vmscan.c revision d2ebd0f6b89567eb93ead4e2ca0cbe03021f344b
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 order; 99 100 /* 101 * Intend to reclaim enough continuous memory rather than reclaim 102 * enough amount of memory. i.e, mode for high order allocation. 103 */ 104 reclaim_mode_t reclaim_mode; 105 106 /* Which cgroup do we reclaim from */ 107 struct mem_cgroup *mem_cgroup; 108 109 /* 110 * Nodemask of nodes allowed by the caller. If NULL, all nodes 111 * are scanned. 112 */ 113 nodemask_t *nodemask; 114}; 115 116#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 117 118#ifdef ARCH_HAS_PREFETCH 119#define prefetch_prev_lru_page(_page, _base, _field) \ 120 do { \ 121 if ((_page)->lru.prev != _base) { \ 122 struct page *prev; \ 123 \ 124 prev = lru_to_page(&(_page->lru)); \ 125 prefetch(&prev->_field); \ 126 } \ 127 } while (0) 128#else 129#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 130#endif 131 132#ifdef ARCH_HAS_PREFETCHW 133#define prefetchw_prev_lru_page(_page, _base, _field) \ 134 do { \ 135 if ((_page)->lru.prev != _base) { \ 136 struct page *prev; \ 137 \ 138 prev = lru_to_page(&(_page->lru)); \ 139 prefetchw(&prev->_field); \ 140 } \ 141 } while (0) 142#else 143#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 144#endif 145 146/* 147 * From 0 .. 100. Higher means more swappy. 148 */ 149int vm_swappiness = 60; 150long vm_total_pages; /* The total number of pages which the VM controls */ 151 152static LIST_HEAD(shrinker_list); 153static DECLARE_RWSEM(shrinker_rwsem); 154 155#ifdef CONFIG_CGROUP_MEM_RES_CTLR 156#define scanning_global_lru(sc) (!(sc)->mem_cgroup) 157#else 158#define scanning_global_lru(sc) (1) 159#endif 160 161static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 162 struct scan_control *sc) 163{ 164 if (!scanning_global_lru(sc)) 165 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 166 167 return &zone->reclaim_stat; 168} 169 170static unsigned long zone_nr_lru_pages(struct zone *zone, 171 struct scan_control *sc, enum lru_list lru) 172{ 173 if (!scanning_global_lru(sc)) 174 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup, 175 zone_to_nid(zone), zone_idx(zone), BIT(lru)); 176 177 return zone_page_state(zone, NR_LRU_BASE + lru); 178} 179 180 181/* 182 * Add a shrinker callback to be called from the vm 183 */ 184void register_shrinker(struct shrinker *shrinker) 185{ 186 shrinker->nr = 0; 187 down_write(&shrinker_rwsem); 188 list_add_tail(&shrinker->list, &shrinker_list); 189 up_write(&shrinker_rwsem); 190} 191EXPORT_SYMBOL(register_shrinker); 192 193/* 194 * Remove one 195 */ 196void unregister_shrinker(struct shrinker *shrinker) 197{ 198 down_write(&shrinker_rwsem); 199 list_del(&shrinker->list); 200 up_write(&shrinker_rwsem); 201} 202EXPORT_SYMBOL(unregister_shrinker); 203 204static inline int do_shrinker_shrink(struct shrinker *shrinker, 205 struct shrink_control *sc, 206 unsigned long nr_to_scan) 207{ 208 sc->nr_to_scan = nr_to_scan; 209 return (*shrinker->shrink)(shrinker, sc); 210} 211 212#define SHRINK_BATCH 128 213/* 214 * Call the shrink functions to age shrinkable caches 215 * 216 * Here we assume it costs one seek to replace a lru page and that it also 217 * takes a seek to recreate a cache object. With this in mind we age equal 218 * percentages of the lru and ageable caches. This should balance the seeks 219 * generated by these structures. 220 * 221 * If the vm encountered mapped pages on the LRU it increase the pressure on 222 * slab to avoid swapping. 223 * 224 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 225 * 226 * `lru_pages' represents the number of on-LRU pages in all the zones which 227 * are eligible for the caller's allocation attempt. It is used for balancing 228 * slab reclaim versus page reclaim. 229 * 230 * Returns the number of slab objects which we shrunk. 231 */ 232unsigned long shrink_slab(struct shrink_control *shrink, 233 unsigned long nr_pages_scanned, 234 unsigned long lru_pages) 235{ 236 struct shrinker *shrinker; 237 unsigned long ret = 0; 238 239 if (nr_pages_scanned == 0) 240 nr_pages_scanned = SWAP_CLUSTER_MAX; 241 242 if (!down_read_trylock(&shrinker_rwsem)) { 243 /* Assume we'll be able to shrink next time */ 244 ret = 1; 245 goto out; 246 } 247 248 list_for_each_entry(shrinker, &shrinker_list, list) { 249 unsigned long long delta; 250 unsigned long total_scan; 251 unsigned long max_pass; 252 int shrink_ret = 0; 253 long nr; 254 long new_nr; 255 long batch_size = shrinker->batch ? shrinker->batch 256 : SHRINK_BATCH; 257 258 /* 259 * copy the current shrinker scan count into a local variable 260 * and zero it so that other concurrent shrinker invocations 261 * don't also do this scanning work. 262 */ 263 do { 264 nr = shrinker->nr; 265 } while (cmpxchg(&shrinker->nr, nr, 0) != nr); 266 267 total_scan = nr; 268 max_pass = do_shrinker_shrink(shrinker, shrink, 0); 269 delta = (4 * nr_pages_scanned) / shrinker->seeks; 270 delta *= max_pass; 271 do_div(delta, lru_pages + 1); 272 total_scan += delta; 273 if (total_scan < 0) { 274 printk(KERN_ERR "shrink_slab: %pF negative objects to " 275 "delete nr=%ld\n", 276 shrinker->shrink, total_scan); 277 total_scan = max_pass; 278 } 279 280 /* 281 * We need to avoid excessive windup on filesystem shrinkers 282 * due to large numbers of GFP_NOFS allocations causing the 283 * shrinkers to return -1 all the time. This results in a large 284 * nr being built up so when a shrink that can do some work 285 * comes along it empties the entire cache due to nr >>> 286 * max_pass. This is bad for sustaining a working set in 287 * memory. 288 * 289 * Hence only allow the shrinker to scan the entire cache when 290 * a large delta change is calculated directly. 291 */ 292 if (delta < max_pass / 4) 293 total_scan = min(total_scan, max_pass / 2); 294 295 /* 296 * Avoid risking looping forever due to too large nr value: 297 * never try to free more than twice the estimate number of 298 * freeable entries. 299 */ 300 if (total_scan > max_pass * 2) 301 total_scan = max_pass * 2; 302 303 trace_mm_shrink_slab_start(shrinker, shrink, nr, 304 nr_pages_scanned, lru_pages, 305 max_pass, delta, total_scan); 306 307 while (total_scan >= batch_size) { 308 int nr_before; 309 310 nr_before = do_shrinker_shrink(shrinker, shrink, 0); 311 shrink_ret = do_shrinker_shrink(shrinker, shrink, 312 batch_size); 313 if (shrink_ret == -1) 314 break; 315 if (shrink_ret < nr_before) 316 ret += nr_before - shrink_ret; 317 count_vm_events(SLABS_SCANNED, batch_size); 318 total_scan -= batch_size; 319 320 cond_resched(); 321 } 322 323 /* 324 * move the unused scan count back into the shrinker in a 325 * manner that handles concurrent updates. If we exhausted the 326 * scan, there is no need to do an update. 327 */ 328 do { 329 nr = shrinker->nr; 330 new_nr = total_scan + nr; 331 if (total_scan <= 0) 332 break; 333 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr); 334 335 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); 336 } 337 up_read(&shrinker_rwsem); 338out: 339 cond_resched(); 340 return ret; 341} 342 343static void set_reclaim_mode(int priority, struct scan_control *sc, 344 bool sync) 345{ 346 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 347 348 /* 349 * Initially assume we are entering either lumpy reclaim or 350 * reclaim/compaction.Depending on the order, we will either set the 351 * sync mode or just reclaim order-0 pages later. 352 */ 353 if (COMPACTION_BUILD) 354 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 355 else 356 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 357 358 /* 359 * Avoid using lumpy reclaim or reclaim/compaction if possible by 360 * restricting when its set to either costly allocations or when 361 * under memory pressure 362 */ 363 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 364 sc->reclaim_mode |= syncmode; 365 else if (sc->order && priority < DEF_PRIORITY - 2) 366 sc->reclaim_mode |= syncmode; 367 else 368 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 369} 370 371static void reset_reclaim_mode(struct scan_control *sc) 372{ 373 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 374} 375 376static inline int is_page_cache_freeable(struct page *page) 377{ 378 /* 379 * A freeable page cache page is referenced only by the caller 380 * that isolated the page, the page cache radix tree and 381 * optional buffer heads at page->private. 382 */ 383 return page_count(page) - page_has_private(page) == 2; 384} 385 386static int may_write_to_queue(struct backing_dev_info *bdi, 387 struct scan_control *sc) 388{ 389 if (current->flags & PF_SWAPWRITE) 390 return 1; 391 if (!bdi_write_congested(bdi)) 392 return 1; 393 if (bdi == current->backing_dev_info) 394 return 1; 395 396 /* lumpy reclaim for hugepage often need a lot of write */ 397 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 398 return 1; 399 return 0; 400} 401 402/* 403 * We detected a synchronous write error writing a page out. Probably 404 * -ENOSPC. We need to propagate that into the address_space for a subsequent 405 * fsync(), msync() or close(). 406 * 407 * The tricky part is that after writepage we cannot touch the mapping: nothing 408 * prevents it from being freed up. But we have a ref on the page and once 409 * that page is locked, the mapping is pinned. 410 * 411 * We're allowed to run sleeping lock_page() here because we know the caller has 412 * __GFP_FS. 413 */ 414static void handle_write_error(struct address_space *mapping, 415 struct page *page, int error) 416{ 417 lock_page(page); 418 if (page_mapping(page) == mapping) 419 mapping_set_error(mapping, error); 420 unlock_page(page); 421} 422 423/* possible outcome of pageout() */ 424typedef enum { 425 /* failed to write page out, page is locked */ 426 PAGE_KEEP, 427 /* move page to the active list, page is locked */ 428 PAGE_ACTIVATE, 429 /* page has been sent to the disk successfully, page is unlocked */ 430 PAGE_SUCCESS, 431 /* page is clean and locked */ 432 PAGE_CLEAN, 433} pageout_t; 434 435/* 436 * pageout is called by shrink_page_list() for each dirty page. 437 * Calls ->writepage(). 438 */ 439static pageout_t pageout(struct page *page, struct address_space *mapping, 440 struct scan_control *sc) 441{ 442 /* 443 * If the page is dirty, only perform writeback if that write 444 * will be non-blocking. To prevent this allocation from being 445 * stalled by pagecache activity. But note that there may be 446 * stalls if we need to run get_block(). We could test 447 * PagePrivate for that. 448 * 449 * If this process is currently in __generic_file_aio_write() against 450 * this page's queue, we can perform writeback even if that 451 * will block. 452 * 453 * If the page is swapcache, write it back even if that would 454 * block, for some throttling. This happens by accident, because 455 * swap_backing_dev_info is bust: it doesn't reflect the 456 * congestion state of the swapdevs. Easy to fix, if needed. 457 */ 458 if (!is_page_cache_freeable(page)) 459 return PAGE_KEEP; 460 if (!mapping) { 461 /* 462 * Some data journaling orphaned pages can have 463 * page->mapping == NULL while being dirty with clean buffers. 464 */ 465 if (page_has_private(page)) { 466 if (try_to_free_buffers(page)) { 467 ClearPageDirty(page); 468 printk("%s: orphaned page\n", __func__); 469 return PAGE_CLEAN; 470 } 471 } 472 return PAGE_KEEP; 473 } 474 if (mapping->a_ops->writepage == NULL) 475 return PAGE_ACTIVATE; 476 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 477 return PAGE_KEEP; 478 479 if (clear_page_dirty_for_io(page)) { 480 int res; 481 struct writeback_control wbc = { 482 .sync_mode = WB_SYNC_NONE, 483 .nr_to_write = SWAP_CLUSTER_MAX, 484 .range_start = 0, 485 .range_end = LLONG_MAX, 486 .for_reclaim = 1, 487 }; 488 489 SetPageReclaim(page); 490 res = mapping->a_ops->writepage(page, &wbc); 491 if (res < 0) 492 handle_write_error(mapping, page, res); 493 if (res == AOP_WRITEPAGE_ACTIVATE) { 494 ClearPageReclaim(page); 495 return PAGE_ACTIVATE; 496 } 497 498 if (!PageWriteback(page)) { 499 /* synchronous write or broken a_ops? */ 500 ClearPageReclaim(page); 501 } 502 trace_mm_vmscan_writepage(page, 503 trace_reclaim_flags(page, sc->reclaim_mode)); 504 inc_zone_page_state(page, NR_VMSCAN_WRITE); 505 return PAGE_SUCCESS; 506 } 507 508 return PAGE_CLEAN; 509} 510 511/* 512 * Same as remove_mapping, but if the page is removed from the mapping, it 513 * gets returned with a refcount of 0. 514 */ 515static int __remove_mapping(struct address_space *mapping, struct page *page) 516{ 517 BUG_ON(!PageLocked(page)); 518 BUG_ON(mapping != page_mapping(page)); 519 520 spin_lock_irq(&mapping->tree_lock); 521 /* 522 * The non racy check for a busy page. 523 * 524 * Must be careful with the order of the tests. When someone has 525 * a ref to the page, it may be possible that they dirty it then 526 * drop the reference. So if PageDirty is tested before page_count 527 * here, then the following race may occur: 528 * 529 * get_user_pages(&page); 530 * [user mapping goes away] 531 * write_to(page); 532 * !PageDirty(page) [good] 533 * SetPageDirty(page); 534 * put_page(page); 535 * !page_count(page) [good, discard it] 536 * 537 * [oops, our write_to data is lost] 538 * 539 * Reversing the order of the tests ensures such a situation cannot 540 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 541 * load is not satisfied before that of page->_count. 542 * 543 * Note that if SetPageDirty is always performed via set_page_dirty, 544 * and thus under tree_lock, then this ordering is not required. 545 */ 546 if (!page_freeze_refs(page, 2)) 547 goto cannot_free; 548 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 549 if (unlikely(PageDirty(page))) { 550 page_unfreeze_refs(page, 2); 551 goto cannot_free; 552 } 553 554 if (PageSwapCache(page)) { 555 swp_entry_t swap = { .val = page_private(page) }; 556 __delete_from_swap_cache(page); 557 spin_unlock_irq(&mapping->tree_lock); 558 swapcache_free(swap, page); 559 } else { 560 void (*freepage)(struct page *); 561 562 freepage = mapping->a_ops->freepage; 563 564 __delete_from_page_cache(page); 565 spin_unlock_irq(&mapping->tree_lock); 566 mem_cgroup_uncharge_cache_page(page); 567 568 if (freepage != NULL) 569 freepage(page); 570 } 571 572 return 1; 573 574cannot_free: 575 spin_unlock_irq(&mapping->tree_lock); 576 return 0; 577} 578 579/* 580 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 581 * someone else has a ref on the page, abort and return 0. If it was 582 * successfully detached, return 1. Assumes the caller has a single ref on 583 * this page. 584 */ 585int remove_mapping(struct address_space *mapping, struct page *page) 586{ 587 if (__remove_mapping(mapping, page)) { 588 /* 589 * Unfreezing the refcount with 1 rather than 2 effectively 590 * drops the pagecache ref for us without requiring another 591 * atomic operation. 592 */ 593 page_unfreeze_refs(page, 1); 594 return 1; 595 } 596 return 0; 597} 598 599/** 600 * putback_lru_page - put previously isolated page onto appropriate LRU list 601 * @page: page to be put back to appropriate lru list 602 * 603 * Add previously isolated @page to appropriate LRU list. 604 * Page may still be unevictable for other reasons. 605 * 606 * lru_lock must not be held, interrupts must be enabled. 607 */ 608void putback_lru_page(struct page *page) 609{ 610 int lru; 611 int active = !!TestClearPageActive(page); 612 int was_unevictable = PageUnevictable(page); 613 614 VM_BUG_ON(PageLRU(page)); 615 616redo: 617 ClearPageUnevictable(page); 618 619 if (page_evictable(page, NULL)) { 620 /* 621 * For evictable pages, we can use the cache. 622 * In event of a race, worst case is we end up with an 623 * unevictable page on [in]active list. 624 * We know how to handle that. 625 */ 626 lru = active + page_lru_base_type(page); 627 lru_cache_add_lru(page, lru); 628 } else { 629 /* 630 * Put unevictable pages directly on zone's unevictable 631 * list. 632 */ 633 lru = LRU_UNEVICTABLE; 634 add_page_to_unevictable_list(page); 635 /* 636 * When racing with an mlock clearing (page is 637 * unlocked), make sure that if the other thread does 638 * not observe our setting of PG_lru and fails 639 * isolation, we see PG_mlocked cleared below and move 640 * the page back to the evictable list. 641 * 642 * The other side is TestClearPageMlocked(). 643 */ 644 smp_mb(); 645 } 646 647 /* 648 * page's status can change while we move it among lru. If an evictable 649 * page is on unevictable list, it never be freed. To avoid that, 650 * check after we added it to the list, again. 651 */ 652 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 653 if (!isolate_lru_page(page)) { 654 put_page(page); 655 goto redo; 656 } 657 /* This means someone else dropped this page from LRU 658 * So, it will be freed or putback to LRU again. There is 659 * nothing to do here. 660 */ 661 } 662 663 if (was_unevictable && lru != LRU_UNEVICTABLE) 664 count_vm_event(UNEVICTABLE_PGRESCUED); 665 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 666 count_vm_event(UNEVICTABLE_PGCULLED); 667 668 put_page(page); /* drop ref from isolate */ 669} 670 671enum page_references { 672 PAGEREF_RECLAIM, 673 PAGEREF_RECLAIM_CLEAN, 674 PAGEREF_KEEP, 675 PAGEREF_ACTIVATE, 676}; 677 678static enum page_references page_check_references(struct page *page, 679 struct scan_control *sc) 680{ 681 int referenced_ptes, referenced_page; 682 unsigned long vm_flags; 683 684 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 685 referenced_page = TestClearPageReferenced(page); 686 687 /* Lumpy reclaim - ignore references */ 688 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 689 return PAGEREF_RECLAIM; 690 691 /* 692 * Mlock lost the isolation race with us. Let try_to_unmap() 693 * move the page to the unevictable list. 694 */ 695 if (vm_flags & VM_LOCKED) 696 return PAGEREF_RECLAIM; 697 698 if (referenced_ptes) { 699 if (PageAnon(page)) 700 return PAGEREF_ACTIVATE; 701 /* 702 * All mapped pages start out with page table 703 * references from the instantiating fault, so we need 704 * to look twice if a mapped file page is used more 705 * than once. 706 * 707 * Mark it and spare it for another trip around the 708 * inactive list. Another page table reference will 709 * lead to its activation. 710 * 711 * Note: the mark is set for activated pages as well 712 * so that recently deactivated but used pages are 713 * quickly recovered. 714 */ 715 SetPageReferenced(page); 716 717 if (referenced_page) 718 return PAGEREF_ACTIVATE; 719 720 return PAGEREF_KEEP; 721 } 722 723 /* Reclaim if clean, defer dirty pages to writeback */ 724 if (referenced_page && !PageSwapBacked(page)) 725 return PAGEREF_RECLAIM_CLEAN; 726 727 return PAGEREF_RECLAIM; 728} 729 730static noinline_for_stack void free_page_list(struct list_head *free_pages) 731{ 732 struct pagevec freed_pvec; 733 struct page *page, *tmp; 734 735 pagevec_init(&freed_pvec, 1); 736 737 list_for_each_entry_safe(page, tmp, free_pages, lru) { 738 list_del(&page->lru); 739 if (!pagevec_add(&freed_pvec, page)) { 740 __pagevec_free(&freed_pvec); 741 pagevec_reinit(&freed_pvec); 742 } 743 } 744 745 pagevec_free(&freed_pvec); 746} 747 748/* 749 * shrink_page_list() returns the number of reclaimed pages 750 */ 751static unsigned long shrink_page_list(struct list_head *page_list, 752 struct zone *zone, 753 struct scan_control *sc, 754 int priority, 755 unsigned long *ret_nr_dirty, 756 unsigned long *ret_nr_writeback) 757{ 758 LIST_HEAD(ret_pages); 759 LIST_HEAD(free_pages); 760 int pgactivate = 0; 761 unsigned long nr_dirty = 0; 762 unsigned long nr_congested = 0; 763 unsigned long nr_reclaimed = 0; 764 unsigned long nr_writeback = 0; 765 766 cond_resched(); 767 768 while (!list_empty(page_list)) { 769 enum page_references references; 770 struct address_space *mapping; 771 struct page *page; 772 int may_enter_fs; 773 774 cond_resched(); 775 776 page = lru_to_page(page_list); 777 list_del(&page->lru); 778 779 if (!trylock_page(page)) 780 goto keep; 781 782 VM_BUG_ON(PageActive(page)); 783 VM_BUG_ON(page_zone(page) != zone); 784 785 sc->nr_scanned++; 786 787 if (unlikely(!page_evictable(page, NULL))) 788 goto cull_mlocked; 789 790 if (!sc->may_unmap && page_mapped(page)) 791 goto keep_locked; 792 793 /* Double the slab pressure for mapped and swapcache pages */ 794 if (page_mapped(page) || PageSwapCache(page)) 795 sc->nr_scanned++; 796 797 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 798 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 799 800 if (PageWriteback(page)) { 801 nr_writeback++; 802 /* 803 * Synchronous reclaim cannot queue pages for 804 * writeback due to the possibility of stack overflow 805 * but if it encounters a page under writeback, wait 806 * for the IO to complete. 807 */ 808 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 809 may_enter_fs) 810 wait_on_page_writeback(page); 811 else { 812 unlock_page(page); 813 goto keep_lumpy; 814 } 815 } 816 817 references = page_check_references(page, sc); 818 switch (references) { 819 case PAGEREF_ACTIVATE: 820 goto activate_locked; 821 case PAGEREF_KEEP: 822 goto keep_locked; 823 case PAGEREF_RECLAIM: 824 case PAGEREF_RECLAIM_CLEAN: 825 ; /* try to reclaim the page below */ 826 } 827 828 /* 829 * Anonymous process memory has backing store? 830 * Try to allocate it some swap space here. 831 */ 832 if (PageAnon(page) && !PageSwapCache(page)) { 833 if (!(sc->gfp_mask & __GFP_IO)) 834 goto keep_locked; 835 if (!add_to_swap(page)) 836 goto activate_locked; 837 may_enter_fs = 1; 838 } 839 840 mapping = page_mapping(page); 841 842 /* 843 * The page is mapped into the page tables of one or more 844 * processes. Try to unmap it here. 845 */ 846 if (page_mapped(page) && mapping) { 847 switch (try_to_unmap(page, TTU_UNMAP)) { 848 case SWAP_FAIL: 849 goto activate_locked; 850 case SWAP_AGAIN: 851 goto keep_locked; 852 case SWAP_MLOCK: 853 goto cull_mlocked; 854 case SWAP_SUCCESS: 855 ; /* try to free the page below */ 856 } 857 } 858 859 if (PageDirty(page)) { 860 nr_dirty++; 861 862 /* 863 * Only kswapd can writeback filesystem pages to 864 * avoid risk of stack overflow but do not writeback 865 * unless under significant pressure. 866 */ 867 if (page_is_file_cache(page) && 868 (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) { 869 /* 870 * Immediately reclaim when written back. 871 * Similar in principal to deactivate_page() 872 * except we already have the page isolated 873 * and know it's dirty 874 */ 875 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); 876 SetPageReclaim(page); 877 878 goto keep_locked; 879 } 880 881 if (references == PAGEREF_RECLAIM_CLEAN) 882 goto keep_locked; 883 if (!may_enter_fs) 884 goto keep_locked; 885 if (!sc->may_writepage) 886 goto keep_locked; 887 888 /* Page is dirty, try to write it out here */ 889 switch (pageout(page, mapping, sc)) { 890 case PAGE_KEEP: 891 nr_congested++; 892 goto keep_locked; 893 case PAGE_ACTIVATE: 894 goto activate_locked; 895 case PAGE_SUCCESS: 896 if (PageWriteback(page)) 897 goto keep_lumpy; 898 if (PageDirty(page)) 899 goto keep; 900 901 /* 902 * A synchronous write - probably a ramdisk. Go 903 * ahead and try to reclaim the page. 904 */ 905 if (!trylock_page(page)) 906 goto keep; 907 if (PageDirty(page) || PageWriteback(page)) 908 goto keep_locked; 909 mapping = page_mapping(page); 910 case PAGE_CLEAN: 911 ; /* try to free the page below */ 912 } 913 } 914 915 /* 916 * If the page has buffers, try to free the buffer mappings 917 * associated with this page. If we succeed we try to free 918 * the page as well. 919 * 920 * We do this even if the page is PageDirty(). 921 * try_to_release_page() does not perform I/O, but it is 922 * possible for a page to have PageDirty set, but it is actually 923 * clean (all its buffers are clean). This happens if the 924 * buffers were written out directly, with submit_bh(). ext3 925 * will do this, as well as the blockdev mapping. 926 * try_to_release_page() will discover that cleanness and will 927 * drop the buffers and mark the page clean - it can be freed. 928 * 929 * Rarely, pages can have buffers and no ->mapping. These are 930 * the pages which were not successfully invalidated in 931 * truncate_complete_page(). We try to drop those buffers here 932 * and if that worked, and the page is no longer mapped into 933 * process address space (page_count == 1) it can be freed. 934 * Otherwise, leave the page on the LRU so it is swappable. 935 */ 936 if (page_has_private(page)) { 937 if (!try_to_release_page(page, sc->gfp_mask)) 938 goto activate_locked; 939 if (!mapping && page_count(page) == 1) { 940 unlock_page(page); 941 if (put_page_testzero(page)) 942 goto free_it; 943 else { 944 /* 945 * rare race with speculative reference. 946 * the speculative reference will free 947 * this page shortly, so we may 948 * increment nr_reclaimed here (and 949 * leave it off the LRU). 950 */ 951 nr_reclaimed++; 952 continue; 953 } 954 } 955 } 956 957 if (!mapping || !__remove_mapping(mapping, page)) 958 goto keep_locked; 959 960 /* 961 * At this point, we have no other references and there is 962 * no way to pick any more up (removed from LRU, removed 963 * from pagecache). Can use non-atomic bitops now (and 964 * we obviously don't have to worry about waking up a process 965 * waiting on the page lock, because there are no references. 966 */ 967 __clear_page_locked(page); 968free_it: 969 nr_reclaimed++; 970 971 /* 972 * Is there need to periodically free_page_list? It would 973 * appear not as the counts should be low 974 */ 975 list_add(&page->lru, &free_pages); 976 continue; 977 978cull_mlocked: 979 if (PageSwapCache(page)) 980 try_to_free_swap(page); 981 unlock_page(page); 982 putback_lru_page(page); 983 reset_reclaim_mode(sc); 984 continue; 985 986activate_locked: 987 /* Not a candidate for swapping, so reclaim swap space. */ 988 if (PageSwapCache(page) && vm_swap_full()) 989 try_to_free_swap(page); 990 VM_BUG_ON(PageActive(page)); 991 SetPageActive(page); 992 pgactivate++; 993keep_locked: 994 unlock_page(page); 995keep: 996 reset_reclaim_mode(sc); 997keep_lumpy: 998 list_add(&page->lru, &ret_pages); 999 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 1000 } 1001 1002 /* 1003 * Tag a zone as congested if all the dirty pages encountered were 1004 * backed by a congested BDI. In this case, reclaimers should just 1005 * back off and wait for congestion to clear because further reclaim 1006 * will encounter the same problem 1007 */ 1008 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) 1009 zone_set_flag(zone, ZONE_CONGESTED); 1010 1011 free_page_list(&free_pages); 1012 1013 list_splice(&ret_pages, page_list); 1014 count_vm_events(PGACTIVATE, pgactivate); 1015 *ret_nr_dirty += nr_dirty; 1016 *ret_nr_writeback += nr_writeback; 1017 return nr_reclaimed; 1018} 1019 1020/* 1021 * Attempt to remove the specified page from its LRU. Only take this page 1022 * if it is of the appropriate PageActive status. Pages which are being 1023 * freed elsewhere are also ignored. 1024 * 1025 * page: page to consider 1026 * mode: one of the LRU isolation modes defined above 1027 * 1028 * returns 0 on success, -ve errno on failure. 1029 */ 1030int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file) 1031{ 1032 bool all_lru_mode; 1033 int ret = -EINVAL; 1034 1035 /* Only take pages on the LRU. */ 1036 if (!PageLRU(page)) 1037 return ret; 1038 1039 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) == 1040 (ISOLATE_ACTIVE|ISOLATE_INACTIVE); 1041 1042 /* 1043 * When checking the active state, we need to be sure we are 1044 * dealing with comparible boolean values. Take the logical not 1045 * of each. 1046 */ 1047 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE)) 1048 return ret; 1049 1050 if (!all_lru_mode && !!page_is_file_cache(page) != file) 1051 return ret; 1052 1053 /* 1054 * When this function is being called for lumpy reclaim, we 1055 * initially look into all LRU pages, active, inactive and 1056 * unevictable; only give shrink_page_list evictable pages. 1057 */ 1058 if (PageUnevictable(page)) 1059 return ret; 1060 1061 ret = -EBUSY; 1062 1063 if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page))) 1064 return ret; 1065 1066 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) 1067 return ret; 1068 1069 if (likely(get_page_unless_zero(page))) { 1070 /* 1071 * Be careful not to clear PageLRU until after we're 1072 * sure the page is not being freed elsewhere -- the 1073 * page release code relies on it. 1074 */ 1075 ClearPageLRU(page); 1076 ret = 0; 1077 } 1078 1079 return ret; 1080} 1081 1082/* 1083 * zone->lru_lock is heavily contended. Some of the functions that 1084 * shrink the lists perform better by taking out a batch of pages 1085 * and working on them outside the LRU lock. 1086 * 1087 * For pagecache intensive workloads, this function is the hottest 1088 * spot in the kernel (apart from copy_*_user functions). 1089 * 1090 * Appropriate locks must be held before calling this function. 1091 * 1092 * @nr_to_scan: The number of pages to look through on the list. 1093 * @src: The LRU list to pull pages off. 1094 * @dst: The temp list to put pages on to. 1095 * @scanned: The number of pages that were scanned. 1096 * @order: The caller's attempted allocation order 1097 * @mode: One of the LRU isolation modes 1098 * @file: True [1] if isolating file [!anon] pages 1099 * 1100 * returns how many pages were moved onto *@dst. 1101 */ 1102static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1103 struct list_head *src, struct list_head *dst, 1104 unsigned long *scanned, int order, isolate_mode_t mode, 1105 int file) 1106{ 1107 unsigned long nr_taken = 0; 1108 unsigned long nr_lumpy_taken = 0; 1109 unsigned long nr_lumpy_dirty = 0; 1110 unsigned long nr_lumpy_failed = 0; 1111 unsigned long scan; 1112 1113 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1114 struct page *page; 1115 unsigned long pfn; 1116 unsigned long end_pfn; 1117 unsigned long page_pfn; 1118 int zone_id; 1119 1120 page = lru_to_page(src); 1121 prefetchw_prev_lru_page(page, src, flags); 1122 1123 VM_BUG_ON(!PageLRU(page)); 1124 1125 switch (__isolate_lru_page(page, mode, file)) { 1126 case 0: 1127 list_move(&page->lru, dst); 1128 mem_cgroup_del_lru(page); 1129 nr_taken += hpage_nr_pages(page); 1130 break; 1131 1132 case -EBUSY: 1133 /* else it is being freed elsewhere */ 1134 list_move(&page->lru, src); 1135 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1136 continue; 1137 1138 default: 1139 BUG(); 1140 } 1141 1142 if (!order) 1143 continue; 1144 1145 /* 1146 * Attempt to take all pages in the order aligned region 1147 * surrounding the tag page. Only take those pages of 1148 * the same active state as that tag page. We may safely 1149 * round the target page pfn down to the requested order 1150 * as the mem_map is guaranteed valid out to MAX_ORDER, 1151 * where that page is in a different zone we will detect 1152 * it from its zone id and abort this block scan. 1153 */ 1154 zone_id = page_zone_id(page); 1155 page_pfn = page_to_pfn(page); 1156 pfn = page_pfn & ~((1 << order) - 1); 1157 end_pfn = pfn + (1 << order); 1158 for (; pfn < end_pfn; pfn++) { 1159 struct page *cursor_page; 1160 1161 /* The target page is in the block, ignore it. */ 1162 if (unlikely(pfn == page_pfn)) 1163 continue; 1164 1165 /* Avoid holes within the zone. */ 1166 if (unlikely(!pfn_valid_within(pfn))) 1167 break; 1168 1169 cursor_page = pfn_to_page(pfn); 1170 1171 /* Check that we have not crossed a zone boundary. */ 1172 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1173 break; 1174 1175 /* 1176 * If we don't have enough swap space, reclaiming of 1177 * anon page which don't already have a swap slot is 1178 * pointless. 1179 */ 1180 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1181 !PageSwapCache(cursor_page)) 1182 break; 1183 1184 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1185 list_move(&cursor_page->lru, dst); 1186 mem_cgroup_del_lru(cursor_page); 1187 nr_taken += hpage_nr_pages(page); 1188 nr_lumpy_taken++; 1189 if (PageDirty(cursor_page)) 1190 nr_lumpy_dirty++; 1191 scan++; 1192 } else { 1193 /* 1194 * Check if the page is freed already. 1195 * 1196 * We can't use page_count() as that 1197 * requires compound_head and we don't 1198 * have a pin on the page here. If a 1199 * page is tail, we may or may not 1200 * have isolated the head, so assume 1201 * it's not free, it'd be tricky to 1202 * track the head status without a 1203 * page pin. 1204 */ 1205 if (!PageTail(cursor_page) && 1206 !atomic_read(&cursor_page->_count)) 1207 continue; 1208 break; 1209 } 1210 } 1211 1212 /* If we break out of the loop above, lumpy reclaim failed */ 1213 if (pfn < end_pfn) 1214 nr_lumpy_failed++; 1215 } 1216 1217 *scanned = scan; 1218 1219 trace_mm_vmscan_lru_isolate(order, 1220 nr_to_scan, scan, 1221 nr_taken, 1222 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1223 mode); 1224 return nr_taken; 1225} 1226 1227static unsigned long isolate_pages_global(unsigned long nr, 1228 struct list_head *dst, 1229 unsigned long *scanned, int order, 1230 isolate_mode_t mode, 1231 struct zone *z, int active, int file) 1232{ 1233 int lru = LRU_BASE; 1234 if (active) 1235 lru += LRU_ACTIVE; 1236 if (file) 1237 lru += LRU_FILE; 1238 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1239 mode, file); 1240} 1241 1242/* 1243 * clear_active_flags() is a helper for shrink_active_list(), clearing 1244 * any active bits from the pages in the list. 1245 */ 1246static unsigned long clear_active_flags(struct list_head *page_list, 1247 unsigned int *count) 1248{ 1249 int nr_active = 0; 1250 int lru; 1251 struct page *page; 1252 1253 list_for_each_entry(page, page_list, lru) { 1254 int numpages = hpage_nr_pages(page); 1255 lru = page_lru_base_type(page); 1256 if (PageActive(page)) { 1257 lru += LRU_ACTIVE; 1258 ClearPageActive(page); 1259 nr_active += numpages; 1260 } 1261 if (count) 1262 count[lru] += numpages; 1263 } 1264 1265 return nr_active; 1266} 1267 1268/** 1269 * isolate_lru_page - tries to isolate a page from its LRU list 1270 * @page: page to isolate from its LRU list 1271 * 1272 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1273 * vmstat statistic corresponding to whatever LRU list the page was on. 1274 * 1275 * Returns 0 if the page was removed from an LRU list. 1276 * Returns -EBUSY if the page was not on an LRU list. 1277 * 1278 * The returned page will have PageLRU() cleared. If it was found on 1279 * the active list, it will have PageActive set. If it was found on 1280 * the unevictable list, it will have the PageUnevictable bit set. That flag 1281 * may need to be cleared by the caller before letting the page go. 1282 * 1283 * The vmstat statistic corresponding to the list on which the page was 1284 * found will be decremented. 1285 * 1286 * Restrictions: 1287 * (1) Must be called with an elevated refcount on the page. This is a 1288 * fundamentnal difference from isolate_lru_pages (which is called 1289 * without a stable reference). 1290 * (2) the lru_lock must not be held. 1291 * (3) interrupts must be enabled. 1292 */ 1293int isolate_lru_page(struct page *page) 1294{ 1295 int ret = -EBUSY; 1296 1297 VM_BUG_ON(!page_count(page)); 1298 1299 if (PageLRU(page)) { 1300 struct zone *zone = page_zone(page); 1301 1302 spin_lock_irq(&zone->lru_lock); 1303 if (PageLRU(page)) { 1304 int lru = page_lru(page); 1305 ret = 0; 1306 get_page(page); 1307 ClearPageLRU(page); 1308 1309 del_page_from_lru_list(zone, page, lru); 1310 } 1311 spin_unlock_irq(&zone->lru_lock); 1312 } 1313 return ret; 1314} 1315 1316/* 1317 * Are there way too many processes in the direct reclaim path already? 1318 */ 1319static int too_many_isolated(struct zone *zone, int file, 1320 struct scan_control *sc) 1321{ 1322 unsigned long inactive, isolated; 1323 1324 if (current_is_kswapd()) 1325 return 0; 1326 1327 if (!scanning_global_lru(sc)) 1328 return 0; 1329 1330 if (file) { 1331 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1332 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1333 } else { 1334 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1335 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1336 } 1337 1338 return isolated > inactive; 1339} 1340 1341/* 1342 * TODO: Try merging with migrations version of putback_lru_pages 1343 */ 1344static noinline_for_stack void 1345putback_lru_pages(struct zone *zone, struct scan_control *sc, 1346 unsigned long nr_anon, unsigned long nr_file, 1347 struct list_head *page_list) 1348{ 1349 struct page *page; 1350 struct pagevec pvec; 1351 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1352 1353 pagevec_init(&pvec, 1); 1354 1355 /* 1356 * Put back any unfreeable pages. 1357 */ 1358 spin_lock(&zone->lru_lock); 1359 while (!list_empty(page_list)) { 1360 int lru; 1361 page = lru_to_page(page_list); 1362 VM_BUG_ON(PageLRU(page)); 1363 list_del(&page->lru); 1364 if (unlikely(!page_evictable(page, NULL))) { 1365 spin_unlock_irq(&zone->lru_lock); 1366 putback_lru_page(page); 1367 spin_lock_irq(&zone->lru_lock); 1368 continue; 1369 } 1370 SetPageLRU(page); 1371 lru = page_lru(page); 1372 add_page_to_lru_list(zone, page, lru); 1373 if (is_active_lru(lru)) { 1374 int file = is_file_lru(lru); 1375 int numpages = hpage_nr_pages(page); 1376 reclaim_stat->recent_rotated[file] += numpages; 1377 } 1378 if (!pagevec_add(&pvec, page)) { 1379 spin_unlock_irq(&zone->lru_lock); 1380 __pagevec_release(&pvec); 1381 spin_lock_irq(&zone->lru_lock); 1382 } 1383 } 1384 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1385 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1386 1387 spin_unlock_irq(&zone->lru_lock); 1388 pagevec_release(&pvec); 1389} 1390 1391static noinline_for_stack void update_isolated_counts(struct zone *zone, 1392 struct scan_control *sc, 1393 unsigned long *nr_anon, 1394 unsigned long *nr_file, 1395 struct list_head *isolated_list) 1396{ 1397 unsigned long nr_active; 1398 unsigned int count[NR_LRU_LISTS] = { 0, }; 1399 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1400 1401 nr_active = clear_active_flags(isolated_list, count); 1402 __count_vm_events(PGDEACTIVATE, nr_active); 1403 1404 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1405 -count[LRU_ACTIVE_FILE]); 1406 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1407 -count[LRU_INACTIVE_FILE]); 1408 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1409 -count[LRU_ACTIVE_ANON]); 1410 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1411 -count[LRU_INACTIVE_ANON]); 1412 1413 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1414 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1415 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1416 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1417 1418 reclaim_stat->recent_scanned[0] += *nr_anon; 1419 reclaim_stat->recent_scanned[1] += *nr_file; 1420} 1421 1422/* 1423 * Returns true if a direct reclaim should wait on pages under writeback. 1424 * 1425 * If we are direct reclaiming for contiguous pages and we do not reclaim 1426 * everything in the list, try again and wait for writeback IO to complete. 1427 * This will stall high-order allocations noticeably. Only do that when really 1428 * need to free the pages under high memory pressure. 1429 */ 1430static inline bool should_reclaim_stall(unsigned long nr_taken, 1431 unsigned long nr_freed, 1432 int priority, 1433 struct scan_control *sc) 1434{ 1435 int lumpy_stall_priority; 1436 1437 /* kswapd should not stall on sync IO */ 1438 if (current_is_kswapd()) 1439 return false; 1440 1441 /* Only stall on lumpy reclaim */ 1442 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1443 return false; 1444 1445 /* If we have reclaimed everything on the isolated list, no stall */ 1446 if (nr_freed == nr_taken) 1447 return false; 1448 1449 /* 1450 * For high-order allocations, there are two stall thresholds. 1451 * High-cost allocations stall immediately where as lower 1452 * order allocations such as stacks require the scanning 1453 * priority to be much higher before stalling. 1454 */ 1455 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1456 lumpy_stall_priority = DEF_PRIORITY; 1457 else 1458 lumpy_stall_priority = DEF_PRIORITY / 3; 1459 1460 return priority <= lumpy_stall_priority; 1461} 1462 1463/* 1464 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1465 * of reclaimed pages 1466 */ 1467static noinline_for_stack unsigned long 1468shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1469 struct scan_control *sc, int priority, int file) 1470{ 1471 LIST_HEAD(page_list); 1472 unsigned long nr_scanned; 1473 unsigned long nr_reclaimed = 0; 1474 unsigned long nr_taken; 1475 unsigned long nr_anon; 1476 unsigned long nr_file; 1477 unsigned long nr_dirty = 0; 1478 unsigned long nr_writeback = 0; 1479 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE; 1480 1481 while (unlikely(too_many_isolated(zone, file, sc))) { 1482 congestion_wait(BLK_RW_ASYNC, HZ/10); 1483 1484 /* We are about to die and free our memory. Return now. */ 1485 if (fatal_signal_pending(current)) 1486 return SWAP_CLUSTER_MAX; 1487 } 1488 1489 set_reclaim_mode(priority, sc, false); 1490 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 1491 reclaim_mode |= ISOLATE_ACTIVE; 1492 1493 lru_add_drain(); 1494 1495 if (!sc->may_unmap) 1496 reclaim_mode |= ISOLATE_UNMAPPED; 1497 if (!sc->may_writepage) 1498 reclaim_mode |= ISOLATE_CLEAN; 1499 1500 spin_lock_irq(&zone->lru_lock); 1501 1502 if (scanning_global_lru(sc)) { 1503 nr_taken = isolate_pages_global(nr_to_scan, &page_list, 1504 &nr_scanned, sc->order, reclaim_mode, zone, 0, file); 1505 zone->pages_scanned += nr_scanned; 1506 if (current_is_kswapd()) 1507 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1508 nr_scanned); 1509 else 1510 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1511 nr_scanned); 1512 } else { 1513 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list, 1514 &nr_scanned, sc->order, reclaim_mode, zone, 1515 sc->mem_cgroup, 0, file); 1516 /* 1517 * mem_cgroup_isolate_pages() keeps track of 1518 * scanned pages on its own. 1519 */ 1520 } 1521 1522 if (nr_taken == 0) { 1523 spin_unlock_irq(&zone->lru_lock); 1524 return 0; 1525 } 1526 1527 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1528 1529 spin_unlock_irq(&zone->lru_lock); 1530 1531 nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority, 1532 &nr_dirty, &nr_writeback); 1533 1534 /* Check if we should syncronously wait for writeback */ 1535 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1536 set_reclaim_mode(priority, sc, true); 1537 nr_reclaimed += shrink_page_list(&page_list, zone, sc, 1538 priority, &nr_dirty, &nr_writeback); 1539 } 1540 1541 local_irq_disable(); 1542 if (current_is_kswapd()) 1543 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1544 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1545 1546 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1547 1548 /* 1549 * If reclaim is isolating dirty pages under writeback, it implies 1550 * that the long-lived page allocation rate is exceeding the page 1551 * laundering rate. Either the global limits are not being effective 1552 * at throttling processes due to the page distribution throughout 1553 * zones or there is heavy usage of a slow backing device. The 1554 * only option is to throttle from reclaim context which is not ideal 1555 * as there is no guarantee the dirtying process is throttled in the 1556 * same way balance_dirty_pages() manages. 1557 * 1558 * This scales the number of dirty pages that must be under writeback 1559 * before throttling depending on priority. It is a simple backoff 1560 * function that has the most effect in the range DEF_PRIORITY to 1561 * DEF_PRIORITY-2 which is the priority reclaim is considered to be 1562 * in trouble and reclaim is considered to be in trouble. 1563 * 1564 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle 1565 * DEF_PRIORITY-1 50% must be PageWriteback 1566 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble 1567 * ... 1568 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any 1569 * isolated page is PageWriteback 1570 */ 1571 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority))) 1572 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); 1573 1574 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1575 zone_idx(zone), 1576 nr_scanned, nr_reclaimed, 1577 priority, 1578 trace_shrink_flags(file, sc->reclaim_mode)); 1579 return nr_reclaimed; 1580} 1581 1582/* 1583 * This moves pages from the active list to the inactive list. 1584 * 1585 * We move them the other way if the page is referenced by one or more 1586 * processes, from rmap. 1587 * 1588 * If the pages are mostly unmapped, the processing is fast and it is 1589 * appropriate to hold zone->lru_lock across the whole operation. But if 1590 * the pages are mapped, the processing is slow (page_referenced()) so we 1591 * should drop zone->lru_lock around each page. It's impossible to balance 1592 * this, so instead we remove the pages from the LRU while processing them. 1593 * It is safe to rely on PG_active against the non-LRU pages in here because 1594 * nobody will play with that bit on a non-LRU page. 1595 * 1596 * The downside is that we have to touch page->_count against each page. 1597 * But we had to alter page->flags anyway. 1598 */ 1599 1600static void move_active_pages_to_lru(struct zone *zone, 1601 struct list_head *list, 1602 enum lru_list lru) 1603{ 1604 unsigned long pgmoved = 0; 1605 struct pagevec pvec; 1606 struct page *page; 1607 1608 pagevec_init(&pvec, 1); 1609 1610 while (!list_empty(list)) { 1611 page = lru_to_page(list); 1612 1613 VM_BUG_ON(PageLRU(page)); 1614 SetPageLRU(page); 1615 1616 list_move(&page->lru, &zone->lru[lru].list); 1617 mem_cgroup_add_lru_list(page, lru); 1618 pgmoved += hpage_nr_pages(page); 1619 1620 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1621 spin_unlock_irq(&zone->lru_lock); 1622 if (buffer_heads_over_limit) 1623 pagevec_strip(&pvec); 1624 __pagevec_release(&pvec); 1625 spin_lock_irq(&zone->lru_lock); 1626 } 1627 } 1628 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1629 if (!is_active_lru(lru)) 1630 __count_vm_events(PGDEACTIVATE, pgmoved); 1631} 1632 1633static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1634 struct scan_control *sc, int priority, int file) 1635{ 1636 unsigned long nr_taken; 1637 unsigned long pgscanned; 1638 unsigned long vm_flags; 1639 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1640 LIST_HEAD(l_active); 1641 LIST_HEAD(l_inactive); 1642 struct page *page; 1643 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1644 unsigned long nr_rotated = 0; 1645 isolate_mode_t reclaim_mode = ISOLATE_ACTIVE; 1646 1647 lru_add_drain(); 1648 1649 if (!sc->may_unmap) 1650 reclaim_mode |= ISOLATE_UNMAPPED; 1651 if (!sc->may_writepage) 1652 reclaim_mode |= ISOLATE_CLEAN; 1653 1654 spin_lock_irq(&zone->lru_lock); 1655 if (scanning_global_lru(sc)) { 1656 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1657 &pgscanned, sc->order, 1658 reclaim_mode, zone, 1659 1, file); 1660 zone->pages_scanned += pgscanned; 1661 } else { 1662 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1663 &pgscanned, sc->order, 1664 reclaim_mode, zone, 1665 sc->mem_cgroup, 1, file); 1666 /* 1667 * mem_cgroup_isolate_pages() keeps track of 1668 * scanned pages on its own. 1669 */ 1670 } 1671 1672 reclaim_stat->recent_scanned[file] += nr_taken; 1673 1674 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1675 if (file) 1676 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1677 else 1678 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1679 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1680 spin_unlock_irq(&zone->lru_lock); 1681 1682 while (!list_empty(&l_hold)) { 1683 cond_resched(); 1684 page = lru_to_page(&l_hold); 1685 list_del(&page->lru); 1686 1687 if (unlikely(!page_evictable(page, NULL))) { 1688 putback_lru_page(page); 1689 continue; 1690 } 1691 1692 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1693 nr_rotated += hpage_nr_pages(page); 1694 /* 1695 * Identify referenced, file-backed active pages and 1696 * give them one more trip around the active list. So 1697 * that executable code get better chances to stay in 1698 * memory under moderate memory pressure. Anon pages 1699 * are not likely to be evicted by use-once streaming 1700 * IO, plus JVM can create lots of anon VM_EXEC pages, 1701 * so we ignore them here. 1702 */ 1703 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1704 list_add(&page->lru, &l_active); 1705 continue; 1706 } 1707 } 1708 1709 ClearPageActive(page); /* we are de-activating */ 1710 list_add(&page->lru, &l_inactive); 1711 } 1712 1713 /* 1714 * Move pages back to the lru list. 1715 */ 1716 spin_lock_irq(&zone->lru_lock); 1717 /* 1718 * Count referenced pages from currently used mappings as rotated, 1719 * even though only some of them are actually re-activated. This 1720 * helps balance scan pressure between file and anonymous pages in 1721 * get_scan_ratio. 1722 */ 1723 reclaim_stat->recent_rotated[file] += nr_rotated; 1724 1725 move_active_pages_to_lru(zone, &l_active, 1726 LRU_ACTIVE + file * LRU_FILE); 1727 move_active_pages_to_lru(zone, &l_inactive, 1728 LRU_BASE + file * LRU_FILE); 1729 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1730 spin_unlock_irq(&zone->lru_lock); 1731} 1732 1733#ifdef CONFIG_SWAP 1734static int inactive_anon_is_low_global(struct zone *zone) 1735{ 1736 unsigned long active, inactive; 1737 1738 active = zone_page_state(zone, NR_ACTIVE_ANON); 1739 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1740 1741 if (inactive * zone->inactive_ratio < active) 1742 return 1; 1743 1744 return 0; 1745} 1746 1747/** 1748 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1749 * @zone: zone to check 1750 * @sc: scan control of this context 1751 * 1752 * Returns true if the zone does not have enough inactive anon pages, 1753 * meaning some active anon pages need to be deactivated. 1754 */ 1755static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1756{ 1757 int low; 1758 1759 /* 1760 * If we don't have swap space, anonymous page deactivation 1761 * is pointless. 1762 */ 1763 if (!total_swap_pages) 1764 return 0; 1765 1766 if (scanning_global_lru(sc)) 1767 low = inactive_anon_is_low_global(zone); 1768 else 1769 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1770 return low; 1771} 1772#else 1773static inline int inactive_anon_is_low(struct zone *zone, 1774 struct scan_control *sc) 1775{ 1776 return 0; 1777} 1778#endif 1779 1780static int inactive_file_is_low_global(struct zone *zone) 1781{ 1782 unsigned long active, inactive; 1783 1784 active = zone_page_state(zone, NR_ACTIVE_FILE); 1785 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1786 1787 return (active > inactive); 1788} 1789 1790/** 1791 * inactive_file_is_low - check if file pages need to be deactivated 1792 * @zone: zone to check 1793 * @sc: scan control of this context 1794 * 1795 * When the system is doing streaming IO, memory pressure here 1796 * ensures that active file pages get deactivated, until more 1797 * than half of the file pages are on the inactive list. 1798 * 1799 * Once we get to that situation, protect the system's working 1800 * set from being evicted by disabling active file page aging. 1801 * 1802 * This uses a different ratio than the anonymous pages, because 1803 * the page cache uses a use-once replacement algorithm. 1804 */ 1805static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1806{ 1807 int low; 1808 1809 if (scanning_global_lru(sc)) 1810 low = inactive_file_is_low_global(zone); 1811 else 1812 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1813 return low; 1814} 1815 1816static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1817 int file) 1818{ 1819 if (file) 1820 return inactive_file_is_low(zone, sc); 1821 else 1822 return inactive_anon_is_low(zone, sc); 1823} 1824 1825static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1826 struct zone *zone, struct scan_control *sc, int priority) 1827{ 1828 int file = is_file_lru(lru); 1829 1830 if (is_active_lru(lru)) { 1831 if (inactive_list_is_low(zone, sc, file)) 1832 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1833 return 0; 1834 } 1835 1836 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1837} 1838 1839static int vmscan_swappiness(struct scan_control *sc) 1840{ 1841 if (scanning_global_lru(sc)) 1842 return vm_swappiness; 1843 return mem_cgroup_swappiness(sc->mem_cgroup); 1844} 1845 1846/* 1847 * Determine how aggressively the anon and file LRU lists should be 1848 * scanned. The relative value of each set of LRU lists is determined 1849 * by looking at the fraction of the pages scanned we did rotate back 1850 * onto the active list instead of evict. 1851 * 1852 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1853 */ 1854static void get_scan_count(struct zone *zone, struct scan_control *sc, 1855 unsigned long *nr, int priority) 1856{ 1857 unsigned long anon, file, free; 1858 unsigned long anon_prio, file_prio; 1859 unsigned long ap, fp; 1860 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1861 u64 fraction[2], denominator; 1862 enum lru_list l; 1863 int noswap = 0; 1864 bool force_scan = false; 1865 1866 /* 1867 * If the zone or memcg is small, nr[l] can be 0. This 1868 * results in no scanning on this priority and a potential 1869 * priority drop. Global direct reclaim can go to the next 1870 * zone and tends to have no problems. Global kswapd is for 1871 * zone balancing and it needs to scan a minimum amount. When 1872 * reclaiming for a memcg, a priority drop can cause high 1873 * latencies, so it's better to scan a minimum amount there as 1874 * well. 1875 */ 1876 if (scanning_global_lru(sc) && current_is_kswapd()) 1877 force_scan = true; 1878 if (!scanning_global_lru(sc)) 1879 force_scan = true; 1880 1881 /* If we have no swap space, do not bother scanning anon pages. */ 1882 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1883 noswap = 1; 1884 fraction[0] = 0; 1885 fraction[1] = 1; 1886 denominator = 1; 1887 goto out; 1888 } 1889 1890 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1891 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1892 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1893 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1894 1895 if (scanning_global_lru(sc)) { 1896 free = zone_page_state(zone, NR_FREE_PAGES); 1897 /* If we have very few page cache pages, 1898 force-scan anon pages. */ 1899 if (unlikely(file + free <= high_wmark_pages(zone))) { 1900 fraction[0] = 1; 1901 fraction[1] = 0; 1902 denominator = 1; 1903 goto out; 1904 } 1905 } 1906 1907 /* 1908 * With swappiness at 100, anonymous and file have the same priority. 1909 * This scanning priority is essentially the inverse of IO cost. 1910 */ 1911 anon_prio = vmscan_swappiness(sc); 1912 file_prio = 200 - vmscan_swappiness(sc); 1913 1914 /* 1915 * OK, so we have swap space and a fair amount of page cache 1916 * pages. We use the recently rotated / recently scanned 1917 * ratios to determine how valuable each cache is. 1918 * 1919 * Because workloads change over time (and to avoid overflow) 1920 * we keep these statistics as a floating average, which ends 1921 * up weighing recent references more than old ones. 1922 * 1923 * anon in [0], file in [1] 1924 */ 1925 spin_lock_irq(&zone->lru_lock); 1926 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1927 reclaim_stat->recent_scanned[0] /= 2; 1928 reclaim_stat->recent_rotated[0] /= 2; 1929 } 1930 1931 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1932 reclaim_stat->recent_scanned[1] /= 2; 1933 reclaim_stat->recent_rotated[1] /= 2; 1934 } 1935 1936 /* 1937 * The amount of pressure on anon vs file pages is inversely 1938 * proportional to the fraction of recently scanned pages on 1939 * each list that were recently referenced and in active use. 1940 */ 1941 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1942 ap /= reclaim_stat->recent_rotated[0] + 1; 1943 1944 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1945 fp /= reclaim_stat->recent_rotated[1] + 1; 1946 spin_unlock_irq(&zone->lru_lock); 1947 1948 fraction[0] = ap; 1949 fraction[1] = fp; 1950 denominator = ap + fp + 1; 1951out: 1952 for_each_evictable_lru(l) { 1953 int file = is_file_lru(l); 1954 unsigned long scan; 1955 1956 scan = zone_nr_lru_pages(zone, sc, l); 1957 if (priority || noswap) { 1958 scan >>= priority; 1959 if (!scan && force_scan) 1960 scan = SWAP_CLUSTER_MAX; 1961 scan = div64_u64(scan * fraction[file], denominator); 1962 } 1963 nr[l] = scan; 1964 } 1965} 1966 1967/* 1968 * Reclaim/compaction depends on a number of pages being freed. To avoid 1969 * disruption to the system, a small number of order-0 pages continue to be 1970 * rotated and reclaimed in the normal fashion. However, by the time we get 1971 * back to the allocator and call try_to_compact_zone(), we ensure that 1972 * there are enough free pages for it to be likely successful 1973 */ 1974static inline bool should_continue_reclaim(struct zone *zone, 1975 unsigned long nr_reclaimed, 1976 unsigned long nr_scanned, 1977 struct scan_control *sc) 1978{ 1979 unsigned long pages_for_compaction; 1980 unsigned long inactive_lru_pages; 1981 1982 /* If not in reclaim/compaction mode, stop */ 1983 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1984 return false; 1985 1986 /* Consider stopping depending on scan and reclaim activity */ 1987 if (sc->gfp_mask & __GFP_REPEAT) { 1988 /* 1989 * For __GFP_REPEAT allocations, stop reclaiming if the 1990 * full LRU list has been scanned and we are still failing 1991 * to reclaim pages. This full LRU scan is potentially 1992 * expensive but a __GFP_REPEAT caller really wants to succeed 1993 */ 1994 if (!nr_reclaimed && !nr_scanned) 1995 return false; 1996 } else { 1997 /* 1998 * For non-__GFP_REPEAT allocations which can presumably 1999 * fail without consequence, stop if we failed to reclaim 2000 * any pages from the last SWAP_CLUSTER_MAX number of 2001 * pages that were scanned. This will return to the 2002 * caller faster at the risk reclaim/compaction and 2003 * the resulting allocation attempt fails 2004 */ 2005 if (!nr_reclaimed) 2006 return false; 2007 } 2008 2009 /* 2010 * If we have not reclaimed enough pages for compaction and the 2011 * inactive lists are large enough, continue reclaiming 2012 */ 2013 pages_for_compaction = (2UL << sc->order); 2014 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 2015 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 2016 if (sc->nr_reclaimed < pages_for_compaction && 2017 inactive_lru_pages > pages_for_compaction) 2018 return true; 2019 2020 /* If compaction would go ahead or the allocation would succeed, stop */ 2021 switch (compaction_suitable(zone, sc->order)) { 2022 case COMPACT_PARTIAL: 2023 case COMPACT_CONTINUE: 2024 return false; 2025 default: 2026 return true; 2027 } 2028} 2029 2030/* 2031 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 2032 */ 2033static void shrink_zone(int priority, struct zone *zone, 2034 struct scan_control *sc) 2035{ 2036 unsigned long nr[NR_LRU_LISTS]; 2037 unsigned long nr_to_scan; 2038 enum lru_list l; 2039 unsigned long nr_reclaimed, nr_scanned; 2040 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 2041 struct blk_plug plug; 2042 2043restart: 2044 nr_reclaimed = 0; 2045 nr_scanned = sc->nr_scanned; 2046 get_scan_count(zone, sc, nr, priority); 2047 2048 blk_start_plug(&plug); 2049 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 2050 nr[LRU_INACTIVE_FILE]) { 2051 for_each_evictable_lru(l) { 2052 if (nr[l]) { 2053 nr_to_scan = min_t(unsigned long, 2054 nr[l], SWAP_CLUSTER_MAX); 2055 nr[l] -= nr_to_scan; 2056 2057 nr_reclaimed += shrink_list(l, nr_to_scan, 2058 zone, sc, priority); 2059 } 2060 } 2061 /* 2062 * On large memory systems, scan >> priority can become 2063 * really large. This is fine for the starting priority; 2064 * we want to put equal scanning pressure on each zone. 2065 * However, if the VM has a harder time of freeing pages, 2066 * with multiple processes reclaiming pages, the total 2067 * freeing target can get unreasonably large. 2068 */ 2069 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 2070 break; 2071 } 2072 blk_finish_plug(&plug); 2073 sc->nr_reclaimed += nr_reclaimed; 2074 2075 /* 2076 * Even if we did not try to evict anon pages at all, we want to 2077 * rebalance the anon lru active/inactive ratio. 2078 */ 2079 if (inactive_anon_is_low(zone, sc)) 2080 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 2081 2082 /* reclaim/compaction might need reclaim to continue */ 2083 if (should_continue_reclaim(zone, nr_reclaimed, 2084 sc->nr_scanned - nr_scanned, sc)) 2085 goto restart; 2086 2087 throttle_vm_writeout(sc->gfp_mask); 2088} 2089 2090/* 2091 * This is the direct reclaim path, for page-allocating processes. We only 2092 * try to reclaim pages from zones which will satisfy the caller's allocation 2093 * request. 2094 * 2095 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 2096 * Because: 2097 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 2098 * allocation or 2099 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 2100 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 2101 * zone defense algorithm. 2102 * 2103 * If a zone is deemed to be full of pinned pages then just give it a light 2104 * scan then give up on it. 2105 */ 2106static void shrink_zones(int priority, struct zonelist *zonelist, 2107 struct scan_control *sc) 2108{ 2109 struct zoneref *z; 2110 struct zone *zone; 2111 unsigned long nr_soft_reclaimed; 2112 unsigned long nr_soft_scanned; 2113 2114 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2115 gfp_zone(sc->gfp_mask), sc->nodemask) { 2116 if (!populated_zone(zone)) 2117 continue; 2118 /* 2119 * Take care memory controller reclaiming has small influence 2120 * to global LRU. 2121 */ 2122 if (scanning_global_lru(sc)) { 2123 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2124 continue; 2125 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2126 continue; /* Let kswapd poll it */ 2127 /* 2128 * This steals pages from memory cgroups over softlimit 2129 * and returns the number of reclaimed pages and 2130 * scanned pages. This works for global memory pressure 2131 * and balancing, not for a memcg's limit. 2132 */ 2133 nr_soft_scanned = 0; 2134 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2135 sc->order, sc->gfp_mask, 2136 &nr_soft_scanned); 2137 sc->nr_reclaimed += nr_soft_reclaimed; 2138 sc->nr_scanned += nr_soft_scanned; 2139 /* need some check for avoid more shrink_zone() */ 2140 } 2141 2142 shrink_zone(priority, zone, sc); 2143 } 2144} 2145 2146static bool zone_reclaimable(struct zone *zone) 2147{ 2148 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 2149} 2150 2151/* All zones in zonelist are unreclaimable? */ 2152static bool all_unreclaimable(struct zonelist *zonelist, 2153 struct scan_control *sc) 2154{ 2155 struct zoneref *z; 2156 struct zone *zone; 2157 2158 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2159 gfp_zone(sc->gfp_mask), sc->nodemask) { 2160 if (!populated_zone(zone)) 2161 continue; 2162 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2163 continue; 2164 if (!zone->all_unreclaimable) 2165 return false; 2166 } 2167 2168 return true; 2169} 2170 2171/* 2172 * This is the main entry point to direct page reclaim. 2173 * 2174 * If a full scan of the inactive list fails to free enough memory then we 2175 * are "out of memory" and something needs to be killed. 2176 * 2177 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2178 * high - the zone may be full of dirty or under-writeback pages, which this 2179 * caller can't do much about. We kick the writeback threads and take explicit 2180 * naps in the hope that some of these pages can be written. But if the 2181 * allocating task holds filesystem locks which prevent writeout this might not 2182 * work, and the allocation attempt will fail. 2183 * 2184 * returns: 0, if no pages reclaimed 2185 * else, the number of pages reclaimed 2186 */ 2187static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2188 struct scan_control *sc, 2189 struct shrink_control *shrink) 2190{ 2191 int priority; 2192 unsigned long total_scanned = 0; 2193 struct reclaim_state *reclaim_state = current->reclaim_state; 2194 struct zoneref *z; 2195 struct zone *zone; 2196 unsigned long writeback_threshold; 2197 2198 get_mems_allowed(); 2199 delayacct_freepages_start(); 2200 2201 if (scanning_global_lru(sc)) 2202 count_vm_event(ALLOCSTALL); 2203 2204 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2205 sc->nr_scanned = 0; 2206 if (!priority) 2207 disable_swap_token(sc->mem_cgroup); 2208 shrink_zones(priority, zonelist, sc); 2209 /* 2210 * Don't shrink slabs when reclaiming memory from 2211 * over limit cgroups 2212 */ 2213 if (scanning_global_lru(sc)) { 2214 unsigned long lru_pages = 0; 2215 for_each_zone_zonelist(zone, z, zonelist, 2216 gfp_zone(sc->gfp_mask)) { 2217 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2218 continue; 2219 2220 lru_pages += zone_reclaimable_pages(zone); 2221 } 2222 2223 shrink_slab(shrink, sc->nr_scanned, lru_pages); 2224 if (reclaim_state) { 2225 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2226 reclaim_state->reclaimed_slab = 0; 2227 } 2228 } 2229 total_scanned += sc->nr_scanned; 2230 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2231 goto out; 2232 2233 /* 2234 * Try to write back as many pages as we just scanned. This 2235 * tends to cause slow streaming writers to write data to the 2236 * disk smoothly, at the dirtying rate, which is nice. But 2237 * that's undesirable in laptop mode, where we *want* lumpy 2238 * writeout. So in laptop mode, write out the whole world. 2239 */ 2240 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2241 if (total_scanned > writeback_threshold) { 2242 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2243 sc->may_writepage = 1; 2244 } 2245 2246 /* Take a nap, wait for some writeback to complete */ 2247 if (!sc->hibernation_mode && sc->nr_scanned && 2248 priority < DEF_PRIORITY - 2) { 2249 struct zone *preferred_zone; 2250 2251 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2252 &cpuset_current_mems_allowed, 2253 &preferred_zone); 2254 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2255 } 2256 } 2257 2258out: 2259 delayacct_freepages_end(); 2260 put_mems_allowed(); 2261 2262 if (sc->nr_reclaimed) 2263 return sc->nr_reclaimed; 2264 2265 /* 2266 * As hibernation is going on, kswapd is freezed so that it can't mark 2267 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2268 * check. 2269 */ 2270 if (oom_killer_disabled) 2271 return 0; 2272 2273 /* top priority shrink_zones still had more to do? don't OOM, then */ 2274 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2275 return 1; 2276 2277 return 0; 2278} 2279 2280unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2281 gfp_t gfp_mask, nodemask_t *nodemask) 2282{ 2283 unsigned long nr_reclaimed; 2284 struct scan_control sc = { 2285 .gfp_mask = gfp_mask, 2286 .may_writepage = !laptop_mode, 2287 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2288 .may_unmap = 1, 2289 .may_swap = 1, 2290 .order = order, 2291 .mem_cgroup = NULL, 2292 .nodemask = nodemask, 2293 }; 2294 struct shrink_control shrink = { 2295 .gfp_mask = sc.gfp_mask, 2296 }; 2297 2298 trace_mm_vmscan_direct_reclaim_begin(order, 2299 sc.may_writepage, 2300 gfp_mask); 2301 2302 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2303 2304 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2305 2306 return nr_reclaimed; 2307} 2308 2309#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2310 2311unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2312 gfp_t gfp_mask, bool noswap, 2313 struct zone *zone, 2314 unsigned long *nr_scanned) 2315{ 2316 struct scan_control sc = { 2317 .nr_scanned = 0, 2318 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2319 .may_writepage = !laptop_mode, 2320 .may_unmap = 1, 2321 .may_swap = !noswap, 2322 .order = 0, 2323 .mem_cgroup = mem, 2324 }; 2325 2326 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2327 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2328 2329 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2330 sc.may_writepage, 2331 sc.gfp_mask); 2332 2333 /* 2334 * NOTE: Although we can get the priority field, using it 2335 * here is not a good idea, since it limits the pages we can scan. 2336 * if we don't reclaim here, the shrink_zone from balance_pgdat 2337 * will pick up pages from other mem cgroup's as well. We hack 2338 * the priority and make it zero. 2339 */ 2340 shrink_zone(0, zone, &sc); 2341 2342 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2343 2344 *nr_scanned = sc.nr_scanned; 2345 return sc.nr_reclaimed; 2346} 2347 2348unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2349 gfp_t gfp_mask, 2350 bool noswap) 2351{ 2352 struct zonelist *zonelist; 2353 unsigned long nr_reclaimed; 2354 int nid; 2355 struct scan_control sc = { 2356 .may_writepage = !laptop_mode, 2357 .may_unmap = 1, 2358 .may_swap = !noswap, 2359 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2360 .order = 0, 2361 .mem_cgroup = mem_cont, 2362 .nodemask = NULL, /* we don't care the placement */ 2363 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2364 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), 2365 }; 2366 struct shrink_control shrink = { 2367 .gfp_mask = sc.gfp_mask, 2368 }; 2369 2370 /* 2371 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't 2372 * take care of from where we get pages. So the node where we start the 2373 * scan does not need to be the current node. 2374 */ 2375 nid = mem_cgroup_select_victim_node(mem_cont); 2376 2377 zonelist = NODE_DATA(nid)->node_zonelists; 2378 2379 trace_mm_vmscan_memcg_reclaim_begin(0, 2380 sc.may_writepage, 2381 sc.gfp_mask); 2382 2383 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2384 2385 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2386 2387 return nr_reclaimed; 2388} 2389#endif 2390 2391/* 2392 * pgdat_balanced is used when checking if a node is balanced for high-order 2393 * allocations. Only zones that meet watermarks and are in a zone allowed 2394 * by the callers classzone_idx are added to balanced_pages. The total of 2395 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2396 * for the node to be considered balanced. Forcing all zones to be balanced 2397 * for high orders can cause excessive reclaim when there are imbalanced zones. 2398 * The choice of 25% is due to 2399 * o a 16M DMA zone that is balanced will not balance a zone on any 2400 * reasonable sized machine 2401 * o On all other machines, the top zone must be at least a reasonable 2402 * percentage of the middle zones. For example, on 32-bit x86, highmem 2403 * would need to be at least 256M for it to be balance a whole node. 2404 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2405 * to balance a node on its own. These seemed like reasonable ratios. 2406 */ 2407static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2408 int classzone_idx) 2409{ 2410 unsigned long present_pages = 0; 2411 int i; 2412 2413 for (i = 0; i <= classzone_idx; i++) 2414 present_pages += pgdat->node_zones[i].present_pages; 2415 2416 /* A special case here: if zone has no page, we think it's balanced */ 2417 return balanced_pages >= (present_pages >> 2); 2418} 2419 2420/* is kswapd sleeping prematurely? */ 2421static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2422 int classzone_idx) 2423{ 2424 int i; 2425 unsigned long balanced = 0; 2426 bool all_zones_ok = true; 2427 2428 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2429 if (remaining) 2430 return true; 2431 2432 /* Check the watermark levels */ 2433 for (i = 0; i <= classzone_idx; i++) { 2434 struct zone *zone = pgdat->node_zones + i; 2435 2436 if (!populated_zone(zone)) 2437 continue; 2438 2439 /* 2440 * balance_pgdat() skips over all_unreclaimable after 2441 * DEF_PRIORITY. Effectively, it considers them balanced so 2442 * they must be considered balanced here as well if kswapd 2443 * is to sleep 2444 */ 2445 if (zone->all_unreclaimable) { 2446 balanced += zone->present_pages; 2447 continue; 2448 } 2449 2450 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2451 i, 0)) 2452 all_zones_ok = false; 2453 else 2454 balanced += zone->present_pages; 2455 } 2456 2457 /* 2458 * For high-order requests, the balanced zones must contain at least 2459 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2460 * must be balanced 2461 */ 2462 if (order) 2463 return !pgdat_balanced(pgdat, balanced, classzone_idx); 2464 else 2465 return !all_zones_ok; 2466} 2467 2468/* 2469 * For kswapd, balance_pgdat() will work across all this node's zones until 2470 * they are all at high_wmark_pages(zone). 2471 * 2472 * Returns the final order kswapd was reclaiming at 2473 * 2474 * There is special handling here for zones which are full of pinned pages. 2475 * This can happen if the pages are all mlocked, or if they are all used by 2476 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2477 * What we do is to detect the case where all pages in the zone have been 2478 * scanned twice and there has been zero successful reclaim. Mark the zone as 2479 * dead and from now on, only perform a short scan. Basically we're polling 2480 * the zone for when the problem goes away. 2481 * 2482 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2483 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2484 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2485 * lower zones regardless of the number of free pages in the lower zones. This 2486 * interoperates with the page allocator fallback scheme to ensure that aging 2487 * of pages is balanced across the zones. 2488 */ 2489static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2490 int *classzone_idx) 2491{ 2492 int all_zones_ok; 2493 unsigned long balanced; 2494 int priority; 2495 int i; 2496 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2497 unsigned long total_scanned; 2498 struct reclaim_state *reclaim_state = current->reclaim_state; 2499 unsigned long nr_soft_reclaimed; 2500 unsigned long nr_soft_scanned; 2501 struct scan_control sc = { 2502 .gfp_mask = GFP_KERNEL, 2503 .may_unmap = 1, 2504 .may_swap = 1, 2505 /* 2506 * kswapd doesn't want to be bailed out while reclaim. because 2507 * we want to put equal scanning pressure on each zone. 2508 */ 2509 .nr_to_reclaim = ULONG_MAX, 2510 .order = order, 2511 .mem_cgroup = NULL, 2512 }; 2513 struct shrink_control shrink = { 2514 .gfp_mask = sc.gfp_mask, 2515 }; 2516loop_again: 2517 total_scanned = 0; 2518 sc.nr_reclaimed = 0; 2519 sc.may_writepage = !laptop_mode; 2520 count_vm_event(PAGEOUTRUN); 2521 2522 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2523 unsigned long lru_pages = 0; 2524 int has_under_min_watermark_zone = 0; 2525 2526 /* The swap token gets in the way of swapout... */ 2527 if (!priority) 2528 disable_swap_token(NULL); 2529 2530 all_zones_ok = 1; 2531 balanced = 0; 2532 2533 /* 2534 * Scan in the highmem->dma direction for the highest 2535 * zone which needs scanning 2536 */ 2537 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2538 struct zone *zone = pgdat->node_zones + i; 2539 2540 if (!populated_zone(zone)) 2541 continue; 2542 2543 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2544 continue; 2545 2546 /* 2547 * Do some background aging of the anon list, to give 2548 * pages a chance to be referenced before reclaiming. 2549 */ 2550 if (inactive_anon_is_low(zone, &sc)) 2551 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2552 &sc, priority, 0); 2553 2554 if (!zone_watermark_ok_safe(zone, order, 2555 high_wmark_pages(zone), 0, 0)) { 2556 end_zone = i; 2557 break; 2558 } else { 2559 /* If balanced, clear the congested flag */ 2560 zone_clear_flag(zone, ZONE_CONGESTED); 2561 } 2562 } 2563 if (i < 0) 2564 goto out; 2565 2566 for (i = 0; i <= end_zone; i++) { 2567 struct zone *zone = pgdat->node_zones + i; 2568 2569 lru_pages += zone_reclaimable_pages(zone); 2570 } 2571 2572 /* 2573 * Now scan the zone in the dma->highmem direction, stopping 2574 * at the last zone which needs scanning. 2575 * 2576 * We do this because the page allocator works in the opposite 2577 * direction. This prevents the page allocator from allocating 2578 * pages behind kswapd's direction of progress, which would 2579 * cause too much scanning of the lower zones. 2580 */ 2581 for (i = 0; i <= end_zone; i++) { 2582 struct zone *zone = pgdat->node_zones + i; 2583 int nr_slab; 2584 unsigned long balance_gap; 2585 2586 if (!populated_zone(zone)) 2587 continue; 2588 2589 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2590 continue; 2591 2592 sc.nr_scanned = 0; 2593 2594 nr_soft_scanned = 0; 2595 /* 2596 * Call soft limit reclaim before calling shrink_zone. 2597 */ 2598 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2599 order, sc.gfp_mask, 2600 &nr_soft_scanned); 2601 sc.nr_reclaimed += nr_soft_reclaimed; 2602 total_scanned += nr_soft_scanned; 2603 2604 /* 2605 * We put equal pressure on every zone, unless 2606 * one zone has way too many pages free 2607 * already. The "too many pages" is defined 2608 * as the high wmark plus a "gap" where the 2609 * gap is either the low watermark or 1% 2610 * of the zone, whichever is smaller. 2611 */ 2612 balance_gap = min(low_wmark_pages(zone), 2613 (zone->present_pages + 2614 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2615 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2616 if (!zone_watermark_ok_safe(zone, order, 2617 high_wmark_pages(zone) + balance_gap, 2618 end_zone, 0)) { 2619 shrink_zone(priority, zone, &sc); 2620 2621 reclaim_state->reclaimed_slab = 0; 2622 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); 2623 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2624 total_scanned += sc.nr_scanned; 2625 2626 if (nr_slab == 0 && !zone_reclaimable(zone)) 2627 zone->all_unreclaimable = 1; 2628 } 2629 2630 /* 2631 * If we've done a decent amount of scanning and 2632 * the reclaim ratio is low, start doing writepage 2633 * even in laptop mode 2634 */ 2635 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2636 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2637 sc.may_writepage = 1; 2638 2639 if (zone->all_unreclaimable) { 2640 if (end_zone && end_zone == i) 2641 end_zone--; 2642 continue; 2643 } 2644 2645 if (!zone_watermark_ok_safe(zone, order, 2646 high_wmark_pages(zone), end_zone, 0)) { 2647 all_zones_ok = 0; 2648 /* 2649 * We are still under min water mark. This 2650 * means that we have a GFP_ATOMIC allocation 2651 * failure risk. Hurry up! 2652 */ 2653 if (!zone_watermark_ok_safe(zone, order, 2654 min_wmark_pages(zone), end_zone, 0)) 2655 has_under_min_watermark_zone = 1; 2656 } else { 2657 /* 2658 * If a zone reaches its high watermark, 2659 * consider it to be no longer congested. It's 2660 * possible there are dirty pages backed by 2661 * congested BDIs but as pressure is relieved, 2662 * spectulatively avoid congestion waits 2663 */ 2664 zone_clear_flag(zone, ZONE_CONGESTED); 2665 if (i <= *classzone_idx) 2666 balanced += zone->present_pages; 2667 } 2668 2669 } 2670 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2671 break; /* kswapd: all done */ 2672 /* 2673 * OK, kswapd is getting into trouble. Take a nap, then take 2674 * another pass across the zones. 2675 */ 2676 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2677 if (has_under_min_watermark_zone) 2678 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2679 else 2680 congestion_wait(BLK_RW_ASYNC, HZ/10); 2681 } 2682 2683 /* 2684 * We do this so kswapd doesn't build up large priorities for 2685 * example when it is freeing in parallel with allocators. It 2686 * matches the direct reclaim path behaviour in terms of impact 2687 * on zone->*_priority. 2688 */ 2689 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2690 break; 2691 } 2692out: 2693 2694 /* 2695 * order-0: All zones must meet high watermark for a balanced node 2696 * high-order: Balanced zones must make up at least 25% of the node 2697 * for the node to be balanced 2698 */ 2699 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2700 cond_resched(); 2701 2702 try_to_freeze(); 2703 2704 /* 2705 * Fragmentation may mean that the system cannot be 2706 * rebalanced for high-order allocations in all zones. 2707 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2708 * it means the zones have been fully scanned and are still 2709 * not balanced. For high-order allocations, there is 2710 * little point trying all over again as kswapd may 2711 * infinite loop. 2712 * 2713 * Instead, recheck all watermarks at order-0 as they 2714 * are the most important. If watermarks are ok, kswapd will go 2715 * back to sleep. High-order users can still perform direct 2716 * reclaim if they wish. 2717 */ 2718 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2719 order = sc.order = 0; 2720 2721 goto loop_again; 2722 } 2723 2724 /* 2725 * If kswapd was reclaiming at a higher order, it has the option of 2726 * sleeping without all zones being balanced. Before it does, it must 2727 * ensure that the watermarks for order-0 on *all* zones are met and 2728 * that the congestion flags are cleared. The congestion flag must 2729 * be cleared as kswapd is the only mechanism that clears the flag 2730 * and it is potentially going to sleep here. 2731 */ 2732 if (order) { 2733 for (i = 0; i <= end_zone; i++) { 2734 struct zone *zone = pgdat->node_zones + i; 2735 2736 if (!populated_zone(zone)) 2737 continue; 2738 2739 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2740 continue; 2741 2742 /* Confirm the zone is balanced for order-0 */ 2743 if (!zone_watermark_ok(zone, 0, 2744 high_wmark_pages(zone), 0, 0)) { 2745 order = sc.order = 0; 2746 goto loop_again; 2747 } 2748 2749 /* If balanced, clear the congested flag */ 2750 zone_clear_flag(zone, ZONE_CONGESTED); 2751 if (i <= *classzone_idx) 2752 balanced += zone->present_pages; 2753 } 2754 } 2755 2756 /* 2757 * Return the order we were reclaiming at so sleeping_prematurely() 2758 * makes a decision on the order we were last reclaiming at. However, 2759 * if another caller entered the allocator slow path while kswapd 2760 * was awake, order will remain at the higher level 2761 */ 2762 *classzone_idx = end_zone; 2763 return order; 2764} 2765 2766static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2767{ 2768 long remaining = 0; 2769 DEFINE_WAIT(wait); 2770 2771 if (freezing(current) || kthread_should_stop()) 2772 return; 2773 2774 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2775 2776 /* Try to sleep for a short interval */ 2777 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2778 remaining = schedule_timeout(HZ/10); 2779 finish_wait(&pgdat->kswapd_wait, &wait); 2780 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2781 } 2782 2783 /* 2784 * After a short sleep, check if it was a premature sleep. If not, then 2785 * go fully to sleep until explicitly woken up. 2786 */ 2787 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2788 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2789 2790 /* 2791 * vmstat counters are not perfectly accurate and the estimated 2792 * value for counters such as NR_FREE_PAGES can deviate from the 2793 * true value by nr_online_cpus * threshold. To avoid the zone 2794 * watermarks being breached while under pressure, we reduce the 2795 * per-cpu vmstat threshold while kswapd is awake and restore 2796 * them before going back to sleep. 2797 */ 2798 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2799 schedule(); 2800 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2801 } else { 2802 if (remaining) 2803 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2804 else 2805 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2806 } 2807 finish_wait(&pgdat->kswapd_wait, &wait); 2808} 2809 2810/* 2811 * The background pageout daemon, started as a kernel thread 2812 * from the init process. 2813 * 2814 * This basically trickles out pages so that we have _some_ 2815 * free memory available even if there is no other activity 2816 * that frees anything up. This is needed for things like routing 2817 * etc, where we otherwise might have all activity going on in 2818 * asynchronous contexts that cannot page things out. 2819 * 2820 * If there are applications that are active memory-allocators 2821 * (most normal use), this basically shouldn't matter. 2822 */ 2823static int kswapd(void *p) 2824{ 2825 unsigned long order, new_order; 2826 unsigned balanced_order; 2827 int classzone_idx, new_classzone_idx; 2828 int balanced_classzone_idx; 2829 pg_data_t *pgdat = (pg_data_t*)p; 2830 struct task_struct *tsk = current; 2831 2832 struct reclaim_state reclaim_state = { 2833 .reclaimed_slab = 0, 2834 }; 2835 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2836 2837 lockdep_set_current_reclaim_state(GFP_KERNEL); 2838 2839 if (!cpumask_empty(cpumask)) 2840 set_cpus_allowed_ptr(tsk, cpumask); 2841 current->reclaim_state = &reclaim_state; 2842 2843 /* 2844 * Tell the memory management that we're a "memory allocator", 2845 * and that if we need more memory we should get access to it 2846 * regardless (see "__alloc_pages()"). "kswapd" should 2847 * never get caught in the normal page freeing logic. 2848 * 2849 * (Kswapd normally doesn't need memory anyway, but sometimes 2850 * you need a small amount of memory in order to be able to 2851 * page out something else, and this flag essentially protects 2852 * us from recursively trying to free more memory as we're 2853 * trying to free the first piece of memory in the first place). 2854 */ 2855 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2856 set_freezable(); 2857 2858 order = new_order = 0; 2859 balanced_order = 0; 2860 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; 2861 balanced_classzone_idx = classzone_idx; 2862 for ( ; ; ) { 2863 int ret; 2864 2865 /* 2866 * If the last balance_pgdat was unsuccessful it's unlikely a 2867 * new request of a similar or harder type will succeed soon 2868 * so consider going to sleep on the basis we reclaimed at 2869 */ 2870 if (balanced_classzone_idx >= new_classzone_idx && 2871 balanced_order == new_order) { 2872 new_order = pgdat->kswapd_max_order; 2873 new_classzone_idx = pgdat->classzone_idx; 2874 pgdat->kswapd_max_order = 0; 2875 pgdat->classzone_idx = pgdat->nr_zones - 1; 2876 } 2877 2878 if (order < new_order || classzone_idx > new_classzone_idx) { 2879 /* 2880 * Don't sleep if someone wants a larger 'order' 2881 * allocation or has tigher zone constraints 2882 */ 2883 order = new_order; 2884 classzone_idx = new_classzone_idx; 2885 } else { 2886 kswapd_try_to_sleep(pgdat, balanced_order, 2887 balanced_classzone_idx); 2888 order = pgdat->kswapd_max_order; 2889 classzone_idx = pgdat->classzone_idx; 2890 pgdat->kswapd_max_order = 0; 2891 pgdat->classzone_idx = pgdat->nr_zones - 1; 2892 } 2893 2894 ret = try_to_freeze(); 2895 if (kthread_should_stop()) 2896 break; 2897 2898 /* 2899 * We can speed up thawing tasks if we don't call balance_pgdat 2900 * after returning from the refrigerator 2901 */ 2902 if (!ret) { 2903 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2904 balanced_classzone_idx = classzone_idx; 2905 balanced_order = balance_pgdat(pgdat, order, 2906 &balanced_classzone_idx); 2907 } 2908 } 2909 return 0; 2910} 2911 2912/* 2913 * A zone is low on free memory, so wake its kswapd task to service it. 2914 */ 2915void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2916{ 2917 pg_data_t *pgdat; 2918 2919 if (!populated_zone(zone)) 2920 return; 2921 2922 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2923 return; 2924 pgdat = zone->zone_pgdat; 2925 if (pgdat->kswapd_max_order < order) { 2926 pgdat->kswapd_max_order = order; 2927 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2928 } 2929 if (!waitqueue_active(&pgdat->kswapd_wait)) 2930 return; 2931 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2932 return; 2933 2934 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2935 wake_up_interruptible(&pgdat->kswapd_wait); 2936} 2937 2938/* 2939 * The reclaimable count would be mostly accurate. 2940 * The less reclaimable pages may be 2941 * - mlocked pages, which will be moved to unevictable list when encountered 2942 * - mapped pages, which may require several travels to be reclaimed 2943 * - dirty pages, which is not "instantly" reclaimable 2944 */ 2945unsigned long global_reclaimable_pages(void) 2946{ 2947 int nr; 2948 2949 nr = global_page_state(NR_ACTIVE_FILE) + 2950 global_page_state(NR_INACTIVE_FILE); 2951 2952 if (nr_swap_pages > 0) 2953 nr += global_page_state(NR_ACTIVE_ANON) + 2954 global_page_state(NR_INACTIVE_ANON); 2955 2956 return nr; 2957} 2958 2959unsigned long zone_reclaimable_pages(struct zone *zone) 2960{ 2961 int nr; 2962 2963 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2964 zone_page_state(zone, NR_INACTIVE_FILE); 2965 2966 if (nr_swap_pages > 0) 2967 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2968 zone_page_state(zone, NR_INACTIVE_ANON); 2969 2970 return nr; 2971} 2972 2973#ifdef CONFIG_HIBERNATION 2974/* 2975 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2976 * freed pages. 2977 * 2978 * Rather than trying to age LRUs the aim is to preserve the overall 2979 * LRU order by reclaiming preferentially 2980 * inactive > active > active referenced > active mapped 2981 */ 2982unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2983{ 2984 struct reclaim_state reclaim_state; 2985 struct scan_control sc = { 2986 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2987 .may_swap = 1, 2988 .may_unmap = 1, 2989 .may_writepage = 1, 2990 .nr_to_reclaim = nr_to_reclaim, 2991 .hibernation_mode = 1, 2992 .order = 0, 2993 }; 2994 struct shrink_control shrink = { 2995 .gfp_mask = sc.gfp_mask, 2996 }; 2997 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2998 struct task_struct *p = current; 2999 unsigned long nr_reclaimed; 3000 3001 p->flags |= PF_MEMALLOC; 3002 lockdep_set_current_reclaim_state(sc.gfp_mask); 3003 reclaim_state.reclaimed_slab = 0; 3004 p->reclaim_state = &reclaim_state; 3005 3006 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 3007 3008 p->reclaim_state = NULL; 3009 lockdep_clear_current_reclaim_state(); 3010 p->flags &= ~PF_MEMALLOC; 3011 3012 return nr_reclaimed; 3013} 3014#endif /* CONFIG_HIBERNATION */ 3015 3016/* It's optimal to keep kswapds on the same CPUs as their memory, but 3017 not required for correctness. So if the last cpu in a node goes 3018 away, we get changed to run anywhere: as the first one comes back, 3019 restore their cpu bindings. */ 3020static int __devinit cpu_callback(struct notifier_block *nfb, 3021 unsigned long action, void *hcpu) 3022{ 3023 int nid; 3024 3025 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 3026 for_each_node_state(nid, N_HIGH_MEMORY) { 3027 pg_data_t *pgdat = NODE_DATA(nid); 3028 const struct cpumask *mask; 3029 3030 mask = cpumask_of_node(pgdat->node_id); 3031 3032 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 3033 /* One of our CPUs online: restore mask */ 3034 set_cpus_allowed_ptr(pgdat->kswapd, mask); 3035 } 3036 } 3037 return NOTIFY_OK; 3038} 3039 3040/* 3041 * This kswapd start function will be called by init and node-hot-add. 3042 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 3043 */ 3044int kswapd_run(int nid) 3045{ 3046 pg_data_t *pgdat = NODE_DATA(nid); 3047 int ret = 0; 3048 3049 if (pgdat->kswapd) 3050 return 0; 3051 3052 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 3053 if (IS_ERR(pgdat->kswapd)) { 3054 /* failure at boot is fatal */ 3055 BUG_ON(system_state == SYSTEM_BOOTING); 3056 printk("Failed to start kswapd on node %d\n",nid); 3057 ret = -1; 3058 } 3059 return ret; 3060} 3061 3062/* 3063 * Called by memory hotplug when all memory in a node is offlined. 3064 */ 3065void kswapd_stop(int nid) 3066{ 3067 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 3068 3069 if (kswapd) 3070 kthread_stop(kswapd); 3071} 3072 3073static int __init kswapd_init(void) 3074{ 3075 int nid; 3076 3077 swap_setup(); 3078 for_each_node_state(nid, N_HIGH_MEMORY) 3079 kswapd_run(nid); 3080 hotcpu_notifier(cpu_callback, 0); 3081 return 0; 3082} 3083 3084module_init(kswapd_init) 3085 3086#ifdef CONFIG_NUMA 3087/* 3088 * Zone reclaim mode 3089 * 3090 * If non-zero call zone_reclaim when the number of free pages falls below 3091 * the watermarks. 3092 */ 3093int zone_reclaim_mode __read_mostly; 3094 3095#define RECLAIM_OFF 0 3096#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 3097#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 3098#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 3099 3100/* 3101 * Priority for ZONE_RECLAIM. This determines the fraction of pages 3102 * of a node considered for each zone_reclaim. 4 scans 1/16th of 3103 * a zone. 3104 */ 3105#define ZONE_RECLAIM_PRIORITY 4 3106 3107/* 3108 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 3109 * occur. 3110 */ 3111int sysctl_min_unmapped_ratio = 1; 3112 3113/* 3114 * If the number of slab pages in a zone grows beyond this percentage then 3115 * slab reclaim needs to occur. 3116 */ 3117int sysctl_min_slab_ratio = 5; 3118 3119static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 3120{ 3121 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 3122 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 3123 zone_page_state(zone, NR_ACTIVE_FILE); 3124 3125 /* 3126 * It's possible for there to be more file mapped pages than 3127 * accounted for by the pages on the file LRU lists because 3128 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 3129 */ 3130 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 3131} 3132 3133/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 3134static long zone_pagecache_reclaimable(struct zone *zone) 3135{ 3136 long nr_pagecache_reclaimable; 3137 long delta = 0; 3138 3139 /* 3140 * If RECLAIM_SWAP is set, then all file pages are considered 3141 * potentially reclaimable. Otherwise, we have to worry about 3142 * pages like swapcache and zone_unmapped_file_pages() provides 3143 * a better estimate 3144 */ 3145 if (zone_reclaim_mode & RECLAIM_SWAP) 3146 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 3147 else 3148 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 3149 3150 /* If we can't clean pages, remove dirty pages from consideration */ 3151 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 3152 delta += zone_page_state(zone, NR_FILE_DIRTY); 3153 3154 /* Watch for any possible underflows due to delta */ 3155 if (unlikely(delta > nr_pagecache_reclaimable)) 3156 delta = nr_pagecache_reclaimable; 3157 3158 return nr_pagecache_reclaimable - delta; 3159} 3160 3161/* 3162 * Try to free up some pages from this zone through reclaim. 3163 */ 3164static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3165{ 3166 /* Minimum pages needed in order to stay on node */ 3167 const unsigned long nr_pages = 1 << order; 3168 struct task_struct *p = current; 3169 struct reclaim_state reclaim_state; 3170 int priority; 3171 struct scan_control sc = { 3172 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 3173 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 3174 .may_swap = 1, 3175 .nr_to_reclaim = max_t(unsigned long, nr_pages, 3176 SWAP_CLUSTER_MAX), 3177 .gfp_mask = gfp_mask, 3178 .order = order, 3179 }; 3180 struct shrink_control shrink = { 3181 .gfp_mask = sc.gfp_mask, 3182 }; 3183 unsigned long nr_slab_pages0, nr_slab_pages1; 3184 3185 cond_resched(); 3186 /* 3187 * We need to be able to allocate from the reserves for RECLAIM_SWAP 3188 * and we also need to be able to write out pages for RECLAIM_WRITE 3189 * and RECLAIM_SWAP. 3190 */ 3191 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 3192 lockdep_set_current_reclaim_state(gfp_mask); 3193 reclaim_state.reclaimed_slab = 0; 3194 p->reclaim_state = &reclaim_state; 3195 3196 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 3197 /* 3198 * Free memory by calling shrink zone with increasing 3199 * priorities until we have enough memory freed. 3200 */ 3201 priority = ZONE_RECLAIM_PRIORITY; 3202 do { 3203 shrink_zone(priority, zone, &sc); 3204 priority--; 3205 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 3206 } 3207 3208 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3209 if (nr_slab_pages0 > zone->min_slab_pages) { 3210 /* 3211 * shrink_slab() does not currently allow us to determine how 3212 * many pages were freed in this zone. So we take the current 3213 * number of slab pages and shake the slab until it is reduced 3214 * by the same nr_pages that we used for reclaiming unmapped 3215 * pages. 3216 * 3217 * Note that shrink_slab will free memory on all zones and may 3218 * take a long time. 3219 */ 3220 for (;;) { 3221 unsigned long lru_pages = zone_reclaimable_pages(zone); 3222 3223 /* No reclaimable slab or very low memory pressure */ 3224 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) 3225 break; 3226 3227 /* Freed enough memory */ 3228 nr_slab_pages1 = zone_page_state(zone, 3229 NR_SLAB_RECLAIMABLE); 3230 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3231 break; 3232 } 3233 3234 /* 3235 * Update nr_reclaimed by the number of slab pages we 3236 * reclaimed from this zone. 3237 */ 3238 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3239 if (nr_slab_pages1 < nr_slab_pages0) 3240 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3241 } 3242 3243 p->reclaim_state = NULL; 3244 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3245 lockdep_clear_current_reclaim_state(); 3246 return sc.nr_reclaimed >= nr_pages; 3247} 3248 3249int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3250{ 3251 int node_id; 3252 int ret; 3253 3254 /* 3255 * Zone reclaim reclaims unmapped file backed pages and 3256 * slab pages if we are over the defined limits. 3257 * 3258 * A small portion of unmapped file backed pages is needed for 3259 * file I/O otherwise pages read by file I/O will be immediately 3260 * thrown out if the zone is overallocated. So we do not reclaim 3261 * if less than a specified percentage of the zone is used by 3262 * unmapped file backed pages. 3263 */ 3264 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3265 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3266 return ZONE_RECLAIM_FULL; 3267 3268 if (zone->all_unreclaimable) 3269 return ZONE_RECLAIM_FULL; 3270 3271 /* 3272 * Do not scan if the allocation should not be delayed. 3273 */ 3274 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3275 return ZONE_RECLAIM_NOSCAN; 3276 3277 /* 3278 * Only run zone reclaim on the local zone or on zones that do not 3279 * have associated processors. This will favor the local processor 3280 * over remote processors and spread off node memory allocations 3281 * as wide as possible. 3282 */ 3283 node_id = zone_to_nid(zone); 3284 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3285 return ZONE_RECLAIM_NOSCAN; 3286 3287 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3288 return ZONE_RECLAIM_NOSCAN; 3289 3290 ret = __zone_reclaim(zone, gfp_mask, order); 3291 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3292 3293 if (!ret) 3294 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3295 3296 return ret; 3297} 3298#endif 3299 3300/* 3301 * page_evictable - test whether a page is evictable 3302 * @page: the page to test 3303 * @vma: the VMA in which the page is or will be mapped, may be NULL 3304 * 3305 * Test whether page is evictable--i.e., should be placed on active/inactive 3306 * lists vs unevictable list. The vma argument is !NULL when called from the 3307 * fault path to determine how to instantate a new page. 3308 * 3309 * Reasons page might not be evictable: 3310 * (1) page's mapping marked unevictable 3311 * (2) page is part of an mlocked VMA 3312 * 3313 */ 3314int page_evictable(struct page *page, struct vm_area_struct *vma) 3315{ 3316 3317 if (mapping_unevictable(page_mapping(page))) 3318 return 0; 3319 3320 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3321 return 0; 3322 3323 return 1; 3324} 3325 3326/** 3327 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3328 * @page: page to check evictability and move to appropriate lru list 3329 * @zone: zone page is in 3330 * 3331 * Checks a page for evictability and moves the page to the appropriate 3332 * zone lru list. 3333 * 3334 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3335 * have PageUnevictable set. 3336 */ 3337static void check_move_unevictable_page(struct page *page, struct zone *zone) 3338{ 3339 VM_BUG_ON(PageActive(page)); 3340 3341retry: 3342 ClearPageUnevictable(page); 3343 if (page_evictable(page, NULL)) { 3344 enum lru_list l = page_lru_base_type(page); 3345 3346 __dec_zone_state(zone, NR_UNEVICTABLE); 3347 list_move(&page->lru, &zone->lru[l].list); 3348 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3349 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3350 __count_vm_event(UNEVICTABLE_PGRESCUED); 3351 } else { 3352 /* 3353 * rotate unevictable list 3354 */ 3355 SetPageUnevictable(page); 3356 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3357 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3358 if (page_evictable(page, NULL)) 3359 goto retry; 3360 } 3361} 3362 3363/** 3364 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3365 * @mapping: struct address_space to scan for evictable pages 3366 * 3367 * Scan all pages in mapping. Check unevictable pages for 3368 * evictability and move them to the appropriate zone lru list. 3369 */ 3370void scan_mapping_unevictable_pages(struct address_space *mapping) 3371{ 3372 pgoff_t next = 0; 3373 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3374 PAGE_CACHE_SHIFT; 3375 struct zone *zone; 3376 struct pagevec pvec; 3377 3378 if (mapping->nrpages == 0) 3379 return; 3380 3381 pagevec_init(&pvec, 0); 3382 while (next < end && 3383 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3384 int i; 3385 int pg_scanned = 0; 3386 3387 zone = NULL; 3388 3389 for (i = 0; i < pagevec_count(&pvec); i++) { 3390 struct page *page = pvec.pages[i]; 3391 pgoff_t page_index = page->index; 3392 struct zone *pagezone = page_zone(page); 3393 3394 pg_scanned++; 3395 if (page_index > next) 3396 next = page_index; 3397 next++; 3398 3399 if (pagezone != zone) { 3400 if (zone) 3401 spin_unlock_irq(&zone->lru_lock); 3402 zone = pagezone; 3403 spin_lock_irq(&zone->lru_lock); 3404 } 3405 3406 if (PageLRU(page) && PageUnevictable(page)) 3407 check_move_unevictable_page(page, zone); 3408 } 3409 if (zone) 3410 spin_unlock_irq(&zone->lru_lock); 3411 pagevec_release(&pvec); 3412 3413 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3414 } 3415 3416} 3417 3418/** 3419 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3420 * @zone - zone of which to scan the unevictable list 3421 * 3422 * Scan @zone's unevictable LRU lists to check for pages that have become 3423 * evictable. Move those that have to @zone's inactive list where they 3424 * become candidates for reclaim, unless shrink_inactive_zone() decides 3425 * to reactivate them. Pages that are still unevictable are rotated 3426 * back onto @zone's unevictable list. 3427 */ 3428#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3429static void scan_zone_unevictable_pages(struct zone *zone) 3430{ 3431 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3432 unsigned long scan; 3433 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3434 3435 while (nr_to_scan > 0) { 3436 unsigned long batch_size = min(nr_to_scan, 3437 SCAN_UNEVICTABLE_BATCH_SIZE); 3438 3439 spin_lock_irq(&zone->lru_lock); 3440 for (scan = 0; scan < batch_size; scan++) { 3441 struct page *page = lru_to_page(l_unevictable); 3442 3443 if (!trylock_page(page)) 3444 continue; 3445 3446 prefetchw_prev_lru_page(page, l_unevictable, flags); 3447 3448 if (likely(PageLRU(page) && PageUnevictable(page))) 3449 check_move_unevictable_page(page, zone); 3450 3451 unlock_page(page); 3452 } 3453 spin_unlock_irq(&zone->lru_lock); 3454 3455 nr_to_scan -= batch_size; 3456 } 3457} 3458 3459 3460/** 3461 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3462 * 3463 * A really big hammer: scan all zones' unevictable LRU lists to check for 3464 * pages that have become evictable. Move those back to the zones' 3465 * inactive list where they become candidates for reclaim. 3466 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3467 * and we add swap to the system. As such, it runs in the context of a task 3468 * that has possibly/probably made some previously unevictable pages 3469 * evictable. 3470 */ 3471static void scan_all_zones_unevictable_pages(void) 3472{ 3473 struct zone *zone; 3474 3475 for_each_zone(zone) { 3476 scan_zone_unevictable_pages(zone); 3477 } 3478} 3479 3480/* 3481 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3482 * all nodes' unevictable lists for evictable pages 3483 */ 3484unsigned long scan_unevictable_pages; 3485 3486int scan_unevictable_handler(struct ctl_table *table, int write, 3487 void __user *buffer, 3488 size_t *length, loff_t *ppos) 3489{ 3490 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3491 3492 if (write && *(unsigned long *)table->data) 3493 scan_all_zones_unevictable_pages(); 3494 3495 scan_unevictable_pages = 0; 3496 return 0; 3497} 3498 3499#ifdef CONFIG_NUMA 3500/* 3501 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3502 * a specified node's per zone unevictable lists for evictable pages. 3503 */ 3504 3505static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3506 struct sysdev_attribute *attr, 3507 char *buf) 3508{ 3509 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3510} 3511 3512static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3513 struct sysdev_attribute *attr, 3514 const char *buf, size_t count) 3515{ 3516 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3517 struct zone *zone; 3518 unsigned long res; 3519 unsigned long req = strict_strtoul(buf, 10, &res); 3520 3521 if (!req) 3522 return 1; /* zero is no-op */ 3523 3524 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3525 if (!populated_zone(zone)) 3526 continue; 3527 scan_zone_unevictable_pages(zone); 3528 } 3529 return 1; 3530} 3531 3532 3533static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3534 read_scan_unevictable_node, 3535 write_scan_unevictable_node); 3536 3537int scan_unevictable_register_node(struct node *node) 3538{ 3539 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3540} 3541 3542void scan_unevictable_unregister_node(struct node *node) 3543{ 3544 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3545} 3546#endif 3547