vmscan.c revision 268bb0ce3e87872cb9290c322b0d35bce230d88f
1/* 2 * linux/mm/vmscan.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * 6 * Swap reorganised 29.12.95, Stephen Tweedie. 7 * kswapd added: 7.1.96 sct 8 * Removed kswapd_ctl limits, and swap out as many pages as needed 9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel. 10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). 11 * Multiqueue VM started 5.8.00, Rik van Riel. 12 */ 13 14#include <linux/mm.h> 15#include <linux/module.h> 16#include <linux/gfp.h> 17#include <linux/kernel_stat.h> 18#include <linux/swap.h> 19#include <linux/pagemap.h> 20#include <linux/init.h> 21#include <linux/highmem.h> 22#include <linux/vmstat.h> 23#include <linux/file.h> 24#include <linux/writeback.h> 25#include <linux/blkdev.h> 26#include <linux/buffer_head.h> /* for try_to_release_page(), 27 buffer_heads_over_limit */ 28#include <linux/mm_inline.h> 29#include <linux/pagevec.h> 30#include <linux/backing-dev.h> 31#include <linux/rmap.h> 32#include <linux/topology.h> 33#include <linux/cpu.h> 34#include <linux/cpuset.h> 35#include <linux/compaction.h> 36#include <linux/notifier.h> 37#include <linux/rwsem.h> 38#include <linux/delay.h> 39#include <linux/kthread.h> 40#include <linux/freezer.h> 41#include <linux/memcontrol.h> 42#include <linux/delayacct.h> 43#include <linux/sysctl.h> 44#include <linux/oom.h> 45#include <linux/prefetch.h> 46 47#include <asm/tlbflush.h> 48#include <asm/div64.h> 49 50#include <linux/swapops.h> 51 52#include "internal.h" 53 54#define CREATE_TRACE_POINTS 55#include <trace/events/vmscan.h> 56 57/* 58 * reclaim_mode determines how the inactive list is shrunk 59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages 60 * RECLAIM_MODE_ASYNC: Do not block 61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback 62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference 63 * page from the LRU and reclaim all pages within a 64 * naturally aligned range 65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of 66 * order-0 pages and then compact the zone 67 */ 68typedef unsigned __bitwise__ reclaim_mode_t; 69#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) 70#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) 71#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) 72#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) 73#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) 74 75struct scan_control { 76 /* Incremented by the number of inactive pages that were scanned */ 77 unsigned long nr_scanned; 78 79 /* Number of pages freed so far during a call to shrink_zones() */ 80 unsigned long nr_reclaimed; 81 82 /* How many pages shrink_list() should reclaim */ 83 unsigned long nr_to_reclaim; 84 85 unsigned long hibernation_mode; 86 87 /* This context's GFP mask */ 88 gfp_t gfp_mask; 89 90 int may_writepage; 91 92 /* Can mapped pages be reclaimed? */ 93 int may_unmap; 94 95 /* Can pages be swapped as part of reclaim? */ 96 int may_swap; 97 98 int swappiness; 99 100 int order; 101 102 /* 103 * Intend to reclaim enough continuous memory rather than reclaim 104 * enough amount of memory. i.e, mode for high order allocation. 105 */ 106 reclaim_mode_t reclaim_mode; 107 108 /* Which cgroup do we reclaim from */ 109 struct mem_cgroup *mem_cgroup; 110 111 /* 112 * Nodemask of nodes allowed by the caller. If NULL, all nodes 113 * are scanned. 114 */ 115 nodemask_t *nodemask; 116}; 117 118#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) 119 120#ifdef ARCH_HAS_PREFETCH 121#define prefetch_prev_lru_page(_page, _base, _field) \ 122 do { \ 123 if ((_page)->lru.prev != _base) { \ 124 struct page *prev; \ 125 \ 126 prev = lru_to_page(&(_page->lru)); \ 127 prefetch(&prev->_field); \ 128 } \ 129 } while (0) 130#else 131#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) 132#endif 133 134#ifdef ARCH_HAS_PREFETCHW 135#define prefetchw_prev_lru_page(_page, _base, _field) \ 136 do { \ 137 if ((_page)->lru.prev != _base) { \ 138 struct page *prev; \ 139 \ 140 prev = lru_to_page(&(_page->lru)); \ 141 prefetchw(&prev->_field); \ 142 } \ 143 } while (0) 144#else 145#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) 146#endif 147 148/* 149 * From 0 .. 100. Higher means more swappy. 150 */ 151int vm_swappiness = 60; 152long vm_total_pages; /* The total number of pages which the VM controls */ 153 154static LIST_HEAD(shrinker_list); 155static DECLARE_RWSEM(shrinker_rwsem); 156 157#ifdef CONFIG_CGROUP_MEM_RES_CTLR 158#define scanning_global_lru(sc) (!(sc)->mem_cgroup) 159#else 160#define scanning_global_lru(sc) (1) 161#endif 162 163static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, 164 struct scan_control *sc) 165{ 166 if (!scanning_global_lru(sc)) 167 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); 168 169 return &zone->reclaim_stat; 170} 171 172static unsigned long zone_nr_lru_pages(struct zone *zone, 173 struct scan_control *sc, enum lru_list lru) 174{ 175 if (!scanning_global_lru(sc)) 176 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); 177 178 return zone_page_state(zone, NR_LRU_BASE + lru); 179} 180 181 182/* 183 * Add a shrinker callback to be called from the vm 184 */ 185void register_shrinker(struct shrinker *shrinker) 186{ 187 shrinker->nr = 0; 188 down_write(&shrinker_rwsem); 189 list_add_tail(&shrinker->list, &shrinker_list); 190 up_write(&shrinker_rwsem); 191} 192EXPORT_SYMBOL(register_shrinker); 193 194/* 195 * Remove one 196 */ 197void unregister_shrinker(struct shrinker *shrinker) 198{ 199 down_write(&shrinker_rwsem); 200 list_del(&shrinker->list); 201 up_write(&shrinker_rwsem); 202} 203EXPORT_SYMBOL(unregister_shrinker); 204 205#define SHRINK_BATCH 128 206/* 207 * Call the shrink functions to age shrinkable caches 208 * 209 * Here we assume it costs one seek to replace a lru page and that it also 210 * takes a seek to recreate a cache object. With this in mind we age equal 211 * percentages of the lru and ageable caches. This should balance the seeks 212 * generated by these structures. 213 * 214 * If the vm encountered mapped pages on the LRU it increase the pressure on 215 * slab to avoid swapping. 216 * 217 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. 218 * 219 * `lru_pages' represents the number of on-LRU pages in all the zones which 220 * are eligible for the caller's allocation attempt. It is used for balancing 221 * slab reclaim versus page reclaim. 222 * 223 * Returns the number of slab objects which we shrunk. 224 */ 225unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask, 226 unsigned long lru_pages) 227{ 228 struct shrinker *shrinker; 229 unsigned long ret = 0; 230 231 if (scanned == 0) 232 scanned = SWAP_CLUSTER_MAX; 233 234 if (!down_read_trylock(&shrinker_rwsem)) 235 return 1; /* Assume we'll be able to shrink next time */ 236 237 list_for_each_entry(shrinker, &shrinker_list, list) { 238 unsigned long long delta; 239 unsigned long total_scan; 240 unsigned long max_pass; 241 242 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask); 243 delta = (4 * scanned) / shrinker->seeks; 244 delta *= max_pass; 245 do_div(delta, lru_pages + 1); 246 shrinker->nr += delta; 247 if (shrinker->nr < 0) { 248 printk(KERN_ERR "shrink_slab: %pF negative objects to " 249 "delete nr=%ld\n", 250 shrinker->shrink, shrinker->nr); 251 shrinker->nr = max_pass; 252 } 253 254 /* 255 * Avoid risking looping forever due to too large nr value: 256 * never try to free more than twice the estimate number of 257 * freeable entries. 258 */ 259 if (shrinker->nr > max_pass * 2) 260 shrinker->nr = max_pass * 2; 261 262 total_scan = shrinker->nr; 263 shrinker->nr = 0; 264 265 while (total_scan >= SHRINK_BATCH) { 266 long this_scan = SHRINK_BATCH; 267 int shrink_ret; 268 int nr_before; 269 270 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask); 271 shrink_ret = (*shrinker->shrink)(shrinker, this_scan, 272 gfp_mask); 273 if (shrink_ret == -1) 274 break; 275 if (shrink_ret < nr_before) 276 ret += nr_before - shrink_ret; 277 count_vm_events(SLABS_SCANNED, this_scan); 278 total_scan -= this_scan; 279 280 cond_resched(); 281 } 282 283 shrinker->nr += total_scan; 284 } 285 up_read(&shrinker_rwsem); 286 return ret; 287} 288 289static void set_reclaim_mode(int priority, struct scan_control *sc, 290 bool sync) 291{ 292 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; 293 294 /* 295 * Initially assume we are entering either lumpy reclaim or 296 * reclaim/compaction.Depending on the order, we will either set the 297 * sync mode or just reclaim order-0 pages later. 298 */ 299 if (COMPACTION_BUILD) 300 sc->reclaim_mode = RECLAIM_MODE_COMPACTION; 301 else 302 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; 303 304 /* 305 * Avoid using lumpy reclaim or reclaim/compaction if possible by 306 * restricting when its set to either costly allocations or when 307 * under memory pressure 308 */ 309 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 310 sc->reclaim_mode |= syncmode; 311 else if (sc->order && priority < DEF_PRIORITY - 2) 312 sc->reclaim_mode |= syncmode; 313 else 314 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 315} 316 317static void reset_reclaim_mode(struct scan_control *sc) 318{ 319 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; 320} 321 322static inline int is_page_cache_freeable(struct page *page) 323{ 324 /* 325 * A freeable page cache page is referenced only by the caller 326 * that isolated the page, the page cache radix tree and 327 * optional buffer heads at page->private. 328 */ 329 return page_count(page) - page_has_private(page) == 2; 330} 331 332static int may_write_to_queue(struct backing_dev_info *bdi, 333 struct scan_control *sc) 334{ 335 if (current->flags & PF_SWAPWRITE) 336 return 1; 337 if (!bdi_write_congested(bdi)) 338 return 1; 339 if (bdi == current->backing_dev_info) 340 return 1; 341 342 /* lumpy reclaim for hugepage often need a lot of write */ 343 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 344 return 1; 345 return 0; 346} 347 348/* 349 * We detected a synchronous write error writing a page out. Probably 350 * -ENOSPC. We need to propagate that into the address_space for a subsequent 351 * fsync(), msync() or close(). 352 * 353 * The tricky part is that after writepage we cannot touch the mapping: nothing 354 * prevents it from being freed up. But we have a ref on the page and once 355 * that page is locked, the mapping is pinned. 356 * 357 * We're allowed to run sleeping lock_page() here because we know the caller has 358 * __GFP_FS. 359 */ 360static void handle_write_error(struct address_space *mapping, 361 struct page *page, int error) 362{ 363 lock_page(page); 364 if (page_mapping(page) == mapping) 365 mapping_set_error(mapping, error); 366 unlock_page(page); 367} 368 369/* possible outcome of pageout() */ 370typedef enum { 371 /* failed to write page out, page is locked */ 372 PAGE_KEEP, 373 /* move page to the active list, page is locked */ 374 PAGE_ACTIVATE, 375 /* page has been sent to the disk successfully, page is unlocked */ 376 PAGE_SUCCESS, 377 /* page is clean and locked */ 378 PAGE_CLEAN, 379} pageout_t; 380 381/* 382 * pageout is called by shrink_page_list() for each dirty page. 383 * Calls ->writepage(). 384 */ 385static pageout_t pageout(struct page *page, struct address_space *mapping, 386 struct scan_control *sc) 387{ 388 /* 389 * If the page is dirty, only perform writeback if that write 390 * will be non-blocking. To prevent this allocation from being 391 * stalled by pagecache activity. But note that there may be 392 * stalls if we need to run get_block(). We could test 393 * PagePrivate for that. 394 * 395 * If this process is currently in __generic_file_aio_write() against 396 * this page's queue, we can perform writeback even if that 397 * will block. 398 * 399 * If the page is swapcache, write it back even if that would 400 * block, for some throttling. This happens by accident, because 401 * swap_backing_dev_info is bust: it doesn't reflect the 402 * congestion state of the swapdevs. Easy to fix, if needed. 403 */ 404 if (!is_page_cache_freeable(page)) 405 return PAGE_KEEP; 406 if (!mapping) { 407 /* 408 * Some data journaling orphaned pages can have 409 * page->mapping == NULL while being dirty with clean buffers. 410 */ 411 if (page_has_private(page)) { 412 if (try_to_free_buffers(page)) { 413 ClearPageDirty(page); 414 printk("%s: orphaned page\n", __func__); 415 return PAGE_CLEAN; 416 } 417 } 418 return PAGE_KEEP; 419 } 420 if (mapping->a_ops->writepage == NULL) 421 return PAGE_ACTIVATE; 422 if (!may_write_to_queue(mapping->backing_dev_info, sc)) 423 return PAGE_KEEP; 424 425 if (clear_page_dirty_for_io(page)) { 426 int res; 427 struct writeback_control wbc = { 428 .sync_mode = WB_SYNC_NONE, 429 .nr_to_write = SWAP_CLUSTER_MAX, 430 .range_start = 0, 431 .range_end = LLONG_MAX, 432 .for_reclaim = 1, 433 }; 434 435 SetPageReclaim(page); 436 res = mapping->a_ops->writepage(page, &wbc); 437 if (res < 0) 438 handle_write_error(mapping, page, res); 439 if (res == AOP_WRITEPAGE_ACTIVATE) { 440 ClearPageReclaim(page); 441 return PAGE_ACTIVATE; 442 } 443 444 /* 445 * Wait on writeback if requested to. This happens when 446 * direct reclaiming a large contiguous area and the 447 * first attempt to free a range of pages fails. 448 */ 449 if (PageWriteback(page) && 450 (sc->reclaim_mode & RECLAIM_MODE_SYNC)) 451 wait_on_page_writeback(page); 452 453 if (!PageWriteback(page)) { 454 /* synchronous write or broken a_ops? */ 455 ClearPageReclaim(page); 456 } 457 trace_mm_vmscan_writepage(page, 458 trace_reclaim_flags(page, sc->reclaim_mode)); 459 inc_zone_page_state(page, NR_VMSCAN_WRITE); 460 return PAGE_SUCCESS; 461 } 462 463 return PAGE_CLEAN; 464} 465 466/* 467 * Same as remove_mapping, but if the page is removed from the mapping, it 468 * gets returned with a refcount of 0. 469 */ 470static int __remove_mapping(struct address_space *mapping, struct page *page) 471{ 472 BUG_ON(!PageLocked(page)); 473 BUG_ON(mapping != page_mapping(page)); 474 475 spin_lock_irq(&mapping->tree_lock); 476 /* 477 * The non racy check for a busy page. 478 * 479 * Must be careful with the order of the tests. When someone has 480 * a ref to the page, it may be possible that they dirty it then 481 * drop the reference. So if PageDirty is tested before page_count 482 * here, then the following race may occur: 483 * 484 * get_user_pages(&page); 485 * [user mapping goes away] 486 * write_to(page); 487 * !PageDirty(page) [good] 488 * SetPageDirty(page); 489 * put_page(page); 490 * !page_count(page) [good, discard it] 491 * 492 * [oops, our write_to data is lost] 493 * 494 * Reversing the order of the tests ensures such a situation cannot 495 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 496 * load is not satisfied before that of page->_count. 497 * 498 * Note that if SetPageDirty is always performed via set_page_dirty, 499 * and thus under tree_lock, then this ordering is not required. 500 */ 501 if (!page_freeze_refs(page, 2)) 502 goto cannot_free; 503 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 504 if (unlikely(PageDirty(page))) { 505 page_unfreeze_refs(page, 2); 506 goto cannot_free; 507 } 508 509 if (PageSwapCache(page)) { 510 swp_entry_t swap = { .val = page_private(page) }; 511 __delete_from_swap_cache(page); 512 spin_unlock_irq(&mapping->tree_lock); 513 swapcache_free(swap, page); 514 } else { 515 void (*freepage)(struct page *); 516 517 freepage = mapping->a_ops->freepage; 518 519 __delete_from_page_cache(page); 520 spin_unlock_irq(&mapping->tree_lock); 521 mem_cgroup_uncharge_cache_page(page); 522 523 if (freepage != NULL) 524 freepage(page); 525 } 526 527 return 1; 528 529cannot_free: 530 spin_unlock_irq(&mapping->tree_lock); 531 return 0; 532} 533 534/* 535 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 536 * someone else has a ref on the page, abort and return 0. If it was 537 * successfully detached, return 1. Assumes the caller has a single ref on 538 * this page. 539 */ 540int remove_mapping(struct address_space *mapping, struct page *page) 541{ 542 if (__remove_mapping(mapping, page)) { 543 /* 544 * Unfreezing the refcount with 1 rather than 2 effectively 545 * drops the pagecache ref for us without requiring another 546 * atomic operation. 547 */ 548 page_unfreeze_refs(page, 1); 549 return 1; 550 } 551 return 0; 552} 553 554/** 555 * putback_lru_page - put previously isolated page onto appropriate LRU list 556 * @page: page to be put back to appropriate lru list 557 * 558 * Add previously isolated @page to appropriate LRU list. 559 * Page may still be unevictable for other reasons. 560 * 561 * lru_lock must not be held, interrupts must be enabled. 562 */ 563void putback_lru_page(struct page *page) 564{ 565 int lru; 566 int active = !!TestClearPageActive(page); 567 int was_unevictable = PageUnevictable(page); 568 569 VM_BUG_ON(PageLRU(page)); 570 571redo: 572 ClearPageUnevictable(page); 573 574 if (page_evictable(page, NULL)) { 575 /* 576 * For evictable pages, we can use the cache. 577 * In event of a race, worst case is we end up with an 578 * unevictable page on [in]active list. 579 * We know how to handle that. 580 */ 581 lru = active + page_lru_base_type(page); 582 lru_cache_add_lru(page, lru); 583 } else { 584 /* 585 * Put unevictable pages directly on zone's unevictable 586 * list. 587 */ 588 lru = LRU_UNEVICTABLE; 589 add_page_to_unevictable_list(page); 590 /* 591 * When racing with an mlock clearing (page is 592 * unlocked), make sure that if the other thread does 593 * not observe our setting of PG_lru and fails 594 * isolation, we see PG_mlocked cleared below and move 595 * the page back to the evictable list. 596 * 597 * The other side is TestClearPageMlocked(). 598 */ 599 smp_mb(); 600 } 601 602 /* 603 * page's status can change while we move it among lru. If an evictable 604 * page is on unevictable list, it never be freed. To avoid that, 605 * check after we added it to the list, again. 606 */ 607 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 608 if (!isolate_lru_page(page)) { 609 put_page(page); 610 goto redo; 611 } 612 /* This means someone else dropped this page from LRU 613 * So, it will be freed or putback to LRU again. There is 614 * nothing to do here. 615 */ 616 } 617 618 if (was_unevictable && lru != LRU_UNEVICTABLE) 619 count_vm_event(UNEVICTABLE_PGRESCUED); 620 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 621 count_vm_event(UNEVICTABLE_PGCULLED); 622 623 put_page(page); /* drop ref from isolate */ 624} 625 626enum page_references { 627 PAGEREF_RECLAIM, 628 PAGEREF_RECLAIM_CLEAN, 629 PAGEREF_KEEP, 630 PAGEREF_ACTIVATE, 631}; 632 633static enum page_references page_check_references(struct page *page, 634 struct scan_control *sc) 635{ 636 int referenced_ptes, referenced_page; 637 unsigned long vm_flags; 638 639 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 640 referenced_page = TestClearPageReferenced(page); 641 642 /* Lumpy reclaim - ignore references */ 643 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) 644 return PAGEREF_RECLAIM; 645 646 /* 647 * Mlock lost the isolation race with us. Let try_to_unmap() 648 * move the page to the unevictable list. 649 */ 650 if (vm_flags & VM_LOCKED) 651 return PAGEREF_RECLAIM; 652 653 if (referenced_ptes) { 654 if (PageAnon(page)) 655 return PAGEREF_ACTIVATE; 656 /* 657 * All mapped pages start out with page table 658 * references from the instantiating fault, so we need 659 * to look twice if a mapped file page is used more 660 * than once. 661 * 662 * Mark it and spare it for another trip around the 663 * inactive list. Another page table reference will 664 * lead to its activation. 665 * 666 * Note: the mark is set for activated pages as well 667 * so that recently deactivated but used pages are 668 * quickly recovered. 669 */ 670 SetPageReferenced(page); 671 672 if (referenced_page) 673 return PAGEREF_ACTIVATE; 674 675 return PAGEREF_KEEP; 676 } 677 678 /* Reclaim if clean, defer dirty pages to writeback */ 679 if (referenced_page && !PageSwapBacked(page)) 680 return PAGEREF_RECLAIM_CLEAN; 681 682 return PAGEREF_RECLAIM; 683} 684 685static noinline_for_stack void free_page_list(struct list_head *free_pages) 686{ 687 struct pagevec freed_pvec; 688 struct page *page, *tmp; 689 690 pagevec_init(&freed_pvec, 1); 691 692 list_for_each_entry_safe(page, tmp, free_pages, lru) { 693 list_del(&page->lru); 694 if (!pagevec_add(&freed_pvec, page)) { 695 __pagevec_free(&freed_pvec); 696 pagevec_reinit(&freed_pvec); 697 } 698 } 699 700 pagevec_free(&freed_pvec); 701} 702 703/* 704 * shrink_page_list() returns the number of reclaimed pages 705 */ 706static unsigned long shrink_page_list(struct list_head *page_list, 707 struct zone *zone, 708 struct scan_control *sc) 709{ 710 LIST_HEAD(ret_pages); 711 LIST_HEAD(free_pages); 712 int pgactivate = 0; 713 unsigned long nr_dirty = 0; 714 unsigned long nr_congested = 0; 715 unsigned long nr_reclaimed = 0; 716 717 cond_resched(); 718 719 while (!list_empty(page_list)) { 720 enum page_references references; 721 struct address_space *mapping; 722 struct page *page; 723 int may_enter_fs; 724 725 cond_resched(); 726 727 page = lru_to_page(page_list); 728 list_del(&page->lru); 729 730 if (!trylock_page(page)) 731 goto keep; 732 733 VM_BUG_ON(PageActive(page)); 734 VM_BUG_ON(page_zone(page) != zone); 735 736 sc->nr_scanned++; 737 738 if (unlikely(!page_evictable(page, NULL))) 739 goto cull_mlocked; 740 741 if (!sc->may_unmap && page_mapped(page)) 742 goto keep_locked; 743 744 /* Double the slab pressure for mapped and swapcache pages */ 745 if (page_mapped(page) || PageSwapCache(page)) 746 sc->nr_scanned++; 747 748 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 749 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 750 751 if (PageWriteback(page)) { 752 /* 753 * Synchronous reclaim is performed in two passes, 754 * first an asynchronous pass over the list to 755 * start parallel writeback, and a second synchronous 756 * pass to wait for the IO to complete. Wait here 757 * for any page for which writeback has already 758 * started. 759 */ 760 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && 761 may_enter_fs) 762 wait_on_page_writeback(page); 763 else { 764 unlock_page(page); 765 goto keep_lumpy; 766 } 767 } 768 769 references = page_check_references(page, sc); 770 switch (references) { 771 case PAGEREF_ACTIVATE: 772 goto activate_locked; 773 case PAGEREF_KEEP: 774 goto keep_locked; 775 case PAGEREF_RECLAIM: 776 case PAGEREF_RECLAIM_CLEAN: 777 ; /* try to reclaim the page below */ 778 } 779 780 /* 781 * Anonymous process memory has backing store? 782 * Try to allocate it some swap space here. 783 */ 784 if (PageAnon(page) && !PageSwapCache(page)) { 785 if (!(sc->gfp_mask & __GFP_IO)) 786 goto keep_locked; 787 if (!add_to_swap(page)) 788 goto activate_locked; 789 may_enter_fs = 1; 790 } 791 792 mapping = page_mapping(page); 793 794 /* 795 * The page is mapped into the page tables of one or more 796 * processes. Try to unmap it here. 797 */ 798 if (page_mapped(page) && mapping) { 799 switch (try_to_unmap(page, TTU_UNMAP)) { 800 case SWAP_FAIL: 801 goto activate_locked; 802 case SWAP_AGAIN: 803 goto keep_locked; 804 case SWAP_MLOCK: 805 goto cull_mlocked; 806 case SWAP_SUCCESS: 807 ; /* try to free the page below */ 808 } 809 } 810 811 if (PageDirty(page)) { 812 nr_dirty++; 813 814 if (references == PAGEREF_RECLAIM_CLEAN) 815 goto keep_locked; 816 if (!may_enter_fs) 817 goto keep_locked; 818 if (!sc->may_writepage) 819 goto keep_locked; 820 821 /* Page is dirty, try to write it out here */ 822 switch (pageout(page, mapping, sc)) { 823 case PAGE_KEEP: 824 nr_congested++; 825 goto keep_locked; 826 case PAGE_ACTIVATE: 827 goto activate_locked; 828 case PAGE_SUCCESS: 829 if (PageWriteback(page)) 830 goto keep_lumpy; 831 if (PageDirty(page)) 832 goto keep; 833 834 /* 835 * A synchronous write - probably a ramdisk. Go 836 * ahead and try to reclaim the page. 837 */ 838 if (!trylock_page(page)) 839 goto keep; 840 if (PageDirty(page) || PageWriteback(page)) 841 goto keep_locked; 842 mapping = page_mapping(page); 843 case PAGE_CLEAN: 844 ; /* try to free the page below */ 845 } 846 } 847 848 /* 849 * If the page has buffers, try to free the buffer mappings 850 * associated with this page. If we succeed we try to free 851 * the page as well. 852 * 853 * We do this even if the page is PageDirty(). 854 * try_to_release_page() does not perform I/O, but it is 855 * possible for a page to have PageDirty set, but it is actually 856 * clean (all its buffers are clean). This happens if the 857 * buffers were written out directly, with submit_bh(). ext3 858 * will do this, as well as the blockdev mapping. 859 * try_to_release_page() will discover that cleanness and will 860 * drop the buffers and mark the page clean - it can be freed. 861 * 862 * Rarely, pages can have buffers and no ->mapping. These are 863 * the pages which were not successfully invalidated in 864 * truncate_complete_page(). We try to drop those buffers here 865 * and if that worked, and the page is no longer mapped into 866 * process address space (page_count == 1) it can be freed. 867 * Otherwise, leave the page on the LRU so it is swappable. 868 */ 869 if (page_has_private(page)) { 870 if (!try_to_release_page(page, sc->gfp_mask)) 871 goto activate_locked; 872 if (!mapping && page_count(page) == 1) { 873 unlock_page(page); 874 if (put_page_testzero(page)) 875 goto free_it; 876 else { 877 /* 878 * rare race with speculative reference. 879 * the speculative reference will free 880 * this page shortly, so we may 881 * increment nr_reclaimed here (and 882 * leave it off the LRU). 883 */ 884 nr_reclaimed++; 885 continue; 886 } 887 } 888 } 889 890 if (!mapping || !__remove_mapping(mapping, page)) 891 goto keep_locked; 892 893 /* 894 * At this point, we have no other references and there is 895 * no way to pick any more up (removed from LRU, removed 896 * from pagecache). Can use non-atomic bitops now (and 897 * we obviously don't have to worry about waking up a process 898 * waiting on the page lock, because there are no references. 899 */ 900 __clear_page_locked(page); 901free_it: 902 nr_reclaimed++; 903 904 /* 905 * Is there need to periodically free_page_list? It would 906 * appear not as the counts should be low 907 */ 908 list_add(&page->lru, &free_pages); 909 continue; 910 911cull_mlocked: 912 if (PageSwapCache(page)) 913 try_to_free_swap(page); 914 unlock_page(page); 915 putback_lru_page(page); 916 reset_reclaim_mode(sc); 917 continue; 918 919activate_locked: 920 /* Not a candidate for swapping, so reclaim swap space. */ 921 if (PageSwapCache(page) && vm_swap_full()) 922 try_to_free_swap(page); 923 VM_BUG_ON(PageActive(page)); 924 SetPageActive(page); 925 pgactivate++; 926keep_locked: 927 unlock_page(page); 928keep: 929 reset_reclaim_mode(sc); 930keep_lumpy: 931 list_add(&page->lru, &ret_pages); 932 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 933 } 934 935 /* 936 * Tag a zone as congested if all the dirty pages encountered were 937 * backed by a congested BDI. In this case, reclaimers should just 938 * back off and wait for congestion to clear because further reclaim 939 * will encounter the same problem 940 */ 941 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) 942 zone_set_flag(zone, ZONE_CONGESTED); 943 944 free_page_list(&free_pages); 945 946 list_splice(&ret_pages, page_list); 947 count_vm_events(PGACTIVATE, pgactivate); 948 return nr_reclaimed; 949} 950 951/* 952 * Attempt to remove the specified page from its LRU. Only take this page 953 * if it is of the appropriate PageActive status. Pages which are being 954 * freed elsewhere are also ignored. 955 * 956 * page: page to consider 957 * mode: one of the LRU isolation modes defined above 958 * 959 * returns 0 on success, -ve errno on failure. 960 */ 961int __isolate_lru_page(struct page *page, int mode, int file) 962{ 963 int ret = -EINVAL; 964 965 /* Only take pages on the LRU. */ 966 if (!PageLRU(page)) 967 return ret; 968 969 /* 970 * When checking the active state, we need to be sure we are 971 * dealing with comparible boolean values. Take the logical not 972 * of each. 973 */ 974 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 975 return ret; 976 977 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 978 return ret; 979 980 /* 981 * When this function is being called for lumpy reclaim, we 982 * initially look into all LRU pages, active, inactive and 983 * unevictable; only give shrink_page_list evictable pages. 984 */ 985 if (PageUnevictable(page)) 986 return ret; 987 988 ret = -EBUSY; 989 990 if (likely(get_page_unless_zero(page))) { 991 /* 992 * Be careful not to clear PageLRU until after we're 993 * sure the page is not being freed elsewhere -- the 994 * page release code relies on it. 995 */ 996 ClearPageLRU(page); 997 ret = 0; 998 } 999 1000 return ret; 1001} 1002 1003/* 1004 * zone->lru_lock is heavily contended. Some of the functions that 1005 * shrink the lists perform better by taking out a batch of pages 1006 * and working on them outside the LRU lock. 1007 * 1008 * For pagecache intensive workloads, this function is the hottest 1009 * spot in the kernel (apart from copy_*_user functions). 1010 * 1011 * Appropriate locks must be held before calling this function. 1012 * 1013 * @nr_to_scan: The number of pages to look through on the list. 1014 * @src: The LRU list to pull pages off. 1015 * @dst: The temp list to put pages on to. 1016 * @scanned: The number of pages that were scanned. 1017 * @order: The caller's attempted allocation order 1018 * @mode: One of the LRU isolation modes 1019 * @file: True [1] if isolating file [!anon] pages 1020 * 1021 * returns how many pages were moved onto *@dst. 1022 */ 1023static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 1024 struct list_head *src, struct list_head *dst, 1025 unsigned long *scanned, int order, int mode, int file) 1026{ 1027 unsigned long nr_taken = 0; 1028 unsigned long nr_lumpy_taken = 0; 1029 unsigned long nr_lumpy_dirty = 0; 1030 unsigned long nr_lumpy_failed = 0; 1031 unsigned long scan; 1032 1033 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 1034 struct page *page; 1035 unsigned long pfn; 1036 unsigned long end_pfn; 1037 unsigned long page_pfn; 1038 int zone_id; 1039 1040 page = lru_to_page(src); 1041 prefetchw_prev_lru_page(page, src, flags); 1042 1043 VM_BUG_ON(!PageLRU(page)); 1044 1045 switch (__isolate_lru_page(page, mode, file)) { 1046 case 0: 1047 list_move(&page->lru, dst); 1048 mem_cgroup_del_lru(page); 1049 nr_taken += hpage_nr_pages(page); 1050 break; 1051 1052 case -EBUSY: 1053 /* else it is being freed elsewhere */ 1054 list_move(&page->lru, src); 1055 mem_cgroup_rotate_lru_list(page, page_lru(page)); 1056 continue; 1057 1058 default: 1059 BUG(); 1060 } 1061 1062 if (!order) 1063 continue; 1064 1065 /* 1066 * Attempt to take all pages in the order aligned region 1067 * surrounding the tag page. Only take those pages of 1068 * the same active state as that tag page. We may safely 1069 * round the target page pfn down to the requested order 1070 * as the mem_map is guaranteed valid out to MAX_ORDER, 1071 * where that page is in a different zone we will detect 1072 * it from its zone id and abort this block scan. 1073 */ 1074 zone_id = page_zone_id(page); 1075 page_pfn = page_to_pfn(page); 1076 pfn = page_pfn & ~((1 << order) - 1); 1077 end_pfn = pfn + (1 << order); 1078 for (; pfn < end_pfn; pfn++) { 1079 struct page *cursor_page; 1080 1081 /* The target page is in the block, ignore it. */ 1082 if (unlikely(pfn == page_pfn)) 1083 continue; 1084 1085 /* Avoid holes within the zone. */ 1086 if (unlikely(!pfn_valid_within(pfn))) 1087 break; 1088 1089 cursor_page = pfn_to_page(pfn); 1090 1091 /* Check that we have not crossed a zone boundary. */ 1092 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1093 break; 1094 1095 /* 1096 * If we don't have enough swap space, reclaiming of 1097 * anon page which don't already have a swap slot is 1098 * pointless. 1099 */ 1100 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1101 !PageSwapCache(cursor_page)) 1102 break; 1103 1104 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1105 list_move(&cursor_page->lru, dst); 1106 mem_cgroup_del_lru(cursor_page); 1107 nr_taken += hpage_nr_pages(page); 1108 nr_lumpy_taken++; 1109 if (PageDirty(cursor_page)) 1110 nr_lumpy_dirty++; 1111 scan++; 1112 } else { 1113 /* the page is freed already. */ 1114 if (!page_count(cursor_page)) 1115 continue; 1116 break; 1117 } 1118 } 1119 1120 /* If we break out of the loop above, lumpy reclaim failed */ 1121 if (pfn < end_pfn) 1122 nr_lumpy_failed++; 1123 } 1124 1125 *scanned = scan; 1126 1127 trace_mm_vmscan_lru_isolate(order, 1128 nr_to_scan, scan, 1129 nr_taken, 1130 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1131 mode); 1132 return nr_taken; 1133} 1134 1135static unsigned long isolate_pages_global(unsigned long nr, 1136 struct list_head *dst, 1137 unsigned long *scanned, int order, 1138 int mode, struct zone *z, 1139 int active, int file) 1140{ 1141 int lru = LRU_BASE; 1142 if (active) 1143 lru += LRU_ACTIVE; 1144 if (file) 1145 lru += LRU_FILE; 1146 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1147 mode, file); 1148} 1149 1150/* 1151 * clear_active_flags() is a helper for shrink_active_list(), clearing 1152 * any active bits from the pages in the list. 1153 */ 1154static unsigned long clear_active_flags(struct list_head *page_list, 1155 unsigned int *count) 1156{ 1157 int nr_active = 0; 1158 int lru; 1159 struct page *page; 1160 1161 list_for_each_entry(page, page_list, lru) { 1162 int numpages = hpage_nr_pages(page); 1163 lru = page_lru_base_type(page); 1164 if (PageActive(page)) { 1165 lru += LRU_ACTIVE; 1166 ClearPageActive(page); 1167 nr_active += numpages; 1168 } 1169 if (count) 1170 count[lru] += numpages; 1171 } 1172 1173 return nr_active; 1174} 1175 1176/** 1177 * isolate_lru_page - tries to isolate a page from its LRU list 1178 * @page: page to isolate from its LRU list 1179 * 1180 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1181 * vmstat statistic corresponding to whatever LRU list the page was on. 1182 * 1183 * Returns 0 if the page was removed from an LRU list. 1184 * Returns -EBUSY if the page was not on an LRU list. 1185 * 1186 * The returned page will have PageLRU() cleared. If it was found on 1187 * the active list, it will have PageActive set. If it was found on 1188 * the unevictable list, it will have the PageUnevictable bit set. That flag 1189 * may need to be cleared by the caller before letting the page go. 1190 * 1191 * The vmstat statistic corresponding to the list on which the page was 1192 * found will be decremented. 1193 * 1194 * Restrictions: 1195 * (1) Must be called with an elevated refcount on the page. This is a 1196 * fundamentnal difference from isolate_lru_pages (which is called 1197 * without a stable reference). 1198 * (2) the lru_lock must not be held. 1199 * (3) interrupts must be enabled. 1200 */ 1201int isolate_lru_page(struct page *page) 1202{ 1203 int ret = -EBUSY; 1204 1205 if (PageLRU(page)) { 1206 struct zone *zone = page_zone(page); 1207 1208 spin_lock_irq(&zone->lru_lock); 1209 if (PageLRU(page) && get_page_unless_zero(page)) { 1210 int lru = page_lru(page); 1211 ret = 0; 1212 ClearPageLRU(page); 1213 1214 del_page_from_lru_list(zone, page, lru); 1215 } 1216 spin_unlock_irq(&zone->lru_lock); 1217 } 1218 return ret; 1219} 1220 1221/* 1222 * Are there way too many processes in the direct reclaim path already? 1223 */ 1224static int too_many_isolated(struct zone *zone, int file, 1225 struct scan_control *sc) 1226{ 1227 unsigned long inactive, isolated; 1228 1229 if (current_is_kswapd()) 1230 return 0; 1231 1232 if (!scanning_global_lru(sc)) 1233 return 0; 1234 1235 if (file) { 1236 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1237 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1238 } else { 1239 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1240 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1241 } 1242 1243 return isolated > inactive; 1244} 1245 1246/* 1247 * TODO: Try merging with migrations version of putback_lru_pages 1248 */ 1249static noinline_for_stack void 1250putback_lru_pages(struct zone *zone, struct scan_control *sc, 1251 unsigned long nr_anon, unsigned long nr_file, 1252 struct list_head *page_list) 1253{ 1254 struct page *page; 1255 struct pagevec pvec; 1256 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1257 1258 pagevec_init(&pvec, 1); 1259 1260 /* 1261 * Put back any unfreeable pages. 1262 */ 1263 spin_lock(&zone->lru_lock); 1264 while (!list_empty(page_list)) { 1265 int lru; 1266 page = lru_to_page(page_list); 1267 VM_BUG_ON(PageLRU(page)); 1268 list_del(&page->lru); 1269 if (unlikely(!page_evictable(page, NULL))) { 1270 spin_unlock_irq(&zone->lru_lock); 1271 putback_lru_page(page); 1272 spin_lock_irq(&zone->lru_lock); 1273 continue; 1274 } 1275 SetPageLRU(page); 1276 lru = page_lru(page); 1277 add_page_to_lru_list(zone, page, lru); 1278 if (is_active_lru(lru)) { 1279 int file = is_file_lru(lru); 1280 int numpages = hpage_nr_pages(page); 1281 reclaim_stat->recent_rotated[file] += numpages; 1282 } 1283 if (!pagevec_add(&pvec, page)) { 1284 spin_unlock_irq(&zone->lru_lock); 1285 __pagevec_release(&pvec); 1286 spin_lock_irq(&zone->lru_lock); 1287 } 1288 } 1289 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1290 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1291 1292 spin_unlock_irq(&zone->lru_lock); 1293 pagevec_release(&pvec); 1294} 1295 1296static noinline_for_stack void update_isolated_counts(struct zone *zone, 1297 struct scan_control *sc, 1298 unsigned long *nr_anon, 1299 unsigned long *nr_file, 1300 struct list_head *isolated_list) 1301{ 1302 unsigned long nr_active; 1303 unsigned int count[NR_LRU_LISTS] = { 0, }; 1304 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1305 1306 nr_active = clear_active_flags(isolated_list, count); 1307 __count_vm_events(PGDEACTIVATE, nr_active); 1308 1309 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1310 -count[LRU_ACTIVE_FILE]); 1311 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1312 -count[LRU_INACTIVE_FILE]); 1313 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1314 -count[LRU_ACTIVE_ANON]); 1315 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1316 -count[LRU_INACTIVE_ANON]); 1317 1318 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1319 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1320 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1321 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1322 1323 reclaim_stat->recent_scanned[0] += *nr_anon; 1324 reclaim_stat->recent_scanned[1] += *nr_file; 1325} 1326 1327/* 1328 * Returns true if the caller should wait to clean dirty/writeback pages. 1329 * 1330 * If we are direct reclaiming for contiguous pages and we do not reclaim 1331 * everything in the list, try again and wait for writeback IO to complete. 1332 * This will stall high-order allocations noticeably. Only do that when really 1333 * need to free the pages under high memory pressure. 1334 */ 1335static inline bool should_reclaim_stall(unsigned long nr_taken, 1336 unsigned long nr_freed, 1337 int priority, 1338 struct scan_control *sc) 1339{ 1340 int lumpy_stall_priority; 1341 1342 /* kswapd should not stall on sync IO */ 1343 if (current_is_kswapd()) 1344 return false; 1345 1346 /* Only stall on lumpy reclaim */ 1347 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) 1348 return false; 1349 1350 /* If we have relaimed everything on the isolated list, no stall */ 1351 if (nr_freed == nr_taken) 1352 return false; 1353 1354 /* 1355 * For high-order allocations, there are two stall thresholds. 1356 * High-cost allocations stall immediately where as lower 1357 * order allocations such as stacks require the scanning 1358 * priority to be much higher before stalling. 1359 */ 1360 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1361 lumpy_stall_priority = DEF_PRIORITY; 1362 else 1363 lumpy_stall_priority = DEF_PRIORITY / 3; 1364 1365 return priority <= lumpy_stall_priority; 1366} 1367 1368/* 1369 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1370 * of reclaimed pages 1371 */ 1372static noinline_for_stack unsigned long 1373shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1374 struct scan_control *sc, int priority, int file) 1375{ 1376 LIST_HEAD(page_list); 1377 unsigned long nr_scanned; 1378 unsigned long nr_reclaimed = 0; 1379 unsigned long nr_taken; 1380 unsigned long nr_anon; 1381 unsigned long nr_file; 1382 1383 while (unlikely(too_many_isolated(zone, file, sc))) { 1384 congestion_wait(BLK_RW_ASYNC, HZ/10); 1385 1386 /* We are about to die and free our memory. Return now. */ 1387 if (fatal_signal_pending(current)) 1388 return SWAP_CLUSTER_MAX; 1389 } 1390 1391 set_reclaim_mode(priority, sc, false); 1392 lru_add_drain(); 1393 spin_lock_irq(&zone->lru_lock); 1394 1395 if (scanning_global_lru(sc)) { 1396 nr_taken = isolate_pages_global(nr_to_scan, 1397 &page_list, &nr_scanned, sc->order, 1398 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1399 ISOLATE_BOTH : ISOLATE_INACTIVE, 1400 zone, 0, file); 1401 zone->pages_scanned += nr_scanned; 1402 if (current_is_kswapd()) 1403 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1404 nr_scanned); 1405 else 1406 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1407 nr_scanned); 1408 } else { 1409 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1410 &page_list, &nr_scanned, sc->order, 1411 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? 1412 ISOLATE_BOTH : ISOLATE_INACTIVE, 1413 zone, sc->mem_cgroup, 1414 0, file); 1415 /* 1416 * mem_cgroup_isolate_pages() keeps track of 1417 * scanned pages on its own. 1418 */ 1419 } 1420 1421 if (nr_taken == 0) { 1422 spin_unlock_irq(&zone->lru_lock); 1423 return 0; 1424 } 1425 1426 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1427 1428 spin_unlock_irq(&zone->lru_lock); 1429 1430 nr_reclaimed = shrink_page_list(&page_list, zone, sc); 1431 1432 /* Check if we should syncronously wait for writeback */ 1433 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1434 set_reclaim_mode(priority, sc, true); 1435 nr_reclaimed += shrink_page_list(&page_list, zone, sc); 1436 } 1437 1438 local_irq_disable(); 1439 if (current_is_kswapd()) 1440 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1441 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1442 1443 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1444 1445 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1446 zone_idx(zone), 1447 nr_scanned, nr_reclaimed, 1448 priority, 1449 trace_shrink_flags(file, sc->reclaim_mode)); 1450 return nr_reclaimed; 1451} 1452 1453/* 1454 * This moves pages from the active list to the inactive list. 1455 * 1456 * We move them the other way if the page is referenced by one or more 1457 * processes, from rmap. 1458 * 1459 * If the pages are mostly unmapped, the processing is fast and it is 1460 * appropriate to hold zone->lru_lock across the whole operation. But if 1461 * the pages are mapped, the processing is slow (page_referenced()) so we 1462 * should drop zone->lru_lock around each page. It's impossible to balance 1463 * this, so instead we remove the pages from the LRU while processing them. 1464 * It is safe to rely on PG_active against the non-LRU pages in here because 1465 * nobody will play with that bit on a non-LRU page. 1466 * 1467 * The downside is that we have to touch page->_count against each page. 1468 * But we had to alter page->flags anyway. 1469 */ 1470 1471static void move_active_pages_to_lru(struct zone *zone, 1472 struct list_head *list, 1473 enum lru_list lru) 1474{ 1475 unsigned long pgmoved = 0; 1476 struct pagevec pvec; 1477 struct page *page; 1478 1479 pagevec_init(&pvec, 1); 1480 1481 while (!list_empty(list)) { 1482 page = lru_to_page(list); 1483 1484 VM_BUG_ON(PageLRU(page)); 1485 SetPageLRU(page); 1486 1487 list_move(&page->lru, &zone->lru[lru].list); 1488 mem_cgroup_add_lru_list(page, lru); 1489 pgmoved += hpage_nr_pages(page); 1490 1491 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1492 spin_unlock_irq(&zone->lru_lock); 1493 if (buffer_heads_over_limit) 1494 pagevec_strip(&pvec); 1495 __pagevec_release(&pvec); 1496 spin_lock_irq(&zone->lru_lock); 1497 } 1498 } 1499 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1500 if (!is_active_lru(lru)) 1501 __count_vm_events(PGDEACTIVATE, pgmoved); 1502} 1503 1504static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1505 struct scan_control *sc, int priority, int file) 1506{ 1507 unsigned long nr_taken; 1508 unsigned long pgscanned; 1509 unsigned long vm_flags; 1510 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1511 LIST_HEAD(l_active); 1512 LIST_HEAD(l_inactive); 1513 struct page *page; 1514 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1515 unsigned long nr_rotated = 0; 1516 1517 lru_add_drain(); 1518 spin_lock_irq(&zone->lru_lock); 1519 if (scanning_global_lru(sc)) { 1520 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1521 &pgscanned, sc->order, 1522 ISOLATE_ACTIVE, zone, 1523 1, file); 1524 zone->pages_scanned += pgscanned; 1525 } else { 1526 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1527 &pgscanned, sc->order, 1528 ISOLATE_ACTIVE, zone, 1529 sc->mem_cgroup, 1, file); 1530 /* 1531 * mem_cgroup_isolate_pages() keeps track of 1532 * scanned pages on its own. 1533 */ 1534 } 1535 1536 reclaim_stat->recent_scanned[file] += nr_taken; 1537 1538 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1539 if (file) 1540 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1541 else 1542 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1543 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1544 spin_unlock_irq(&zone->lru_lock); 1545 1546 while (!list_empty(&l_hold)) { 1547 cond_resched(); 1548 page = lru_to_page(&l_hold); 1549 list_del(&page->lru); 1550 1551 if (unlikely(!page_evictable(page, NULL))) { 1552 putback_lru_page(page); 1553 continue; 1554 } 1555 1556 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1557 nr_rotated += hpage_nr_pages(page); 1558 /* 1559 * Identify referenced, file-backed active pages and 1560 * give them one more trip around the active list. So 1561 * that executable code get better chances to stay in 1562 * memory under moderate memory pressure. Anon pages 1563 * are not likely to be evicted by use-once streaming 1564 * IO, plus JVM can create lots of anon VM_EXEC pages, 1565 * so we ignore them here. 1566 */ 1567 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1568 list_add(&page->lru, &l_active); 1569 continue; 1570 } 1571 } 1572 1573 ClearPageActive(page); /* we are de-activating */ 1574 list_add(&page->lru, &l_inactive); 1575 } 1576 1577 /* 1578 * Move pages back to the lru list. 1579 */ 1580 spin_lock_irq(&zone->lru_lock); 1581 /* 1582 * Count referenced pages from currently used mappings as rotated, 1583 * even though only some of them are actually re-activated. This 1584 * helps balance scan pressure between file and anonymous pages in 1585 * get_scan_ratio. 1586 */ 1587 reclaim_stat->recent_rotated[file] += nr_rotated; 1588 1589 move_active_pages_to_lru(zone, &l_active, 1590 LRU_ACTIVE + file * LRU_FILE); 1591 move_active_pages_to_lru(zone, &l_inactive, 1592 LRU_BASE + file * LRU_FILE); 1593 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1594 spin_unlock_irq(&zone->lru_lock); 1595} 1596 1597#ifdef CONFIG_SWAP 1598static int inactive_anon_is_low_global(struct zone *zone) 1599{ 1600 unsigned long active, inactive; 1601 1602 active = zone_page_state(zone, NR_ACTIVE_ANON); 1603 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1604 1605 if (inactive * zone->inactive_ratio < active) 1606 return 1; 1607 1608 return 0; 1609} 1610 1611/** 1612 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1613 * @zone: zone to check 1614 * @sc: scan control of this context 1615 * 1616 * Returns true if the zone does not have enough inactive anon pages, 1617 * meaning some active anon pages need to be deactivated. 1618 */ 1619static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1620{ 1621 int low; 1622 1623 /* 1624 * If we don't have swap space, anonymous page deactivation 1625 * is pointless. 1626 */ 1627 if (!total_swap_pages) 1628 return 0; 1629 1630 if (scanning_global_lru(sc)) 1631 low = inactive_anon_is_low_global(zone); 1632 else 1633 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1634 return low; 1635} 1636#else 1637static inline int inactive_anon_is_low(struct zone *zone, 1638 struct scan_control *sc) 1639{ 1640 return 0; 1641} 1642#endif 1643 1644static int inactive_file_is_low_global(struct zone *zone) 1645{ 1646 unsigned long active, inactive; 1647 1648 active = zone_page_state(zone, NR_ACTIVE_FILE); 1649 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1650 1651 return (active > inactive); 1652} 1653 1654/** 1655 * inactive_file_is_low - check if file pages need to be deactivated 1656 * @zone: zone to check 1657 * @sc: scan control of this context 1658 * 1659 * When the system is doing streaming IO, memory pressure here 1660 * ensures that active file pages get deactivated, until more 1661 * than half of the file pages are on the inactive list. 1662 * 1663 * Once we get to that situation, protect the system's working 1664 * set from being evicted by disabling active file page aging. 1665 * 1666 * This uses a different ratio than the anonymous pages, because 1667 * the page cache uses a use-once replacement algorithm. 1668 */ 1669static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1670{ 1671 int low; 1672 1673 if (scanning_global_lru(sc)) 1674 low = inactive_file_is_low_global(zone); 1675 else 1676 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1677 return low; 1678} 1679 1680static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1681 int file) 1682{ 1683 if (file) 1684 return inactive_file_is_low(zone, sc); 1685 else 1686 return inactive_anon_is_low(zone, sc); 1687} 1688 1689static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1690 struct zone *zone, struct scan_control *sc, int priority) 1691{ 1692 int file = is_file_lru(lru); 1693 1694 if (is_active_lru(lru)) { 1695 if (inactive_list_is_low(zone, sc, file)) 1696 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1697 return 0; 1698 } 1699 1700 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1701} 1702 1703/* 1704 * Smallish @nr_to_scan's are deposited in @nr_saved_scan, 1705 * until we collected @swap_cluster_max pages to scan. 1706 */ 1707static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, 1708 unsigned long *nr_saved_scan) 1709{ 1710 unsigned long nr; 1711 1712 *nr_saved_scan += nr_to_scan; 1713 nr = *nr_saved_scan; 1714 1715 if (nr >= SWAP_CLUSTER_MAX) 1716 *nr_saved_scan = 0; 1717 else 1718 nr = 0; 1719 1720 return nr; 1721} 1722 1723/* 1724 * Determine how aggressively the anon and file LRU lists should be 1725 * scanned. The relative value of each set of LRU lists is determined 1726 * by looking at the fraction of the pages scanned we did rotate back 1727 * onto the active list instead of evict. 1728 * 1729 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1730 */ 1731static void get_scan_count(struct zone *zone, struct scan_control *sc, 1732 unsigned long *nr, int priority) 1733{ 1734 unsigned long anon, file, free; 1735 unsigned long anon_prio, file_prio; 1736 unsigned long ap, fp; 1737 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1738 u64 fraction[2], denominator; 1739 enum lru_list l; 1740 int noswap = 0; 1741 1742 /* If we have no swap space, do not bother scanning anon pages. */ 1743 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1744 noswap = 1; 1745 fraction[0] = 0; 1746 fraction[1] = 1; 1747 denominator = 1; 1748 goto out; 1749 } 1750 1751 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1752 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1753 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1754 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1755 1756 if (scanning_global_lru(sc)) { 1757 free = zone_page_state(zone, NR_FREE_PAGES); 1758 /* If we have very few page cache pages, 1759 force-scan anon pages. */ 1760 if (unlikely(file + free <= high_wmark_pages(zone))) { 1761 fraction[0] = 1; 1762 fraction[1] = 0; 1763 denominator = 1; 1764 goto out; 1765 } 1766 } 1767 1768 /* 1769 * With swappiness at 100, anonymous and file have the same priority. 1770 * This scanning priority is essentially the inverse of IO cost. 1771 */ 1772 anon_prio = sc->swappiness; 1773 file_prio = 200 - sc->swappiness; 1774 1775 /* 1776 * OK, so we have swap space and a fair amount of page cache 1777 * pages. We use the recently rotated / recently scanned 1778 * ratios to determine how valuable each cache is. 1779 * 1780 * Because workloads change over time (and to avoid overflow) 1781 * we keep these statistics as a floating average, which ends 1782 * up weighing recent references more than old ones. 1783 * 1784 * anon in [0], file in [1] 1785 */ 1786 spin_lock_irq(&zone->lru_lock); 1787 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1788 reclaim_stat->recent_scanned[0] /= 2; 1789 reclaim_stat->recent_rotated[0] /= 2; 1790 } 1791 1792 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1793 reclaim_stat->recent_scanned[1] /= 2; 1794 reclaim_stat->recent_rotated[1] /= 2; 1795 } 1796 1797 /* 1798 * The amount of pressure on anon vs file pages is inversely 1799 * proportional to the fraction of recently scanned pages on 1800 * each list that were recently referenced and in active use. 1801 */ 1802 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1803 ap /= reclaim_stat->recent_rotated[0] + 1; 1804 1805 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1806 fp /= reclaim_stat->recent_rotated[1] + 1; 1807 spin_unlock_irq(&zone->lru_lock); 1808 1809 fraction[0] = ap; 1810 fraction[1] = fp; 1811 denominator = ap + fp + 1; 1812out: 1813 for_each_evictable_lru(l) { 1814 int file = is_file_lru(l); 1815 unsigned long scan; 1816 1817 scan = zone_nr_lru_pages(zone, sc, l); 1818 if (priority || noswap) { 1819 scan >>= priority; 1820 scan = div64_u64(scan * fraction[file], denominator); 1821 } 1822 nr[l] = nr_scan_try_batch(scan, 1823 &reclaim_stat->nr_saved_scan[l]); 1824 } 1825} 1826 1827/* 1828 * Reclaim/compaction depends on a number of pages being freed. To avoid 1829 * disruption to the system, a small number of order-0 pages continue to be 1830 * rotated and reclaimed in the normal fashion. However, by the time we get 1831 * back to the allocator and call try_to_compact_zone(), we ensure that 1832 * there are enough free pages for it to be likely successful 1833 */ 1834static inline bool should_continue_reclaim(struct zone *zone, 1835 unsigned long nr_reclaimed, 1836 unsigned long nr_scanned, 1837 struct scan_control *sc) 1838{ 1839 unsigned long pages_for_compaction; 1840 unsigned long inactive_lru_pages; 1841 1842 /* If not in reclaim/compaction mode, stop */ 1843 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) 1844 return false; 1845 1846 /* Consider stopping depending on scan and reclaim activity */ 1847 if (sc->gfp_mask & __GFP_REPEAT) { 1848 /* 1849 * For __GFP_REPEAT allocations, stop reclaiming if the 1850 * full LRU list has been scanned and we are still failing 1851 * to reclaim pages. This full LRU scan is potentially 1852 * expensive but a __GFP_REPEAT caller really wants to succeed 1853 */ 1854 if (!nr_reclaimed && !nr_scanned) 1855 return false; 1856 } else { 1857 /* 1858 * For non-__GFP_REPEAT allocations which can presumably 1859 * fail without consequence, stop if we failed to reclaim 1860 * any pages from the last SWAP_CLUSTER_MAX number of 1861 * pages that were scanned. This will return to the 1862 * caller faster at the risk reclaim/compaction and 1863 * the resulting allocation attempt fails 1864 */ 1865 if (!nr_reclaimed) 1866 return false; 1867 } 1868 1869 /* 1870 * If we have not reclaimed enough pages for compaction and the 1871 * inactive lists are large enough, continue reclaiming 1872 */ 1873 pages_for_compaction = (2UL << sc->order); 1874 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + 1875 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1876 if (sc->nr_reclaimed < pages_for_compaction && 1877 inactive_lru_pages > pages_for_compaction) 1878 return true; 1879 1880 /* If compaction would go ahead or the allocation would succeed, stop */ 1881 switch (compaction_suitable(zone, sc->order)) { 1882 case COMPACT_PARTIAL: 1883 case COMPACT_CONTINUE: 1884 return false; 1885 default: 1886 return true; 1887 } 1888} 1889 1890/* 1891 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1892 */ 1893static void shrink_zone(int priority, struct zone *zone, 1894 struct scan_control *sc) 1895{ 1896 unsigned long nr[NR_LRU_LISTS]; 1897 unsigned long nr_to_scan; 1898 enum lru_list l; 1899 unsigned long nr_reclaimed, nr_scanned; 1900 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1901 1902restart: 1903 nr_reclaimed = 0; 1904 nr_scanned = sc->nr_scanned; 1905 get_scan_count(zone, sc, nr, priority); 1906 1907 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1908 nr[LRU_INACTIVE_FILE]) { 1909 for_each_evictable_lru(l) { 1910 if (nr[l]) { 1911 nr_to_scan = min_t(unsigned long, 1912 nr[l], SWAP_CLUSTER_MAX); 1913 nr[l] -= nr_to_scan; 1914 1915 nr_reclaimed += shrink_list(l, nr_to_scan, 1916 zone, sc, priority); 1917 } 1918 } 1919 /* 1920 * On large memory systems, scan >> priority can become 1921 * really large. This is fine for the starting priority; 1922 * we want to put equal scanning pressure on each zone. 1923 * However, if the VM has a harder time of freeing pages, 1924 * with multiple processes reclaiming pages, the total 1925 * freeing target can get unreasonably large. 1926 */ 1927 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 1928 break; 1929 } 1930 sc->nr_reclaimed += nr_reclaimed; 1931 1932 /* 1933 * Even if we did not try to evict anon pages at all, we want to 1934 * rebalance the anon lru active/inactive ratio. 1935 */ 1936 if (inactive_anon_is_low(zone, sc)) 1937 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1938 1939 /* reclaim/compaction might need reclaim to continue */ 1940 if (should_continue_reclaim(zone, nr_reclaimed, 1941 sc->nr_scanned - nr_scanned, sc)) 1942 goto restart; 1943 1944 throttle_vm_writeout(sc->gfp_mask); 1945} 1946 1947/* 1948 * This is the direct reclaim path, for page-allocating processes. We only 1949 * try to reclaim pages from zones which will satisfy the caller's allocation 1950 * request. 1951 * 1952 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 1953 * Because: 1954 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1955 * allocation or 1956 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 1957 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 1958 * zone defense algorithm. 1959 * 1960 * If a zone is deemed to be full of pinned pages then just give it a light 1961 * scan then give up on it. 1962 */ 1963static void shrink_zones(int priority, struct zonelist *zonelist, 1964 struct scan_control *sc) 1965{ 1966 struct zoneref *z; 1967 struct zone *zone; 1968 1969 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1970 gfp_zone(sc->gfp_mask), sc->nodemask) { 1971 if (!populated_zone(zone)) 1972 continue; 1973 /* 1974 * Take care memory controller reclaiming has small influence 1975 * to global LRU. 1976 */ 1977 if (scanning_global_lru(sc)) { 1978 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1979 continue; 1980 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1981 continue; /* Let kswapd poll it */ 1982 } 1983 1984 shrink_zone(priority, zone, sc); 1985 } 1986} 1987 1988static bool zone_reclaimable(struct zone *zone) 1989{ 1990 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 1991} 1992 1993/* All zones in zonelist are unreclaimable? */ 1994static bool all_unreclaimable(struct zonelist *zonelist, 1995 struct scan_control *sc) 1996{ 1997 struct zoneref *z; 1998 struct zone *zone; 1999 2000 for_each_zone_zonelist_nodemask(zone, z, zonelist, 2001 gfp_zone(sc->gfp_mask), sc->nodemask) { 2002 if (!populated_zone(zone)) 2003 continue; 2004 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2005 continue; 2006 if (!zone->all_unreclaimable) 2007 return false; 2008 } 2009 2010 return true; 2011} 2012 2013/* 2014 * This is the main entry point to direct page reclaim. 2015 * 2016 * If a full scan of the inactive list fails to free enough memory then we 2017 * are "out of memory" and something needs to be killed. 2018 * 2019 * If the caller is !__GFP_FS then the probability of a failure is reasonably 2020 * high - the zone may be full of dirty or under-writeback pages, which this 2021 * caller can't do much about. We kick the writeback threads and take explicit 2022 * naps in the hope that some of these pages can be written. But if the 2023 * allocating task holds filesystem locks which prevent writeout this might not 2024 * work, and the allocation attempt will fail. 2025 * 2026 * returns: 0, if no pages reclaimed 2027 * else, the number of pages reclaimed 2028 */ 2029static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 2030 struct scan_control *sc) 2031{ 2032 int priority; 2033 unsigned long total_scanned = 0; 2034 struct reclaim_state *reclaim_state = current->reclaim_state; 2035 struct zoneref *z; 2036 struct zone *zone; 2037 unsigned long writeback_threshold; 2038 2039 get_mems_allowed(); 2040 delayacct_freepages_start(); 2041 2042 if (scanning_global_lru(sc)) 2043 count_vm_event(ALLOCSTALL); 2044 2045 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2046 sc->nr_scanned = 0; 2047 if (!priority) 2048 disable_swap_token(); 2049 shrink_zones(priority, zonelist, sc); 2050 /* 2051 * Don't shrink slabs when reclaiming memory from 2052 * over limit cgroups 2053 */ 2054 if (scanning_global_lru(sc)) { 2055 unsigned long lru_pages = 0; 2056 for_each_zone_zonelist(zone, z, zonelist, 2057 gfp_zone(sc->gfp_mask)) { 2058 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2059 continue; 2060 2061 lru_pages += zone_reclaimable_pages(zone); 2062 } 2063 2064 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); 2065 if (reclaim_state) { 2066 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 2067 reclaim_state->reclaimed_slab = 0; 2068 } 2069 } 2070 total_scanned += sc->nr_scanned; 2071 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 2072 goto out; 2073 2074 /* 2075 * Try to write back as many pages as we just scanned. This 2076 * tends to cause slow streaming writers to write data to the 2077 * disk smoothly, at the dirtying rate, which is nice. But 2078 * that's undesirable in laptop mode, where we *want* lumpy 2079 * writeout. So in laptop mode, write out the whole world. 2080 */ 2081 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 2082 if (total_scanned > writeback_threshold) { 2083 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 2084 sc->may_writepage = 1; 2085 } 2086 2087 /* Take a nap, wait for some writeback to complete */ 2088 if (!sc->hibernation_mode && sc->nr_scanned && 2089 priority < DEF_PRIORITY - 2) { 2090 struct zone *preferred_zone; 2091 2092 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), 2093 &cpuset_current_mems_allowed, 2094 &preferred_zone); 2095 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); 2096 } 2097 } 2098 2099out: 2100 delayacct_freepages_end(); 2101 put_mems_allowed(); 2102 2103 if (sc->nr_reclaimed) 2104 return sc->nr_reclaimed; 2105 2106 /* 2107 * As hibernation is going on, kswapd is freezed so that it can't mark 2108 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable 2109 * check. 2110 */ 2111 if (oom_killer_disabled) 2112 return 0; 2113 2114 /* top priority shrink_zones still had more to do? don't OOM, then */ 2115 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 2116 return 1; 2117 2118 return 0; 2119} 2120 2121unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 2122 gfp_t gfp_mask, nodemask_t *nodemask) 2123{ 2124 unsigned long nr_reclaimed; 2125 struct scan_control sc = { 2126 .gfp_mask = gfp_mask, 2127 .may_writepage = !laptop_mode, 2128 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2129 .may_unmap = 1, 2130 .may_swap = 1, 2131 .swappiness = vm_swappiness, 2132 .order = order, 2133 .mem_cgroup = NULL, 2134 .nodemask = nodemask, 2135 }; 2136 2137 trace_mm_vmscan_direct_reclaim_begin(order, 2138 sc.may_writepage, 2139 gfp_mask); 2140 2141 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2142 2143 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2144 2145 return nr_reclaimed; 2146} 2147 2148#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2149 2150unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2151 gfp_t gfp_mask, bool noswap, 2152 unsigned int swappiness, 2153 struct zone *zone) 2154{ 2155 struct scan_control sc = { 2156 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2157 .may_writepage = !laptop_mode, 2158 .may_unmap = 1, 2159 .may_swap = !noswap, 2160 .swappiness = swappiness, 2161 .order = 0, 2162 .mem_cgroup = mem, 2163 }; 2164 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2165 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2166 2167 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2168 sc.may_writepage, 2169 sc.gfp_mask); 2170 2171 /* 2172 * NOTE: Although we can get the priority field, using it 2173 * here is not a good idea, since it limits the pages we can scan. 2174 * if we don't reclaim here, the shrink_zone from balance_pgdat 2175 * will pick up pages from other mem cgroup's as well. We hack 2176 * the priority and make it zero. 2177 */ 2178 shrink_zone(0, zone, &sc); 2179 2180 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2181 2182 return sc.nr_reclaimed; 2183} 2184 2185unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2186 gfp_t gfp_mask, 2187 bool noswap, 2188 unsigned int swappiness) 2189{ 2190 struct zonelist *zonelist; 2191 unsigned long nr_reclaimed; 2192 struct scan_control sc = { 2193 .may_writepage = !laptop_mode, 2194 .may_unmap = 1, 2195 .may_swap = !noswap, 2196 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2197 .swappiness = swappiness, 2198 .order = 0, 2199 .mem_cgroup = mem_cont, 2200 .nodemask = NULL, /* we don't care the placement */ 2201 }; 2202 2203 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2204 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2205 zonelist = NODE_DATA(numa_node_id())->node_zonelists; 2206 2207 trace_mm_vmscan_memcg_reclaim_begin(0, 2208 sc.may_writepage, 2209 sc.gfp_mask); 2210 2211 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2212 2213 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2214 2215 return nr_reclaimed; 2216} 2217#endif 2218 2219/* 2220 * pgdat_balanced is used when checking if a node is balanced for high-order 2221 * allocations. Only zones that meet watermarks and are in a zone allowed 2222 * by the callers classzone_idx are added to balanced_pages. The total of 2223 * balanced pages must be at least 25% of the zones allowed by classzone_idx 2224 * for the node to be considered balanced. Forcing all zones to be balanced 2225 * for high orders can cause excessive reclaim when there are imbalanced zones. 2226 * The choice of 25% is due to 2227 * o a 16M DMA zone that is balanced will not balance a zone on any 2228 * reasonable sized machine 2229 * o On all other machines, the top zone must be at least a reasonable 2230 * percentage of the middle zones. For example, on 32-bit x86, highmem 2231 * would need to be at least 256M for it to be balance a whole node. 2232 * Similarly, on x86-64 the Normal zone would need to be at least 1G 2233 * to balance a node on its own. These seemed like reasonable ratios. 2234 */ 2235static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 2236 int classzone_idx) 2237{ 2238 unsigned long present_pages = 0; 2239 int i; 2240 2241 for (i = 0; i <= classzone_idx; i++) 2242 present_pages += pgdat->node_zones[i].present_pages; 2243 2244 return balanced_pages > (present_pages >> 2); 2245} 2246 2247/* is kswapd sleeping prematurely? */ 2248static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, 2249 int classzone_idx) 2250{ 2251 int i; 2252 unsigned long balanced = 0; 2253 bool all_zones_ok = true; 2254 2255 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2256 if (remaining) 2257 return true; 2258 2259 /* Check the watermark levels */ 2260 for (i = 0; i < pgdat->nr_zones; i++) { 2261 struct zone *zone = pgdat->node_zones + i; 2262 2263 if (!populated_zone(zone)) 2264 continue; 2265 2266 /* 2267 * balance_pgdat() skips over all_unreclaimable after 2268 * DEF_PRIORITY. Effectively, it considers them balanced so 2269 * they must be considered balanced here as well if kswapd 2270 * is to sleep 2271 */ 2272 if (zone->all_unreclaimable) { 2273 balanced += zone->present_pages; 2274 continue; 2275 } 2276 2277 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 2278 classzone_idx, 0)) 2279 all_zones_ok = false; 2280 else 2281 balanced += zone->present_pages; 2282 } 2283 2284 /* 2285 * For high-order requests, the balanced zones must contain at least 2286 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones 2287 * must be balanced 2288 */ 2289 if (order) 2290 return pgdat_balanced(pgdat, balanced, classzone_idx); 2291 else 2292 return !all_zones_ok; 2293} 2294 2295/* 2296 * For kswapd, balance_pgdat() will work across all this node's zones until 2297 * they are all at high_wmark_pages(zone). 2298 * 2299 * Returns the final order kswapd was reclaiming at 2300 * 2301 * There is special handling here for zones which are full of pinned pages. 2302 * This can happen if the pages are all mlocked, or if they are all used by 2303 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2304 * What we do is to detect the case where all pages in the zone have been 2305 * scanned twice and there has been zero successful reclaim. Mark the zone as 2306 * dead and from now on, only perform a short scan. Basically we're polling 2307 * the zone for when the problem goes away. 2308 * 2309 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2310 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2311 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2312 * lower zones regardless of the number of free pages in the lower zones. This 2313 * interoperates with the page allocator fallback scheme to ensure that aging 2314 * of pages is balanced across the zones. 2315 */ 2316static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 2317 int *classzone_idx) 2318{ 2319 int all_zones_ok; 2320 unsigned long balanced; 2321 int priority; 2322 int i; 2323 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2324 unsigned long total_scanned; 2325 struct reclaim_state *reclaim_state = current->reclaim_state; 2326 struct scan_control sc = { 2327 .gfp_mask = GFP_KERNEL, 2328 .may_unmap = 1, 2329 .may_swap = 1, 2330 /* 2331 * kswapd doesn't want to be bailed out while reclaim. because 2332 * we want to put equal scanning pressure on each zone. 2333 */ 2334 .nr_to_reclaim = ULONG_MAX, 2335 .swappiness = vm_swappiness, 2336 .order = order, 2337 .mem_cgroup = NULL, 2338 }; 2339loop_again: 2340 total_scanned = 0; 2341 sc.nr_reclaimed = 0; 2342 sc.may_writepage = !laptop_mode; 2343 count_vm_event(PAGEOUTRUN); 2344 2345 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2346 unsigned long lru_pages = 0; 2347 int has_under_min_watermark_zone = 0; 2348 2349 /* The swap token gets in the way of swapout... */ 2350 if (!priority) 2351 disable_swap_token(); 2352 2353 all_zones_ok = 1; 2354 balanced = 0; 2355 2356 /* 2357 * Scan in the highmem->dma direction for the highest 2358 * zone which needs scanning 2359 */ 2360 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2361 struct zone *zone = pgdat->node_zones + i; 2362 2363 if (!populated_zone(zone)) 2364 continue; 2365 2366 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2367 continue; 2368 2369 /* 2370 * Do some background aging of the anon list, to give 2371 * pages a chance to be referenced before reclaiming. 2372 */ 2373 if (inactive_anon_is_low(zone, &sc)) 2374 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2375 &sc, priority, 0); 2376 2377 if (!zone_watermark_ok_safe(zone, order, 2378 high_wmark_pages(zone), 0, 0)) { 2379 end_zone = i; 2380 *classzone_idx = i; 2381 break; 2382 } 2383 } 2384 if (i < 0) 2385 goto out; 2386 2387 for (i = 0; i <= end_zone; i++) { 2388 struct zone *zone = pgdat->node_zones + i; 2389 2390 lru_pages += zone_reclaimable_pages(zone); 2391 } 2392 2393 /* 2394 * Now scan the zone in the dma->highmem direction, stopping 2395 * at the last zone which needs scanning. 2396 * 2397 * We do this because the page allocator works in the opposite 2398 * direction. This prevents the page allocator from allocating 2399 * pages behind kswapd's direction of progress, which would 2400 * cause too much scanning of the lower zones. 2401 */ 2402 for (i = 0; i <= end_zone; i++) { 2403 struct zone *zone = pgdat->node_zones + i; 2404 int nr_slab; 2405 unsigned long balance_gap; 2406 2407 if (!populated_zone(zone)) 2408 continue; 2409 2410 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2411 continue; 2412 2413 sc.nr_scanned = 0; 2414 2415 /* 2416 * Call soft limit reclaim before calling shrink_zone. 2417 * For now we ignore the return value 2418 */ 2419 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); 2420 2421 /* 2422 * We put equal pressure on every zone, unless 2423 * one zone has way too many pages free 2424 * already. The "too many pages" is defined 2425 * as the high wmark plus a "gap" where the 2426 * gap is either the low watermark or 1% 2427 * of the zone, whichever is smaller. 2428 */ 2429 balance_gap = min(low_wmark_pages(zone), 2430 (zone->present_pages + 2431 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / 2432 KSWAPD_ZONE_BALANCE_GAP_RATIO); 2433 if (!zone_watermark_ok_safe(zone, order, 2434 high_wmark_pages(zone) + balance_gap, 2435 end_zone, 0)) 2436 shrink_zone(priority, zone, &sc); 2437 reclaim_state->reclaimed_slab = 0; 2438 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 2439 lru_pages); 2440 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2441 total_scanned += sc.nr_scanned; 2442 2443 if (zone->all_unreclaimable) 2444 continue; 2445 if (nr_slab == 0 && 2446 !zone_reclaimable(zone)) 2447 zone->all_unreclaimable = 1; 2448 /* 2449 * If we've done a decent amount of scanning and 2450 * the reclaim ratio is low, start doing writepage 2451 * even in laptop mode 2452 */ 2453 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2454 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2455 sc.may_writepage = 1; 2456 2457 if (!zone_watermark_ok_safe(zone, order, 2458 high_wmark_pages(zone), end_zone, 0)) { 2459 all_zones_ok = 0; 2460 /* 2461 * We are still under min water mark. This 2462 * means that we have a GFP_ATOMIC allocation 2463 * failure risk. Hurry up! 2464 */ 2465 if (!zone_watermark_ok_safe(zone, order, 2466 min_wmark_pages(zone), end_zone, 0)) 2467 has_under_min_watermark_zone = 1; 2468 } else { 2469 /* 2470 * If a zone reaches its high watermark, 2471 * consider it to be no longer congested. It's 2472 * possible there are dirty pages backed by 2473 * congested BDIs but as pressure is relieved, 2474 * spectulatively avoid congestion waits 2475 */ 2476 zone_clear_flag(zone, ZONE_CONGESTED); 2477 if (i <= *classzone_idx) 2478 balanced += zone->present_pages; 2479 } 2480 2481 } 2482 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) 2483 break; /* kswapd: all done */ 2484 /* 2485 * OK, kswapd is getting into trouble. Take a nap, then take 2486 * another pass across the zones. 2487 */ 2488 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2489 if (has_under_min_watermark_zone) 2490 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2491 else 2492 congestion_wait(BLK_RW_ASYNC, HZ/10); 2493 } 2494 2495 /* 2496 * We do this so kswapd doesn't build up large priorities for 2497 * example when it is freeing in parallel with allocators. It 2498 * matches the direct reclaim path behaviour in terms of impact 2499 * on zone->*_priority. 2500 */ 2501 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2502 break; 2503 } 2504out: 2505 2506 /* 2507 * order-0: All zones must meet high watermark for a balanced node 2508 * high-order: Balanced zones must make up at least 25% of the node 2509 * for the node to be balanced 2510 */ 2511 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { 2512 cond_resched(); 2513 2514 try_to_freeze(); 2515 2516 /* 2517 * Fragmentation may mean that the system cannot be 2518 * rebalanced for high-order allocations in all zones. 2519 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2520 * it means the zones have been fully scanned and are still 2521 * not balanced. For high-order allocations, there is 2522 * little point trying all over again as kswapd may 2523 * infinite loop. 2524 * 2525 * Instead, recheck all watermarks at order-0 as they 2526 * are the most important. If watermarks are ok, kswapd will go 2527 * back to sleep. High-order users can still perform direct 2528 * reclaim if they wish. 2529 */ 2530 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2531 order = sc.order = 0; 2532 2533 goto loop_again; 2534 } 2535 2536 /* 2537 * If kswapd was reclaiming at a higher order, it has the option of 2538 * sleeping without all zones being balanced. Before it does, it must 2539 * ensure that the watermarks for order-0 on *all* zones are met and 2540 * that the congestion flags are cleared. The congestion flag must 2541 * be cleared as kswapd is the only mechanism that clears the flag 2542 * and it is potentially going to sleep here. 2543 */ 2544 if (order) { 2545 for (i = 0; i <= end_zone; i++) { 2546 struct zone *zone = pgdat->node_zones + i; 2547 2548 if (!populated_zone(zone)) 2549 continue; 2550 2551 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2552 continue; 2553 2554 /* Confirm the zone is balanced for order-0 */ 2555 if (!zone_watermark_ok(zone, 0, 2556 high_wmark_pages(zone), 0, 0)) { 2557 order = sc.order = 0; 2558 goto loop_again; 2559 } 2560 2561 /* If balanced, clear the congested flag */ 2562 zone_clear_flag(zone, ZONE_CONGESTED); 2563 } 2564 } 2565 2566 /* 2567 * Return the order we were reclaiming at so sleeping_prematurely() 2568 * makes a decision on the order we were last reclaiming at. However, 2569 * if another caller entered the allocator slow path while kswapd 2570 * was awake, order will remain at the higher level 2571 */ 2572 *classzone_idx = end_zone; 2573 return order; 2574} 2575 2576static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) 2577{ 2578 long remaining = 0; 2579 DEFINE_WAIT(wait); 2580 2581 if (freezing(current) || kthread_should_stop()) 2582 return; 2583 2584 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2585 2586 /* Try to sleep for a short interval */ 2587 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2588 remaining = schedule_timeout(HZ/10); 2589 finish_wait(&pgdat->kswapd_wait, &wait); 2590 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2591 } 2592 2593 /* 2594 * After a short sleep, check if it was a premature sleep. If not, then 2595 * go fully to sleep until explicitly woken up. 2596 */ 2597 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { 2598 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2599 2600 /* 2601 * vmstat counters are not perfectly accurate and the estimated 2602 * value for counters such as NR_FREE_PAGES can deviate from the 2603 * true value by nr_online_cpus * threshold. To avoid the zone 2604 * watermarks being breached while under pressure, we reduce the 2605 * per-cpu vmstat threshold while kswapd is awake and restore 2606 * them before going back to sleep. 2607 */ 2608 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); 2609 schedule(); 2610 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); 2611 } else { 2612 if (remaining) 2613 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2614 else 2615 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2616 } 2617 finish_wait(&pgdat->kswapd_wait, &wait); 2618} 2619 2620/* 2621 * The background pageout daemon, started as a kernel thread 2622 * from the init process. 2623 * 2624 * This basically trickles out pages so that we have _some_ 2625 * free memory available even if there is no other activity 2626 * that frees anything up. This is needed for things like routing 2627 * etc, where we otherwise might have all activity going on in 2628 * asynchronous contexts that cannot page things out. 2629 * 2630 * If there are applications that are active memory-allocators 2631 * (most normal use), this basically shouldn't matter. 2632 */ 2633static int kswapd(void *p) 2634{ 2635 unsigned long order; 2636 int classzone_idx; 2637 pg_data_t *pgdat = (pg_data_t*)p; 2638 struct task_struct *tsk = current; 2639 2640 struct reclaim_state reclaim_state = { 2641 .reclaimed_slab = 0, 2642 }; 2643 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2644 2645 lockdep_set_current_reclaim_state(GFP_KERNEL); 2646 2647 if (!cpumask_empty(cpumask)) 2648 set_cpus_allowed_ptr(tsk, cpumask); 2649 current->reclaim_state = &reclaim_state; 2650 2651 /* 2652 * Tell the memory management that we're a "memory allocator", 2653 * and that if we need more memory we should get access to it 2654 * regardless (see "__alloc_pages()"). "kswapd" should 2655 * never get caught in the normal page freeing logic. 2656 * 2657 * (Kswapd normally doesn't need memory anyway, but sometimes 2658 * you need a small amount of memory in order to be able to 2659 * page out something else, and this flag essentially protects 2660 * us from recursively trying to free more memory as we're 2661 * trying to free the first piece of memory in the first place). 2662 */ 2663 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2664 set_freezable(); 2665 2666 order = 0; 2667 classzone_idx = MAX_NR_ZONES - 1; 2668 for ( ; ; ) { 2669 unsigned long new_order; 2670 int new_classzone_idx; 2671 int ret; 2672 2673 new_order = pgdat->kswapd_max_order; 2674 new_classzone_idx = pgdat->classzone_idx; 2675 pgdat->kswapd_max_order = 0; 2676 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2677 if (order < new_order || classzone_idx > new_classzone_idx) { 2678 /* 2679 * Don't sleep if someone wants a larger 'order' 2680 * allocation or has tigher zone constraints 2681 */ 2682 order = new_order; 2683 classzone_idx = new_classzone_idx; 2684 } else { 2685 kswapd_try_to_sleep(pgdat, order, classzone_idx); 2686 order = pgdat->kswapd_max_order; 2687 classzone_idx = pgdat->classzone_idx; 2688 pgdat->kswapd_max_order = 0; 2689 pgdat->classzone_idx = MAX_NR_ZONES - 1; 2690 } 2691 2692 ret = try_to_freeze(); 2693 if (kthread_should_stop()) 2694 break; 2695 2696 /* 2697 * We can speed up thawing tasks if we don't call balance_pgdat 2698 * after returning from the refrigerator 2699 */ 2700 if (!ret) { 2701 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2702 order = balance_pgdat(pgdat, order, &classzone_idx); 2703 } 2704 } 2705 return 0; 2706} 2707 2708/* 2709 * A zone is low on free memory, so wake its kswapd task to service it. 2710 */ 2711void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 2712{ 2713 pg_data_t *pgdat; 2714 2715 if (!populated_zone(zone)) 2716 return; 2717 2718 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2719 return; 2720 pgdat = zone->zone_pgdat; 2721 if (pgdat->kswapd_max_order < order) { 2722 pgdat->kswapd_max_order = order; 2723 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); 2724 } 2725 if (!waitqueue_active(&pgdat->kswapd_wait)) 2726 return; 2727 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) 2728 return; 2729 2730 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2731 wake_up_interruptible(&pgdat->kswapd_wait); 2732} 2733 2734/* 2735 * The reclaimable count would be mostly accurate. 2736 * The less reclaimable pages may be 2737 * - mlocked pages, which will be moved to unevictable list when encountered 2738 * - mapped pages, which may require several travels to be reclaimed 2739 * - dirty pages, which is not "instantly" reclaimable 2740 */ 2741unsigned long global_reclaimable_pages(void) 2742{ 2743 int nr; 2744 2745 nr = global_page_state(NR_ACTIVE_FILE) + 2746 global_page_state(NR_INACTIVE_FILE); 2747 2748 if (nr_swap_pages > 0) 2749 nr += global_page_state(NR_ACTIVE_ANON) + 2750 global_page_state(NR_INACTIVE_ANON); 2751 2752 return nr; 2753} 2754 2755unsigned long zone_reclaimable_pages(struct zone *zone) 2756{ 2757 int nr; 2758 2759 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2760 zone_page_state(zone, NR_INACTIVE_FILE); 2761 2762 if (nr_swap_pages > 0) 2763 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2764 zone_page_state(zone, NR_INACTIVE_ANON); 2765 2766 return nr; 2767} 2768 2769#ifdef CONFIG_HIBERNATION 2770/* 2771 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2772 * freed pages. 2773 * 2774 * Rather than trying to age LRUs the aim is to preserve the overall 2775 * LRU order by reclaiming preferentially 2776 * inactive > active > active referenced > active mapped 2777 */ 2778unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2779{ 2780 struct reclaim_state reclaim_state; 2781 struct scan_control sc = { 2782 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2783 .may_swap = 1, 2784 .may_unmap = 1, 2785 .may_writepage = 1, 2786 .nr_to_reclaim = nr_to_reclaim, 2787 .hibernation_mode = 1, 2788 .swappiness = vm_swappiness, 2789 .order = 0, 2790 }; 2791 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2792 struct task_struct *p = current; 2793 unsigned long nr_reclaimed; 2794 2795 p->flags |= PF_MEMALLOC; 2796 lockdep_set_current_reclaim_state(sc.gfp_mask); 2797 reclaim_state.reclaimed_slab = 0; 2798 p->reclaim_state = &reclaim_state; 2799 2800 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2801 2802 p->reclaim_state = NULL; 2803 lockdep_clear_current_reclaim_state(); 2804 p->flags &= ~PF_MEMALLOC; 2805 2806 return nr_reclaimed; 2807} 2808#endif /* CONFIG_HIBERNATION */ 2809 2810/* It's optimal to keep kswapds on the same CPUs as their memory, but 2811 not required for correctness. So if the last cpu in a node goes 2812 away, we get changed to run anywhere: as the first one comes back, 2813 restore their cpu bindings. */ 2814static int __devinit cpu_callback(struct notifier_block *nfb, 2815 unsigned long action, void *hcpu) 2816{ 2817 int nid; 2818 2819 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2820 for_each_node_state(nid, N_HIGH_MEMORY) { 2821 pg_data_t *pgdat = NODE_DATA(nid); 2822 const struct cpumask *mask; 2823 2824 mask = cpumask_of_node(pgdat->node_id); 2825 2826 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2827 /* One of our CPUs online: restore mask */ 2828 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2829 } 2830 } 2831 return NOTIFY_OK; 2832} 2833 2834/* 2835 * This kswapd start function will be called by init and node-hot-add. 2836 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2837 */ 2838int kswapd_run(int nid) 2839{ 2840 pg_data_t *pgdat = NODE_DATA(nid); 2841 int ret = 0; 2842 2843 if (pgdat->kswapd) 2844 return 0; 2845 2846 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2847 if (IS_ERR(pgdat->kswapd)) { 2848 /* failure at boot is fatal */ 2849 BUG_ON(system_state == SYSTEM_BOOTING); 2850 printk("Failed to start kswapd on node %d\n",nid); 2851 ret = -1; 2852 } 2853 return ret; 2854} 2855 2856/* 2857 * Called by memory hotplug when all memory in a node is offlined. 2858 */ 2859void kswapd_stop(int nid) 2860{ 2861 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2862 2863 if (kswapd) 2864 kthread_stop(kswapd); 2865} 2866 2867static int __init kswapd_init(void) 2868{ 2869 int nid; 2870 2871 swap_setup(); 2872 for_each_node_state(nid, N_HIGH_MEMORY) 2873 kswapd_run(nid); 2874 hotcpu_notifier(cpu_callback, 0); 2875 return 0; 2876} 2877 2878module_init(kswapd_init) 2879 2880#ifdef CONFIG_NUMA 2881/* 2882 * Zone reclaim mode 2883 * 2884 * If non-zero call zone_reclaim when the number of free pages falls below 2885 * the watermarks. 2886 */ 2887int zone_reclaim_mode __read_mostly; 2888 2889#define RECLAIM_OFF 0 2890#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2891#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2892#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2893 2894/* 2895 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2896 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2897 * a zone. 2898 */ 2899#define ZONE_RECLAIM_PRIORITY 4 2900 2901/* 2902 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2903 * occur. 2904 */ 2905int sysctl_min_unmapped_ratio = 1; 2906 2907/* 2908 * If the number of slab pages in a zone grows beyond this percentage then 2909 * slab reclaim needs to occur. 2910 */ 2911int sysctl_min_slab_ratio = 5; 2912 2913static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 2914{ 2915 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 2916 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 2917 zone_page_state(zone, NR_ACTIVE_FILE); 2918 2919 /* 2920 * It's possible for there to be more file mapped pages than 2921 * accounted for by the pages on the file LRU lists because 2922 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 2923 */ 2924 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 2925} 2926 2927/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 2928static long zone_pagecache_reclaimable(struct zone *zone) 2929{ 2930 long nr_pagecache_reclaimable; 2931 long delta = 0; 2932 2933 /* 2934 * If RECLAIM_SWAP is set, then all file pages are considered 2935 * potentially reclaimable. Otherwise, we have to worry about 2936 * pages like swapcache and zone_unmapped_file_pages() provides 2937 * a better estimate 2938 */ 2939 if (zone_reclaim_mode & RECLAIM_SWAP) 2940 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 2941 else 2942 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 2943 2944 /* If we can't clean pages, remove dirty pages from consideration */ 2945 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 2946 delta += zone_page_state(zone, NR_FILE_DIRTY); 2947 2948 /* Watch for any possible underflows due to delta */ 2949 if (unlikely(delta > nr_pagecache_reclaimable)) 2950 delta = nr_pagecache_reclaimable; 2951 2952 return nr_pagecache_reclaimable - delta; 2953} 2954 2955/* 2956 * Try to free up some pages from this zone through reclaim. 2957 */ 2958static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2959{ 2960 /* Minimum pages needed in order to stay on node */ 2961 const unsigned long nr_pages = 1 << order; 2962 struct task_struct *p = current; 2963 struct reclaim_state reclaim_state; 2964 int priority; 2965 struct scan_control sc = { 2966 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 2967 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 2968 .may_swap = 1, 2969 .nr_to_reclaim = max_t(unsigned long, nr_pages, 2970 SWAP_CLUSTER_MAX), 2971 .gfp_mask = gfp_mask, 2972 .swappiness = vm_swappiness, 2973 .order = order, 2974 }; 2975 unsigned long nr_slab_pages0, nr_slab_pages1; 2976 2977 cond_resched(); 2978 /* 2979 * We need to be able to allocate from the reserves for RECLAIM_SWAP 2980 * and we also need to be able to write out pages for RECLAIM_WRITE 2981 * and RECLAIM_SWAP. 2982 */ 2983 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 2984 lockdep_set_current_reclaim_state(gfp_mask); 2985 reclaim_state.reclaimed_slab = 0; 2986 p->reclaim_state = &reclaim_state; 2987 2988 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 2989 /* 2990 * Free memory by calling shrink zone with increasing 2991 * priorities until we have enough memory freed. 2992 */ 2993 priority = ZONE_RECLAIM_PRIORITY; 2994 do { 2995 shrink_zone(priority, zone, &sc); 2996 priority--; 2997 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 2998 } 2999 3000 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3001 if (nr_slab_pages0 > zone->min_slab_pages) { 3002 /* 3003 * shrink_slab() does not currently allow us to determine how 3004 * many pages were freed in this zone. So we take the current 3005 * number of slab pages and shake the slab until it is reduced 3006 * by the same nr_pages that we used for reclaiming unmapped 3007 * pages. 3008 * 3009 * Note that shrink_slab will free memory on all zones and may 3010 * take a long time. 3011 */ 3012 for (;;) { 3013 unsigned long lru_pages = zone_reclaimable_pages(zone); 3014 3015 /* No reclaimable slab or very low memory pressure */ 3016 if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) 3017 break; 3018 3019 /* Freed enough memory */ 3020 nr_slab_pages1 = zone_page_state(zone, 3021 NR_SLAB_RECLAIMABLE); 3022 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 3023 break; 3024 } 3025 3026 /* 3027 * Update nr_reclaimed by the number of slab pages we 3028 * reclaimed from this zone. 3029 */ 3030 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 3031 if (nr_slab_pages1 < nr_slab_pages0) 3032 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 3033 } 3034 3035 p->reclaim_state = NULL; 3036 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 3037 lockdep_clear_current_reclaim_state(); 3038 return sc.nr_reclaimed >= nr_pages; 3039} 3040 3041int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 3042{ 3043 int node_id; 3044 int ret; 3045 3046 /* 3047 * Zone reclaim reclaims unmapped file backed pages and 3048 * slab pages if we are over the defined limits. 3049 * 3050 * A small portion of unmapped file backed pages is needed for 3051 * file I/O otherwise pages read by file I/O will be immediately 3052 * thrown out if the zone is overallocated. So we do not reclaim 3053 * if less than a specified percentage of the zone is used by 3054 * unmapped file backed pages. 3055 */ 3056 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 3057 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 3058 return ZONE_RECLAIM_FULL; 3059 3060 if (zone->all_unreclaimable) 3061 return ZONE_RECLAIM_FULL; 3062 3063 /* 3064 * Do not scan if the allocation should not be delayed. 3065 */ 3066 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 3067 return ZONE_RECLAIM_NOSCAN; 3068 3069 /* 3070 * Only run zone reclaim on the local zone or on zones that do not 3071 * have associated processors. This will favor the local processor 3072 * over remote processors and spread off node memory allocations 3073 * as wide as possible. 3074 */ 3075 node_id = zone_to_nid(zone); 3076 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 3077 return ZONE_RECLAIM_NOSCAN; 3078 3079 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 3080 return ZONE_RECLAIM_NOSCAN; 3081 3082 ret = __zone_reclaim(zone, gfp_mask, order); 3083 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 3084 3085 if (!ret) 3086 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 3087 3088 return ret; 3089} 3090#endif 3091 3092/* 3093 * page_evictable - test whether a page is evictable 3094 * @page: the page to test 3095 * @vma: the VMA in which the page is or will be mapped, may be NULL 3096 * 3097 * Test whether page is evictable--i.e., should be placed on active/inactive 3098 * lists vs unevictable list. The vma argument is !NULL when called from the 3099 * fault path to determine how to instantate a new page. 3100 * 3101 * Reasons page might not be evictable: 3102 * (1) page's mapping marked unevictable 3103 * (2) page is part of an mlocked VMA 3104 * 3105 */ 3106int page_evictable(struct page *page, struct vm_area_struct *vma) 3107{ 3108 3109 if (mapping_unevictable(page_mapping(page))) 3110 return 0; 3111 3112 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 3113 return 0; 3114 3115 return 1; 3116} 3117 3118/** 3119 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 3120 * @page: page to check evictability and move to appropriate lru list 3121 * @zone: zone page is in 3122 * 3123 * Checks a page for evictability and moves the page to the appropriate 3124 * zone lru list. 3125 * 3126 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 3127 * have PageUnevictable set. 3128 */ 3129static void check_move_unevictable_page(struct page *page, struct zone *zone) 3130{ 3131 VM_BUG_ON(PageActive(page)); 3132 3133retry: 3134 ClearPageUnevictable(page); 3135 if (page_evictable(page, NULL)) { 3136 enum lru_list l = page_lru_base_type(page); 3137 3138 __dec_zone_state(zone, NR_UNEVICTABLE); 3139 list_move(&page->lru, &zone->lru[l].list); 3140 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 3141 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 3142 __count_vm_event(UNEVICTABLE_PGRESCUED); 3143 } else { 3144 /* 3145 * rotate unevictable list 3146 */ 3147 SetPageUnevictable(page); 3148 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 3149 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 3150 if (page_evictable(page, NULL)) 3151 goto retry; 3152 } 3153} 3154 3155/** 3156 * scan_mapping_unevictable_pages - scan an address space for evictable pages 3157 * @mapping: struct address_space to scan for evictable pages 3158 * 3159 * Scan all pages in mapping. Check unevictable pages for 3160 * evictability and move them to the appropriate zone lru list. 3161 */ 3162void scan_mapping_unevictable_pages(struct address_space *mapping) 3163{ 3164 pgoff_t next = 0; 3165 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 3166 PAGE_CACHE_SHIFT; 3167 struct zone *zone; 3168 struct pagevec pvec; 3169 3170 if (mapping->nrpages == 0) 3171 return; 3172 3173 pagevec_init(&pvec, 0); 3174 while (next < end && 3175 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 3176 int i; 3177 int pg_scanned = 0; 3178 3179 zone = NULL; 3180 3181 for (i = 0; i < pagevec_count(&pvec); i++) { 3182 struct page *page = pvec.pages[i]; 3183 pgoff_t page_index = page->index; 3184 struct zone *pagezone = page_zone(page); 3185 3186 pg_scanned++; 3187 if (page_index > next) 3188 next = page_index; 3189 next++; 3190 3191 if (pagezone != zone) { 3192 if (zone) 3193 spin_unlock_irq(&zone->lru_lock); 3194 zone = pagezone; 3195 spin_lock_irq(&zone->lru_lock); 3196 } 3197 3198 if (PageLRU(page) && PageUnevictable(page)) 3199 check_move_unevictable_page(page, zone); 3200 } 3201 if (zone) 3202 spin_unlock_irq(&zone->lru_lock); 3203 pagevec_release(&pvec); 3204 3205 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 3206 } 3207 3208} 3209 3210/** 3211 * scan_zone_unevictable_pages - check unevictable list for evictable pages 3212 * @zone - zone of which to scan the unevictable list 3213 * 3214 * Scan @zone's unevictable LRU lists to check for pages that have become 3215 * evictable. Move those that have to @zone's inactive list where they 3216 * become candidates for reclaim, unless shrink_inactive_zone() decides 3217 * to reactivate them. Pages that are still unevictable are rotated 3218 * back onto @zone's unevictable list. 3219 */ 3220#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 3221static void scan_zone_unevictable_pages(struct zone *zone) 3222{ 3223 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 3224 unsigned long scan; 3225 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 3226 3227 while (nr_to_scan > 0) { 3228 unsigned long batch_size = min(nr_to_scan, 3229 SCAN_UNEVICTABLE_BATCH_SIZE); 3230 3231 spin_lock_irq(&zone->lru_lock); 3232 for (scan = 0; scan < batch_size; scan++) { 3233 struct page *page = lru_to_page(l_unevictable); 3234 3235 if (!trylock_page(page)) 3236 continue; 3237 3238 prefetchw_prev_lru_page(page, l_unevictable, flags); 3239 3240 if (likely(PageLRU(page) && PageUnevictable(page))) 3241 check_move_unevictable_page(page, zone); 3242 3243 unlock_page(page); 3244 } 3245 spin_unlock_irq(&zone->lru_lock); 3246 3247 nr_to_scan -= batch_size; 3248 } 3249} 3250 3251 3252/** 3253 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 3254 * 3255 * A really big hammer: scan all zones' unevictable LRU lists to check for 3256 * pages that have become evictable. Move those back to the zones' 3257 * inactive list where they become candidates for reclaim. 3258 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 3259 * and we add swap to the system. As such, it runs in the context of a task 3260 * that has possibly/probably made some previously unevictable pages 3261 * evictable. 3262 */ 3263static void scan_all_zones_unevictable_pages(void) 3264{ 3265 struct zone *zone; 3266 3267 for_each_zone(zone) { 3268 scan_zone_unevictable_pages(zone); 3269 } 3270} 3271 3272/* 3273 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 3274 * all nodes' unevictable lists for evictable pages 3275 */ 3276unsigned long scan_unevictable_pages; 3277 3278int scan_unevictable_handler(struct ctl_table *table, int write, 3279 void __user *buffer, 3280 size_t *length, loff_t *ppos) 3281{ 3282 proc_doulongvec_minmax(table, write, buffer, length, ppos); 3283 3284 if (write && *(unsigned long *)table->data) 3285 scan_all_zones_unevictable_pages(); 3286 3287 scan_unevictable_pages = 0; 3288 return 0; 3289} 3290 3291#ifdef CONFIG_NUMA 3292/* 3293 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3294 * a specified node's per zone unevictable lists for evictable pages. 3295 */ 3296 3297static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3298 struct sysdev_attribute *attr, 3299 char *buf) 3300{ 3301 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3302} 3303 3304static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3305 struct sysdev_attribute *attr, 3306 const char *buf, size_t count) 3307{ 3308 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3309 struct zone *zone; 3310 unsigned long res; 3311 unsigned long req = strict_strtoul(buf, 10, &res); 3312 3313 if (!req) 3314 return 1; /* zero is no-op */ 3315 3316 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3317 if (!populated_zone(zone)) 3318 continue; 3319 scan_zone_unevictable_pages(zone); 3320 } 3321 return 1; 3322} 3323 3324 3325static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3326 read_scan_unevictable_node, 3327 write_scan_unevictable_node); 3328 3329int scan_unevictable_register_node(struct node *node) 3330{ 3331 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3332} 3333 3334void scan_unevictable_unregister_node(struct node *node) 3335{ 3336 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3337} 3338#endif 3339