vmscan.c revision 0abdee2bd4118366c62349a304f81537be69af33
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 45#include <asm/tlbflush.h> 46#include <asm/div64.h> 47 48#include <linux/swapops.h> 49 50#include "internal.h" 51 52#define CREATE_TRACE_POINTS 53#include <trace/events/vmscan.h> 54 55/* 56 * reclaim_mode determines how the inactive list is shrunk 57 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages 58 * RECLAIM_MODE_ASYNC: Do not block 59 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback 60 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference 61 * page from the LRU and reclaim all pages within a 62 * naturally aligned range 63 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of 64 * order-0 pages and then compact the zone 65 */ 66typedef unsigned __bitwise__ reclaim_mode_t; 67#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) 68#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) 69#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) 70#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) 71#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) 72 73struct scan_control { 74 /* Incremented by the number of inactive pages that were scanned */ 75 unsigned long nr_scanned; 76 77 /* Number of pages freed so far during a call to shrink_zones() */ 78 unsigned long nr_reclaimed; 79 80 /* How many pages shrink_list() should reclaim */ 81 unsigned long nr_to_reclaim; 82 83 unsigned long hibernation_mode; 84 85 /* This context's GFP mask */ 86 gfp_t gfp_mask; 87 88 int may_writepage; 89 90 /* Can mapped pages be reclaimed? */ 91 int may_unmap; 92 93 /* Can pages be swapped as part of reclaim? */ 94 int may_swap; 95 96 int swappiness; 97 98 int order; 99 100 /* 101 * Intend to reclaim enough continuous memory rather than reclaim 102 * enough amount of memory. i.e, mode for high order allocation. 103 */ 104 reclaim_mode_t reclaim_mode; 105 106 /* Which cgroup do we reclaim from */ 107 struct mem_cgroup *mem_cgroup; 108 109 /* 110 * Nodemask of nodes allowed by the caller. If NULL, all nodes 111 * are scanned. 112 */ 113 nodemask_t *nodemask; 114}; 115 116#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 117 118#ifdef ARCH_HAS_PREFETCH 119#define prefetch_prev_lru_page(_page, _base, _field) \ 120 do { \ 121 if ((_page)->lru.prev != _base) { \ 122 struct page *prev; \ 123 \ 124 prev = lru_to_page(&(_page->lru)); \ 125 prefetch(&prev->_field); \ 126 } \ 127 } while (0) 128#else 129#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 130#endif 131 132#ifdef ARCH_HAS_PREFETCHW 133#define prefetchw_prev_lru_page(_page, _base, _field) \ 134 do { \ 135 if ((_page)->lru.prev != _base) { \ 136 struct page *prev; \ 137 \ 138 prev = lru_to_page(&(_page->lru)); \ 139 prefetchw(&prev->_field); \ 140 } \ 141 } while (0) 142#else 143#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 144#endif 145 146/* 147 * From 0 .. 100. Higher means more swappy. 148 */ 149int vm_swappiness = 60; 150long vm_total_pages; /* The total number of pages which the VM controls */ 151 152static LIST_HEAD(shrinker_list); 153static DECLARE_RWSEM(shrinker_rwsem); 154 155#ifdef CONFIG_CGROUP_MEM_RES_CTLR 156#define scanning_global_lru(sc) (!(sc)->mem_cgroup) 157#else 158#define scanning_global_lru(sc) (1) 159#endif 160 161static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 162 struct scan_control *sc) 163{ 164 if (!scanning_global_lru(sc)) 165 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 166 167 return &zone->reclaim_stat; 168} 169 170static unsigned long zone_nr_lru_pages(struct zone *zone, 171 struct scan_control *sc, enum lru_list lru) 172{ 173 if (!scanning_global_lru(sc)) 174 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); 175 176 return zone_page_state(zone, NR_LRU_BASE + lru); 177} 178 179 180/* 181 * Add a shrinker callback to be called from the vm 182 */ 183void register_shrinker(struct shrinker *shrinker) 184{ 185 shrinker->nr = 0; 186 down_write(&shrinker_rwsem); 187 list_add_tail(&shrinker->list, &shrinker_list); 188 up_write(&shrinker_rwsem); 189} 190EXPORT_SYMBOL(register_shrinker); 191 192/* 193 * Remove one 194 */ 195void unregister_shrinker(struct shrinker *shrinker) 196{ 197 down_write(&shrinker_rwsem); 198 list_del(&shrinker->list); 199 up_write(&shrinker_rwsem); 200} 201EXPORT_SYMBOL(unregister_shrinker); 202 203#define SHRINK_BATCH 128 204/* 205 * Call the shrink functions to age shrinkable caches 206 * 207 * Here we assume it costs one seek to replace a lru page and that it also 208 * takes a seek to recreate a cache object. With this in mind we age equal 209 * percentages of the lru and ageable caches. This should balance the seeks 210 * generated by these structures. 211 * 212 * If the vm encountered mapped pages on the LRU it increase the pressure on 213 * slab to avoid swapping. 214 * 215 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 216 * 217 * `lru_pages' represents the number of on-LRU pages in all the zones which 218 * are eligible for the caller's allocation attempt. It is used for balancing 219 * slab reclaim versus page reclaim. 220 * 221 * Returns the number of slab objects which we shrunk. 222 */ 223unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, 224 unsigned long lru_pages) 225{ 226 struct shrinker *shrinker; 227 unsigned long ret = 0; 228 229 if (scanned == 0) 230 scanned = SWAP_CLUSTER_MAX; 231 232 if (!down_read_trylock(&shrinker_rwsem)) 233 return 1; /* Assume we'll be able to shrink next time */ 234 235 list_for_each_entry(shrinker, &shrinker_list, list) { 236 unsigned long long delta; 237 unsigned long total_scan; 238 unsigned long max_pass; 239 240 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask); 241 delta = (4 * scanned) / shrinker->seeks; 242 delta *= max_pass; 243 do_div(delta, lru_pages + 1); 244 shrinker->nr += delta; 245 if (shrinker->nr < 0) { 246 printk(KERN_ERR "shrink_slab: %pF negative objects to " 247 "delete nr=%ld\n", 248 shrinker->shrink, shrinker->nr); 249 shrinker->nr = max_pass; 250 } 251 252 /* 253 * Avoid risking looping forever due to too large nr value: 254 * never try to free more than twice the estimate number of 255 * freeable entries. 256 */ 257 if (shrinker->nr > max_pass * 2) 258 shrinker->nr = max_pass * 2; 259 260 total_scan = shrinker->nr; 261 shrinker->nr = 0; 262 263 while (total_scan >= SHRINK_BATCH) { 264 long this_scan = SHRINK_BATCH; 265 int shrink_ret; 266 int nr_before; 267 268 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); 269 shrink_ret = (*shrinker->shrink)(shrinker, this_scan, 270 gfp_mask); 271 if (shrink_ret == -1) 272 break; 273 if (shrink_ret < nr_before) 274 ret += nr_before - shrink_ret; 275 count_vm_events(SLABS_SCANNED, this_scan); 276 total_scan -= this_scan; 277 278 cond_resched(); 279 } 280 281 shrinker->nr += total_scan; 282 } 283 up_read(&shrinker_rwsem); 284 return ret; 285} 286 287static void set_reclaim_mode(int priority, struct scan_control *sc, 288 bool sync) 289{ 290 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 291 292 /* 293 * Initially assume we are entering either lumpy reclaim or 294 * reclaim/compaction.Depending on the order, we will either set the 295 * sync mode or just reclaim order-0 pages later. 296 */ 297 if (COMPACTION_BUILD) 298 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 299 else 300 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 301 302 /* 303 * Avoid using lumpy reclaim or reclaim/compaction if possible by 304 * restricting when its set to either costly allocations or when 305 * under memory pressure 306 */ 307 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 308 sc->reclaim_mode |= syncmode; 309 else if (sc->order && priority < DEF_PRIORITY - 2) 310 sc->reclaim_mode |= syncmode; 311 else 312 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 313} 314 315static void reset_reclaim_mode(struct scan_control *sc) 316{ 317 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 318} 319 320static inline int is_page_cache_freeable(struct page *page) 321{ 322 /* 323 * A freeable page cache page is referenced only by the caller 324 * that isolated the page, the page cache radix tree and 325 * optional buffer heads at page->private. 326 */ 327 return page_count(page) - page_has_private(page) == 2; 328} 329 330static int may_write_to_queue(struct backing_dev_info *bdi, 331 struct scan_control *sc) 332{ 333 if (current->flags & PF_SWAPWRITE) 334 return 1; 335 if (!bdi_write_congested(bdi)) 336 return 1; 337 if (bdi == current->backing_dev_info) 338 return 1; 339 340 /* lumpy reclaim for hugepage often need a lot of write */ 341 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 342 return 1; 343 return 0; 344} 345 346/* 347 * We detected a synchronous write error writing a page out. Probably 348 * -ENOSPC. We need to propagate that into the address_space for a subsequent 349 * fsync(), msync() or close(). 350 * 351 * The tricky part is that after writepage we cannot touch the mapping: nothing 352 * prevents it from being freed up. But we have a ref on the page and once 353 * that page is locked, the mapping is pinned. 354 * 355 * We're allowed to run sleeping lock_page() here because we know the caller has 356 * __GFP_FS. 357 */ 358static void handle_write_error(struct address_space *mapping, 359 struct page *page, int error) 360{ 361 lock_page_nosync(page); 362 if (page_mapping(page) == mapping) 363 mapping_set_error(mapping, error); 364 unlock_page(page); 365} 366 367/* possible outcome of pageout() */ 368typedef enum { 369 /* failed to write page out, page is locked */ 370 PAGE_KEEP, 371 /* move page to the active list, page is locked */ 372 PAGE_ACTIVATE, 373 /* page has been sent to the disk successfully, page is unlocked */ 374 PAGE_SUCCESS, 375 /* page is clean and locked */ 376 PAGE_CLEAN, 377} pageout_t; 378 379/* 380 * pageout is called by shrink_page_list() for each dirty page. 381 * Calls ->writepage(). 382 */ 383static pageout_t pageout(struct page *page, struct address_space *mapping, 384 struct scan_control *sc) 385{ 386 /* 387 * If the page is dirty, only perform writeback if that write 388 * will be non-blocking. To prevent this allocation from being 389 * stalled by pagecache activity. But note that there may be 390 * stalls if we need to run get_block(). We could test 391 * PagePrivate for that. 392 * 393 * If this process is currently in __generic_file_aio_write() against 394 * this page's queue, we can perform writeback even if that 395 * will block. 396 * 397 * If the page is swapcache, write it back even if that would 398 * block, for some throttling. This happens by accident, because 399 * swap_backing_dev_info is bust: it doesn't reflect the 400 * congestion state of the swapdevs. Easy to fix, if needed. 401 */ 402 if (!is_page_cache_freeable(page)) 403 return PAGE_KEEP; 404 if (!mapping) { 405 /* 406 * Some data journaling orphaned pages can have 407 * page->mapping == NULL while being dirty with clean buffers. 408 */ 409 if (page_has_private(page)) { 410 if (try_to_free_buffers(page)) { 411 ClearPageDirty(page); 412 printk("%s: orphaned page\n", __func__); 413 return PAGE_CLEAN; 414 } 415 } 416 return PAGE_KEEP; 417 } 418 if (mapping->a_ops->writepage == NULL) 419 return PAGE_ACTIVATE; 420 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 421 return PAGE_KEEP; 422 423 if (clear_page_dirty_for_io(page)) { 424 int res; 425 struct writeback_control wbc = { 426 .sync_mode = WB_SYNC_NONE, 427 .nr_to_write = SWAP_CLUSTER_MAX, 428 .range_start = 0, 429 .range_end = LLONG_MAX, 430 .for_reclaim = 1, 431 }; 432 433 SetPageReclaim(page); 434 res = mapping->a_ops->writepage(page, &wbc); 435 if (res < 0) 436 handle_write_error(mapping, page, res); 437 if (res == AOP_WRITEPAGE_ACTIVATE) { 438 ClearPageReclaim(page); 439 return PAGE_ACTIVATE; 440 } 441 442 /* 443 * Wait on writeback if requested to. This happens when 444 * direct reclaiming a large contiguous area and the 445 * first attempt to free a range of pages fails. 446 */ 447 if (PageWriteback(page) && 448 (sc->reclaim_mode & RECLAIM_MODE_SYNC)) 449 wait_on_page_writeback(page); 450 451 if (!PageWriteback(page)) { 452 /* synchronous write or broken a_ops? */ 453 ClearPageReclaim(page); 454 } 455 trace_mm_vmscan_writepage(page, 456 trace_reclaim_flags(page, sc->reclaim_mode)); 457 inc_zone_page_state(page, NR_VMSCAN_WRITE); 458 return PAGE_SUCCESS; 459 } 460 461 return PAGE_CLEAN; 462} 463 464/* 465 * Same as remove_mapping, but if the page is removed from the mapping, it 466 * gets returned with a refcount of 0. 467 */ 468static int __remove_mapping(struct address_space *mapping, struct page *page) 469{ 470 BUG_ON(!PageLocked(page)); 471 BUG_ON(mapping != page_mapping(page)); 472 473 spin_lock_irq(&mapping->tree_lock); 474 /* 475 * The non racy check for a busy page. 476 * 477 * Must be careful with the order of the tests. When someone has 478 * a ref to the page, it may be possible that they dirty it then 479 * drop the reference. So if PageDirty is tested before page_count 480 * here, then the following race may occur: 481 * 482 * get_user_pages(&page); 483 * [user mapping goes away] 484 * write_to(page); 485 * !PageDirty(page) [good] 486 * SetPageDirty(page); 487 * put_page(page); 488 * !page_count(page) [good, discard it] 489 * 490 * [oops, our write_to data is lost] 491 * 492 * Reversing the order of the tests ensures such a situation cannot 493 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 494 * load is not satisfied before that of page->_count. 495 * 496 * Note that if SetPageDirty is always performed via set_page_dirty, 497 * and thus under tree_lock, then this ordering is not required. 498 */ 499 if (!page_freeze_refs(page, 2)) 500 goto cannot_free; 501 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 502 if (unlikely(PageDirty(page))) { 503 page_unfreeze_refs(page, 2); 504 goto cannot_free; 505 } 506 507 if (PageSwapCache(page)) { 508 swp_entry_t swap = { .val = page_private(page) }; 509 __delete_from_swap_cache(page); 510 spin_unlock_irq(&mapping->tree_lock); 511 swapcache_free(swap, page); 512 } else { 513 void (*freepage)(struct page *); 514 515 freepage = mapping->a_ops->freepage; 516 517 __remove_from_page_cache(page); 518 spin_unlock_irq(&mapping->tree_lock); 519 mem_cgroup_uncharge_cache_page(page); 520 521 if (freepage != NULL) 522 freepage(page); 523 } 524 525 return 1; 526 527cannot_free: 528 spin_unlock_irq(&mapping->tree_lock); 529 return 0; 530} 531 532/* 533 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 534 * someone else has a ref on the page, abort and return 0. If it was 535 * successfully detached, return 1. Assumes the caller has a single ref on 536 * this page. 537 */ 538int remove_mapping(struct address_space *mapping, struct page *page) 539{ 540 if (__remove_mapping(mapping, page)) { 541 /* 542 * Unfreezing the refcount with 1 rather than 2 effectively 543 * drops the pagecache ref for us without requiring another 544 * atomic operation. 545 */ 546 page_unfreeze_refs(page, 1); 547 return 1; 548 } 549 return 0; 550} 551 552/** 553 * putback_lru_page - put previously isolated page onto appropriate LRU list 554 * @page: page to be put back to appropriate lru list 555 * 556 * Add previously isolated @page to appropriate LRU list. 557 * Page may still be unevictable for other reasons. 558 * 559 * lru_lock must not be held, interrupts must be enabled. 560 */ 561void putback_lru_page(struct page *page) 562{ 563 int lru; 564 int active = !!TestClearPageActive(page); 565 int was_unevictable = PageUnevictable(page); 566 567 VM_BUG_ON(PageLRU(page)); 568 569redo: 570 ClearPageUnevictable(page); 571 572 if (page_evictable(page, NULL)) { 573 /* 574 * For evictable pages, we can use the cache. 575 * In event of a race, worst case is we end up with an 576 * unevictable page on [in]active list. 577 * We know how to handle that. 578 */ 579 lru = active + page_lru_base_type(page); 580 lru_cache_add_lru(page, lru); 581 } else { 582 /* 583 * Put unevictable pages directly on zone's unevictable 584 * list. 585 */ 586 lru = LRU_UNEVICTABLE; 587 add_page_to_unevictable_list(page); 588 /* 589 * When racing with an mlock clearing (page is 590 * unlocked), make sure that if the other thread does 591 * not observe our setting of PG_lru and fails 592 * isolation, we see PG_mlocked cleared below and move 593 * the page back to the evictable list. 594 * 595 * The other side is TestClearPageMlocked(). 596 */ 597 smp_mb(); 598 } 599 600 /* 601 * page's status can change while we move it among lru. If an evictable 602 * page is on unevictable list, it never be freed. To avoid that, 603 * check after we added it to the list, again. 604 */ 605 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 606 if (!isolate_lru_page(page)) { 607 put_page(page); 608 goto redo; 609 } 610 /* This means someone else dropped this page from LRU 611 * So, it will be freed or putback to LRU again. There is 612 * nothing to do here. 613 */ 614 } 615 616 if (was_unevictable && lru != LRU_UNEVICTABLE) 617 count_vm_event(UNEVICTABLE_PGRESCUED); 618 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 619 count_vm_event(UNEVICTABLE_PGCULLED); 620 621 put_page(page); /* drop ref from isolate */ 622} 623 624enum page_references { 625 PAGEREF_RECLAIM, 626 PAGEREF_RECLAIM_CLEAN, 627 PAGEREF_KEEP, 628 PAGEREF_ACTIVATE, 629}; 630 631static enum page_references page_check_references(struct page *page, 632 struct scan_control *sc) 633{ 634 int referenced_ptes, referenced_page; 635 unsigned long vm_flags; 636 637 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 638 referenced_page = TestClearPageReferenced(page); 639 640 /* Lumpy reclaim - ignore references */ 641 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 642 return PAGEREF_RECLAIM; 643 644 /* 645 * Mlock lost the isolation race with us. Let try_to_unmap() 646 * move the page to the unevictable list. 647 */ 648 if (vm_flags & VM_LOCKED) 649 return PAGEREF_RECLAIM; 650 651 if (referenced_ptes) { 652 if (PageAnon(page)) 653 return PAGEREF_ACTIVATE; 654 /* 655 * All mapped pages start out with page table 656 * references from the instantiating fault, so we need 657 * to look twice if a mapped file page is used more 658 * than once. 659 * 660 * Mark it and spare it for another trip around the 661 * inactive list. Another page table reference will 662 * lead to its activation. 663 * 664 * Note: the mark is set for activated pages as well 665 * so that recently deactivated but used pages are 666 * quickly recovered. 667 */ 668 SetPageReferenced(page); 669 670 if (referenced_page) 671 return PAGEREF_ACTIVATE; 672 673 return PAGEREF_KEEP; 674 } 675 676 /* Reclaim if clean, defer dirty pages to writeback */ 677 if (referenced_page && !PageSwapBacked(page)) 678 return PAGEREF_RECLAIM_CLEAN; 679 680 return PAGEREF_RECLAIM; 681} 682 683static noinline_for_stack void free_page_list(struct list_head *free_pages) 684{ 685 struct pagevec freed_pvec; 686 struct page *page, *tmp; 687 688 pagevec_init(&freed_pvec, 1); 689 690 list_for_each_entry_safe(page, tmp, free_pages, lru) { 691 list_del(&page->lru); 692 if (!pagevec_add(&freed_pvec, page)) { 693 __pagevec_free(&freed_pvec); 694 pagevec_reinit(&freed_pvec); 695 } 696 } 697 698 pagevec_free(&freed_pvec); 699} 700 701/* 702 * shrink_page_list() returns the number of reclaimed pages 703 */ 704static unsigned long shrink_page_list(struct list_head *page_list, 705 struct zone *zone, 706 struct scan_control *sc) 707{ 708 LIST_HEAD(ret_pages); 709 LIST_HEAD(free_pages); 710 int pgactivate = 0; 711 unsigned long nr_dirty = 0; 712 unsigned long nr_congested = 0; 713 unsigned long nr_reclaimed = 0; 714 715 cond_resched(); 716 717 while (!list_empty(page_list)) { 718 enum page_references references; 719 struct address_space *mapping; 720 struct page *page; 721 int may_enter_fs; 722 723 cond_resched(); 724 725 page = lru_to_page(page_list); 726 list_del(&page->lru); 727 728 if (!trylock_page(page)) 729 goto keep; 730 731 VM_BUG_ON(PageActive(page)); 732 VM_BUG_ON(page_zone(page) != zone); 733 734 sc->nr_scanned++; 735 736 if (unlikely(!page_evictable(page, NULL))) 737 goto cull_mlocked; 738 739 if (!sc->may_unmap && page_mapped(page)) 740 goto keep_locked; 741 742 /* Double the slab pressure for mapped and swapcache pages */ 743 if (page_mapped(page) || PageSwapCache(page)) 744 sc->nr_scanned++; 745 746 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 747 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 748 749 if (PageWriteback(page)) { 750 /* 751 * Synchronous reclaim is performed in two passes, 752 * first an asynchronous pass over the list to 753 * start parallel writeback, and a second synchronous 754 * pass to wait for the IO to complete. Wait here 755 * for any page for which writeback has already 756 * started. 757 */ 758 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 759 may_enter_fs) 760 wait_on_page_writeback(page); 761 else { 762 unlock_page(page); 763 goto keep_lumpy; 764 } 765 } 766 767 references = page_check_references(page, sc); 768 switch (references) { 769 case PAGEREF_ACTIVATE: 770 goto activate_locked; 771 case PAGEREF_KEEP: 772 goto keep_locked; 773 case PAGEREF_RECLAIM: 774 case PAGEREF_RECLAIM_CLEAN: 775 ; /* try to reclaim the page below */ 776 } 777 778 /* 779 * Anonymous process memory has backing store? 780 * Try to allocate it some swap space here. 781 */ 782 if (PageAnon(page) && !PageSwapCache(page)) { 783 if (!(sc->gfp_mask & __GFP_IO)) 784 goto keep_locked; 785 if (!add_to_swap(page)) 786 goto activate_locked; 787 may_enter_fs = 1; 788 } 789 790 mapping = page_mapping(page); 791 792 /* 793 * The page is mapped into the page tables of one or more 794 * processes. Try to unmap it here. 795 */ 796 if (page_mapped(page) && mapping) { 797 switch (try_to_unmap(page, TTU_UNMAP)) { 798 case SWAP_FAIL: 799 goto activate_locked; 800 case SWAP_AGAIN: 801 goto keep_locked; 802 case SWAP_MLOCK: 803 goto cull_mlocked; 804 case SWAP_SUCCESS: 805 ; /* try to free the page below */ 806 } 807 } 808 809 if (PageDirty(page)) { 810 nr_dirty++; 811 812 if (references == PAGEREF_RECLAIM_CLEAN) 813 goto keep_locked; 814 if (!may_enter_fs) 815 goto keep_locked; 816 if (!sc->may_writepage) 817 goto keep_locked; 818 819 /* Page is dirty, try to write it out here */ 820 switch (pageout(page, mapping, sc)) { 821 case PAGE_KEEP: 822 nr_congested++; 823 goto keep_locked; 824 case PAGE_ACTIVATE: 825 goto activate_locked; 826 case PAGE_SUCCESS: 827 if (PageWriteback(page)) 828 goto keep_lumpy; 829 if (PageDirty(page)) 830 goto keep; 831 832 /* 833 * A synchronous write - probably a ramdisk. Go 834 * ahead and try to reclaim the page. 835 */ 836 if (!trylock_page(page)) 837 goto keep; 838 if (PageDirty(page) || PageWriteback(page)) 839 goto keep_locked; 840 mapping = page_mapping(page); 841 case PAGE_CLEAN: 842 ; /* try to free the page below */ 843 } 844 } 845 846 /* 847 * If the page has buffers, try to free the buffer mappings 848 * associated with this page. If we succeed we try to free 849 * the page as well. 850 * 851 * We do this even if the page is PageDirty(). 852 * try_to_release_page() does not perform I/O, but it is 853 * possible for a page to have PageDirty set, but it is actually 854 * clean (all its buffers are clean). This happens if the 855 * buffers were written out directly, with submit_bh(). ext3 856 * will do this, as well as the blockdev mapping. 857 * try_to_release_page() will discover that cleanness and will 858 * drop the buffers and mark the page clean - it can be freed. 859 * 860 * Rarely, pages can have buffers and no ->mapping. These are 861 * the pages which were not successfully invalidated in 862 * truncate_complete_page(). We try to drop those buffers here 863 * and if that worked, and the page is no longer mapped into 864 * process address space (page_count == 1) it can be freed. 865 * Otherwise, leave the page on the LRU so it is swappable. 866 */ 867 if (page_has_private(page)) { 868 if (!try_to_release_page(page, sc->gfp_mask)) 869 goto activate_locked; 870 if (!mapping && page_count(page) == 1) { 871 unlock_page(page); 872 if (put_page_testzero(page)) 873 goto free_it; 874 else { 875 /* 876 * rare race with speculative reference. 877 * the speculative reference will free 878 * this page shortly, so we may 879 * increment nr_reclaimed here (and 880 * leave it off the LRU). 881 */ 882 nr_reclaimed++; 883 continue; 884 } 885 } 886 } 887 888 if (!mapping || !__remove_mapping(mapping, page)) 889 goto keep_locked; 890 891 /* 892 * At this point, we have no other references and there is 893 * no way to pick any more up (removed from LRU, removed 894 * from pagecache). Can use non-atomic bitops now (and 895 * we obviously don't have to worry about waking up a process 896 * waiting on the page lock, because there are no references. 897 */ 898 __clear_page_locked(page); 899free_it: 900 nr_reclaimed++; 901 902 /* 903 * Is there need to periodically free_page_list? It would 904 * appear not as the counts should be low 905 */ 906 list_add(&page->lru, &free_pages); 907 continue; 908 909cull_mlocked: 910 if (PageSwapCache(page)) 911 try_to_free_swap(page); 912 unlock_page(page); 913 putback_lru_page(page); 914 reset_reclaim_mode(sc); 915 continue; 916 917activate_locked: 918 /* Not a candidate for swapping, so reclaim swap space. */ 919 if (PageSwapCache(page) && vm_swap_full()) 920 try_to_free_swap(page); 921 VM_BUG_ON(PageActive(page)); 922 SetPageActive(page); 923 pgactivate++; 924keep_locked: 925 unlock_page(page); 926keep: 927 reset_reclaim_mode(sc); 928keep_lumpy: 929 list_add(&page->lru, &ret_pages); 930 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 931 } 932 933 /* 934 * Tag a zone as congested if all the dirty pages encountered were 935 * backed by a congested BDI. In this case, reclaimers should just 936 * back off and wait for congestion to clear because further reclaim 937 * will encounter the same problem 938 */ 939 if (nr_dirty == nr_congested && nr_dirty != 0) 940 zone_set_flag(zone, ZONE_CONGESTED); 941 942 free_page_list(&free_pages); 943 944 list_splice(&ret_pages, page_list); 945 count_vm_events(PGACTIVATE, pgactivate); 946 return nr_reclaimed; 947} 948 949/* 950 * Attempt to remove the specified page from its LRU. Only take this page 951 * if it is of the appropriate PageActive status. Pages which are being 952 * freed elsewhere are also ignored. 953 * 954 * page: page to consider 955 * mode: one of the LRU isolation modes defined above 956 * 957 * returns 0 on success, -ve errno on failure. 958 */ 959int __isolate_lru_page(struct page *page, int mode, int file) 960{ 961 int ret = -EINVAL; 962 963 /* Only take pages on the LRU. */ 964 if (!PageLRU(page)) 965 return ret; 966 967 /* 968 * When checking the active state, we need to be sure we are 969 * dealing with comparible boolean values. Take the logical not 970 * of each. 971 */ 972 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 973 return ret; 974 975 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 976 return ret; 977 978 /* 979 * When this function is being called for lumpy reclaim, we 980 * initially look into all LRU pages, active, inactive and 981 * unevictable; only give shrink_page_list evictable pages. 982 */ 983 if (PageUnevictable(page)) 984 return ret; 985 986 ret = -EBUSY; 987 988 if (likely(get_page_unless_zero(page))) { 989 /* 990 * Be careful not to clear PageLRU until after we're 991 * sure the page is not being freed elsewhere -- the 992 * page release code relies on it. 993 */ 994 ClearPageLRU(page); 995 ret = 0; 996 } 997 998 return ret; 999} 1000 1001/* 1002 * zone->lru_lock is heavily contended. Some of the functions that 1003 * shrink the lists perform better by taking out a batch of pages 1004 * and working on them outside the LRU lock. 1005 * 1006 * For pagecache intensive workloads, this function is the hottest 1007 * spot in the kernel (apart from copy_*_user functions). 1008 * 1009 * Appropriate locks must be held before calling this function. 1010 * 1011 * @nr_to_scan: The number of pages to look through on the list. 1012 * @src: The LRU list to pull pages off. 1013 * @dst: The temp list to put pages on to. 1014 * @scanned: The number of pages that were scanned. 1015 * @order: The caller's attempted allocation order 1016 * @mode: One of the LRU isolation modes 1017 * @file: True [1] if isolating file [!anon] pages 1018 * 1019 * returns how many pages were moved onto *@dst. 1020 */ 1021static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1022 struct list_head *src, struct list_head *dst, 1023 unsigned long *scanned, int order, int mode, int file) 1024{ 1025 unsigned long nr_taken = 0; 1026 unsigned long nr_lumpy_taken = 0; 1027 unsigned long nr_lumpy_dirty = 0; 1028 unsigned long nr_lumpy_failed = 0; 1029 unsigned long scan; 1030 1031 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1032 struct page *page; 1033 unsigned long pfn; 1034 unsigned long end_pfn; 1035 unsigned long page_pfn; 1036 int zone_id; 1037 1038 page = lru_to_page(src); 1039 prefetchw_prev_lru_page(page, src, flags); 1040 1041 VM_BUG_ON(!PageLRU(page)); 1042 1043 switch (__isolate_lru_page(page, mode, file)) { 1044 case 0: 1045 list_move(&page->lru, dst); 1046 mem_cgroup_del_lru(page); 1047 nr_taken++; 1048 break; 1049 1050 case -EBUSY: 1051 /* else it is being freed elsewhere */ 1052 list_move(&page->lru, src); 1053 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1054 continue; 1055 1056 default: 1057 BUG(); 1058 } 1059 1060 if (!order) 1061 continue; 1062 1063 /* 1064 * Attempt to take all pages in the order aligned region 1065 * surrounding the tag page. Only take those pages of 1066 * the same active state as that tag page. We may safely 1067 * round the target page pfn down to the requested order 1068 * as the mem_map is guarenteed valid out to MAX_ORDER, 1069 * where that page is in a different zone we will detect 1070 * it from its zone id and abort this block scan. 1071 */ 1072 zone_id = page_zone_id(page); 1073 page_pfn = page_to_pfn(page); 1074 pfn = page_pfn & ~((1 << order) - 1); 1075 end_pfn = pfn + (1 << order); 1076 for (; pfn < end_pfn; pfn++) { 1077 struct page *cursor_page; 1078 1079 /* The target page is in the block, ignore it. */ 1080 if (unlikely(pfn == page_pfn)) 1081 continue; 1082 1083 /* Avoid holes within the zone. */ 1084 if (unlikely(!pfn_valid_within(pfn))) 1085 break; 1086 1087 cursor_page = pfn_to_page(pfn); 1088 1089 /* Check that we have not crossed a zone boundary. */ 1090 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1091 break; 1092 1093 /* 1094 * If we don't have enough swap space, reclaiming of 1095 * anon page which don't already have a swap slot is 1096 * pointless. 1097 */ 1098 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1099 !PageSwapCache(cursor_page)) 1100 break; 1101 1102 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1103 list_move(&cursor_page->lru, dst); 1104 mem_cgroup_del_lru(cursor_page); 1105 nr_taken++; 1106 nr_lumpy_taken++; 1107 if (PageDirty(cursor_page)) 1108 nr_lumpy_dirty++; 1109 scan++; 1110 } else { 1111 /* the page is freed already. */ 1112 if (!page_count(cursor_page)) 1113 continue; 1114 break; 1115 } 1116 } 1117 1118 /* If we break out of the loop above, lumpy reclaim failed */ 1119 if (pfn < end_pfn) 1120 nr_lumpy_failed++; 1121 } 1122 1123 *scanned = scan; 1124 1125 trace_mm_vmscan_lru_isolate(order, 1126 nr_to_scan, scan, 1127 nr_taken, 1128 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1129 mode); 1130 return nr_taken; 1131} 1132 1133static unsigned long isolate_pages_global(unsigned long nr, 1134 struct list_head *dst, 1135 unsigned long *scanned, int order, 1136 int mode, struct zone *z, 1137 int active, int file) 1138{ 1139 int lru = LRU_BASE; 1140 if (active) 1141 lru += LRU_ACTIVE; 1142 if (file) 1143 lru += LRU_FILE; 1144 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1145 mode, file); 1146} 1147 1148/* 1149 * clear_active_flags() is a helper for shrink_active_list(), clearing 1150 * any active bits from the pages in the list. 1151 */ 1152static unsigned long clear_active_flags(struct list_head *page_list, 1153 unsigned int *count) 1154{ 1155 int nr_active = 0; 1156 int lru; 1157 struct page *page; 1158 1159 list_for_each_entry(page, page_list, lru) { 1160 lru = page_lru_base_type(page); 1161 if (PageActive(page)) { 1162 lru += LRU_ACTIVE; 1163 ClearPageActive(page); 1164 nr_active++; 1165 } 1166 if (count) 1167 count[lru]++; 1168 } 1169 1170 return nr_active; 1171} 1172 1173/** 1174 * isolate_lru_page - tries to isolate a page from its LRU list 1175 * @page: page to isolate from its LRU list 1176 * 1177 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1178 * vmstat statistic corresponding to whatever LRU list the page was on. 1179 * 1180 * Returns 0 if the page was removed from an LRU list. 1181 * Returns -EBUSY if the page was not on an LRU list. 1182 * 1183 * The returned page will have PageLRU() cleared. If it was found on 1184 * the active list, it will have PageActive set. If it was found on 1185 * the unevictable list, it will have the PageUnevictable bit set. That flag 1186 * may need to be cleared by the caller before letting the page go. 1187 * 1188 * The vmstat statistic corresponding to the list on which the page was 1189 * found will be decremented. 1190 * 1191 * Restrictions: 1192 * (1) Must be called with an elevated refcount on the page. This is a 1193 * fundamentnal difference from isolate_lru_pages (which is called 1194 * without a stable reference). 1195 * (2) the lru_lock must not be held. 1196 * (3) interrupts must be enabled. 1197 */ 1198int isolate_lru_page(struct page *page) 1199{ 1200 int ret = -EBUSY; 1201 1202 if (PageLRU(page)) { 1203 struct zone *zone = page_zone(page); 1204 1205 spin_lock_irq(&zone->lru_lock); 1206 if (PageLRU(page) && get_page_unless_zero(page)) { 1207 int lru = page_lru(page); 1208 ret = 0; 1209 ClearPageLRU(page); 1210 1211 del_page_from_lru_list(zone, page, lru); 1212 } 1213 spin_unlock_irq(&zone->lru_lock); 1214 } 1215 return ret; 1216} 1217 1218/* 1219 * Are there way too many processes in the direct reclaim path already? 1220 */ 1221static int too_many_isolated(struct zone *zone, int file, 1222 struct scan_control *sc) 1223{ 1224 unsigned long inactive, isolated; 1225 1226 if (current_is_kswapd()) 1227 return 0; 1228 1229 if (!scanning_global_lru(sc)) 1230 return 0; 1231 1232 if (file) { 1233 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1234 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1235 } else { 1236 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1237 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1238 } 1239 1240 return isolated > inactive; 1241} 1242 1243/* 1244 * TODO: Try merging with migrations version of putback_lru_pages 1245 */ 1246static noinline_for_stack void 1247putback_lru_pages(struct zone *zone, struct scan_control *sc, 1248 unsigned long nr_anon, unsigned long nr_file, 1249 struct list_head *page_list) 1250{ 1251 struct page *page; 1252 struct pagevec pvec; 1253 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1254 1255 pagevec_init(&pvec, 1); 1256 1257 /* 1258 * Put back any unfreeable pages. 1259 */ 1260 spin_lock(&zone->lru_lock); 1261 while (!list_empty(page_list)) { 1262 int lru; 1263 page = lru_to_page(page_list); 1264 VM_BUG_ON(PageLRU(page)); 1265 list_del(&page->lru); 1266 if (unlikely(!page_evictable(page, NULL))) { 1267 spin_unlock_irq(&zone->lru_lock); 1268 putback_lru_page(page); 1269 spin_lock_irq(&zone->lru_lock); 1270 continue; 1271 } 1272 SetPageLRU(page); 1273 lru = page_lru(page); 1274 add_page_to_lru_list(zone, page, lru); 1275 if (is_active_lru(lru)) { 1276 int file = is_file_lru(lru); 1277 reclaim_stat->recent_rotated[file]++; 1278 } 1279 if (!pagevec_add(&pvec, page)) { 1280 spin_unlock_irq(&zone->lru_lock); 1281 __pagevec_release(&pvec); 1282 spin_lock_irq(&zone->lru_lock); 1283 } 1284 } 1285 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1286 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1287 1288 spin_unlock_irq(&zone->lru_lock); 1289 pagevec_release(&pvec); 1290} 1291 1292static noinline_for_stack void update_isolated_counts(struct zone *zone, 1293 struct scan_control *sc, 1294 unsigned long *nr_anon, 1295 unsigned long *nr_file, 1296 struct list_head *isolated_list) 1297{ 1298 unsigned long nr_active; 1299 unsigned int count[NR_LRU_LISTS] = { 0, }; 1300 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1301 1302 nr_active = clear_active_flags(isolated_list, count); 1303 __count_vm_events(PGDEACTIVATE, nr_active); 1304 1305 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1306 -count[LRU_ACTIVE_FILE]); 1307 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1308 -count[LRU_INACTIVE_FILE]); 1309 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1310 -count[LRU_ACTIVE_ANON]); 1311 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1312 -count[LRU_INACTIVE_ANON]); 1313 1314 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1315 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1316 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1317 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1318 1319 reclaim_stat->recent_scanned[0] += *nr_anon; 1320 reclaim_stat->recent_scanned[1] += *nr_file; 1321} 1322 1323/* 1324 * Returns true if the caller should wait to clean dirty/writeback pages. 1325 * 1326 * If we are direct reclaiming for contiguous pages and we do not reclaim 1327 * everything in the list, try again and wait for writeback IO to complete. 1328 * This will stall high-order allocations noticeably. Only do that when really 1329 * need to free the pages under high memory pressure. 1330 */ 1331static inline bool should_reclaim_stall(unsigned long nr_taken, 1332 unsigned long nr_freed, 1333 int priority, 1334 struct scan_control *sc) 1335{ 1336 int lumpy_stall_priority; 1337 1338 /* kswapd should not stall on sync IO */ 1339 if (current_is_kswapd()) 1340 return false; 1341 1342 /* Only stall on lumpy reclaim */ 1343 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1344 return false; 1345 1346 /* If we have relaimed everything on the isolated list, no stall */ 1347 if (nr_freed == nr_taken) 1348 return false; 1349 1350 /* 1351 * For high-order allocations, there are two stall thresholds. 1352 * High-cost allocations stall immediately where as lower 1353 * order allocations such as stacks require the scanning 1354 * priority to be much higher before stalling. 1355 */ 1356 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1357 lumpy_stall_priority = DEF_PRIORITY; 1358 else 1359 lumpy_stall_priority = DEF_PRIORITY / 3; 1360 1361 return priority <= lumpy_stall_priority; 1362} 1363 1364/* 1365 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1366 * of reclaimed pages 1367 */ 1368static noinline_for_stack unsigned long 1369shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1370 struct scan_control *sc, int priority, int file) 1371{ 1372 LIST_HEAD(page_list); 1373 unsigned long nr_scanned; 1374 unsigned long nr_reclaimed = 0; 1375 unsigned long nr_taken; 1376 unsigned long nr_anon; 1377 unsigned long nr_file; 1378 1379 while (unlikely(too_many_isolated(zone, file, sc))) { 1380 congestion_wait(BLK_RW_ASYNC, HZ/10); 1381 1382 /* We are about to die and free our memory. Return now. */ 1383 if (fatal_signal_pending(current)) 1384 return SWAP_CLUSTER_MAX; 1385 } 1386 1387 set_reclaim_mode(priority, sc, false); 1388 lru_add_drain(); 1389 spin_lock_irq(&zone->lru_lock); 1390 1391 if (scanning_global_lru(sc)) { 1392 nr_taken = isolate_pages_global(nr_to_scan, 1393 &page_list, &nr_scanned, sc->order, 1394 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1395 ISOLATE_BOTH : ISOLATE_INACTIVE, 1396 zone, 0, file); 1397 zone->pages_scanned += nr_scanned; 1398 if (current_is_kswapd()) 1399 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1400 nr_scanned); 1401 else 1402 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1403 nr_scanned); 1404 } else { 1405 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1406 &page_list, &nr_scanned, sc->order, 1407 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1408 ISOLATE_BOTH : ISOLATE_INACTIVE, 1409 zone, sc->mem_cgroup, 1410 0, file); 1411 /* 1412 * mem_cgroup_isolate_pages() keeps track of 1413 * scanned pages on its own. 1414 */ 1415 } 1416 1417 if (nr_taken == 0) { 1418 spin_unlock_irq(&zone->lru_lock); 1419 return 0; 1420 } 1421 1422 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1423 1424 spin_unlock_irq(&zone->lru_lock); 1425 1426 nr_reclaimed = shrink_page_list(&page_list, zone, sc); 1427 1428 /* Check if we should syncronously wait for writeback */ 1429 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1430 set_reclaim_mode(priority, sc, true); 1431 nr_reclaimed += shrink_page_list(&page_list, zone, sc); 1432 } 1433 1434 local_irq_disable(); 1435 if (current_is_kswapd()) 1436 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1437 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1438 1439 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1440 1441 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1442 zone_idx(zone), 1443 nr_scanned, nr_reclaimed, 1444 priority, 1445 trace_shrink_flags(file, sc->reclaim_mode)); 1446 return nr_reclaimed; 1447} 1448 1449/* 1450 * This moves pages from the active list to the inactive list. 1451 * 1452 * We move them the other way if the page is referenced by one or more 1453 * processes, from rmap. 1454 * 1455 * If the pages are mostly unmapped, the processing is fast and it is 1456 * appropriate to hold zone->lru_lock across the whole operation. But if 1457 * the pages are mapped, the processing is slow (page_referenced()) so we 1458 * should drop zone->lru_lock around each page. It's impossible to balance 1459 * this, so instead we remove the pages from the LRU while processing them. 1460 * It is safe to rely on PG_active against the non-LRU pages in here because 1461 * nobody will play with that bit on a non-LRU page. 1462 * 1463 * The downside is that we have to touch page->_count against each page. 1464 * But we had to alter page->flags anyway. 1465 */ 1466 1467static void move_active_pages_to_lru(struct zone *zone, 1468 struct list_head *list, 1469 enum lru_list lru) 1470{ 1471 unsigned long pgmoved = 0; 1472 struct pagevec pvec; 1473 struct page *page; 1474 1475 pagevec_init(&pvec, 1); 1476 1477 while (!list_empty(list)) { 1478 page = lru_to_page(list); 1479 1480 VM_BUG_ON(PageLRU(page)); 1481 SetPageLRU(page); 1482 1483 list_move(&page->lru, &zone->lru[lru].list); 1484 mem_cgroup_add_lru_list(page, lru); 1485 pgmoved++; 1486 1487 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1488 spin_unlock_irq(&zone->lru_lock); 1489 if (buffer_heads_over_limit) 1490 pagevec_strip(&pvec); 1491 __pagevec_release(&pvec); 1492 spin_lock_irq(&zone->lru_lock); 1493 } 1494 } 1495 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1496 if (!is_active_lru(lru)) 1497 __count_vm_events(PGDEACTIVATE, pgmoved); 1498} 1499 1500static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1501 struct scan_control *sc, int priority, int file) 1502{ 1503 unsigned long nr_taken; 1504 unsigned long pgscanned; 1505 unsigned long vm_flags; 1506 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1507 LIST_HEAD(l_active); 1508 LIST_HEAD(l_inactive); 1509 struct page *page; 1510 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1511 unsigned long nr_rotated = 0; 1512 1513 lru_add_drain(); 1514 spin_lock_irq(&zone->lru_lock); 1515 if (scanning_global_lru(sc)) { 1516 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1517 &pgscanned, sc->order, 1518 ISOLATE_ACTIVE, zone, 1519 1, file); 1520 zone->pages_scanned += pgscanned; 1521 } else { 1522 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1523 &pgscanned, sc->order, 1524 ISOLATE_ACTIVE, zone, 1525 sc->mem_cgroup, 1, file); 1526 /* 1527 * mem_cgroup_isolate_pages() keeps track of 1528 * scanned pages on its own. 1529 */ 1530 } 1531 1532 reclaim_stat->recent_scanned[file] += nr_taken; 1533 1534 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1535 if (file) 1536 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1537 else 1538 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1539 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1540 spin_unlock_irq(&zone->lru_lock); 1541 1542 while (!list_empty(&l_hold)) { 1543 cond_resched(); 1544 page = lru_to_page(&l_hold); 1545 list_del(&page->lru); 1546 1547 if (unlikely(!page_evictable(page, NULL))) { 1548 putback_lru_page(page); 1549 continue; 1550 } 1551 1552 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1553 nr_rotated++; 1554 /* 1555 * Identify referenced, file-backed active pages and 1556 * give them one more trip around the active list. So 1557 * that executable code get better chances to stay in 1558 * memory under moderate memory pressure. Anon pages 1559 * are not likely to be evicted by use-once streaming 1560 * IO, plus JVM can create lots of anon VM_EXEC pages, 1561 * so we ignore them here. 1562 */ 1563 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1564 list_add(&page->lru, &l_active); 1565 continue; 1566 } 1567 } 1568 1569 ClearPageActive(page); /* we are de-activating */ 1570 list_add(&page->lru, &l_inactive); 1571 } 1572 1573 /* 1574 * Move pages back to the lru list. 1575 */ 1576 spin_lock_irq(&zone->lru_lock); 1577 /* 1578 * Count referenced pages from currently used mappings as rotated, 1579 * even though only some of them are actually re-activated. This 1580 * helps balance scan pressure between file and anonymous pages in 1581 * get_scan_ratio. 1582 */ 1583 reclaim_stat->recent_rotated[file] += nr_rotated; 1584 1585 move_active_pages_to_lru(zone, &l_active, 1586 LRU_ACTIVE + file * LRU_FILE); 1587 move_active_pages_to_lru(zone, &l_inactive, 1588 LRU_BASE + file * LRU_FILE); 1589 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1590 spin_unlock_irq(&zone->lru_lock); 1591} 1592 1593#ifdef CONFIG_SWAP 1594static int inactive_anon_is_low_global(struct zone *zone) 1595{ 1596 unsigned long active, inactive; 1597 1598 active = zone_page_state(zone, NR_ACTIVE_ANON); 1599 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1600 1601 if (inactive * zone->inactive_ratio < active) 1602 return 1; 1603 1604 return 0; 1605} 1606 1607/** 1608 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1609 * @zone: zone to check 1610 * @sc: scan control of this context 1611 * 1612 * Returns true if the zone does not have enough inactive anon pages, 1613 * meaning some active anon pages need to be deactivated. 1614 */ 1615static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1616{ 1617 int low; 1618 1619 /* 1620 * If we don't have swap space, anonymous page deactivation 1621 * is pointless. 1622 */ 1623 if (!total_swap_pages) 1624 return 0; 1625 1626 if (scanning_global_lru(sc)) 1627 low = inactive_anon_is_low_global(zone); 1628 else 1629 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1630 return low; 1631} 1632#else 1633static inline int inactive_anon_is_low(struct zone *zone, 1634 struct scan_control *sc) 1635{ 1636 return 0; 1637} 1638#endif 1639 1640static int inactive_file_is_low_global(struct zone *zone) 1641{ 1642 unsigned long active, inactive; 1643 1644 active = zone_page_state(zone, NR_ACTIVE_FILE); 1645 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1646 1647 return (active > inactive); 1648} 1649 1650/** 1651 * inactive_file_is_low - check if file pages need to be deactivated 1652 * @zone: zone to check 1653 * @sc: scan control of this context 1654 * 1655 * When the system is doing streaming IO, memory pressure here 1656 * ensures that active file pages get deactivated, until more 1657 * than half of the file pages are on the inactive list. 1658 * 1659 * Once we get to that situation, protect the system's working 1660 * set from being evicted by disabling active file page aging. 1661 * 1662 * This uses a different ratio than the anonymous pages, because 1663 * the page cache uses a use-once replacement algorithm. 1664 */ 1665static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1666{ 1667 int low; 1668 1669 if (scanning_global_lru(sc)) 1670 low = inactive_file_is_low_global(zone); 1671 else 1672 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1673 return low; 1674} 1675 1676static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1677 int file) 1678{ 1679 if (file) 1680 return inactive_file_is_low(zone, sc); 1681 else 1682 return inactive_anon_is_low(zone, sc); 1683} 1684 1685static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1686 struct zone *zone, struct scan_control *sc, int priority) 1687{ 1688 int file = is_file_lru(lru); 1689 1690 if (is_active_lru(lru)) { 1691 if (inactive_list_is_low(zone, sc, file)) 1692 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1693 return 0; 1694 } 1695 1696 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1697} 1698 1699/* 1700 * Smallish @nr_to_scan's are deposited in @nr_saved_scan, 1701 * until we collected @swap_cluster_max pages to scan. 1702 */ 1703static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, 1704 unsigned long *nr_saved_scan) 1705{ 1706 unsigned long nr; 1707 1708 *nr_saved_scan += nr_to_scan; 1709 nr = *nr_saved_scan; 1710 1711 if (nr >= SWAP_CLUSTER_MAX) 1712 *nr_saved_scan = 0; 1713 else 1714 nr = 0; 1715 1716 return nr; 1717} 1718 1719/* 1720 * Determine how aggressively the anon and file LRU lists should be 1721 * scanned. The relative value of each set of LRU lists is determined 1722 * by looking at the fraction of the pages scanned we did rotate back 1723 * onto the active list instead of evict. 1724 * 1725 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1726 */ 1727static void get_scan_count(struct zone *zone, struct scan_control *sc, 1728 unsigned long *nr, int priority) 1729{ 1730 unsigned long anon, file, free; 1731 unsigned long anon_prio, file_prio; 1732 unsigned long ap, fp; 1733 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1734 u64 fraction[2], denominator; 1735 enum lru_list l; 1736 int noswap = 0; 1737 1738 /* If we have no swap space, do not bother scanning anon pages. */ 1739 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1740 noswap = 1; 1741 fraction[0] = 0; 1742 fraction[1] = 1; 1743 denominator = 1; 1744 goto out; 1745 } 1746 1747 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1748 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1749 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1750 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1751 1752 if (scanning_global_lru(sc)) { 1753 free = zone_page_state(zone, NR_FREE_PAGES); 1754 /* If we have very few page cache pages, 1755 force-scan anon pages. */ 1756 if (unlikely(file + free <= high_wmark_pages(zone))) { 1757 fraction[0] = 1; 1758 fraction[1] = 0; 1759 denominator = 1; 1760 goto out; 1761 } 1762 } 1763 1764 /* 1765 * With swappiness at 100, anonymous and file have the same priority. 1766 * This scanning priority is essentially the inverse of IO cost. 1767 */ 1768 anon_prio = sc->swappiness; 1769 file_prio = 200 - sc->swappiness; 1770 1771 /* 1772 * OK, so we have swap space and a fair amount of page cache 1773 * pages. We use the recently rotated / recently scanned 1774 * ratios to determine how valuable each cache is. 1775 * 1776 * Because workloads change over time (and to avoid overflow) 1777 * we keep these statistics as a floating average, which ends 1778 * up weighing recent references more than old ones. 1779 * 1780 * anon in [0], file in [1] 1781 */ 1782 spin_lock_irq(&zone->lru_lock); 1783 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1784 reclaim_stat->recent_scanned[0] /= 2; 1785 reclaim_stat->recent_rotated[0] /= 2; 1786 } 1787 1788 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1789 reclaim_stat->recent_scanned[1] /= 2; 1790 reclaim_stat->recent_rotated[1] /= 2; 1791 } 1792 1793 /* 1794 * The amount of pressure on anon vs file pages is inversely 1795 * proportional to the fraction of recently scanned pages on 1796 * each list that were recently referenced and in active use. 1797 */ 1798 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1799 ap /= reclaim_stat->recent_rotated[0] + 1; 1800 1801 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1802 fp /= reclaim_stat->recent_rotated[1] + 1; 1803 spin_unlock_irq(&zone->lru_lock); 1804 1805 fraction[0] = ap; 1806 fraction[1] = fp; 1807 denominator = ap + fp + 1; 1808out: 1809 for_each_evictable_lru(l) { 1810 int file = is_file_lru(l); 1811 unsigned long scan; 1812 1813 scan = zone_nr_lru_pages(zone, sc, l); 1814 if (priority || noswap) { 1815 scan >>= priority; 1816 scan = div64_u64(scan * fraction[file], denominator); 1817 } 1818 nr[l] = nr_scan_try_batch(scan, 1819 &reclaim_stat->nr_saved_scan[l]); 1820 } 1821} 1822 1823/* 1824 * Reclaim/compaction depends on a number of pages being freed. To avoid 1825 * disruption to the system, a small number of order-0 pages continue to be 1826 * rotated and reclaimed in the normal fashion. However, by the time we get 1827 * back to the allocator and call try_to_compact_zone(), we ensure that 1828 * there are enough free pages for it to be likely successful 1829 */ 1830static inline bool should_continue_reclaim(struct zone *zone, 1831 unsigned long nr_reclaimed, 1832 unsigned long nr_scanned, 1833 struct scan_control *sc) 1834{ 1835 unsigned long pages_for_compaction; 1836 unsigned long inactive_lru_pages; 1837 1838 /* If not in reclaim/compaction mode, stop */ 1839 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1840 return false; 1841 1842 /* 1843 * If we failed to reclaim and have scanned the full list, stop. 1844 * NOTE: Checking just nr_reclaimed would exit reclaim/compaction far 1845 * faster but obviously would be less likely to succeed 1846 * allocation. If this is desirable, use GFP_REPEAT to decide 1847 * if both reclaimed and scanned should be checked or just 1848 * reclaimed 1849 */ 1850 if (!nr_reclaimed && !nr_scanned) 1851 return false; 1852 1853 /* 1854 * If we have not reclaimed enough pages for compaction and the 1855 * inactive lists are large enough, continue reclaiming 1856 */ 1857 pages_for_compaction = (2UL << sc->order); 1858 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 1859 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1860 if (sc->nr_reclaimed < pages_for_compaction && 1861 inactive_lru_pages > pages_for_compaction) 1862 return true; 1863 1864 /* If compaction would go ahead or the allocation would succeed, stop */ 1865 switch (compaction_suitable(zone, sc->order)) { 1866 case COMPACT_PARTIAL: 1867 case COMPACT_CONTINUE: 1868 return false; 1869 default: 1870 return true; 1871 } 1872} 1873 1874/* 1875 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1876 */ 1877static void shrink_zone(int priority, struct zone *zone, 1878 struct scan_control *sc) 1879{ 1880 unsigned long nr[NR_LRU_LISTS]; 1881 unsigned long nr_to_scan; 1882 enum lru_list l; 1883 unsigned long nr_reclaimed; 1884 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1885 unsigned long nr_scanned = sc->nr_scanned; 1886 1887restart: 1888 nr_reclaimed = 0; 1889 get_scan_count(zone, sc, nr, priority); 1890 1891 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1892 nr[LRU_INACTIVE_FILE]) { 1893 for_each_evictable_lru(l) { 1894 if (nr[l]) { 1895 nr_to_scan = min_t(unsigned long, 1896 nr[l], SWAP_CLUSTER_MAX); 1897 nr[l] -= nr_to_scan; 1898 1899 nr_reclaimed += shrink_list(l, nr_to_scan, 1900 zone, sc, priority); 1901 } 1902 } 1903 /* 1904 * On large memory systems, scan >> priority can become 1905 * really large. This is fine for the starting priority; 1906 * we want to put equal scanning pressure on each zone. 1907 * However, if the VM has a harder time of freeing pages, 1908 * with multiple processes reclaiming pages, the total 1909 * freeing target can get unreasonably large. 1910 */ 1911 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 1912 break; 1913 } 1914 sc->nr_reclaimed += nr_reclaimed; 1915 1916 /* 1917 * Even if we did not try to evict anon pages at all, we want to 1918 * rebalance the anon lru active/inactive ratio. 1919 */ 1920 if (inactive_anon_is_low(zone, sc)) 1921 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1922 1923 /* reclaim/compaction might need reclaim to continue */ 1924 if (should_continue_reclaim(zone, nr_reclaimed, 1925 sc->nr_scanned - nr_scanned, sc)) 1926 goto restart; 1927 1928 throttle_vm_writeout(sc->gfp_mask); 1929} 1930 1931/* 1932 * This is the direct reclaim path, for page-allocating processes. We only 1933 * try to reclaim pages from zones which will satisfy the caller's allocation 1934 * request. 1935 * 1936 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 1937 * Because: 1938 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1939 * allocation or 1940 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 1941 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 1942 * zone defense algorithm. 1943 * 1944 * If a zone is deemed to be full of pinned pages then just give it a light 1945 * scan then give up on it. 1946 */ 1947static void shrink_zones(int priority, struct zonelist *zonelist, 1948 struct scan_control *sc) 1949{ 1950 struct zoneref *z; 1951 struct zone *zone; 1952 1953 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1954 gfp_zone(sc->gfp_mask), sc->nodemask) { 1955 if (!populated_zone(zone)) 1956 continue; 1957 /* 1958 * Take care memory controller reclaiming has small influence 1959 * to global LRU. 1960 */ 1961 if (scanning_global_lru(sc)) { 1962 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1963 continue; 1964 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1965 continue; /* Let kswapd poll it */ 1966 } 1967 1968 shrink_zone(priority, zone, sc); 1969 } 1970} 1971 1972static bool zone_reclaimable(struct zone *zone) 1973{ 1974 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 1975} 1976 1977/* 1978 * As hibernation is going on, kswapd is freezed so that it can't mark 1979 * the zone into all_unreclaimable. It can't handle OOM during hibernation. 1980 * So let's check zone's unreclaimable in direct reclaim as well as kswapd. 1981 */ 1982static bool all_unreclaimable(struct zonelist *zonelist, 1983 struct scan_control *sc) 1984{ 1985 struct zoneref *z; 1986 struct zone *zone; 1987 bool all_unreclaimable = true; 1988 1989 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1990 gfp_zone(sc->gfp_mask), sc->nodemask) { 1991 if (!populated_zone(zone)) 1992 continue; 1993 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1994 continue; 1995 if (zone_reclaimable(zone)) { 1996 all_unreclaimable = false; 1997 break; 1998 } 1999 } 2000 2001 return all_unreclaimable; 2002} 2003 2004/* 2005 * This is the main entry point to direct page reclaim. 2006 * 2007 * If a full scan of the inactive list fails to free enough memory then we 2008 * are "out of memory" and something needs to be killed. 2009 * 2010 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2011 * high - the zone may be full of dirty or under-writeback pages, which this 2012 * caller can't do much about. We kick the writeback threads and take explicit 2013 * naps in the hope that some of these pages can be written. But if the 2014 * allocating task holds filesystem locks which prevent writeout this might not 2015 * work, and the allocation attempt will fail. 2016 * 2017 * returns: 0, if no pages reclaimed 2018 * else, the number of pages reclaimed 2019 */ 2020static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2021 struct scan_control *sc) 2022{ 2023 int priority; 2024 unsigned long total_scanned = 0; 2025 struct reclaim_state *reclaim_state = current->reclaim_state; 2026 struct zoneref *z; 2027 struct zone *zone; 2028 unsigned long writeback_threshold; 2029 2030 get_mems_allowed(); 2031 delayacct_freepages_start(); 2032 2033 if (scanning_global_lru(sc)) 2034 count_vm_event(ALLOCSTALL); 2035 2036 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2037 sc->nr_scanned = 0; 2038 if (!priority) 2039 disable_swap_token(); 2040 shrink_zones(priority, zonelist, sc); 2041 /* 2042 * Don't shrink slabs when reclaiming memory from 2043 * over limit cgroups 2044 */ 2045 if (scanning_global_lru(sc)) { 2046 unsigned long lru_pages = 0; 2047 for_each_zone_zonelist(zone, z, zonelist, 2048 gfp_zone(sc->gfp_mask)) { 2049 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2050 continue; 2051 2052 lru_pages += zone_reclaimable_pages(zone); 2053 } 2054 2055 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); 2056 if (reclaim_state) { 2057 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2058 reclaim_state->reclaimed_slab = 0; 2059 } 2060 } 2061 total_scanned += sc->nr_scanned; 2062 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2063 goto out; 2064 2065 /* 2066 * Try to write back as many pages as we just scanned. This 2067 * tends to cause slow streaming writers to write data to the 2068 * disk smoothly, at the dirtying rate, which is nice. But 2069 * that's undesirable in laptop mode, where we *want* lumpy 2070 * writeout. So in laptop mode, write out the whole world. 2071 */ 2072 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2073 if (total_scanned > writeback_threshold) { 2074 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2075 sc->may_writepage = 1; 2076 } 2077 2078 /* Take a nap, wait for some writeback to complete */ 2079 if (!sc->hibernation_mode && sc->nr_scanned && 2080 priority < DEF_PRIORITY - 2) { 2081 struct zone *preferred_zone; 2082 2083 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2084 NULL, &preferred_zone); 2085 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2086 } 2087 } 2088 2089out: 2090 delayacct_freepages_end(); 2091 put_mems_allowed(); 2092 2093 if (sc->nr_reclaimed) 2094 return sc->nr_reclaimed; 2095 2096 /* top priority shrink_zones still had more to do? don't OOM, then */ 2097 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2098 return 1; 2099 2100 return 0; 2101} 2102 2103unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2104 gfp_t gfp_mask, nodemask_t *nodemask) 2105{ 2106 unsigned long nr_reclaimed; 2107 struct scan_control sc = { 2108 .gfp_mask = gfp_mask, 2109 .may_writepage = !laptop_mode, 2110 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2111 .may_unmap = 1, 2112 .may_swap = 1, 2113 .swappiness = vm_swappiness, 2114 .order = order, 2115 .mem_cgroup = NULL, 2116 .nodemask = nodemask, 2117 }; 2118 2119 trace_mm_vmscan_direct_reclaim_begin(order, 2120 sc.may_writepage, 2121 gfp_mask); 2122 2123 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2124 2125 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2126 2127 return nr_reclaimed; 2128} 2129 2130#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2131 2132unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2133 gfp_t gfp_mask, bool noswap, 2134 unsigned int swappiness, 2135 struct zone *zone) 2136{ 2137 struct scan_control sc = { 2138 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2139 .may_writepage = !laptop_mode, 2140 .may_unmap = 1, 2141 .may_swap = !noswap, 2142 .swappiness = swappiness, 2143 .order = 0, 2144 .mem_cgroup = mem, 2145 }; 2146 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2147 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2148 2149 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2150 sc.may_writepage, 2151 sc.gfp_mask); 2152 2153 /* 2154 * NOTE: Although we can get the priority field, using it 2155 * here is not a good idea, since it limits the pages we can scan. 2156 * if we don't reclaim here, the shrink_zone from balance_pgdat 2157 * will pick up pages from other mem cgroup's as well. We hack 2158 * the priority and make it zero. 2159 */ 2160 shrink_zone(0, zone, &sc); 2161 2162 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2163 2164 return sc.nr_reclaimed; 2165} 2166 2167unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2168 gfp_t gfp_mask, 2169 bool noswap, 2170 unsigned int swappiness) 2171{ 2172 struct zonelist *zonelist; 2173 unsigned long nr_reclaimed; 2174 struct scan_control sc = { 2175 .may_writepage = !laptop_mode, 2176 .may_unmap = 1, 2177 .may_swap = !noswap, 2178 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2179 .swappiness = swappiness, 2180 .order = 0, 2181 .mem_cgroup = mem_cont, 2182 .nodemask = NULL, /* we don't care the placement */ 2183 }; 2184 2185 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2186 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2187 zonelist = NODE_DATA(numa_node_id())->node_zonelists; 2188 2189 trace_mm_vmscan_memcg_reclaim_begin(0, 2190 sc.may_writepage, 2191 sc.gfp_mask); 2192 2193 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2194 2195 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2196 2197 return nr_reclaimed; 2198} 2199#endif 2200 2201/* 2202 * pgdat_balanced is used when checking if a node is balanced for high-order 2203 * allocations. Only zones that meet watermarks and are in a zone allowed 2204 * by the callers classzone_idx are added to balanced_pages. The total of 2205 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2206 * for the node to be considered balanced. Forcing all zones to be balanced 2207 * for high orders can cause excessive reclaim when there are imbalanced zones. 2208 * The choice of 25% is due to 2209 * o a 16M DMA zone that is balanced will not balance a zone on any 2210 * reasonable sized machine 2211 * o On all other machines, the top zone must be at least a reasonable 2212 * precentage of the middle zones. For example, on 32-bit x86, highmem 2213 * would need to be at least 256M for it to be balance a whole node. 2214 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2215 * to balance a node on its own. These seemed like reasonable ratios. 2216 */ 2217static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2218 int classzone_idx) 2219{ 2220 unsigned long present_pages = 0; 2221 int i; 2222 2223 for (i = 0; i <= classzone_idx; i++) 2224 present_pages += pgdat->node_zones[i].present_pages; 2225 2226 return balanced_pages > (present_pages >> 2); 2227} 2228 2229/* is kswapd sleeping prematurely? */ 2230static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) 2231{ 2232 int i; 2233 unsigned long balanced = 0; 2234 bool all_zones_ok = true; 2235 2236 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2237 if (remaining) 2238 return 1; 2239 2240 /* Check the watermark levels */ 2241 for (i = 0; i < pgdat->nr_zones; i++) { 2242 struct zone *zone = pgdat->node_zones + i; 2243 2244 if (!populated_zone(zone)) 2245 continue; 2246 2247 if (zone->all_unreclaimable) 2248 continue; 2249 2250 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2251 0, 0)) 2252 all_zones_ok = false; 2253 else 2254 balanced += zone->present_pages; 2255 } 2256 2257 /* 2258 * For high-order requests, the balanced zones must contain at least 2259 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2260 * must be balanced 2261 */ 2262 if (order) 2263 return pgdat_balanced(pgdat, balanced, 0); 2264 else 2265 return !all_zones_ok; 2266} 2267 2268/* 2269 * For kswapd, balance_pgdat() will work across all this node's zones until 2270 * they are all at high_wmark_pages(zone). 2271 * 2272 * Returns the final order kswapd was reclaiming at 2273 * 2274 * There is special handling here for zones which are full of pinned pages. 2275 * This can happen if the pages are all mlocked, or if they are all used by 2276 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2277 * What we do is to detect the case where all pages in the zone have been 2278 * scanned twice and there has been zero successful reclaim. Mark the zone as 2279 * dead and from now on, only perform a short scan. Basically we're polling 2280 * the zone for when the problem goes away. 2281 * 2282 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2283 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2284 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2285 * lower zones regardless of the number of free pages in the lower zones. This 2286 * interoperates with the page allocator fallback scheme to ensure that aging 2287 * of pages is balanced across the zones. 2288 */ 2289static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2290 int classzone_idx) 2291{ 2292 int all_zones_ok; 2293 unsigned long balanced; 2294 int priority; 2295 int i; 2296 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2297 unsigned long total_scanned; 2298 struct reclaim_state *reclaim_state = current->reclaim_state; 2299 struct scan_control sc = { 2300 .gfp_mask = GFP_KERNEL, 2301 .may_unmap = 1, 2302 .may_swap = 1, 2303 /* 2304 * kswapd doesn't want to be bailed out while reclaim. because 2305 * we want to put equal scanning pressure on each zone. 2306 */ 2307 .nr_to_reclaim = ULONG_MAX, 2308 .swappiness = vm_swappiness, 2309 .order = order, 2310 .mem_cgroup = NULL, 2311 }; 2312loop_again: 2313 total_scanned = 0; 2314 sc.nr_reclaimed = 0; 2315 sc.may_writepage = !laptop_mode; 2316 count_vm_event(PAGEOUTRUN); 2317 2318 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2319 unsigned long lru_pages = 0; 2320 int has_under_min_watermark_zone = 0; 2321 2322 /* The swap token gets in the way of swapout... */ 2323 if (!priority) 2324 disable_swap_token(); 2325 2326 all_zones_ok = 1; 2327 balanced = 0; 2328 2329 /* 2330 * Scan in the highmem->dma direction for the highest 2331 * zone which needs scanning 2332 */ 2333 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2334 struct zone *zone = pgdat->node_zones + i; 2335 2336 if (!populated_zone(zone)) 2337 continue; 2338 2339 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2340 continue; 2341 2342 /* 2343 * Do some background aging of the anon list, to give 2344 * pages a chance to be referenced before reclaiming. 2345 */ 2346 if (inactive_anon_is_low(zone, &sc)) 2347 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2348 &sc, priority, 0); 2349 2350 if (!zone_watermark_ok_safe(zone, order, 2351 high_wmark_pages(zone), 0, 0)) { 2352 end_zone = i; 2353 break; 2354 } 2355 } 2356 if (i < 0) 2357 goto out; 2358 2359 for (i = 0; i <= end_zone; i++) { 2360 struct zone *zone = pgdat->node_zones + i; 2361 2362 lru_pages += zone_reclaimable_pages(zone); 2363 } 2364 2365 /* 2366 * Now scan the zone in the dma->highmem direction, stopping 2367 * at the last zone which needs scanning. 2368 * 2369 * We do this because the page allocator works in the opposite 2370 * direction. This prevents the page allocator from allocating 2371 * pages behind kswapd's direction of progress, which would 2372 * cause too much scanning of the lower zones. 2373 */ 2374 for (i = 0; i <= end_zone; i++) { 2375 struct zone *zone = pgdat->node_zones + i; 2376 int nr_slab; 2377 2378 if (!populated_zone(zone)) 2379 continue; 2380 2381 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2382 continue; 2383 2384 sc.nr_scanned = 0; 2385 2386 /* 2387 * Call soft limit reclaim before calling shrink_zone. 2388 * For now we ignore the return value 2389 */ 2390 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); 2391 2392 /* 2393 * We put equal pressure on every zone, unless one 2394 * zone has way too many pages free already. 2395 */ 2396 if (!zone_watermark_ok_safe(zone, order, 2397 8*high_wmark_pages(zone), end_zone, 0)) 2398 shrink_zone(priority, zone, &sc); 2399 reclaim_state->reclaimed_slab = 0; 2400 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 2401 lru_pages); 2402 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2403 total_scanned += sc.nr_scanned; 2404 if (zone->all_unreclaimable) 2405 continue; 2406 if (nr_slab == 0 && !zone_reclaimable(zone)) 2407 zone->all_unreclaimable = 1; 2408 /* 2409 * If we've done a decent amount of scanning and 2410 * the reclaim ratio is low, start doing writepage 2411 * even in laptop mode 2412 */ 2413 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2414 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2415 sc.may_writepage = 1; 2416 2417 /* 2418 * Compact the zone for higher orders to reduce 2419 * latencies for higher-order allocations that 2420 * would ordinarily call try_to_compact_pages() 2421 */ 2422 if (sc.order > PAGE_ALLOC_COSTLY_ORDER) 2423 compact_zone_order(zone, sc.order, sc.gfp_mask, 2424 false); 2425 2426 if (!zone_watermark_ok_safe(zone, order, 2427 high_wmark_pages(zone), end_zone, 0)) { 2428 all_zones_ok = 0; 2429 /* 2430 * We are still under min water mark. This 2431 * means that we have a GFP_ATOMIC allocation 2432 * failure risk. Hurry up! 2433 */ 2434 if (!zone_watermark_ok_safe(zone, order, 2435 min_wmark_pages(zone), end_zone, 0)) 2436 has_under_min_watermark_zone = 1; 2437 } else { 2438 /* 2439 * If a zone reaches its high watermark, 2440 * consider it to be no longer congested. It's 2441 * possible there are dirty pages backed by 2442 * congested BDIs but as pressure is relieved, 2443 * spectulatively avoid congestion waits 2444 */ 2445 zone_clear_flag(zone, ZONE_CONGESTED); 2446 if (i <= classzone_idx) 2447 balanced += zone->present_pages; 2448 } 2449 2450 } 2451 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, classzone_idx))) 2452 break; /* kswapd: all done */ 2453 /* 2454 * OK, kswapd is getting into trouble. Take a nap, then take 2455 * another pass across the zones. 2456 */ 2457 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2458 if (has_under_min_watermark_zone) 2459 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2460 else 2461 congestion_wait(BLK_RW_ASYNC, HZ/10); 2462 } 2463 2464 /* 2465 * We do this so kswapd doesn't build up large priorities for 2466 * example when it is freeing in parallel with allocators. It 2467 * matches the direct reclaim path behaviour in terms of impact 2468 * on zone->*_priority. 2469 */ 2470 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2471 break; 2472 } 2473out: 2474 2475 /* 2476 * order-0: All zones must meet high watermark for a balanced node 2477 * high-order: Balanced zones must make up at least 25% of the node 2478 * for the node to be balanced 2479 */ 2480 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, classzone_idx)))) { 2481 cond_resched(); 2482 2483 try_to_freeze(); 2484 2485 /* 2486 * Fragmentation may mean that the system cannot be 2487 * rebalanced for high-order allocations in all zones. 2488 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2489 * it means the zones have been fully scanned and are still 2490 * not balanced. For high-order allocations, there is 2491 * little point trying all over again as kswapd may 2492 * infinite loop. 2493 * 2494 * Instead, recheck all watermarks at order-0 as they 2495 * are the most important. If watermarks are ok, kswapd will go 2496 * back to sleep. High-order users can still perform direct 2497 * reclaim if they wish. 2498 */ 2499 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2500 order = sc.order = 0; 2501 2502 goto loop_again; 2503 } 2504 2505 /* 2506 * If kswapd was reclaiming at a higher order, it has the option of 2507 * sleeping without all zones being balanced. Before it does, it must 2508 * ensure that the watermarks for order-0 on *all* zones are met and 2509 * that the congestion flags are cleared. The congestion flag must 2510 * be cleared as kswapd is the only mechanism that clears the flag 2511 * and it is potentially going to sleep here. 2512 */ 2513 if (order) { 2514 for (i = 0; i <= end_zone; i++) { 2515 struct zone *zone = pgdat->node_zones + i; 2516 2517 if (!populated_zone(zone)) 2518 continue; 2519 2520 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2521 continue; 2522 2523 /* Confirm the zone is balanced for order-0 */ 2524 if (!zone_watermark_ok(zone, 0, 2525 high_wmark_pages(zone), 0, 0)) { 2526 order = sc.order = 0; 2527 goto loop_again; 2528 } 2529 2530 /* If balanced, clear the congested flag */ 2531 zone_clear_flag(zone, ZONE_CONGESTED); 2532 } 2533 } 2534 2535 /* 2536 * Return the order we were reclaiming at so sleeping_prematurely() 2537 * makes a decision on the order we were last reclaiming at. However, 2538 * if another caller entered the allocator slow path while kswapd 2539 * was awake, order will remain at the higher level 2540 */ 2541 return order; 2542} 2543 2544static void kswapd_try_to_sleep(pg_data_t *pgdat, int order) 2545{ 2546 long remaining = 0; 2547 DEFINE_WAIT(wait); 2548 2549 if (freezing(current) || kthread_should_stop()) 2550 return; 2551 2552 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2553 2554 /* Try to sleep for a short interval */ 2555 if (!sleeping_prematurely(pgdat, order, remaining)) { 2556 remaining = schedule_timeout(HZ/10); 2557 finish_wait(&pgdat->kswapd_wait, &wait); 2558 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2559 } 2560 2561 /* 2562 * After a short sleep, check if it was a premature sleep. If not, then 2563 * go fully to sleep until explicitly woken up. 2564 */ 2565 if (!sleeping_prematurely(pgdat, order, remaining)) { 2566 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2567 2568 /* 2569 * vmstat counters are not perfectly accurate and the estimated 2570 * value for counters such as NR_FREE_PAGES can deviate from the 2571 * true value by nr_online_cpus * threshold. To avoid the zone 2572 * watermarks being breached while under pressure, we reduce the 2573 * per-cpu vmstat threshold while kswapd is awake and restore 2574 * them before going back to sleep. 2575 */ 2576 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2577 schedule(); 2578 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2579 } else { 2580 if (remaining) 2581 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2582 else 2583 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2584 } 2585 finish_wait(&pgdat->kswapd_wait, &wait); 2586} 2587 2588/* 2589 * The background pageout daemon, started as a kernel thread 2590 * from the init process. 2591 * 2592 * This basically trickles out pages so that we have _some_ 2593 * free memory available even if there is no other activity 2594 * that frees anything up. This is needed for things like routing 2595 * etc, where we otherwise might have all activity going on in 2596 * asynchronous contexts that cannot page things out. 2597 * 2598 * If there are applications that are active memory-allocators 2599 * (most normal use), this basically shouldn't matter. 2600 */ 2601static int kswapd(void *p) 2602{ 2603 unsigned long order; 2604 int classzone_idx; 2605 pg_data_t *pgdat = (pg_data_t*)p; 2606 struct task_struct *tsk = current; 2607 2608 struct reclaim_state reclaim_state = { 2609 .reclaimed_slab = 0, 2610 }; 2611 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2612 2613 lockdep_set_current_reclaim_state(GFP_KERNEL); 2614 2615 if (!cpumask_empty(cpumask)) 2616 set_cpus_allowed_ptr(tsk, cpumask); 2617 current->reclaim_state = &reclaim_state; 2618 2619 /* 2620 * Tell the memory management that we're a "memory allocator", 2621 * and that if we need more memory we should get access to it 2622 * regardless (see "__alloc_pages()"). "kswapd" should 2623 * never get caught in the normal page freeing logic. 2624 * 2625 * (Kswapd normally doesn't need memory anyway, but sometimes 2626 * you need a small amount of memory in order to be able to 2627 * page out something else, and this flag essentially protects 2628 * us from recursively trying to free more memory as we're 2629 * trying to free the first piece of memory in the first place). 2630 */ 2631 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2632 set_freezable(); 2633 2634 order = 0; 2635 classzone_idx = MAX_NR_ZONES - 1; 2636 for ( ; ; ) { 2637 unsigned long new_order; 2638 int new_classzone_idx; 2639 int ret; 2640 2641 new_order = pgdat->kswapd_max_order; 2642 new_classzone_idx = pgdat->classzone_idx; 2643 pgdat->kswapd_max_order = 0; 2644 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2645 if (order < new_order || classzone_idx > new_classzone_idx) { 2646 /* 2647 * Don't sleep if someone wants a larger 'order' 2648 * allocation or has tigher zone constraints 2649 */ 2650 order = new_order; 2651 classzone_idx = new_classzone_idx; 2652 } else { 2653 kswapd_try_to_sleep(pgdat, order); 2654 order = pgdat->kswapd_max_order; 2655 classzone_idx = pgdat->classzone_idx; 2656 } 2657 2658 ret = try_to_freeze(); 2659 if (kthread_should_stop()) 2660 break; 2661 2662 /* 2663 * We can speed up thawing tasks if we don't call balance_pgdat 2664 * after returning from the refrigerator 2665 */ 2666 if (!ret) { 2667 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2668 order = balance_pgdat(pgdat, order, classzone_idx); 2669 } 2670 } 2671 return 0; 2672} 2673 2674/* 2675 * A zone is low on free memory, so wake its kswapd task to service it. 2676 */ 2677void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2678{ 2679 pg_data_t *pgdat; 2680 2681 if (!populated_zone(zone)) 2682 return; 2683 2684 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2685 return; 2686 pgdat = zone->zone_pgdat; 2687 if (pgdat->kswapd_max_order < order) { 2688 pgdat->kswapd_max_order = order; 2689 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2690 } 2691 if (!waitqueue_active(&pgdat->kswapd_wait)) 2692 return; 2693 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2694 return; 2695 2696 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2697 wake_up_interruptible(&pgdat->kswapd_wait); 2698} 2699 2700/* 2701 * The reclaimable count would be mostly accurate. 2702 * The less reclaimable pages may be 2703 * - mlocked pages, which will be moved to unevictable list when encountered 2704 * - mapped pages, which may require several travels to be reclaimed 2705 * - dirty pages, which is not "instantly" reclaimable 2706 */ 2707unsigned long global_reclaimable_pages(void) 2708{ 2709 int nr; 2710 2711 nr = global_page_state(NR_ACTIVE_FILE) + 2712 global_page_state(NR_INACTIVE_FILE); 2713 2714 if (nr_swap_pages > 0) 2715 nr += global_page_state(NR_ACTIVE_ANON) + 2716 global_page_state(NR_INACTIVE_ANON); 2717 2718 return nr; 2719} 2720 2721unsigned long zone_reclaimable_pages(struct zone *zone) 2722{ 2723 int nr; 2724 2725 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2726 zone_page_state(zone, NR_INACTIVE_FILE); 2727 2728 if (nr_swap_pages > 0) 2729 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2730 zone_page_state(zone, NR_INACTIVE_ANON); 2731 2732 return nr; 2733} 2734 2735#ifdef CONFIG_HIBERNATION 2736/* 2737 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2738 * freed pages. 2739 * 2740 * Rather than trying to age LRUs the aim is to preserve the overall 2741 * LRU order by reclaiming preferentially 2742 * inactive > active > active referenced > active mapped 2743 */ 2744unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2745{ 2746 struct reclaim_state reclaim_state; 2747 struct scan_control sc = { 2748 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2749 .may_swap = 1, 2750 .may_unmap = 1, 2751 .may_writepage = 1, 2752 .nr_to_reclaim = nr_to_reclaim, 2753 .hibernation_mode = 1, 2754 .swappiness = vm_swappiness, 2755 .order = 0, 2756 }; 2757 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2758 struct task_struct *p = current; 2759 unsigned long nr_reclaimed; 2760 2761 p->flags |= PF_MEMALLOC; 2762 lockdep_set_current_reclaim_state(sc.gfp_mask); 2763 reclaim_state.reclaimed_slab = 0; 2764 p->reclaim_state = &reclaim_state; 2765 2766 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2767 2768 p->reclaim_state = NULL; 2769 lockdep_clear_current_reclaim_state(); 2770 p->flags &= ~PF_MEMALLOC; 2771 2772 return nr_reclaimed; 2773} 2774#endif /* CONFIG_HIBERNATION */ 2775 2776/* It's optimal to keep kswapds on the same CPUs as their memory, but 2777 not required for correctness. So if the last cpu in a node goes 2778 away, we get changed to run anywhere: as the first one comes back, 2779 restore their cpu bindings. */ 2780static int __devinit cpu_callback(struct notifier_block *nfb, 2781 unsigned long action, void *hcpu) 2782{ 2783 int nid; 2784 2785 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2786 for_each_node_state(nid, N_HIGH_MEMORY) { 2787 pg_data_t *pgdat = NODE_DATA(nid); 2788 const struct cpumask *mask; 2789 2790 mask = cpumask_of_node(pgdat->node_id); 2791 2792 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2793 /* One of our CPUs online: restore mask */ 2794 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2795 } 2796 } 2797 return NOTIFY_OK; 2798} 2799 2800/* 2801 * This kswapd start function will be called by init and node-hot-add. 2802 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2803 */ 2804int kswapd_run(int nid) 2805{ 2806 pg_data_t *pgdat = NODE_DATA(nid); 2807 int ret = 0; 2808 2809 if (pgdat->kswapd) 2810 return 0; 2811 2812 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2813 if (IS_ERR(pgdat->kswapd)) { 2814 /* failure at boot is fatal */ 2815 BUG_ON(system_state == SYSTEM_BOOTING); 2816 printk("Failed to start kswapd on node %d\n",nid); 2817 ret = -1; 2818 } 2819 return ret; 2820} 2821 2822/* 2823 * Called by memory hotplug when all memory in a node is offlined. 2824 */ 2825void kswapd_stop(int nid) 2826{ 2827 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2828 2829 if (kswapd) 2830 kthread_stop(kswapd); 2831} 2832 2833static int __init kswapd_init(void) 2834{ 2835 int nid; 2836 2837 swap_setup(); 2838 for_each_node_state(nid, N_HIGH_MEMORY) 2839 kswapd_run(nid); 2840 hotcpu_notifier(cpu_callback, 0); 2841 return 0; 2842} 2843 2844module_init(kswapd_init) 2845 2846#ifdef CONFIG_NUMA 2847/* 2848 * Zone reclaim mode 2849 * 2850 * If non-zero call zone_reclaim when the number of free pages falls below 2851 * the watermarks. 2852 */ 2853int zone_reclaim_mode __read_mostly; 2854 2855#define RECLAIM_OFF 0 2856#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2857#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2858#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2859 2860/* 2861 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2862 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2863 * a zone. 2864 */ 2865#define ZONE_RECLAIM_PRIORITY 4 2866 2867/* 2868 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2869 * occur. 2870 */ 2871int sysctl_min_unmapped_ratio = 1; 2872 2873/* 2874 * If the number of slab pages in a zone grows beyond this percentage then 2875 * slab reclaim needs to occur. 2876 */ 2877int sysctl_min_slab_ratio = 5; 2878 2879static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 2880{ 2881 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 2882 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 2883 zone_page_state(zone, NR_ACTIVE_FILE); 2884 2885 /* 2886 * It's possible for there to be more file mapped pages than 2887 * accounted for by the pages on the file LRU lists because 2888 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 2889 */ 2890 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 2891} 2892 2893/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 2894static long zone_pagecache_reclaimable(struct zone *zone) 2895{ 2896 long nr_pagecache_reclaimable; 2897 long delta = 0; 2898 2899 /* 2900 * If RECLAIM_SWAP is set, then all file pages are considered 2901 * potentially reclaimable. Otherwise, we have to worry about 2902 * pages like swapcache and zone_unmapped_file_pages() provides 2903 * a better estimate 2904 */ 2905 if (zone_reclaim_mode & RECLAIM_SWAP) 2906 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 2907 else 2908 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 2909 2910 /* If we can't clean pages, remove dirty pages from consideration */ 2911 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 2912 delta += zone_page_state(zone, NR_FILE_DIRTY); 2913 2914 /* Watch for any possible underflows due to delta */ 2915 if (unlikely(delta > nr_pagecache_reclaimable)) 2916 delta = nr_pagecache_reclaimable; 2917 2918 return nr_pagecache_reclaimable - delta; 2919} 2920 2921/* 2922 * Try to free up some pages from this zone through reclaim. 2923 */ 2924static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2925{ 2926 /* Minimum pages needed in order to stay on node */ 2927 const unsigned long nr_pages = 1 << order; 2928 struct task_struct *p = current; 2929 struct reclaim_state reclaim_state; 2930 int priority; 2931 struct scan_control sc = { 2932 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 2933 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 2934 .may_swap = 1, 2935 .nr_to_reclaim = max_t(unsigned long, nr_pages, 2936 SWAP_CLUSTER_MAX), 2937 .gfp_mask = gfp_mask, 2938 .swappiness = vm_swappiness, 2939 .order = order, 2940 }; 2941 unsigned long nr_slab_pages0, nr_slab_pages1; 2942 2943 cond_resched(); 2944 /* 2945 * We need to be able to allocate from the reserves for RECLAIM_SWAP 2946 * and we also need to be able to write out pages for RECLAIM_WRITE 2947 * and RECLAIM_SWAP. 2948 */ 2949 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 2950 lockdep_set_current_reclaim_state(gfp_mask); 2951 reclaim_state.reclaimed_slab = 0; 2952 p->reclaim_state = &reclaim_state; 2953 2954 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 2955 /* 2956 * Free memory by calling shrink zone with increasing 2957 * priorities until we have enough memory freed. 2958 */ 2959 priority = ZONE_RECLAIM_PRIORITY; 2960 do { 2961 shrink_zone(priority, zone, &sc); 2962 priority--; 2963 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 2964 } 2965 2966 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 2967 if (nr_slab_pages0 > zone->min_slab_pages) { 2968 /* 2969 * shrink_slab() does not currently allow us to determine how 2970 * many pages were freed in this zone. So we take the current 2971 * number of slab pages and shake the slab until it is reduced 2972 * by the same nr_pages that we used for reclaiming unmapped 2973 * pages. 2974 * 2975 * Note that shrink_slab will free memory on all zones and may 2976 * take a long time. 2977 */ 2978 for (;;) { 2979 unsigned long lru_pages = zone_reclaimable_pages(zone); 2980 2981 /* No reclaimable slab or very low memory pressure */ 2982 if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) 2983 break; 2984 2985 /* Freed enough memory */ 2986 nr_slab_pages1 = zone_page_state(zone, 2987 NR_SLAB_RECLAIMABLE); 2988 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 2989 break; 2990 } 2991 2992 /* 2993 * Update nr_reclaimed by the number of slab pages we 2994 * reclaimed from this zone. 2995 */ 2996 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 2997 if (nr_slab_pages1 < nr_slab_pages0) 2998 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 2999 } 3000 3001 p->reclaim_state = NULL; 3002 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3003 lockdep_clear_current_reclaim_state(); 3004 return sc.nr_reclaimed >= nr_pages; 3005} 3006 3007int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3008{ 3009 int node_id; 3010 int ret; 3011 3012 /* 3013 * Zone reclaim reclaims unmapped file backed pages and 3014 * slab pages if we are over the defined limits. 3015 * 3016 * A small portion of unmapped file backed pages is needed for 3017 * file I/O otherwise pages read by file I/O will be immediately 3018 * thrown out if the zone is overallocated. So we do not reclaim 3019 * if less than a specified percentage of the zone is used by 3020 * unmapped file backed pages. 3021 */ 3022 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3023 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3024 return ZONE_RECLAIM_FULL; 3025 3026 if (zone->all_unreclaimable) 3027 return ZONE_RECLAIM_FULL; 3028 3029 /* 3030 * Do not scan if the allocation should not be delayed. 3031 */ 3032 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3033 return ZONE_RECLAIM_NOSCAN; 3034 3035 /* 3036 * Only run zone reclaim on the local zone or on zones that do not 3037 * have associated processors. This will favor the local processor 3038 * over remote processors and spread off node memory allocations 3039 * as wide as possible. 3040 */ 3041 node_id = zone_to_nid(zone); 3042 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3043 return ZONE_RECLAIM_NOSCAN; 3044 3045 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3046 return ZONE_RECLAIM_NOSCAN; 3047 3048 ret = __zone_reclaim(zone, gfp_mask, order); 3049 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3050 3051 if (!ret) 3052 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3053 3054 return ret; 3055} 3056#endif 3057 3058/* 3059 * page_evictable - test whether a page is evictable 3060 * @page: the page to test 3061 * @vma: the VMA in which the page is or will be mapped, may be NULL 3062 * 3063 * Test whether page is evictable--i.e., should be placed on active/inactive 3064 * lists vs unevictable list. The vma argument is !NULL when called from the 3065 * fault path to determine how to instantate a new page. 3066 * 3067 * Reasons page might not be evictable: 3068 * (1) page's mapping marked unevictable 3069 * (2) page is part of an mlocked VMA 3070 * 3071 */ 3072int page_evictable(struct page *page, struct vm_area_struct *vma) 3073{ 3074 3075 if (mapping_unevictable(page_mapping(page))) 3076 return 0; 3077 3078 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3079 return 0; 3080 3081 return 1; 3082} 3083 3084/** 3085 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3086 * @page: page to check evictability and move to appropriate lru list 3087 * @zone: zone page is in 3088 * 3089 * Checks a page for evictability and moves the page to the appropriate 3090 * zone lru list. 3091 * 3092 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3093 * have PageUnevictable set. 3094 */ 3095static void check_move_unevictable_page(struct page *page, struct zone *zone) 3096{ 3097 VM_BUG_ON(PageActive(page)); 3098 3099retry: 3100 ClearPageUnevictable(page); 3101 if (page_evictable(page, NULL)) { 3102 enum lru_list l = page_lru_base_type(page); 3103 3104 __dec_zone_state(zone, NR_UNEVICTABLE); 3105 list_move(&page->lru, &zone->lru[l].list); 3106 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3107 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3108 __count_vm_event(UNEVICTABLE_PGRESCUED); 3109 } else { 3110 /* 3111 * rotate unevictable list 3112 */ 3113 SetPageUnevictable(page); 3114 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3115 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3116 if (page_evictable(page, NULL)) 3117 goto retry; 3118 } 3119} 3120 3121/** 3122 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3123 * @mapping: struct address_space to scan for evictable pages 3124 * 3125 * Scan all pages in mapping. Check unevictable pages for 3126 * evictability and move them to the appropriate zone lru list. 3127 */ 3128void scan_mapping_unevictable_pages(struct address_space *mapping) 3129{ 3130 pgoff_t next = 0; 3131 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3132 PAGE_CACHE_SHIFT; 3133 struct zone *zone; 3134 struct pagevec pvec; 3135 3136 if (mapping->nrpages == 0) 3137 return; 3138 3139 pagevec_init(&pvec, 0); 3140 while (next < end && 3141 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3142 int i; 3143 int pg_scanned = 0; 3144 3145 zone = NULL; 3146 3147 for (i = 0; i < pagevec_count(&pvec); i++) { 3148 struct page *page = pvec.pages[i]; 3149 pgoff_t page_index = page->index; 3150 struct zone *pagezone = page_zone(page); 3151 3152 pg_scanned++; 3153 if (page_index > next) 3154 next = page_index; 3155 next++; 3156 3157 if (pagezone != zone) { 3158 if (zone) 3159 spin_unlock_irq(&zone->lru_lock); 3160 zone = pagezone; 3161 spin_lock_irq(&zone->lru_lock); 3162 } 3163 3164 if (PageLRU(page) && PageUnevictable(page)) 3165 check_move_unevictable_page(page, zone); 3166 } 3167 if (zone) 3168 spin_unlock_irq(&zone->lru_lock); 3169 pagevec_release(&pvec); 3170 3171 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3172 } 3173 3174} 3175 3176/** 3177 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3178 * @zone - zone of which to scan the unevictable list 3179 * 3180 * Scan @zone's unevictable LRU lists to check for pages that have become 3181 * evictable. Move those that have to @zone's inactive list where they 3182 * become candidates for reclaim, unless shrink_inactive_zone() decides 3183 * to reactivate them. Pages that are still unevictable are rotated 3184 * back onto @zone's unevictable list. 3185 */ 3186#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3187static void scan_zone_unevictable_pages(struct zone *zone) 3188{ 3189 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3190 unsigned long scan; 3191 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3192 3193 while (nr_to_scan > 0) { 3194 unsigned long batch_size = min(nr_to_scan, 3195 SCAN_UNEVICTABLE_BATCH_SIZE); 3196 3197 spin_lock_irq(&zone->lru_lock); 3198 for (scan = 0; scan < batch_size; scan++) { 3199 struct page *page = lru_to_page(l_unevictable); 3200 3201 if (!trylock_page(page)) 3202 continue; 3203 3204 prefetchw_prev_lru_page(page, l_unevictable, flags); 3205 3206 if (likely(PageLRU(page) && PageUnevictable(page))) 3207 check_move_unevictable_page(page, zone); 3208 3209 unlock_page(page); 3210 } 3211 spin_unlock_irq(&zone->lru_lock); 3212 3213 nr_to_scan -= batch_size; 3214 } 3215} 3216 3217 3218/** 3219 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3220 * 3221 * A really big hammer: scan all zones' unevictable LRU lists to check for 3222 * pages that have become evictable. Move those back to the zones' 3223 * inactive list where they become candidates for reclaim. 3224 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3225 * and we add swap to the system. As such, it runs in the context of a task 3226 * that has possibly/probably made some previously unevictable pages 3227 * evictable. 3228 */ 3229static void scan_all_zones_unevictable_pages(void) 3230{ 3231 struct zone *zone; 3232 3233 for_each_zone(zone) { 3234 scan_zone_unevictable_pages(zone); 3235 } 3236} 3237 3238/* 3239 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3240 * all nodes' unevictable lists for evictable pages 3241 */ 3242unsigned long scan_unevictable_pages; 3243 3244int scan_unevictable_handler(struct ctl_table *table, int write, 3245 void __user *buffer, 3246 size_t *length, loff_t *ppos) 3247{ 3248 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3249 3250 if (write && *(unsigned long *)table->data) 3251 scan_all_zones_unevictable_pages(); 3252 3253 scan_unevictable_pages = 0; 3254 return 0; 3255} 3256 3257#ifdef CONFIG_NUMA 3258/* 3259 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3260 * a specified node's per zone unevictable lists for evictable pages. 3261 */ 3262 3263static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3264 struct sysdev_attribute *attr, 3265 char *buf) 3266{ 3267 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3268} 3269 3270static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3271 struct sysdev_attribute *attr, 3272 const char *buf, size_t count) 3273{ 3274 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3275 struct zone *zone; 3276 unsigned long res; 3277 unsigned long req = strict_strtoul(buf, 10, &res); 3278 3279 if (!req) 3280 return 1; /* zero is no-op */ 3281 3282 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3283 if (!populated_zone(zone)) 3284 continue; 3285 scan_zone_unevictable_pages(zone); 3286 } 3287 return 1; 3288} 3289 3290 3291static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3292 read_scan_unevictable_node, 3293 write_scan_unevictable_node); 3294 3295int scan_unevictable_register_node(struct node *node) 3296{ 3297 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3298} 3299 3300void scan_unevictable_unregister_node(struct node *node) 3301{ 3302 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3303} 3304#endif 3305