vmscan.c revision a433658c30974fc87ba3ff52d7e4e6299762aa3d
1/* 2 * linux/mm/vmscan.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * 6 * Swap reorganised 29.12.95, Stephen Tweedie. 7 * kswapd added: 7.1.96 sct 8 * Removed kswapd_ctl limits, and swap out as many pages as needed 9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). 11 * Multiqueue VM started 5.8.00, Rik van Riel. 12 */ 13 14#include <linux/mm.h> 15#include <linux/module.h> 16#include <linux/gfp.h> 17#include <linux/kernel_stat.h> 18#include <linux/swap.h> 19#include <linux/pagemap.h> 20#include <linux/init.h> 21#include <linux/highmem.h> 22#include <linux/vmstat.h> 23#include <linux/file.h> 24#include <linux/writeback.h> 25#include <linux/blkdev.h> 26#include <linux/buffer_head.h> /* for try_to_release_page(), 27 buffer_heads_over_limit */ 28#include <linux/mm_inline.h> 29#include <linux/pagevec.h> 30#include <linux/backing-dev.h> 31#include <linux/rmap.h> 32#include <linux/topology.h> 33#include <linux/cpu.h> 34#include <linux/cpuset.h> 35#include <linux/compaction.h> 36#include <linux/notifier.h> 37#include <linux/rwsem.h> 38#include <linux/delay.h> 39#include <linux/kthread.h> 40#include <linux/freezer.h> 41#include <linux/memcontrol.h> 42#include <linux/delayacct.h> 43#include <linux/sysctl.h> 44#include <linux/oom.h> 45#include <linux/prefetch.h> 46 47#include <asm/tlbflush.h> 48#include <asm/div64.h> 49 50#include <linux/swapops.h> 51 52#include "internal.h" 53 54#define CREATE_TRACE_POINTS 55#include <trace/events/vmscan.h> 56 57/* 58 * reclaim_mode determines how the inactive list is shrunk 59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages 60 * RECLAIM_MODE_ASYNC: Do not block 61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback 62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference 63 * page from the LRU and reclaim all pages within a 64 * naturally aligned range 65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of 66 * order-0 pages and then compact the zone 67 */ 68typedef unsigned __bitwise__ reclaim_mode_t; 69#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) 70#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) 71#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) 72#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) 73#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) 74 75struct scan_control { 76 /* Incremented by the number of inactive pages that were scanned */ 77 unsigned long nr_scanned; 78 79 /* Number of pages freed so far during a call to shrink_zones() */ 80 unsigned long nr_reclaimed; 81 82 /* How many pages shrink_list() should reclaim */ 83 unsigned long nr_to_reclaim; 84 85 unsigned long hibernation_mode; 86 87 /* This context's GFP mask */ 88 gfp_t gfp_mask; 89 90 int may_writepage; 91 92 /* Can mapped pages be reclaimed? */ 93 int may_unmap; 94 95 /* Can pages be swapped as part of reclaim? */ 96 int may_swap; 97 98 int swappiness; 99 100 int order; 101 102 /* 103 * Intend to reclaim enough continuous memory rather than reclaim 104 * enough amount of memory. i.e, mode for high order allocation. 105 */ 106 reclaim_mode_t reclaim_mode; 107 108 /* Which cgroup do we reclaim from */ 109 struct mem_cgroup *mem_cgroup; 110 111 /* 112 * Nodemask of nodes allowed by the caller. If NULL, all nodes 113 * are scanned. 114 */ 115 nodemask_t *nodemask; 116}; 117 118#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 119 120#ifdef ARCH_HAS_PREFETCH 121#define prefetch_prev_lru_page(_page, _base, _field) \ 122 do { \ 123 if ((_page)->lru.prev != _base) { \ 124 struct page *prev; \ 125 \ 126 prev = lru_to_page(&(_page->lru)); \ 127 prefetch(&prev->_field); \ 128 } \ 129 } while (0) 130#else 131#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 132#endif 133 134#ifdef ARCH_HAS_PREFETCHW 135#define prefetchw_prev_lru_page(_page, _base, _field) \ 136 do { \ 137 if ((_page)->lru.prev != _base) { \ 138 struct page *prev; \ 139 \ 140 prev = lru_to_page(&(_page->lru)); \ 141 prefetchw(&prev->_field); \ 142 } \ 143 } while (0) 144#else 145#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 146#endif 147 148/* 149 * From 0 .. 100. Higher means more swappy. 150 */ 151int vm_swappiness = 60; 152long vm_total_pages; /* The total number of pages which the VM controls */ 153 154static LIST_HEAD(shrinker_list); 155static DECLARE_RWSEM(shrinker_rwsem); 156 157#ifdef CONFIG_CGROUP_MEM_RES_CTLR 158#define scanning_global_lru(sc) (!(sc)->mem_cgroup) 159#else 160#define scanning_global_lru(sc) (1) 161#endif 162 163static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 164 struct scan_control *sc) 165{ 166 if (!scanning_global_lru(sc)) 167 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 168 169 return &zone->reclaim_stat; 170} 171 172static unsigned long zone_nr_lru_pages(struct zone *zone, 173 struct scan_control *sc, enum lru_list lru) 174{ 175 if (!scanning_global_lru(sc)) 176 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup, zone, lru); 177 178 return zone_page_state(zone, NR_LRU_BASE + lru); 179} 180 181 182/* 183 * Add a shrinker callback to be called from the vm 184 */ 185void register_shrinker(struct shrinker *shrinker) 186{ 187 shrinker->nr = 0; 188 down_write(&shrinker_rwsem); 189 list_add_tail(&shrinker->list, &shrinker_list); 190 up_write(&shrinker_rwsem); 191} 192EXPORT_SYMBOL(register_shrinker); 193 194/* 195 * Remove one 196 */ 197void unregister_shrinker(struct shrinker *shrinker) 198{ 199 down_write(&shrinker_rwsem); 200 list_del(&shrinker->list); 201 up_write(&shrinker_rwsem); 202} 203EXPORT_SYMBOL(unregister_shrinker); 204 205static inline int do_shrinker_shrink(struct shrinker *shrinker, 206 struct shrink_control *sc, 207 unsigned long nr_to_scan) 208{ 209 sc->nr_to_scan = nr_to_scan; 210 return (*shrinker->shrink)(shrinker, sc); 211} 212 213#define SHRINK_BATCH 128 214/* 215 * Call the shrink functions to age shrinkable caches 216 * 217 * Here we assume it costs one seek to replace a lru page and that it also 218 * takes a seek to recreate a cache object. With this in mind we age equal 219 * percentages of the lru and ageable caches. This should balance the seeks 220 * generated by these structures. 221 * 222 * If the vm encountered mapped pages on the LRU it increase the pressure on 223 * slab to avoid swapping. 224 * 225 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 226 * 227 * `lru_pages' represents the number of on-LRU pages in all the zones which 228 * are eligible for the caller's allocation attempt. It is used for balancing 229 * slab reclaim versus page reclaim. 230 * 231 * Returns the number of slab objects which we shrunk. 232 */ 233unsigned long shrink_slab(struct shrink_control *shrink, 234 unsigned long nr_pages_scanned, 235 unsigned long lru_pages) 236{ 237 struct shrinker *shrinker; 238 unsigned long ret = 0; 239 240 if (nr_pages_scanned == 0) 241 nr_pages_scanned = SWAP_CLUSTER_MAX; 242 243 if (!down_read_trylock(&shrinker_rwsem)) { 244 /* Assume we'll be able to shrink next time */ 245 ret = 1; 246 goto out; 247 } 248 249 list_for_each_entry(shrinker, &shrinker_list, list) { 250 unsigned long long delta; 251 unsigned long total_scan; 252 unsigned long max_pass; 253 254 max_pass = do_shrinker_shrink(shrinker, shrink, 0); 255 delta = (4 * nr_pages_scanned) / shrinker->seeks; 256 delta *= max_pass; 257 do_div(delta, lru_pages + 1); 258 shrinker->nr += delta; 259 if (shrinker->nr < 0) { 260 printk(KERN_ERR "shrink_slab: %pF negative objects to " 261 "delete nr=%ld\n", 262 shrinker->shrink, shrinker->nr); 263 shrinker->nr = max_pass; 264 } 265 266 /* 267 * Avoid risking looping forever due to too large nr value: 268 * never try to free more than twice the estimate number of 269 * freeable entries. 270 */ 271 if (shrinker->nr > max_pass * 2) 272 shrinker->nr = max_pass * 2; 273 274 total_scan = shrinker->nr; 275 shrinker->nr = 0; 276 277 while (total_scan >= SHRINK_BATCH) { 278 long this_scan = SHRINK_BATCH; 279 int shrink_ret; 280 int nr_before; 281 282 nr_before = do_shrinker_shrink(shrinker, shrink, 0); 283 shrink_ret = do_shrinker_shrink(shrinker, shrink, 284 this_scan); 285 if (shrink_ret == -1) 286 break; 287 if (shrink_ret < nr_before) 288 ret += nr_before - shrink_ret; 289 count_vm_events(SLABS_SCANNED, this_scan); 290 total_scan -= this_scan; 291 292 cond_resched(); 293 } 294 295 shrinker->nr += total_scan; 296 } 297 up_read(&shrinker_rwsem); 298out: 299 cond_resched(); 300 return ret; 301} 302 303static void set_reclaim_mode(int priority, struct scan_control *sc, 304 bool sync) 305{ 306 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 307 308 /* 309 * Initially assume we are entering either lumpy reclaim or 310 * reclaim/compaction.Depending on the order, we will either set the 311 * sync mode or just reclaim order-0 pages later. 312 */ 313 if (COMPACTION_BUILD) 314 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 315 else 316 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 317 318 /* 319 * Avoid using lumpy reclaim or reclaim/compaction if possible by 320 * restricting when its set to either costly allocations or when 321 * under memory pressure 322 */ 323 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 324 sc->reclaim_mode |= syncmode; 325 else if (sc->order && priority < DEF_PRIORITY - 2) 326 sc->reclaim_mode |= syncmode; 327 else 328 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 329} 330 331static void reset_reclaim_mode(struct scan_control *sc) 332{ 333 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 334} 335 336static inline int is_page_cache_freeable(struct page *page) 337{ 338 /* 339 * A freeable page cache page is referenced only by the caller 340 * that isolated the page, the page cache radix tree and 341 * optional buffer heads at page->private. 342 */ 343 return page_count(page) - page_has_private(page) == 2; 344} 345 346static int may_write_to_queue(struct backing_dev_info *bdi, 347 struct scan_control *sc) 348{ 349 if (current->flags & PF_SWAPWRITE) 350 return 1; 351 if (!bdi_write_congested(bdi)) 352 return 1; 353 if (bdi == current->backing_dev_info) 354 return 1; 355 356 /* lumpy reclaim for hugepage often need a lot of write */ 357 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 358 return 1; 359 return 0; 360} 361 362/* 363 * We detected a synchronous write error writing a page out. Probably 364 * -ENOSPC. We need to propagate that into the address_space for a subsequent 365 * fsync(), msync() or close(). 366 * 367 * The tricky part is that after writepage we cannot touch the mapping: nothing 368 * prevents it from being freed up. But we have a ref on the page and once 369 * that page is locked, the mapping is pinned. 370 * 371 * We're allowed to run sleeping lock_page() here because we know the caller has 372 * __GFP_FS. 373 */ 374static void handle_write_error(struct address_space *mapping, 375 struct page *page, int error) 376{ 377 lock_page(page); 378 if (page_mapping(page) == mapping) 379 mapping_set_error(mapping, error); 380 unlock_page(page); 381} 382 383/* possible outcome of pageout() */ 384typedef enum { 385 /* failed to write page out, page is locked */ 386 PAGE_KEEP, 387 /* move page to the active list, page is locked */ 388 PAGE_ACTIVATE, 389 /* page has been sent to the disk successfully, page is unlocked */ 390 PAGE_SUCCESS, 391 /* page is clean and locked */ 392 PAGE_CLEAN, 393} pageout_t; 394 395/* 396 * pageout is called by shrink_page_list() for each dirty page. 397 * Calls ->writepage(). 398 */ 399static pageout_t pageout(struct page *page, struct address_space *mapping, 400 struct scan_control *sc) 401{ 402 /* 403 * If the page is dirty, only perform writeback if that write 404 * will be non-blocking. To prevent this allocation from being 405 * stalled by pagecache activity. But note that there may be 406 * stalls if we need to run get_block(). We could test 407 * PagePrivate for that. 408 * 409 * If this process is currently in __generic_file_aio_write() against 410 * this page's queue, we can perform writeback even if that 411 * will block. 412 * 413 * If the page is swapcache, write it back even if that would 414 * block, for some throttling. This happens by accident, because 415 * swap_backing_dev_info is bust: it doesn't reflect the 416 * congestion state of the swapdevs. Easy to fix, if needed. 417 */ 418 if (!is_page_cache_freeable(page)) 419 return PAGE_KEEP; 420 if (!mapping) { 421 /* 422 * Some data journaling orphaned pages can have 423 * page->mapping == NULL while being dirty with clean buffers. 424 */ 425 if (page_has_private(page)) { 426 if (try_to_free_buffers(page)) { 427 ClearPageDirty(page); 428 printk("%s: orphaned page\n", __func__); 429 return PAGE_CLEAN; 430 } 431 } 432 return PAGE_KEEP; 433 } 434 if (mapping->a_ops->writepage == NULL) 435 return PAGE_ACTIVATE; 436 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 437 return PAGE_KEEP; 438 439 if (clear_page_dirty_for_io(page)) { 440 int res; 441 struct writeback_control wbc = { 442 .sync_mode = WB_SYNC_NONE, 443 .nr_to_write = SWAP_CLUSTER_MAX, 444 .range_start = 0, 445 .range_end = LLONG_MAX, 446 .for_reclaim = 1, 447 }; 448 449 SetPageReclaim(page); 450 res = mapping->a_ops->writepage(page, &wbc); 451 if (res < 0) 452 handle_write_error(mapping, page, res); 453 if (res == AOP_WRITEPAGE_ACTIVATE) { 454 ClearPageReclaim(page); 455 return PAGE_ACTIVATE; 456 } 457 458 /* 459 * Wait on writeback if requested to. This happens when 460 * direct reclaiming a large contiguous area and the 461 * first attempt to free a range of pages fails. 462 */ 463 if (PageWriteback(page) && 464 (sc->reclaim_mode & RECLAIM_MODE_SYNC)) 465 wait_on_page_writeback(page); 466 467 if (!PageWriteback(page)) { 468 /* synchronous write or broken a_ops? */ 469 ClearPageReclaim(page); 470 } 471 trace_mm_vmscan_writepage(page, 472 trace_reclaim_flags(page, sc->reclaim_mode)); 473 inc_zone_page_state(page, NR_VMSCAN_WRITE); 474 return PAGE_SUCCESS; 475 } 476 477 return PAGE_CLEAN; 478} 479 480/* 481 * Same as remove_mapping, but if the page is removed from the mapping, it 482 * gets returned with a refcount of 0. 483 */ 484static int __remove_mapping(struct address_space *mapping, struct page *page) 485{ 486 BUG_ON(!PageLocked(page)); 487 BUG_ON(mapping != page_mapping(page)); 488 489 spin_lock_irq(&mapping->tree_lock); 490 /* 491 * The non racy check for a busy page. 492 * 493 * Must be careful with the order of the tests. When someone has 494 * a ref to the page, it may be possible that they dirty it then 495 * drop the reference. So if PageDirty is tested before page_count 496 * here, then the following race may occur: 497 * 498 * get_user_pages(&page); 499 * [user mapping goes away] 500 * write_to(page); 501 * !PageDirty(page) [good] 502 * SetPageDirty(page); 503 * put_page(page); 504 * !page_count(page) [good, discard it] 505 * 506 * [oops, our write_to data is lost] 507 * 508 * Reversing the order of the tests ensures such a situation cannot 509 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 510 * load is not satisfied before that of page->_count. 511 * 512 * Note that if SetPageDirty is always performed via set_page_dirty, 513 * and thus under tree_lock, then this ordering is not required. 514 */ 515 if (!page_freeze_refs(page, 2)) 516 goto cannot_free; 517 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 518 if (unlikely(PageDirty(page))) { 519 page_unfreeze_refs(page, 2); 520 goto cannot_free; 521 } 522 523 if (PageSwapCache(page)) { 524 swp_entry_t swap = { .val = page_private(page) }; 525 __delete_from_swap_cache(page); 526 spin_unlock_irq(&mapping->tree_lock); 527 swapcache_free(swap, page); 528 } else { 529 void (*freepage)(struct page *); 530 531 freepage = mapping->a_ops->freepage; 532 533 __delete_from_page_cache(page); 534 spin_unlock_irq(&mapping->tree_lock); 535 mem_cgroup_uncharge_cache_page(page); 536 537 if (freepage != NULL) 538 freepage(page); 539 } 540 541 return 1; 542 543cannot_free: 544 spin_unlock_irq(&mapping->tree_lock); 545 return 0; 546} 547 548/* 549 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 550 * someone else has a ref on the page, abort and return 0. If it was 551 * successfully detached, return 1. Assumes the caller has a single ref on 552 * this page. 553 */ 554int remove_mapping(struct address_space *mapping, struct page *page) 555{ 556 if (__remove_mapping(mapping, page)) { 557 /* 558 * Unfreezing the refcount with 1 rather than 2 effectively 559 * drops the pagecache ref for us without requiring another 560 * atomic operation. 561 */ 562 page_unfreeze_refs(page, 1); 563 return 1; 564 } 565 return 0; 566} 567 568/** 569 * putback_lru_page - put previously isolated page onto appropriate LRU list 570 * @page: page to be put back to appropriate lru list 571 * 572 * Add previously isolated @page to appropriate LRU list. 573 * Page may still be unevictable for other reasons. 574 * 575 * lru_lock must not be held, interrupts must be enabled. 576 */ 577void putback_lru_page(struct page *page) 578{ 579 int lru; 580 int active = !!TestClearPageActive(page); 581 int was_unevictable = PageUnevictable(page); 582 583 VM_BUG_ON(PageLRU(page)); 584 585redo: 586 ClearPageUnevictable(page); 587 588 if (page_evictable(page, NULL)) { 589 /* 590 * For evictable pages, we can use the cache. 591 * In event of a race, worst case is we end up with an 592 * unevictable page on [in]active list. 593 * We know how to handle that. 594 */ 595 lru = active + page_lru_base_type(page); 596 lru_cache_add_lru(page, lru); 597 } else { 598 /* 599 * Put unevictable pages directly on zone's unevictable 600 * list. 601 */ 602 lru = LRU_UNEVICTABLE; 603 add_page_to_unevictable_list(page); 604 /* 605 * When racing with an mlock clearing (page is 606 * unlocked), make sure that if the other thread does 607 * not observe our setting of PG_lru and fails 608 * isolation, we see PG_mlocked cleared below and move 609 * the page back to the evictable list. 610 * 611 * The other side is TestClearPageMlocked(). 612 */ 613 smp_mb(); 614 } 615 616 /* 617 * page's status can change while we move it among lru. If an evictable 618 * page is on unevictable list, it never be freed. To avoid that, 619 * check after we added it to the list, again. 620 */ 621 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 622 if (!isolate_lru_page(page)) { 623 put_page(page); 624 goto redo; 625 } 626 /* This means someone else dropped this page from LRU 627 * So, it will be freed or putback to LRU again. There is 628 * nothing to do here. 629 */ 630 } 631 632 if (was_unevictable && lru != LRU_UNEVICTABLE) 633 count_vm_event(UNEVICTABLE_PGRESCUED); 634 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 635 count_vm_event(UNEVICTABLE_PGCULLED); 636 637 put_page(page); /* drop ref from isolate */ 638} 639 640enum page_references { 641 PAGEREF_RECLAIM, 642 PAGEREF_RECLAIM_CLEAN, 643 PAGEREF_KEEP, 644 PAGEREF_ACTIVATE, 645}; 646 647static enum page_references page_check_references(struct page *page, 648 struct scan_control *sc) 649{ 650 int referenced_ptes, referenced_page; 651 unsigned long vm_flags; 652 653 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 654 referenced_page = TestClearPageReferenced(page); 655 656 /* Lumpy reclaim - ignore references */ 657 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 658 return PAGEREF_RECLAIM; 659 660 /* 661 * Mlock lost the isolation race with us. Let try_to_unmap() 662 * move the page to the unevictable list. 663 */ 664 if (vm_flags & VM_LOCKED) 665 return PAGEREF_RECLAIM; 666 667 if (referenced_ptes) { 668 if (PageAnon(page)) 669 return PAGEREF_ACTIVATE; 670 /* 671 * All mapped pages start out with page table 672 * references from the instantiating fault, so we need 673 * to look twice if a mapped file page is used more 674 * than once. 675 * 676 * Mark it and spare it for another trip around the 677 * inactive list. Another page table reference will 678 * lead to its activation. 679 * 680 * Note: the mark is set for activated pages as well 681 * so that recently deactivated but used pages are 682 * quickly recovered. 683 */ 684 SetPageReferenced(page); 685 686 if (referenced_page) 687 return PAGEREF_ACTIVATE; 688 689 return PAGEREF_KEEP; 690 } 691 692 /* Reclaim if clean, defer dirty pages to writeback */ 693 if (referenced_page && !PageSwapBacked(page)) 694 return PAGEREF_RECLAIM_CLEAN; 695 696 return PAGEREF_RECLAIM; 697} 698 699static noinline_for_stack void free_page_list(struct list_head *free_pages) 700{ 701 struct pagevec freed_pvec; 702 struct page *page, *tmp; 703 704 pagevec_init(&freed_pvec, 1); 705 706 list_for_each_entry_safe(page, tmp, free_pages, lru) { 707 list_del(&page->lru); 708 if (!pagevec_add(&freed_pvec, page)) { 709 __pagevec_free(&freed_pvec); 710 pagevec_reinit(&freed_pvec); 711 } 712 } 713 714 pagevec_free(&freed_pvec); 715} 716 717/* 718 * shrink_page_list() returns the number of reclaimed pages 719 */ 720static unsigned long shrink_page_list(struct list_head *page_list, 721 struct zone *zone, 722 struct scan_control *sc) 723{ 724 LIST_HEAD(ret_pages); 725 LIST_HEAD(free_pages); 726 int pgactivate = 0; 727 unsigned long nr_dirty = 0; 728 unsigned long nr_congested = 0; 729 unsigned long nr_reclaimed = 0; 730 731 cond_resched(); 732 733 while (!list_empty(page_list)) { 734 enum page_references references; 735 struct address_space *mapping; 736 struct page *page; 737 int may_enter_fs; 738 739 cond_resched(); 740 741 page = lru_to_page(page_list); 742 list_del(&page->lru); 743 744 if (!trylock_page(page)) 745 goto keep; 746 747 VM_BUG_ON(PageActive(page)); 748 VM_BUG_ON(page_zone(page) != zone); 749 750 sc->nr_scanned++; 751 752 if (unlikely(!page_evictable(page, NULL))) 753 goto cull_mlocked; 754 755 if (!sc->may_unmap && page_mapped(page)) 756 goto keep_locked; 757 758 /* Double the slab pressure for mapped and swapcache pages */ 759 if (page_mapped(page) || PageSwapCache(page)) 760 sc->nr_scanned++; 761 762 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 763 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 764 765 if (PageWriteback(page)) { 766 /* 767 * Synchronous reclaim is performed in two passes, 768 * first an asynchronous pass over the list to 769 * start parallel writeback, and a second synchronous 770 * pass to wait for the IO to complete. Wait here 771 * for any page for which writeback has already 772 * started. 773 */ 774 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 775 may_enter_fs) 776 wait_on_page_writeback(page); 777 else { 778 unlock_page(page); 779 goto keep_lumpy; 780 } 781 } 782 783 references = page_check_references(page, sc); 784 switch (references) { 785 case PAGEREF_ACTIVATE: 786 goto activate_locked; 787 case PAGEREF_KEEP: 788 goto keep_locked; 789 case PAGEREF_RECLAIM: 790 case PAGEREF_RECLAIM_CLEAN: 791 ; /* try to reclaim the page below */ 792 } 793 794 /* 795 * Anonymous process memory has backing store? 796 * Try to allocate it some swap space here. 797 */ 798 if (PageAnon(page) && !PageSwapCache(page)) { 799 if (!(sc->gfp_mask & __GFP_IO)) 800 goto keep_locked; 801 if (!add_to_swap(page)) 802 goto activate_locked; 803 may_enter_fs = 1; 804 } 805 806 mapping = page_mapping(page); 807 808 /* 809 * The page is mapped into the page tables of one or more 810 * processes. Try to unmap it here. 811 */ 812 if (page_mapped(page) && mapping) { 813 switch (try_to_unmap(page, TTU_UNMAP)) { 814 case SWAP_FAIL: 815 goto activate_locked; 816 case SWAP_AGAIN: 817 goto keep_locked; 818 case SWAP_MLOCK: 819 goto cull_mlocked; 820 case SWAP_SUCCESS: 821 ; /* try to free the page below */ 822 } 823 } 824 825 if (PageDirty(page)) { 826 nr_dirty++; 827 828 if (references == PAGEREF_RECLAIM_CLEAN) 829 goto keep_locked; 830 if (!may_enter_fs) 831 goto keep_locked; 832 if (!sc->may_writepage) 833 goto keep_locked; 834 835 /* Page is dirty, try to write it out here */ 836 switch (pageout(page, mapping, sc)) { 837 case PAGE_KEEP: 838 nr_congested++; 839 goto keep_locked; 840 case PAGE_ACTIVATE: 841 goto activate_locked; 842 case PAGE_SUCCESS: 843 if (PageWriteback(page)) 844 goto keep_lumpy; 845 if (PageDirty(page)) 846 goto keep; 847 848 /* 849 * A synchronous write - probably a ramdisk. Go 850 * ahead and try to reclaim the page. 851 */ 852 if (!trylock_page(page)) 853 goto keep; 854 if (PageDirty(page) || PageWriteback(page)) 855 goto keep_locked; 856 mapping = page_mapping(page); 857 case PAGE_CLEAN: 858 ; /* try to free the page below */ 859 } 860 } 861 862 /* 863 * If the page has buffers, try to free the buffer mappings 864 * associated with this page. If we succeed we try to free 865 * the page as well. 866 * 867 * We do this even if the page is PageDirty(). 868 * try_to_release_page() does not perform I/O, but it is 869 * possible for a page to have PageDirty set, but it is actually 870 * clean (all its buffers are clean). This happens if the 871 * buffers were written out directly, with submit_bh(). ext3 872 * will do this, as well as the blockdev mapping. 873 * try_to_release_page() will discover that cleanness and will 874 * drop the buffers and mark the page clean - it can be freed. 875 * 876 * Rarely, pages can have buffers and no ->mapping. These are 877 * the pages which were not successfully invalidated in 878 * truncate_complete_page(). We try to drop those buffers here 879 * and if that worked, and the page is no longer mapped into 880 * process address space (page_count == 1) it can be freed. 881 * Otherwise, leave the page on the LRU so it is swappable. 882 */ 883 if (page_has_private(page)) { 884 if (!try_to_release_page(page, sc->gfp_mask)) 885 goto activate_locked; 886 if (!mapping && page_count(page) == 1) { 887 unlock_page(page); 888 if (put_page_testzero(page)) 889 goto free_it; 890 else { 891 /* 892 * rare race with speculative reference. 893 * the speculative reference will free 894 * this page shortly, so we may 895 * increment nr_reclaimed here (and 896 * leave it off the LRU). 897 */ 898 nr_reclaimed++; 899 continue; 900 } 901 } 902 } 903 904 if (!mapping || !__remove_mapping(mapping, page)) 905 goto keep_locked; 906 907 /* 908 * At this point, we have no other references and there is 909 * no way to pick any more up (removed from LRU, removed 910 * from pagecache). Can use non-atomic bitops now (and 911 * we obviously don't have to worry about waking up a process 912 * waiting on the page lock, because there are no references. 913 */ 914 __clear_page_locked(page); 915free_it: 916 nr_reclaimed++; 917 918 /* 919 * Is there need to periodically free_page_list? It would 920 * appear not as the counts should be low 921 */ 922 list_add(&page->lru, &free_pages); 923 continue; 924 925cull_mlocked: 926 if (PageSwapCache(page)) 927 try_to_free_swap(page); 928 unlock_page(page); 929 putback_lru_page(page); 930 reset_reclaim_mode(sc); 931 continue; 932 933activate_locked: 934 /* Not a candidate for swapping, so reclaim swap space. */ 935 if (PageSwapCache(page) && vm_swap_full()) 936 try_to_free_swap(page); 937 VM_BUG_ON(PageActive(page)); 938 SetPageActive(page); 939 pgactivate++; 940keep_locked: 941 unlock_page(page); 942keep: 943 reset_reclaim_mode(sc); 944keep_lumpy: 945 list_add(&page->lru, &ret_pages); 946 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 947 } 948 949 /* 950 * Tag a zone as congested if all the dirty pages encountered were 951 * backed by a congested BDI. In this case, reclaimers should just 952 * back off and wait for congestion to clear because further reclaim 953 * will encounter the same problem 954 */ 955 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) 956 zone_set_flag(zone, ZONE_CONGESTED); 957 958 free_page_list(&free_pages); 959 960 list_splice(&ret_pages, page_list); 961 count_vm_events(PGACTIVATE, pgactivate); 962 return nr_reclaimed; 963} 964 965/* 966 * Attempt to remove the specified page from its LRU. Only take this page 967 * if it is of the appropriate PageActive status. Pages which are being 968 * freed elsewhere are also ignored. 969 * 970 * page: page to consider 971 * mode: one of the LRU isolation modes defined above 972 * 973 * returns 0 on success, -ve errno on failure. 974 */ 975int __isolate_lru_page(struct page *page, int mode, int file) 976{ 977 int ret = -EINVAL; 978 979 /* Only take pages on the LRU. */ 980 if (!PageLRU(page)) 981 return ret; 982 983 /* 984 * When checking the active state, we need to be sure we are 985 * dealing with comparible boolean values. Take the logical not 986 * of each. 987 */ 988 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 989 return ret; 990 991 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 992 return ret; 993 994 /* 995 * When this function is being called for lumpy reclaim, we 996 * initially look into all LRU pages, active, inactive and 997 * unevictable; only give shrink_page_list evictable pages. 998 */ 999 if (PageUnevictable(page)) 1000 return ret; 1001 1002 ret = -EBUSY; 1003 1004 if (likely(get_page_unless_zero(page))) { 1005 /* 1006 * Be careful not to clear PageLRU until after we're 1007 * sure the page is not being freed elsewhere -- the 1008 * page release code relies on it. 1009 */ 1010 ClearPageLRU(page); 1011 ret = 0; 1012 } 1013 1014 return ret; 1015} 1016 1017/* 1018 * zone->lru_lock is heavily contended. Some of the functions that 1019 * shrink the lists perform better by taking out a batch of pages 1020 * and working on them outside the LRU lock. 1021 * 1022 * For pagecache intensive workloads, this function is the hottest 1023 * spot in the kernel (apart from copy_*_user functions). 1024 * 1025 * Appropriate locks must be held before calling this function. 1026 * 1027 * @nr_to_scan: The number of pages to look through on the list. 1028 * @src: The LRU list to pull pages off. 1029 * @dst: The temp list to put pages on to. 1030 * @scanned: The number of pages that were scanned. 1031 * @order: The caller's attempted allocation order 1032 * @mode: One of the LRU isolation modes 1033 * @file: True [1] if isolating file [!anon] pages 1034 * 1035 * returns how many pages were moved onto *@dst. 1036 */ 1037static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1038 struct list_head *src, struct list_head *dst, 1039 unsigned long *scanned, int order, int mode, int file) 1040{ 1041 unsigned long nr_taken = 0; 1042 unsigned long nr_lumpy_taken = 0; 1043 unsigned long nr_lumpy_dirty = 0; 1044 unsigned long nr_lumpy_failed = 0; 1045 unsigned long scan; 1046 1047 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1048 struct page *page; 1049 unsigned long pfn; 1050 unsigned long end_pfn; 1051 unsigned long page_pfn; 1052 int zone_id; 1053 1054 page = lru_to_page(src); 1055 prefetchw_prev_lru_page(page, src, flags); 1056 1057 VM_BUG_ON(!PageLRU(page)); 1058 1059 switch (__isolate_lru_page(page, mode, file)) { 1060 case 0: 1061 list_move(&page->lru, dst); 1062 mem_cgroup_del_lru(page); 1063 nr_taken += hpage_nr_pages(page); 1064 break; 1065 1066 case -EBUSY: 1067 /* else it is being freed elsewhere */ 1068 list_move(&page->lru, src); 1069 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1070 continue; 1071 1072 default: 1073 BUG(); 1074 } 1075 1076 if (!order) 1077 continue; 1078 1079 /* 1080 * Attempt to take all pages in the order aligned region 1081 * surrounding the tag page. Only take those pages of 1082 * the same active state as that tag page. We may safely 1083 * round the target page pfn down to the requested order 1084 * as the mem_map is guaranteed valid out to MAX_ORDER, 1085 * where that page is in a different zone we will detect 1086 * it from its zone id and abort this block scan. 1087 */ 1088 zone_id = page_zone_id(page); 1089 page_pfn = page_to_pfn(page); 1090 pfn = page_pfn & ~((1 << order) - 1); 1091 end_pfn = pfn + (1 << order); 1092 for (; pfn < end_pfn; pfn++) { 1093 struct page *cursor_page; 1094 1095 /* The target page is in the block, ignore it. */ 1096 if (unlikely(pfn == page_pfn)) 1097 continue; 1098 1099 /* Avoid holes within the zone. */ 1100 if (unlikely(!pfn_valid_within(pfn))) 1101 break; 1102 1103 cursor_page = pfn_to_page(pfn); 1104 1105 /* Check that we have not crossed a zone boundary. */ 1106 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1107 break; 1108 1109 /* 1110 * If we don't have enough swap space, reclaiming of 1111 * anon page which don't already have a swap slot is 1112 * pointless. 1113 */ 1114 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1115 !PageSwapCache(cursor_page)) 1116 break; 1117 1118 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1119 list_move(&cursor_page->lru, dst); 1120 mem_cgroup_del_lru(cursor_page); 1121 nr_taken += hpage_nr_pages(page); 1122 nr_lumpy_taken++; 1123 if (PageDirty(cursor_page)) 1124 nr_lumpy_dirty++; 1125 scan++; 1126 } else { 1127 /* the page is freed already. */ 1128 if (!page_count(cursor_page)) 1129 continue; 1130 break; 1131 } 1132 } 1133 1134 /* If we break out of the loop above, lumpy reclaim failed */ 1135 if (pfn < end_pfn) 1136 nr_lumpy_failed++; 1137 } 1138 1139 *scanned = scan; 1140 1141 trace_mm_vmscan_lru_isolate(order, 1142 nr_to_scan, scan, 1143 nr_taken, 1144 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1145 mode); 1146 return nr_taken; 1147} 1148 1149static unsigned long isolate_pages_global(unsigned long nr, 1150 struct list_head *dst, 1151 unsigned long *scanned, int order, 1152 int mode, struct zone *z, 1153 int active, int file) 1154{ 1155 int lru = LRU_BASE; 1156 if (active) 1157 lru += LRU_ACTIVE; 1158 if (file) 1159 lru += LRU_FILE; 1160 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1161 mode, file); 1162} 1163 1164/* 1165 * clear_active_flags() is a helper for shrink_active_list(), clearing 1166 * any active bits from the pages in the list. 1167 */ 1168static unsigned long clear_active_flags(struct list_head *page_list, 1169 unsigned int *count) 1170{ 1171 int nr_active = 0; 1172 int lru; 1173 struct page *page; 1174 1175 list_for_each_entry(page, page_list, lru) { 1176 int numpages = hpage_nr_pages(page); 1177 lru = page_lru_base_type(page); 1178 if (PageActive(page)) { 1179 lru += LRU_ACTIVE; 1180 ClearPageActive(page); 1181 nr_active += numpages; 1182 } 1183 if (count) 1184 count[lru] += numpages; 1185 } 1186 1187 return nr_active; 1188} 1189 1190/** 1191 * isolate_lru_page - tries to isolate a page from its LRU list 1192 * @page: page to isolate from its LRU list 1193 * 1194 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1195 * vmstat statistic corresponding to whatever LRU list the page was on. 1196 * 1197 * Returns 0 if the page was removed from an LRU list. 1198 * Returns -EBUSY if the page was not on an LRU list. 1199 * 1200 * The returned page will have PageLRU() cleared. If it was found on 1201 * the active list, it will have PageActive set. If it was found on 1202 * the unevictable list, it will have the PageUnevictable bit set. That flag 1203 * may need to be cleared by the caller before letting the page go. 1204 * 1205 * The vmstat statistic corresponding to the list on which the page was 1206 * found will be decremented. 1207 * 1208 * Restrictions: 1209 * (1) Must be called with an elevated refcount on the page. This is a 1210 * fundamentnal difference from isolate_lru_pages (which is called 1211 * without a stable reference). 1212 * (2) the lru_lock must not be held. 1213 * (3) interrupts must be enabled. 1214 */ 1215int isolate_lru_page(struct page *page) 1216{ 1217 int ret = -EBUSY; 1218 1219 VM_BUG_ON(!page_count(page)); 1220 1221 if (PageLRU(page)) { 1222 struct zone *zone = page_zone(page); 1223 1224 spin_lock_irq(&zone->lru_lock); 1225 if (PageLRU(page)) { 1226 int lru = page_lru(page); 1227 ret = 0; 1228 get_page(page); 1229 ClearPageLRU(page); 1230 1231 del_page_from_lru_list(zone, page, lru); 1232 } 1233 spin_unlock_irq(&zone->lru_lock); 1234 } 1235 return ret; 1236} 1237 1238/* 1239 * Are there way too many processes in the direct reclaim path already? 1240 */ 1241static int too_many_isolated(struct zone *zone, int file, 1242 struct scan_control *sc) 1243{ 1244 unsigned long inactive, isolated; 1245 1246 if (current_is_kswapd()) 1247 return 0; 1248 1249 if (!scanning_global_lru(sc)) 1250 return 0; 1251 1252 if (file) { 1253 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1254 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1255 } else { 1256 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1257 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1258 } 1259 1260 return isolated > inactive; 1261} 1262 1263/* 1264 * TODO: Try merging with migrations version of putback_lru_pages 1265 */ 1266static noinline_for_stack void 1267putback_lru_pages(struct zone *zone, struct scan_control *sc, 1268 unsigned long nr_anon, unsigned long nr_file, 1269 struct list_head *page_list) 1270{ 1271 struct page *page; 1272 struct pagevec pvec; 1273 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1274 1275 pagevec_init(&pvec, 1); 1276 1277 /* 1278 * Put back any unfreeable pages. 1279 */ 1280 spin_lock(&zone->lru_lock); 1281 while (!list_empty(page_list)) { 1282 int lru; 1283 page = lru_to_page(page_list); 1284 VM_BUG_ON(PageLRU(page)); 1285 list_del(&page->lru); 1286 if (unlikely(!page_evictable(page, NULL))) { 1287 spin_unlock_irq(&zone->lru_lock); 1288 putback_lru_page(page); 1289 spin_lock_irq(&zone->lru_lock); 1290 continue; 1291 } 1292 SetPageLRU(page); 1293 lru = page_lru(page); 1294 add_page_to_lru_list(zone, page, lru); 1295 if (is_active_lru(lru)) { 1296 int file = is_file_lru(lru); 1297 int numpages = hpage_nr_pages(page); 1298 reclaim_stat->recent_rotated[file] += numpages; 1299 } 1300 if (!pagevec_add(&pvec, page)) { 1301 spin_unlock_irq(&zone->lru_lock); 1302 __pagevec_release(&pvec); 1303 spin_lock_irq(&zone->lru_lock); 1304 } 1305 } 1306 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1307 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1308 1309 spin_unlock_irq(&zone->lru_lock); 1310 pagevec_release(&pvec); 1311} 1312 1313static noinline_for_stack void update_isolated_counts(struct zone *zone, 1314 struct scan_control *sc, 1315 unsigned long *nr_anon, 1316 unsigned long *nr_file, 1317 struct list_head *isolated_list) 1318{ 1319 unsigned long nr_active; 1320 unsigned int count[NR_LRU_LISTS] = { 0, }; 1321 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1322 1323 nr_active = clear_active_flags(isolated_list, count); 1324 __count_vm_events(PGDEACTIVATE, nr_active); 1325 1326 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1327 -count[LRU_ACTIVE_FILE]); 1328 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1329 -count[LRU_INACTIVE_FILE]); 1330 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1331 -count[LRU_ACTIVE_ANON]); 1332 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1333 -count[LRU_INACTIVE_ANON]); 1334 1335 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1336 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1337 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1338 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1339 1340 reclaim_stat->recent_scanned[0] += *nr_anon; 1341 reclaim_stat->recent_scanned[1] += *nr_file; 1342} 1343 1344/* 1345 * Returns true if the caller should wait to clean dirty/writeback pages. 1346 * 1347 * If we are direct reclaiming for contiguous pages and we do not reclaim 1348 * everything in the list, try again and wait for writeback IO to complete. 1349 * This will stall high-order allocations noticeably. Only do that when really 1350 * need to free the pages under high memory pressure. 1351 */ 1352static inline bool should_reclaim_stall(unsigned long nr_taken, 1353 unsigned long nr_freed, 1354 int priority, 1355 struct scan_control *sc) 1356{ 1357 int lumpy_stall_priority; 1358 1359 /* kswapd should not stall on sync IO */ 1360 if (current_is_kswapd()) 1361 return false; 1362 1363 /* Only stall on lumpy reclaim */ 1364 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1365 return false; 1366 1367 /* If we have relaimed everything on the isolated list, no stall */ 1368 if (nr_freed == nr_taken) 1369 return false; 1370 1371 /* 1372 * For high-order allocations, there are two stall thresholds. 1373 * High-cost allocations stall immediately where as lower 1374 * order allocations such as stacks require the scanning 1375 * priority to be much higher before stalling. 1376 */ 1377 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1378 lumpy_stall_priority = DEF_PRIORITY; 1379 else 1380 lumpy_stall_priority = DEF_PRIORITY / 3; 1381 1382 return priority <= lumpy_stall_priority; 1383} 1384 1385/* 1386 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1387 * of reclaimed pages 1388 */ 1389static noinline_for_stack unsigned long 1390shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1391 struct scan_control *sc, int priority, int file) 1392{ 1393 LIST_HEAD(page_list); 1394 unsigned long nr_scanned; 1395 unsigned long nr_reclaimed = 0; 1396 unsigned long nr_taken; 1397 unsigned long nr_anon; 1398 unsigned long nr_file; 1399 1400 while (unlikely(too_many_isolated(zone, file, sc))) { 1401 congestion_wait(BLK_RW_ASYNC, HZ/10); 1402 1403 /* We are about to die and free our memory. Return now. */ 1404 if (fatal_signal_pending(current)) 1405 return SWAP_CLUSTER_MAX; 1406 } 1407 1408 set_reclaim_mode(priority, sc, false); 1409 lru_add_drain(); 1410 spin_lock_irq(&zone->lru_lock); 1411 1412 if (scanning_global_lru(sc)) { 1413 nr_taken = isolate_pages_global(nr_to_scan, 1414 &page_list, &nr_scanned, sc->order, 1415 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1416 ISOLATE_BOTH : ISOLATE_INACTIVE, 1417 zone, 0, file); 1418 zone->pages_scanned += nr_scanned; 1419 if (current_is_kswapd()) 1420 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1421 nr_scanned); 1422 else 1423 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1424 nr_scanned); 1425 } else { 1426 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1427 &page_list, &nr_scanned, sc->order, 1428 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1429 ISOLATE_BOTH : ISOLATE_INACTIVE, 1430 zone, sc->mem_cgroup, 1431 0, file); 1432 /* 1433 * mem_cgroup_isolate_pages() keeps track of 1434 * scanned pages on its own. 1435 */ 1436 } 1437 1438 if (nr_taken == 0) { 1439 spin_unlock_irq(&zone->lru_lock); 1440 return 0; 1441 } 1442 1443 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1444 1445 spin_unlock_irq(&zone->lru_lock); 1446 1447 nr_reclaimed = shrink_page_list(&page_list, zone, sc); 1448 1449 /* Check if we should syncronously wait for writeback */ 1450 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1451 set_reclaim_mode(priority, sc, true); 1452 nr_reclaimed += shrink_page_list(&page_list, zone, sc); 1453 } 1454 1455 local_irq_disable(); 1456 if (current_is_kswapd()) 1457 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1458 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1459 1460 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1461 1462 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1463 zone_idx(zone), 1464 nr_scanned, nr_reclaimed, 1465 priority, 1466 trace_shrink_flags(file, sc->reclaim_mode)); 1467 return nr_reclaimed; 1468} 1469 1470/* 1471 * This moves pages from the active list to the inactive list. 1472 * 1473 * We move them the other way if the page is referenced by one or more 1474 * processes, from rmap. 1475 * 1476 * If the pages are mostly unmapped, the processing is fast and it is 1477 * appropriate to hold zone->lru_lock across the whole operation. But if 1478 * the pages are mapped, the processing is slow (page_referenced()) so we 1479 * should drop zone->lru_lock around each page. It's impossible to balance 1480 * this, so instead we remove the pages from the LRU while processing them. 1481 * It is safe to rely on PG_active against the non-LRU pages in here because 1482 * nobody will play with that bit on a non-LRU page. 1483 * 1484 * The downside is that we have to touch page->_count against each page. 1485 * But we had to alter page->flags anyway. 1486 */ 1487 1488static void move_active_pages_to_lru(struct zone *zone, 1489 struct list_head *list, 1490 enum lru_list lru) 1491{ 1492 unsigned long pgmoved = 0; 1493 struct pagevec pvec; 1494 struct page *page; 1495 1496 pagevec_init(&pvec, 1); 1497 1498 while (!list_empty(list)) { 1499 page = lru_to_page(list); 1500 1501 VM_BUG_ON(PageLRU(page)); 1502 SetPageLRU(page); 1503 1504 list_move(&page->lru, &zone->lru[lru].list); 1505 mem_cgroup_add_lru_list(page, lru); 1506 pgmoved += hpage_nr_pages(page); 1507 1508 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1509 spin_unlock_irq(&zone->lru_lock); 1510 if (buffer_heads_over_limit) 1511 pagevec_strip(&pvec); 1512 __pagevec_release(&pvec); 1513 spin_lock_irq(&zone->lru_lock); 1514 } 1515 } 1516 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1517 if (!is_active_lru(lru)) 1518 __count_vm_events(PGDEACTIVATE, pgmoved); 1519} 1520 1521static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1522 struct scan_control *sc, int priority, int file) 1523{ 1524 unsigned long nr_taken; 1525 unsigned long pgscanned; 1526 unsigned long vm_flags; 1527 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1528 LIST_HEAD(l_active); 1529 LIST_HEAD(l_inactive); 1530 struct page *page; 1531 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1532 unsigned long nr_rotated = 0; 1533 1534 lru_add_drain(); 1535 spin_lock_irq(&zone->lru_lock); 1536 if (scanning_global_lru(sc)) { 1537 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1538 &pgscanned, sc->order, 1539 ISOLATE_ACTIVE, zone, 1540 1, file); 1541 zone->pages_scanned += pgscanned; 1542 } else { 1543 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1544 &pgscanned, sc->order, 1545 ISOLATE_ACTIVE, zone, 1546 sc->mem_cgroup, 1, file); 1547 /* 1548 * mem_cgroup_isolate_pages() keeps track of 1549 * scanned pages on its own. 1550 */ 1551 } 1552 1553 reclaim_stat->recent_scanned[file] += nr_taken; 1554 1555 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1556 if (file) 1557 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1558 else 1559 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1560 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1561 spin_unlock_irq(&zone->lru_lock); 1562 1563 while (!list_empty(&l_hold)) { 1564 cond_resched(); 1565 page = lru_to_page(&l_hold); 1566 list_del(&page->lru); 1567 1568 if (unlikely(!page_evictable(page, NULL))) { 1569 putback_lru_page(page); 1570 continue; 1571 } 1572 1573 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1574 nr_rotated += hpage_nr_pages(page); 1575 /* 1576 * Identify referenced, file-backed active pages and 1577 * give them one more trip around the active list. So 1578 * that executable code get better chances to stay in 1579 * memory under moderate memory pressure. Anon pages 1580 * are not likely to be evicted by use-once streaming 1581 * IO, plus JVM can create lots of anon VM_EXEC pages, 1582 * so we ignore them here. 1583 */ 1584 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1585 list_add(&page->lru, &l_active); 1586 continue; 1587 } 1588 } 1589 1590 ClearPageActive(page); /* we are de-activating */ 1591 list_add(&page->lru, &l_inactive); 1592 } 1593 1594 /* 1595 * Move pages back to the lru list. 1596 */ 1597 spin_lock_irq(&zone->lru_lock); 1598 /* 1599 * Count referenced pages from currently used mappings as rotated, 1600 * even though only some of them are actually re-activated. This 1601 * helps balance scan pressure between file and anonymous pages in 1602 * get_scan_ratio. 1603 */ 1604 reclaim_stat->recent_rotated[file] += nr_rotated; 1605 1606 move_active_pages_to_lru(zone, &l_active, 1607 LRU_ACTIVE + file * LRU_FILE); 1608 move_active_pages_to_lru(zone, &l_inactive, 1609 LRU_BASE + file * LRU_FILE); 1610 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1611 spin_unlock_irq(&zone->lru_lock); 1612} 1613 1614#ifdef CONFIG_SWAP 1615static int inactive_anon_is_low_global(struct zone *zone) 1616{ 1617 unsigned long active, inactive; 1618 1619 active = zone_page_state(zone, NR_ACTIVE_ANON); 1620 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1621 1622 if (inactive * zone->inactive_ratio < active) 1623 return 1; 1624 1625 return 0; 1626} 1627 1628/** 1629 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1630 * @zone: zone to check 1631 * @sc: scan control of this context 1632 * 1633 * Returns true if the zone does not have enough inactive anon pages, 1634 * meaning some active anon pages need to be deactivated. 1635 */ 1636static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1637{ 1638 int low; 1639 1640 /* 1641 * If we don't have swap space, anonymous page deactivation 1642 * is pointless. 1643 */ 1644 if (!total_swap_pages) 1645 return 0; 1646 1647 if (scanning_global_lru(sc)) 1648 low = inactive_anon_is_low_global(zone); 1649 else 1650 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1651 return low; 1652} 1653#else 1654static inline int inactive_anon_is_low(struct zone *zone, 1655 struct scan_control *sc) 1656{ 1657 return 0; 1658} 1659#endif 1660 1661static int inactive_file_is_low_global(struct zone *zone) 1662{ 1663 unsigned long active, inactive; 1664 1665 active = zone_page_state(zone, NR_ACTIVE_FILE); 1666 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1667 1668 return (active > inactive); 1669} 1670 1671/** 1672 * inactive_file_is_low - check if file pages need to be deactivated 1673 * @zone: zone to check 1674 * @sc: scan control of this context 1675 * 1676 * When the system is doing streaming IO, memory pressure here 1677 * ensures that active file pages get deactivated, until more 1678 * than half of the file pages are on the inactive list. 1679 * 1680 * Once we get to that situation, protect the system's working 1681 * set from being evicted by disabling active file page aging. 1682 * 1683 * This uses a different ratio than the anonymous pages, because 1684 * the page cache uses a use-once replacement algorithm. 1685 */ 1686static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1687{ 1688 int low; 1689 1690 if (scanning_global_lru(sc)) 1691 low = inactive_file_is_low_global(zone); 1692 else 1693 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1694 return low; 1695} 1696 1697static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1698 int file) 1699{ 1700 if (file) 1701 return inactive_file_is_low(zone, sc); 1702 else 1703 return inactive_anon_is_low(zone, sc); 1704} 1705 1706static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1707 struct zone *zone, struct scan_control *sc, int priority) 1708{ 1709 int file = is_file_lru(lru); 1710 1711 if (is_active_lru(lru)) { 1712 if (inactive_list_is_low(zone, sc, file)) 1713 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1714 return 0; 1715 } 1716 1717 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1718} 1719 1720/* 1721 * Determine how aggressively the anon and file LRU lists should be 1722 * scanned. The relative value of each set of LRU lists is determined 1723 * by looking at the fraction of the pages scanned we did rotate back 1724 * onto the active list instead of evict. 1725 * 1726 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1727 */ 1728static void get_scan_count(struct zone *zone, struct scan_control *sc, 1729 unsigned long *nr, int priority) 1730{ 1731 unsigned long anon, file, free; 1732 unsigned long anon_prio, file_prio; 1733 unsigned long ap, fp; 1734 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1735 u64 fraction[2], denominator; 1736 enum lru_list l; 1737 int noswap = 0; 1738 int force_scan = 0; 1739 1740 1741 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1742 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1743 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1744 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1745 1746 if (((anon + file) >> priority) < SWAP_CLUSTER_MAX) { 1747 /* kswapd does zone balancing and need to scan this zone */ 1748 if (scanning_global_lru(sc) && current_is_kswapd()) 1749 force_scan = 1; 1750 /* memcg may have small limit and need to avoid priority drop */ 1751 if (!scanning_global_lru(sc)) 1752 force_scan = 1; 1753 } 1754 1755 /* If we have no swap space, do not bother scanning anon pages. */ 1756 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1757 noswap = 1; 1758 fraction[0] = 0; 1759 fraction[1] = 1; 1760 denominator = 1; 1761 goto out; 1762 } 1763 1764 if (scanning_global_lru(sc)) { 1765 free = zone_page_state(zone, NR_FREE_PAGES); 1766 /* If we have very few page cache pages, 1767 force-scan anon pages. */ 1768 if (unlikely(file + free <= high_wmark_pages(zone))) { 1769 fraction[0] = 1; 1770 fraction[1] = 0; 1771 denominator = 1; 1772 goto out; 1773 } 1774 } 1775 1776 /* 1777 * With swappiness at 100, anonymous and file have the same priority. 1778 * This scanning priority is essentially the inverse of IO cost. 1779 */ 1780 anon_prio = sc->swappiness; 1781 file_prio = 200 - sc->swappiness; 1782 1783 /* 1784 * OK, so we have swap space and a fair amount of page cache 1785 * pages. We use the recently rotated / recently scanned 1786 * ratios to determine how valuable each cache is. 1787 * 1788 * Because workloads change over time (and to avoid overflow) 1789 * we keep these statistics as a floating average, which ends 1790 * up weighing recent references more than old ones. 1791 * 1792 * anon in [0], file in [1] 1793 */ 1794 spin_lock_irq(&zone->lru_lock); 1795 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1796 reclaim_stat->recent_scanned[0] /= 2; 1797 reclaim_stat->recent_rotated[0] /= 2; 1798 } 1799 1800 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1801 reclaim_stat->recent_scanned[1] /= 2; 1802 reclaim_stat->recent_rotated[1] /= 2; 1803 } 1804 1805 /* 1806 * The amount of pressure on anon vs file pages is inversely 1807 * proportional to the fraction of recently scanned pages on 1808 * each list that were recently referenced and in active use. 1809 */ 1810 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1811 ap /= reclaim_stat->recent_rotated[0] + 1; 1812 1813 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1814 fp /= reclaim_stat->recent_rotated[1] + 1; 1815 spin_unlock_irq(&zone->lru_lock); 1816 1817 fraction[0] = ap; 1818 fraction[1] = fp; 1819 denominator = ap + fp + 1; 1820out: 1821 for_each_evictable_lru(l) { 1822 int file = is_file_lru(l); 1823 unsigned long scan; 1824 1825 scan = zone_nr_lru_pages(zone, sc, l); 1826 if (priority || noswap) { 1827 scan >>= priority; 1828 scan = div64_u64(scan * fraction[file], denominator); 1829 } 1830 1831 /* 1832 * If zone is small or memcg is small, nr[l] can be 0. 1833 * This results no-scan on this priority and priority drop down. 1834 * For global direct reclaim, it can visit next zone and tend 1835 * not to have problems. For global kswapd, it's for zone 1836 * balancing and it need to scan a small amounts. When using 1837 * memcg, priority drop can cause big latency. So, it's better 1838 * to scan small amount. See may_noscan above. 1839 */ 1840 if (!scan && force_scan) { 1841 if (file) 1842 scan = SWAP_CLUSTER_MAX; 1843 else if (!noswap) 1844 scan = SWAP_CLUSTER_MAX; 1845 } 1846 nr[l] = scan; 1847 } 1848} 1849 1850/* 1851 * Reclaim/compaction depends on a number of pages being freed. To avoid 1852 * disruption to the system, a small number of order-0 pages continue to be 1853 * rotated and reclaimed in the normal fashion. However, by the time we get 1854 * back to the allocator and call try_to_compact_zone(), we ensure that 1855 * there are enough free pages for it to be likely successful 1856 */ 1857static inline bool should_continue_reclaim(struct zone *zone, 1858 unsigned long nr_reclaimed, 1859 unsigned long nr_scanned, 1860 struct scan_control *sc) 1861{ 1862 unsigned long pages_for_compaction; 1863 unsigned long inactive_lru_pages; 1864 1865 /* If not in reclaim/compaction mode, stop */ 1866 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1867 return false; 1868 1869 /* Consider stopping depending on scan and reclaim activity */ 1870 if (sc->gfp_mask & __GFP_REPEAT) { 1871 /* 1872 * For __GFP_REPEAT allocations, stop reclaiming if the 1873 * full LRU list has been scanned and we are still failing 1874 * to reclaim pages. This full LRU scan is potentially 1875 * expensive but a __GFP_REPEAT caller really wants to succeed 1876 */ 1877 if (!nr_reclaimed && !nr_scanned) 1878 return false; 1879 } else { 1880 /* 1881 * For non-__GFP_REPEAT allocations which can presumably 1882 * fail without consequence, stop if we failed to reclaim 1883 * any pages from the last SWAP_CLUSTER_MAX number of 1884 * pages that were scanned. This will return to the 1885 * caller faster at the risk reclaim/compaction and 1886 * the resulting allocation attempt fails 1887 */ 1888 if (!nr_reclaimed) 1889 return false; 1890 } 1891 1892 /* 1893 * If we have not reclaimed enough pages for compaction and the 1894 * inactive lists are large enough, continue reclaiming 1895 */ 1896 pages_for_compaction = (2UL << sc->order); 1897 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 1898 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1899 if (sc->nr_reclaimed < pages_for_compaction && 1900 inactive_lru_pages > pages_for_compaction) 1901 return true; 1902 1903 /* If compaction would go ahead or the allocation would succeed, stop */ 1904 switch (compaction_suitable(zone, sc->order)) { 1905 case COMPACT_PARTIAL: 1906 case COMPACT_CONTINUE: 1907 return false; 1908 default: 1909 return true; 1910 } 1911} 1912 1913/* 1914 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1915 */ 1916static void shrink_zone(int priority, struct zone *zone, 1917 struct scan_control *sc) 1918{ 1919 unsigned long nr[NR_LRU_LISTS]; 1920 unsigned long nr_to_scan; 1921 enum lru_list l; 1922 unsigned long nr_reclaimed, nr_scanned; 1923 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1924 1925restart: 1926 nr_reclaimed = 0; 1927 nr_scanned = sc->nr_scanned; 1928 get_scan_count(zone, sc, nr, priority); 1929 1930 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1931 nr[LRU_INACTIVE_FILE]) { 1932 for_each_evictable_lru(l) { 1933 if (nr[l]) { 1934 nr_to_scan = min_t(unsigned long, 1935 nr[l], SWAP_CLUSTER_MAX); 1936 nr[l] -= nr_to_scan; 1937 1938 nr_reclaimed += shrink_list(l, nr_to_scan, 1939 zone, sc, priority); 1940 } 1941 } 1942 /* 1943 * On large memory systems, scan >> priority can become 1944 * really large. This is fine for the starting priority; 1945 * we want to put equal scanning pressure on each zone. 1946 * However, if the VM has a harder time of freeing pages, 1947 * with multiple processes reclaiming pages, the total 1948 * freeing target can get unreasonably large. 1949 */ 1950 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 1951 break; 1952 } 1953 sc->nr_reclaimed += nr_reclaimed; 1954 1955 /* 1956 * Even if we did not try to evict anon pages at all, we want to 1957 * rebalance the anon lru active/inactive ratio. 1958 */ 1959 if (inactive_anon_is_low(zone, sc)) 1960 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1961 1962 /* reclaim/compaction might need reclaim to continue */ 1963 if (should_continue_reclaim(zone, nr_reclaimed, 1964 sc->nr_scanned - nr_scanned, sc)) 1965 goto restart; 1966 1967 throttle_vm_writeout(sc->gfp_mask); 1968} 1969 1970/* 1971 * This is the direct reclaim path, for page-allocating processes. We only 1972 * try to reclaim pages from zones which will satisfy the caller's allocation 1973 * request. 1974 * 1975 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 1976 * Because: 1977 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1978 * allocation or 1979 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 1980 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 1981 * zone defense algorithm. 1982 * 1983 * If a zone is deemed to be full of pinned pages then just give it a light 1984 * scan then give up on it. 1985 */ 1986static unsigned long shrink_zones(int priority, struct zonelist *zonelist, 1987 struct scan_control *sc) 1988{ 1989 struct zoneref *z; 1990 struct zone *zone; 1991 unsigned long nr_soft_reclaimed; 1992 unsigned long nr_soft_scanned; 1993 unsigned long total_scanned = 0; 1994 1995 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1996 gfp_zone(sc->gfp_mask), sc->nodemask) { 1997 if (!populated_zone(zone)) 1998 continue; 1999 /* 2000 * Take care memory controller reclaiming has small influence 2001 * to global LRU. 2002 */ 2003 if (scanning_global_lru(sc)) { 2004 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2005 continue; 2006 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2007 continue; /* Let kswapd poll it */ 2008 } 2009 2010 nr_soft_scanned = 0; 2011 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2012 sc->order, sc->gfp_mask, 2013 &nr_soft_scanned); 2014 sc->nr_reclaimed += nr_soft_reclaimed; 2015 total_scanned += nr_soft_scanned; 2016 2017 shrink_zone(priority, zone, sc); 2018 } 2019 2020 return total_scanned; 2021} 2022 2023static bool zone_reclaimable(struct zone *zone) 2024{ 2025 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 2026} 2027 2028/* All zones in zonelist are unreclaimable? */ 2029static bool all_unreclaimable(struct zonelist *zonelist, 2030 struct scan_control *sc) 2031{ 2032 struct zoneref *z; 2033 struct zone *zone; 2034 2035 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2036 gfp_zone(sc->gfp_mask), sc->nodemask) { 2037 if (!populated_zone(zone)) 2038 continue; 2039 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2040 continue; 2041 if (!zone->all_unreclaimable) 2042 return false; 2043 } 2044 2045 return true; 2046} 2047 2048/* 2049 * This is the main entry point to direct page reclaim. 2050 * 2051 * If a full scan of the inactive list fails to free enough memory then we 2052 * are "out of memory" and something needs to be killed. 2053 * 2054 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2055 * high - the zone may be full of dirty or under-writeback pages, which this 2056 * caller can't do much about. We kick the writeback threads and take explicit 2057 * naps in the hope that some of these pages can be written. But if the 2058 * allocating task holds filesystem locks which prevent writeout this might not 2059 * work, and the allocation attempt will fail. 2060 * 2061 * returns: 0, if no pages reclaimed 2062 * else, the number of pages reclaimed 2063 */ 2064static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2065 struct scan_control *sc, 2066 struct shrink_control *shrink) 2067{ 2068 int priority; 2069 unsigned long total_scanned = 0; 2070 struct reclaim_state *reclaim_state = current->reclaim_state; 2071 struct zoneref *z; 2072 struct zone *zone; 2073 unsigned long writeback_threshold; 2074 2075 get_mems_allowed(); 2076 delayacct_freepages_start(); 2077 2078 if (scanning_global_lru(sc)) 2079 count_vm_event(ALLOCSTALL); 2080 2081 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2082 sc->nr_scanned = 0; 2083 if (!priority) 2084 disable_swap_token(sc->mem_cgroup); 2085 total_scanned += shrink_zones(priority, zonelist, sc); 2086 /* 2087 * Don't shrink slabs when reclaiming memory from 2088 * over limit cgroups 2089 */ 2090 if (scanning_global_lru(sc)) { 2091 unsigned long lru_pages = 0; 2092 for_each_zone_zonelist(zone, z, zonelist, 2093 gfp_zone(sc->gfp_mask)) { 2094 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2095 continue; 2096 2097 lru_pages += zone_reclaimable_pages(zone); 2098 } 2099 2100 shrink_slab(shrink, sc->nr_scanned, lru_pages); 2101 if (reclaim_state) { 2102 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2103 reclaim_state->reclaimed_slab = 0; 2104 } 2105 } 2106 total_scanned += sc->nr_scanned; 2107 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2108 goto out; 2109 2110 /* 2111 * Try to write back as many pages as we just scanned. This 2112 * tends to cause slow streaming writers to write data to the 2113 * disk smoothly, at the dirtying rate, which is nice. But 2114 * that's undesirable in laptop mode, where we *want* lumpy 2115 * writeout. So in laptop mode, write out the whole world. 2116 */ 2117 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2118 if (total_scanned > writeback_threshold) { 2119 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2120 sc->may_writepage = 1; 2121 } 2122 2123 /* Take a nap, wait for some writeback to complete */ 2124 if (!sc->hibernation_mode && sc->nr_scanned && 2125 priority < DEF_PRIORITY - 2) { 2126 struct zone *preferred_zone; 2127 2128 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2129 &cpuset_current_mems_allowed, 2130 &preferred_zone); 2131 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2132 } 2133 } 2134 2135out: 2136 delayacct_freepages_end(); 2137 put_mems_allowed(); 2138 2139 if (sc->nr_reclaimed) 2140 return sc->nr_reclaimed; 2141 2142 /* 2143 * As hibernation is going on, kswapd is freezed so that it can't mark 2144 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2145 * check. 2146 */ 2147 if (oom_killer_disabled) 2148 return 0; 2149 2150 /* top priority shrink_zones still had more to do? don't OOM, then */ 2151 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2152 return 1; 2153 2154 return 0; 2155} 2156 2157unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2158 gfp_t gfp_mask, nodemask_t *nodemask) 2159{ 2160 unsigned long nr_reclaimed; 2161 struct scan_control sc = { 2162 .gfp_mask = gfp_mask, 2163 .may_writepage = !laptop_mode, 2164 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2165 .may_unmap = 1, 2166 .may_swap = 1, 2167 .swappiness = vm_swappiness, 2168 .order = order, 2169 .mem_cgroup = NULL, 2170 .nodemask = nodemask, 2171 }; 2172 struct shrink_control shrink = { 2173 .gfp_mask = sc.gfp_mask, 2174 }; 2175 2176 trace_mm_vmscan_direct_reclaim_begin(order, 2177 sc.may_writepage, 2178 gfp_mask); 2179 2180 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2181 2182 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2183 2184 return nr_reclaimed; 2185} 2186 2187#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2188 2189unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2190 gfp_t gfp_mask, bool noswap, 2191 unsigned int swappiness, 2192 struct zone *zone, 2193 unsigned long *nr_scanned) 2194{ 2195 struct scan_control sc = { 2196 .nr_scanned = 0, 2197 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2198 .may_writepage = !laptop_mode, 2199 .may_unmap = 1, 2200 .may_swap = !noswap, 2201 .swappiness = swappiness, 2202 .order = 0, 2203 .mem_cgroup = mem, 2204 }; 2205 2206 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2207 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2208 2209 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2210 sc.may_writepage, 2211 sc.gfp_mask); 2212 2213 /* 2214 * NOTE: Although we can get the priority field, using it 2215 * here is not a good idea, since it limits the pages we can scan. 2216 * if we don't reclaim here, the shrink_zone from balance_pgdat 2217 * will pick up pages from other mem cgroup's as well. We hack 2218 * the priority and make it zero. 2219 */ 2220 shrink_zone(0, zone, &sc); 2221 2222 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2223 2224 *nr_scanned = sc.nr_scanned; 2225 return sc.nr_reclaimed; 2226} 2227 2228unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2229 gfp_t gfp_mask, 2230 bool noswap, 2231 unsigned int swappiness) 2232{ 2233 struct zonelist *zonelist; 2234 unsigned long nr_reclaimed; 2235 int nid; 2236 struct scan_control sc = { 2237 .may_writepage = !laptop_mode, 2238 .may_unmap = 1, 2239 .may_swap = !noswap, 2240 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2241 .swappiness = swappiness, 2242 .order = 0, 2243 .mem_cgroup = mem_cont, 2244 .nodemask = NULL, /* we don't care the placement */ 2245 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2246 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), 2247 }; 2248 struct shrink_control shrink = { 2249 .gfp_mask = sc.gfp_mask, 2250 }; 2251 2252 /* 2253 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't 2254 * take care of from where we get pages. So the node where we start the 2255 * scan does not need to be the current node. 2256 */ 2257 nid = mem_cgroup_select_victim_node(mem_cont); 2258 2259 zonelist = NODE_DATA(nid)->node_zonelists; 2260 2261 trace_mm_vmscan_memcg_reclaim_begin(0, 2262 sc.may_writepage, 2263 sc.gfp_mask); 2264 2265 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2266 2267 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2268 2269 return nr_reclaimed; 2270} 2271#endif 2272 2273/* 2274 * pgdat_balanced is used when checking if a node is balanced for high-order 2275 * allocations. Only zones that meet watermarks and are in a zone allowed 2276 * by the callers classzone_idx are added to balanced_pages. The total of 2277 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2278 * for the node to be considered balanced. Forcing all zones to be balanced 2279 * for high orders can cause excessive reclaim when there are imbalanced zones. 2280 * The choice of 25% is due to 2281 * o a 16M DMA zone that is balanced will not balance a zone on any 2282 * reasonable sized machine 2283 * o On all other machines, the top zone must be at least a reasonable 2284 * percentage of the middle zones. For example, on 32-bit x86, highmem 2285 * would need to be at least 256M for it to be balance a whole node. 2286 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2287 * to balance a node on its own. These seemed like reasonable ratios. 2288 */ 2289static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2290 int classzone_idx) 2291{ 2292 unsigned long present_pages = 0; 2293 int i; 2294 2295 for (i = 0; i <= classzone_idx; i++) 2296 present_pages += pgdat->node_zones[i].present_pages; 2297 2298 return balanced_pages > (present_pages >> 2); 2299} 2300 2301/* is kswapd sleeping prematurely? */ 2302static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2303 int classzone_idx) 2304{ 2305 int i; 2306 unsigned long balanced = 0; 2307 bool all_zones_ok = true; 2308 2309 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2310 if (remaining) 2311 return true; 2312 2313 /* Check the watermark levels */ 2314 for (i = 0; i < pgdat->nr_zones; i++) { 2315 struct zone *zone = pgdat->node_zones + i; 2316 2317 if (!populated_zone(zone)) 2318 continue; 2319 2320 /* 2321 * balance_pgdat() skips over all_unreclaimable after 2322 * DEF_PRIORITY. Effectively, it considers them balanced so 2323 * they must be considered balanced here as well if kswapd 2324 * is to sleep 2325 */ 2326 if (zone->all_unreclaimable) { 2327 balanced += zone->present_pages; 2328 continue; 2329 } 2330 2331 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2332 classzone_idx, 0)) 2333 all_zones_ok = false; 2334 else 2335 balanced += zone->present_pages; 2336 } 2337 2338 /* 2339 * For high-order requests, the balanced zones must contain at least 2340 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2341 * must be balanced 2342 */ 2343 if (order) 2344 return !pgdat_balanced(pgdat, balanced, classzone_idx); 2345 else 2346 return !all_zones_ok; 2347} 2348 2349/* 2350 * For kswapd, balance_pgdat() will work across all this node's zones until 2351 * they are all at high_wmark_pages(zone). 2352 * 2353 * Returns the final order kswapd was reclaiming at 2354 * 2355 * There is special handling here for zones which are full of pinned pages. 2356 * This can happen if the pages are all mlocked, or if they are all used by 2357 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2358 * What we do is to detect the case where all pages in the zone have been 2359 * scanned twice and there has been zero successful reclaim. Mark the zone as 2360 * dead and from now on, only perform a short scan. Basically we're polling 2361 * the zone for when the problem goes away. 2362 * 2363 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2364 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2365 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2366 * lower zones regardless of the number of free pages in the lower zones. This 2367 * interoperates with the page allocator fallback scheme to ensure that aging 2368 * of pages is balanced across the zones. 2369 */ 2370static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2371 int *classzone_idx) 2372{ 2373 int all_zones_ok; 2374 unsigned long balanced; 2375 int priority; 2376 int i; 2377 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2378 unsigned long total_scanned; 2379 struct reclaim_state *reclaim_state = current->reclaim_state; 2380 unsigned long nr_soft_reclaimed; 2381 unsigned long nr_soft_scanned; 2382 struct scan_control sc = { 2383 .gfp_mask = GFP_KERNEL, 2384 .may_unmap = 1, 2385 .may_swap = 1, 2386 /* 2387 * kswapd doesn't want to be bailed out while reclaim. because 2388 * we want to put equal scanning pressure on each zone. 2389 */ 2390 .nr_to_reclaim = ULONG_MAX, 2391 .swappiness = vm_swappiness, 2392 .order = order, 2393 .mem_cgroup = NULL, 2394 }; 2395 struct shrink_control shrink = { 2396 .gfp_mask = sc.gfp_mask, 2397 }; 2398loop_again: 2399 total_scanned = 0; 2400 sc.nr_reclaimed = 0; 2401 sc.may_writepage = !laptop_mode; 2402 count_vm_event(PAGEOUTRUN); 2403 2404 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2405 unsigned long lru_pages = 0; 2406 int has_under_min_watermark_zone = 0; 2407 2408 /* The swap token gets in the way of swapout... */ 2409 if (!priority) 2410 disable_swap_token(NULL); 2411 2412 all_zones_ok = 1; 2413 balanced = 0; 2414 2415 /* 2416 * Scan in the highmem->dma direction for the highest 2417 * zone which needs scanning 2418 */ 2419 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2420 struct zone *zone = pgdat->node_zones + i; 2421 2422 if (!populated_zone(zone)) 2423 continue; 2424 2425 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2426 continue; 2427 2428 /* 2429 * Do some background aging of the anon list, to give 2430 * pages a chance to be referenced before reclaiming. 2431 */ 2432 if (inactive_anon_is_low(zone, &sc)) 2433 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2434 &sc, priority, 0); 2435 2436 if (!zone_watermark_ok_safe(zone, order, 2437 high_wmark_pages(zone), 0, 0)) { 2438 end_zone = i; 2439 *classzone_idx = i; 2440 break; 2441 } 2442 } 2443 if (i < 0) 2444 goto out; 2445 2446 for (i = 0; i <= end_zone; i++) { 2447 struct zone *zone = pgdat->node_zones + i; 2448 2449 lru_pages += zone_reclaimable_pages(zone); 2450 } 2451 2452 /* 2453 * Now scan the zone in the dma->highmem direction, stopping 2454 * at the last zone which needs scanning. 2455 * 2456 * We do this because the page allocator works in the opposite 2457 * direction. This prevents the page allocator from allocating 2458 * pages behind kswapd's direction of progress, which would 2459 * cause too much scanning of the lower zones. 2460 */ 2461 for (i = 0; i <= end_zone; i++) { 2462 struct zone *zone = pgdat->node_zones + i; 2463 int nr_slab; 2464 unsigned long balance_gap; 2465 2466 if (!populated_zone(zone)) 2467 continue; 2468 2469 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2470 continue; 2471 2472 sc.nr_scanned = 0; 2473 2474 nr_soft_scanned = 0; 2475 /* 2476 * Call soft limit reclaim before calling shrink_zone. 2477 */ 2478 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, 2479 order, sc.gfp_mask, 2480 &nr_soft_scanned); 2481 sc.nr_reclaimed += nr_soft_reclaimed; 2482 total_scanned += nr_soft_scanned; 2483 2484 /* 2485 * We put equal pressure on every zone, unless 2486 * one zone has way too many pages free 2487 * already. The "too many pages" is defined 2488 * as the high wmark plus a "gap" where the 2489 * gap is either the low watermark or 1% 2490 * of the zone, whichever is smaller. 2491 */ 2492 balance_gap = min(low_wmark_pages(zone), 2493 (zone->present_pages + 2494 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2495 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2496 if (!zone_watermark_ok_safe(zone, order, 2497 high_wmark_pages(zone) + balance_gap, 2498 end_zone, 0)) 2499 shrink_zone(priority, zone, &sc); 2500 reclaim_state->reclaimed_slab = 0; 2501 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); 2502 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2503 total_scanned += sc.nr_scanned; 2504 2505 if (zone->all_unreclaimable) 2506 continue; 2507 if (nr_slab == 0 && 2508 !zone_reclaimable(zone)) 2509 zone->all_unreclaimable = 1; 2510 /* 2511 * If we've done a decent amount of scanning and 2512 * the reclaim ratio is low, start doing writepage 2513 * even in laptop mode 2514 */ 2515 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2516 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2517 sc.may_writepage = 1; 2518 2519 if (!zone_watermark_ok_safe(zone, order, 2520 high_wmark_pages(zone), end_zone, 0)) { 2521 all_zones_ok = 0; 2522 /* 2523 * We are still under min water mark. This 2524 * means that we have a GFP_ATOMIC allocation 2525 * failure risk. Hurry up! 2526 */ 2527 if (!zone_watermark_ok_safe(zone, order, 2528 min_wmark_pages(zone), end_zone, 0)) 2529 has_under_min_watermark_zone = 1; 2530 } else { 2531 /* 2532 * If a zone reaches its high watermark, 2533 * consider it to be no longer congested. It's 2534 * possible there are dirty pages backed by 2535 * congested BDIs but as pressure is relieved, 2536 * spectulatively avoid congestion waits 2537 */ 2538 zone_clear_flag(zone, ZONE_CONGESTED); 2539 if (i <= *classzone_idx) 2540 balanced += zone->present_pages; 2541 } 2542 2543 } 2544 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2545 break; /* kswapd: all done */ 2546 /* 2547 * OK, kswapd is getting into trouble. Take a nap, then take 2548 * another pass across the zones. 2549 */ 2550 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2551 if (has_under_min_watermark_zone) 2552 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2553 else 2554 congestion_wait(BLK_RW_ASYNC, HZ/10); 2555 } 2556 2557 /* 2558 * We do this so kswapd doesn't build up large priorities for 2559 * example when it is freeing in parallel with allocators. It 2560 * matches the direct reclaim path behaviour in terms of impact 2561 * on zone->*_priority. 2562 */ 2563 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2564 break; 2565 } 2566out: 2567 2568 /* 2569 * order-0: All zones must meet high watermark for a balanced node 2570 * high-order: Balanced zones must make up at least 25% of the node 2571 * for the node to be balanced 2572 */ 2573 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2574 cond_resched(); 2575 2576 try_to_freeze(); 2577 2578 /* 2579 * Fragmentation may mean that the system cannot be 2580 * rebalanced for high-order allocations in all zones. 2581 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2582 * it means the zones have been fully scanned and are still 2583 * not balanced. For high-order allocations, there is 2584 * little point trying all over again as kswapd may 2585 * infinite loop. 2586 * 2587 * Instead, recheck all watermarks at order-0 as they 2588 * are the most important. If watermarks are ok, kswapd will go 2589 * back to sleep. High-order users can still perform direct 2590 * reclaim if they wish. 2591 */ 2592 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2593 order = sc.order = 0; 2594 2595 goto loop_again; 2596 } 2597 2598 /* 2599 * If kswapd was reclaiming at a higher order, it has the option of 2600 * sleeping without all zones being balanced. Before it does, it must 2601 * ensure that the watermarks for order-0 on *all* zones are met and 2602 * that the congestion flags are cleared. The congestion flag must 2603 * be cleared as kswapd is the only mechanism that clears the flag 2604 * and it is potentially going to sleep here. 2605 */ 2606 if (order) { 2607 for (i = 0; i <= end_zone; i++) { 2608 struct zone *zone = pgdat->node_zones + i; 2609 2610 if (!populated_zone(zone)) 2611 continue; 2612 2613 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2614 continue; 2615 2616 /* Confirm the zone is balanced for order-0 */ 2617 if (!zone_watermark_ok(zone, 0, 2618 high_wmark_pages(zone), 0, 0)) { 2619 order = sc.order = 0; 2620 goto loop_again; 2621 } 2622 2623 /* If balanced, clear the congested flag */ 2624 zone_clear_flag(zone, ZONE_CONGESTED); 2625 } 2626 } 2627 2628 /* 2629 * Return the order we were reclaiming at so sleeping_prematurely() 2630 * makes a decision on the order we were last reclaiming at. However, 2631 * if another caller entered the allocator slow path while kswapd 2632 * was awake, order will remain at the higher level 2633 */ 2634 *classzone_idx = end_zone; 2635 return order; 2636} 2637 2638static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2639{ 2640 long remaining = 0; 2641 DEFINE_WAIT(wait); 2642 2643 if (freezing(current) || kthread_should_stop()) 2644 return; 2645 2646 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2647 2648 /* Try to sleep for a short interval */ 2649 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2650 remaining = schedule_timeout(HZ/10); 2651 finish_wait(&pgdat->kswapd_wait, &wait); 2652 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2653 } 2654 2655 /* 2656 * After a short sleep, check if it was a premature sleep. If not, then 2657 * go fully to sleep until explicitly woken up. 2658 */ 2659 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2660 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2661 2662 /* 2663 * vmstat counters are not perfectly accurate and the estimated 2664 * value for counters such as NR_FREE_PAGES can deviate from the 2665 * true value by nr_online_cpus * threshold. To avoid the zone 2666 * watermarks being breached while under pressure, we reduce the 2667 * per-cpu vmstat threshold while kswapd is awake and restore 2668 * them before going back to sleep. 2669 */ 2670 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2671 schedule(); 2672 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2673 } else { 2674 if (remaining) 2675 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2676 else 2677 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2678 } 2679 finish_wait(&pgdat->kswapd_wait, &wait); 2680} 2681 2682/* 2683 * The background pageout daemon, started as a kernel thread 2684 * from the init process. 2685 * 2686 * This basically trickles out pages so that we have _some_ 2687 * free memory available even if there is no other activity 2688 * that frees anything up. This is needed for things like routing 2689 * etc, where we otherwise might have all activity going on in 2690 * asynchronous contexts that cannot page things out. 2691 * 2692 * If there are applications that are active memory-allocators 2693 * (most normal use), this basically shouldn't matter. 2694 */ 2695static int kswapd(void *p) 2696{ 2697 unsigned long order; 2698 int classzone_idx; 2699 pg_data_t *pgdat = (pg_data_t*)p; 2700 struct task_struct *tsk = current; 2701 2702 struct reclaim_state reclaim_state = { 2703 .reclaimed_slab = 0, 2704 }; 2705 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2706 2707 lockdep_set_current_reclaim_state(GFP_KERNEL); 2708 2709 if (!cpumask_empty(cpumask)) 2710 set_cpus_allowed_ptr(tsk, cpumask); 2711 current->reclaim_state = &reclaim_state; 2712 2713 /* 2714 * Tell the memory management that we're a "memory allocator", 2715 * and that if we need more memory we should get access to it 2716 * regardless (see "__alloc_pages()"). "kswapd" should 2717 * never get caught in the normal page freeing logic. 2718 * 2719 * (Kswapd normally doesn't need memory anyway, but sometimes 2720 * you need a small amount of memory in order to be able to 2721 * page out something else, and this flag essentially protects 2722 * us from recursively trying to free more memory as we're 2723 * trying to free the first piece of memory in the first place). 2724 */ 2725 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2726 set_freezable(); 2727 2728 order = 0; 2729 classzone_idx = MAX_NR_ZONES - 1; 2730 for ( ; ; ) { 2731 unsigned long new_order; 2732 int new_classzone_idx; 2733 int ret; 2734 2735 new_order = pgdat->kswapd_max_order; 2736 new_classzone_idx = pgdat->classzone_idx; 2737 pgdat->kswapd_max_order = 0; 2738 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2739 if (order < new_order || classzone_idx > new_classzone_idx) { 2740 /* 2741 * Don't sleep if someone wants a larger 'order' 2742 * allocation or has tigher zone constraints 2743 */ 2744 order = new_order; 2745 classzone_idx = new_classzone_idx; 2746 } else { 2747 kswapd_try_to_sleep(pgdat, order, classzone_idx); 2748 order = pgdat->kswapd_max_order; 2749 classzone_idx = pgdat->classzone_idx; 2750 pgdat->kswapd_max_order = 0; 2751 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2752 } 2753 2754 ret = try_to_freeze(); 2755 if (kthread_should_stop()) 2756 break; 2757 2758 /* 2759 * We can speed up thawing tasks if we don't call balance_pgdat 2760 * after returning from the refrigerator 2761 */ 2762 if (!ret) { 2763 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2764 order = balance_pgdat(pgdat, order, &classzone_idx); 2765 } 2766 } 2767 return 0; 2768} 2769 2770/* 2771 * A zone is low on free memory, so wake its kswapd task to service it. 2772 */ 2773void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2774{ 2775 pg_data_t *pgdat; 2776 2777 if (!populated_zone(zone)) 2778 return; 2779 2780 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2781 return; 2782 pgdat = zone->zone_pgdat; 2783 if (pgdat->kswapd_max_order < order) { 2784 pgdat->kswapd_max_order = order; 2785 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2786 } 2787 if (!waitqueue_active(&pgdat->kswapd_wait)) 2788 return; 2789 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2790 return; 2791 2792 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2793 wake_up_interruptible(&pgdat->kswapd_wait); 2794} 2795 2796/* 2797 * The reclaimable count would be mostly accurate. 2798 * The less reclaimable pages may be 2799 * - mlocked pages, which will be moved to unevictable list when encountered 2800 * - mapped pages, which may require several travels to be reclaimed 2801 * - dirty pages, which is not "instantly" reclaimable 2802 */ 2803unsigned long global_reclaimable_pages(void) 2804{ 2805 int nr; 2806 2807 nr = global_page_state(NR_ACTIVE_FILE) + 2808 global_page_state(NR_INACTIVE_FILE); 2809 2810 if (nr_swap_pages > 0) 2811 nr += global_page_state(NR_ACTIVE_ANON) + 2812 global_page_state(NR_INACTIVE_ANON); 2813 2814 return nr; 2815} 2816 2817unsigned long zone_reclaimable_pages(struct zone *zone) 2818{ 2819 int nr; 2820 2821 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2822 zone_page_state(zone, NR_INACTIVE_FILE); 2823 2824 if (nr_swap_pages > 0) 2825 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2826 zone_page_state(zone, NR_INACTIVE_ANON); 2827 2828 return nr; 2829} 2830 2831#ifdef CONFIG_HIBERNATION 2832/* 2833 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2834 * freed pages. 2835 * 2836 * Rather than trying to age LRUs the aim is to preserve the overall 2837 * LRU order by reclaiming preferentially 2838 * inactive > active > active referenced > active mapped 2839 */ 2840unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2841{ 2842 struct reclaim_state reclaim_state; 2843 struct scan_control sc = { 2844 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2845 .may_swap = 1, 2846 .may_unmap = 1, 2847 .may_writepage = 1, 2848 .nr_to_reclaim = nr_to_reclaim, 2849 .hibernation_mode = 1, 2850 .swappiness = vm_swappiness, 2851 .order = 0, 2852 }; 2853 struct shrink_control shrink = { 2854 .gfp_mask = sc.gfp_mask, 2855 }; 2856 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2857 struct task_struct *p = current; 2858 unsigned long nr_reclaimed; 2859 2860 p->flags |= PF_MEMALLOC; 2861 lockdep_set_current_reclaim_state(sc.gfp_mask); 2862 reclaim_state.reclaimed_slab = 0; 2863 p->reclaim_state = &reclaim_state; 2864 2865 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); 2866 2867 p->reclaim_state = NULL; 2868 lockdep_clear_current_reclaim_state(); 2869 p->flags &= ~PF_MEMALLOC; 2870 2871 return nr_reclaimed; 2872} 2873#endif /* CONFIG_HIBERNATION */ 2874 2875/* It's optimal to keep kswapds on the same CPUs as their memory, but 2876 not required for correctness. So if the last cpu in a node goes 2877 away, we get changed to run anywhere: as the first one comes back, 2878 restore their cpu bindings. */ 2879static int __devinit cpu_callback(struct notifier_block *nfb, 2880 unsigned long action, void *hcpu) 2881{ 2882 int nid; 2883 2884 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2885 for_each_node_state(nid, N_HIGH_MEMORY) { 2886 pg_data_t *pgdat = NODE_DATA(nid); 2887 const struct cpumask *mask; 2888 2889 mask = cpumask_of_node(pgdat->node_id); 2890 2891 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2892 /* One of our CPUs online: restore mask */ 2893 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2894 } 2895 } 2896 return NOTIFY_OK; 2897} 2898 2899/* 2900 * This kswapd start function will be called by init and node-hot-add. 2901 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2902 */ 2903int kswapd_run(int nid) 2904{ 2905 pg_data_t *pgdat = NODE_DATA(nid); 2906 int ret = 0; 2907 2908 if (pgdat->kswapd) 2909 return 0; 2910 2911 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2912 if (IS_ERR(pgdat->kswapd)) { 2913 /* failure at boot is fatal */ 2914 BUG_ON(system_state == SYSTEM_BOOTING); 2915 printk("Failed to start kswapd on node %d\n",nid); 2916 ret = -1; 2917 } 2918 return ret; 2919} 2920 2921/* 2922 * Called by memory hotplug when all memory in a node is offlined. 2923 */ 2924void kswapd_stop(int nid) 2925{ 2926 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2927 2928 if (kswapd) 2929 kthread_stop(kswapd); 2930} 2931 2932static int __init kswapd_init(void) 2933{ 2934 int nid; 2935 2936 swap_setup(); 2937 for_each_node_state(nid, N_HIGH_MEMORY) 2938 kswapd_run(nid); 2939 hotcpu_notifier(cpu_callback, 0); 2940 return 0; 2941} 2942 2943module_init(kswapd_init) 2944 2945#ifdef CONFIG_NUMA 2946/* 2947 * Zone reclaim mode 2948 * 2949 * If non-zero call zone_reclaim when the number of free pages falls below 2950 * the watermarks. 2951 */ 2952int zone_reclaim_mode __read_mostly; 2953 2954#define RECLAIM_OFF 0 2955#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2956#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2957#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2958 2959/* 2960 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2961 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2962 * a zone. 2963 */ 2964#define ZONE_RECLAIM_PRIORITY 4 2965 2966/* 2967 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2968 * occur. 2969 */ 2970int sysctl_min_unmapped_ratio = 1; 2971 2972/* 2973 * If the number of slab pages in a zone grows beyond this percentage then 2974 * slab reclaim needs to occur. 2975 */ 2976int sysctl_min_slab_ratio = 5; 2977 2978static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 2979{ 2980 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 2981 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 2982 zone_page_state(zone, NR_ACTIVE_FILE); 2983 2984 /* 2985 * It's possible for there to be more file mapped pages than 2986 * accounted for by the pages on the file LRU lists because 2987 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 2988 */ 2989 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 2990} 2991 2992/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 2993static long zone_pagecache_reclaimable(struct zone *zone) 2994{ 2995 long nr_pagecache_reclaimable; 2996 long delta = 0; 2997 2998 /* 2999 * If RECLAIM_SWAP is set, then all file pages are considered 3000 * potentially reclaimable. Otherwise, we have to worry about 3001 * pages like swapcache and zone_unmapped_file_pages() provides 3002 * a better estimate 3003 */ 3004 if (zone_reclaim_mode & RECLAIM_SWAP) 3005 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 3006 else 3007 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 3008 3009 /* If we can't clean pages, remove dirty pages from consideration */ 3010 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 3011 delta += zone_page_state(zone, NR_FILE_DIRTY); 3012 3013 /* Watch for any possible underflows due to delta */ 3014 if (unlikely(delta > nr_pagecache_reclaimable)) 3015 delta = nr_pagecache_reclaimable; 3016 3017 return nr_pagecache_reclaimable - delta; 3018} 3019 3020/* 3021 * Try to free up some pages from this zone through reclaim. 3022 */ 3023static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3024{ 3025 /* Minimum pages needed in order to stay on node */ 3026 const unsigned long nr_pages = 1 << order; 3027 struct task_struct *p = current; 3028 struct reclaim_state reclaim_state; 3029 int priority; 3030 struct scan_control sc = { 3031 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 3032 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 3033 .may_swap = 1, 3034 .nr_to_reclaim = max_t(unsigned long, nr_pages, 3035 SWAP_CLUSTER_MAX), 3036 .gfp_mask = gfp_mask, 3037 .swappiness = vm_swappiness, 3038 .order = order, 3039 }; 3040 struct shrink_control shrink = { 3041 .gfp_mask = sc.gfp_mask, 3042 }; 3043 unsigned long nr_slab_pages0, nr_slab_pages1; 3044 3045 cond_resched(); 3046 /* 3047 * We need to be able to allocate from the reserves for RECLAIM_SWAP 3048 * and we also need to be able to write out pages for RECLAIM_WRITE 3049 * and RECLAIM_SWAP. 3050 */ 3051 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 3052 lockdep_set_current_reclaim_state(gfp_mask); 3053 reclaim_state.reclaimed_slab = 0; 3054 p->reclaim_state = &reclaim_state; 3055 3056 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 3057 /* 3058 * Free memory by calling shrink zone with increasing 3059 * priorities until we have enough memory freed. 3060 */ 3061 priority = ZONE_RECLAIM_PRIORITY; 3062 do { 3063 shrink_zone(priority, zone, &sc); 3064 priority--; 3065 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 3066 } 3067 3068 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3069 if (nr_slab_pages0 > zone->min_slab_pages) { 3070 /* 3071 * shrink_slab() does not currently allow us to determine how 3072 * many pages were freed in this zone. So we take the current 3073 * number of slab pages and shake the slab until it is reduced 3074 * by the same nr_pages that we used for reclaiming unmapped 3075 * pages. 3076 * 3077 * Note that shrink_slab will free memory on all zones and may 3078 * take a long time. 3079 */ 3080 for (;;) { 3081 unsigned long lru_pages = zone_reclaimable_pages(zone); 3082 3083 /* No reclaimable slab or very low memory pressure */ 3084 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) 3085 break; 3086 3087 /* Freed enough memory */ 3088 nr_slab_pages1 = zone_page_state(zone, 3089 NR_SLAB_RECLAIMABLE); 3090 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3091 break; 3092 } 3093 3094 /* 3095 * Update nr_reclaimed by the number of slab pages we 3096 * reclaimed from this zone. 3097 */ 3098 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3099 if (nr_slab_pages1 < nr_slab_pages0) 3100 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3101 } 3102 3103 p->reclaim_state = NULL; 3104 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3105 lockdep_clear_current_reclaim_state(); 3106 return sc.nr_reclaimed >= nr_pages; 3107} 3108 3109int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3110{ 3111 int node_id; 3112 int ret; 3113 3114 /* 3115 * Zone reclaim reclaims unmapped file backed pages and 3116 * slab pages if we are over the defined limits. 3117 * 3118 * A small portion of unmapped file backed pages is needed for 3119 * file I/O otherwise pages read by file I/O will be immediately 3120 * thrown out if the zone is overallocated. So we do not reclaim 3121 * if less than a specified percentage of the zone is used by 3122 * unmapped file backed pages. 3123 */ 3124 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3125 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3126 return ZONE_RECLAIM_FULL; 3127 3128 if (zone->all_unreclaimable) 3129 return ZONE_RECLAIM_FULL; 3130 3131 /* 3132 * Do not scan if the allocation should not be delayed. 3133 */ 3134 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3135 return ZONE_RECLAIM_NOSCAN; 3136 3137 /* 3138 * Only run zone reclaim on the local zone or on zones that do not 3139 * have associated processors. This will favor the local processor 3140 * over remote processors and spread off node memory allocations 3141 * as wide as possible. 3142 */ 3143 node_id = zone_to_nid(zone); 3144 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3145 return ZONE_RECLAIM_NOSCAN; 3146 3147 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3148 return ZONE_RECLAIM_NOSCAN; 3149 3150 ret = __zone_reclaim(zone, gfp_mask, order); 3151 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3152 3153 if (!ret) 3154 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3155 3156 return ret; 3157} 3158#endif 3159 3160/* 3161 * page_evictable - test whether a page is evictable 3162 * @page: the page to test 3163 * @vma: the VMA in which the page is or will be mapped, may be NULL 3164 * 3165 * Test whether page is evictable--i.e., should be placed on active/inactive 3166 * lists vs unevictable list. The vma argument is !NULL when called from the 3167 * fault path to determine how to instantate a new page. 3168 * 3169 * Reasons page might not be evictable: 3170 * (1) page's mapping marked unevictable 3171 * (2) page is part of an mlocked VMA 3172 * 3173 */ 3174int page_evictable(struct page *page, struct vm_area_struct *vma) 3175{ 3176 3177 if (mapping_unevictable(page_mapping(page))) 3178 return 0; 3179 3180 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3181 return 0; 3182 3183 return 1; 3184} 3185 3186/** 3187 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3188 * @page: page to check evictability and move to appropriate lru list 3189 * @zone: zone page is in 3190 * 3191 * Checks a page for evictability and moves the page to the appropriate 3192 * zone lru list. 3193 * 3194 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3195 * have PageUnevictable set. 3196 */ 3197static void check_move_unevictable_page(struct page *page, struct zone *zone) 3198{ 3199 VM_BUG_ON(PageActive(page)); 3200 3201retry: 3202 ClearPageUnevictable(page); 3203 if (page_evictable(page, NULL)) { 3204 enum lru_list l = page_lru_base_type(page); 3205 3206 __dec_zone_state(zone, NR_UNEVICTABLE); 3207 list_move(&page->lru, &zone->lru[l].list); 3208 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3209 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3210 __count_vm_event(UNEVICTABLE_PGRESCUED); 3211 } else { 3212 /* 3213 * rotate unevictable list 3214 */ 3215 SetPageUnevictable(page); 3216 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3217 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3218 if (page_evictable(page, NULL)) 3219 goto retry; 3220 } 3221} 3222 3223/** 3224 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3225 * @mapping: struct address_space to scan for evictable pages 3226 * 3227 * Scan all pages in mapping. Check unevictable pages for 3228 * evictability and move them to the appropriate zone lru list. 3229 */ 3230void scan_mapping_unevictable_pages(struct address_space *mapping) 3231{ 3232 pgoff_t next = 0; 3233 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3234 PAGE_CACHE_SHIFT; 3235 struct zone *zone; 3236 struct pagevec pvec; 3237 3238 if (mapping->nrpages == 0) 3239 return; 3240 3241 pagevec_init(&pvec, 0); 3242 while (next < end && 3243 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3244 int i; 3245 int pg_scanned = 0; 3246 3247 zone = NULL; 3248 3249 for (i = 0; i < pagevec_count(&pvec); i++) { 3250 struct page *page = pvec.pages[i]; 3251 pgoff_t page_index = page->index; 3252 struct zone *pagezone = page_zone(page); 3253 3254 pg_scanned++; 3255 if (page_index > next) 3256 next = page_index; 3257 next++; 3258 3259 if (pagezone != zone) { 3260 if (zone) 3261 spin_unlock_irq(&zone->lru_lock); 3262 zone = pagezone; 3263 spin_lock_irq(&zone->lru_lock); 3264 } 3265 3266 if (PageLRU(page) && PageUnevictable(page)) 3267 check_move_unevictable_page(page, zone); 3268 } 3269 if (zone) 3270 spin_unlock_irq(&zone->lru_lock); 3271 pagevec_release(&pvec); 3272 3273 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3274 } 3275 3276} 3277 3278/** 3279 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3280 * @zone - zone of which to scan the unevictable list 3281 * 3282 * Scan @zone's unevictable LRU lists to check for pages that have become 3283 * evictable. Move those that have to @zone's inactive list where they 3284 * become candidates for reclaim, unless shrink_inactive_zone() decides 3285 * to reactivate them. Pages that are still unevictable are rotated 3286 * back onto @zone's unevictable list. 3287 */ 3288#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3289static void scan_zone_unevictable_pages(struct zone *zone) 3290{ 3291 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3292 unsigned long scan; 3293 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3294 3295 while (nr_to_scan > 0) { 3296 unsigned long batch_size = min(nr_to_scan, 3297 SCAN_UNEVICTABLE_BATCH_SIZE); 3298 3299 spin_lock_irq(&zone->lru_lock); 3300 for (scan = 0; scan < batch_size; scan++) { 3301 struct page *page = lru_to_page(l_unevictable); 3302 3303 if (!trylock_page(page)) 3304 continue; 3305 3306 prefetchw_prev_lru_page(page, l_unevictable, flags); 3307 3308 if (likely(PageLRU(page) && PageUnevictable(page))) 3309 check_move_unevictable_page(page, zone); 3310 3311 unlock_page(page); 3312 } 3313 spin_unlock_irq(&zone->lru_lock); 3314 3315 nr_to_scan -= batch_size; 3316 } 3317} 3318 3319 3320/** 3321 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3322 * 3323 * A really big hammer: scan all zones' unevictable LRU lists to check for 3324 * pages that have become evictable. Move those back to the zones' 3325 * inactive list where they become candidates for reclaim. 3326 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3327 * and we add swap to the system. As such, it runs in the context of a task 3328 * that has possibly/probably made some previously unevictable pages 3329 * evictable. 3330 */ 3331static void scan_all_zones_unevictable_pages(void) 3332{ 3333 struct zone *zone; 3334 3335 for_each_zone(zone) { 3336 scan_zone_unevictable_pages(zone); 3337 } 3338} 3339 3340/* 3341 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3342 * all nodes' unevictable lists for evictable pages 3343 */ 3344unsigned long scan_unevictable_pages; 3345 3346int scan_unevictable_handler(struct ctl_table *table, int write, 3347 void __user *buffer, 3348 size_t *length, loff_t *ppos) 3349{ 3350 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3351 3352 if (write && *(unsigned long *)table->data) 3353 scan_all_zones_unevictable_pages(); 3354 3355 scan_unevictable_pages = 0; 3356 return 0; 3357} 3358 3359#ifdef CONFIG_NUMA 3360/* 3361 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3362 * a specified node's per zone unevictable lists for evictable pages. 3363 */ 3364 3365static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3366 struct sysdev_attribute *attr, 3367 char *buf) 3368{ 3369 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3370} 3371 3372static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3373 struct sysdev_attribute *attr, 3374 const char *buf, size_t count) 3375{ 3376 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3377 struct zone *zone; 3378 unsigned long res; 3379 unsigned long req = strict_strtoul(buf, 10, &res); 3380 3381 if (!req) 3382 return 1; /* zero is no-op */ 3383 3384 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3385 if (!populated_zone(zone)) 3386 continue; 3387 scan_zone_unevictable_pages(zone); 3388 } 3389 return 1; 3390} 3391 3392 3393static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3394 read_scan_unevictable_node, 3395 write_scan_unevictable_node); 3396 3397int scan_unevictable_register_node(struct node *node) 3398{ 3399 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3400} 3401 3402void scan_unevictable_unregister_node(struct node *node) 3403{ 3404 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3405} 3406#endif 3407