vmscan.c revision 0c917313a8d84fcc0c376db3f7edb7c06f06f920
1/* 2 * linux/mm/vmscan.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * 6 * Swap reorganised 29.12.95, Stephen Tweedie. 7 * kswapd added: 7.1.96 sct 8 * Removed kswapd_ctl limits, and swap out as many pages as needed 9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). 11 * Multiqueue VM started 5.8.00, Rik van Riel. 12 */ 13 14#include <linux/mm.h> 15#include <linux/module.h> 16#include <linux/gfp.h> 17#include <linux/kernel_stat.h> 18#include <linux/swap.h> 19#include <linux/pagemap.h> 20#include <linux/init.h> 21#include <linux/highmem.h> 22#include <linux/vmstat.h> 23#include <linux/file.h> 24#include <linux/writeback.h> 25#include <linux/blkdev.h> 26#include <linux/buffer_head.h> /* for try_to_release_page(), 27 buffer_heads_over_limit */ 28#include <linux/mm_inline.h> 29#include <linux/pagevec.h> 30#include <linux/backing-dev.h> 31#include <linux/rmap.h> 32#include <linux/topology.h> 33#include <linux/cpu.h> 34#include <linux/cpuset.h> 35#include <linux/compaction.h> 36#include <linux/notifier.h> 37#include <linux/rwsem.h> 38#include <linux/delay.h> 39#include <linux/kthread.h> 40#include <linux/freezer.h> 41#include <linux/memcontrol.h> 42#include <linux/delayacct.h> 43#include <linux/sysctl.h> 44#include <linux/oom.h> 45#include <linux/prefetch.h> 46 47#include <asm/tlbflush.h> 48#include <asm/div64.h> 49 50#include <linux/swapops.h> 51 52#include "internal.h" 53 54#define CREATE_TRACE_POINTS 55#include <trace/events/vmscan.h> 56 57/* 58 * reclaim_mode determines how the inactive list is shrunk 59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages 60 * RECLAIM_MODE_ASYNC: Do not block 61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback 62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference 63 * page from the LRU and reclaim all pages within a 64 * naturally aligned range 65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of 66 * order-0 pages and then compact the zone 67 */ 68typedef unsigned __bitwise__ reclaim_mode_t; 69#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) 70#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) 71#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) 72#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) 73#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) 74 75struct scan_control { 76 /* Incremented by the number of inactive pages that were scanned */ 77 unsigned long nr_scanned; 78 79 /* Number of pages freed so far during a call to shrink_zones() */ 80 unsigned long nr_reclaimed; 81 82 /* How many pages shrink_list() should reclaim */ 83 unsigned long nr_to_reclaim; 84 85 unsigned long hibernation_mode; 86 87 /* This context's GFP mask */ 88 gfp_t gfp_mask; 89 90 int may_writepage; 91 92 /* Can mapped pages be reclaimed? */ 93 int may_unmap; 94 95 /* Can pages be swapped as part of reclaim? */ 96 int may_swap; 97 98 int swappiness; 99 100 int order; 101 102 /* 103 * Intend to reclaim enough continuous memory rather than reclaim 104 * enough amount of memory. i.e, mode for high order allocation. 105 */ 106 reclaim_mode_t reclaim_mode; 107 108 /* Which cgroup do we reclaim from */ 109 struct mem_cgroup *mem_cgroup; 110 111 /* 112 * Nodemask of nodes allowed by the caller. If NULL, all nodes 113 * are scanned. 114 */ 115 nodemask_t *nodemask; 116}; 117 118#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 119 120#ifdef ARCH_HAS_PREFETCH 121#define prefetch_prev_lru_page(_page, _base, _field) \ 122 do { \ 123 if ((_page)->lru.prev != _base) { \ 124 struct page *prev; \ 125 \ 126 prev = lru_to_page(&(_page->lru)); \ 127 prefetch(&prev->_field); \ 128 } \ 129 } while (0) 130#else 131#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 132#endif 133 134#ifdef ARCH_HAS_PREFETCHW 135#define prefetchw_prev_lru_page(_page, _base, _field) \ 136 do { \ 137 if ((_page)->lru.prev != _base) { \ 138 struct page *prev; \ 139 \ 140 prev = lru_to_page(&(_page->lru)); \ 141 prefetchw(&prev->_field); \ 142 } \ 143 } while (0) 144#else 145#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 146#endif 147 148/* 149 * From 0 .. 100. Higher means more swappy. 150 */ 151int vm_swappiness = 60; 152long vm_total_pages; /* The total number of pages which the VM controls */ 153 154static LIST_HEAD(shrinker_list); 155static DECLARE_RWSEM(shrinker_rwsem); 156 157#ifdef CONFIG_CGROUP_MEM_RES_CTLR 158#define scanning_global_lru(sc) (!(sc)->mem_cgroup) 159#else 160#define scanning_global_lru(sc) (1) 161#endif 162 163static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 164 struct scan_control *sc) 165{ 166 if (!scanning_global_lru(sc)) 167 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 168 169 return &zone->reclaim_stat; 170} 171 172static unsigned long zone_nr_lru_pages(struct zone *zone, 173 struct scan_control *sc, enum lru_list lru) 174{ 175 if (!scanning_global_lru(sc)) 176 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); 177 178 return zone_page_state(zone, NR_LRU_BASE + lru); 179} 180 181 182/* 183 * Add a shrinker callback to be called from the vm 184 */ 185void register_shrinker(struct shrinker *shrinker) 186{ 187 shrinker->nr = 0; 188 down_write(&shrinker_rwsem); 189 list_add_tail(&shrinker->list, &shrinker_list); 190 up_write(&shrinker_rwsem); 191} 192EXPORT_SYMBOL(register_shrinker); 193 194/* 195 * Remove one 196 */ 197void unregister_shrinker(struct shrinker *shrinker) 198{ 199 down_write(&shrinker_rwsem); 200 list_del(&shrinker->list); 201 up_write(&shrinker_rwsem); 202} 203EXPORT_SYMBOL(unregister_shrinker); 204 205#define SHRINK_BATCH 128 206/* 207 * Call the shrink functions to age shrinkable caches 208 * 209 * Here we assume it costs one seek to replace a lru page and that it also 210 * takes a seek to recreate a cache object. With this in mind we age equal 211 * percentages of the lru and ageable caches. This should balance the seeks 212 * generated by these structures. 213 * 214 * If the vm encountered mapped pages on the LRU it increase the pressure on 215 * slab to avoid swapping. 216 * 217 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 218 * 219 * `lru_pages' represents the number of on-LRU pages in all the zones which 220 * are eligible for the caller's allocation attempt. It is used for balancing 221 * slab reclaim versus page reclaim. 222 * 223 * Returns the number of slab objects which we shrunk. 224 */ 225unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, 226 unsigned long lru_pages) 227{ 228 struct shrinker *shrinker; 229 unsigned long ret = 0; 230 231 if (scanned == 0) 232 scanned = SWAP_CLUSTER_MAX; 233 234 if (!down_read_trylock(&shrinker_rwsem)) { 235 /* Assume we'll be able to shrink next time */ 236 ret = 1; 237 goto out; 238 } 239 240 list_for_each_entry(shrinker, &shrinker_list, list) { 241 unsigned long long delta; 242 unsigned long total_scan; 243 unsigned long max_pass; 244 245 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask); 246 delta = (4 * scanned) / shrinker->seeks; 247 delta *= max_pass; 248 do_div(delta, lru_pages + 1); 249 shrinker->nr += delta; 250 if (shrinker->nr < 0) { 251 printk(KERN_ERR "shrink_slab: %pF negative objects to " 252 "delete nr=%ld\n", 253 shrinker->shrink, shrinker->nr); 254 shrinker->nr = max_pass; 255 } 256 257 /* 258 * Avoid risking looping forever due to too large nr value: 259 * never try to free more than twice the estimate number of 260 * freeable entries. 261 */ 262 if (shrinker->nr > max_pass * 2) 263 shrinker->nr = max_pass * 2; 264 265 total_scan = shrinker->nr; 266 shrinker->nr = 0; 267 268 while (total_scan >= SHRINK_BATCH) { 269 long this_scan = SHRINK_BATCH; 270 int shrink_ret; 271 int nr_before; 272 273 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); 274 shrink_ret = (*shrinker->shrink)(shrinker, this_scan, 275 gfp_mask); 276 if (shrink_ret == -1) 277 break; 278 if (shrink_ret < nr_before) 279 ret += nr_before - shrink_ret; 280 count_vm_events(SLABS_SCANNED, this_scan); 281 total_scan -= this_scan; 282 283 cond_resched(); 284 } 285 286 shrinker->nr += total_scan; 287 } 288 up_read(&shrinker_rwsem); 289out: 290 cond_resched(); 291 return ret; 292} 293 294static void set_reclaim_mode(int priority, struct scan_control *sc, 295 bool sync) 296{ 297 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 298 299 /* 300 * Initially assume we are entering either lumpy reclaim or 301 * reclaim/compaction.Depending on the order, we will either set the 302 * sync mode or just reclaim order-0 pages later. 303 */ 304 if (COMPACTION_BUILD) 305 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 306 else 307 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 308 309 /* 310 * Avoid using lumpy reclaim or reclaim/compaction if possible by 311 * restricting when its set to either costly allocations or when 312 * under memory pressure 313 */ 314 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 315 sc->reclaim_mode |= syncmode; 316 else if (sc->order && priority < DEF_PRIORITY - 2) 317 sc->reclaim_mode |= syncmode; 318 else 319 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 320} 321 322static void reset_reclaim_mode(struct scan_control *sc) 323{ 324 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 325} 326 327static inline int is_page_cache_freeable(struct page *page) 328{ 329 /* 330 * A freeable page cache page is referenced only by the caller 331 * that isolated the page, the page cache radix tree and 332 * optional buffer heads at page->private. 333 */ 334 return page_count(page) - page_has_private(page) == 2; 335} 336 337static int may_write_to_queue(struct backing_dev_info *bdi, 338 struct scan_control *sc) 339{ 340 if (current->flags & PF_SWAPWRITE) 341 return 1; 342 if (!bdi_write_congested(bdi)) 343 return 1; 344 if (bdi == current->backing_dev_info) 345 return 1; 346 347 /* lumpy reclaim for hugepage often need a lot of write */ 348 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 349 return 1; 350 return 0; 351} 352 353/* 354 * We detected a synchronous write error writing a page out. Probably 355 * -ENOSPC. We need to propagate that into the address_space for a subsequent 356 * fsync(), msync() or close(). 357 * 358 * The tricky part is that after writepage we cannot touch the mapping: nothing 359 * prevents it from being freed up. But we have a ref on the page and once 360 * that page is locked, the mapping is pinned. 361 * 362 * We're allowed to run sleeping lock_page() here because we know the caller has 363 * __GFP_FS. 364 */ 365static void handle_write_error(struct address_space *mapping, 366 struct page *page, int error) 367{ 368 lock_page(page); 369 if (page_mapping(page) == mapping) 370 mapping_set_error(mapping, error); 371 unlock_page(page); 372} 373 374/* possible outcome of pageout() */ 375typedef enum { 376 /* failed to write page out, page is locked */ 377 PAGE_KEEP, 378 /* move page to the active list, page is locked */ 379 PAGE_ACTIVATE, 380 /* page has been sent to the disk successfully, page is unlocked */ 381 PAGE_SUCCESS, 382 /* page is clean and locked */ 383 PAGE_CLEAN, 384} pageout_t; 385 386/* 387 * pageout is called by shrink_page_list() for each dirty page. 388 * Calls ->writepage(). 389 */ 390static pageout_t pageout(struct page *page, struct address_space *mapping, 391 struct scan_control *sc) 392{ 393 /* 394 * If the page is dirty, only perform writeback if that write 395 * will be non-blocking. To prevent this allocation from being 396 * stalled by pagecache activity. But note that there may be 397 * stalls if we need to run get_block(). We could test 398 * PagePrivate for that. 399 * 400 * If this process is currently in __generic_file_aio_write() against 401 * this page's queue, we can perform writeback even if that 402 * will block. 403 * 404 * If the page is swapcache, write it back even if that would 405 * block, for some throttling. This happens by accident, because 406 * swap_backing_dev_info is bust: it doesn't reflect the 407 * congestion state of the swapdevs. Easy to fix, if needed. 408 */ 409 if (!is_page_cache_freeable(page)) 410 return PAGE_KEEP; 411 if (!mapping) { 412 /* 413 * Some data journaling orphaned pages can have 414 * page->mapping == NULL while being dirty with clean buffers. 415 */ 416 if (page_has_private(page)) { 417 if (try_to_free_buffers(page)) { 418 ClearPageDirty(page); 419 printk("%s: orphaned page\n", __func__); 420 return PAGE_CLEAN; 421 } 422 } 423 return PAGE_KEEP; 424 } 425 if (mapping->a_ops->writepage == NULL) 426 return PAGE_ACTIVATE; 427 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 428 return PAGE_KEEP; 429 430 if (clear_page_dirty_for_io(page)) { 431 int res; 432 struct writeback_control wbc = { 433 .sync_mode = WB_SYNC_NONE, 434 .nr_to_write = SWAP_CLUSTER_MAX, 435 .range_start = 0, 436 .range_end = LLONG_MAX, 437 .for_reclaim = 1, 438 }; 439 440 SetPageReclaim(page); 441 res = mapping->a_ops->writepage(page, &wbc); 442 if (res < 0) 443 handle_write_error(mapping, page, res); 444 if (res == AOP_WRITEPAGE_ACTIVATE) { 445 ClearPageReclaim(page); 446 return PAGE_ACTIVATE; 447 } 448 449 /* 450 * Wait on writeback if requested to. This happens when 451 * direct reclaiming a large contiguous area and the 452 * first attempt to free a range of pages fails. 453 */ 454 if (PageWriteback(page) && 455 (sc->reclaim_mode & RECLAIM_MODE_SYNC)) 456 wait_on_page_writeback(page); 457 458 if (!PageWriteback(page)) { 459 /* synchronous write or broken a_ops? */ 460 ClearPageReclaim(page); 461 } 462 trace_mm_vmscan_writepage(page, 463 trace_reclaim_flags(page, sc->reclaim_mode)); 464 inc_zone_page_state(page, NR_VMSCAN_WRITE); 465 return PAGE_SUCCESS; 466 } 467 468 return PAGE_CLEAN; 469} 470 471/* 472 * Same as remove_mapping, but if the page is removed from the mapping, it 473 * gets returned with a refcount of 0. 474 */ 475static int __remove_mapping(struct address_space *mapping, struct page *page) 476{ 477 BUG_ON(!PageLocked(page)); 478 BUG_ON(mapping != page_mapping(page)); 479 480 spin_lock_irq(&mapping->tree_lock); 481 /* 482 * The non racy check for a busy page. 483 * 484 * Must be careful with the order of the tests. When someone has 485 * a ref to the page, it may be possible that they dirty it then 486 * drop the reference. So if PageDirty is tested before page_count 487 * here, then the following race may occur: 488 * 489 * get_user_pages(&page); 490 * [user mapping goes away] 491 * write_to(page); 492 * !PageDirty(page) [good] 493 * SetPageDirty(page); 494 * put_page(page); 495 * !page_count(page) [good, discard it] 496 * 497 * [oops, our write_to data is lost] 498 * 499 * Reversing the order of the tests ensures such a situation cannot 500 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 501 * load is not satisfied before that of page->_count. 502 * 503 * Note that if SetPageDirty is always performed via set_page_dirty, 504 * and thus under tree_lock, then this ordering is not required. 505 */ 506 if (!page_freeze_refs(page, 2)) 507 goto cannot_free; 508 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 509 if (unlikely(PageDirty(page))) { 510 page_unfreeze_refs(page, 2); 511 goto cannot_free; 512 } 513 514 if (PageSwapCache(page)) { 515 swp_entry_t swap = { .val = page_private(page) }; 516 __delete_from_swap_cache(page); 517 spin_unlock_irq(&mapping->tree_lock); 518 swapcache_free(swap, page); 519 } else { 520 void (*freepage)(struct page *); 521 522 freepage = mapping->a_ops->freepage; 523 524 __delete_from_page_cache(page); 525 spin_unlock_irq(&mapping->tree_lock); 526 mem_cgroup_uncharge_cache_page(page); 527 528 if (freepage != NULL) 529 freepage(page); 530 } 531 532 return 1; 533 534cannot_free: 535 spin_unlock_irq(&mapping->tree_lock); 536 return 0; 537} 538 539/* 540 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 541 * someone else has a ref on the page, abort and return 0. If it was 542 * successfully detached, return 1. Assumes the caller has a single ref on 543 * this page. 544 */ 545int remove_mapping(struct address_space *mapping, struct page *page) 546{ 547 if (__remove_mapping(mapping, page)) { 548 /* 549 * Unfreezing the refcount with 1 rather than 2 effectively 550 * drops the pagecache ref for us without requiring another 551 * atomic operation. 552 */ 553 page_unfreeze_refs(page, 1); 554 return 1; 555 } 556 return 0; 557} 558 559/** 560 * putback_lru_page - put previously isolated page onto appropriate LRU list 561 * @page: page to be put back to appropriate lru list 562 * 563 * Add previously isolated @page to appropriate LRU list. 564 * Page may still be unevictable for other reasons. 565 * 566 * lru_lock must not be held, interrupts must be enabled. 567 */ 568void putback_lru_page(struct page *page) 569{ 570 int lru; 571 int active = !!TestClearPageActive(page); 572 int was_unevictable = PageUnevictable(page); 573 574 VM_BUG_ON(PageLRU(page)); 575 576redo: 577 ClearPageUnevictable(page); 578 579 if (page_evictable(page, NULL)) { 580 /* 581 * For evictable pages, we can use the cache. 582 * In event of a race, worst case is we end up with an 583 * unevictable page on [in]active list. 584 * We know how to handle that. 585 */ 586 lru = active + page_lru_base_type(page); 587 lru_cache_add_lru(page, lru); 588 } else { 589 /* 590 * Put unevictable pages directly on zone's unevictable 591 * list. 592 */ 593 lru = LRU_UNEVICTABLE; 594 add_page_to_unevictable_list(page); 595 /* 596 * When racing with an mlock clearing (page is 597 * unlocked), make sure that if the other thread does 598 * not observe our setting of PG_lru and fails 599 * isolation, we see PG_mlocked cleared below and move 600 * the page back to the evictable list. 601 * 602 * The other side is TestClearPageMlocked(). 603 */ 604 smp_mb(); 605 } 606 607 /* 608 * page's status can change while we move it among lru. If an evictable 609 * page is on unevictable list, it never be freed. To avoid that, 610 * check after we added it to the list, again. 611 */ 612 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 613 if (!isolate_lru_page(page)) { 614 put_page(page); 615 goto redo; 616 } 617 /* This means someone else dropped this page from LRU 618 * So, it will be freed or putback to LRU again. There is 619 * nothing to do here. 620 */ 621 } 622 623 if (was_unevictable && lru != LRU_UNEVICTABLE) 624 count_vm_event(UNEVICTABLE_PGRESCUED); 625 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 626 count_vm_event(UNEVICTABLE_PGCULLED); 627 628 put_page(page); /* drop ref from isolate */ 629} 630 631enum page_references { 632 PAGEREF_RECLAIM, 633 PAGEREF_RECLAIM_CLEAN, 634 PAGEREF_KEEP, 635 PAGEREF_ACTIVATE, 636}; 637 638static enum page_references page_check_references(struct page *page, 639 struct scan_control *sc) 640{ 641 int referenced_ptes, referenced_page; 642 unsigned long vm_flags; 643 644 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 645 referenced_page = TestClearPageReferenced(page); 646 647 /* Lumpy reclaim - ignore references */ 648 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 649 return PAGEREF_RECLAIM; 650 651 /* 652 * Mlock lost the isolation race with us. Let try_to_unmap() 653 * move the page to the unevictable list. 654 */ 655 if (vm_flags & VM_LOCKED) 656 return PAGEREF_RECLAIM; 657 658 if (referenced_ptes) { 659 if (PageAnon(page)) 660 return PAGEREF_ACTIVATE; 661 /* 662 * All mapped pages start out with page table 663 * references from the instantiating fault, so we need 664 * to look twice if a mapped file page is used more 665 * than once. 666 * 667 * Mark it and spare it for another trip around the 668 * inactive list. Another page table reference will 669 * lead to its activation. 670 * 671 * Note: the mark is set for activated pages as well 672 * so that recently deactivated but used pages are 673 * quickly recovered. 674 */ 675 SetPageReferenced(page); 676 677 if (referenced_page) 678 return PAGEREF_ACTIVATE; 679 680 return PAGEREF_KEEP; 681 } 682 683 /* Reclaim if clean, defer dirty pages to writeback */ 684 if (referenced_page && !PageSwapBacked(page)) 685 return PAGEREF_RECLAIM_CLEAN; 686 687 return PAGEREF_RECLAIM; 688} 689 690static noinline_for_stack void free_page_list(struct list_head *free_pages) 691{ 692 struct pagevec freed_pvec; 693 struct page *page, *tmp; 694 695 pagevec_init(&freed_pvec, 1); 696 697 list_for_each_entry_safe(page, tmp, free_pages, lru) { 698 list_del(&page->lru); 699 if (!pagevec_add(&freed_pvec, page)) { 700 __pagevec_free(&freed_pvec); 701 pagevec_reinit(&freed_pvec); 702 } 703 } 704 705 pagevec_free(&freed_pvec); 706} 707 708/* 709 * shrink_page_list() returns the number of reclaimed pages 710 */ 711static unsigned long shrink_page_list(struct list_head *page_list, 712 struct zone *zone, 713 struct scan_control *sc) 714{ 715 LIST_HEAD(ret_pages); 716 LIST_HEAD(free_pages); 717 int pgactivate = 0; 718 unsigned long nr_dirty = 0; 719 unsigned long nr_congested = 0; 720 unsigned long nr_reclaimed = 0; 721 722 cond_resched(); 723 724 while (!list_empty(page_list)) { 725 enum page_references references; 726 struct address_space *mapping; 727 struct page *page; 728 int may_enter_fs; 729 730 cond_resched(); 731 732 page = lru_to_page(page_list); 733 list_del(&page->lru); 734 735 if (!trylock_page(page)) 736 goto keep; 737 738 VM_BUG_ON(PageActive(page)); 739 VM_BUG_ON(page_zone(page) != zone); 740 741 sc->nr_scanned++; 742 743 if (unlikely(!page_evictable(page, NULL))) 744 goto cull_mlocked; 745 746 if (!sc->may_unmap && page_mapped(page)) 747 goto keep_locked; 748 749 /* Double the slab pressure for mapped and swapcache pages */ 750 if (page_mapped(page) || PageSwapCache(page)) 751 sc->nr_scanned++; 752 753 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 754 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 755 756 if (PageWriteback(page)) { 757 /* 758 * Synchronous reclaim is performed in two passes, 759 * first an asynchronous pass over the list to 760 * start parallel writeback, and a second synchronous 761 * pass to wait for the IO to complete. Wait here 762 * for any page for which writeback has already 763 * started. 764 */ 765 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 766 may_enter_fs) 767 wait_on_page_writeback(page); 768 else { 769 unlock_page(page); 770 goto keep_lumpy; 771 } 772 } 773 774 references = page_check_references(page, sc); 775 switch (references) { 776 case PAGEREF_ACTIVATE: 777 goto activate_locked; 778 case PAGEREF_KEEP: 779 goto keep_locked; 780 case PAGEREF_RECLAIM: 781 case PAGEREF_RECLAIM_CLEAN: 782 ; /* try to reclaim the page below */ 783 } 784 785 /* 786 * Anonymous process memory has backing store? 787 * Try to allocate it some swap space here. 788 */ 789 if (PageAnon(page) && !PageSwapCache(page)) { 790 if (!(sc->gfp_mask & __GFP_IO)) 791 goto keep_locked; 792 if (!add_to_swap(page)) 793 goto activate_locked; 794 may_enter_fs = 1; 795 } 796 797 mapping = page_mapping(page); 798 799 /* 800 * The page is mapped into the page tables of one or more 801 * processes. Try to unmap it here. 802 */ 803 if (page_mapped(page) && mapping) { 804 switch (try_to_unmap(page, TTU_UNMAP)) { 805 case SWAP_FAIL: 806 goto activate_locked; 807 case SWAP_AGAIN: 808 goto keep_locked; 809 case SWAP_MLOCK: 810 goto cull_mlocked; 811 case SWAP_SUCCESS: 812 ; /* try to free the page below */ 813 } 814 } 815 816 if (PageDirty(page)) { 817 nr_dirty++; 818 819 if (references == PAGEREF_RECLAIM_CLEAN) 820 goto keep_locked; 821 if (!may_enter_fs) 822 goto keep_locked; 823 if (!sc->may_writepage) 824 goto keep_locked; 825 826 /* Page is dirty, try to write it out here */ 827 switch (pageout(page, mapping, sc)) { 828 case PAGE_KEEP: 829 nr_congested++; 830 goto keep_locked; 831 case PAGE_ACTIVATE: 832 goto activate_locked; 833 case PAGE_SUCCESS: 834 if (PageWriteback(page)) 835 goto keep_lumpy; 836 if (PageDirty(page)) 837 goto keep; 838 839 /* 840 * A synchronous write - probably a ramdisk. Go 841 * ahead and try to reclaim the page. 842 */ 843 if (!trylock_page(page)) 844 goto keep; 845 if (PageDirty(page) || PageWriteback(page)) 846 goto keep_locked; 847 mapping = page_mapping(page); 848 case PAGE_CLEAN: 849 ; /* try to free the page below */ 850 } 851 } 852 853 /* 854 * If the page has buffers, try to free the buffer mappings 855 * associated with this page. If we succeed we try to free 856 * the page as well. 857 * 858 * We do this even if the page is PageDirty(). 859 * try_to_release_page() does not perform I/O, but it is 860 * possible for a page to have PageDirty set, but it is actually 861 * clean (all its buffers are clean). This happens if the 862 * buffers were written out directly, with submit_bh(). ext3 863 * will do this, as well as the blockdev mapping. 864 * try_to_release_page() will discover that cleanness and will 865 * drop the buffers and mark the page clean - it can be freed. 866 * 867 * Rarely, pages can have buffers and no ->mapping. These are 868 * the pages which were not successfully invalidated in 869 * truncate_complete_page(). We try to drop those buffers here 870 * and if that worked, and the page is no longer mapped into 871 * process address space (page_count == 1) it can be freed. 872 * Otherwise, leave the page on the LRU so it is swappable. 873 */ 874 if (page_has_private(page)) { 875 if (!try_to_release_page(page, sc->gfp_mask)) 876 goto activate_locked; 877 if (!mapping && page_count(page) == 1) { 878 unlock_page(page); 879 if (put_page_testzero(page)) 880 goto free_it; 881 else { 882 /* 883 * rare race with speculative reference. 884 * the speculative reference will free 885 * this page shortly, so we may 886 * increment nr_reclaimed here (and 887 * leave it off the LRU). 888 */ 889 nr_reclaimed++; 890 continue; 891 } 892 } 893 } 894 895 if (!mapping || !__remove_mapping(mapping, page)) 896 goto keep_locked; 897 898 /* 899 * At this point, we have no other references and there is 900 * no way to pick any more up (removed from LRU, removed 901 * from pagecache). Can use non-atomic bitops now (and 902 * we obviously don't have to worry about waking up a process 903 * waiting on the page lock, because there are no references. 904 */ 905 __clear_page_locked(page); 906free_it: 907 nr_reclaimed++; 908 909 /* 910 * Is there need to periodically free_page_list? It would 911 * appear not as the counts should be low 912 */ 913 list_add(&page->lru, &free_pages); 914 continue; 915 916cull_mlocked: 917 if (PageSwapCache(page)) 918 try_to_free_swap(page); 919 unlock_page(page); 920 putback_lru_page(page); 921 reset_reclaim_mode(sc); 922 continue; 923 924activate_locked: 925 /* Not a candidate for swapping, so reclaim swap space. */ 926 if (PageSwapCache(page) && vm_swap_full()) 927 try_to_free_swap(page); 928 VM_BUG_ON(PageActive(page)); 929 SetPageActive(page); 930 pgactivate++; 931keep_locked: 932 unlock_page(page); 933keep: 934 reset_reclaim_mode(sc); 935keep_lumpy: 936 list_add(&page->lru, &ret_pages); 937 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 938 } 939 940 /* 941 * Tag a zone as congested if all the dirty pages encountered were 942 * backed by a congested BDI. In this case, reclaimers should just 943 * back off and wait for congestion to clear because further reclaim 944 * will encounter the same problem 945 */ 946 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) 947 zone_set_flag(zone, ZONE_CONGESTED); 948 949 free_page_list(&free_pages); 950 951 list_splice(&ret_pages, page_list); 952 count_vm_events(PGACTIVATE, pgactivate); 953 return nr_reclaimed; 954} 955 956/* 957 * Attempt to remove the specified page from its LRU. Only take this page 958 * if it is of the appropriate PageActive status. Pages which are being 959 * freed elsewhere are also ignored. 960 * 961 * page: page to consider 962 * mode: one of the LRU isolation modes defined above 963 * 964 * returns 0 on success, -ve errno on failure. 965 */ 966int __isolate_lru_page(struct page *page, int mode, int file) 967{ 968 int ret = -EINVAL; 969 970 /* Only take pages on the LRU. */ 971 if (!PageLRU(page)) 972 return ret; 973 974 /* 975 * When checking the active state, we need to be sure we are 976 * dealing with comparible boolean values. Take the logical not 977 * of each. 978 */ 979 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 980 return ret; 981 982 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 983 return ret; 984 985 /* 986 * When this function is being called for lumpy reclaim, we 987 * initially look into all LRU pages, active, inactive and 988 * unevictable; only give shrink_page_list evictable pages. 989 */ 990 if (PageUnevictable(page)) 991 return ret; 992 993 ret = -EBUSY; 994 995 if (likely(get_page_unless_zero(page))) { 996 /* 997 * Be careful not to clear PageLRU until after we're 998 * sure the page is not being freed elsewhere -- the 999 * page release code relies on it. 1000 */ 1001 ClearPageLRU(page); 1002 ret = 0; 1003 } 1004 1005 return ret; 1006} 1007 1008/* 1009 * zone->lru_lock is heavily contended. Some of the functions that 1010 * shrink the lists perform better by taking out a batch of pages 1011 * and working on them outside the LRU lock. 1012 * 1013 * For pagecache intensive workloads, this function is the hottest 1014 * spot in the kernel (apart from copy_*_user functions). 1015 * 1016 * Appropriate locks must be held before calling this function. 1017 * 1018 * @nr_to_scan: The number of pages to look through on the list. 1019 * @src: The LRU list to pull pages off. 1020 * @dst: The temp list to put pages on to. 1021 * @scanned: The number of pages that were scanned. 1022 * @order: The caller's attempted allocation order 1023 * @mode: One of the LRU isolation modes 1024 * @file: True [1] if isolating file [!anon] pages 1025 * 1026 * returns how many pages were moved onto *@dst. 1027 */ 1028static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1029 struct list_head *src, struct list_head *dst, 1030 unsigned long *scanned, int order, int mode, int file) 1031{ 1032 unsigned long nr_taken = 0; 1033 unsigned long nr_lumpy_taken = 0; 1034 unsigned long nr_lumpy_dirty = 0; 1035 unsigned long nr_lumpy_failed = 0; 1036 unsigned long scan; 1037 1038 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1039 struct page *page; 1040 unsigned long pfn; 1041 unsigned long end_pfn; 1042 unsigned long page_pfn; 1043 int zone_id; 1044 1045 page = lru_to_page(src); 1046 prefetchw_prev_lru_page(page, src, flags); 1047 1048 VM_BUG_ON(!PageLRU(page)); 1049 1050 switch (__isolate_lru_page(page, mode, file)) { 1051 case 0: 1052 list_move(&page->lru, dst); 1053 mem_cgroup_del_lru(page); 1054 nr_taken += hpage_nr_pages(page); 1055 break; 1056 1057 case -EBUSY: 1058 /* else it is being freed elsewhere */ 1059 list_move(&page->lru, src); 1060 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1061 continue; 1062 1063 default: 1064 BUG(); 1065 } 1066 1067 if (!order) 1068 continue; 1069 1070 /* 1071 * Attempt to take all pages in the order aligned region 1072 * surrounding the tag page. Only take those pages of 1073 * the same active state as that tag page. We may safely 1074 * round the target page pfn down to the requested order 1075 * as the mem_map is guaranteed valid out to MAX_ORDER, 1076 * where that page is in a different zone we will detect 1077 * it from its zone id and abort this block scan. 1078 */ 1079 zone_id = page_zone_id(page); 1080 page_pfn = page_to_pfn(page); 1081 pfn = page_pfn & ~((1 << order) - 1); 1082 end_pfn = pfn + (1 << order); 1083 for (; pfn < end_pfn; pfn++) { 1084 struct page *cursor_page; 1085 1086 /* The target page is in the block, ignore it. */ 1087 if (unlikely(pfn == page_pfn)) 1088 continue; 1089 1090 /* Avoid holes within the zone. */ 1091 if (unlikely(!pfn_valid_within(pfn))) 1092 break; 1093 1094 cursor_page = pfn_to_page(pfn); 1095 1096 /* Check that we have not crossed a zone boundary. */ 1097 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1098 break; 1099 1100 /* 1101 * If we don't have enough swap space, reclaiming of 1102 * anon page which don't already have a swap slot is 1103 * pointless. 1104 */ 1105 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1106 !PageSwapCache(cursor_page)) 1107 break; 1108 1109 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1110 list_move(&cursor_page->lru, dst); 1111 mem_cgroup_del_lru(cursor_page); 1112 nr_taken += hpage_nr_pages(page); 1113 nr_lumpy_taken++; 1114 if (PageDirty(cursor_page)) 1115 nr_lumpy_dirty++; 1116 scan++; 1117 } else { 1118 /* the page is freed already. */ 1119 if (!page_count(cursor_page)) 1120 continue; 1121 break; 1122 } 1123 } 1124 1125 /* If we break out of the loop above, lumpy reclaim failed */ 1126 if (pfn < end_pfn) 1127 nr_lumpy_failed++; 1128 } 1129 1130 *scanned = scan; 1131 1132 trace_mm_vmscan_lru_isolate(order, 1133 nr_to_scan, scan, 1134 nr_taken, 1135 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1136 mode); 1137 return nr_taken; 1138} 1139 1140static unsigned long isolate_pages_global(unsigned long nr, 1141 struct list_head *dst, 1142 unsigned long *scanned, int order, 1143 int mode, struct zone *z, 1144 int active, int file) 1145{ 1146 int lru = LRU_BASE; 1147 if (active) 1148 lru += LRU_ACTIVE; 1149 if (file) 1150 lru += LRU_FILE; 1151 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1152 mode, file); 1153} 1154 1155/* 1156 * clear_active_flags() is a helper for shrink_active_list(), clearing 1157 * any active bits from the pages in the list. 1158 */ 1159static unsigned long clear_active_flags(struct list_head *page_list, 1160 unsigned int *count) 1161{ 1162 int nr_active = 0; 1163 int lru; 1164 struct page *page; 1165 1166 list_for_each_entry(page, page_list, lru) { 1167 int numpages = hpage_nr_pages(page); 1168 lru = page_lru_base_type(page); 1169 if (PageActive(page)) { 1170 lru += LRU_ACTIVE; 1171 ClearPageActive(page); 1172 nr_active += numpages; 1173 } 1174 if (count) 1175 count[lru] += numpages; 1176 } 1177 1178 return nr_active; 1179} 1180 1181/** 1182 * isolate_lru_page - tries to isolate a page from its LRU list 1183 * @page: page to isolate from its LRU list 1184 * 1185 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1186 * vmstat statistic corresponding to whatever LRU list the page was on. 1187 * 1188 * Returns 0 if the page was removed from an LRU list. 1189 * Returns -EBUSY if the page was not on an LRU list. 1190 * 1191 * The returned page will have PageLRU() cleared. If it was found on 1192 * the active list, it will have PageActive set. If it was found on 1193 * the unevictable list, it will have the PageUnevictable bit set. That flag 1194 * may need to be cleared by the caller before letting the page go. 1195 * 1196 * The vmstat statistic corresponding to the list on which the page was 1197 * found will be decremented. 1198 * 1199 * Restrictions: 1200 * (1) Must be called with an elevated refcount on the page. This is a 1201 * fundamentnal difference from isolate_lru_pages (which is called 1202 * without a stable reference). 1203 * (2) the lru_lock must not be held. 1204 * (3) interrupts must be enabled. 1205 */ 1206int isolate_lru_page(struct page *page) 1207{ 1208 int ret = -EBUSY; 1209 1210 VM_BUG_ON(!page_count(page)); 1211 1212 if (PageLRU(page)) { 1213 struct zone *zone = page_zone(page); 1214 1215 spin_lock_irq(&zone->lru_lock); 1216 if (PageLRU(page)) { 1217 int lru = page_lru(page); 1218 ret = 0; 1219 get_page(page); 1220 ClearPageLRU(page); 1221 1222 del_page_from_lru_list(zone, page, lru); 1223 } 1224 spin_unlock_irq(&zone->lru_lock); 1225 } 1226 return ret; 1227} 1228 1229/* 1230 * Are there way too many processes in the direct reclaim path already? 1231 */ 1232static int too_many_isolated(struct zone *zone, int file, 1233 struct scan_control *sc) 1234{ 1235 unsigned long inactive, isolated; 1236 1237 if (current_is_kswapd()) 1238 return 0; 1239 1240 if (!scanning_global_lru(sc)) 1241 return 0; 1242 1243 if (file) { 1244 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1245 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1246 } else { 1247 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1248 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1249 } 1250 1251 return isolated > inactive; 1252} 1253 1254/* 1255 * TODO: Try merging with migrations version of putback_lru_pages 1256 */ 1257static noinline_for_stack void 1258putback_lru_pages(struct zone *zone, struct scan_control *sc, 1259 unsigned long nr_anon, unsigned long nr_file, 1260 struct list_head *page_list) 1261{ 1262 struct page *page; 1263 struct pagevec pvec; 1264 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1265 1266 pagevec_init(&pvec, 1); 1267 1268 /* 1269 * Put back any unfreeable pages. 1270 */ 1271 spin_lock(&zone->lru_lock); 1272 while (!list_empty(page_list)) { 1273 int lru; 1274 page = lru_to_page(page_list); 1275 VM_BUG_ON(PageLRU(page)); 1276 list_del(&page->lru); 1277 if (unlikely(!page_evictable(page, NULL))) { 1278 spin_unlock_irq(&zone->lru_lock); 1279 putback_lru_page(page); 1280 spin_lock_irq(&zone->lru_lock); 1281 continue; 1282 } 1283 SetPageLRU(page); 1284 lru = page_lru(page); 1285 add_page_to_lru_list(zone, page, lru); 1286 if (is_active_lru(lru)) { 1287 int file = is_file_lru(lru); 1288 int numpages = hpage_nr_pages(page); 1289 reclaim_stat->recent_rotated[file] += numpages; 1290 } 1291 if (!pagevec_add(&pvec, page)) { 1292 spin_unlock_irq(&zone->lru_lock); 1293 __pagevec_release(&pvec); 1294 spin_lock_irq(&zone->lru_lock); 1295 } 1296 } 1297 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1298 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1299 1300 spin_unlock_irq(&zone->lru_lock); 1301 pagevec_release(&pvec); 1302} 1303 1304static noinline_for_stack void update_isolated_counts(struct zone *zone, 1305 struct scan_control *sc, 1306 unsigned long *nr_anon, 1307 unsigned long *nr_file, 1308 struct list_head *isolated_list) 1309{ 1310 unsigned long nr_active; 1311 unsigned int count[NR_LRU_LISTS] = { 0, }; 1312 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1313 1314 nr_active = clear_active_flags(isolated_list, count); 1315 __count_vm_events(PGDEACTIVATE, nr_active); 1316 1317 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1318 -count[LRU_ACTIVE_FILE]); 1319 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1320 -count[LRU_INACTIVE_FILE]); 1321 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1322 -count[LRU_ACTIVE_ANON]); 1323 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1324 -count[LRU_INACTIVE_ANON]); 1325 1326 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1327 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1328 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1329 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1330 1331 reclaim_stat->recent_scanned[0] += *nr_anon; 1332 reclaim_stat->recent_scanned[1] += *nr_file; 1333} 1334 1335/* 1336 * Returns true if the caller should wait to clean dirty/writeback pages. 1337 * 1338 * If we are direct reclaiming for contiguous pages and we do not reclaim 1339 * everything in the list, try again and wait for writeback IO to complete. 1340 * This will stall high-order allocations noticeably. Only do that when really 1341 * need to free the pages under high memory pressure. 1342 */ 1343static inline bool should_reclaim_stall(unsigned long nr_taken, 1344 unsigned long nr_freed, 1345 int priority, 1346 struct scan_control *sc) 1347{ 1348 int lumpy_stall_priority; 1349 1350 /* kswapd should not stall on sync IO */ 1351 if (current_is_kswapd()) 1352 return false; 1353 1354 /* Only stall on lumpy reclaim */ 1355 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1356 return false; 1357 1358 /* If we have relaimed everything on the isolated list, no stall */ 1359 if (nr_freed == nr_taken) 1360 return false; 1361 1362 /* 1363 * For high-order allocations, there are two stall thresholds. 1364 * High-cost allocations stall immediately where as lower 1365 * order allocations such as stacks require the scanning 1366 * priority to be much higher before stalling. 1367 */ 1368 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1369 lumpy_stall_priority = DEF_PRIORITY; 1370 else 1371 lumpy_stall_priority = DEF_PRIORITY / 3; 1372 1373 return priority <= lumpy_stall_priority; 1374} 1375 1376/* 1377 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1378 * of reclaimed pages 1379 */ 1380static noinline_for_stack unsigned long 1381shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1382 struct scan_control *sc, int priority, int file) 1383{ 1384 LIST_HEAD(page_list); 1385 unsigned long nr_scanned; 1386 unsigned long nr_reclaimed = 0; 1387 unsigned long nr_taken; 1388 unsigned long nr_anon; 1389 unsigned long nr_file; 1390 1391 while (unlikely(too_many_isolated(zone, file, sc))) { 1392 congestion_wait(BLK_RW_ASYNC, HZ/10); 1393 1394 /* We are about to die and free our memory. Return now. */ 1395 if (fatal_signal_pending(current)) 1396 return SWAP_CLUSTER_MAX; 1397 } 1398 1399 set_reclaim_mode(priority, sc, false); 1400 lru_add_drain(); 1401 spin_lock_irq(&zone->lru_lock); 1402 1403 if (scanning_global_lru(sc)) { 1404 nr_taken = isolate_pages_global(nr_to_scan, 1405 &page_list, &nr_scanned, sc->order, 1406 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1407 ISOLATE_BOTH : ISOLATE_INACTIVE, 1408 zone, 0, file); 1409 zone->pages_scanned += nr_scanned; 1410 if (current_is_kswapd()) 1411 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1412 nr_scanned); 1413 else 1414 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1415 nr_scanned); 1416 } else { 1417 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1418 &page_list, &nr_scanned, sc->order, 1419 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1420 ISOLATE_BOTH : ISOLATE_INACTIVE, 1421 zone, sc->mem_cgroup, 1422 0, file); 1423 /* 1424 * mem_cgroup_isolate_pages() keeps track of 1425 * scanned pages on its own. 1426 */ 1427 } 1428 1429 if (nr_taken == 0) { 1430 spin_unlock_irq(&zone->lru_lock); 1431 return 0; 1432 } 1433 1434 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1435 1436 spin_unlock_irq(&zone->lru_lock); 1437 1438 nr_reclaimed = shrink_page_list(&page_list, zone, sc); 1439 1440 /* Check if we should syncronously wait for writeback */ 1441 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1442 set_reclaim_mode(priority, sc, true); 1443 nr_reclaimed += shrink_page_list(&page_list, zone, sc); 1444 } 1445 1446 local_irq_disable(); 1447 if (current_is_kswapd()) 1448 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1449 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1450 1451 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1452 1453 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1454 zone_idx(zone), 1455 nr_scanned, nr_reclaimed, 1456 priority, 1457 trace_shrink_flags(file, sc->reclaim_mode)); 1458 return nr_reclaimed; 1459} 1460 1461/* 1462 * This moves pages from the active list to the inactive list. 1463 * 1464 * We move them the other way if the page is referenced by one or more 1465 * processes, from rmap. 1466 * 1467 * If the pages are mostly unmapped, the processing is fast and it is 1468 * appropriate to hold zone->lru_lock across the whole operation. But if 1469 * the pages are mapped, the processing is slow (page_referenced()) so we 1470 * should drop zone->lru_lock around each page. It's impossible to balance 1471 * this, so instead we remove the pages from the LRU while processing them. 1472 * It is safe to rely on PG_active against the non-LRU pages in here because 1473 * nobody will play with that bit on a non-LRU page. 1474 * 1475 * The downside is that we have to touch page->_count against each page. 1476 * But we had to alter page->flags anyway. 1477 */ 1478 1479static void move_active_pages_to_lru(struct zone *zone, 1480 struct list_head *list, 1481 enum lru_list lru) 1482{ 1483 unsigned long pgmoved = 0; 1484 struct pagevec pvec; 1485 struct page *page; 1486 1487 pagevec_init(&pvec, 1); 1488 1489 while (!list_empty(list)) { 1490 page = lru_to_page(list); 1491 1492 VM_BUG_ON(PageLRU(page)); 1493 SetPageLRU(page); 1494 1495 list_move(&page->lru, &zone->lru[lru].list); 1496 mem_cgroup_add_lru_list(page, lru); 1497 pgmoved += hpage_nr_pages(page); 1498 1499 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1500 spin_unlock_irq(&zone->lru_lock); 1501 if (buffer_heads_over_limit) 1502 pagevec_strip(&pvec); 1503 __pagevec_release(&pvec); 1504 spin_lock_irq(&zone->lru_lock); 1505 } 1506 } 1507 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1508 if (!is_active_lru(lru)) 1509 __count_vm_events(PGDEACTIVATE, pgmoved); 1510} 1511 1512static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1513 struct scan_control *sc, int priority, int file) 1514{ 1515 unsigned long nr_taken; 1516 unsigned long pgscanned; 1517 unsigned long vm_flags; 1518 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1519 LIST_HEAD(l_active); 1520 LIST_HEAD(l_inactive); 1521 struct page *page; 1522 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1523 unsigned long nr_rotated = 0; 1524 1525 lru_add_drain(); 1526 spin_lock_irq(&zone->lru_lock); 1527 if (scanning_global_lru(sc)) { 1528 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1529 &pgscanned, sc->order, 1530 ISOLATE_ACTIVE, zone, 1531 1, file); 1532 zone->pages_scanned += pgscanned; 1533 } else { 1534 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1535 &pgscanned, sc->order, 1536 ISOLATE_ACTIVE, zone, 1537 sc->mem_cgroup, 1, file); 1538 /* 1539 * mem_cgroup_isolate_pages() keeps track of 1540 * scanned pages on its own. 1541 */ 1542 } 1543 1544 reclaim_stat->recent_scanned[file] += nr_taken; 1545 1546 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1547 if (file) 1548 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1549 else 1550 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1551 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1552 spin_unlock_irq(&zone->lru_lock); 1553 1554 while (!list_empty(&l_hold)) { 1555 cond_resched(); 1556 page = lru_to_page(&l_hold); 1557 list_del(&page->lru); 1558 1559 if (unlikely(!page_evictable(page, NULL))) { 1560 putback_lru_page(page); 1561 continue; 1562 } 1563 1564 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1565 nr_rotated += hpage_nr_pages(page); 1566 /* 1567 * Identify referenced, file-backed active pages and 1568 * give them one more trip around the active list. So 1569 * that executable code get better chances to stay in 1570 * memory under moderate memory pressure. Anon pages 1571 * are not likely to be evicted by use-once streaming 1572 * IO, plus JVM can create lots of anon VM_EXEC pages, 1573 * so we ignore them here. 1574 */ 1575 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1576 list_add(&page->lru, &l_active); 1577 continue; 1578 } 1579 } 1580 1581 ClearPageActive(page); /* we are de-activating */ 1582 list_add(&page->lru, &l_inactive); 1583 } 1584 1585 /* 1586 * Move pages back to the lru list. 1587 */ 1588 spin_lock_irq(&zone->lru_lock); 1589 /* 1590 * Count referenced pages from currently used mappings as rotated, 1591 * even though only some of them are actually re-activated. This 1592 * helps balance scan pressure between file and anonymous pages in 1593 * get_scan_ratio. 1594 */ 1595 reclaim_stat->recent_rotated[file] += nr_rotated; 1596 1597 move_active_pages_to_lru(zone, &l_active, 1598 LRU_ACTIVE + file * LRU_FILE); 1599 move_active_pages_to_lru(zone, &l_inactive, 1600 LRU_BASE + file * LRU_FILE); 1601 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1602 spin_unlock_irq(&zone->lru_lock); 1603} 1604 1605#ifdef CONFIG_SWAP 1606static int inactive_anon_is_low_global(struct zone *zone) 1607{ 1608 unsigned long active, inactive; 1609 1610 active = zone_page_state(zone, NR_ACTIVE_ANON); 1611 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1612 1613 if (inactive * zone->inactive_ratio < active) 1614 return 1; 1615 1616 return 0; 1617} 1618 1619/** 1620 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1621 * @zone: zone to check 1622 * @sc: scan control of this context 1623 * 1624 * Returns true if the zone does not have enough inactive anon pages, 1625 * meaning some active anon pages need to be deactivated. 1626 */ 1627static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1628{ 1629 int low; 1630 1631 /* 1632 * If we don't have swap space, anonymous page deactivation 1633 * is pointless. 1634 */ 1635 if (!total_swap_pages) 1636 return 0; 1637 1638 if (scanning_global_lru(sc)) 1639 low = inactive_anon_is_low_global(zone); 1640 else 1641 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1642 return low; 1643} 1644#else 1645static inline int inactive_anon_is_low(struct zone *zone, 1646 struct scan_control *sc) 1647{ 1648 return 0; 1649} 1650#endif 1651 1652static int inactive_file_is_low_global(struct zone *zone) 1653{ 1654 unsigned long active, inactive; 1655 1656 active = zone_page_state(zone, NR_ACTIVE_FILE); 1657 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1658 1659 return (active > inactive); 1660} 1661 1662/** 1663 * inactive_file_is_low - check if file pages need to be deactivated 1664 * @zone: zone to check 1665 * @sc: scan control of this context 1666 * 1667 * When the system is doing streaming IO, memory pressure here 1668 * ensures that active file pages get deactivated, until more 1669 * than half of the file pages are on the inactive list. 1670 * 1671 * Once we get to that situation, protect the system's working 1672 * set from being evicted by disabling active file page aging. 1673 * 1674 * This uses a different ratio than the anonymous pages, because 1675 * the page cache uses a use-once replacement algorithm. 1676 */ 1677static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1678{ 1679 int low; 1680 1681 if (scanning_global_lru(sc)) 1682 low = inactive_file_is_low_global(zone); 1683 else 1684 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1685 return low; 1686} 1687 1688static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1689 int file) 1690{ 1691 if (file) 1692 return inactive_file_is_low(zone, sc); 1693 else 1694 return inactive_anon_is_low(zone, sc); 1695} 1696 1697static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1698 struct zone *zone, struct scan_control *sc, int priority) 1699{ 1700 int file = is_file_lru(lru); 1701 1702 if (is_active_lru(lru)) { 1703 if (inactive_list_is_low(zone, sc, file)) 1704 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1705 return 0; 1706 } 1707 1708 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1709} 1710 1711/* 1712 * Smallish @nr_to_scan's are deposited in @nr_saved_scan, 1713 * until we collected @swap_cluster_max pages to scan. 1714 */ 1715static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, 1716 unsigned long *nr_saved_scan) 1717{ 1718 unsigned long nr; 1719 1720 *nr_saved_scan += nr_to_scan; 1721 nr = *nr_saved_scan; 1722 1723 if (nr >= SWAP_CLUSTER_MAX) 1724 *nr_saved_scan = 0; 1725 else 1726 nr = 0; 1727 1728 return nr; 1729} 1730 1731/* 1732 * Determine how aggressively the anon and file LRU lists should be 1733 * scanned. The relative value of each set of LRU lists is determined 1734 * by looking at the fraction of the pages scanned we did rotate back 1735 * onto the active list instead of evict. 1736 * 1737 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1738 */ 1739static void get_scan_count(struct zone *zone, struct scan_control *sc, 1740 unsigned long *nr, int priority) 1741{ 1742 unsigned long anon, file, free; 1743 unsigned long anon_prio, file_prio; 1744 unsigned long ap, fp; 1745 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1746 u64 fraction[2], denominator; 1747 enum lru_list l; 1748 int noswap = 0; 1749 1750 /* If we have no swap space, do not bother scanning anon pages. */ 1751 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1752 noswap = 1; 1753 fraction[0] = 0; 1754 fraction[1] = 1; 1755 denominator = 1; 1756 goto out; 1757 } 1758 1759 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1760 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1761 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1762 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1763 1764 if (scanning_global_lru(sc)) { 1765 free = zone_page_state(zone, NR_FREE_PAGES); 1766 /* If we have very few page cache pages, 1767 force-scan anon pages. */ 1768 if (unlikely(file + free <= high_wmark_pages(zone))) { 1769 fraction[0] = 1; 1770 fraction[1] = 0; 1771 denominator = 1; 1772 goto out; 1773 } 1774 } 1775 1776 /* 1777 * With swappiness at 100, anonymous and file have the same priority. 1778 * This scanning priority is essentially the inverse of IO cost. 1779 */ 1780 anon_prio = sc->swappiness; 1781 file_prio = 200 - sc->swappiness; 1782 1783 /* 1784 * OK, so we have swap space and a fair amount of page cache 1785 * pages. We use the recently rotated / recently scanned 1786 * ratios to determine how valuable each cache is. 1787 * 1788 * Because workloads change over time (and to avoid overflow) 1789 * we keep these statistics as a floating average, which ends 1790 * up weighing recent references more than old ones. 1791 * 1792 * anon in [0], file in [1] 1793 */ 1794 spin_lock_irq(&zone->lru_lock); 1795 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1796 reclaim_stat->recent_scanned[0] /= 2; 1797 reclaim_stat->recent_rotated[0] /= 2; 1798 } 1799 1800 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1801 reclaim_stat->recent_scanned[1] /= 2; 1802 reclaim_stat->recent_rotated[1] /= 2; 1803 } 1804 1805 /* 1806 * The amount of pressure on anon vs file pages is inversely 1807 * proportional to the fraction of recently scanned pages on 1808 * each list that were recently referenced and in active use. 1809 */ 1810 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1811 ap /= reclaim_stat->recent_rotated[0] + 1; 1812 1813 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1814 fp /= reclaim_stat->recent_rotated[1] + 1; 1815 spin_unlock_irq(&zone->lru_lock); 1816 1817 fraction[0] = ap; 1818 fraction[1] = fp; 1819 denominator = ap + fp + 1; 1820out: 1821 for_each_evictable_lru(l) { 1822 int file = is_file_lru(l); 1823 unsigned long scan; 1824 1825 scan = zone_nr_lru_pages(zone, sc, l); 1826 if (priority || noswap) { 1827 scan >>= priority; 1828 scan = div64_u64(scan * fraction[file], denominator); 1829 } 1830 nr[l] = nr_scan_try_batch(scan, 1831 &reclaim_stat->nr_saved_scan[l]); 1832 } 1833} 1834 1835/* 1836 * Reclaim/compaction depends on a number of pages being freed. To avoid 1837 * disruption to the system, a small number of order-0 pages continue to be 1838 * rotated and reclaimed in the normal fashion. However, by the time we get 1839 * back to the allocator and call try_to_compact_zone(), we ensure that 1840 * there are enough free pages for it to be likely successful 1841 */ 1842static inline bool should_continue_reclaim(struct zone *zone, 1843 unsigned long nr_reclaimed, 1844 unsigned long nr_scanned, 1845 struct scan_control *sc) 1846{ 1847 unsigned long pages_for_compaction; 1848 unsigned long inactive_lru_pages; 1849 1850 /* If not in reclaim/compaction mode, stop */ 1851 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1852 return false; 1853 1854 /* Consider stopping depending on scan and reclaim activity */ 1855 if (sc->gfp_mask & __GFP_REPEAT) { 1856 /* 1857 * For __GFP_REPEAT allocations, stop reclaiming if the 1858 * full LRU list has been scanned and we are still failing 1859 * to reclaim pages. This full LRU scan is potentially 1860 * expensive but a __GFP_REPEAT caller really wants to succeed 1861 */ 1862 if (!nr_reclaimed && !nr_scanned) 1863 return false; 1864 } else { 1865 /* 1866 * For non-__GFP_REPEAT allocations which can presumably 1867 * fail without consequence, stop if we failed to reclaim 1868 * any pages from the last SWAP_CLUSTER_MAX number of 1869 * pages that were scanned. This will return to the 1870 * caller faster at the risk reclaim/compaction and 1871 * the resulting allocation attempt fails 1872 */ 1873 if (!nr_reclaimed) 1874 return false; 1875 } 1876 1877 /* 1878 * If we have not reclaimed enough pages for compaction and the 1879 * inactive lists are large enough, continue reclaiming 1880 */ 1881 pages_for_compaction = (2UL << sc->order); 1882 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 1883 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1884 if (sc->nr_reclaimed < pages_for_compaction && 1885 inactive_lru_pages > pages_for_compaction) 1886 return true; 1887 1888 /* If compaction would go ahead or the allocation would succeed, stop */ 1889 switch (compaction_suitable(zone, sc->order)) { 1890 case COMPACT_PARTIAL: 1891 case COMPACT_CONTINUE: 1892 return false; 1893 default: 1894 return true; 1895 } 1896} 1897 1898/* 1899 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1900 */ 1901static void shrink_zone(int priority, struct zone *zone, 1902 struct scan_control *sc) 1903{ 1904 unsigned long nr[NR_LRU_LISTS]; 1905 unsigned long nr_to_scan; 1906 enum lru_list l; 1907 unsigned long nr_reclaimed, nr_scanned; 1908 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1909 1910restart: 1911 nr_reclaimed = 0; 1912 nr_scanned = sc->nr_scanned; 1913 get_scan_count(zone, sc, nr, priority); 1914 1915 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1916 nr[LRU_INACTIVE_FILE]) { 1917 for_each_evictable_lru(l) { 1918 if (nr[l]) { 1919 nr_to_scan = min_t(unsigned long, 1920 nr[l], SWAP_CLUSTER_MAX); 1921 nr[l] -= nr_to_scan; 1922 1923 nr_reclaimed += shrink_list(l, nr_to_scan, 1924 zone, sc, priority); 1925 } 1926 } 1927 /* 1928 * On large memory systems, scan >> priority can become 1929 * really large. This is fine for the starting priority; 1930 * we want to put equal scanning pressure on each zone. 1931 * However, if the VM has a harder time of freeing pages, 1932 * with multiple processes reclaiming pages, the total 1933 * freeing target can get unreasonably large. 1934 */ 1935 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 1936 break; 1937 } 1938 sc->nr_reclaimed += nr_reclaimed; 1939 1940 /* 1941 * Even if we did not try to evict anon pages at all, we want to 1942 * rebalance the anon lru active/inactive ratio. 1943 */ 1944 if (inactive_anon_is_low(zone, sc)) 1945 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1946 1947 /* reclaim/compaction might need reclaim to continue */ 1948 if (should_continue_reclaim(zone, nr_reclaimed, 1949 sc->nr_scanned - nr_scanned, sc)) 1950 goto restart; 1951 1952 throttle_vm_writeout(sc->gfp_mask); 1953} 1954 1955/* 1956 * This is the direct reclaim path, for page-allocating processes. We only 1957 * try to reclaim pages from zones which will satisfy the caller's allocation 1958 * request. 1959 * 1960 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 1961 * Because: 1962 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1963 * allocation or 1964 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 1965 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 1966 * zone defense algorithm. 1967 * 1968 * If a zone is deemed to be full of pinned pages then just give it a light 1969 * scan then give up on it. 1970 */ 1971static void shrink_zones(int priority, struct zonelist *zonelist, 1972 struct scan_control *sc) 1973{ 1974 struct zoneref *z; 1975 struct zone *zone; 1976 1977 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1978 gfp_zone(sc->gfp_mask), sc->nodemask) { 1979 if (!populated_zone(zone)) 1980 continue; 1981 /* 1982 * Take care memory controller reclaiming has small influence 1983 * to global LRU. 1984 */ 1985 if (scanning_global_lru(sc)) { 1986 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1987 continue; 1988 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1989 continue; /* Let kswapd poll it */ 1990 } 1991 1992 shrink_zone(priority, zone, sc); 1993 } 1994} 1995 1996static bool zone_reclaimable(struct zone *zone) 1997{ 1998 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 1999} 2000 2001/* All zones in zonelist are unreclaimable? */ 2002static bool all_unreclaimable(struct zonelist *zonelist, 2003 struct scan_control *sc) 2004{ 2005 struct zoneref *z; 2006 struct zone *zone; 2007 2008 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2009 gfp_zone(sc->gfp_mask), sc->nodemask) { 2010 if (!populated_zone(zone)) 2011 continue; 2012 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2013 continue; 2014 if (!zone->all_unreclaimable) 2015 return false; 2016 } 2017 2018 return true; 2019} 2020 2021/* 2022 * This is the main entry point to direct page reclaim. 2023 * 2024 * If a full scan of the inactive list fails to free enough memory then we 2025 * are "out of memory" and something needs to be killed. 2026 * 2027 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2028 * high - the zone may be full of dirty or under-writeback pages, which this 2029 * caller can't do much about. We kick the writeback threads and take explicit 2030 * naps in the hope that some of these pages can be written. But if the 2031 * allocating task holds filesystem locks which prevent writeout this might not 2032 * work, and the allocation attempt will fail. 2033 * 2034 * returns: 0, if no pages reclaimed 2035 * else, the number of pages reclaimed 2036 */ 2037static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2038 struct scan_control *sc) 2039{ 2040 int priority; 2041 unsigned long total_scanned = 0; 2042 struct reclaim_state *reclaim_state = current->reclaim_state; 2043 struct zoneref *z; 2044 struct zone *zone; 2045 unsigned long writeback_threshold; 2046 2047 get_mems_allowed(); 2048 delayacct_freepages_start(); 2049 2050 if (scanning_global_lru(sc)) 2051 count_vm_event(ALLOCSTALL); 2052 2053 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2054 sc->nr_scanned = 0; 2055 if (!priority) 2056 disable_swap_token(); 2057 shrink_zones(priority, zonelist, sc); 2058 /* 2059 * Don't shrink slabs when reclaiming memory from 2060 * over limit cgroups 2061 */ 2062 if (scanning_global_lru(sc)) { 2063 unsigned long lru_pages = 0; 2064 for_each_zone_zonelist(zone, z, zonelist, 2065 gfp_zone(sc->gfp_mask)) { 2066 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2067 continue; 2068 2069 lru_pages += zone_reclaimable_pages(zone); 2070 } 2071 2072 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); 2073 if (reclaim_state) { 2074 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2075 reclaim_state->reclaimed_slab = 0; 2076 } 2077 } 2078 total_scanned += sc->nr_scanned; 2079 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2080 goto out; 2081 2082 /* 2083 * Try to write back as many pages as we just scanned. This 2084 * tends to cause slow streaming writers to write data to the 2085 * disk smoothly, at the dirtying rate, which is nice. But 2086 * that's undesirable in laptop mode, where we *want* lumpy 2087 * writeout. So in laptop mode, write out the whole world. 2088 */ 2089 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2090 if (total_scanned > writeback_threshold) { 2091 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2092 sc->may_writepage = 1; 2093 } 2094 2095 /* Take a nap, wait for some writeback to complete */ 2096 if (!sc->hibernation_mode && sc->nr_scanned && 2097 priority < DEF_PRIORITY - 2) { 2098 struct zone *preferred_zone; 2099 2100 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2101 &cpuset_current_mems_allowed, 2102 &preferred_zone); 2103 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2104 } 2105 } 2106 2107out: 2108 delayacct_freepages_end(); 2109 put_mems_allowed(); 2110 2111 if (sc->nr_reclaimed) 2112 return sc->nr_reclaimed; 2113 2114 /* 2115 * As hibernation is going on, kswapd is freezed so that it can't mark 2116 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2117 * check. 2118 */ 2119 if (oom_killer_disabled) 2120 return 0; 2121 2122 /* top priority shrink_zones still had more to do? don't OOM, then */ 2123 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2124 return 1; 2125 2126 return 0; 2127} 2128 2129unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2130 gfp_t gfp_mask, nodemask_t *nodemask) 2131{ 2132 unsigned long nr_reclaimed; 2133 struct scan_control sc = { 2134 .gfp_mask = gfp_mask, 2135 .may_writepage = !laptop_mode, 2136 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2137 .may_unmap = 1, 2138 .may_swap = 1, 2139 .swappiness = vm_swappiness, 2140 .order = order, 2141 .mem_cgroup = NULL, 2142 .nodemask = nodemask, 2143 }; 2144 2145 trace_mm_vmscan_direct_reclaim_begin(order, 2146 sc.may_writepage, 2147 gfp_mask); 2148 2149 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2150 2151 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2152 2153 return nr_reclaimed; 2154} 2155 2156#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2157 2158unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2159 gfp_t gfp_mask, bool noswap, 2160 unsigned int swappiness, 2161 struct zone *zone) 2162{ 2163 struct scan_control sc = { 2164 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2165 .may_writepage = !laptop_mode, 2166 .may_unmap = 1, 2167 .may_swap = !noswap, 2168 .swappiness = swappiness, 2169 .order = 0, 2170 .mem_cgroup = mem, 2171 }; 2172 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2173 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2174 2175 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2176 sc.may_writepage, 2177 sc.gfp_mask); 2178 2179 /* 2180 * NOTE: Although we can get the priority field, using it 2181 * here is not a good idea, since it limits the pages we can scan. 2182 * if we don't reclaim here, the shrink_zone from balance_pgdat 2183 * will pick up pages from other mem cgroup's as well. We hack 2184 * the priority and make it zero. 2185 */ 2186 shrink_zone(0, zone, &sc); 2187 2188 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2189 2190 return sc.nr_reclaimed; 2191} 2192 2193unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2194 gfp_t gfp_mask, 2195 bool noswap, 2196 unsigned int swappiness) 2197{ 2198 struct zonelist *zonelist; 2199 unsigned long nr_reclaimed; 2200 struct scan_control sc = { 2201 .may_writepage = !laptop_mode, 2202 .may_unmap = 1, 2203 .may_swap = !noswap, 2204 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2205 .swappiness = swappiness, 2206 .order = 0, 2207 .mem_cgroup = mem_cont, 2208 .nodemask = NULL, /* we don't care the placement */ 2209 }; 2210 2211 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2212 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2213 zonelist = NODE_DATA(numa_node_id())->node_zonelists; 2214 2215 trace_mm_vmscan_memcg_reclaim_begin(0, 2216 sc.may_writepage, 2217 sc.gfp_mask); 2218 2219 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2220 2221 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2222 2223 return nr_reclaimed; 2224} 2225#endif 2226 2227/* 2228 * pgdat_balanced is used when checking if a node is balanced for high-order 2229 * allocations. Only zones that meet watermarks and are in a zone allowed 2230 * by the callers classzone_idx are added to balanced_pages. The total of 2231 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2232 * for the node to be considered balanced. Forcing all zones to be balanced 2233 * for high orders can cause excessive reclaim when there are imbalanced zones. 2234 * The choice of 25% is due to 2235 * o a 16M DMA zone that is balanced will not balance a zone on any 2236 * reasonable sized machine 2237 * o On all other machines, the top zone must be at least a reasonable 2238 * percentage of the middle zones. For example, on 32-bit x86, highmem 2239 * would need to be at least 256M for it to be balance a whole node. 2240 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2241 * to balance a node on its own. These seemed like reasonable ratios. 2242 */ 2243static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2244 int classzone_idx) 2245{ 2246 unsigned long present_pages = 0; 2247 int i; 2248 2249 for (i = 0; i <= classzone_idx; i++) 2250 present_pages += pgdat->node_zones[i].present_pages; 2251 2252 return balanced_pages > (present_pages >> 2); 2253} 2254 2255/* is kswapd sleeping prematurely? */ 2256static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2257 int classzone_idx) 2258{ 2259 int i; 2260 unsigned long balanced = 0; 2261 bool all_zones_ok = true; 2262 2263 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2264 if (remaining) 2265 return true; 2266 2267 /* Check the watermark levels */ 2268 for (i = 0; i < pgdat->nr_zones; i++) { 2269 struct zone *zone = pgdat->node_zones + i; 2270 2271 if (!populated_zone(zone)) 2272 continue; 2273 2274 /* 2275 * balance_pgdat() skips over all_unreclaimable after 2276 * DEF_PRIORITY. Effectively, it considers them balanced so 2277 * they must be considered balanced here as well if kswapd 2278 * is to sleep 2279 */ 2280 if (zone->all_unreclaimable) { 2281 balanced += zone->present_pages; 2282 continue; 2283 } 2284 2285 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2286 classzone_idx, 0)) 2287 all_zones_ok = false; 2288 else 2289 balanced += zone->present_pages; 2290 } 2291 2292 /* 2293 * For high-order requests, the balanced zones must contain at least 2294 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2295 * must be balanced 2296 */ 2297 if (order) 2298 return !pgdat_balanced(pgdat, balanced, classzone_idx); 2299 else 2300 return !all_zones_ok; 2301} 2302 2303/* 2304 * For kswapd, balance_pgdat() will work across all this node's zones until 2305 * they are all at high_wmark_pages(zone). 2306 * 2307 * Returns the final order kswapd was reclaiming at 2308 * 2309 * There is special handling here for zones which are full of pinned pages. 2310 * This can happen if the pages are all mlocked, or if they are all used by 2311 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2312 * What we do is to detect the case where all pages in the zone have been 2313 * scanned twice and there has been zero successful reclaim. Mark the zone as 2314 * dead and from now on, only perform a short scan. Basically we're polling 2315 * the zone for when the problem goes away. 2316 * 2317 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2318 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2319 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2320 * lower zones regardless of the number of free pages in the lower zones. This 2321 * interoperates with the page allocator fallback scheme to ensure that aging 2322 * of pages is balanced across the zones. 2323 */ 2324static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2325 int *classzone_idx) 2326{ 2327 int all_zones_ok; 2328 unsigned long balanced; 2329 int priority; 2330 int i; 2331 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2332 unsigned long total_scanned; 2333 struct reclaim_state *reclaim_state = current->reclaim_state; 2334 struct scan_control sc = { 2335 .gfp_mask = GFP_KERNEL, 2336 .may_unmap = 1, 2337 .may_swap = 1, 2338 /* 2339 * kswapd doesn't want to be bailed out while reclaim. because 2340 * we want to put equal scanning pressure on each zone. 2341 */ 2342 .nr_to_reclaim = ULONG_MAX, 2343 .swappiness = vm_swappiness, 2344 .order = order, 2345 .mem_cgroup = NULL, 2346 }; 2347loop_again: 2348 total_scanned = 0; 2349 sc.nr_reclaimed = 0; 2350 sc.may_writepage = !laptop_mode; 2351 count_vm_event(PAGEOUTRUN); 2352 2353 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2354 unsigned long lru_pages = 0; 2355 int has_under_min_watermark_zone = 0; 2356 2357 /* The swap token gets in the way of swapout... */ 2358 if (!priority) 2359 disable_swap_token(); 2360 2361 all_zones_ok = 1; 2362 balanced = 0; 2363 2364 /* 2365 * Scan in the highmem->dma direction for the highest 2366 * zone which needs scanning 2367 */ 2368 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2369 struct zone *zone = pgdat->node_zones + i; 2370 2371 if (!populated_zone(zone)) 2372 continue; 2373 2374 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2375 continue; 2376 2377 /* 2378 * Do some background aging of the anon list, to give 2379 * pages a chance to be referenced before reclaiming. 2380 */ 2381 if (inactive_anon_is_low(zone, &sc)) 2382 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2383 &sc, priority, 0); 2384 2385 if (!zone_watermark_ok_safe(zone, order, 2386 high_wmark_pages(zone), 0, 0)) { 2387 end_zone = i; 2388 *classzone_idx = i; 2389 break; 2390 } 2391 } 2392 if (i < 0) 2393 goto out; 2394 2395 for (i = 0; i <= end_zone; i++) { 2396 struct zone *zone = pgdat->node_zones + i; 2397 2398 lru_pages += zone_reclaimable_pages(zone); 2399 } 2400 2401 /* 2402 * Now scan the zone in the dma->highmem direction, stopping 2403 * at the last zone which needs scanning. 2404 * 2405 * We do this because the page allocator works in the opposite 2406 * direction. This prevents the page allocator from allocating 2407 * pages behind kswapd's direction of progress, which would 2408 * cause too much scanning of the lower zones. 2409 */ 2410 for (i = 0; i <= end_zone; i++) { 2411 struct zone *zone = pgdat->node_zones + i; 2412 int nr_slab; 2413 unsigned long balance_gap; 2414 2415 if (!populated_zone(zone)) 2416 continue; 2417 2418 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2419 continue; 2420 2421 sc.nr_scanned = 0; 2422 2423 /* 2424 * Call soft limit reclaim before calling shrink_zone. 2425 * For now we ignore the return value 2426 */ 2427 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); 2428 2429 /* 2430 * We put equal pressure on every zone, unless 2431 * one zone has way too many pages free 2432 * already. The "too many pages" is defined 2433 * as the high wmark plus a "gap" where the 2434 * gap is either the low watermark or 1% 2435 * of the zone, whichever is smaller. 2436 */ 2437 balance_gap = min(low_wmark_pages(zone), 2438 (zone->present_pages + 2439 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2440 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2441 if (!zone_watermark_ok_safe(zone, order, 2442 high_wmark_pages(zone) + balance_gap, 2443 end_zone, 0)) 2444 shrink_zone(priority, zone, &sc); 2445 reclaim_state->reclaimed_slab = 0; 2446 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 2447 lru_pages); 2448 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2449 total_scanned += sc.nr_scanned; 2450 2451 if (zone->all_unreclaimable) 2452 continue; 2453 if (nr_slab == 0 && 2454 !zone_reclaimable(zone)) 2455 zone->all_unreclaimable = 1; 2456 /* 2457 * If we've done a decent amount of scanning and 2458 * the reclaim ratio is low, start doing writepage 2459 * even in laptop mode 2460 */ 2461 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2462 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2463 sc.may_writepage = 1; 2464 2465 if (!zone_watermark_ok_safe(zone, order, 2466 high_wmark_pages(zone), end_zone, 0)) { 2467 all_zones_ok = 0; 2468 /* 2469 * We are still under min water mark. This 2470 * means that we have a GFP_ATOMIC allocation 2471 * failure risk. Hurry up! 2472 */ 2473 if (!zone_watermark_ok_safe(zone, order, 2474 min_wmark_pages(zone), end_zone, 0)) 2475 has_under_min_watermark_zone = 1; 2476 } else { 2477 /* 2478 * If a zone reaches its high watermark, 2479 * consider it to be no longer congested. It's 2480 * possible there are dirty pages backed by 2481 * congested BDIs but as pressure is relieved, 2482 * spectulatively avoid congestion waits 2483 */ 2484 zone_clear_flag(zone, ZONE_CONGESTED); 2485 if (i <= *classzone_idx) 2486 balanced += zone->present_pages; 2487 } 2488 2489 } 2490 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2491 break; /* kswapd: all done */ 2492 /* 2493 * OK, kswapd is getting into trouble. Take a nap, then take 2494 * another pass across the zones. 2495 */ 2496 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2497 if (has_under_min_watermark_zone) 2498 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2499 else 2500 congestion_wait(BLK_RW_ASYNC, HZ/10); 2501 } 2502 2503 /* 2504 * We do this so kswapd doesn't build up large priorities for 2505 * example when it is freeing in parallel with allocators. It 2506 * matches the direct reclaim path behaviour in terms of impact 2507 * on zone->*_priority. 2508 */ 2509 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2510 break; 2511 } 2512out: 2513 2514 /* 2515 * order-0: All zones must meet high watermark for a balanced node 2516 * high-order: Balanced zones must make up at least 25% of the node 2517 * for the node to be balanced 2518 */ 2519 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2520 cond_resched(); 2521 2522 try_to_freeze(); 2523 2524 /* 2525 * Fragmentation may mean that the system cannot be 2526 * rebalanced for high-order allocations in all zones. 2527 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2528 * it means the zones have been fully scanned and are still 2529 * not balanced. For high-order allocations, there is 2530 * little point trying all over again as kswapd may 2531 * infinite loop. 2532 * 2533 * Instead, recheck all watermarks at order-0 as they 2534 * are the most important. If watermarks are ok, kswapd will go 2535 * back to sleep. High-order users can still perform direct 2536 * reclaim if they wish. 2537 */ 2538 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2539 order = sc.order = 0; 2540 2541 goto loop_again; 2542 } 2543 2544 /* 2545 * If kswapd was reclaiming at a higher order, it has the option of 2546 * sleeping without all zones being balanced. Before it does, it must 2547 * ensure that the watermarks for order-0 on *all* zones are met and 2548 * that the congestion flags are cleared. The congestion flag must 2549 * be cleared as kswapd is the only mechanism that clears the flag 2550 * and it is potentially going to sleep here. 2551 */ 2552 if (order) { 2553 for (i = 0; i <= end_zone; i++) { 2554 struct zone *zone = pgdat->node_zones + i; 2555 2556 if (!populated_zone(zone)) 2557 continue; 2558 2559 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2560 continue; 2561 2562 /* Confirm the zone is balanced for order-0 */ 2563 if (!zone_watermark_ok(zone, 0, 2564 high_wmark_pages(zone), 0, 0)) { 2565 order = sc.order = 0; 2566 goto loop_again; 2567 } 2568 2569 /* If balanced, clear the congested flag */ 2570 zone_clear_flag(zone, ZONE_CONGESTED); 2571 } 2572 } 2573 2574 /* 2575 * Return the order we were reclaiming at so sleeping_prematurely() 2576 * makes a decision on the order we were last reclaiming at. However, 2577 * if another caller entered the allocator slow path while kswapd 2578 * was awake, order will remain at the higher level 2579 */ 2580 *classzone_idx = end_zone; 2581 return order; 2582} 2583 2584static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2585{ 2586 long remaining = 0; 2587 DEFINE_WAIT(wait); 2588 2589 if (freezing(current) || kthread_should_stop()) 2590 return; 2591 2592 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2593 2594 /* Try to sleep for a short interval */ 2595 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2596 remaining = schedule_timeout(HZ/10); 2597 finish_wait(&pgdat->kswapd_wait, &wait); 2598 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2599 } 2600 2601 /* 2602 * After a short sleep, check if it was a premature sleep. If not, then 2603 * go fully to sleep until explicitly woken up. 2604 */ 2605 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2606 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2607 2608 /* 2609 * vmstat counters are not perfectly accurate and the estimated 2610 * value for counters such as NR_FREE_PAGES can deviate from the 2611 * true value by nr_online_cpus * threshold. To avoid the zone 2612 * watermarks being breached while under pressure, we reduce the 2613 * per-cpu vmstat threshold while kswapd is awake and restore 2614 * them before going back to sleep. 2615 */ 2616 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2617 schedule(); 2618 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2619 } else { 2620 if (remaining) 2621 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2622 else 2623 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2624 } 2625 finish_wait(&pgdat->kswapd_wait, &wait); 2626} 2627 2628/* 2629 * The background pageout daemon, started as a kernel thread 2630 * from the init process. 2631 * 2632 * This basically trickles out pages so that we have _some_ 2633 * free memory available even if there is no other activity 2634 * that frees anything up. This is needed for things like routing 2635 * etc, where we otherwise might have all activity going on in 2636 * asynchronous contexts that cannot page things out. 2637 * 2638 * If there are applications that are active memory-allocators 2639 * (most normal use), this basically shouldn't matter. 2640 */ 2641static int kswapd(void *p) 2642{ 2643 unsigned long order; 2644 int classzone_idx; 2645 pg_data_t *pgdat = (pg_data_t*)p; 2646 struct task_struct *tsk = current; 2647 2648 struct reclaim_state reclaim_state = { 2649 .reclaimed_slab = 0, 2650 }; 2651 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2652 2653 lockdep_set_current_reclaim_state(GFP_KERNEL); 2654 2655 if (!cpumask_empty(cpumask)) 2656 set_cpus_allowed_ptr(tsk, cpumask); 2657 current->reclaim_state = &reclaim_state; 2658 2659 /* 2660 * Tell the memory management that we're a "memory allocator", 2661 * and that if we need more memory we should get access to it 2662 * regardless (see "__alloc_pages()"). "kswapd" should 2663 * never get caught in the normal page freeing logic. 2664 * 2665 * (Kswapd normally doesn't need memory anyway, but sometimes 2666 * you need a small amount of memory in order to be able to 2667 * page out something else, and this flag essentially protects 2668 * us from recursively trying to free more memory as we're 2669 * trying to free the first piece of memory in the first place). 2670 */ 2671 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2672 set_freezable(); 2673 2674 order = 0; 2675 classzone_idx = MAX_NR_ZONES - 1; 2676 for ( ; ; ) { 2677 unsigned long new_order; 2678 int new_classzone_idx; 2679 int ret; 2680 2681 new_order = pgdat->kswapd_max_order; 2682 new_classzone_idx = pgdat->classzone_idx; 2683 pgdat->kswapd_max_order = 0; 2684 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2685 if (order < new_order || classzone_idx > new_classzone_idx) { 2686 /* 2687 * Don't sleep if someone wants a larger 'order' 2688 * allocation or has tigher zone constraints 2689 */ 2690 order = new_order; 2691 classzone_idx = new_classzone_idx; 2692 } else { 2693 kswapd_try_to_sleep(pgdat, order, classzone_idx); 2694 order = pgdat->kswapd_max_order; 2695 classzone_idx = pgdat->classzone_idx; 2696 pgdat->kswapd_max_order = 0; 2697 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2698 } 2699 2700 ret = try_to_freeze(); 2701 if (kthread_should_stop()) 2702 break; 2703 2704 /* 2705 * We can speed up thawing tasks if we don't call balance_pgdat 2706 * after returning from the refrigerator 2707 */ 2708 if (!ret) { 2709 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2710 order = balance_pgdat(pgdat, order, &classzone_idx); 2711 } 2712 } 2713 return 0; 2714} 2715 2716/* 2717 * A zone is low on free memory, so wake its kswapd task to service it. 2718 */ 2719void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2720{ 2721 pg_data_t *pgdat; 2722 2723 if (!populated_zone(zone)) 2724 return; 2725 2726 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2727 return; 2728 pgdat = zone->zone_pgdat; 2729 if (pgdat->kswapd_max_order < order) { 2730 pgdat->kswapd_max_order = order; 2731 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2732 } 2733 if (!waitqueue_active(&pgdat->kswapd_wait)) 2734 return; 2735 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2736 return; 2737 2738 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2739 wake_up_interruptible(&pgdat->kswapd_wait); 2740} 2741 2742/* 2743 * The reclaimable count would be mostly accurate. 2744 * The less reclaimable pages may be 2745 * - mlocked pages, which will be moved to unevictable list when encountered 2746 * - mapped pages, which may require several travels to be reclaimed 2747 * - dirty pages, which is not "instantly" reclaimable 2748 */ 2749unsigned long global_reclaimable_pages(void) 2750{ 2751 int nr; 2752 2753 nr = global_page_state(NR_ACTIVE_FILE) + 2754 global_page_state(NR_INACTIVE_FILE); 2755 2756 if (nr_swap_pages > 0) 2757 nr += global_page_state(NR_ACTIVE_ANON) + 2758 global_page_state(NR_INACTIVE_ANON); 2759 2760 return nr; 2761} 2762 2763unsigned long zone_reclaimable_pages(struct zone *zone) 2764{ 2765 int nr; 2766 2767 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2768 zone_page_state(zone, NR_INACTIVE_FILE); 2769 2770 if (nr_swap_pages > 0) 2771 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2772 zone_page_state(zone, NR_INACTIVE_ANON); 2773 2774 return nr; 2775} 2776 2777#ifdef CONFIG_HIBERNATION 2778/* 2779 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2780 * freed pages. 2781 * 2782 * Rather than trying to age LRUs the aim is to preserve the overall 2783 * LRU order by reclaiming preferentially 2784 * inactive > active > active referenced > active mapped 2785 */ 2786unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2787{ 2788 struct reclaim_state reclaim_state; 2789 struct scan_control sc = { 2790 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2791 .may_swap = 1, 2792 .may_unmap = 1, 2793 .may_writepage = 1, 2794 .nr_to_reclaim = nr_to_reclaim, 2795 .hibernation_mode = 1, 2796 .swappiness = vm_swappiness, 2797 .order = 0, 2798 }; 2799 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2800 struct task_struct *p = current; 2801 unsigned long nr_reclaimed; 2802 2803 p->flags |= PF_MEMALLOC; 2804 lockdep_set_current_reclaim_state(sc.gfp_mask); 2805 reclaim_state.reclaimed_slab = 0; 2806 p->reclaim_state = &reclaim_state; 2807 2808 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2809 2810 p->reclaim_state = NULL; 2811 lockdep_clear_current_reclaim_state(); 2812 p->flags &= ~PF_MEMALLOC; 2813 2814 return nr_reclaimed; 2815} 2816#endif /* CONFIG_HIBERNATION */ 2817 2818/* It's optimal to keep kswapds on the same CPUs as their memory, but 2819 not required for correctness. So if the last cpu in a node goes 2820 away, we get changed to run anywhere: as the first one comes back, 2821 restore their cpu bindings. */ 2822static int __devinit cpu_callback(struct notifier_block *nfb, 2823 unsigned long action, void *hcpu) 2824{ 2825 int nid; 2826 2827 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2828 for_each_node_state(nid, N_HIGH_MEMORY) { 2829 pg_data_t *pgdat = NODE_DATA(nid); 2830 const struct cpumask *mask; 2831 2832 mask = cpumask_of_node(pgdat->node_id); 2833 2834 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2835 /* One of our CPUs online: restore mask */ 2836 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2837 } 2838 } 2839 return NOTIFY_OK; 2840} 2841 2842/* 2843 * This kswapd start function will be called by init and node-hot-add. 2844 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2845 */ 2846int kswapd_run(int nid) 2847{ 2848 pg_data_t *pgdat = NODE_DATA(nid); 2849 int ret = 0; 2850 2851 if (pgdat->kswapd) 2852 return 0; 2853 2854 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2855 if (IS_ERR(pgdat->kswapd)) { 2856 /* failure at boot is fatal */ 2857 BUG_ON(system_state == SYSTEM_BOOTING); 2858 printk("Failed to start kswapd on node %d\n",nid); 2859 ret = -1; 2860 } 2861 return ret; 2862} 2863 2864/* 2865 * Called by memory hotplug when all memory in a node is offlined. 2866 */ 2867void kswapd_stop(int nid) 2868{ 2869 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2870 2871 if (kswapd) 2872 kthread_stop(kswapd); 2873} 2874 2875static int __init kswapd_init(void) 2876{ 2877 int nid; 2878 2879 swap_setup(); 2880 for_each_node_state(nid, N_HIGH_MEMORY) 2881 kswapd_run(nid); 2882 hotcpu_notifier(cpu_callback, 0); 2883 return 0; 2884} 2885 2886module_init(kswapd_init) 2887 2888#ifdef CONFIG_NUMA 2889/* 2890 * Zone reclaim mode 2891 * 2892 * If non-zero call zone_reclaim when the number of free pages falls below 2893 * the watermarks. 2894 */ 2895int zone_reclaim_mode __read_mostly; 2896 2897#define RECLAIM_OFF 0 2898#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2899#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2900#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2901 2902/* 2903 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2904 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2905 * a zone. 2906 */ 2907#define ZONE_RECLAIM_PRIORITY 4 2908 2909/* 2910 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2911 * occur. 2912 */ 2913int sysctl_min_unmapped_ratio = 1; 2914 2915/* 2916 * If the number of slab pages in a zone grows beyond this percentage then 2917 * slab reclaim needs to occur. 2918 */ 2919int sysctl_min_slab_ratio = 5; 2920 2921static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 2922{ 2923 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 2924 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 2925 zone_page_state(zone, NR_ACTIVE_FILE); 2926 2927 /* 2928 * It's possible for there to be more file mapped pages than 2929 * accounted for by the pages on the file LRU lists because 2930 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 2931 */ 2932 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 2933} 2934 2935/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 2936static long zone_pagecache_reclaimable(struct zone *zone) 2937{ 2938 long nr_pagecache_reclaimable; 2939 long delta = 0; 2940 2941 /* 2942 * If RECLAIM_SWAP is set, then all file pages are considered 2943 * potentially reclaimable. Otherwise, we have to worry about 2944 * pages like swapcache and zone_unmapped_file_pages() provides 2945 * a better estimate 2946 */ 2947 if (zone_reclaim_mode & RECLAIM_SWAP) 2948 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 2949 else 2950 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 2951 2952 /* If we can't clean pages, remove dirty pages from consideration */ 2953 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 2954 delta += zone_page_state(zone, NR_FILE_DIRTY); 2955 2956 /* Watch for any possible underflows due to delta */ 2957 if (unlikely(delta > nr_pagecache_reclaimable)) 2958 delta = nr_pagecache_reclaimable; 2959 2960 return nr_pagecache_reclaimable - delta; 2961} 2962 2963/* 2964 * Try to free up some pages from this zone through reclaim. 2965 */ 2966static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2967{ 2968 /* Minimum pages needed in order to stay on node */ 2969 const unsigned long nr_pages = 1 << order; 2970 struct task_struct *p = current; 2971 struct reclaim_state reclaim_state; 2972 int priority; 2973 struct scan_control sc = { 2974 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 2975 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 2976 .may_swap = 1, 2977 .nr_to_reclaim = max_t(unsigned long, nr_pages, 2978 SWAP_CLUSTER_MAX), 2979 .gfp_mask = gfp_mask, 2980 .swappiness = vm_swappiness, 2981 .order = order, 2982 }; 2983 unsigned long nr_slab_pages0, nr_slab_pages1; 2984 2985 cond_resched(); 2986 /* 2987 * We need to be able to allocate from the reserves for RECLAIM_SWAP 2988 * and we also need to be able to write out pages for RECLAIM_WRITE 2989 * and RECLAIM_SWAP. 2990 */ 2991 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 2992 lockdep_set_current_reclaim_state(gfp_mask); 2993 reclaim_state.reclaimed_slab = 0; 2994 p->reclaim_state = &reclaim_state; 2995 2996 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 2997 /* 2998 * Free memory by calling shrink zone with increasing 2999 * priorities until we have enough memory freed. 3000 */ 3001 priority = ZONE_RECLAIM_PRIORITY; 3002 do { 3003 shrink_zone(priority, zone, &sc); 3004 priority--; 3005 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 3006 } 3007 3008 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3009 if (nr_slab_pages0 > zone->min_slab_pages) { 3010 /* 3011 * shrink_slab() does not currently allow us to determine how 3012 * many pages were freed in this zone. So we take the current 3013 * number of slab pages and shake the slab until it is reduced 3014 * by the same nr_pages that we used for reclaiming unmapped 3015 * pages. 3016 * 3017 * Note that shrink_slab will free memory on all zones and may 3018 * take a long time. 3019 */ 3020 for (;;) { 3021 unsigned long lru_pages = zone_reclaimable_pages(zone); 3022 3023 /* No reclaimable slab or very low memory pressure */ 3024 if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) 3025 break; 3026 3027 /* Freed enough memory */ 3028 nr_slab_pages1 = zone_page_state(zone, 3029 NR_SLAB_RECLAIMABLE); 3030 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3031 break; 3032 } 3033 3034 /* 3035 * Update nr_reclaimed by the number of slab pages we 3036 * reclaimed from this zone. 3037 */ 3038 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3039 if (nr_slab_pages1 < nr_slab_pages0) 3040 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3041 } 3042 3043 p->reclaim_state = NULL; 3044 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3045 lockdep_clear_current_reclaim_state(); 3046 return sc.nr_reclaimed >= nr_pages; 3047} 3048 3049int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3050{ 3051 int node_id; 3052 int ret; 3053 3054 /* 3055 * Zone reclaim reclaims unmapped file backed pages and 3056 * slab pages if we are over the defined limits. 3057 * 3058 * A small portion of unmapped file backed pages is needed for 3059 * file I/O otherwise pages read by file I/O will be immediately 3060 * thrown out if the zone is overallocated. So we do not reclaim 3061 * if less than a specified percentage of the zone is used by 3062 * unmapped file backed pages. 3063 */ 3064 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3065 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3066 return ZONE_RECLAIM_FULL; 3067 3068 if (zone->all_unreclaimable) 3069 return ZONE_RECLAIM_FULL; 3070 3071 /* 3072 * Do not scan if the allocation should not be delayed. 3073 */ 3074 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3075 return ZONE_RECLAIM_NOSCAN; 3076 3077 /* 3078 * Only run zone reclaim on the local zone or on zones that do not 3079 * have associated processors. This will favor the local processor 3080 * over remote processors and spread off node memory allocations 3081 * as wide as possible. 3082 */ 3083 node_id = zone_to_nid(zone); 3084 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3085 return ZONE_RECLAIM_NOSCAN; 3086 3087 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3088 return ZONE_RECLAIM_NOSCAN; 3089 3090 ret = __zone_reclaim(zone, gfp_mask, order); 3091 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3092 3093 if (!ret) 3094 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3095 3096 return ret; 3097} 3098#endif 3099 3100/* 3101 * page_evictable - test whether a page is evictable 3102 * @page: the page to test 3103 * @vma: the VMA in which the page is or will be mapped, may be NULL 3104 * 3105 * Test whether page is evictable--i.e., should be placed on active/inactive 3106 * lists vs unevictable list. The vma argument is !NULL when called from the 3107 * fault path to determine how to instantate a new page. 3108 * 3109 * Reasons page might not be evictable: 3110 * (1) page's mapping marked unevictable 3111 * (2) page is part of an mlocked VMA 3112 * 3113 */ 3114int page_evictable(struct page *page, struct vm_area_struct *vma) 3115{ 3116 3117 if (mapping_unevictable(page_mapping(page))) 3118 return 0; 3119 3120 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3121 return 0; 3122 3123 return 1; 3124} 3125 3126/** 3127 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3128 * @page: page to check evictability and move to appropriate lru list 3129 * @zone: zone page is in 3130 * 3131 * Checks a page for evictability and moves the page to the appropriate 3132 * zone lru list. 3133 * 3134 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3135 * have PageUnevictable set. 3136 */ 3137static void check_move_unevictable_page(struct page *page, struct zone *zone) 3138{ 3139 VM_BUG_ON(PageActive(page)); 3140 3141retry: 3142 ClearPageUnevictable(page); 3143 if (page_evictable(page, NULL)) { 3144 enum lru_list l = page_lru_base_type(page); 3145 3146 __dec_zone_state(zone, NR_UNEVICTABLE); 3147 list_move(&page->lru, &zone->lru[l].list); 3148 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3149 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3150 __count_vm_event(UNEVICTABLE_PGRESCUED); 3151 } else { 3152 /* 3153 * rotate unevictable list 3154 */ 3155 SetPageUnevictable(page); 3156 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3157 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3158 if (page_evictable(page, NULL)) 3159 goto retry; 3160 } 3161} 3162 3163/** 3164 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3165 * @mapping: struct address_space to scan for evictable pages 3166 * 3167 * Scan all pages in mapping. Check unevictable pages for 3168 * evictability and move them to the appropriate zone lru list. 3169 */ 3170void scan_mapping_unevictable_pages(struct address_space *mapping) 3171{ 3172 pgoff_t next = 0; 3173 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3174 PAGE_CACHE_SHIFT; 3175 struct zone *zone; 3176 struct pagevec pvec; 3177 3178 if (mapping->nrpages == 0) 3179 return; 3180 3181 pagevec_init(&pvec, 0); 3182 while (next < end && 3183 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3184 int i; 3185 int pg_scanned = 0; 3186 3187 zone = NULL; 3188 3189 for (i = 0; i < pagevec_count(&pvec); i++) { 3190 struct page *page = pvec.pages[i]; 3191 pgoff_t page_index = page->index; 3192 struct zone *pagezone = page_zone(page); 3193 3194 pg_scanned++; 3195 if (page_index > next) 3196 next = page_index; 3197 next++; 3198 3199 if (pagezone != zone) { 3200 if (zone) 3201 spin_unlock_irq(&zone->lru_lock); 3202 zone = pagezone; 3203 spin_lock_irq(&zone->lru_lock); 3204 } 3205 3206 if (PageLRU(page) && PageUnevictable(page)) 3207 check_move_unevictable_page(page, zone); 3208 } 3209 if (zone) 3210 spin_unlock_irq(&zone->lru_lock); 3211 pagevec_release(&pvec); 3212 3213 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3214 } 3215 3216} 3217 3218/** 3219 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3220 * @zone - zone of which to scan the unevictable list 3221 * 3222 * Scan @zone's unevictable LRU lists to check for pages that have become 3223 * evictable. Move those that have to @zone's inactive list where they 3224 * become candidates for reclaim, unless shrink_inactive_zone() decides 3225 * to reactivate them. Pages that are still unevictable are rotated 3226 * back onto @zone's unevictable list. 3227 */ 3228#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3229static void scan_zone_unevictable_pages(struct zone *zone) 3230{ 3231 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3232 unsigned long scan; 3233 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3234 3235 while (nr_to_scan > 0) { 3236 unsigned long batch_size = min(nr_to_scan, 3237 SCAN_UNEVICTABLE_BATCH_SIZE); 3238 3239 spin_lock_irq(&zone->lru_lock); 3240 for (scan = 0; scan < batch_size; scan++) { 3241 struct page *page = lru_to_page(l_unevictable); 3242 3243 if (!trylock_page(page)) 3244 continue; 3245 3246 prefetchw_prev_lru_page(page, l_unevictable, flags); 3247 3248 if (likely(PageLRU(page) && PageUnevictable(page))) 3249 check_move_unevictable_page(page, zone); 3250 3251 unlock_page(page); 3252 } 3253 spin_unlock_irq(&zone->lru_lock); 3254 3255 nr_to_scan -= batch_size; 3256 } 3257} 3258 3259 3260/** 3261 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3262 * 3263 * A really big hammer: scan all zones' unevictable LRU lists to check for 3264 * pages that have become evictable. Move those back to the zones' 3265 * inactive list where they become candidates for reclaim. 3266 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3267 * and we add swap to the system. As such, it runs in the context of a task 3268 * that has possibly/probably made some previously unevictable pages 3269 * evictable. 3270 */ 3271static void scan_all_zones_unevictable_pages(void) 3272{ 3273 struct zone *zone; 3274 3275 for_each_zone(zone) { 3276 scan_zone_unevictable_pages(zone); 3277 } 3278} 3279 3280/* 3281 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3282 * all nodes' unevictable lists for evictable pages 3283 */ 3284unsigned long scan_unevictable_pages; 3285 3286int scan_unevictable_handler(struct ctl_table *table, int write, 3287 void __user *buffer, 3288 size_t *length, loff_t *ppos) 3289{ 3290 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3291 3292 if (write && *(unsigned long *)table->data) 3293 scan_all_zones_unevictable_pages(); 3294 3295 scan_unevictable_pages = 0; 3296 return 0; 3297} 3298 3299#ifdef CONFIG_NUMA 3300/* 3301 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3302 * a specified node's per zone unevictable lists for evictable pages. 3303 */ 3304 3305static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3306 struct sysdev_attribute *attr, 3307 char *buf) 3308{ 3309 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3310} 3311 3312static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3313 struct sysdev_attribute *attr, 3314 const char *buf, size_t count) 3315{ 3316 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3317 struct zone *zone; 3318 unsigned long res; 3319 unsigned long req = strict_strtoul(buf, 10, &res); 3320 3321 if (!req) 3322 return 1; /* zero is no-op */ 3323 3324 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3325 if (!populated_zone(zone)) 3326 continue; 3327 scan_zone_unevictable_pages(zone); 3328 } 3329 return 1; 3330} 3331 3332 3333static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3334 read_scan_unevictable_node, 3335 write_scan_unevictable_node); 3336 3337int scan_unevictable_register_node(struct node *node) 3338{ 3339 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3340} 3341 3342void scan_unevictable_unregister_node(struct node *node) 3343{ 3344 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3345} 3346#endif 3347