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