vmscan.c revision 4111304dab198c687bc60f2e235a9f7ee92c47c8
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 /* 107 * The memory cgroup that hit its limit and as a result is the 108 * primary target of this reclaim invocation. 109 */ 110 struct mem_cgroup *target_mem_cgroup; 111 112 /* 113 * Nodemask of nodes allowed by the caller. If NULL, all nodes 114 * are scanned. 115 */ 116 nodemask_t *nodemask; 117}; 118 119struct mem_cgroup_zone { 120 struct mem_cgroup *mem_cgroup; 121 struct zone *zone; 122}; 123 124#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 125 126#ifdef ARCH_HAS_PREFETCH 127#define prefetch_prev_lru_page(_page, _base, _field) \ 128 do { \ 129 if ((_page)->lru.prev != _base) { \ 130 struct page *prev; \ 131 \ 132 prev = lru_to_page(&(_page->lru)); \ 133 prefetch(&prev->_field); \ 134 } \ 135 } while (0) 136#else 137#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 138#endif 139 140#ifdef ARCH_HAS_PREFETCHW 141#define prefetchw_prev_lru_page(_page, _base, _field) \ 142 do { \ 143 if ((_page)->lru.prev != _base) { \ 144 struct page *prev; \ 145 \ 146 prev = lru_to_page(&(_page->lru)); \ 147 prefetchw(&prev->_field); \ 148 } \ 149 } while (0) 150#else 151#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 152#endif 153 154/* 155 * From 0 .. 100. Higher means more swappy. 156 */ 157int vm_swappiness = 60; 158long vm_total_pages; /* The total number of pages which the VM controls */ 159 160static LIST_HEAD(shrinker_list); 161static DECLARE_RWSEM(shrinker_rwsem); 162 163#ifdef CONFIG_CGROUP_MEM_RES_CTLR 164static bool global_reclaim(struct scan_control *sc) 165{ 166 return !sc->target_mem_cgroup; 167} 168 169static bool scanning_global_lru(struct mem_cgroup_zone *mz) 170{ 171 return !mz->mem_cgroup; 172} 173#else 174static bool global_reclaim(struct scan_control *sc) 175{ 176 return true; 177} 178 179static bool scanning_global_lru(struct mem_cgroup_zone *mz) 180{ 181 return true; 182} 183#endif 184 185static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz) 186{ 187 if (!scanning_global_lru(mz)) 188 return mem_cgroup_get_reclaim_stat(mz->mem_cgroup, mz->zone); 189 190 return &mz->zone->reclaim_stat; 191} 192 193static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone *mz, 194 enum lru_list lru) 195{ 196 if (!scanning_global_lru(mz)) 197 return mem_cgroup_zone_nr_lru_pages(mz->mem_cgroup, 198 zone_to_nid(mz->zone), 199 zone_idx(mz->zone), 200 BIT(lru)); 201 202 return zone_page_state(mz->zone, NR_LRU_BASE + lru); 203} 204 205 206/* 207 * Add a shrinker callback to be called from the vm 208 */ 209void register_shrinker(struct shrinker *shrinker) 210{ 211 atomic_long_set(&shrinker->nr_in_batch, 0); 212 down_write(&shrinker_rwsem); 213 list_add_tail(&shrinker->list, &shrinker_list); 214 up_write(&shrinker_rwsem); 215} 216EXPORT_SYMBOL(register_shrinker); 217 218/* 219 * Remove one 220 */ 221void unregister_shrinker(struct shrinker *shrinker) 222{ 223 down_write(&shrinker_rwsem); 224 list_del(&shrinker->list); 225 up_write(&shrinker_rwsem); 226} 227EXPORT_SYMBOL(unregister_shrinker); 228 229static inline int do_shrinker_shrink(struct shrinker *shrinker, 230 struct shrink_control *sc, 231 unsigned long nr_to_scan) 232{ 233 sc->nr_to_scan = nr_to_scan; 234 return (*shrinker->shrink)(shrinker, sc); 235} 236 237#define SHRINK_BATCH 128 238/* 239 * Call the shrink functions to age shrinkable caches 240 * 241 * Here we assume it costs one seek to replace a lru page and that it also 242 * takes a seek to recreate a cache object. With this in mind we age equal 243 * percentages of the lru and ageable caches. This should balance the seeks 244 * generated by these structures. 245 * 246 * If the vm encountered mapped pages on the LRU it increase the pressure on 247 * slab to avoid swapping. 248 * 249 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 250 * 251 * `lru_pages' represents the number of on-LRU pages in all the zones which 252 * are eligible for the caller's allocation attempt. It is used for balancing 253 * slab reclaim versus page reclaim. 254 * 255 * Returns the number of slab objects which we shrunk. 256 */ 257unsigned long shrink_slab(struct shrink_control *shrink, 258 unsigned long nr_pages_scanned, 259 unsigned long lru_pages) 260{ 261 struct shrinker *shrinker; 262 unsigned long ret = 0; 263 264 if (nr_pages_scanned == 0) 265 nr_pages_scanned = SWAP_CLUSTER_MAX; 266 267 if (!down_read_trylock(&shrinker_rwsem)) { 268 /* Assume we'll be able to shrink next time */ 269 ret = 1; 270 goto out; 271 } 272 273 list_for_each_entry(shrinker, &shrinker_list, list) { 274 unsigned long long delta; 275 long total_scan; 276 long max_pass; 277 int shrink_ret = 0; 278 long nr; 279 long new_nr; 280 long batch_size = shrinker->batch ? shrinker->batch 281 : SHRINK_BATCH; 282 283 max_pass = do_shrinker_shrink(shrinker, shrink, 0); 284 if (max_pass <= 0) 285 continue; 286 287 /* 288 * copy the current shrinker scan count into a local variable 289 * and zero it so that other concurrent shrinker invocations 290 * don't also do this scanning work. 291 */ 292 nr = atomic_long_xchg(&shrinker->nr_in_batch, 0); 293 294 total_scan = nr; 295 delta = (4 * nr_pages_scanned) / shrinker->seeks; 296 delta *= max_pass; 297 do_div(delta, lru_pages + 1); 298 total_scan += delta; 299 if (total_scan < 0) { 300 printk(KERN_ERR "shrink_slab: %pF negative objects to " 301 "delete nr=%ld\n", 302 shrinker->shrink, total_scan); 303 total_scan = max_pass; 304 } 305 306 /* 307 * We need to avoid excessive windup on filesystem shrinkers 308 * due to large numbers of GFP_NOFS allocations causing the 309 * shrinkers to return -1 all the time. This results in a large 310 * nr being built up so when a shrink that can do some work 311 * comes along it empties the entire cache due to nr >>> 312 * max_pass. This is bad for sustaining a working set in 313 * memory. 314 * 315 * Hence only allow the shrinker to scan the entire cache when 316 * a large delta change is calculated directly. 317 */ 318 if (delta < max_pass / 4) 319 total_scan = min(total_scan, max_pass / 2); 320 321 /* 322 * Avoid risking looping forever due to too large nr value: 323 * never try to free more than twice the estimate number of 324 * freeable entries. 325 */ 326 if (total_scan > max_pass * 2) 327 total_scan = max_pass * 2; 328 329 trace_mm_shrink_slab_start(shrinker, shrink, nr, 330 nr_pages_scanned, lru_pages, 331 max_pass, delta, total_scan); 332 333 while (total_scan >= batch_size) { 334 int nr_before; 335 336 nr_before = do_shrinker_shrink(shrinker, shrink, 0); 337 shrink_ret = do_shrinker_shrink(shrinker, shrink, 338 batch_size); 339 if (shrink_ret == -1) 340 break; 341 if (shrink_ret < nr_before) 342 ret += nr_before - shrink_ret; 343 count_vm_events(SLABS_SCANNED, batch_size); 344 total_scan -= batch_size; 345 346 cond_resched(); 347 } 348 349 /* 350 * move the unused scan count back into the shrinker in a 351 * manner that handles concurrent updates. If we exhausted the 352 * scan, there is no need to do an update. 353 */ 354 if (total_scan > 0) 355 new_nr = atomic_long_add_return(total_scan, 356 &shrinker->nr_in_batch); 357 else 358 new_nr = atomic_long_read(&shrinker->nr_in_batch); 359 360 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); 361 } 362 up_read(&shrinker_rwsem); 363out: 364 cond_resched(); 365 return ret; 366} 367 368static void set_reclaim_mode(int priority, struct scan_control *sc, 369 bool sync) 370{ 371 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 372 373 /* 374 * Initially assume we are entering either lumpy reclaim or 375 * reclaim/compaction.Depending on the order, we will either set the 376 * sync mode or just reclaim order-0 pages later. 377 */ 378 if (COMPACTION_BUILD) 379 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 380 else 381 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 382 383 /* 384 * Avoid using lumpy reclaim or reclaim/compaction if possible by 385 * restricting when its set to either costly allocations or when 386 * under memory pressure 387 */ 388 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 389 sc->reclaim_mode |= syncmode; 390 else if (sc->order && priority < DEF_PRIORITY - 2) 391 sc->reclaim_mode |= syncmode; 392 else 393 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 394} 395 396static void reset_reclaim_mode(struct scan_control *sc) 397{ 398 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 399} 400 401static inline int is_page_cache_freeable(struct page *page) 402{ 403 /* 404 * A freeable page cache page is referenced only by the caller 405 * that isolated the page, the page cache radix tree and 406 * optional buffer heads at page->private. 407 */ 408 return page_count(page) - page_has_private(page) == 2; 409} 410 411static int may_write_to_queue(struct backing_dev_info *bdi, 412 struct scan_control *sc) 413{ 414 if (current->flags & PF_SWAPWRITE) 415 return 1; 416 if (!bdi_write_congested(bdi)) 417 return 1; 418 if (bdi == current->backing_dev_info) 419 return 1; 420 421 /* lumpy reclaim for hugepage often need a lot of write */ 422 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 423 return 1; 424 return 0; 425} 426 427/* 428 * We detected a synchronous write error writing a page out. Probably 429 * -ENOSPC. We need to propagate that into the address_space for a subsequent 430 * fsync(), msync() or close(). 431 * 432 * The tricky part is that after writepage we cannot touch the mapping: nothing 433 * prevents it from being freed up. But we have a ref on the page and once 434 * that page is locked, the mapping is pinned. 435 * 436 * We're allowed to run sleeping lock_page() here because we know the caller has 437 * __GFP_FS. 438 */ 439static void handle_write_error(struct address_space *mapping, 440 struct page *page, int error) 441{ 442 lock_page(page); 443 if (page_mapping(page) == mapping) 444 mapping_set_error(mapping, error); 445 unlock_page(page); 446} 447 448/* possible outcome of pageout() */ 449typedef enum { 450 /* failed to write page out, page is locked */ 451 PAGE_KEEP, 452 /* move page to the active list, page is locked */ 453 PAGE_ACTIVATE, 454 /* page has been sent to the disk successfully, page is unlocked */ 455 PAGE_SUCCESS, 456 /* page is clean and locked */ 457 PAGE_CLEAN, 458} pageout_t; 459 460/* 461 * pageout is called by shrink_page_list() for each dirty page. 462 * Calls ->writepage(). 463 */ 464static pageout_t pageout(struct page *page, struct address_space *mapping, 465 struct scan_control *sc) 466{ 467 /* 468 * If the page is dirty, only perform writeback if that write 469 * will be non-blocking. To prevent this allocation from being 470 * stalled by pagecache activity. But note that there may be 471 * stalls if we need to run get_block(). We could test 472 * PagePrivate for that. 473 * 474 * If this process is currently in __generic_file_aio_write() against 475 * this page's queue, we can perform writeback even if that 476 * will block. 477 * 478 * If the page is swapcache, write it back even if that would 479 * block, for some throttling. This happens by accident, because 480 * swap_backing_dev_info is bust: it doesn't reflect the 481 * congestion state of the swapdevs. Easy to fix, if needed. 482 */ 483 if (!is_page_cache_freeable(page)) 484 return PAGE_KEEP; 485 if (!mapping) { 486 /* 487 * Some data journaling orphaned pages can have 488 * page->mapping == NULL while being dirty with clean buffers. 489 */ 490 if (page_has_private(page)) { 491 if (try_to_free_buffers(page)) { 492 ClearPageDirty(page); 493 printk("%s: orphaned page\n", __func__); 494 return PAGE_CLEAN; 495 } 496 } 497 return PAGE_KEEP; 498 } 499 if (mapping->a_ops->writepage == NULL) 500 return PAGE_ACTIVATE; 501 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 502 return PAGE_KEEP; 503 504 if (clear_page_dirty_for_io(page)) { 505 int res; 506 struct writeback_control wbc = { 507 .sync_mode = WB_SYNC_NONE, 508 .nr_to_write = SWAP_CLUSTER_MAX, 509 .range_start = 0, 510 .range_end = LLONG_MAX, 511 .for_reclaim = 1, 512 }; 513 514 SetPageReclaim(page); 515 res = mapping->a_ops->writepage(page, &wbc); 516 if (res < 0) 517 handle_write_error(mapping, page, res); 518 if (res == AOP_WRITEPAGE_ACTIVATE) { 519 ClearPageReclaim(page); 520 return PAGE_ACTIVATE; 521 } 522 523 if (!PageWriteback(page)) { 524 /* synchronous write or broken a_ops? */ 525 ClearPageReclaim(page); 526 } 527 trace_mm_vmscan_writepage(page, 528 trace_reclaim_flags(page, sc->reclaim_mode)); 529 inc_zone_page_state(page, NR_VMSCAN_WRITE); 530 return PAGE_SUCCESS; 531 } 532 533 return PAGE_CLEAN; 534} 535 536/* 537 * Same as remove_mapping, but if the page is removed from the mapping, it 538 * gets returned with a refcount of 0. 539 */ 540static int __remove_mapping(struct address_space *mapping, struct page *page) 541{ 542 BUG_ON(!PageLocked(page)); 543 BUG_ON(mapping != page_mapping(page)); 544 545 spin_lock_irq(&mapping->tree_lock); 546 /* 547 * The non racy check for a busy page. 548 * 549 * Must be careful with the order of the tests. When someone has 550 * a ref to the page, it may be possible that they dirty it then 551 * drop the reference. So if PageDirty is tested before page_count 552 * here, then the following race may occur: 553 * 554 * get_user_pages(&page); 555 * [user mapping goes away] 556 * write_to(page); 557 * !PageDirty(page) [good] 558 * SetPageDirty(page); 559 * put_page(page); 560 * !page_count(page) [good, discard it] 561 * 562 * [oops, our write_to data is lost] 563 * 564 * Reversing the order of the tests ensures such a situation cannot 565 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 566 * load is not satisfied before that of page->_count. 567 * 568 * Note that if SetPageDirty is always performed via set_page_dirty, 569 * and thus under tree_lock, then this ordering is not required. 570 */ 571 if (!page_freeze_refs(page, 2)) 572 goto cannot_free; 573 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 574 if (unlikely(PageDirty(page))) { 575 page_unfreeze_refs(page, 2); 576 goto cannot_free; 577 } 578 579 if (PageSwapCache(page)) { 580 swp_entry_t swap = { .val = page_private(page) }; 581 __delete_from_swap_cache(page); 582 spin_unlock_irq(&mapping->tree_lock); 583 swapcache_free(swap, page); 584 } else { 585 void (*freepage)(struct page *); 586 587 freepage = mapping->a_ops->freepage; 588 589 __delete_from_page_cache(page); 590 spin_unlock_irq(&mapping->tree_lock); 591 mem_cgroup_uncharge_cache_page(page); 592 593 if (freepage != NULL) 594 freepage(page); 595 } 596 597 return 1; 598 599cannot_free: 600 spin_unlock_irq(&mapping->tree_lock); 601 return 0; 602} 603 604/* 605 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 606 * someone else has a ref on the page, abort and return 0. If it was 607 * successfully detached, return 1. Assumes the caller has a single ref on 608 * this page. 609 */ 610int remove_mapping(struct address_space *mapping, struct page *page) 611{ 612 if (__remove_mapping(mapping, page)) { 613 /* 614 * Unfreezing the refcount with 1 rather than 2 effectively 615 * drops the pagecache ref for us without requiring another 616 * atomic operation. 617 */ 618 page_unfreeze_refs(page, 1); 619 return 1; 620 } 621 return 0; 622} 623 624/** 625 * putback_lru_page - put previously isolated page onto appropriate LRU list 626 * @page: page to be put back to appropriate lru list 627 * 628 * Add previously isolated @page to appropriate LRU list. 629 * Page may still be unevictable for other reasons. 630 * 631 * lru_lock must not be held, interrupts must be enabled. 632 */ 633void putback_lru_page(struct page *page) 634{ 635 int lru; 636 int active = !!TestClearPageActive(page); 637 int was_unevictable = PageUnevictable(page); 638 639 VM_BUG_ON(PageLRU(page)); 640 641redo: 642 ClearPageUnevictable(page); 643 644 if (page_evictable(page, NULL)) { 645 /* 646 * For evictable pages, we can use the cache. 647 * In event of a race, worst case is we end up with an 648 * unevictable page on [in]active list. 649 * We know how to handle that. 650 */ 651 lru = active + page_lru_base_type(page); 652 lru_cache_add_lru(page, lru); 653 } else { 654 /* 655 * Put unevictable pages directly on zone's unevictable 656 * list. 657 */ 658 lru = LRU_UNEVICTABLE; 659 add_page_to_unevictable_list(page); 660 /* 661 * When racing with an mlock or AS_UNEVICTABLE clearing 662 * (page is unlocked) make sure that if the other thread 663 * does not observe our setting of PG_lru and fails 664 * isolation/check_move_unevictable_page, 665 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move 666 * the page back to the evictable list. 667 * 668 * The other side is TestClearPageMlocked() or shmem_lock(). 669 */ 670 smp_mb(); 671 } 672 673 /* 674 * page's status can change while we move it among lru. If an evictable 675 * page is on unevictable list, it never be freed. To avoid that, 676 * check after we added it to the list, again. 677 */ 678 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 679 if (!isolate_lru_page(page)) { 680 put_page(page); 681 goto redo; 682 } 683 /* This means someone else dropped this page from LRU 684 * So, it will be freed or putback to LRU again. There is 685 * nothing to do here. 686 */ 687 } 688 689 if (was_unevictable && lru != LRU_UNEVICTABLE) 690 count_vm_event(UNEVICTABLE_PGRESCUED); 691 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 692 count_vm_event(UNEVICTABLE_PGCULLED); 693 694 put_page(page); /* drop ref from isolate */ 695} 696 697enum page_references { 698 PAGEREF_RECLAIM, 699 PAGEREF_RECLAIM_CLEAN, 700 PAGEREF_KEEP, 701 PAGEREF_ACTIVATE, 702}; 703 704static enum page_references page_check_references(struct page *page, 705 struct mem_cgroup_zone *mz, 706 struct scan_control *sc) 707{ 708 int referenced_ptes, referenced_page; 709 unsigned long vm_flags; 710 711 referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags); 712 referenced_page = TestClearPageReferenced(page); 713 714 /* Lumpy reclaim - ignore references */ 715 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 716 return PAGEREF_RECLAIM; 717 718 /* 719 * Mlock lost the isolation race with us. Let try_to_unmap() 720 * move the page to the unevictable list. 721 */ 722 if (vm_flags & VM_LOCKED) 723 return PAGEREF_RECLAIM; 724 725 if (referenced_ptes) { 726 if (PageAnon(page)) 727 return PAGEREF_ACTIVATE; 728 /* 729 * All mapped pages start out with page table 730 * references from the instantiating fault, so we need 731 * to look twice if a mapped file page is used more 732 * than once. 733 * 734 * Mark it and spare it for another trip around the 735 * inactive list. Another page table reference will 736 * lead to its activation. 737 * 738 * Note: the mark is set for activated pages as well 739 * so that recently deactivated but used pages are 740 * quickly recovered. 741 */ 742 SetPageReferenced(page); 743 744 if (referenced_page || referenced_ptes > 1) 745 return PAGEREF_ACTIVATE; 746 747 /* 748 * Activate file-backed executable pages after first usage. 749 */ 750 if (vm_flags & VM_EXEC) 751 return PAGEREF_ACTIVATE; 752 753 return PAGEREF_KEEP; 754 } 755 756 /* Reclaim if clean, defer dirty pages to writeback */ 757 if (referenced_page && !PageSwapBacked(page)) 758 return PAGEREF_RECLAIM_CLEAN; 759 760 return PAGEREF_RECLAIM; 761} 762 763/* 764 * shrink_page_list() returns the number of reclaimed pages 765 */ 766static unsigned long shrink_page_list(struct list_head *page_list, 767 struct mem_cgroup_zone *mz, 768 struct scan_control *sc, 769 int priority, 770 unsigned long *ret_nr_dirty, 771 unsigned long *ret_nr_writeback) 772{ 773 LIST_HEAD(ret_pages); 774 LIST_HEAD(free_pages); 775 int pgactivate = 0; 776 unsigned long nr_dirty = 0; 777 unsigned long nr_congested = 0; 778 unsigned long nr_reclaimed = 0; 779 unsigned long nr_writeback = 0; 780 781 cond_resched(); 782 783 while (!list_empty(page_list)) { 784 enum page_references references; 785 struct address_space *mapping; 786 struct page *page; 787 int may_enter_fs; 788 789 cond_resched(); 790 791 page = lru_to_page(page_list); 792 list_del(&page->lru); 793 794 if (!trylock_page(page)) 795 goto keep; 796 797 VM_BUG_ON(PageActive(page)); 798 VM_BUG_ON(page_zone(page) != mz->zone); 799 800 sc->nr_scanned++; 801 802 if (unlikely(!page_evictable(page, NULL))) 803 goto cull_mlocked; 804 805 if (!sc->may_unmap && page_mapped(page)) 806 goto keep_locked; 807 808 /* Double the slab pressure for mapped and swapcache pages */ 809 if (page_mapped(page) || PageSwapCache(page)) 810 sc->nr_scanned++; 811 812 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 813 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 814 815 if (PageWriteback(page)) { 816 nr_writeback++; 817 /* 818 * Synchronous reclaim cannot queue pages for 819 * writeback due to the possibility of stack overflow 820 * but if it encounters a page under writeback, wait 821 * for the IO to complete. 822 */ 823 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 824 may_enter_fs) 825 wait_on_page_writeback(page); 826 else { 827 unlock_page(page); 828 goto keep_lumpy; 829 } 830 } 831 832 references = page_check_references(page, mz, sc); 833 switch (references) { 834 case PAGEREF_ACTIVATE: 835 goto activate_locked; 836 case PAGEREF_KEEP: 837 goto keep_locked; 838 case PAGEREF_RECLAIM: 839 case PAGEREF_RECLAIM_CLEAN: 840 ; /* try to reclaim the page below */ 841 } 842 843 /* 844 * Anonymous process memory has backing store? 845 * Try to allocate it some swap space here. 846 */ 847 if (PageAnon(page) && !PageSwapCache(page)) { 848 if (!(sc->gfp_mask & __GFP_IO)) 849 goto keep_locked; 850 if (!add_to_swap(page)) 851 goto activate_locked; 852 may_enter_fs = 1; 853 } 854 855 mapping = page_mapping(page); 856 857 /* 858 * The page is mapped into the page tables of one or more 859 * processes. Try to unmap it here. 860 */ 861 if (page_mapped(page) && mapping) { 862 switch (try_to_unmap(page, TTU_UNMAP)) { 863 case SWAP_FAIL: 864 goto activate_locked; 865 case SWAP_AGAIN: 866 goto keep_locked; 867 case SWAP_MLOCK: 868 goto cull_mlocked; 869 case SWAP_SUCCESS: 870 ; /* try to free the page below */ 871 } 872 } 873 874 if (PageDirty(page)) { 875 nr_dirty++; 876 877 /* 878 * Only kswapd can writeback filesystem pages to 879 * avoid risk of stack overflow but do not writeback 880 * unless under significant pressure. 881 */ 882 if (page_is_file_cache(page) && 883 (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) { 884 /* 885 * Immediately reclaim when written back. 886 * Similar in principal to deactivate_page() 887 * except we already have the page isolated 888 * and know it's dirty 889 */ 890 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); 891 SetPageReclaim(page); 892 893 goto keep_locked; 894 } 895 896 if (references == PAGEREF_RECLAIM_CLEAN) 897 goto keep_locked; 898 if (!may_enter_fs) 899 goto keep_locked; 900 if (!sc->may_writepage) 901 goto keep_locked; 902 903 /* Page is dirty, try to write it out here */ 904 switch (pageout(page, mapping, sc)) { 905 case PAGE_KEEP: 906 nr_congested++; 907 goto keep_locked; 908 case PAGE_ACTIVATE: 909 goto activate_locked; 910 case PAGE_SUCCESS: 911 if (PageWriteback(page)) 912 goto keep_lumpy; 913 if (PageDirty(page)) 914 goto keep; 915 916 /* 917 * A synchronous write - probably a ramdisk. Go 918 * ahead and try to reclaim the page. 919 */ 920 if (!trylock_page(page)) 921 goto keep; 922 if (PageDirty(page) || PageWriteback(page)) 923 goto keep_locked; 924 mapping = page_mapping(page); 925 case PAGE_CLEAN: 926 ; /* try to free the page below */ 927 } 928 } 929 930 /* 931 * If the page has buffers, try to free the buffer mappings 932 * associated with this page. If we succeed we try to free 933 * the page as well. 934 * 935 * We do this even if the page is PageDirty(). 936 * try_to_release_page() does not perform I/O, but it is 937 * possible for a page to have PageDirty set, but it is actually 938 * clean (all its buffers are clean). This happens if the 939 * buffers were written out directly, with submit_bh(). ext3 940 * will do this, as well as the blockdev mapping. 941 * try_to_release_page() will discover that cleanness and will 942 * drop the buffers and mark the page clean - it can be freed. 943 * 944 * Rarely, pages can have buffers and no ->mapping. These are 945 * the pages which were not successfully invalidated in 946 * truncate_complete_page(). We try to drop those buffers here 947 * and if that worked, and the page is no longer mapped into 948 * process address space (page_count == 1) it can be freed. 949 * Otherwise, leave the page on the LRU so it is swappable. 950 */ 951 if (page_has_private(page)) { 952 if (!try_to_release_page(page, sc->gfp_mask)) 953 goto activate_locked; 954 if (!mapping && page_count(page) == 1) { 955 unlock_page(page); 956 if (put_page_testzero(page)) 957 goto free_it; 958 else { 959 /* 960 * rare race with speculative reference. 961 * the speculative reference will free 962 * this page shortly, so we may 963 * increment nr_reclaimed here (and 964 * leave it off the LRU). 965 */ 966 nr_reclaimed++; 967 continue; 968 } 969 } 970 } 971 972 if (!mapping || !__remove_mapping(mapping, page)) 973 goto keep_locked; 974 975 /* 976 * At this point, we have no other references and there is 977 * no way to pick any more up (removed from LRU, removed 978 * from pagecache). Can use non-atomic bitops now (and 979 * we obviously don't have to worry about waking up a process 980 * waiting on the page lock, because there are no references. 981 */ 982 __clear_page_locked(page); 983free_it: 984 nr_reclaimed++; 985 986 /* 987 * Is there need to periodically free_page_list? It would 988 * appear not as the counts should be low 989 */ 990 list_add(&page->lru, &free_pages); 991 continue; 992 993cull_mlocked: 994 if (PageSwapCache(page)) 995 try_to_free_swap(page); 996 unlock_page(page); 997 putback_lru_page(page); 998 reset_reclaim_mode(sc); 999 continue; 1000 1001activate_locked: 1002 /* Not a candidate for swapping, so reclaim swap space. */ 1003 if (PageSwapCache(page) && vm_swap_full()) 1004 try_to_free_swap(page); 1005 VM_BUG_ON(PageActive(page)); 1006 SetPageActive(page); 1007 pgactivate++; 1008keep_locked: 1009 unlock_page(page); 1010keep: 1011 reset_reclaim_mode(sc); 1012keep_lumpy: 1013 list_add(&page->lru, &ret_pages); 1014 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 1015 } 1016 1017 /* 1018 * Tag a zone as congested if all the dirty pages encountered were 1019 * backed by a congested BDI. In this case, reclaimers should just 1020 * back off and wait for congestion to clear because further reclaim 1021 * will encounter the same problem 1022 */ 1023 if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc)) 1024 zone_set_flag(mz->zone, ZONE_CONGESTED); 1025 1026 free_hot_cold_page_list(&free_pages, 1); 1027 1028 list_splice(&ret_pages, page_list); 1029 count_vm_events(PGACTIVATE, pgactivate); 1030 *ret_nr_dirty += nr_dirty; 1031 *ret_nr_writeback += nr_writeback; 1032 return nr_reclaimed; 1033} 1034 1035/* 1036 * Attempt to remove the specified page from its LRU. Only take this page 1037 * if it is of the appropriate PageActive status. Pages which are being 1038 * freed elsewhere are also ignored. 1039 * 1040 * page: page to consider 1041 * mode: one of the LRU isolation modes defined above 1042 * 1043 * returns 0 on success, -ve errno on failure. 1044 */ 1045int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file) 1046{ 1047 bool all_lru_mode; 1048 int ret = -EINVAL; 1049 1050 /* Only take pages on the LRU. */ 1051 if (!PageLRU(page)) 1052 return ret; 1053 1054 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) == 1055 (ISOLATE_ACTIVE|ISOLATE_INACTIVE); 1056 1057 /* 1058 * When checking the active state, we need to be sure we are 1059 * dealing with comparible boolean values. Take the logical not 1060 * of each. 1061 */ 1062 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE)) 1063 return ret; 1064 1065 if (!all_lru_mode && !!page_is_file_cache(page) != file) 1066 return ret; 1067 1068 /* 1069 * When this function is being called for lumpy reclaim, we 1070 * initially look into all LRU pages, active, inactive and 1071 * unevictable; only give shrink_page_list evictable pages. 1072 */ 1073 if (PageUnevictable(page)) 1074 return ret; 1075 1076 ret = -EBUSY; 1077 1078 /* 1079 * To minimise LRU disruption, the caller can indicate that it only 1080 * wants to isolate pages it will be able to operate on without 1081 * blocking - clean pages for the most part. 1082 * 1083 * ISOLATE_CLEAN means that only clean pages should be isolated. This 1084 * is used by reclaim when it is cannot write to backing storage 1085 * 1086 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages 1087 * that it is possible to migrate without blocking 1088 */ 1089 if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { 1090 /* All the caller can do on PageWriteback is block */ 1091 if (PageWriteback(page)) 1092 return ret; 1093 1094 if (PageDirty(page)) { 1095 struct address_space *mapping; 1096 1097 /* ISOLATE_CLEAN means only clean pages */ 1098 if (mode & ISOLATE_CLEAN) 1099 return ret; 1100 1101 /* 1102 * Only pages without mappings or that have a 1103 * ->migratepage callback are possible to migrate 1104 * without blocking 1105 */ 1106 mapping = page_mapping(page); 1107 if (mapping && !mapping->a_ops->migratepage) 1108 return ret; 1109 } 1110 } 1111 1112 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) 1113 return ret; 1114 1115 if (likely(get_page_unless_zero(page))) { 1116 /* 1117 * Be careful not to clear PageLRU until after we're 1118 * sure the page is not being freed elsewhere -- the 1119 * page release code relies on it. 1120 */ 1121 ClearPageLRU(page); 1122 ret = 0; 1123 } 1124 1125 return ret; 1126} 1127 1128/* 1129 * zone->lru_lock is heavily contended. Some of the functions that 1130 * shrink the lists perform better by taking out a batch of pages 1131 * and working on them outside the LRU lock. 1132 * 1133 * For pagecache intensive workloads, this function is the hottest 1134 * spot in the kernel (apart from copy_*_user functions). 1135 * 1136 * Appropriate locks must be held before calling this function. 1137 * 1138 * @nr_to_scan: The number of pages to look through on the list. 1139 * @src: The LRU list to pull pages off. 1140 * @dst: The temp list to put pages on to. 1141 * @scanned: The number of pages that were scanned. 1142 * @order: The caller's attempted allocation order 1143 * @mode: One of the LRU isolation modes 1144 * @file: True [1] if isolating file [!anon] pages 1145 * 1146 * returns how many pages were moved onto *@dst. 1147 */ 1148static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1149 struct list_head *src, struct list_head *dst, 1150 unsigned long *scanned, int order, isolate_mode_t mode, 1151 int file) 1152{ 1153 unsigned long nr_taken = 0; 1154 unsigned long nr_lumpy_taken = 0; 1155 unsigned long nr_lumpy_dirty = 0; 1156 unsigned long nr_lumpy_failed = 0; 1157 unsigned long scan; 1158 1159 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1160 struct page *page; 1161 unsigned long pfn; 1162 unsigned long end_pfn; 1163 unsigned long page_pfn; 1164 int zone_id; 1165 1166 page = lru_to_page(src); 1167 prefetchw_prev_lru_page(page, src, flags); 1168 1169 VM_BUG_ON(!PageLRU(page)); 1170 1171 switch (__isolate_lru_page(page, mode, file)) { 1172 case 0: 1173 mem_cgroup_lru_del(page); 1174 list_move(&page->lru, dst); 1175 nr_taken += hpage_nr_pages(page); 1176 break; 1177 1178 case -EBUSY: 1179 /* else it is being freed elsewhere */ 1180 list_move(&page->lru, src); 1181 continue; 1182 1183 default: 1184 BUG(); 1185 } 1186 1187 if (!order) 1188 continue; 1189 1190 /* 1191 * Attempt to take all pages in the order aligned region 1192 * surrounding the tag page. Only take those pages of 1193 * the same active state as that tag page. We may safely 1194 * round the target page pfn down to the requested order 1195 * as the mem_map is guaranteed valid out to MAX_ORDER, 1196 * where that page is in a different zone we will detect 1197 * it from its zone id and abort this block scan. 1198 */ 1199 zone_id = page_zone_id(page); 1200 page_pfn = page_to_pfn(page); 1201 pfn = page_pfn & ~((1 << order) - 1); 1202 end_pfn = pfn + (1 << order); 1203 for (; pfn < end_pfn; pfn++) { 1204 struct page *cursor_page; 1205 1206 /* The target page is in the block, ignore it. */ 1207 if (unlikely(pfn == page_pfn)) 1208 continue; 1209 1210 /* Avoid holes within the zone. */ 1211 if (unlikely(!pfn_valid_within(pfn))) 1212 break; 1213 1214 cursor_page = pfn_to_page(pfn); 1215 1216 /* Check that we have not crossed a zone boundary. */ 1217 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1218 break; 1219 1220 /* 1221 * If we don't have enough swap space, reclaiming of 1222 * anon page which don't already have a swap slot is 1223 * pointless. 1224 */ 1225 if (nr_swap_pages <= 0 && PageSwapBacked(cursor_page) && 1226 !PageSwapCache(cursor_page)) 1227 break; 1228 1229 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1230 unsigned int isolated_pages; 1231 1232 mem_cgroup_lru_del(cursor_page); 1233 list_move(&cursor_page->lru, dst); 1234 isolated_pages = hpage_nr_pages(cursor_page); 1235 nr_taken += isolated_pages; 1236 nr_lumpy_taken += isolated_pages; 1237 if (PageDirty(cursor_page)) 1238 nr_lumpy_dirty += isolated_pages; 1239 scan++; 1240 pfn += isolated_pages - 1; 1241 } else { 1242 /* 1243 * Check if the page is freed already. 1244 * 1245 * We can't use page_count() as that 1246 * requires compound_head and we don't 1247 * have a pin on the page here. If a 1248 * page is tail, we may or may not 1249 * have isolated the head, so assume 1250 * it's not free, it'd be tricky to 1251 * track the head status without a 1252 * page pin. 1253 */ 1254 if (!PageTail(cursor_page) && 1255 !atomic_read(&cursor_page->_count)) 1256 continue; 1257 break; 1258 } 1259 } 1260 1261 /* If we break out of the loop above, lumpy reclaim failed */ 1262 if (pfn < end_pfn) 1263 nr_lumpy_failed++; 1264 } 1265 1266 *scanned = scan; 1267 1268 trace_mm_vmscan_lru_isolate(order, 1269 nr_to_scan, scan, 1270 nr_taken, 1271 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1272 mode, file); 1273 return nr_taken; 1274} 1275 1276static unsigned long isolate_pages(unsigned long nr, struct mem_cgroup_zone *mz, 1277 struct list_head *dst, 1278 unsigned long *scanned, int order, 1279 isolate_mode_t mode, int active, int file) 1280{ 1281 struct lruvec *lruvec; 1282 int lru = LRU_BASE; 1283 1284 lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup); 1285 if (active) 1286 lru += LRU_ACTIVE; 1287 if (file) 1288 lru += LRU_FILE; 1289 return isolate_lru_pages(nr, &lruvec->lists[lru], dst, 1290 scanned, order, mode, file); 1291} 1292 1293/* 1294 * clear_active_flags() is a helper for shrink_active_list(), clearing 1295 * any active bits from the pages in the list. 1296 */ 1297static unsigned long clear_active_flags(struct list_head *page_list, 1298 unsigned int *count) 1299{ 1300 int nr_active = 0; 1301 int lru; 1302 struct page *page; 1303 1304 list_for_each_entry(page, page_list, lru) { 1305 int numpages = hpage_nr_pages(page); 1306 lru = page_lru_base_type(page); 1307 if (PageActive(page)) { 1308 lru += LRU_ACTIVE; 1309 ClearPageActive(page); 1310 nr_active += numpages; 1311 } 1312 if (count) 1313 count[lru] += numpages; 1314 } 1315 1316 return nr_active; 1317} 1318 1319/** 1320 * isolate_lru_page - tries to isolate a page from its LRU list 1321 * @page: page to isolate from its LRU list 1322 * 1323 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1324 * vmstat statistic corresponding to whatever LRU list the page was on. 1325 * 1326 * Returns 0 if the page was removed from an LRU list. 1327 * Returns -EBUSY if the page was not on an LRU list. 1328 * 1329 * The returned page will have PageLRU() cleared. If it was found on 1330 * the active list, it will have PageActive set. If it was found on 1331 * the unevictable list, it will have the PageUnevictable bit set. That flag 1332 * may need to be cleared by the caller before letting the page go. 1333 * 1334 * The vmstat statistic corresponding to the list on which the page was 1335 * found will be decremented. 1336 * 1337 * Restrictions: 1338 * (1) Must be called with an elevated refcount on the page. This is a 1339 * fundamentnal difference from isolate_lru_pages (which is called 1340 * without a stable reference). 1341 * (2) the lru_lock must not be held. 1342 * (3) interrupts must be enabled. 1343 */ 1344int isolate_lru_page(struct page *page) 1345{ 1346 int ret = -EBUSY; 1347 1348 VM_BUG_ON(!page_count(page)); 1349 1350 if (PageLRU(page)) { 1351 struct zone *zone = page_zone(page); 1352 1353 spin_lock_irq(&zone->lru_lock); 1354 if (PageLRU(page)) { 1355 int lru = page_lru(page); 1356 ret = 0; 1357 get_page(page); 1358 ClearPageLRU(page); 1359 1360 del_page_from_lru_list(zone, page, lru); 1361 } 1362 spin_unlock_irq(&zone->lru_lock); 1363 } 1364 return ret; 1365} 1366 1367/* 1368 * Are there way too many processes in the direct reclaim path already? 1369 */ 1370static int too_many_isolated(struct zone *zone, int file, 1371 struct scan_control *sc) 1372{ 1373 unsigned long inactive, isolated; 1374 1375 if (current_is_kswapd()) 1376 return 0; 1377 1378 if (!global_reclaim(sc)) 1379 return 0; 1380 1381 if (file) { 1382 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1383 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1384 } else { 1385 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1386 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1387 } 1388 1389 return isolated > inactive; 1390} 1391 1392/* 1393 * TODO: Try merging with migrations version of putback_lru_pages 1394 */ 1395static noinline_for_stack void 1396putback_lru_pages(struct mem_cgroup_zone *mz, struct scan_control *sc, 1397 unsigned long nr_anon, unsigned long nr_file, 1398 struct list_head *page_list) 1399{ 1400 struct page *page; 1401 LIST_HEAD(pages_to_free); 1402 struct zone *zone = mz->zone; 1403 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); 1404 1405 /* 1406 * Put back any unfreeable pages. 1407 */ 1408 spin_lock(&zone->lru_lock); 1409 while (!list_empty(page_list)) { 1410 int lru; 1411 page = lru_to_page(page_list); 1412 VM_BUG_ON(PageLRU(page)); 1413 list_del(&page->lru); 1414 if (unlikely(!page_evictable(page, NULL))) { 1415 spin_unlock_irq(&zone->lru_lock); 1416 putback_lru_page(page); 1417 spin_lock_irq(&zone->lru_lock); 1418 continue; 1419 } 1420 SetPageLRU(page); 1421 lru = page_lru(page); 1422 add_page_to_lru_list(zone, page, lru); 1423 if (is_active_lru(lru)) { 1424 int file = is_file_lru(lru); 1425 int numpages = hpage_nr_pages(page); 1426 reclaim_stat->recent_rotated[file] += numpages; 1427 } 1428 if (put_page_testzero(page)) { 1429 __ClearPageLRU(page); 1430 __ClearPageActive(page); 1431 del_page_from_lru_list(zone, page, lru); 1432 1433 if (unlikely(PageCompound(page))) { 1434 spin_unlock_irq(&zone->lru_lock); 1435 (*get_compound_page_dtor(page))(page); 1436 spin_lock_irq(&zone->lru_lock); 1437 } else 1438 list_add(&page->lru, &pages_to_free); 1439 } 1440 } 1441 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1442 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1443 1444 spin_unlock_irq(&zone->lru_lock); 1445 free_hot_cold_page_list(&pages_to_free, 1); 1446} 1447 1448static noinline_for_stack void 1449update_isolated_counts(struct mem_cgroup_zone *mz, 1450 struct scan_control *sc, 1451 unsigned long *nr_anon, 1452 unsigned long *nr_file, 1453 struct list_head *isolated_list) 1454{ 1455 unsigned long nr_active; 1456 struct zone *zone = mz->zone; 1457 unsigned int count[NR_LRU_LISTS] = { 0, }; 1458 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); 1459 1460 nr_active = clear_active_flags(isolated_list, count); 1461 __count_vm_events(PGDEACTIVATE, nr_active); 1462 1463 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1464 -count[LRU_ACTIVE_FILE]); 1465 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1466 -count[LRU_INACTIVE_FILE]); 1467 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1468 -count[LRU_ACTIVE_ANON]); 1469 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1470 -count[LRU_INACTIVE_ANON]); 1471 1472 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1473 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1474 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1475 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1476 1477 reclaim_stat->recent_scanned[0] += *nr_anon; 1478 reclaim_stat->recent_scanned[1] += *nr_file; 1479} 1480 1481/* 1482 * Returns true if a direct reclaim should wait on pages under writeback. 1483 * 1484 * If we are direct reclaiming for contiguous pages and we do not reclaim 1485 * everything in the list, try again and wait for writeback IO to complete. 1486 * This will stall high-order allocations noticeably. Only do that when really 1487 * need to free the pages under high memory pressure. 1488 */ 1489static inline bool should_reclaim_stall(unsigned long nr_taken, 1490 unsigned long nr_freed, 1491 int priority, 1492 struct scan_control *sc) 1493{ 1494 int lumpy_stall_priority; 1495 1496 /* kswapd should not stall on sync IO */ 1497 if (current_is_kswapd()) 1498 return false; 1499 1500 /* Only stall on lumpy reclaim */ 1501 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1502 return false; 1503 1504 /* If we have reclaimed everything on the isolated list, no stall */ 1505 if (nr_freed == nr_taken) 1506 return false; 1507 1508 /* 1509 * For high-order allocations, there are two stall thresholds. 1510 * High-cost allocations stall immediately where as lower 1511 * order allocations such as stacks require the scanning 1512 * priority to be much higher before stalling. 1513 */ 1514 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1515 lumpy_stall_priority = DEF_PRIORITY; 1516 else 1517 lumpy_stall_priority = DEF_PRIORITY / 3; 1518 1519 return priority <= lumpy_stall_priority; 1520} 1521 1522/* 1523 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1524 * of reclaimed pages 1525 */ 1526static noinline_for_stack unsigned long 1527shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz, 1528 struct scan_control *sc, int priority, int file) 1529{ 1530 LIST_HEAD(page_list); 1531 unsigned long nr_scanned; 1532 unsigned long nr_reclaimed = 0; 1533 unsigned long nr_taken; 1534 unsigned long nr_anon; 1535 unsigned long nr_file; 1536 unsigned long nr_dirty = 0; 1537 unsigned long nr_writeback = 0; 1538 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE; 1539 struct zone *zone = mz->zone; 1540 1541 while (unlikely(too_many_isolated(zone, file, sc))) { 1542 congestion_wait(BLK_RW_ASYNC, HZ/10); 1543 1544 /* We are about to die and free our memory. Return now. */ 1545 if (fatal_signal_pending(current)) 1546 return SWAP_CLUSTER_MAX; 1547 } 1548 1549 set_reclaim_mode(priority, sc, false); 1550 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 1551 reclaim_mode |= ISOLATE_ACTIVE; 1552 1553 lru_add_drain(); 1554 1555 if (!sc->may_unmap) 1556 reclaim_mode |= ISOLATE_UNMAPPED; 1557 if (!sc->may_writepage) 1558 reclaim_mode |= ISOLATE_CLEAN; 1559 1560 spin_lock_irq(&zone->lru_lock); 1561 1562 nr_taken = isolate_pages(nr_to_scan, mz, &page_list, 1563 &nr_scanned, sc->order, 1564 reclaim_mode, 0, file); 1565 if (global_reclaim(sc)) { 1566 zone->pages_scanned += nr_scanned; 1567 if (current_is_kswapd()) 1568 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1569 nr_scanned); 1570 else 1571 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1572 nr_scanned); 1573 } 1574 1575 if (nr_taken == 0) { 1576 spin_unlock_irq(&zone->lru_lock); 1577 return 0; 1578 } 1579 1580 update_isolated_counts(mz, sc, &nr_anon, &nr_file, &page_list); 1581 1582 spin_unlock_irq(&zone->lru_lock); 1583 1584 nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority, 1585 &nr_dirty, &nr_writeback); 1586 1587 /* Check if we should syncronously wait for writeback */ 1588 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1589 set_reclaim_mode(priority, sc, true); 1590 nr_reclaimed += shrink_page_list(&page_list, mz, sc, 1591 priority, &nr_dirty, &nr_writeback); 1592 } 1593 1594 local_irq_disable(); 1595 if (current_is_kswapd()) 1596 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1597 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1598 1599 putback_lru_pages(mz, sc, nr_anon, nr_file, &page_list); 1600 1601 /* 1602 * If reclaim is isolating dirty pages under writeback, it implies 1603 * that the long-lived page allocation rate is exceeding the page 1604 * laundering rate. Either the global limits are not being effective 1605 * at throttling processes due to the page distribution throughout 1606 * zones or there is heavy usage of a slow backing device. The 1607 * only option is to throttle from reclaim context which is not ideal 1608 * as there is no guarantee the dirtying process is throttled in the 1609 * same way balance_dirty_pages() manages. 1610 * 1611 * This scales the number of dirty pages that must be under writeback 1612 * before throttling depending on priority. It is a simple backoff 1613 * function that has the most effect in the range DEF_PRIORITY to 1614 * DEF_PRIORITY-2 which is the priority reclaim is considered to be 1615 * in trouble and reclaim is considered to be in trouble. 1616 * 1617 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle 1618 * DEF_PRIORITY-1 50% must be PageWriteback 1619 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble 1620 * ... 1621 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any 1622 * isolated page is PageWriteback 1623 */ 1624 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority))) 1625 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); 1626 1627 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1628 zone_idx(zone), 1629 nr_scanned, nr_reclaimed, 1630 priority, 1631 trace_shrink_flags(file, sc->reclaim_mode)); 1632 return nr_reclaimed; 1633} 1634 1635/* 1636 * This moves pages from the active list to the inactive list. 1637 * 1638 * We move them the other way if the page is referenced by one or more 1639 * processes, from rmap. 1640 * 1641 * If the pages are mostly unmapped, the processing is fast and it is 1642 * appropriate to hold zone->lru_lock across the whole operation. But if 1643 * the pages are mapped, the processing is slow (page_referenced()) so we 1644 * should drop zone->lru_lock around each page. It's impossible to balance 1645 * this, so instead we remove the pages from the LRU while processing them. 1646 * It is safe to rely on PG_active against the non-LRU pages in here because 1647 * nobody will play with that bit on a non-LRU page. 1648 * 1649 * The downside is that we have to touch page->_count against each page. 1650 * But we had to alter page->flags anyway. 1651 */ 1652 1653static void move_active_pages_to_lru(struct zone *zone, 1654 struct list_head *list, 1655 struct list_head *pages_to_free, 1656 enum lru_list lru) 1657{ 1658 unsigned long pgmoved = 0; 1659 struct page *page; 1660 1661 if (buffer_heads_over_limit) { 1662 spin_unlock_irq(&zone->lru_lock); 1663 list_for_each_entry(page, list, lru) { 1664 if (page_has_private(page) && trylock_page(page)) { 1665 if (page_has_private(page)) 1666 try_to_release_page(page, 0); 1667 unlock_page(page); 1668 } 1669 } 1670 spin_lock_irq(&zone->lru_lock); 1671 } 1672 1673 while (!list_empty(list)) { 1674 struct lruvec *lruvec; 1675 1676 page = lru_to_page(list); 1677 1678 VM_BUG_ON(PageLRU(page)); 1679 SetPageLRU(page); 1680 1681 lruvec = mem_cgroup_lru_add_list(zone, page, lru); 1682 list_move(&page->lru, &lruvec->lists[lru]); 1683 pgmoved += hpage_nr_pages(page); 1684 1685 if (put_page_testzero(page)) { 1686 __ClearPageLRU(page); 1687 __ClearPageActive(page); 1688 del_page_from_lru_list(zone, page, lru); 1689 1690 if (unlikely(PageCompound(page))) { 1691 spin_unlock_irq(&zone->lru_lock); 1692 (*get_compound_page_dtor(page))(page); 1693 spin_lock_irq(&zone->lru_lock); 1694 } else 1695 list_add(&page->lru, pages_to_free); 1696 } 1697 } 1698 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1699 if (!is_active_lru(lru)) 1700 __count_vm_events(PGDEACTIVATE, pgmoved); 1701} 1702 1703static void shrink_active_list(unsigned long nr_pages, 1704 struct mem_cgroup_zone *mz, 1705 struct scan_control *sc, 1706 int priority, int file) 1707{ 1708 unsigned long nr_taken; 1709 unsigned long pgscanned; 1710 unsigned long vm_flags; 1711 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1712 LIST_HEAD(l_active); 1713 LIST_HEAD(l_inactive); 1714 struct page *page; 1715 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); 1716 unsigned long nr_rotated = 0; 1717 isolate_mode_t reclaim_mode = ISOLATE_ACTIVE; 1718 struct zone *zone = mz->zone; 1719 1720 lru_add_drain(); 1721 1722 if (!sc->may_unmap) 1723 reclaim_mode |= ISOLATE_UNMAPPED; 1724 if (!sc->may_writepage) 1725 reclaim_mode |= ISOLATE_CLEAN; 1726 1727 spin_lock_irq(&zone->lru_lock); 1728 1729 nr_taken = isolate_pages(nr_pages, mz, &l_hold, 1730 &pgscanned, sc->order, 1731 reclaim_mode, 1, file); 1732 1733 if (global_reclaim(sc)) 1734 zone->pages_scanned += pgscanned; 1735 1736 reclaim_stat->recent_scanned[file] += nr_taken; 1737 1738 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1739 if (file) 1740 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1741 else 1742 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1743 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1744 spin_unlock_irq(&zone->lru_lock); 1745 1746 while (!list_empty(&l_hold)) { 1747 cond_resched(); 1748 page = lru_to_page(&l_hold); 1749 list_del(&page->lru); 1750 1751 if (unlikely(!page_evictable(page, NULL))) { 1752 putback_lru_page(page); 1753 continue; 1754 } 1755 1756 if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) { 1757 nr_rotated += hpage_nr_pages(page); 1758 /* 1759 * Identify referenced, file-backed active pages and 1760 * give them one more trip around the active list. So 1761 * that executable code get better chances to stay in 1762 * memory under moderate memory pressure. Anon pages 1763 * are not likely to be evicted by use-once streaming 1764 * IO, plus JVM can create lots of anon VM_EXEC pages, 1765 * so we ignore them here. 1766 */ 1767 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1768 list_add(&page->lru, &l_active); 1769 continue; 1770 } 1771 } 1772 1773 ClearPageActive(page); /* we are de-activating */ 1774 list_add(&page->lru, &l_inactive); 1775 } 1776 1777 /* 1778 * Move pages back to the lru list. 1779 */ 1780 spin_lock_irq(&zone->lru_lock); 1781 /* 1782 * Count referenced pages from currently used mappings as rotated, 1783 * even though only some of them are actually re-activated. This 1784 * helps balance scan pressure between file and anonymous pages in 1785 * get_scan_ratio. 1786 */ 1787 reclaim_stat->recent_rotated[file] += nr_rotated; 1788 1789 move_active_pages_to_lru(zone, &l_active, &l_hold, 1790 LRU_ACTIVE + file * LRU_FILE); 1791 move_active_pages_to_lru(zone, &l_inactive, &l_hold, 1792 LRU_BASE + file * LRU_FILE); 1793 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1794 spin_unlock_irq(&zone->lru_lock); 1795 1796 free_hot_cold_page_list(&l_hold, 1); 1797} 1798 1799#ifdef CONFIG_SWAP 1800static int inactive_anon_is_low_global(struct zone *zone) 1801{ 1802 unsigned long active, inactive; 1803 1804 active = zone_page_state(zone, NR_ACTIVE_ANON); 1805 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1806 1807 if (inactive * zone->inactive_ratio < active) 1808 return 1; 1809 1810 return 0; 1811} 1812 1813/** 1814 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1815 * @zone: zone to check 1816 * @sc: scan control of this context 1817 * 1818 * Returns true if the zone does not have enough inactive anon pages, 1819 * meaning some active anon pages need to be deactivated. 1820 */ 1821static int inactive_anon_is_low(struct mem_cgroup_zone *mz) 1822{ 1823 /* 1824 * If we don't have swap space, anonymous page deactivation 1825 * is pointless. 1826 */ 1827 if (!total_swap_pages) 1828 return 0; 1829 1830 if (!scanning_global_lru(mz)) 1831 return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup, 1832 mz->zone); 1833 1834 return inactive_anon_is_low_global(mz->zone); 1835} 1836#else 1837static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz) 1838{ 1839 return 0; 1840} 1841#endif 1842 1843static int inactive_file_is_low_global(struct zone *zone) 1844{ 1845 unsigned long active, inactive; 1846 1847 active = zone_page_state(zone, NR_ACTIVE_FILE); 1848 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1849 1850 return (active > inactive); 1851} 1852 1853/** 1854 * inactive_file_is_low - check if file pages need to be deactivated 1855 * @mz: memory cgroup and zone to check 1856 * 1857 * When the system is doing streaming IO, memory pressure here 1858 * ensures that active file pages get deactivated, until more 1859 * than half of the file pages are on the inactive list. 1860 * 1861 * Once we get to that situation, protect the system's working 1862 * set from being evicted by disabling active file page aging. 1863 * 1864 * This uses a different ratio than the anonymous pages, because 1865 * the page cache uses a use-once replacement algorithm. 1866 */ 1867static int inactive_file_is_low(struct mem_cgroup_zone *mz) 1868{ 1869 if (!scanning_global_lru(mz)) 1870 return mem_cgroup_inactive_file_is_low(mz->mem_cgroup, 1871 mz->zone); 1872 1873 return inactive_file_is_low_global(mz->zone); 1874} 1875 1876static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file) 1877{ 1878 if (file) 1879 return inactive_file_is_low(mz); 1880 else 1881 return inactive_anon_is_low(mz); 1882} 1883 1884static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1885 struct mem_cgroup_zone *mz, 1886 struct scan_control *sc, int priority) 1887{ 1888 int file = is_file_lru(lru); 1889 1890 if (is_active_lru(lru)) { 1891 if (inactive_list_is_low(mz, file)) 1892 shrink_active_list(nr_to_scan, mz, sc, priority, file); 1893 return 0; 1894 } 1895 1896 return shrink_inactive_list(nr_to_scan, mz, sc, priority, file); 1897} 1898 1899static int vmscan_swappiness(struct mem_cgroup_zone *mz, 1900 struct scan_control *sc) 1901{ 1902 if (global_reclaim(sc)) 1903 return vm_swappiness; 1904 return mem_cgroup_swappiness(mz->mem_cgroup); 1905} 1906 1907/* 1908 * Determine how aggressively the anon and file LRU lists should be 1909 * scanned. The relative value of each set of LRU lists is determined 1910 * by looking at the fraction of the pages scanned we did rotate back 1911 * onto the active list instead of evict. 1912 * 1913 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1914 */ 1915static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc, 1916 unsigned long *nr, int priority) 1917{ 1918 unsigned long anon, file, free; 1919 unsigned long anon_prio, file_prio; 1920 unsigned long ap, fp; 1921 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz); 1922 u64 fraction[2], denominator; 1923 enum lru_list lru; 1924 int noswap = 0; 1925 bool force_scan = false; 1926 1927 /* 1928 * If the zone or memcg is small, nr[l] can be 0. This 1929 * results in no scanning on this priority and a potential 1930 * priority drop. Global direct reclaim can go to the next 1931 * zone and tends to have no problems. Global kswapd is for 1932 * zone balancing and it needs to scan a minimum amount. When 1933 * reclaiming for a memcg, a priority drop can cause high 1934 * latencies, so it's better to scan a minimum amount there as 1935 * well. 1936 */ 1937 if (current_is_kswapd() && mz->zone->all_unreclaimable) 1938 force_scan = true; 1939 if (!global_reclaim(sc)) 1940 force_scan = true; 1941 1942 /* If we have no swap space, do not bother scanning anon pages. */ 1943 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1944 noswap = 1; 1945 fraction[0] = 0; 1946 fraction[1] = 1; 1947 denominator = 1; 1948 goto out; 1949 } 1950 1951 anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) + 1952 zone_nr_lru_pages(mz, LRU_INACTIVE_ANON); 1953 file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) + 1954 zone_nr_lru_pages(mz, LRU_INACTIVE_FILE); 1955 1956 if (global_reclaim(sc)) { 1957 free = zone_page_state(mz->zone, NR_FREE_PAGES); 1958 /* If we have very few page cache pages, 1959 force-scan anon pages. */ 1960 if (unlikely(file + free <= high_wmark_pages(mz->zone))) { 1961 fraction[0] = 1; 1962 fraction[1] = 0; 1963 denominator = 1; 1964 goto out; 1965 } 1966 } 1967 1968 /* 1969 * With swappiness at 100, anonymous and file have the same priority. 1970 * This scanning priority is essentially the inverse of IO cost. 1971 */ 1972 anon_prio = vmscan_swappiness(mz, sc); 1973 file_prio = 200 - vmscan_swappiness(mz, sc); 1974 1975 /* 1976 * OK, so we have swap space and a fair amount of page cache 1977 * pages. We use the recently rotated / recently scanned 1978 * ratios to determine how valuable each cache is. 1979 * 1980 * Because workloads change over time (and to avoid overflow) 1981 * we keep these statistics as a floating average, which ends 1982 * up weighing recent references more than old ones. 1983 * 1984 * anon in [0], file in [1] 1985 */ 1986 spin_lock_irq(&mz->zone->lru_lock); 1987 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1988 reclaim_stat->recent_scanned[0] /= 2; 1989 reclaim_stat->recent_rotated[0] /= 2; 1990 } 1991 1992 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1993 reclaim_stat->recent_scanned[1] /= 2; 1994 reclaim_stat->recent_rotated[1] /= 2; 1995 } 1996 1997 /* 1998 * The amount of pressure on anon vs file pages is inversely 1999 * proportional to the fraction of recently scanned pages on 2000 * each list that were recently referenced and in active use. 2001 */ 2002 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 2003 ap /= reclaim_stat->recent_rotated[0] + 1; 2004 2005 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 2006 fp /= reclaim_stat->recent_rotated[1] + 1; 2007 spin_unlock_irq(&mz->zone->lru_lock); 2008 2009 fraction[0] = ap; 2010 fraction[1] = fp; 2011 denominator = ap + fp + 1; 2012out: 2013 for_each_evictable_lru(lru) { 2014 int file = is_file_lru(lru); 2015 unsigned long scan; 2016 2017 scan = zone_nr_lru_pages(mz, lru); 2018 if (priority || noswap) { 2019 scan >>= priority; 2020 if (!scan && force_scan) 2021 scan = SWAP_CLUSTER_MAX; 2022 scan = div64_u64(scan * fraction[file], denominator); 2023 } 2024 nr[lru] = scan; 2025 } 2026} 2027 2028/* 2029 * Reclaim/compaction depends on a number of pages being freed. To avoid 2030 * disruption to the system, a small number of order-0 pages continue to be 2031 * rotated and reclaimed in the normal fashion. However, by the time we get 2032 * back to the allocator and call try_to_compact_zone(), we ensure that 2033 * there are enough free pages for it to be likely successful 2034 */ 2035static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz, 2036 unsigned long nr_reclaimed, 2037 unsigned long nr_scanned, 2038 struct scan_control *sc) 2039{ 2040 unsigned long pages_for_compaction; 2041 unsigned long inactive_lru_pages; 2042 2043 /* If not in reclaim/compaction mode, stop */ 2044 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 2045 return false; 2046 2047 /* Consider stopping depending on scan and reclaim activity */ 2048 if (sc->gfp_mask & __GFP_REPEAT) { 2049 /* 2050 * For __GFP_REPEAT allocations, stop reclaiming if the 2051 * full LRU list has been scanned and we are still failing 2052 * to reclaim pages. This full LRU scan is potentially 2053 * expensive but a __GFP_REPEAT caller really wants to succeed 2054 */ 2055 if (!nr_reclaimed && !nr_scanned) 2056 return false; 2057 } else { 2058 /* 2059 * For non-__GFP_REPEAT allocations which can presumably 2060 * fail without consequence, stop if we failed to reclaim 2061 * any pages from the last SWAP_CLUSTER_MAX number of 2062 * pages that were scanned. This will return to the 2063 * caller faster at the risk reclaim/compaction and 2064 * the resulting allocation attempt fails 2065 */ 2066 if (!nr_reclaimed) 2067 return false; 2068 } 2069 2070 /* 2071 * If we have not reclaimed enough pages for compaction and the 2072 * inactive lists are large enough, continue reclaiming 2073 */ 2074 pages_for_compaction = (2UL << sc->order); 2075 inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE); 2076 if (nr_swap_pages > 0) 2077 inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON); 2078 if (sc->nr_reclaimed < pages_for_compaction && 2079 inactive_lru_pages > pages_for_compaction) 2080 return true; 2081 2082 /* If compaction would go ahead or the allocation would succeed, stop */ 2083 switch (compaction_suitable(mz->zone, sc->order)) { 2084 case COMPACT_PARTIAL: 2085 case COMPACT_CONTINUE: 2086 return false; 2087 default: 2088 return true; 2089 } 2090} 2091 2092/* 2093 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 2094 */ 2095static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz, 2096 struct scan_control *sc) 2097{ 2098 unsigned long nr[NR_LRU_LISTS]; 2099 unsigned long nr_to_scan; 2100 enum lru_list lru; 2101 unsigned long nr_reclaimed, nr_scanned; 2102 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 2103 struct blk_plug plug; 2104 2105restart: 2106 nr_reclaimed = 0; 2107 nr_scanned = sc->nr_scanned; 2108 get_scan_count(mz, sc, nr, priority); 2109 2110 blk_start_plug(&plug); 2111 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 2112 nr[LRU_INACTIVE_FILE]) { 2113 for_each_evictable_lru(lru) { 2114 if (nr[lru]) { 2115 nr_to_scan = min_t(unsigned long, 2116 nr[lru], SWAP_CLUSTER_MAX); 2117 nr[lru] -= nr_to_scan; 2118 2119 nr_reclaimed += shrink_list(lru, nr_to_scan, 2120 mz, sc, priority); 2121 } 2122 } 2123 /* 2124 * On large memory systems, scan >> priority can become 2125 * really large. This is fine for the starting priority; 2126 * we want to put equal scanning pressure on each zone. 2127 * However, if the VM has a harder time of freeing pages, 2128 * with multiple processes reclaiming pages, the total 2129 * freeing target can get unreasonably large. 2130 */ 2131 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 2132 break; 2133 } 2134 blk_finish_plug(&plug); 2135 sc->nr_reclaimed += nr_reclaimed; 2136 2137 /* 2138 * Even if we did not try to evict anon pages at all, we want to 2139 * rebalance the anon lru active/inactive ratio. 2140 */ 2141 if (inactive_anon_is_low(mz)) 2142 shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0); 2143 2144 /* reclaim/compaction might need reclaim to continue */ 2145 if (should_continue_reclaim(mz, nr_reclaimed, 2146 sc->nr_scanned - nr_scanned, sc)) 2147 goto restart; 2148 2149 throttle_vm_writeout(sc->gfp_mask); 2150} 2151 2152static void shrink_zone(int priority, struct zone *zone, 2153 struct scan_control *sc) 2154{ 2155 struct mem_cgroup *root = sc->target_mem_cgroup; 2156 struct mem_cgroup_reclaim_cookie reclaim = { 2157 .zone = zone, 2158 .priority = priority, 2159 }; 2160 struct mem_cgroup *memcg; 2161 2162 memcg = mem_cgroup_iter(root, NULL, &reclaim); 2163 do { 2164 struct mem_cgroup_zone mz = { 2165 .mem_cgroup = memcg, 2166 .zone = zone, 2167 }; 2168 2169 shrink_mem_cgroup_zone(priority, &mz, sc); 2170 /* 2171 * Limit reclaim has historically picked one memcg and 2172 * scanned it with decreasing priority levels until 2173 * nr_to_reclaim had been reclaimed. This priority 2174 * cycle is thus over after a single memcg. 2175 * 2176 * Direct reclaim and kswapd, on the other hand, have 2177 * to scan all memory cgroups to fulfill the overall 2178 * scan target for the zone. 2179 */ 2180 if (!global_reclaim(sc)) { 2181 mem_cgroup_iter_break(root, memcg); 2182 break; 2183 } 2184 memcg = mem_cgroup_iter(root, memcg, &reclaim); 2185 } while (memcg); 2186} 2187 2188/* Returns true if compaction should go ahead for a high-order request */ 2189static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) 2190{ 2191 unsigned long balance_gap, watermark; 2192 bool watermark_ok; 2193 2194 /* Do not consider compaction for orders reclaim is meant to satisfy */ 2195 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER) 2196 return false; 2197 2198 /* 2199 * Compaction takes time to run and there are potentially other 2200 * callers using the pages just freed. Continue reclaiming until 2201 * there is a buffer of free pages available to give compaction 2202 * a reasonable chance of completing and allocating the page 2203 */ 2204 balance_gap = min(low_wmark_pages(zone), 2205 (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2206 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2207 watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); 2208 watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); 2209 2210 /* 2211 * If compaction is deferred, reclaim up to a point where 2212 * compaction will have a chance of success when re-enabled 2213 */ 2214 if (compaction_deferred(zone)) 2215 return watermark_ok; 2216 2217 /* If compaction is not ready to start, keep reclaiming */ 2218 if (!compaction_suitable(zone, sc->order)) 2219 return false; 2220 2221 return watermark_ok; 2222} 2223 2224/* 2225 * This is the direct reclaim path, for page-allocating processes. We only 2226 * try to reclaim pages from zones which will satisfy the caller's allocation 2227 * request. 2228 * 2229 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 2230 * Because: 2231 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 2232 * allocation or 2233 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 2234 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 2235 * zone defense algorithm. 2236 * 2237 * If a zone is deemed to be full of pinned pages then just give it a light 2238 * scan then give up on it. 2239 * 2240 * This function returns true if a zone is being reclaimed for a costly 2241 * high-order allocation and compaction is ready to begin. This indicates to 2242 * the caller that it should consider retrying the allocation instead of 2243 * further reclaim. 2244 */ 2245static bool shrink_zones(int priority, struct zonelist *zonelist, 2246 struct scan_control *sc) 2247{ 2248 struct zoneref *z; 2249 struct zone *zone; 2250 unsigned long nr_soft_reclaimed; 2251 unsigned long nr_soft_scanned; 2252 bool aborted_reclaim = false; 2253 2254 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2255 gfp_zone(sc->gfp_mask), sc->nodemask) { 2256 if (!populated_zone(zone)) 2257 continue; 2258 /* 2259 * Take care memory controller reclaiming has small influence 2260 * to global LRU. 2261 */ 2262 if (global_reclaim(sc)) { 2263 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2264 continue; 2265 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2266 continue; /* Let kswapd poll it */ 2267 if (COMPACTION_BUILD) { 2268 /* 2269 * If we already have plenty of memory free for 2270 * compaction in this zone, don't free any more. 2271 * Even though compaction is invoked for any 2272 * non-zero order, only frequent costly order 2273 * reclamation is disruptive enough to become a 2274 * noticable problem, like transparent huge page 2275 * allocations. 2276 */ 2277 if (compaction_ready(zone, sc)) { 2278 aborted_reclaim = true; 2279 continue; 2280 } 2281 } 2282 /* 2283 * This steals pages from memory cgroups over softlimit 2284 * and returns the number of reclaimed pages and 2285 * scanned pages. This works for global memory pressure 2286 * and balancing, not for a memcg's limit. 2287 */ 2288 nr_soft_scanned = 0; 2289 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2290 sc->order, sc->gfp_mask, 2291 &nr_soft_scanned); 2292 sc->nr_reclaimed += nr_soft_reclaimed; 2293 sc->nr_scanned += nr_soft_scanned; 2294 /* need some check for avoid more shrink_zone() */ 2295 } 2296 2297 shrink_zone(priority, zone, sc); 2298 } 2299 2300 return aborted_reclaim; 2301} 2302 2303static bool zone_reclaimable(struct zone *zone) 2304{ 2305 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 2306} 2307 2308/* All zones in zonelist are unreclaimable? */ 2309static bool all_unreclaimable(struct zonelist *zonelist, 2310 struct scan_control *sc) 2311{ 2312 struct zoneref *z; 2313 struct zone *zone; 2314 2315 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2316 gfp_zone(sc->gfp_mask), sc->nodemask) { 2317 if (!populated_zone(zone)) 2318 continue; 2319 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2320 continue; 2321 if (!zone->all_unreclaimable) 2322 return false; 2323 } 2324 2325 return true; 2326} 2327 2328/* 2329 * This is the main entry point to direct page reclaim. 2330 * 2331 * If a full scan of the inactive list fails to free enough memory then we 2332 * are "out of memory" and something needs to be killed. 2333 * 2334 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2335 * high - the zone may be full of dirty or under-writeback pages, which this 2336 * caller can't do much about. We kick the writeback threads and take explicit 2337 * naps in the hope that some of these pages can be written. But if the 2338 * allocating task holds filesystem locks which prevent writeout this might not 2339 * work, and the allocation attempt will fail. 2340 * 2341 * returns: 0, if no pages reclaimed 2342 * else, the number of pages reclaimed 2343 */ 2344static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2345 struct scan_control *sc, 2346 struct shrink_control *shrink) 2347{ 2348 int priority; 2349 unsigned long total_scanned = 0; 2350 struct reclaim_state *reclaim_state = current->reclaim_state; 2351 struct zoneref *z; 2352 struct zone *zone; 2353 unsigned long writeback_threshold; 2354 bool aborted_reclaim; 2355 2356 get_mems_allowed(); 2357 delayacct_freepages_start(); 2358 2359 if (global_reclaim(sc)) 2360 count_vm_event(ALLOCSTALL); 2361 2362 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2363 sc->nr_scanned = 0; 2364 if (!priority) 2365 disable_swap_token(sc->target_mem_cgroup); 2366 aborted_reclaim = shrink_zones(priority, zonelist, sc); 2367 2368 /* 2369 * Don't shrink slabs when reclaiming memory from 2370 * over limit cgroups 2371 */ 2372 if (global_reclaim(sc)) { 2373 unsigned long lru_pages = 0; 2374 for_each_zone_zonelist(zone, z, zonelist, 2375 gfp_zone(sc->gfp_mask)) { 2376 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2377 continue; 2378 2379 lru_pages += zone_reclaimable_pages(zone); 2380 } 2381 2382 shrink_slab(shrink, sc->nr_scanned, lru_pages); 2383 if (reclaim_state) { 2384 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2385 reclaim_state->reclaimed_slab = 0; 2386 } 2387 } 2388 total_scanned += sc->nr_scanned; 2389 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2390 goto out; 2391 2392 /* 2393 * Try to write back as many pages as we just scanned. This 2394 * tends to cause slow streaming writers to write data to the 2395 * disk smoothly, at the dirtying rate, which is nice. But 2396 * that's undesirable in laptop mode, where we *want* lumpy 2397 * writeout. So in laptop mode, write out the whole world. 2398 */ 2399 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2400 if (total_scanned > writeback_threshold) { 2401 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, 2402 WB_REASON_TRY_TO_FREE_PAGES); 2403 sc->may_writepage = 1; 2404 } 2405 2406 /* Take a nap, wait for some writeback to complete */ 2407 if (!sc->hibernation_mode && sc->nr_scanned && 2408 priority < DEF_PRIORITY - 2) { 2409 struct zone *preferred_zone; 2410 2411 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2412 &cpuset_current_mems_allowed, 2413 &preferred_zone); 2414 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2415 } 2416 } 2417 2418out: 2419 delayacct_freepages_end(); 2420 put_mems_allowed(); 2421 2422 if (sc->nr_reclaimed) 2423 return sc->nr_reclaimed; 2424 2425 /* 2426 * As hibernation is going on, kswapd is freezed so that it can't mark 2427 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2428 * check. 2429 */ 2430 if (oom_killer_disabled) 2431 return 0; 2432 2433 /* Aborted reclaim to try compaction? don't OOM, then */ 2434 if (aborted_reclaim) 2435 return 1; 2436 2437 /* top priority shrink_zones still had more to do? don't OOM, then */ 2438 if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) 2439 return 1; 2440 2441 return 0; 2442} 2443 2444unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2445 gfp_t gfp_mask, nodemask_t *nodemask) 2446{ 2447 unsigned long nr_reclaimed; 2448 struct scan_control sc = { 2449 .gfp_mask = gfp_mask, 2450 .may_writepage = !laptop_mode, 2451 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2452 .may_unmap = 1, 2453 .may_swap = 1, 2454 .order = order, 2455 .target_mem_cgroup = NULL, 2456 .nodemask = nodemask, 2457 }; 2458 struct shrink_control shrink = { 2459 .gfp_mask = sc.gfp_mask, 2460 }; 2461 2462 trace_mm_vmscan_direct_reclaim_begin(order, 2463 sc.may_writepage, 2464 gfp_mask); 2465 2466 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2467 2468 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2469 2470 return nr_reclaimed; 2471} 2472 2473#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2474 2475unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, 2476 gfp_t gfp_mask, bool noswap, 2477 struct zone *zone, 2478 unsigned long *nr_scanned) 2479{ 2480 struct scan_control sc = { 2481 .nr_scanned = 0, 2482 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2483 .may_writepage = !laptop_mode, 2484 .may_unmap = 1, 2485 .may_swap = !noswap, 2486 .order = 0, 2487 .target_mem_cgroup = memcg, 2488 }; 2489 struct mem_cgroup_zone mz = { 2490 .mem_cgroup = memcg, 2491 .zone = zone, 2492 }; 2493 2494 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2495 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2496 2497 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2498 sc.may_writepage, 2499 sc.gfp_mask); 2500 2501 /* 2502 * NOTE: Although we can get the priority field, using it 2503 * here is not a good idea, since it limits the pages we can scan. 2504 * if we don't reclaim here, the shrink_zone from balance_pgdat 2505 * will pick up pages from other mem cgroup's as well. We hack 2506 * the priority and make it zero. 2507 */ 2508 shrink_mem_cgroup_zone(0, &mz, &sc); 2509 2510 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2511 2512 *nr_scanned = sc.nr_scanned; 2513 return sc.nr_reclaimed; 2514} 2515 2516unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, 2517 gfp_t gfp_mask, 2518 bool noswap) 2519{ 2520 struct zonelist *zonelist; 2521 unsigned long nr_reclaimed; 2522 int nid; 2523 struct scan_control sc = { 2524 .may_writepage = !laptop_mode, 2525 .may_unmap = 1, 2526 .may_swap = !noswap, 2527 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2528 .order = 0, 2529 .target_mem_cgroup = memcg, 2530 .nodemask = NULL, /* we don't care the placement */ 2531 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2532 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), 2533 }; 2534 struct shrink_control shrink = { 2535 .gfp_mask = sc.gfp_mask, 2536 }; 2537 2538 /* 2539 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't 2540 * take care of from where we get pages. So the node where we start the 2541 * scan does not need to be the current node. 2542 */ 2543 nid = mem_cgroup_select_victim_node(memcg); 2544 2545 zonelist = NODE_DATA(nid)->node_zonelists; 2546 2547 trace_mm_vmscan_memcg_reclaim_begin(0, 2548 sc.may_writepage, 2549 sc.gfp_mask); 2550 2551 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2552 2553 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2554 2555 return nr_reclaimed; 2556} 2557#endif 2558 2559static void age_active_anon(struct zone *zone, struct scan_control *sc, 2560 int priority) 2561{ 2562 struct mem_cgroup *memcg; 2563 2564 if (!total_swap_pages) 2565 return; 2566 2567 memcg = mem_cgroup_iter(NULL, NULL, NULL); 2568 do { 2569 struct mem_cgroup_zone mz = { 2570 .mem_cgroup = memcg, 2571 .zone = zone, 2572 }; 2573 2574 if (inactive_anon_is_low(&mz)) 2575 shrink_active_list(SWAP_CLUSTER_MAX, &mz, 2576 sc, priority, 0); 2577 2578 memcg = mem_cgroup_iter(NULL, memcg, NULL); 2579 } while (memcg); 2580} 2581 2582/* 2583 * pgdat_balanced is used when checking if a node is balanced for high-order 2584 * allocations. Only zones that meet watermarks and are in a zone allowed 2585 * by the callers classzone_idx are added to balanced_pages. The total of 2586 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2587 * for the node to be considered balanced. Forcing all zones to be balanced 2588 * for high orders can cause excessive reclaim when there are imbalanced zones. 2589 * The choice of 25% is due to 2590 * o a 16M DMA zone that is balanced will not balance a zone on any 2591 * reasonable sized machine 2592 * o On all other machines, the top zone must be at least a reasonable 2593 * percentage of the middle zones. For example, on 32-bit x86, highmem 2594 * would need to be at least 256M for it to be balance a whole node. 2595 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2596 * to balance a node on its own. These seemed like reasonable ratios. 2597 */ 2598static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2599 int classzone_idx) 2600{ 2601 unsigned long present_pages = 0; 2602 int i; 2603 2604 for (i = 0; i <= classzone_idx; i++) 2605 present_pages += pgdat->node_zones[i].present_pages; 2606 2607 /* A special case here: if zone has no page, we think it's balanced */ 2608 return balanced_pages >= (present_pages >> 2); 2609} 2610 2611/* is kswapd sleeping prematurely? */ 2612static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2613 int classzone_idx) 2614{ 2615 int i; 2616 unsigned long balanced = 0; 2617 bool all_zones_ok = true; 2618 2619 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2620 if (remaining) 2621 return true; 2622 2623 /* Check the watermark levels */ 2624 for (i = 0; i <= classzone_idx; i++) { 2625 struct zone *zone = pgdat->node_zones + i; 2626 2627 if (!populated_zone(zone)) 2628 continue; 2629 2630 /* 2631 * balance_pgdat() skips over all_unreclaimable after 2632 * DEF_PRIORITY. Effectively, it considers them balanced so 2633 * they must be considered balanced here as well if kswapd 2634 * is to sleep 2635 */ 2636 if (zone->all_unreclaimable) { 2637 balanced += zone->present_pages; 2638 continue; 2639 } 2640 2641 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2642 i, 0)) 2643 all_zones_ok = false; 2644 else 2645 balanced += zone->present_pages; 2646 } 2647 2648 /* 2649 * For high-order requests, the balanced zones must contain at least 2650 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2651 * must be balanced 2652 */ 2653 if (order) 2654 return !pgdat_balanced(pgdat, balanced, classzone_idx); 2655 else 2656 return !all_zones_ok; 2657} 2658 2659/* 2660 * For kswapd, balance_pgdat() will work across all this node's zones until 2661 * they are all at high_wmark_pages(zone). 2662 * 2663 * Returns the final order kswapd was reclaiming at 2664 * 2665 * There is special handling here for zones which are full of pinned pages. 2666 * This can happen if the pages are all mlocked, or if they are all used by 2667 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2668 * What we do is to detect the case where all pages in the zone have been 2669 * scanned twice and there has been zero successful reclaim. Mark the zone as 2670 * dead and from now on, only perform a short scan. Basically we're polling 2671 * the zone for when the problem goes away. 2672 * 2673 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2674 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2675 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2676 * lower zones regardless of the number of free pages in the lower zones. This 2677 * interoperates with the page allocator fallback scheme to ensure that aging 2678 * of pages is balanced across the zones. 2679 */ 2680static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2681 int *classzone_idx) 2682{ 2683 int all_zones_ok; 2684 unsigned long balanced; 2685 int priority; 2686 int i; 2687 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2688 unsigned long total_scanned; 2689 struct reclaim_state *reclaim_state = current->reclaim_state; 2690 unsigned long nr_soft_reclaimed; 2691 unsigned long nr_soft_scanned; 2692 struct scan_control sc = { 2693 .gfp_mask = GFP_KERNEL, 2694 .may_unmap = 1, 2695 .may_swap = 1, 2696 /* 2697 * kswapd doesn't want to be bailed out while reclaim. because 2698 * we want to put equal scanning pressure on each zone. 2699 */ 2700 .nr_to_reclaim = ULONG_MAX, 2701 .order = order, 2702 .target_mem_cgroup = NULL, 2703 }; 2704 struct shrink_control shrink = { 2705 .gfp_mask = sc.gfp_mask, 2706 }; 2707loop_again: 2708 total_scanned = 0; 2709 sc.nr_reclaimed = 0; 2710 sc.may_writepage = !laptop_mode; 2711 count_vm_event(PAGEOUTRUN); 2712 2713 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2714 unsigned long lru_pages = 0; 2715 int has_under_min_watermark_zone = 0; 2716 2717 /* The swap token gets in the way of swapout... */ 2718 if (!priority) 2719 disable_swap_token(NULL); 2720 2721 all_zones_ok = 1; 2722 balanced = 0; 2723 2724 /* 2725 * Scan in the highmem->dma direction for the highest 2726 * zone which needs scanning 2727 */ 2728 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2729 struct zone *zone = pgdat->node_zones + i; 2730 2731 if (!populated_zone(zone)) 2732 continue; 2733 2734 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2735 continue; 2736 2737 /* 2738 * Do some background aging of the anon list, to give 2739 * pages a chance to be referenced before reclaiming. 2740 */ 2741 age_active_anon(zone, &sc, priority); 2742 2743 if (!zone_watermark_ok_safe(zone, order, 2744 high_wmark_pages(zone), 0, 0)) { 2745 end_zone = i; 2746 break; 2747 } else { 2748 /* If balanced, clear the congested flag */ 2749 zone_clear_flag(zone, ZONE_CONGESTED); 2750 } 2751 } 2752 if (i < 0) 2753 goto out; 2754 2755 for (i = 0; i <= end_zone; i++) { 2756 struct zone *zone = pgdat->node_zones + i; 2757 2758 lru_pages += zone_reclaimable_pages(zone); 2759 } 2760 2761 /* 2762 * Now scan the zone in the dma->highmem direction, stopping 2763 * at the last zone which needs scanning. 2764 * 2765 * We do this because the page allocator works in the opposite 2766 * direction. This prevents the page allocator from allocating 2767 * pages behind kswapd's direction of progress, which would 2768 * cause too much scanning of the lower zones. 2769 */ 2770 for (i = 0; i <= end_zone; i++) { 2771 struct zone *zone = pgdat->node_zones + i; 2772 int nr_slab; 2773 unsigned long balance_gap; 2774 2775 if (!populated_zone(zone)) 2776 continue; 2777 2778 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2779 continue; 2780 2781 sc.nr_scanned = 0; 2782 2783 nr_soft_scanned = 0; 2784 /* 2785 * Call soft limit reclaim before calling shrink_zone. 2786 */ 2787 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2788 order, sc.gfp_mask, 2789 &nr_soft_scanned); 2790 sc.nr_reclaimed += nr_soft_reclaimed; 2791 total_scanned += nr_soft_scanned; 2792 2793 /* 2794 * We put equal pressure on every zone, unless 2795 * one zone has way too many pages free 2796 * already. The "too many pages" is defined 2797 * as the high wmark plus a "gap" where the 2798 * gap is either the low watermark or 1% 2799 * of the zone, whichever is smaller. 2800 */ 2801 balance_gap = min(low_wmark_pages(zone), 2802 (zone->present_pages + 2803 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2804 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2805 if (!zone_watermark_ok_safe(zone, order, 2806 high_wmark_pages(zone) + balance_gap, 2807 end_zone, 0)) { 2808 shrink_zone(priority, zone, &sc); 2809 2810 reclaim_state->reclaimed_slab = 0; 2811 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); 2812 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2813 total_scanned += sc.nr_scanned; 2814 2815 if (nr_slab == 0 && !zone_reclaimable(zone)) 2816 zone->all_unreclaimable = 1; 2817 } 2818 2819 /* 2820 * If we've done a decent amount of scanning and 2821 * the reclaim ratio is low, start doing writepage 2822 * even in laptop mode 2823 */ 2824 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2825 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2826 sc.may_writepage = 1; 2827 2828 if (zone->all_unreclaimable) { 2829 if (end_zone && end_zone == i) 2830 end_zone--; 2831 continue; 2832 } 2833 2834 if (!zone_watermark_ok_safe(zone, order, 2835 high_wmark_pages(zone), end_zone, 0)) { 2836 all_zones_ok = 0; 2837 /* 2838 * We are still under min water mark. This 2839 * means that we have a GFP_ATOMIC allocation 2840 * failure risk. Hurry up! 2841 */ 2842 if (!zone_watermark_ok_safe(zone, order, 2843 min_wmark_pages(zone), end_zone, 0)) 2844 has_under_min_watermark_zone = 1; 2845 } else { 2846 /* 2847 * If a zone reaches its high watermark, 2848 * consider it to be no longer congested. It's 2849 * possible there are dirty pages backed by 2850 * congested BDIs but as pressure is relieved, 2851 * spectulatively avoid congestion waits 2852 */ 2853 zone_clear_flag(zone, ZONE_CONGESTED); 2854 if (i <= *classzone_idx) 2855 balanced += zone->present_pages; 2856 } 2857 2858 } 2859 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2860 break; /* kswapd: all done */ 2861 /* 2862 * OK, kswapd is getting into trouble. Take a nap, then take 2863 * another pass across the zones. 2864 */ 2865 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2866 if (has_under_min_watermark_zone) 2867 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2868 else 2869 congestion_wait(BLK_RW_ASYNC, HZ/10); 2870 } 2871 2872 /* 2873 * We do this so kswapd doesn't build up large priorities for 2874 * example when it is freeing in parallel with allocators. It 2875 * matches the direct reclaim path behaviour in terms of impact 2876 * on zone->*_priority. 2877 */ 2878 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2879 break; 2880 } 2881out: 2882 2883 /* 2884 * order-0: All zones must meet high watermark for a balanced node 2885 * high-order: Balanced zones must make up at least 25% of the node 2886 * for the node to be balanced 2887 */ 2888 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2889 cond_resched(); 2890 2891 try_to_freeze(); 2892 2893 /* 2894 * Fragmentation may mean that the system cannot be 2895 * rebalanced for high-order allocations in all zones. 2896 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2897 * it means the zones have been fully scanned and are still 2898 * not balanced. For high-order allocations, there is 2899 * little point trying all over again as kswapd may 2900 * infinite loop. 2901 * 2902 * Instead, recheck all watermarks at order-0 as they 2903 * are the most important. If watermarks are ok, kswapd will go 2904 * back to sleep. High-order users can still perform direct 2905 * reclaim if they wish. 2906 */ 2907 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2908 order = sc.order = 0; 2909 2910 goto loop_again; 2911 } 2912 2913 /* 2914 * If kswapd was reclaiming at a higher order, it has the option of 2915 * sleeping without all zones being balanced. Before it does, it must 2916 * ensure that the watermarks for order-0 on *all* zones are met and 2917 * that the congestion flags are cleared. The congestion flag must 2918 * be cleared as kswapd is the only mechanism that clears the flag 2919 * and it is potentially going to sleep here. 2920 */ 2921 if (order) { 2922 for (i = 0; i <= end_zone; i++) { 2923 struct zone *zone = pgdat->node_zones + i; 2924 2925 if (!populated_zone(zone)) 2926 continue; 2927 2928 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2929 continue; 2930 2931 /* Confirm the zone is balanced for order-0 */ 2932 if (!zone_watermark_ok(zone, 0, 2933 high_wmark_pages(zone), 0, 0)) { 2934 order = sc.order = 0; 2935 goto loop_again; 2936 } 2937 2938 /* If balanced, clear the congested flag */ 2939 zone_clear_flag(zone, ZONE_CONGESTED); 2940 if (i <= *classzone_idx) 2941 balanced += zone->present_pages; 2942 } 2943 } 2944 2945 /* 2946 * Return the order we were reclaiming at so sleeping_prematurely() 2947 * makes a decision on the order we were last reclaiming at. However, 2948 * if another caller entered the allocator slow path while kswapd 2949 * was awake, order will remain at the higher level 2950 */ 2951 *classzone_idx = end_zone; 2952 return order; 2953} 2954 2955static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2956{ 2957 long remaining = 0; 2958 DEFINE_WAIT(wait); 2959 2960 if (freezing(current) || kthread_should_stop()) 2961 return; 2962 2963 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2964 2965 /* Try to sleep for a short interval */ 2966 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2967 remaining = schedule_timeout(HZ/10); 2968 finish_wait(&pgdat->kswapd_wait, &wait); 2969 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2970 } 2971 2972 /* 2973 * After a short sleep, check if it was a premature sleep. If not, then 2974 * go fully to sleep until explicitly woken up. 2975 */ 2976 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2977 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2978 2979 /* 2980 * vmstat counters are not perfectly accurate and the estimated 2981 * value for counters such as NR_FREE_PAGES can deviate from the 2982 * true value by nr_online_cpus * threshold. To avoid the zone 2983 * watermarks being breached while under pressure, we reduce the 2984 * per-cpu vmstat threshold while kswapd is awake and restore 2985 * them before going back to sleep. 2986 */ 2987 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2988 schedule(); 2989 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2990 } else { 2991 if (remaining) 2992 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2993 else 2994 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2995 } 2996 finish_wait(&pgdat->kswapd_wait, &wait); 2997} 2998 2999/* 3000 * The background pageout daemon, started as a kernel thread 3001 * from the init process. 3002 * 3003 * This basically trickles out pages so that we have _some_ 3004 * free memory available even if there is no other activity 3005 * that frees anything up. This is needed for things like routing 3006 * etc, where we otherwise might have all activity going on in 3007 * asynchronous contexts that cannot page things out. 3008 * 3009 * If there are applications that are active memory-allocators 3010 * (most normal use), this basically shouldn't matter. 3011 */ 3012static int kswapd(void *p) 3013{ 3014 unsigned long order, new_order; 3015 unsigned balanced_order; 3016 int classzone_idx, new_classzone_idx; 3017 int balanced_classzone_idx; 3018 pg_data_t *pgdat = (pg_data_t*)p; 3019 struct task_struct *tsk = current; 3020 3021 struct reclaim_state reclaim_state = { 3022 .reclaimed_slab = 0, 3023 }; 3024 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 3025 3026 lockdep_set_current_reclaim_state(GFP_KERNEL); 3027 3028 if (!cpumask_empty(cpumask)) 3029 set_cpus_allowed_ptr(tsk, cpumask); 3030 current->reclaim_state = &reclaim_state; 3031 3032 /* 3033 * Tell the memory management that we're a "memory allocator", 3034 * and that if we need more memory we should get access to it 3035 * regardless (see "__alloc_pages()"). "kswapd" should 3036 * never get caught in the normal page freeing logic. 3037 * 3038 * (Kswapd normally doesn't need memory anyway, but sometimes 3039 * you need a small amount of memory in order to be able to 3040 * page out something else, and this flag essentially protects 3041 * us from recursively trying to free more memory as we're 3042 * trying to free the first piece of memory in the first place). 3043 */ 3044 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 3045 set_freezable(); 3046 3047 order = new_order = 0; 3048 balanced_order = 0; 3049 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; 3050 balanced_classzone_idx = classzone_idx; 3051 for ( ; ; ) { 3052 int ret; 3053 3054 /* 3055 * If the last balance_pgdat was unsuccessful it's unlikely a 3056 * new request of a similar or harder type will succeed soon 3057 * so consider going to sleep on the basis we reclaimed at 3058 */ 3059 if (balanced_classzone_idx >= new_classzone_idx && 3060 balanced_order == new_order) { 3061 new_order = pgdat->kswapd_max_order; 3062 new_classzone_idx = pgdat->classzone_idx; 3063 pgdat->kswapd_max_order = 0; 3064 pgdat->classzone_idx = pgdat->nr_zones - 1; 3065 } 3066 3067 if (order < new_order || classzone_idx > new_classzone_idx) { 3068 /* 3069 * Don't sleep if someone wants a larger 'order' 3070 * allocation or has tigher zone constraints 3071 */ 3072 order = new_order; 3073 classzone_idx = new_classzone_idx; 3074 } else { 3075 kswapd_try_to_sleep(pgdat, balanced_order, 3076 balanced_classzone_idx); 3077 order = pgdat->kswapd_max_order; 3078 classzone_idx = pgdat->classzone_idx; 3079 new_order = order; 3080 new_classzone_idx = classzone_idx; 3081 pgdat->kswapd_max_order = 0; 3082 pgdat->classzone_idx = pgdat->nr_zones - 1; 3083 } 3084 3085 ret = try_to_freeze(); 3086 if (kthread_should_stop()) 3087 break; 3088 3089 /* 3090 * We can speed up thawing tasks if we don't call balance_pgdat 3091 * after returning from the refrigerator 3092 */ 3093 if (!ret) { 3094 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 3095 balanced_classzone_idx = classzone_idx; 3096 balanced_order = balance_pgdat(pgdat, order, 3097 &balanced_classzone_idx); 3098 } 3099 } 3100 return 0; 3101} 3102 3103/* 3104 * A zone is low on free memory, so wake its kswapd task to service it. 3105 */ 3106void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 3107{ 3108 pg_data_t *pgdat; 3109 3110 if (!populated_zone(zone)) 3111 return; 3112 3113 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 3114 return; 3115 pgdat = zone->zone_pgdat; 3116 if (pgdat->kswapd_max_order < order) { 3117 pgdat->kswapd_max_order = order; 3118 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 3119 } 3120 if (!waitqueue_active(&pgdat->kswapd_wait)) 3121 return; 3122 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 3123 return; 3124 3125 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 3126 wake_up_interruptible(&pgdat->kswapd_wait); 3127} 3128 3129/* 3130 * The reclaimable count would be mostly accurate. 3131 * The less reclaimable pages may be 3132 * - mlocked pages, which will be moved to unevictable list when encountered 3133 * - mapped pages, which may require several travels to be reclaimed 3134 * - dirty pages, which is not "instantly" reclaimable 3135 */ 3136unsigned long global_reclaimable_pages(void) 3137{ 3138 int nr; 3139 3140 nr = global_page_state(NR_ACTIVE_FILE) + 3141 global_page_state(NR_INACTIVE_FILE); 3142 3143 if (nr_swap_pages > 0) 3144 nr += global_page_state(NR_ACTIVE_ANON) + 3145 global_page_state(NR_INACTIVE_ANON); 3146 3147 return nr; 3148} 3149 3150unsigned long zone_reclaimable_pages(struct zone *zone) 3151{ 3152 int nr; 3153 3154 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 3155 zone_page_state(zone, NR_INACTIVE_FILE); 3156 3157 if (nr_swap_pages > 0) 3158 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 3159 zone_page_state(zone, NR_INACTIVE_ANON); 3160 3161 return nr; 3162} 3163 3164#ifdef CONFIG_HIBERNATION 3165/* 3166 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 3167 * freed pages. 3168 * 3169 * Rather than trying to age LRUs the aim is to preserve the overall 3170 * LRU order by reclaiming preferentially 3171 * inactive > active > active referenced > active mapped 3172 */ 3173unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 3174{ 3175 struct reclaim_state reclaim_state; 3176 struct scan_control sc = { 3177 .gfp_mask = GFP_HIGHUSER_MOVABLE, 3178 .may_swap = 1, 3179 .may_unmap = 1, 3180 .may_writepage = 1, 3181 .nr_to_reclaim = nr_to_reclaim, 3182 .hibernation_mode = 1, 3183 .order = 0, 3184 }; 3185 struct shrink_control shrink = { 3186 .gfp_mask = sc.gfp_mask, 3187 }; 3188 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 3189 struct task_struct *p = current; 3190 unsigned long nr_reclaimed; 3191 3192 p->flags |= PF_MEMALLOC; 3193 lockdep_set_current_reclaim_state(sc.gfp_mask); 3194 reclaim_state.reclaimed_slab = 0; 3195 p->reclaim_state = &reclaim_state; 3196 3197 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 3198 3199 p->reclaim_state = NULL; 3200 lockdep_clear_current_reclaim_state(); 3201 p->flags &= ~PF_MEMALLOC; 3202 3203 return nr_reclaimed; 3204} 3205#endif /* CONFIG_HIBERNATION */ 3206 3207/* It's optimal to keep kswapds on the same CPUs as their memory, but 3208 not required for correctness. So if the last cpu in a node goes 3209 away, we get changed to run anywhere: as the first one comes back, 3210 restore their cpu bindings. */ 3211static int __devinit cpu_callback(struct notifier_block *nfb, 3212 unsigned long action, void *hcpu) 3213{ 3214 int nid; 3215 3216 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 3217 for_each_node_state(nid, N_HIGH_MEMORY) { 3218 pg_data_t *pgdat = NODE_DATA(nid); 3219 const struct cpumask *mask; 3220 3221 mask = cpumask_of_node(pgdat->node_id); 3222 3223 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 3224 /* One of our CPUs online: restore mask */ 3225 set_cpus_allowed_ptr(pgdat->kswapd, mask); 3226 } 3227 } 3228 return NOTIFY_OK; 3229} 3230 3231/* 3232 * This kswapd start function will be called by init and node-hot-add. 3233 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 3234 */ 3235int kswapd_run(int nid) 3236{ 3237 pg_data_t *pgdat = NODE_DATA(nid); 3238 int ret = 0; 3239 3240 if (pgdat->kswapd) 3241 return 0; 3242 3243 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 3244 if (IS_ERR(pgdat->kswapd)) { 3245 /* failure at boot is fatal */ 3246 BUG_ON(system_state == SYSTEM_BOOTING); 3247 printk("Failed to start kswapd on node %d\n",nid); 3248 ret = -1; 3249 } 3250 return ret; 3251} 3252 3253/* 3254 * Called by memory hotplug when all memory in a node is offlined. 3255 */ 3256void kswapd_stop(int nid) 3257{ 3258 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 3259 3260 if (kswapd) 3261 kthread_stop(kswapd); 3262} 3263 3264static int __init kswapd_init(void) 3265{ 3266 int nid; 3267 3268 swap_setup(); 3269 for_each_node_state(nid, N_HIGH_MEMORY) 3270 kswapd_run(nid); 3271 hotcpu_notifier(cpu_callback, 0); 3272 return 0; 3273} 3274 3275module_init(kswapd_init) 3276 3277#ifdef CONFIG_NUMA 3278/* 3279 * Zone reclaim mode 3280 * 3281 * If non-zero call zone_reclaim when the number of free pages falls below 3282 * the watermarks. 3283 */ 3284int zone_reclaim_mode __read_mostly; 3285 3286#define RECLAIM_OFF 0 3287#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 3288#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 3289#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 3290 3291/* 3292 * Priority for ZONE_RECLAIM. This determines the fraction of pages 3293 * of a node considered for each zone_reclaim. 4 scans 1/16th of 3294 * a zone. 3295 */ 3296#define ZONE_RECLAIM_PRIORITY 4 3297 3298/* 3299 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 3300 * occur. 3301 */ 3302int sysctl_min_unmapped_ratio = 1; 3303 3304/* 3305 * If the number of slab pages in a zone grows beyond this percentage then 3306 * slab reclaim needs to occur. 3307 */ 3308int sysctl_min_slab_ratio = 5; 3309 3310static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 3311{ 3312 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 3313 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 3314 zone_page_state(zone, NR_ACTIVE_FILE); 3315 3316 /* 3317 * It's possible for there to be more file mapped pages than 3318 * accounted for by the pages on the file LRU lists because 3319 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 3320 */ 3321 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 3322} 3323 3324/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 3325static long zone_pagecache_reclaimable(struct zone *zone) 3326{ 3327 long nr_pagecache_reclaimable; 3328 long delta = 0; 3329 3330 /* 3331 * If RECLAIM_SWAP is set, then all file pages are considered 3332 * potentially reclaimable. Otherwise, we have to worry about 3333 * pages like swapcache and zone_unmapped_file_pages() provides 3334 * a better estimate 3335 */ 3336 if (zone_reclaim_mode & RECLAIM_SWAP) 3337 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 3338 else 3339 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 3340 3341 /* If we can't clean pages, remove dirty pages from consideration */ 3342 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 3343 delta += zone_page_state(zone, NR_FILE_DIRTY); 3344 3345 /* Watch for any possible underflows due to delta */ 3346 if (unlikely(delta > nr_pagecache_reclaimable)) 3347 delta = nr_pagecache_reclaimable; 3348 3349 return nr_pagecache_reclaimable - delta; 3350} 3351 3352/* 3353 * Try to free up some pages from this zone through reclaim. 3354 */ 3355static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3356{ 3357 /* Minimum pages needed in order to stay on node */ 3358 const unsigned long nr_pages = 1 << order; 3359 struct task_struct *p = current; 3360 struct reclaim_state reclaim_state; 3361 int priority; 3362 struct scan_control sc = { 3363 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 3364 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 3365 .may_swap = 1, 3366 .nr_to_reclaim = max_t(unsigned long, nr_pages, 3367 SWAP_CLUSTER_MAX), 3368 .gfp_mask = gfp_mask, 3369 .order = order, 3370 }; 3371 struct shrink_control shrink = { 3372 .gfp_mask = sc.gfp_mask, 3373 }; 3374 unsigned long nr_slab_pages0, nr_slab_pages1; 3375 3376 cond_resched(); 3377 /* 3378 * We need to be able to allocate from the reserves for RECLAIM_SWAP 3379 * and we also need to be able to write out pages for RECLAIM_WRITE 3380 * and RECLAIM_SWAP. 3381 */ 3382 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 3383 lockdep_set_current_reclaim_state(gfp_mask); 3384 reclaim_state.reclaimed_slab = 0; 3385 p->reclaim_state = &reclaim_state; 3386 3387 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 3388 /* 3389 * Free memory by calling shrink zone with increasing 3390 * priorities until we have enough memory freed. 3391 */ 3392 priority = ZONE_RECLAIM_PRIORITY; 3393 do { 3394 shrink_zone(priority, zone, &sc); 3395 priority--; 3396 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 3397 } 3398 3399 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3400 if (nr_slab_pages0 > zone->min_slab_pages) { 3401 /* 3402 * shrink_slab() does not currently allow us to determine how 3403 * many pages were freed in this zone. So we take the current 3404 * number of slab pages and shake the slab until it is reduced 3405 * by the same nr_pages that we used for reclaiming unmapped 3406 * pages. 3407 * 3408 * Note that shrink_slab will free memory on all zones and may 3409 * take a long time. 3410 */ 3411 for (;;) { 3412 unsigned long lru_pages = zone_reclaimable_pages(zone); 3413 3414 /* No reclaimable slab or very low memory pressure */ 3415 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) 3416 break; 3417 3418 /* Freed enough memory */ 3419 nr_slab_pages1 = zone_page_state(zone, 3420 NR_SLAB_RECLAIMABLE); 3421 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3422 break; 3423 } 3424 3425 /* 3426 * Update nr_reclaimed by the number of slab pages we 3427 * reclaimed from this zone. 3428 */ 3429 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3430 if (nr_slab_pages1 < nr_slab_pages0) 3431 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3432 } 3433 3434 p->reclaim_state = NULL; 3435 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3436 lockdep_clear_current_reclaim_state(); 3437 return sc.nr_reclaimed >= nr_pages; 3438} 3439 3440int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3441{ 3442 int node_id; 3443 int ret; 3444 3445 /* 3446 * Zone reclaim reclaims unmapped file backed pages and 3447 * slab pages if we are over the defined limits. 3448 * 3449 * A small portion of unmapped file backed pages is needed for 3450 * file I/O otherwise pages read by file I/O will be immediately 3451 * thrown out if the zone is overallocated. So we do not reclaim 3452 * if less than a specified percentage of the zone is used by 3453 * unmapped file backed pages. 3454 */ 3455 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3456 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3457 return ZONE_RECLAIM_FULL; 3458 3459 if (zone->all_unreclaimable) 3460 return ZONE_RECLAIM_FULL; 3461 3462 /* 3463 * Do not scan if the allocation should not be delayed. 3464 */ 3465 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3466 return ZONE_RECLAIM_NOSCAN; 3467 3468 /* 3469 * Only run zone reclaim on the local zone or on zones that do not 3470 * have associated processors. This will favor the local processor 3471 * over remote processors and spread off node memory allocations 3472 * as wide as possible. 3473 */ 3474 node_id = zone_to_nid(zone); 3475 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3476 return ZONE_RECLAIM_NOSCAN; 3477 3478 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3479 return ZONE_RECLAIM_NOSCAN; 3480 3481 ret = __zone_reclaim(zone, gfp_mask, order); 3482 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3483 3484 if (!ret) 3485 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3486 3487 return ret; 3488} 3489#endif 3490 3491/* 3492 * page_evictable - test whether a page is evictable 3493 * @page: the page to test 3494 * @vma: the VMA in which the page is or will be mapped, may be NULL 3495 * 3496 * Test whether page is evictable--i.e., should be placed on active/inactive 3497 * lists vs unevictable list. The vma argument is !NULL when called from the 3498 * fault path to determine how to instantate a new page. 3499 * 3500 * Reasons page might not be evictable: 3501 * (1) page's mapping marked unevictable 3502 * (2) page is part of an mlocked VMA 3503 * 3504 */ 3505int page_evictable(struct page *page, struct vm_area_struct *vma) 3506{ 3507 3508 if (mapping_unevictable(page_mapping(page))) 3509 return 0; 3510 3511 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3512 return 0; 3513 3514 return 1; 3515} 3516 3517/** 3518 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3519 * @page: page to check evictability and move to appropriate lru list 3520 * @zone: zone page is in 3521 * 3522 * Checks a page for evictability and moves the page to the appropriate 3523 * zone lru list. 3524 * 3525 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3526 * have PageUnevictable set. 3527 */ 3528static void check_move_unevictable_page(struct page *page, struct zone *zone) 3529{ 3530 struct lruvec *lruvec; 3531 3532 VM_BUG_ON(PageActive(page)); 3533retry: 3534 ClearPageUnevictable(page); 3535 if (page_evictable(page, NULL)) { 3536 enum lru_list l = page_lru_base_type(page); 3537 3538 __dec_zone_state(zone, NR_UNEVICTABLE); 3539 lruvec = mem_cgroup_lru_move_lists(zone, page, 3540 LRU_UNEVICTABLE, l); 3541 list_move(&page->lru, &lruvec->lists[l]); 3542 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3543 __count_vm_event(UNEVICTABLE_PGRESCUED); 3544 } else { 3545 /* 3546 * rotate unevictable list 3547 */ 3548 SetPageUnevictable(page); 3549 lruvec = mem_cgroup_lru_move_lists(zone, page, LRU_UNEVICTABLE, 3550 LRU_UNEVICTABLE); 3551 list_move(&page->lru, &lruvec->lists[LRU_UNEVICTABLE]); 3552 if (page_evictable(page, NULL)) 3553 goto retry; 3554 } 3555} 3556 3557/** 3558 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3559 * @mapping: struct address_space to scan for evictable pages 3560 * 3561 * Scan all pages in mapping. Check unevictable pages for 3562 * evictability and move them to the appropriate zone lru list. 3563 */ 3564void scan_mapping_unevictable_pages(struct address_space *mapping) 3565{ 3566 pgoff_t next = 0; 3567 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3568 PAGE_CACHE_SHIFT; 3569 struct zone *zone; 3570 struct pagevec pvec; 3571 3572 if (mapping->nrpages == 0) 3573 return; 3574 3575 pagevec_init(&pvec, 0); 3576 while (next < end && 3577 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3578 int i; 3579 int pg_scanned = 0; 3580 3581 zone = NULL; 3582 3583 for (i = 0; i < pagevec_count(&pvec); i++) { 3584 struct page *page = pvec.pages[i]; 3585 pgoff_t page_index = page->index; 3586 struct zone *pagezone = page_zone(page); 3587 3588 pg_scanned++; 3589 if (page_index > next) 3590 next = page_index; 3591 next++; 3592 3593 if (pagezone != zone) { 3594 if (zone) 3595 spin_unlock_irq(&zone->lru_lock); 3596 zone = pagezone; 3597 spin_lock_irq(&zone->lru_lock); 3598 } 3599 3600 if (PageLRU(page) && PageUnevictable(page)) 3601 check_move_unevictable_page(page, zone); 3602 } 3603 if (zone) 3604 spin_unlock_irq(&zone->lru_lock); 3605 pagevec_release(&pvec); 3606 3607 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3608 } 3609 3610} 3611 3612static void warn_scan_unevictable_pages(void) 3613{ 3614 printk_once(KERN_WARNING 3615 "%s: The scan_unevictable_pages sysctl/node-interface has been " 3616 "disabled for lack of a legitimate use case. If you have " 3617 "one, please send an email to linux-mm@kvack.org.\n", 3618 current->comm); 3619} 3620 3621/* 3622 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3623 * all nodes' unevictable lists for evictable pages 3624 */ 3625unsigned long scan_unevictable_pages; 3626 3627int scan_unevictable_handler(struct ctl_table *table, int write, 3628 void __user *buffer, 3629 size_t *length, loff_t *ppos) 3630{ 3631 warn_scan_unevictable_pages(); 3632 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3633 scan_unevictable_pages = 0; 3634 return 0; 3635} 3636 3637#ifdef CONFIG_NUMA 3638/* 3639 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3640 * a specified node's per zone unevictable lists for evictable pages. 3641 */ 3642 3643static ssize_t read_scan_unevictable_node(struct device *dev, 3644 struct device_attribute *attr, 3645 char *buf) 3646{ 3647 warn_scan_unevictable_pages(); 3648 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3649} 3650 3651static ssize_t write_scan_unevictable_node(struct device *dev, 3652 struct device_attribute *attr, 3653 const char *buf, size_t count) 3654{ 3655 warn_scan_unevictable_pages(); 3656 return 1; 3657} 3658 3659 3660static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3661 read_scan_unevictable_node, 3662 write_scan_unevictable_node); 3663 3664int scan_unevictable_register_node(struct node *node) 3665{ 3666 return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages); 3667} 3668 3669void scan_unevictable_unregister_node(struct node *node) 3670{ 3671 device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages); 3672} 3673#endif 3674