Try to unmap it here. 796 */ 797 if (page_mapped(page) && mapping) { 798 switch (try_to_unmap(page, TTU_UNMAP)) { 799 case SWAP_FAIL: 800 goto activate_locked; 801 case SWAP_AGAIN: 802 goto keep_locked; 803 case SWAP_MLOCK: 804 goto cull_mlocked; 805 case SWAP_SUCCESS: 806 ; /* try to free the page below */ 807 } 808 } 809 810 if (PageDirty(page)) { 811 nr_dirty++; 812 813 if (references == PAGEREF_RECLAIM_CLEAN) 814 goto keep_locked; 815 if (!may_enter_fs) 816 goto keep_locked; 817 if (!sc->may_writepage) 818 goto keep_locked; 819 820 /* Page is dirty, try to write it out here */ 821 switch (pageout(page, mapping, sc)) { 822 case PAGE_KEEP: 823 nr_congested++; 824 goto keep_locked; 825 case PAGE_ACTIVATE: 826 goto activate_locked; 827 case PAGE_SUCCESS: 828 if (PageWriteback(page)) 829 goto keep_lumpy; 830 if (PageDirty(page)) 831 goto keep; 832 833 /* 834 * A synchronous write - probably a ramdisk. Go 835 * ahead and try to reclaim the page. 836 */ 837 if (!trylock_page(page)) 838 goto keep; 839 if (PageDirty(page) || PageWriteback(page)) 840 goto keep_locked; 841 mapping = page_mapping(page); 842 case PAGE_CLEAN: 843 ; /* try to free the page below */ 844 } 845 } 846 847 /* 848 * If the page has buffers, try to free the buffer mappings 849 * associated with this page. If we succeed we try to free 850 * the page as well. 851 * 852 * We do this even if the page is PageDirty(). 853 * try_to_release_page() does not perform I/O, but it is 854 * possible for a page to have PageDirty set, but it is actually 855 * clean (all its buffers are clean). This happens if the 856 * buffers were written out directly, with submit_bh(). ext3 857 * will do this, as well as the blockdev mapping. 858 * try_to_release_page() will discover that cleanness and will 859 * drop the buffers and mark the page clean - it can be freed. 860 * 861 * Rarely, pages can have buffers and no ->mapping. These are 862 * the pages which were not successfully invalidated in 863 * truncate_complete_page(). We try to drop those buffers here 864 * and if that worked, and the page is no longer mapped into 865 * process address space (page_count == 1) it can be freed. 866 * Otherwise, leave the page on the LRU so it is swappable. 867 */ 868 if (page_has_private(page)) { 869 if (!try_to_release_page(page, sc->gfp_mask)) 870 goto activate_locked; 871 if (!mapping && page_count(page) == 1) { 872 unlock_page(page); 873 if (put_page_testzero(page)) 874 goto free_it; 875 else { 876 /* 877 * rare race with speculative reference. 878 * the speculative reference will free 879 * this page shortly, so we may 880 * increment nr_reclaimed here (and 881 * leave it off the LRU). 882 */ 883 nr_reclaimed++; 884 continue; 885 } 886 } 887 } 888 889 if (!mapping || !__remove_mapping(mapping, page)) 890 goto keep_locked; 891 892 /* 893 * At this point, we have no other references and there is 894 * no way to pick any more up (removed from LRU, removed 895 * from pagecache). Can use non-atomic bitops now (and 896 * we obviously don't have to worry about waking up a process 897 * waiting on the page lock, because there are no references. 898 */ 899 __clear_page_locked(page); 900free_it: 901 nr_reclaimed++; 902 903 /* 904 * Is there need to periodically free_page_list? It would 905 * appear not as the counts should be low 906 */ 907 list_add(&page->lru, &free_pages); 908 continue; 909 910cull_mlocked: 911 if (PageSwapCache(page)) 912 try_to_free_swap(page); 913 unlock_page(page); 914 putback_lru_page(page); 915 reset_reclaim_mode(sc); 916 continue; 917 918activate_locked: 919 /* Not a candidate for swapping, so reclaim swap space. */ 920 if (PageSwapCache(page) && vm_swap_full()) 921 try_to_free_swap(page); 922 VM_BUG_ON(PageActive(page)); 923 SetPageActive(page); 924 pgactivate++; 925keep_locked: 926 unlock_page(page); 927keep: 928 reset_reclaim_mode(sc); 929keep_lumpy: 930 list_add(&page->lru, &ret_pages); 931 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 932 } 933 934 /* 935 * Tag a zone as congested if all the dirty pages encountered were 936 * backed by a congested BDI. In this case, reclaimers should just 937 * back off and wait for congestion to clear because further reclaim 938 * will encounter the same problem 939 */ 940 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) 941 zone_set_flag(zone, ZONE_CONGESTED); 942 943 free_page_list(&free_pages); 944 945 list_splice(&ret_pages, page_list); 946 count_vm_events(PGACTIVATE, pgactivate); 947 return nr_reclaimed; 948} 949 950/* 951 * Attempt to remove the specified page from its LRU. Only take this page 952 * if it is of the appropriate PageActive status. Pages which are being 953 * freed elsewhere are also ignored. 954 * 955 * page: page to consider 956 * mode: one of the LRU isolation modes defined above 957 * 958 * returns 0 on success, -ve errno on failure. 959 */ 960int __isolate_lru_page(struct page *page, int mode, int file) 961{ 962 int ret = -EINVAL; 963 964 /* Only take pages on the LRU. */ 965 if (!PageLRU(page)) 966 return ret; 967 968 /* 969 * When checking the active state, we need to be sure we are 970 * dealing with comparible boolean values. Take the logical not 971 * of each. 972 */ 973 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 974 return ret; 975 976 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 977 return ret; 978 979 /* 980 * When this function is being called for lumpy reclaim, we 981 * initially look into all LRU pages, active, inactive and 982 * unevictable; only give shrink_page_list evictable pages. 983 */ 984 if (PageUnevictable(page)) 985 return ret; 986 987 ret = -EBUSY; 988 989 if (likely(get_page_unless_zero(page))) { 990 /* 991 * Be careful not to clear PageLRU until after we're 992 * sure the page is not being freed elsewhere -- the 993 * page release code relies on it. 994 */ 995 ClearPageLRU(page); 996 ret = 0; 997 } 998 999 return ret; 1000} 1001 1002/* 1003 * zone->lru_lock is heavily contended. Some of the functions that 1004 * shrink the lists perform better by taking out a batch of pages 1005 * and working on them outside the LRU lock. 1006 * 1007 * For pagecache intensive workloads, this function is the hottest 1008 * spot in the kernel (apart from copy_*_user functions). 1009 * 1010 * Appropriate locks must be held before calling this function. 1011 * 1012 * @nr_to_scan: The number of pages to look through on the list. 1013 * @src: The LRU list to pull pages off. 1014 * @dst: The temp list to put pages on to. 1015 * @scanned: The number of pages that were scanned. 1016 * @order: The caller's attempted allocation order 1017 * @mode: One of the LRU isolation modes 1018 * @file: True [1] if isolating file [!anon] pages 1019 * 1020 * returns how many pages were moved onto *@dst. 1021 */ 1022static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1023 struct list_head *src, struct list_head *dst, 1024 unsigned long *scanned, int order, int mode, int file) 1025{ 1026 unsigned long nr_taken = 0; 1027 unsigned long nr_lumpy_taken = 0; 1028 unsigned long nr_lumpy_dirty = 0; 1029 unsigned long nr_lumpy_failed = 0; 1030 unsigned long scan; 1031 1032 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1033 struct page *page; 1034 unsigned long pfn; 1035 unsigned long end_pfn; 1036 unsigned long page_pfn; 1037 int zone_id; 1038 1039 page = lru_to_page(src); 1040 prefetchw_prev_lru_page(page, src, flags); 1041 1042 VM_BUG_ON(!PageLRU(page)); 1043 1044 switch (__isolate_lru_page(page, mode, file)) { 1045 case 0: 1046 list_move(&page->lru, dst); 1047 mem_cgroup_del_lru(page); 1048 nr_taken += hpage_nr_pages(page); 1049 break; 1050 1051 case -EBUSY: 1052 /* else it is being freed elsewhere */ 1053 list_move(&page->lru, src); 1054 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1055 continue; 1056 1057 default: 1058 BUG(); 1059 } 1060 1061 if (!order) 1062 continue; 1063 1064 /* 1065 * Attempt to take all pages in the order aligned region 1066 * surrounding the tag page. Only take those pages of 1067 * the same active state as that tag page. We may safely 1068 * round the target page pfn down to the requested order 1069 * as the mem_map is guaranteed valid out to MAX_ORDER, 1070 * where that page is in a different zone we will detect 1071 * it from its zone id and abort this block scan. 1072 */ 1073 zone_id = page_zone_id(page); 1074 page_pfn = page_to_pfn(page); 1075 pfn = page_pfn & ~((1 << order) - 1); 1076 end_pfn = pfn + (1 << order); 1077 for (; pfn < end_pfn; pfn++) { 1078 struct page *cursor_page; 1079 1080 /* The target page is in the block, ignore it. */ 1081 if (unlikely(pfn == page_pfn)) 1082 continue; 1083 1084 /* Avoid holes within the zone. */ 1085 if (unlikely(!pfn_valid_within(pfn))) 1086 break; 1087 1088 cursor_page = pfn_to_page(pfn); 1089 1090 /* Check that we have not crossed a zone boundary. */ 1091 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1092 break; 1093 1094 /* 1095 * If we don't have enough swap space, reclaiming of 1096 * anon page which don't already have a swap slot is 1097 * pointless. 1098 */ 1099 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1100 !PageSwapCache(cursor_page)) 1101 break; 1102 1103 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1104 list_move(&cursor_page->lru, dst); 1105 mem_cgroup_del_lru(cursor_page); 1106 nr_taken += hpage_nr_pages(page); 1107 nr_lumpy_taken++; 1108 if (PageDirty(cursor_page)) 1109 nr_lumpy_dirty++; 1110 scan++; 1111 } else { 1112 /* the page is freed already. */ 1113 if (!page_count(cursor_page)) 1114 continue; 1115 break; 1116 } 1117 } 1118 1119 /* If we break out of the loop above, lumpy reclaim failed */ 1120 if (pfn < end_pfn) 1121 nr_lumpy_failed++; 1122 } 1123 1124 *scanned = scan; 1125 1126 trace_mm_vmscan_lru_isolate(order, 1127 nr_to_scan, scan, 1128 nr_taken, 1129 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1130 mode); 1131 return nr_taken; 1132} 1133 1134static unsigned long isolate_pages_global(unsigned long nr, 1135 struct list_head *dst, 1136 unsigned long *scanned, int order, 1137 int mode, struct zone *z, 1138 int active, int file) 1139{ 1140 int lru = LRU_BASE; 1141 if (active) 1142 lru += LRU_ACTIVE; 1143 if (file) 1144 lru += LRU_FILE; 1145 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1146 mode, file); 1147} 1148 1149/* 1150 * clear_active_flags() is a helper for shrink_active_list(), clearing 1151 * any active bits from the pages in the list. 1152 */ 1153static unsigned long clear_active_flags(struct list_head *page_list, 1154 unsigned int *count) 1155{ 1156 int nr_active = 0; 1157 int lru; 1158 struct page *page; 1159 1160 list_for_each_entry(page, page_list, lru) { 1161 int numpages = hpage_nr_pages(page); 1162 lru = page_lru_base_type(page); 1163 if (PageActive(page)) { 1164 lru += LRU_ACTIVE; 1165 ClearPageActive(page); 1166 nr_active += numpages; 1167 } 1168 if (count) 1169 count[lru] += numpages; 1170 } 1171 1172 return nr_active; 1173} 1174 1175/** 1176 * isolate_lru_page - tries to isolate a page from its LRU list 1177 * @page: page to isolate from its LRU list 1178 * 1179 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1180 * vmstat statistic corresponding to whatever LRU list the page was on. 1181 * 1182 * Returns 0 if the page was removed from an LRU list. 1183 * Returns -EBUSY if the page was not on an LRU list. 1184 * 1185 * The returned page will have PageLRU() cleared. If it was found on 1186 * the active list, it will have PageActive set. If it was found on 1187 * the unevictable list, it will have the PageUnevictable bit set. That flag 1188 * may need to be cleared by the caller before letting the page go. 1189 * 1190 * The vmstat statistic corresponding to the list on which the page was 1191 * found will be decremented. 1192 * 1193 * Restrictions: 1194 * (1) Must be called with an elevated refcount on the page. This is a 1195 * fundamentnal difference from isolate_lru_pages (which is called 1196 * without a stable reference). 1197 * (2) the lru_lock must not be held. 1198 * (3) interrupts must be enabled. 1199 */ 1200int isolate_lru_page(struct page *page) 1201{ 1202 int ret = -EBUSY; 1203 1204 if (PageLRU(page)) { 1205 struct zone *zone = page_zone(page); 1206 1207 spin_lock_irq(&zone->lru_lock); 1208 if (PageLRU(page) && get_page_unless_zero(page)) { 1209 int lru = page_lru(page); 1210 ret = 0; 1211 ClearPageLRU(page); 1212 1213 del_page_from_lru_list(zone, page, lru); 1214 } 1215 spin_unlock_irq(&zone->lru_lock); 1216 } 1217 return ret; 1218} 1219 1220/* 1221 * Are there way too many processes in the direct reclaim path already? 1222 */ 1223static int too_many_isolated(struct zone *zone, int file, 1224 struct scan_control *sc) 1225{ 1226 unsigned long inactive, isolated; 1227 1228 if (current_is_kswapd()) 1229 return 0; 1230 1231 if (!scanning_global_lru(sc)) 1232 return 0; 1233 1234 if (file) { 1235 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1236 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1237 } else { 1238 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1239 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1240 } 1241 1242 return isolated > inactive; 1243} 1244 1245/* 1246 * TODO: Try merging with migrations version of putback_lru_pages 1247 */ 1248static noinline_for_stack void 1249putback_lru_pages(struct zone *zone, struct scan_control *sc, 1250 unsigned long nr_anon, unsigned long nr_file, 1251 struct list_head *page_list) 1252{ 1253 struct page *page; 1254 struct pagevec pvec; 1255 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1256 1257 pagevec_init(&pvec, 1); 1258 1259 /* 1260 * Put back any unfreeable pages. 1261 */ 1262 spin_lock(&zone->lru_lock); 1263 while (!list_empty(page_list)) { 1264 int lru; 1265 page = lru_to_page(page_list); 1266 VM_BUG_ON(PageLRU(page)); 1267 list_del(&page->lru); 1268 if (unlikely(!page_evictable(page, NULL))) { 1269 spin_unlock_irq(&zone->lru_lock); 1270 putback_lru_page(page); 1271 spin_lock_irq(&zone->lru_lock); 1272 continue; 1273 } 1274 SetPageLRU(page); 1275 lru = page_lru(page); 1276 add_page_to_lru_list(zone, page, lru); 1277 if (is_active_lru(lru)) { 1278 int file = is_file_lru(lru); 1279 int numpages = hpage_nr_pages(page); 1280 reclaim_stat->recent_rotated[file] += numpages; 1281 } 1282 if (!pagevec_add(&pvec, page)) { 1283 spin_unlock_irq(&zone->lru_lock); 1284 __pagevec_release(&pvec); 1285 spin_lock_irq(&zone->lru_lock); 1286 } 1287 } 1288 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1289 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1290 1291 spin_unlock_irq(&zone->lru_lock); 1292 pagevec_release(&pvec); 1293} 1294 1295static noinline_for_stack void update_isolated_counts(struct zone *zone, 1296 struct scan_control *sc, 1297 unsigned long *nr_anon, 1298 unsigned long *nr_file, 1299 struct list_head *isolated_list) 1300{ 1301 unsigned long nr_active; 1302 unsigned int count[NR_LRU_LISTS] = { 0, }; 1303 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1304 1305 nr_active = clear_active_flags(isolated_list, count); 1306 __count_vm_events(PGDEACTIVATE, nr_active); 1307 1308 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1309 -count[LRU_ACTIVE_FILE]); 1310 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1311 -count[LRU_INACTIVE_FILE]); 1312 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1313 -count[LRU_ACTIVE_ANON]); 1314 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1315 -count[LRU_INACTIVE_ANON]); 1316 1317 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1318 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1319 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1320 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1321 1322 reclaim_stat->recent_scanned[0] += *nr_anon; 1323 reclaim_stat->recent_scanned[1] += *nr_file; 1324} 1325 1326/* 1327 * Returns true if the caller should wait to clean dirty/writeback pages. 1328 * 1329 * If we are direct reclaiming for contiguous pages and we do not reclaim 1330 * everything in the list, try again and wait for writeback IO to complete. 1331 * This will stall high-order allocations noticeably. Only do that when really 1332 * need to free the pages under high memory pressure. 1333 */ 1334static inline bool should_reclaim_stall(unsigned long nr_taken, 1335 unsigned long nr_freed, 1336 int priority, 1337 struct scan_control *sc) 1338{ 1339 int lumpy_stall_priority; 1340 1341 /* kswapd should not stall on sync IO */ 1342 if (current_is_kswapd()) 1343 return false; 1344 1345 /* Only stall on lumpy reclaim */ 1346 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1347 return false; 1348 1349 /* If we have relaimed everything on the isolated list, no stall */ 1350 if (nr_freed == nr_taken) 1351 return false; 1352 1353 /* 1354 * For high-order allocations, there are two stall thresholds. 1355 * High-cost allocations stall immediately where as lower 1356 * order allocations such as stacks require the scanning 1357 * priority to be much higher before stalling. 1358 */ 1359 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1360 lumpy_stall_priority = DEF_PRIORITY; 1361 else 1362 lumpy_stall_priority = DEF_PRIORITY / 3; 1363 1364 return priority <= lumpy_stall_priority; 1365} 1366 1367/* 1368 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1369 * of reclaimed pages 1370 */ 1371static noinline_for_stack unsigned long 1372shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1373 struct scan_control *sc, int priority, int file) 1374{ 1375 LIST_HEAD(page_list); 1376 unsigned long nr_scanned; 1377 unsigned long nr_reclaimed = 0; 1378 unsigned long nr_taken; 1379 unsigned long nr_anon; 1380 unsigned long nr_file; 1381 1382 while (unlikely(too_many_isolated(zone, file, sc))) { 1383 congestion_wait(BLK_RW_ASYNC, HZ/10); 1384 1385 /* We are about to die and free our memory. Return now. */ 1386 if (fatal_signal_pending(current)) 1387 return SWAP_CLUSTER_MAX; 1388 } 1389 1390 set_reclaim_mode(priority, sc, false); 1391 lru_add_drain(); 1392 spin_lock_irq(&zone->lru_lock); 1393 1394 if (scanning_global_lru(sc)) { 1395 nr_taken = isolate_pages_global(nr_to_scan, 1396 &page_list, &nr_scanned, sc->order, 1397 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1398 ISOLATE_BOTH : ISOLATE_INACTIVE, 1399 zone, 0, file); 1400 zone->pages_scanned += nr_scanned; 1401 if (current_is_kswapd()) 1402 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1403 nr_scanned); 1404 else 1405 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1406 nr_scanned); 1407 } else { 1408 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1409 &page_list, &nr_scanned, sc->order, 1410 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1411 ISOLATE_BOTH : ISOLATE_INACTIVE, 1412 zone, sc->mem_cgroup, 1413 0, file); 1414 /* 1415 * mem_cgroup_isolate_pages() keeps track of 1416 * scanned pages on its own. 1417 */ 1418 } 1419 1420 if (nr_taken == 0) { 1421 spin_unlock_irq(&zone->lru_lock); 1422 return 0; 1423 } 1424 1425 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1426 1427 spin_unlock_irq(&zone->lru_lock); 1428 1429 nr_reclaimed = shrink_page_list(&page_list, zone, sc); 1430 1431 /* Check if we should syncronously wait for writeback */ 1432 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1433 set_reclaim_mode(priority, sc, true); 1434 nr_reclaimed += shrink_page_list(&page_list, zone, sc); 1435 } 1436 1437 local_irq_disable(); 1438 if (current_is_kswapd()) 1439 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1440 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1441 1442 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1443 1444 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1445 zone_idx(zone), 1446 nr_scanned, nr_reclaimed, 1447 priority, 1448 trace_shrink_flags(file, sc->reclaim_mode)); 1449 return nr_reclaimed; 1450} 1451 1452/* 1453 * This moves pages from the active list to the inactive list. 1454 * 1455 * We move them the other way if the page is referenced by one or more 1456 * processes, from rmap. 1457 * 1458 * If the pages are mostly unmapped, the processing is fast and it is 1459 * appropriate to hold zone->lru_lock across the whole operation. But if 1460 * the pages are mapped, the processing is slow (page_referenced()) so we 1461 * should drop zone->lru_lock around each page. It's impossible to balance 1462 * this, so instead we remove the pages from the LRU while processing them. 1463 * It is safe to rely on PG_active against the non-LRU pages in here because 1464 * nobody will play with that bit on a non-LRU page. 1465 * 1466 * The downside is that we have to touch page->_count against each page. 1467 * But we had to alter page->flags anyway. 1468 */ 1469 1470static void move_active_pages_to_lru(struct zone *zone, 1471 struct list_head *list, 1472 enum lru_list lru) 1473{ 1474 unsigned long pgmoved = 0; 1475 struct pagevec pvec; 1476 struct page *page; 1477 1478 pagevec_init(&pvec, 1); 1479 1480 while (!list_empty(list)) { 1481 page = lru_to_page(list); 1482 1483 VM_BUG_ON(PageLRU(page)); 1484 SetPageLRU(page); 1485 1486 list_move(&page->lru, &zone->lru[lru].list); 1487 mem_cgroup_add_lru_list(page, lru); 1488 pgmoved += hpage_nr_pages(page); 1489 1490 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1491 spin_unlock_irq(&zone->lru_lock); 1492 if (buffer_heads_over_limit) 1493 pagevec_strip(&pvec); 1494 __pagevec_release(&pvec); 1495 spin_lock_irq(&zone->lru_lock); 1496 } 1497 } 1498 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1499 if (!is_active_lru(lru)) 1500 __count_vm_events(PGDEACTIVATE, pgmoved); 1501} 1502 1503static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1504 struct scan_control *sc, int priority, int file) 1505{ 1506 unsigned long nr_taken; 1507 unsigned long pgscanned; 1508 unsigned long vm_flags; 1509 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1510 LIST_HEAD(l_active); 1511 LIST_HEAD(l_inactive); 1512 struct page *page; 1513 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1514 unsigned long nr_rotated = 0; 1515 1516 lru_add_drain(); 1517 spin_lock_irq(&zone->lru_lock); 1518 if (scanning_global_lru(sc)) { 1519 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1520 &pgscanned, sc->order, 1521 ISOLATE_ACTIVE, zone, 1522 1, file); 1523 zone->pages_scanned += pgscanned; 1524 } else { 1525 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1526 &pgscanned, sc->order, 1527 ISOLATE_ACTIVE, zone, 1528 sc->mem_cgroup, 1, file); 1529 /* 1530 * mem_cgroup_isolate_pages() keeps track of 1531 * scanned pages on its own. 1532 */ 1533 } 1534 1535 reclaim_stat->recent_scanned[file] += nr_taken; 1536 1537 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1538 if (file) 1539 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1540 else 1541 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1542 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1543 spin_unlock_irq(&zone->lru_lock); 1544 1545 while (!list_empty(&l_hold)) { 1546 cond_resched(); 1547 page = lru_to_page(&l_hold); 1548 list_del(&page->lru); 1549 1550 if (unlikely(!page_evictable(page, NULL))) { 1551 putback_lru_page(page); 1552 continue; 1553 } 1554 1555 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1556 nr_rotated += hpage_nr_pages(page); 1557 /* 1558 * Identify referenced, file-backed active pages and 1559 * give them one more trip around the active list. So 1560 * that executable code get better chances to stay in 1561 * memory under moderate memory pressure. Anon pages 1562 * are not likely to be evicted by use-once streaming 1563 * IO, plus JVM can create lots of anon VM_EXEC pages, 1564 * so we ignore them here. 1565 */ 1566 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1567 list_add(&page->lru, &l_active); 1568 continue; 1569 } 1570 } 1571 1572 ClearPageActive(page); /* we are de-activating */ 1573 list_add(&page->lru, &l_inactive); 1574 } 1575 1576 /* 1577 * Move pages back to the lru list. 1578 */ 1579 spin_lock_irq(&zone->lru_lock); 1580 /* 1581 * Count referenced pages from currently used mappings as rotated, 1582 * even though only some of them are actually re-activated. This 1583 * helps balance scan pressure between file and anonymous pages in 1584 * get_scan_ratio. 1585 */ 1586 reclaim_stat->recent_rotated[file] += nr_rotated; 1587 1588 move_active_pages_to_lru(zone, &l_active, 1589 LRU_ACTIVE + file * LRU_FILE); 1590 move_active_pages_to_lru(zone, &l_inactive, 1591 LRU_BASE + file * LRU_FILE); 1592 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1593 spin_unlock_irq(&zone->lru_lock); 1594} 1595 1596#ifdef CONFIG_SWAP 1597static int inactive_anon_is_low_global(struct zone *zone) 1598{ 1599 unsigned long active, inactive; 1600 1601 active = zone_page_state(zone, NR_ACTIVE_ANON); 1602 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1603 1604 if (inactive * zone->inactive_ratio < active) 1605 return 1; 1606 1607 return 0; 1608} 1609 1610/** 1611 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1612 * @zone: zone to check 1613 * @sc: scan control of this context 1614 * 1615 * Returns true if the zone does not have enough inactive anon pages, 1616 * meaning some active anon pages need to be deactivated. 1617 */ 1618static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1619{ 1620 int low; 1621 1622 /* 1623 * If we don't have swap space, anonymous page deactivation 1624 * is pointless. 1625 */ 1626 if (!total_swap_pages) 1627 return 0; 1628 1629 if (scanning_global_lru(sc)) 1630 low = inactive_anon_is_low_global(zone); 1631 else 1632 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1633 return low; 1634} 1635#else 1636static inline int inactive_anon_is_low(struct zone *zone, 1637 struct scan_control *sc) 1638{ 1639 return 0; 1640} 1641#endif 1642 1643static int inactive_file_is_low_global(struct zone *zone) 1644{ 1645 unsigned long active, inactive; 1646 1647 active = zone_page_state(zone, NR_ACTIVE_FILE); 1648 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1649 1650 return (active > inactive); 1651} 1652 1653/** 1654 * inactive_file_is_low - check if file pages need to be deactivated 1655 * @zone: zone to check 1656 * @sc: scan control of this context 1657 * 1658 * When the system is doing streaming IO, memory pressure here 1659 * ensures that active file pages get deactivated, until more 1660 * than half of the file pages are on the inactive list. 1661 * 1662 * Once we get to that situation, protect the system's working 1663 * set from being evicted by disabling active file page aging. 1664 * 1665 * This uses a different ratio than the anonymous pages, because 1666 * the page cache uses a use-once replacement algorithm. 1667 */ 1668static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1669{ 1670 int low; 1671 1672 if (scanning_global_lru(sc)) 1673 low = inactive_file_is_low_global(zone); 1674 else 1675 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1676 return low; 1677} 1678 1679static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1680 int file) 1681{ 1682 if (file) 1683 return inactive_file_is_low(zone, sc); 1684 else 1685 return inactive_anon_is_low(zone, sc); 1686} 1687 1688static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1689 struct zone *zone, struct scan_control *sc, int priority) 1690{ 1691 int file = is_file_lru(lru); 1692 1693 if (is_active_lru(lru)) { 1694 if (inactive_list_is_low(zone, sc, file)) 1695 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1696 return 0; 1697 } 1698 1699 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1700} 1701 1702/* 1703 * Smallish @nr_to_scan's are deposited in @nr_saved_scan, 1704 * until we collected @swap_cluster_max pages to scan. 1705 */ 1706static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, 1707 unsigned long *nr_saved_scan) 1708{ 1709 unsigned long nr; 1710 1711 *nr_saved_scan += nr_to_scan; 1712 nr = *nr_saved_scan; 1713 1714 if (nr >= SWAP_CLUSTER_MAX) 1715 *nr_saved_scan = 0; 1716 else 1717 nr = 0; 1718 1719 return nr; 1720} 1721 1722/* 1723 * Determine how aggressively the anon and file LRU lists should be 1724 * scanned. The relative value of each set of LRU lists is determined 1725 * by looking at the fraction of the pages scanned we did rotate back 1726 * onto the active list instead of evict. 1727 * 1728 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1729 */ 1730static void get_scan_count(struct zone *zone, struct scan_control *sc, 1731 unsigned long *nr, int priority) 1732{ 1733 unsigned long anon, file, free; 1734 unsigned long anon_prio, file_prio; 1735 unsigned long ap, fp; 1736 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1737 u64 fraction[2], denominator; 1738 enum lru_list l; 1739 int noswap = 0; 1740 1741 /* If we have no swap space, do not bother scanning anon pages. */ 1742 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1743 noswap = 1; 1744 fraction[0] = 0; 1745 fraction[1] = 1; 1746 denominator = 1; 1747 goto out; 1748 } 1749 1750 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1751 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1752 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1753 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1754 1755 if (scanning_global_lru(sc)) { 1756 free = zone_page_state(zone, NR_FREE_PAGES); 1757 /* If we have very few page cache pages, 1758 force-scan anon pages. */ 1759 if (unlikely(file + free <= high_wmark_pages(zone))) { 1760 fraction[0] = 1; 1761 fraction[1] = 0; 1762 denominator = 1; 1763 goto out; 1764 } 1765 } 1766 1767 /* 1768 * With swappiness at 100, anonymous and file have the same priority. 1769 * This scanning priority is essentially the inverse of IO cost. 1770 */ 1771 anon_prio = sc->swappiness; 1772 file_prio = 200 - sc->swappiness; 1773 1774 /* 1775 * OK, so we have swap space and a fair amount of page cache 1776 * pages. We use the recently rotated / recently scanned 1777 * ratios to determine how valuable each cache is. 1778 * 1779 * Because workloads change over time (and to avoid overflow) 1780 * we keep these statistics as a floating average, which ends 1781 * up weighing recent references more than old ones. 1782 * 1783 * anon in [0], file in [1] 1784 */ 1785 spin_lock_irq(&zone->lru_lock); 1786 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1787 reclaim_stat->recent_scanned[0] /= 2; 1788 reclaim_stat->recent_rotated[0] /= 2; 1789 } 1790 1791 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1792 reclaim_stat->recent_scanned[1] /= 2; 1793 reclaim_stat->recent_rotated[1] /= 2; 1794 } 1795 1796 /* 1797 * The amount of pressure on anon vs file pages is inversely 1798 * proportional to the fraction of recently scanned pages on 1799 * each list that were recently referenced and in active use. 1800 */ 1801 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1802 ap /= reclaim_stat->recent_rotated[0] + 1; 1803 1804 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1805 fp /= reclaim_stat->recent_rotated[1] + 1; 1806 spin_unlock_irq(&zone->lru_lock); 1807 1808 fraction[0] = ap; 1809 fraction[1] = fp; 1810 denominator = ap + fp + 1; 1811out: 1812 for_each_evictable_lru(l) { 1813 int file = is_file_lru(l); 1814 unsigned long scan; 1815 1816 scan = zone_nr_lru_pages(zone, sc, l); 1817 if (priority || noswap) { 1818 scan >>= priority; 1819 scan = div64_u64(scan * fraction[file], denominator); 1820 } 1821 nr[l] = nr_scan_try_batch(scan, 1822 &reclaim_stat->nr_saved_scan[l]); 1823 } 1824} 1825 1826/* 1827 * Reclaim/compaction depends on a number of pages being freed. To avoid 1828 * disruption to the system, a small number of order-0 pages continue to be 1829 * rotated and reclaimed in the normal fashion. However, by the time we get 1830 * back to the allocator and call try_to_compact_zone(), we ensure that 1831 * there are enough free pages for it to be likely successful 1832 */ 1833static inline bool should_continue_reclaim(struct zone *zone, 1834 unsigned long nr_reclaimed, 1835 unsigned long nr_scanned, 1836 struct scan_control *sc) 1837{ 1838 unsigned long pages_for_compaction; 1839 unsigned long inactive_lru_pages; 1840 1841 /* If not in reclaim/compaction mode, stop */ 1842 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1843 return false; 1844 1845 /* Consider stopping depending on scan and reclaim activity */ 1846 if (sc->gfp_mask & __GFP_REPEAT) { 1847 /* 1848 * For __GFP_REPEAT allocations, stop reclaiming if the 1849 * full LRU list has been scanned and we are still failing 1850 * to reclaim pages. This full LRU scan is potentially 1851 * expensive but a __GFP_REPEAT caller really wants to succeed 1852 */ 1853 if (!nr_reclaimed && !nr_scanned) 1854 return false; 1855 } else { 1856 /* 1857 * For non-__GFP_REPEAT allocations which can presumably 1858 * fail without consequence, stop if we failed to reclaim 1859 * any pages from the last SWAP_CLUSTER_MAX number of 1860 * pages that were scanned. This will return to the 1861 * caller faster at the risk reclaim/compaction and 1862 * the resulting allocation attempt fails 1863 */ 1864 if (!nr_reclaimed) 1865 return false; 1866 } 1867 1868 /* 1869 * If we have not reclaimed enough pages for compaction and the 1870 * inactive lists are large enough, continue reclaiming 1871 */ 1872 pages_for_compaction = (2UL << sc->order); 1873 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 1874 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1875 if (sc->nr_reclaimed < pages_for_compaction && 1876 inactive_lru_pages > pages_for_compaction) 1877 return true; 1878 1879 /* If compaction would go ahead or the allocation would succeed, stop */ 1880 switch (compaction_suitable(zone, sc->order)) { 1881 case COMPACT_PARTIAL: 1882 case COMPACT_CONTINUE: 1883 return false; 1884 default: 1885 return true; 1886 } 1887} 1888 1889/* 1890 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1891 */ 1892static void shrink_zone(int priority, struct zone *zone, 1893 struct scan_control *sc) 1894{ 1895 unsigned long nr[NR_LRU_LISTS]; 1896 unsigned long nr_to_scan; 1897 enum lru_list l; 1898 unsigned long nr_reclaimed, nr_scanned; 1899 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1900 1901restart: 1902 nr_reclaimed = 0; 1903 nr_scanned = sc->nr_scanned; 1904 get_scan_count(zone, sc, nr, priority); 1905 1906 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1907 nr[LRU_INACTIVE_FILE]) { 1908 for_each_evictable_lru(l) { 1909 if (nr[l]) { 1910 nr_to_scan = min_t(unsigned long, 1911 nr[l], SWAP_CLUSTER_MAX); 1912 nr[l] -= nr_to_scan; 1913 1914 nr_reclaimed += shrink_list(l, nr_to_scan, 1915 zone, sc, priority); 1916 } 1917 } 1918 /* 1919 * On large memory systems, scan >> priority can become 1920 * really large. This is fine for the starting priority; 1921 * we want to put equal scanning pressure on each zone. 1922 * However, if the VM has a harder time of freeing pages, 1923 * with multiple processes reclaiming pages, the total 1924 * freeing target can get unreasonably large. 1925 */ 1926 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 1927 break; 1928 } 1929 sc->nr_reclaimed += nr_reclaimed; 1930 1931 /* 1932 * Even if we did not try to evict anon pages at all, we want to 1933 * rebalance the anon lru active/inactive ratio. 1934 */ 1935 if (inactive_anon_is_low(zone, sc)) 1936 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1937 1938 /* reclaim/compaction might need reclaim to continue */ 1939 if (should_continue_reclaim(zone, nr_reclaimed, 1940 sc->nr_scanned - nr_scanned, sc)) 1941 goto restart; 1942 1943 throttle_vm_writeout(sc->gfp_mask); 1944} 1945 1946/* 1947 * This is the direct reclaim path, for page-allocating processes. We only 1948 * try to reclaim pages from zones which will satisfy the caller's allocation 1949 * request. 1950 * 1951 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 1952 * Because: 1953 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1954 * allocation or 1955 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 1956 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 1957 * zone defense algorithm. 1958 * 1959 * If a zone is deemed to be full of pinned pages then just give it a light 1960 * scan then give up on it. 1961 */ 1962static void shrink_zones(int priority, struct zonelist *zonelist, 1963 struct scan_control *sc) 1964{ 1965 struct zoneref *z; 1966 struct zone *zone; 1967 1968 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1969 gfp_zone(sc->gfp_mask), sc->nodemask) { 1970 if (!populated_zone(zone)) 1971 continue; 1972 /* 1973 * Take care memory controller reclaiming has small influence 1974 * to global LRU. 1975 */ 1976 if (scanning_global_lru(sc)) { 1977 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1978 continue; 1979 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1980 continue; /* Let kswapd poll it */ 1981 } 1982 1983 shrink_zone(priority, zone, sc); 1984 } 1985} 1986 1987static bool zone_reclaimable(struct zone *zone) 1988{ 1989 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 1990} 1991 1992/* All zones in zonelist are unreclaimable? */ 1993static bool all_unreclaimable(struct zonelist *zonelist, 1994 struct scan_control *sc) 1995{ 1996 struct zoneref *z; 1997 struct zone *zone; 1998 1999 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2000 gfp_zone(sc->gfp_mask), sc->nodemask) { 2001 if (!populated_zone(zone)) 2002 continue; 2003 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2004 continue; 2005 if (!zone->all_unreclaimable) 2006 return false; 2007 } 2008 2009 return true; 2010} 2011 2012/* 2013 * This is the main entry point to direct page reclaim. 2014 * 2015 * If a full scan of the inactive list fails to free enough memory then we 2016 * are "out of memory" and something needs to be killed. 2017 * 2018 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2019 * high - the zone may be full of dirty or under-writeback pages, which this 2020 * caller can't do much about. We kick the writeback threads and take explicit 2021 * naps in the hope that some of these pages can be written. But if the 2022 * allocating task holds filesystem locks which prevent writeout this might not 2023 * work, and the allocation attempt will fail. 2024 * 2025 * returns: 0, if no pages reclaimed 2026 * else, the number of pages reclaimed 2027 */ 2028static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2029 struct scan_control *sc) 2030{ 2031 int priority; 2032 unsigned long total_scanned = 0; 2033 struct reclaim_state *reclaim_state = current->reclaim_state; 2034 struct zoneref *z; 2035 struct zone *zone; 2036 unsigned long writeback_threshold; 2037 2038 get_mems_allowed(); 2039 delayacct_freepages_start(); 2040 2041 if (scanning_global_lru(sc)) 2042 count_vm_event(ALLOCSTALL); 2043 2044 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2045 sc->nr_scanned = 0; 2046 if (!priority) 2047 disable_swap_token(); 2048 shrink_zones(priority, zonelist, sc); 2049 /* 2050 * Don't shrink slabs when reclaiming memory from 2051 * over limit cgroups 2052 */ 2053 if (scanning_global_lru(sc)) { 2054 unsigned long lru_pages = 0; 2055 for_each_zone_zonelist(zone, z, zonelist, 2056 gfp_zone(sc->gfp_mask)) { 2057 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2058 continue; 2059 2060 lru_pages += zone_reclaimable_pages(zone); 2061 } 2062 2063 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); 2064 if (reclaim_state) { 2065 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2066 reclaim_state->reclaimed_slab = 0; 2067 } 2068 } 2069 total_scanned += sc->nr_scanned; 2070 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2071 goto out; 2072 2073 /* 2074 * Try to write back as many pages as we just scanned. This 2075 * tends to cause slow streaming writers to write data to the 2076 * disk smoothly, at the dirtying rate, which is nice. But 2077 * that's undesirable in laptop mode, where we *want* lumpy 2078 * writeout. So in laptop mode, write out the whole world. 2079 */ 2080 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2081 if (total_scanned > writeback_threshold) { 2082 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2083 sc->may_writepage = 1; 2084 } 2085 2086 /* Take a nap, wait for some writeback to complete */ 2087 if (!sc->hibernation_mode && sc->nr_scanned && 2088 priority < DEF_PRIORITY - 2) { 2089 struct zone *preferred_zone; 2090 2091 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2092 &cpuset_current_mems_allowed, 2093 &preferred_zone); 2094 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2095 } 2096 } 2097 2098out: 2099 delayacct_freepages_end(); 2100 put_mems_allowed(); 2101 2102 if (sc->nr_reclaimed) 2103 return sc->nr_reclaimed; 2104 2105 /* 2106 * As hibernation is going on, kswapd is freezed so that it can't mark 2107 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2108 * check. 2109 */ 2110 if (oom_killer_disabled) 2111 return 0; 2112 2113 /* top priority shrink_zones still had more to do? don't OOM, then */ 2114 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2115 return 1; 2116 2117 return 0; 2118} 2119 2120unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2121 gfp_t gfp_mask, nodemask_t *nodemask) 2122{ 2123 unsigned long nr_reclaimed; 2124 struct scan_control sc = { 2125 .gfp_mask = gfp_mask, 2126 .may_writepage = !laptop_mode, 2127 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2128 .may_unmap = 1, 2129 .may_swap = 1, 2130 .swappiness = vm_swappiness, 2131 .order = order, 2132 .mem_cgroup = NULL, 2133 .nodemask = nodemask, 2134 }; 2135 2136 trace_mm_vmscan_direct_reclaim_begin(order, 2137 sc.may_writepage, 2138 gfp_mask); 2139 2140 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2141 2142 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2143 2144 return nr_reclaimed; 2145} 2146 2147#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2148 2149unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2150 gfp_t gfp_mask, bool noswap, 2151 unsigned int swappiness, 2152 struct zone *zone) 2153{ 2154 struct scan_control sc = { 2155 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2156 .may_writepage = !laptop_mode, 2157 .may_unmap = 1, 2158 .may_swap = !noswap, 2159 .swappiness = swappiness, 2160 .order = 0, 2161 .mem_cgroup = mem, 2162 }; 2163 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2164 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2165 2166 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2167 sc.may_writepage, 2168 sc.gfp_mask); 2169 2170 /* 2171 * NOTE: Although we can get the priority field, using it 2172 * here is not a good idea, since it limits the pages we can scan. 2173 * if we don't reclaim here, the shrink_zone from balance_pgdat 2174 * will pick up pages from other mem cgroup's as well. We hack 2175 * the priority and make it zero. 2176 */ 2177 shrink_zone(0, zone, &sc); 2178 2179 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2180 2181 return sc.nr_reclaimed; 2182} 2183 2184unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2185 gfp_t gfp_mask, 2186 bool noswap, 2187 unsigned int swappiness) 2188{ 2189 struct zonelist *zonelist; 2190 unsigned long nr_reclaimed; 2191 struct scan_control sc = { 2192 .may_writepage = !laptop_mode, 2193 .may_unmap = 1, 2194 .may_swap = !noswap, 2195 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2196 .swappiness = swappiness, 2197 .order = 0, 2198 .mem_cgroup = mem_cont, 2199 .nodemask = NULL, /* we don't care the placement */ 2200 }; 2201 2202 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2203 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2204 zonelist = NODE_DATA(numa_node_id())->node_zonelists; 2205 2206 trace_mm_vmscan_memcg_reclaim_begin(0, 2207 sc.may_writepage, 2208 sc.gfp_mask); 2209 2210 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2211 2212 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2213 2214 return nr_reclaimed; 2215} 2216#endif 2217 2218/* 2219 * pgdat_balanced is used when checking if a node is balanced for high-order 2220 * allocations. Only zones that meet watermarks and are in a zone allowed 2221 * by the callers classzone_idx are added to balanced_pages. The total of 2222 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2223 * for the node to be considered balanced. Forcing all zones to be balanced 2224 * for high orders can cause excessive reclaim when there are imbalanced zones. 2225 * The choice of 25% is due to 2226 * o a 16M DMA zone that is balanced will not balance a zone on any 2227 * reasonable sized machine 2228 * o On all other machines, the top zone must be at least a reasonable 2229 * percentage of the middle zones. For example, on 32-bit x86, highmem 2230 * would need to be at least 256M for it to be balance a whole node. 2231 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2232 * to balance a node on its own. These seemed like reasonable ratios. 2233 */ 2234static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2235 int classzone_idx) 2236{ 2237 unsigned long present_pages = 0; 2238 int i; 2239 2240 for (i = 0; i <= classzone_idx; i++) 2241 present_pages += pgdat->node_zones[i].present_pages; 2242 2243 return balanced_pages > (present_pages >> 2); 2244} 2245 2246/* is kswapd sleeping prematurely? */ 2247static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2248 int classzone_idx) 2249{ 2250 int i; 2251 unsigned long balanced = 0; 2252 bool all_zones_ok = true; 2253 2254 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2255 if (remaining) 2256 return true; 2257 2258 /* Check the watermark levels */ 2259 for (i = 0; i < pgdat->nr_zones; i++) { 2260 struct zone *zone = pgdat->node_zones + i; 2261 2262 if (!populated_zone(zone)) 2263 continue; 2264 2265 /* 2266 * balance_pgdat() skips over all_unreclaimable after 2267 * DEF_PRIORITY. Effectively, it considers them balanced so 2268 * they must be considered balanced here as well if kswapd 2269 * is to sleep 2270 */ 2271 if (zone->all_unreclaimable) { 2272 balanced += zone->present_pages; 2273 continue; 2274 } 2275 2276 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2277 classzone_idx, 0)) 2278 all_zones_ok = false; 2279 else 2280 balanced += zone->present_pages; 2281 } 2282 2283 /* 2284 * For high-order requests, the balanced zones must contain at least 2285 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2286 * must be balanced 2287 */ 2288 if (order) 2289 return pgdat_balanced(pgdat, balanced, classzone_idx); 2290 else 2291 return !all_zones_ok; 2292} 2293 2294/* 2295 * For kswapd, balance_pgdat() will work across all this node's zones until 2296 * they are all at high_wmark_pages(zone). 2297 * 2298 * Returns the final order kswapd was reclaiming at 2299 * 2300 * There is special handling here for zones which are full of pinned pages. 2301 * This can happen if the pages are all mlocked, or if they are all used by 2302 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2303 * What we do is to detect the case where all pages in the zone have been 2304 * scanned twice and there has been zero successful reclaim. Mark the zone as 2305 * dead and from now on, only perform a short scan. Basically we're polling 2306 * the zone for when the problem goes away. 2307 * 2308 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2309 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2310 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2311 * lower zones regardless of the number of free pages in the lower zones. This 2312 * interoperates with the page allocator fallback scheme to ensure that aging 2313 * of pages is balanced across the zones. 2314 */ 2315static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2316 int *classzone_idx) 2317{ 2318 int all_zones_ok; 2319 unsigned long balanced; 2320 int priority; 2321 int i; 2322 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2323 unsigned long total_scanned; 2324 struct reclaim_state *reclaim_state = current->reclaim_state; 2325 struct scan_control sc = { 2326 .gfp_mask = GFP_KERNEL, 2327 .may_unmap = 1, 2328 .may_swap = 1, 2329 /* 2330 * kswapd doesn't want to be bailed out while reclaim. because 2331 * we want to put equal scanning pressure on each zone. 2332 */ 2333 .nr_to_reclaim = ULONG_MAX, 2334 .swappiness = vm_swappiness, 2335 .order = order, 2336 .mem_cgroup = NULL, 2337 }; 2338loop_again: 2339 total_scanned = 0; 2340 sc.nr_reclaimed = 0; 2341 sc.may_writepage = !laptop_mode; 2342 count_vm_event(PAGEOUTRUN); 2343 2344 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2345 unsigned long lru_pages = 0; 2346 int has_under_min_watermark_zone = 0; 2347 2348 /* The swap token gets in the way of swapout... */ 2349 if (!priority) 2350 disable_swap_token(); 2351 2352 all_zones_ok = 1; 2353 balanced = 0; 2354 2355 /* 2356 * Scan in the highmem->dma direction for the highest 2357 * zone which needs scanning 2358 */ 2359 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2360 struct zone *zone = pgdat->node_zones + i; 2361 2362 if (!populated_zone(zone)) 2363 continue; 2364 2365 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2366 continue; 2367 2368 /* 2369 * Do some background aging of the anon list, to give 2370 * pages a chance to be referenced before reclaiming. 2371 */ 2372 if (inactive_anon_is_low(zone, &sc)) 2373 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2374 &sc, priority, 0); 2375 2376 if (!zone_watermark_ok_safe(zone, order, 2377 high_wmark_pages(zone), 0, 0)) { 2378 end_zone = i; 2379 *classzone_idx = i; 2380 break; 2381 } 2382 } 2383 if (i < 0) 2384 goto out; 2385 2386 for (i = 0; i <= end_zone; i++) { 2387 struct zone *zone = pgdat->node_zones + i; 2388 2389 lru_pages += zone_reclaimable_pages(zone); 2390 } 2391 2392 /* 2393 * Now scan the zone in the dma->highmem direction, stopping 2394 * at the last zone which needs scanning. 2395 * 2396 * We do this because the page allocator works in the opposite 2397 * direction. This prevents the page allocator from allocating 2398 * pages behind kswapd's direction of progress, which would 2399 * cause too much scanning of the lower zones. 2400 */ 2401 for (i = 0; i <= end_zone; i++) { 2402 struct zone *zone = pgdat->node_zones + i; 2403 int nr_slab; 2404 unsigned long balance_gap; 2405 2406 if (!populated_zone(zone)) 2407 continue; 2408 2409 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2410 continue; 2411 2412 sc.nr_scanned = 0; 2413 2414 /* 2415 * Call soft limit reclaim before calling shrink_zone. 2416 * For now we ignore the return value 2417 */ 2418 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); 2419 2420 /* 2421 * We put equal pressure on every zone, unless 2422 * one zone has way too many pages free 2423 * already. The "too many pages" is defined 2424 * as the high wmark plus a "gap" where the 2425 * gap is either the low watermark or 1% 2426 * of the zone, whichever is smaller. 2427 */ 2428 balance_gap = min(low_wmark_pages(zone), 2429 (zone->present_pages + 2430 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2431 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2432 if (!zone_watermark_ok_safe(zone, order, 2433 high_wmark_pages(zone) + balance_gap, 2434 end_zone, 0)) 2435 shrink_zone(priority, zone, &sc); 2436 reclaim_state->reclaimed_slab = 0; 2437 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 2438 lru_pages); 2439 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2440 total_scanned += sc.nr_scanned; 2441 2442 if (zone->all_unreclaimable) 2443 continue; 2444 if (nr_slab == 0 && 2445 !zone_reclaimable(zone)) 2446 zone->all_unreclaimable = 1; 2447 /* 2448 * If we've done a decent amount of scanning and 2449 * the reclaim ratio is low, start doing writepage 2450 * even in laptop mode 2451 */ 2452 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2453 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2454 sc.may_writepage = 1; 2455 2456 if (!zone_watermark_ok_safe(zone, order, 2457 high_wmark_pages(zone), end_zone, 0)) { 2458 all_zones_ok = 0; 2459 /* 2460 * We are still under min water mark. This 2461 * means that we have a GFP_ATOMIC allocation 2462 * failure risk. Hurry up! 2463 */ 2464 if (!zone_watermark_ok_safe(zone, order, 2465 min_wmark_pages(zone), end_zone, 0)) 2466 has_under_min_watermark_zone = 1; 2467 } else { 2468 /* 2469 * If a zone reaches its high watermark, 2470 * consider it to be no longer congested. It's 2471 * possible there are dirty pages backed by 2472 * congested BDIs but as pressure is relieved, 2473 * spectulatively avoid congestion waits 2474 */ 2475 zone_clear_flag(zone, ZONE_CONGESTED); 2476 if (i <= *classzone_idx) 2477 balanced += zone->present_pages; 2478 } 2479 2480 } 2481 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2482 break; /* kswapd: all done */ 2483 /* 2484 * OK, kswapd is getting into trouble. Take a nap, then take 2485 * another pass across the zones. 2486 */ 2487 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2488 if (has_under_min_watermark_zone) 2489 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2490 else 2491 congestion_wait(BLK_RW_ASYNC, HZ/10); 2492 } 2493 2494 /* 2495 * We do this so kswapd doesn't build up large priorities for 2496 * example when it is freeing in parallel with allocators. It 2497 * matches the direct reclaim path behaviour in terms of impact 2498 * on zone->*_priority. 2499 */ 2500 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2501 break; 2502 } 2503out: 2504 2505 /* 2506 * order-0: All zones must meet high watermark for a balanced node 2507 * high-order: Balanced zones must make up at least 25% of the node 2508 * for the node to be balanced 2509 */ 2510 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2511 cond_resched(); 2512 2513 try_to_freeze(); 2514 2515 /* 2516 * Fragmentation may mean that the system cannot be 2517 * rebalanced for high-order allocations in all zones. 2518 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2519 * it means the zones have been fully scanned and are still 2520 * not balanced. For high-order allocations, there is 2521 * little point trying all over again as kswapd may 2522 * infinite loop. 2523 * 2524 * Instead, recheck all watermarks at order-0 as they 2525 * are the most important. If watermarks are ok, kswapd will go 2526 * back to sleep. High-order users can still perform direct 2527 * reclaim if they wish. 2528 */ 2529 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2530 order = sc.order = 0; 2531 2532 goto loop_again; 2533 } 2534 2535 /* 2536 * If kswapd was reclaiming at a higher order, it has the option of 2537 * sleeping without all zones being balanced. Before it does, it must 2538 * ensure that the watermarks for order-0 on *all* zones are met and 2539 * that the congestion flags are cleared. The congestion flag must 2540 * be cleared as kswapd is the only mechanism that clears the flag 2541 * and it is potentially going to sleep here. 2542 */ 2543 if (order) { 2544 for (i = 0; i <= end_zone; i++) { 2545 struct zone *zone = pgdat->node_zones + i; 2546 2547 if (!populated_zone(zone)) 2548 continue; 2549 2550 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2551 continue; 2552 2553 /* Confirm the zone is balanced for order-0 */ 2554 if (!zone_watermark_ok(zone, 0, 2555 high_wmark_pages(zone), 0, 0)) { 2556 order = sc.order = 0; 2557 goto loop_again; 2558 } 2559 2560 /* If balanced, clear the congested flag */ 2561 zone_clear_flag(zone, ZONE_CONGESTED); 2562 } 2563 } 2564 2565 /* 2566 * Return the order we were reclaiming at so sleeping_prematurely() 2567 * makes a decision on the order we were last reclaiming at. However, 2568 * if another caller entered the allocator slow path while kswapd 2569 * was awake, order will remain at the higher level 2570 */ 2571 *classzone_idx = end_zone; 2572 return order; 2573} 2574 2575static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2576{ 2577 long remaining = 0; 2578 DEFINE_WAIT(wait); 2579 2580 if (freezing(current) || kthread_should_stop()) 2581 return; 2582 2583 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2584 2585 /* Try to sleep for a short interval */ 2586 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2587 remaining = schedule_timeout(HZ/10); 2588 finish_wait(&pgdat->kswapd_wait, &wait); 2589 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2590 } 2591 2592 /* 2593 * After a short sleep, check if it was a premature sleep. If not, then 2594 * go fully to sleep until explicitly woken up. 2595 */ 2596 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2597 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2598 2599 /* 2600 * vmstat counters are not perfectly accurate and the estimated 2601 * value for counters such as NR_FREE_PAGES can deviate from the 2602 * true value by nr_online_cpus * threshold. To avoid the zone 2603 * watermarks being breached while under pressure, we reduce the 2604 * per-cpu vmstat threshold while kswapd is awake and restore 2605 * them before going back to sleep. 2606 */ 2607 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2608 schedule(); 2609 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2610 } else { 2611 if (remaining) 2612 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2613 else 2614 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2615 } 2616 finish_wait(&pgdat->kswapd_wait, &wait); 2617} 2618 2619/* 2620 * The background pageout daemon, started as a kernel thread 2621 * from the init process. 2622 * 2623 * This basically trickles out pages so that we have _some_ 2624 * free memory available even if there is no other activity 2625 * that frees anything up. This is needed for things like routing 2626 * etc, where we otherwise might have all activity going on in 2627 * asynchronous contexts that cannot page things out. 2628 * 2629 * If there are applications that are active memory-allocators 2630 * (most normal use), this basically shouldn't matter. 2631 */ 2632static int kswapd(void *p) 2633{ 2634 unsigned long order; 2635 int classzone_idx; 2636 pg_data_t *pgdat = (pg_data_t*)p; 2637 struct task_struct *tsk = current; 2638 2639 struct reclaim_state reclaim_state = { 2640 .reclaimed_slab = 0, 2641 }; 2642 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2643 2644 lockdep_set_current_reclaim_state(GFP_KERNEL); 2645 2646 if (!cpumask_empty(cpumask)) 2647 set_cpus_allowed_ptr(tsk, cpumask); 2648 current->reclaim_state = &reclaim_state; 2649 2650 /* 2651 * Tell the memory management that we're a "memory allocator", 2652 * and that if we need more memory we should get access to it 2653 * regardless (see "__alloc_pages()"). "kswapd" should 2654 * never get caught in the normal page freeing logic. 2655 * 2656 * (Kswapd normally doesn't need memory anyway, but sometimes 2657 * you need a small amount of memory in order to be able to 2658 * page out something else, and this flag essentially protects 2659 * us from recursively trying to free more memory as we're 2660 * trying to free the first piece of memory in the first place). 2661 */ 2662 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2663 set_freezable(); 2664 2665 order = 0; 2666 classzone_idx = MAX_NR_ZONES - 1; 2667 for ( ; ; ) { 2668 unsigned long new_order; 2669 int new_classzone_idx; 2670 int ret; 2671 2672 new_order = pgdat->kswapd_max_order; 2673 new_classzone_idx = pgdat->classzone_idx; 2674 pgdat->kswapd_max_order = 0; 2675 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2676 if (order < new_order || classzone_idx > new_classzone_idx) { 2677 /* 2678 * Don't sleep if someone wants a larger 'order' 2679 * allocation or has tigher zone constraints 2680 */ 2681 order = new_order; 2682 classzone_idx = new_classzone_idx; 2683 } else { 2684 kswapd_try_to_sleep(pgdat, order, classzone_idx); 2685 order = pgdat->kswapd_max_order; 2686 classzone_idx = pgdat->classzone_idx; 2687 pgdat->kswapd_max_order = 0; 2688 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2689 } 2690 2691 ret = try_to_freeze(); 2692 if (kthread_should_stop()) 2693 break; 2694 2695 /* 2696 * We can speed up thawing tasks if we don't call balance_pgdat 2697 * after returning from the refrigerator 2698 */ 2699 if (!ret) { 2700 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2701 order = balance_pgdat(pgdat, order, &classzone_idx); 2702 } 2703 } 2704 return 0; 2705} 2706 2707/* 2708 * A zone is low on free memory, so wake its kswapd task to service it. 2709 */ 2710void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2711{ 2712 pg_data_t *pgdat; 2713 2714 if (!populated_zone(zone)) 2715 return; 2716 2717 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2718 return; 2719 pgdat = zone->zone_pgdat; 2720 if (pgdat->kswapd_max_order < order) { 2721 pgdat->kswapd_max_order = order; 2722 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2723 } 2724 if (!waitqueue_active(&pgdat->kswapd_wait)) 2725 return; 2726 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2727 return; 2728 2729 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2730 wake_up_interruptible(&pgdat->kswapd_wait); 2731} 2732 2733/* 2734 * The reclaimable count would be mostly accurate. 2735 * The less reclaimable pages may be 2736 * - mlocked pages, which will be moved to unevictable list when encountered 2737 * - mapped pages, which may require several travels to be reclaimed 2738 * - dirty pages, which is not "instantly" reclaimable 2739 */ 2740unsigned long global_reclaimable_pages(void) 2741{ 2742 int nr; 2743 2744 nr = global_page_state(NR_ACTIVE_FILE) + 2745 global_page_state(NR_INACTIVE_FILE); 2746 2747 if (nr_swap_pages > 0) 2748 nr += global_page_state(NR_ACTIVE_ANON) + 2749 global_page_state(NR_INACTIVE_ANON); 2750 2751 return nr; 2752} 2753 2754unsigned long zone_reclaimable_pages(struct zone *zone) 2755{ 2756 int nr; 2757 2758 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2759 zone_page_state(zone, NR_INACTIVE_FILE); 2760 2761 if (nr_swap_pages > 0) 2762 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2763 zone_page_state(zone, NR_INACTIVE_ANON); 2764 2765 return nr; 2766} 2767 2768#ifdef CONFIG_HIBERNATION 2769/* 2770 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2771 * freed pages. 2772 * 2773 * Rather than trying to age LRUs the aim is to preserve the overall 2774 * LRU order by reclaiming preferentially 2775 * inactive > active > active referenced > active mapped 2776 */ 2777unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2778{ 2779 struct reclaim_state reclaim_state; 2780 struct scan_control sc = { 2781 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2782 .may_swap = 1, 2783 .may_unmap = 1, 2784 .may_writepage = 1, 2785 .nr_to_reclaim = nr_to_reclaim, 2786 .hibernation_mode = 1, 2787 .swappiness = vm_swappiness, 2788 .order = 0, 2789 }; 2790 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2791 struct task_struct *p = current; 2792 unsigned long nr_reclaimed; 2793 2794 p->flags |= PF_MEMALLOC; 2795 lockdep_set_current_reclaim_state(sc.gfp_mask); 2796 reclaim_state.reclaimed_slab = 0; 2797 p->reclaim_state = &reclaim_state; 2798 2799 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2800 2801 p->reclaim_state = NULL; 2802 lockdep_clear_current_reclaim_state(); 2803 p->flags &= ~PF_MEMALLOC; 2804 2805 return nr_reclaimed; 2806} 2807#endif /* CONFIG_HIBERNATION */ 2808 2809/* It's optimal to keep kswapds on the same CPUs as their memory, but 2810 not required for correctness. So if the last cpu in a node goes 2811 away, we get changed to run anywhere: as the first one comes back, 2812 restore their cpu bindings. */ 2813static int __devinit cpu_callback(struct notifier_block *nfb, 2814 unsigned long action, void *hcpu) 2815{ 2816 int nid; 2817 2818 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2819 for_each_node_state(nid, N_HIGH_MEMORY) { 2820 pg_data_t *pgdat = NODE_DATA(nid); 2821 const struct cpumask *mask; 2822 2823 mask = cpumask_of_node(pgdat->node_id); 2824 2825 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2826 /* One of our CPUs online: restore mask */ 2827 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2828 } 2829 } 2830 return NOTIFY_OK; 2831} 2832 2833/* 2834 * This kswapd start function will be called by init and node-hot-add. 2835 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2836 */ 2837int kswapd_run(int nid) 2838{ 2839 pg_data_t *pgdat = NODE_DATA(nid); 2840 int ret = 0; 2841 2842 if (pgdat->kswapd) 2843 return 0; 2844 2845 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2846 if (IS_ERR(pgdat->kswapd)) { 2847 /* failure at boot is fatal */ 2848 BUG_ON(system_state == SYSTEM_BOOTING); 2849 printk("Failed to start kswapd on node %d\n",nid); 2850 ret = -1; 2851 } 2852 return ret; 2853} 2854 2855/* 2856 * Called by memory hotplug when all memory in a node is offlined. 2857 */ 2858void kswapd_stop(int nid) 2859{ 2860 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2861 2862 if (kswapd) 2863 kthread_stop(kswapd); 2864} 2865 2866static int __init kswapd_init(void) 2867{ 2868 int nid; 2869 2870 swap_setup(); 2871 for_each_node_state(nid, N_HIGH_MEMORY) 2872 kswapd_run(nid); 2873 hotcpu_notifier(cpu_callback, 0); 2874 return 0; 2875} 2876 2877module_init(kswapd_init) 2878 2879#ifdef CONFIG_NUMA 2880/* 2881 * Zone reclaim mode 2882 * 2883 * If non-zero call zone_reclaim when the number of free pages falls below 2884 * the watermarks. 2885 */ 2886int zone_reclaim_mode __read_mostly; 2887 2888#define RECLAIM_OFF 0 2889#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2890#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2891#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2892 2893/* 2894 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2895 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2896 * a zone. 2897 */ 2898#define ZONE_RECLAIM_PRIORITY 4 2899 2900/* 2901 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2902 * occur. 2903 */ 2904int sysctl_min_unmapped_ratio = 1; 2905 2906/* 2907 * If the number of slab pages in a zone grows beyond this percentage then 2908 * slab reclaim needs to occur. 2909 */ 2910int sysctl_min_slab_ratio = 5; 2911 2912static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 2913{ 2914 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 2915 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 2916 zone_page_state(zone, NR_ACTIVE_FILE); 2917 2918 /* 2919 * It's possible for there to be more file mapped pages than 2920 * accounted for by the pages on the file LRU lists because 2921 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 2922 */ 2923 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 2924} 2925 2926/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 2927static long zone_pagecache_reclaimable(struct zone *zone) 2928{ 2929 long nr_pagecache_reclaimable; 2930 long delta = 0; 2931 2932 /* 2933 * If RECLAIM_SWAP is set, then all file pages are considered 2934 * potentially reclaimable. Otherwise, we have to worry about 2935 * pages like swapcache and zone_unmapped_file_pages() provides 2936 * a better estimate 2937 */ 2938 if (zone_reclaim_mode & RECLAIM_SWAP) 2939 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 2940 else 2941 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 2942 2943 /* If we can't clean pages, remove dirty pages from consideration */ 2944 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 2945 delta += zone_page_state(zone, NR_FILE_DIRTY); 2946 2947 /* Watch for any possible underflows due to delta */ 2948 if (unlikely(delta > nr_pagecache_reclaimable)) 2949 delta = nr_pagecache_reclaimable; 2950 2951 return nr_pagecache_reclaimable - delta; 2952} 2953 2954/* 2955 * Try to free up some pages from this zone through reclaim. 2956 */ 2957static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2958{ 2959 /* Minimum pages needed in order to stay on node */ 2960 const unsigned long nr_pages = 1 << order; 2961 struct task_struct *p = current; 2962 struct reclaim_state reclaim_state; 2963 int priority; 2964 struct scan_control sc = { 2965 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 2966 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 2967 .may_swap = 1, 2968 .nr_to_reclaim = max_t(unsigned long, nr_pages, 2969 SWAP_CLUSTER_MAX), 2970 .gfp_mask = gfp_mask, 2971 .swappiness = vm_swappiness, 2972 .order = order, 2973 }; 2974 unsigned long nr_slab_pages0, nr_slab_pages1; 2975 2976 cond_resched(); 2977 /* 2978 * We need to be able to allocate from the reserves for RECLAIM_SWAP 2979 * and we also need to be able to write out pages for RECLAIM_WRITE 2980 * and RECLAIM_SWAP. 2981 */ 2982 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 2983 lockdep_set_current_reclaim_state(gfp_mask); 2984 reclaim_state.reclaimed_slab = 0; 2985 p->reclaim_state = &reclaim_state; 2986 2987 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 2988 /* 2989 * Free memory by calling shrink zone with increasing 2990 * priorities until we have enough memory freed. 2991 */ 2992 priority = ZONE_RECLAIM_PRIORITY; 2993 do { 2994 shrink_zone(priority, zone, &sc); 2995 priority--; 2996 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 2997 } 2998 2999 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3000 if (nr_slab_pages0 > zone->min_slab_pages) { 3001 /* 3002 * shrink_slab() does not currently allow us to determine how 3003 * many pages were freed in this zone. So we take the current 3004 * number of slab pages and shake the slab until it is reduced 3005 * by the same nr_pages that we used for reclaiming unmapped 3006 * pages. 3007 * 3008 * Note that shrink_slab will free memory on all zones and may 3009 * take a long time. 3010 */ 3011 for (;;) { 3012 unsigned long lru_pages = zone_reclaimable_pages(zone); 3013 3014 /* No reclaimable slab or very low memory pressure */ 3015 if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) 3016 break; 3017 3018 /* Freed enough memory */ 3019 nr_slab_pages1 = zone_page_state(zone, 3020 NR_SLAB_RECLAIMABLE); 3021 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3022 break; 3023 } 3024 3025 /* 3026 * Update nr_reclaimed by the number of slab pages we 3027 * reclaimed from this zone. 3028 */ 3029 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3030 if (nr_slab_pages1 < nr_slab_pages0) 3031 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3032 } 3033 3034 p->reclaim_state = NULL; 3035 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3036 lockdep_clear_current_reclaim_state(); 3037 return sc.nr_reclaimed >= nr_pages; 3038} 3039 3040int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3041{ 3042 int node_id; 3043 int ret; 3044 3045 /* 3046 * Zone reclaim reclaims unmapped file backed pages and 3047 * slab pages if we are over the defined limits. 3048 * 3049 * A small portion of unmapped file backed pages is needed for 3050 * file I/O otherwise pages read by file I/O will be immediately 3051 * thrown out if the zone is overallocated. So we do not reclaim 3052 * if less than a specified percentage of the zone is used by 3053 * unmapped file backed pages. 3054 */ 3055 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3056 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3057 return ZONE_RECLAIM_FULL; 3058 3059 if (zone->all_unreclaimable) 3060 return ZONE_RECLAIM_FULL; 3061 3062 /* 3063 * Do not scan if the allocation should not be delayed. 3064 */ 3065 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3066 return ZONE_RECLAIM_NOSCAN; 3067 3068 /* 3069 * Only run zone reclaim on the local zone or on zones that do not 3070 * have associated processors. This will favor the local processor 3071 * over remote processors and spread off node memory allocations 3072 * as wide as possible. 3073 */ 3074 node_id = zone_to_nid(zone); 3075 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3076 return ZONE_RECLAIM_NOSCAN; 3077 3078 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3079 return ZONE_RECLAIM_NOSCAN; 3080 3081 ret = __zone_reclaim(zone, gfp_mask, order); 3082 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3083 3084 if (!ret) 3085 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3086 3087 return ret; 3088} 3089#endif 3090 3091/* 3092 * page_evictable - test whether a page is evictable 3093 * @page: the page to test 3094 * @vma: the VMA in which the page is or will be mapped, may be NULL 3095 * 3096 * Test whether page is evictable--i.e., should be placed on active/inactive 3097 * lists vs unevictable list. The vma argument is !NULL when called from the 3098 * fault path to determine how to instantate a new page. 3099 * 3100 * Reasons page might not be evictable: 3101 * (1) page's mapping marked unevictable 3102 * (2) page is part of an mlocked VMA 3103 * 3104 */ 3105int page_evictable(struct page *page, struct vm_area_struct *vma) 3106{ 3107 3108 if (mapping_unevictable(page_mapping(page))) 3109 return 0; 3110 3111 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3112 return 0; 3113 3114 return 1; 3115} 3116 3117/** 3118 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3119 * @page: page to check evictability and move to appropriate lru list 3120 * @zone: zone page is in 3121 * 3122 * Checks a page for evictability and moves the page to the appropriate 3123 * zone lru list. 3124 * 3125 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3126 * have PageUnevictable set. 3127 */ 3128static void check_move_unevictable_page(struct page *page, struct zone *zone) 3129{ 3130 VM_BUG_ON(PageActive(page)); 3131 3132retry: 3133 ClearPageUnevictable(page); 3134 if (page_evictable(page, NULL)) { 3135 enum lru_list l = page_lru_base_type(page); 3136 3137 __dec_zone_state(zone, NR_UNEVICTABLE); 3138 list_move(&page->lru, &zone->lru[l].list); 3139 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3140 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3141 __count_vm_event(UNEVICTABLE_PGRESCUED); 3142 } else { 3143 /* 3144 * rotate unevictable list 3145 */ 3146 SetPageUnevictable(page); 3147 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3148 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3149 if (page_evictable(page, NULL)) 3150 goto retry; 3151 } 3152} 3153 3154/** 3155 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3156 * @mapping: struct address_space to scan for evictable pages 3157 * 3158 * Scan all pages in mapping. Check unevictable pages for 3159 * evictability and move them to the appropriate zone lru list. 3160 */ 3161void scan_mapping_unevictable_pages(struct address_space *mapping) 3162{ 3163 pgoff_t next = 0; 3164 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3165 PAGE_CACHE_SHIFT; 3166 struct zone *zone; 3167 struct pagevec pvec; 3168 3169 if (mapping->nrpages == 0) 3170 return; 3171 3172 pagevec_init(&pvec, 0); 3173 while (next < end && 3174 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3175 int i; 3176 int pg_scanned = 0; 3177 3178 zone = NULL; 3179 3180 for (i = 0; i < pagevec_count(&pvec); i++) { 3181 struct page *page = pvec.pages[i]; 3182 pgoff_t page_index = page->index; 3183 struct zone *pagezone = page_zone(page); 3184 3185 pg_scanned++; 3186 if (page_index > next) 3187 next = page_index; 3188 next++; 3189 3190 if (pagezone != zone) { 3191 if (zone) 3192 spin_unlock_irq(&zone->lru_lock); 3193 zone = pagezone; 3194 spin_lock_irq(&zone->lru_lock); 3195 } 3196 3197 if (PageLRU(page) && PageUnevictable(page)) 3198 check_move_unevictable_page(page, zone); 3199 } 3200 if (zone) 3201 spin_unlock_irq(&zone->lru_lock); 3202 pagevec_release(&pvec); 3203 3204 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3205 } 3206 3207} 3208 3209/** 3210 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3211 * @zone - zone of which to scan the unevictable list 3212 * 3213 * Scan @zone's unevictable LRU lists to check for pages that have become 3214 * evictable. Move those that have to @zone's inactive list where they 3215 * become candidates for reclaim, unless shrink_inactive_zone() decides 3216 * to reactivate them. Pages that are still unevictable are rotated 3217 * back onto @zone's unevictable list. 3218 */ 3219#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3220static void scan_zone_unevictable_pages(struct zone *zone) 3221{ 3222 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3223 unsigned long scan; 3224 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3225 3226 while (nr_to_scan > 0) { 3227 unsigned long batch_size = min(nr_to_scan, 3228 SCAN_UNEVICTABLE_BATCH_SIZE); 3229 3230 spin_lock_irq(&zone->lru_lock); 3231 for (scan = 0; scan < batch_size; scan++) { 3232 struct page *page = lru_to_page(l_unevictable); 3233 3234 if (!trylock_page(page)) 3235 continue; 3236 3237 prefetchw_prev_lru_page(page, l_unevictable, flags); 3238 3239 if (likely(PageLRU(page) && PageUnevictable(page))) 3240 check_move_unevictable_page(page, zone); 3241 3242 unlock_page(page); 3243 } 3244 spin_unlock_irq(&zone->lru_lock); 3245 3246 nr_to_scan -= batch_size; 3247 } 3248} 3249 3250 3251/** 3252 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3253 * 3254 * A really big hammer: scan all zones' unevictable LRU lists to check for 3255 * pages that have become evictable. Move those back to the zones' 3256 * inactive list where they become candidates for reclaim. 3257 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3258 * and we add swap to the system. As such, it runs in the context of a task 3259 * that has possibly/probably made some previously unevictable pages 3260 * evictable. 3261 */ 3262static void scan_all_zones_unevictable_pages(void) 3263{ 3264 struct zone *zone; 3265 3266 for_each_zone(zone) { 3267 scan_zone_unevictable_pages(zone); 3268 } 3269} 3270 3271/* 3272 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3273 * all nodes' unevictable lists for evictable pages 3274 */ 3275unsigned long scan_unevictable_pages; 3276 3277int scan_unevictable_handler(struct ctl_table *table, int write, 3278 void __user *buffer, 3279 size_t *length, loff_t *ppos) 3280{ 3281 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3282 3283 if (write && *(unsigned long *)table->data) 3284 scan_all_zones_unevictable_pages(); 3285 3286 scan_unevictable_pages = 0; 3287 return 0; 3288} 3289 3290#ifdef CONFIG_NUMA 3291/* 3292 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3293 * a specified node's per zone unevictable lists for evictable pages. 3294 */ 3295 3296static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3297 struct sysdev_attribute *attr, 3298 char *buf) 3299{ 3300 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3301} 3302 3303static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3304 struct sysdev_attribute *attr, 3305 const char *buf, size_t count) 3306{ 3307 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3308 struct zone *zone; 3309 unsigned long res; 3310 unsigned long req = strict_strtoul(buf, 10, &res); 3311 3312 if (!req) 3313 return 1; /* zero is no-op */ 3314 3315 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3316 if (!populated_zone(zone)) 3317 continue; 3318 scan_zone_unevictable_pages(zone); 3319 } 3320 return 1; 3321} 3322 3323 3324static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3325 read_scan_unevictable_node, 3326 write_scan_unevictable_node); 3327 3328int scan_unevictable_register_node(struct node *node) 3329{ 3330 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3331} 3332 3333void scan_unevictable_unregister_node(struct node *node) 3334{ 3335 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3336} 3337#endif 3338