vmscan.c revision e11da5b4fdf01d71d73c21cb92b00595b917d7fd
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 continuous memory rather than reclaim 83 * enough amount of memory. i.e, 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 .for_reclaim = 1, 380 }; 381 382 SetPageReclaim(page); 383 res = mapping->a_ops->writepage(page, &wbc); 384 if (res < 0) 385 handle_write_error(mapping, page, res); 386 if (res == AOP_WRITEPAGE_ACTIVATE) { 387 ClearPageReclaim(page); 388 return PAGE_ACTIVATE; 389 } 390 391 /* 392 * Wait on writeback if requested to. This happens when 393 * direct reclaiming a large contiguous area and the 394 * first attempt to free a range of pages fails. 395 */ 396 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC) 397 wait_on_page_writeback(page); 398 399 if (!PageWriteback(page)) { 400 /* synchronous write or broken a_ops? */ 401 ClearPageReclaim(page); 402 } 403 trace_mm_vmscan_writepage(page, 404 trace_reclaim_flags(page, sync_writeback)); 405 inc_zone_page_state(page, NR_VMSCAN_WRITE); 406 return PAGE_SUCCESS; 407 } 408 409 return PAGE_CLEAN; 410} 411 412/* 413 * Same as remove_mapping, but if the page is removed from the mapping, it 414 * gets returned with a refcount of 0. 415 */ 416static int __remove_mapping(struct address_space *mapping, struct page *page) 417{ 418 BUG_ON(!PageLocked(page)); 419 BUG_ON(mapping != page_mapping(page)); 420 421 spin_lock_irq(&mapping->tree_lock); 422 /* 423 * The non racy check for a busy page. 424 * 425 * Must be careful with the order of the tests. When someone has 426 * a ref to the page, it may be possible that they dirty it then 427 * drop the reference. So if PageDirty is tested before page_count 428 * here, then the following race may occur: 429 * 430 * get_user_pages(&page); 431 * [user mapping goes away] 432 * write_to(page); 433 * !PageDirty(page) [good] 434 * SetPageDirty(page); 435 * put_page(page); 436 * !page_count(page) [good, discard it] 437 * 438 * [oops, our write_to data is lost] 439 * 440 * Reversing the order of the tests ensures such a situation cannot 441 * escape unnoticed. The smp_rmb is needed to ensure the page->flags 442 * load is not satisfied before that of page->_count. 443 * 444 * Note that if SetPageDirty is always performed via set_page_dirty, 445 * and thus under tree_lock, then this ordering is not required. 446 */ 447 if (!page_freeze_refs(page, 2)) 448 goto cannot_free; 449 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ 450 if (unlikely(PageDirty(page))) { 451 page_unfreeze_refs(page, 2); 452 goto cannot_free; 453 } 454 455 if (PageSwapCache(page)) { 456 swp_entry_t swap = { .val = page_private(page) }; 457 __delete_from_swap_cache(page); 458 spin_unlock_irq(&mapping->tree_lock); 459 swapcache_free(swap, page); 460 } else { 461 __remove_from_page_cache(page); 462 spin_unlock_irq(&mapping->tree_lock); 463 mem_cgroup_uncharge_cache_page(page); 464 } 465 466 return 1; 467 468cannot_free: 469 spin_unlock_irq(&mapping->tree_lock); 470 return 0; 471} 472 473/* 474 * Attempt to detach a locked page from its ->mapping. If it is dirty or if 475 * someone else has a ref on the page, abort and return 0. If it was 476 * successfully detached, return 1. Assumes the caller has a single ref on 477 * this page. 478 */ 479int remove_mapping(struct address_space *mapping, struct page *page) 480{ 481 if (__remove_mapping(mapping, page)) { 482 /* 483 * Unfreezing the refcount with 1 rather than 2 effectively 484 * drops the pagecache ref for us without requiring another 485 * atomic operation. 486 */ 487 page_unfreeze_refs(page, 1); 488 return 1; 489 } 490 return 0; 491} 492 493/** 494 * putback_lru_page - put previously isolated page onto appropriate LRU list 495 * @page: page to be put back to appropriate lru list 496 * 497 * Add previously isolated @page to appropriate LRU list. 498 * Page may still be unevictable for other reasons. 499 * 500 * lru_lock must not be held, interrupts must be enabled. 501 */ 502void putback_lru_page(struct page *page) 503{ 504 int lru; 505 int active = !!TestClearPageActive(page); 506 int was_unevictable = PageUnevictable(page); 507 508 VM_BUG_ON(PageLRU(page)); 509 510redo: 511 ClearPageUnevictable(page); 512 513 if (page_evictable(page, NULL)) { 514 /* 515 * For evictable pages, we can use the cache. 516 * In event of a race, worst case is we end up with an 517 * unevictable page on [in]active list. 518 * We know how to handle that. 519 */ 520 lru = active + page_lru_base_type(page); 521 lru_cache_add_lru(page, lru); 522 } else { 523 /* 524 * Put unevictable pages directly on zone's unevictable 525 * list. 526 */ 527 lru = LRU_UNEVICTABLE; 528 add_page_to_unevictable_list(page); 529 /* 530 * When racing with an mlock clearing (page is 531 * unlocked), make sure that if the other thread does 532 * not observe our setting of PG_lru and fails 533 * isolation, we see PG_mlocked cleared below and move 534 * the page back to the evictable list. 535 * 536 * The other side is TestClearPageMlocked(). 537 */ 538 smp_mb(); 539 } 540 541 /* 542 * page's status can change while we move it among lru. If an evictable 543 * page is on unevictable list, it never be freed. To avoid that, 544 * check after we added it to the list, again. 545 */ 546 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { 547 if (!isolate_lru_page(page)) { 548 put_page(page); 549 goto redo; 550 } 551 /* This means someone else dropped this page from LRU 552 * So, it will be freed or putback to LRU again. There is 553 * nothing to do here. 554 */ 555 } 556 557 if (was_unevictable && lru != LRU_UNEVICTABLE) 558 count_vm_event(UNEVICTABLE_PGRESCUED); 559 else if (!was_unevictable && lru == LRU_UNEVICTABLE) 560 count_vm_event(UNEVICTABLE_PGCULLED); 561 562 put_page(page); /* drop ref from isolate */ 563} 564 565enum page_references { 566 PAGEREF_RECLAIM, 567 PAGEREF_RECLAIM_CLEAN, 568 PAGEREF_KEEP, 569 PAGEREF_ACTIVATE, 570}; 571 572static enum page_references page_check_references(struct page *page, 573 struct scan_control *sc) 574{ 575 int referenced_ptes, referenced_page; 576 unsigned long vm_flags; 577 578 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); 579 referenced_page = TestClearPageReferenced(page); 580 581 /* Lumpy reclaim - ignore references */ 582 if (sc->lumpy_reclaim_mode) 583 return PAGEREF_RECLAIM; 584 585 /* 586 * Mlock lost the isolation race with us. Let try_to_unmap() 587 * move the page to the unevictable list. 588 */ 589 if (vm_flags & VM_LOCKED) 590 return PAGEREF_RECLAIM; 591 592 if (referenced_ptes) { 593 if (PageAnon(page)) 594 return PAGEREF_ACTIVATE; 595 /* 596 * All mapped pages start out with page table 597 * references from the instantiating fault, so we need 598 * to look twice if a mapped file page is used more 599 * than once. 600 * 601 * Mark it and spare it for another trip around the 602 * inactive list. Another page table reference will 603 * lead to its activation. 604 * 605 * Note: the mark is set for activated pages as well 606 * so that recently deactivated but used pages are 607 * quickly recovered. 608 */ 609 SetPageReferenced(page); 610 611 if (referenced_page) 612 return PAGEREF_ACTIVATE; 613 614 return PAGEREF_KEEP; 615 } 616 617 /* Reclaim if clean, defer dirty pages to writeback */ 618 if (referenced_page) 619 return PAGEREF_RECLAIM_CLEAN; 620 621 return PAGEREF_RECLAIM; 622} 623 624static noinline_for_stack void free_page_list(struct list_head *free_pages) 625{ 626 struct pagevec freed_pvec; 627 struct page *page, *tmp; 628 629 pagevec_init(&freed_pvec, 1); 630 631 list_for_each_entry_safe(page, tmp, free_pages, lru) { 632 list_del(&page->lru); 633 if (!pagevec_add(&freed_pvec, page)) { 634 __pagevec_free(&freed_pvec); 635 pagevec_reinit(&freed_pvec); 636 } 637 } 638 639 pagevec_free(&freed_pvec); 640} 641 642/* 643 * shrink_page_list() returns the number of reclaimed pages 644 */ 645static unsigned long shrink_page_list(struct list_head *page_list, 646 struct scan_control *sc, 647 enum pageout_io sync_writeback) 648{ 649 LIST_HEAD(ret_pages); 650 LIST_HEAD(free_pages); 651 int pgactivate = 0; 652 unsigned long nr_reclaimed = 0; 653 654 cond_resched(); 655 656 while (!list_empty(page_list)) { 657 enum page_references references; 658 struct address_space *mapping; 659 struct page *page; 660 int may_enter_fs; 661 662 cond_resched(); 663 664 page = lru_to_page(page_list); 665 list_del(&page->lru); 666 667 if (!trylock_page(page)) 668 goto keep; 669 670 VM_BUG_ON(PageActive(page)); 671 672 sc->nr_scanned++; 673 674 if (unlikely(!page_evictable(page, NULL))) 675 goto cull_mlocked; 676 677 if (!sc->may_unmap && page_mapped(page)) 678 goto keep_locked; 679 680 /* Double the slab pressure for mapped and swapcache pages */ 681 if (page_mapped(page) || PageSwapCache(page)) 682 sc->nr_scanned++; 683 684 may_enter_fs = (sc->gfp_mask & __GFP_FS) || 685 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); 686 687 if (PageWriteback(page)) { 688 /* 689 * Synchronous reclaim is performed in two passes, 690 * first an asynchronous pass over the list to 691 * start parallel writeback, and a second synchronous 692 * pass to wait for the IO to complete. Wait here 693 * for any page for which writeback has already 694 * started. 695 */ 696 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) 697 wait_on_page_writeback(page); 698 else 699 goto keep_locked; 700 } 701 702 references = page_check_references(page, sc); 703 switch (references) { 704 case PAGEREF_ACTIVATE: 705 goto activate_locked; 706 case PAGEREF_KEEP: 707 goto keep_locked; 708 case PAGEREF_RECLAIM: 709 case PAGEREF_RECLAIM_CLEAN: 710 ; /* try to reclaim the page below */ 711 } 712 713 /* 714 * Anonymous process memory has backing store? 715 * Try to allocate it some swap space here. 716 */ 717 if (PageAnon(page) && !PageSwapCache(page)) { 718 if (!(sc->gfp_mask & __GFP_IO)) 719 goto keep_locked; 720 if (!add_to_swap(page)) 721 goto activate_locked; 722 may_enter_fs = 1; 723 } 724 725 mapping = page_mapping(page); 726 727 /* 728 * The page is mapped into the page tables of one or more 729 * processes. Try to unmap it here. 730 */ 731 if (page_mapped(page) && mapping) { 732 switch (try_to_unmap(page, TTU_UNMAP)) { 733 case SWAP_FAIL: 734 goto activate_locked; 735 case SWAP_AGAIN: 736 goto keep_locked; 737 case SWAP_MLOCK: 738 goto cull_mlocked; 739 case SWAP_SUCCESS: 740 ; /* try to free the page below */ 741 } 742 } 743 744 if (PageDirty(page)) { 745 if (references == PAGEREF_RECLAIM_CLEAN) 746 goto keep_locked; 747 if (!may_enter_fs) 748 goto keep_locked; 749 if (!sc->may_writepage) 750 goto keep_locked; 751 752 /* Page is dirty, try to write it out here */ 753 switch (pageout(page, mapping, sync_writeback)) { 754 case PAGE_KEEP: 755 goto keep_locked; 756 case PAGE_ACTIVATE: 757 goto activate_locked; 758 case PAGE_SUCCESS: 759 if (PageWriteback(page) || PageDirty(page)) 760 goto keep; 761 /* 762 * A synchronous write - probably a ramdisk. Go 763 * ahead and try to reclaim the page. 764 */ 765 if (!trylock_page(page)) 766 goto keep; 767 if (PageDirty(page) || PageWriteback(page)) 768 goto keep_locked; 769 mapping = page_mapping(page); 770 case PAGE_CLEAN: 771 ; /* try to free the page below */ 772 } 773 } 774 775 /* 776 * If the page has buffers, try to free the buffer mappings 777 * associated with this page. If we succeed we try to free 778 * the page as well. 779 * 780 * We do this even if the page is PageDirty(). 781 * try_to_release_page() does not perform I/O, but it is 782 * possible for a page to have PageDirty set, but it is actually 783 * clean (all its buffers are clean). This happens if the 784 * buffers were written out directly, with submit_bh(). ext3 785 * will do this, as well as the blockdev mapping. 786 * try_to_release_page() will discover that cleanness and will 787 * drop the buffers and mark the page clean - it can be freed. 788 * 789 * Rarely, pages can have buffers and no ->mapping. These are 790 * the pages which were not successfully invalidated in 791 * truncate_complete_page(). We try to drop those buffers here 792 * and if that worked, and the page is no longer mapped into 793 * process address space (page_count == 1) it can be freed. 794 * Otherwise, leave the page on the LRU so it is swappable. 795 */ 796 if (page_has_private(page)) { 797 if (!try_to_release_page(page, sc->gfp_mask)) 798 goto activate_locked; 799 if (!mapping && page_count(page) == 1) { 800 unlock_page(page); 801 if (put_page_testzero(page)) 802 goto free_it; 803 else { 804 /* 805 * rare race with speculative reference. 806 * the speculative reference will free 807 * this page shortly, so we may 808 * increment nr_reclaimed here (and 809 * leave it off the LRU). 810 */ 811 nr_reclaimed++; 812 continue; 813 } 814 } 815 } 816 817 if (!mapping || !__remove_mapping(mapping, page)) 818 goto keep_locked; 819 820 /* 821 * At this point, we have no other references and there is 822 * no way to pick any more up (removed from LRU, removed 823 * from pagecache). Can use non-atomic bitops now (and 824 * we obviously don't have to worry about waking up a process 825 * waiting on the page lock, because there are no references. 826 */ 827 __clear_page_locked(page); 828free_it: 829 nr_reclaimed++; 830 831 /* 832 * Is there need to periodically free_page_list? It would 833 * appear not as the counts should be low 834 */ 835 list_add(&page->lru, &free_pages); 836 continue; 837 838cull_mlocked: 839 if (PageSwapCache(page)) 840 try_to_free_swap(page); 841 unlock_page(page); 842 putback_lru_page(page); 843 continue; 844 845activate_locked: 846 /* Not a candidate for swapping, so reclaim swap space. */ 847 if (PageSwapCache(page) && vm_swap_full()) 848 try_to_free_swap(page); 849 VM_BUG_ON(PageActive(page)); 850 SetPageActive(page); 851 pgactivate++; 852keep_locked: 853 unlock_page(page); 854keep: 855 list_add(&page->lru, &ret_pages); 856 VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); 857 } 858 859 free_page_list(&free_pages); 860 861 list_splice(&ret_pages, page_list); 862 count_vm_events(PGACTIVATE, pgactivate); 863 return nr_reclaimed; 864} 865 866/* 867 * Attempt to remove the specified page from its LRU. Only take this page 868 * if it is of the appropriate PageActive status. Pages which are being 869 * freed elsewhere are also ignored. 870 * 871 * page: page to consider 872 * mode: one of the LRU isolation modes defined above 873 * 874 * returns 0 on success, -ve errno on failure. 875 */ 876int __isolate_lru_page(struct page *page, int mode, int file) 877{ 878 int ret = -EINVAL; 879 880 /* Only take pages on the LRU. */ 881 if (!PageLRU(page)) 882 return ret; 883 884 /* 885 * When checking the active state, we need to be sure we are 886 * dealing with comparible boolean values. Take the logical not 887 * of each. 888 */ 889 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) 890 return ret; 891 892 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) 893 return ret; 894 895 /* 896 * When this function is being called for lumpy reclaim, we 897 * initially look into all LRU pages, active, inactive and 898 * unevictable; only give shrink_page_list evictable pages. 899 */ 900 if (PageUnevictable(page)) 901 return ret; 902 903 ret = -EBUSY; 904 905 if (likely(get_page_unless_zero(page))) { 906 /* 907 * Be careful not to clear PageLRU until after we're 908 * sure the page is not being freed elsewhere -- the 909 * page release code relies on it. 910 */ 911 ClearPageLRU(page); 912 ret = 0; 913 } 914 915 return ret; 916} 917 918/* 919 * zone->lru_lock is heavily contended. Some of the functions that 920 * shrink the lists perform better by taking out a batch of pages 921 * and working on them outside the LRU lock. 922 * 923 * For pagecache intensive workloads, this function is the hottest 924 * spot in the kernel (apart from copy_*_user functions). 925 * 926 * Appropriate locks must be held before calling this function. 927 * 928 * @nr_to_scan: The number of pages to look through on the list. 929 * @src: The LRU list to pull pages off. 930 * @dst: The temp list to put pages on to. 931 * @scanned: The number of pages that were scanned. 932 * @order: The caller's attempted allocation order 933 * @mode: One of the LRU isolation modes 934 * @file: True [1] if isolating file [!anon] pages 935 * 936 * returns how many pages were moved onto *@dst. 937 */ 938static unsigned long isolate_lru_pages(unsigned long nr_to_scan, 939 struct list_head *src, struct list_head *dst, 940 unsigned long *scanned, int order, int mode, int file) 941{ 942 unsigned long nr_taken = 0; 943 unsigned long nr_lumpy_taken = 0; 944 unsigned long nr_lumpy_dirty = 0; 945 unsigned long nr_lumpy_failed = 0; 946 unsigned long scan; 947 948 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { 949 struct page *page; 950 unsigned long pfn; 951 unsigned long end_pfn; 952 unsigned long page_pfn; 953 int zone_id; 954 955 page = lru_to_page(src); 956 prefetchw_prev_lru_page(page, src, flags); 957 958 VM_BUG_ON(!PageLRU(page)); 959 960 switch (__isolate_lru_page(page, mode, file)) { 961 case 0: 962 list_move(&page->lru, dst); 963 mem_cgroup_del_lru(page); 964 nr_taken++; 965 break; 966 967 case -EBUSY: 968 /* else it is being freed elsewhere */ 969 list_move(&page->lru, src); 970 mem_cgroup_rotate_lru_list(page, page_lru(page)); 971 continue; 972 973 default: 974 BUG(); 975 } 976 977 if (!order) 978 continue; 979 980 /* 981 * Attempt to take all pages in the order aligned region 982 * surrounding the tag page. Only take those pages of 983 * the same active state as that tag page. We may safely 984 * round the target page pfn down to the requested order 985 * as the mem_map is guarenteed valid out to MAX_ORDER, 986 * where that page is in a different zone we will detect 987 * it from its zone id and abort this block scan. 988 */ 989 zone_id = page_zone_id(page); 990 page_pfn = page_to_pfn(page); 991 pfn = page_pfn & ~((1 << order) - 1); 992 end_pfn = pfn + (1 << order); 993 for (; pfn < end_pfn; pfn++) { 994 struct page *cursor_page; 995 996 /* The target page is in the block, ignore it. */ 997 if (unlikely(pfn == page_pfn)) 998 continue; 999 1000 /* Avoid holes within the zone. */ 1001 if (unlikely(!pfn_valid_within(pfn))) 1002 break; 1003 1004 cursor_page = pfn_to_page(pfn); 1005 1006 /* Check that we have not crossed a zone boundary. */ 1007 if (unlikely(page_zone_id(cursor_page) != zone_id)) 1008 continue; 1009 1010 /* 1011 * If we don't have enough swap space, reclaiming of 1012 * anon page which don't already have a swap slot is 1013 * pointless. 1014 */ 1015 if (nr_swap_pages <= 0 && PageAnon(cursor_page) && 1016 !PageSwapCache(cursor_page)) 1017 continue; 1018 1019 if (__isolate_lru_page(cursor_page, mode, file) == 0) { 1020 list_move(&cursor_page->lru, dst); 1021 mem_cgroup_del_lru(cursor_page); 1022 nr_taken++; 1023 nr_lumpy_taken++; 1024 if (PageDirty(cursor_page)) 1025 nr_lumpy_dirty++; 1026 scan++; 1027 } else { 1028 if (mode == ISOLATE_BOTH && 1029 page_count(cursor_page)) 1030 nr_lumpy_failed++; 1031 } 1032 } 1033 } 1034 1035 *scanned = scan; 1036 1037 trace_mm_vmscan_lru_isolate(order, 1038 nr_to_scan, scan, 1039 nr_taken, 1040 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, 1041 mode); 1042 return nr_taken; 1043} 1044 1045static unsigned long isolate_pages_global(unsigned long nr, 1046 struct list_head *dst, 1047 unsigned long *scanned, int order, 1048 int mode, struct zone *z, 1049 int active, int file) 1050{ 1051 int lru = LRU_BASE; 1052 if (active) 1053 lru += LRU_ACTIVE; 1054 if (file) 1055 lru += LRU_FILE; 1056 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, 1057 mode, file); 1058} 1059 1060/* 1061 * clear_active_flags() is a helper for shrink_active_list(), clearing 1062 * any active bits from the pages in the list. 1063 */ 1064static unsigned long clear_active_flags(struct list_head *page_list, 1065 unsigned int *count) 1066{ 1067 int nr_active = 0; 1068 int lru; 1069 struct page *page; 1070 1071 list_for_each_entry(page, page_list, lru) { 1072 lru = page_lru_base_type(page); 1073 if (PageActive(page)) { 1074 lru += LRU_ACTIVE; 1075 ClearPageActive(page); 1076 nr_active++; 1077 } 1078 if (count) 1079 count[lru]++; 1080 } 1081 1082 return nr_active; 1083} 1084 1085/** 1086 * isolate_lru_page - tries to isolate a page from its LRU list 1087 * @page: page to isolate from its LRU list 1088 * 1089 * Isolates a @page from an LRU list, clears PageLRU and adjusts the 1090 * vmstat statistic corresponding to whatever LRU list the page was on. 1091 * 1092 * Returns 0 if the page was removed from an LRU list. 1093 * Returns -EBUSY if the page was not on an LRU list. 1094 * 1095 * The returned page will have PageLRU() cleared. If it was found on 1096 * the active list, it will have PageActive set. If it was found on 1097 * the unevictable list, it will have the PageUnevictable bit set. That flag 1098 * may need to be cleared by the caller before letting the page go. 1099 * 1100 * The vmstat statistic corresponding to the list on which the page was 1101 * found will be decremented. 1102 * 1103 * Restrictions: 1104 * (1) Must be called with an elevated refcount on the page. This is a 1105 * fundamentnal difference from isolate_lru_pages (which is called 1106 * without a stable reference). 1107 * (2) the lru_lock must not be held. 1108 * (3) interrupts must be enabled. 1109 */ 1110int isolate_lru_page(struct page *page) 1111{ 1112 int ret = -EBUSY; 1113 1114 if (PageLRU(page)) { 1115 struct zone *zone = page_zone(page); 1116 1117 spin_lock_irq(&zone->lru_lock); 1118 if (PageLRU(page) && get_page_unless_zero(page)) { 1119 int lru = page_lru(page); 1120 ret = 0; 1121 ClearPageLRU(page); 1122 1123 del_page_from_lru_list(zone, page, lru); 1124 } 1125 spin_unlock_irq(&zone->lru_lock); 1126 } 1127 return ret; 1128} 1129 1130/* 1131 * Are there way too many processes in the direct reclaim path already? 1132 */ 1133static int too_many_isolated(struct zone *zone, int file, 1134 struct scan_control *sc) 1135{ 1136 unsigned long inactive, isolated; 1137 1138 if (current_is_kswapd()) 1139 return 0; 1140 1141 if (!scanning_global_lru(sc)) 1142 return 0; 1143 1144 if (file) { 1145 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1146 isolated = zone_page_state(zone, NR_ISOLATED_FILE); 1147 } else { 1148 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1149 isolated = zone_page_state(zone, NR_ISOLATED_ANON); 1150 } 1151 1152 return isolated > inactive; 1153} 1154 1155/* 1156 * TODO: Try merging with migrations version of putback_lru_pages 1157 */ 1158static noinline_for_stack void 1159putback_lru_pages(struct zone *zone, struct scan_control *sc, 1160 unsigned long nr_anon, unsigned long nr_file, 1161 struct list_head *page_list) 1162{ 1163 struct page *page; 1164 struct pagevec pvec; 1165 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1166 1167 pagevec_init(&pvec, 1); 1168 1169 /* 1170 * Put back any unfreeable pages. 1171 */ 1172 spin_lock(&zone->lru_lock); 1173 while (!list_empty(page_list)) { 1174 int lru; 1175 page = lru_to_page(page_list); 1176 VM_BUG_ON(PageLRU(page)); 1177 list_del(&page->lru); 1178 if (unlikely(!page_evictable(page, NULL))) { 1179 spin_unlock_irq(&zone->lru_lock); 1180 putback_lru_page(page); 1181 spin_lock_irq(&zone->lru_lock); 1182 continue; 1183 } 1184 SetPageLRU(page); 1185 lru = page_lru(page); 1186 add_page_to_lru_list(zone, page, lru); 1187 if (is_active_lru(lru)) { 1188 int file = is_file_lru(lru); 1189 reclaim_stat->recent_rotated[file]++; 1190 } 1191 if (!pagevec_add(&pvec, page)) { 1192 spin_unlock_irq(&zone->lru_lock); 1193 __pagevec_release(&pvec); 1194 spin_lock_irq(&zone->lru_lock); 1195 } 1196 } 1197 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); 1198 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); 1199 1200 spin_unlock_irq(&zone->lru_lock); 1201 pagevec_release(&pvec); 1202} 1203 1204static noinline_for_stack void update_isolated_counts(struct zone *zone, 1205 struct scan_control *sc, 1206 unsigned long *nr_anon, 1207 unsigned long *nr_file, 1208 struct list_head *isolated_list) 1209{ 1210 unsigned long nr_active; 1211 unsigned int count[NR_LRU_LISTS] = { 0, }; 1212 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1213 1214 nr_active = clear_active_flags(isolated_list, count); 1215 __count_vm_events(PGDEACTIVATE, nr_active); 1216 1217 __mod_zone_page_state(zone, NR_ACTIVE_FILE, 1218 -count[LRU_ACTIVE_FILE]); 1219 __mod_zone_page_state(zone, NR_INACTIVE_FILE, 1220 -count[LRU_INACTIVE_FILE]); 1221 __mod_zone_page_state(zone, NR_ACTIVE_ANON, 1222 -count[LRU_ACTIVE_ANON]); 1223 __mod_zone_page_state(zone, NR_INACTIVE_ANON, 1224 -count[LRU_INACTIVE_ANON]); 1225 1226 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; 1227 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; 1228 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); 1229 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); 1230 1231 reclaim_stat->recent_scanned[0] += *nr_anon; 1232 reclaim_stat->recent_scanned[1] += *nr_file; 1233} 1234 1235/* 1236 * Returns true if the caller should wait to clean dirty/writeback pages. 1237 * 1238 * If we are direct reclaiming for contiguous pages and we do not reclaim 1239 * everything in the list, try again and wait for writeback IO to complete. 1240 * This will stall high-order allocations noticeably. Only do that when really 1241 * need to free the pages under high memory pressure. 1242 */ 1243static inline bool should_reclaim_stall(unsigned long nr_taken, 1244 unsigned long nr_freed, 1245 int priority, 1246 struct scan_control *sc) 1247{ 1248 int lumpy_stall_priority; 1249 1250 /* kswapd should not stall on sync IO */ 1251 if (current_is_kswapd()) 1252 return false; 1253 1254 /* Only stall on lumpy reclaim */ 1255 if (!sc->lumpy_reclaim_mode) 1256 return false; 1257 1258 /* If we have relaimed everything on the isolated list, no stall */ 1259 if (nr_freed == nr_taken) 1260 return false; 1261 1262 /* 1263 * For high-order allocations, there are two stall thresholds. 1264 * High-cost allocations stall immediately where as lower 1265 * order allocations such as stacks require the scanning 1266 * priority to be much higher before stalling. 1267 */ 1268 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1269 lumpy_stall_priority = DEF_PRIORITY; 1270 else 1271 lumpy_stall_priority = DEF_PRIORITY / 3; 1272 1273 return priority <= lumpy_stall_priority; 1274} 1275 1276/* 1277 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number 1278 * of reclaimed pages 1279 */ 1280static noinline_for_stack unsigned long 1281shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, 1282 struct scan_control *sc, int priority, int file) 1283{ 1284 LIST_HEAD(page_list); 1285 unsigned long nr_scanned; 1286 unsigned long nr_reclaimed = 0; 1287 unsigned long nr_taken; 1288 unsigned long nr_active; 1289 unsigned long nr_anon; 1290 unsigned long nr_file; 1291 1292 while (unlikely(too_many_isolated(zone, file, sc))) { 1293 congestion_wait(BLK_RW_ASYNC, HZ/10); 1294 1295 /* We are about to die and free our memory. Return now. */ 1296 if (fatal_signal_pending(current)) 1297 return SWAP_CLUSTER_MAX; 1298 } 1299 1300 1301 lru_add_drain(); 1302 spin_lock_irq(&zone->lru_lock); 1303 1304 if (scanning_global_lru(sc)) { 1305 nr_taken = isolate_pages_global(nr_to_scan, 1306 &page_list, &nr_scanned, sc->order, 1307 sc->lumpy_reclaim_mode ? 1308 ISOLATE_BOTH : ISOLATE_INACTIVE, 1309 zone, 0, file); 1310 zone->pages_scanned += nr_scanned; 1311 if (current_is_kswapd()) 1312 __count_zone_vm_events(PGSCAN_KSWAPD, zone, 1313 nr_scanned); 1314 else 1315 __count_zone_vm_events(PGSCAN_DIRECT, zone, 1316 nr_scanned); 1317 } else { 1318 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, 1319 &page_list, &nr_scanned, sc->order, 1320 sc->lumpy_reclaim_mode ? 1321 ISOLATE_BOTH : ISOLATE_INACTIVE, 1322 zone, sc->mem_cgroup, 1323 0, file); 1324 /* 1325 * mem_cgroup_isolate_pages() keeps track of 1326 * scanned pages on its own. 1327 */ 1328 } 1329 1330 if (nr_taken == 0) { 1331 spin_unlock_irq(&zone->lru_lock); 1332 return 0; 1333 } 1334 1335 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); 1336 1337 spin_unlock_irq(&zone->lru_lock); 1338 1339 nr_reclaimed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); 1340 1341 /* Check if we should syncronously wait for writeback */ 1342 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { 1343 congestion_wait(BLK_RW_ASYNC, HZ/10); 1344 1345 /* 1346 * The attempt at page out may have made some 1347 * of the pages active, mark them inactive again. 1348 */ 1349 nr_active = clear_active_flags(&page_list, NULL); 1350 count_vm_events(PGDEACTIVATE, nr_active); 1351 1352 nr_reclaimed += shrink_page_list(&page_list, sc, PAGEOUT_IO_SYNC); 1353 } 1354 1355 local_irq_disable(); 1356 if (current_is_kswapd()) 1357 __count_vm_events(KSWAPD_STEAL, nr_reclaimed); 1358 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); 1359 1360 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); 1361 1362 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, 1363 zone_idx(zone), 1364 nr_scanned, nr_reclaimed, 1365 priority, 1366 trace_shrink_flags(file, sc->lumpy_reclaim_mode)); 1367 return nr_reclaimed; 1368} 1369 1370/* 1371 * This moves pages from the active list to the inactive list. 1372 * 1373 * We move them the other way if the page is referenced by one or more 1374 * processes, from rmap. 1375 * 1376 * If the pages are mostly unmapped, the processing is fast and it is 1377 * appropriate to hold zone->lru_lock across the whole operation. But if 1378 * the pages are mapped, the processing is slow (page_referenced()) so we 1379 * should drop zone->lru_lock around each page. It's impossible to balance 1380 * this, so instead we remove the pages from the LRU while processing them. 1381 * It is safe to rely on PG_active against the non-LRU pages in here because 1382 * nobody will play with that bit on a non-LRU page. 1383 * 1384 * The downside is that we have to touch page->_count against each page. 1385 * But we had to alter page->flags anyway. 1386 */ 1387 1388static void move_active_pages_to_lru(struct zone *zone, 1389 struct list_head *list, 1390 enum lru_list lru) 1391{ 1392 unsigned long pgmoved = 0; 1393 struct pagevec pvec; 1394 struct page *page; 1395 1396 pagevec_init(&pvec, 1); 1397 1398 while (!list_empty(list)) { 1399 page = lru_to_page(list); 1400 1401 VM_BUG_ON(PageLRU(page)); 1402 SetPageLRU(page); 1403 1404 list_move(&page->lru, &zone->lru[lru].list); 1405 mem_cgroup_add_lru_list(page, lru); 1406 pgmoved++; 1407 1408 if (!pagevec_add(&pvec, page) || list_empty(list)) { 1409 spin_unlock_irq(&zone->lru_lock); 1410 if (buffer_heads_over_limit) 1411 pagevec_strip(&pvec); 1412 __pagevec_release(&pvec); 1413 spin_lock_irq(&zone->lru_lock); 1414 } 1415 } 1416 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); 1417 if (!is_active_lru(lru)) 1418 __count_vm_events(PGDEACTIVATE, pgmoved); 1419} 1420 1421static void shrink_active_list(unsigned long nr_pages, struct zone *zone, 1422 struct scan_control *sc, int priority, int file) 1423{ 1424 unsigned long nr_taken; 1425 unsigned long pgscanned; 1426 unsigned long vm_flags; 1427 LIST_HEAD(l_hold); /* The pages which were snipped off */ 1428 LIST_HEAD(l_active); 1429 LIST_HEAD(l_inactive); 1430 struct page *page; 1431 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1432 unsigned long nr_rotated = 0; 1433 1434 lru_add_drain(); 1435 spin_lock_irq(&zone->lru_lock); 1436 if (scanning_global_lru(sc)) { 1437 nr_taken = isolate_pages_global(nr_pages, &l_hold, 1438 &pgscanned, sc->order, 1439 ISOLATE_ACTIVE, zone, 1440 1, file); 1441 zone->pages_scanned += pgscanned; 1442 } else { 1443 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, 1444 &pgscanned, sc->order, 1445 ISOLATE_ACTIVE, zone, 1446 sc->mem_cgroup, 1, file); 1447 /* 1448 * mem_cgroup_isolate_pages() keeps track of 1449 * scanned pages on its own. 1450 */ 1451 } 1452 1453 reclaim_stat->recent_scanned[file] += nr_taken; 1454 1455 __count_zone_vm_events(PGREFILL, zone, pgscanned); 1456 if (file) 1457 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); 1458 else 1459 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); 1460 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); 1461 spin_unlock_irq(&zone->lru_lock); 1462 1463 while (!list_empty(&l_hold)) { 1464 cond_resched(); 1465 page = lru_to_page(&l_hold); 1466 list_del(&page->lru); 1467 1468 if (unlikely(!page_evictable(page, NULL))) { 1469 putback_lru_page(page); 1470 continue; 1471 } 1472 1473 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { 1474 nr_rotated++; 1475 /* 1476 * Identify referenced, file-backed active pages and 1477 * give them one more trip around the active list. So 1478 * that executable code get better chances to stay in 1479 * memory under moderate memory pressure. Anon pages 1480 * are not likely to be evicted by use-once streaming 1481 * IO, plus JVM can create lots of anon VM_EXEC pages, 1482 * so we ignore them here. 1483 */ 1484 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { 1485 list_add(&page->lru, &l_active); 1486 continue; 1487 } 1488 } 1489 1490 ClearPageActive(page); /* we are de-activating */ 1491 list_add(&page->lru, &l_inactive); 1492 } 1493 1494 /* 1495 * Move pages back to the lru list. 1496 */ 1497 spin_lock_irq(&zone->lru_lock); 1498 /* 1499 * Count referenced pages from currently used mappings as rotated, 1500 * even though only some of them are actually re-activated. This 1501 * helps balance scan pressure between file and anonymous pages in 1502 * get_scan_ratio. 1503 */ 1504 reclaim_stat->recent_rotated[file] += nr_rotated; 1505 1506 move_active_pages_to_lru(zone, &l_active, 1507 LRU_ACTIVE + file * LRU_FILE); 1508 move_active_pages_to_lru(zone, &l_inactive, 1509 LRU_BASE + file * LRU_FILE); 1510 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); 1511 spin_unlock_irq(&zone->lru_lock); 1512} 1513 1514#ifdef CONFIG_SWAP 1515static int inactive_anon_is_low_global(struct zone *zone) 1516{ 1517 unsigned long active, inactive; 1518 1519 active = zone_page_state(zone, NR_ACTIVE_ANON); 1520 inactive = zone_page_state(zone, NR_INACTIVE_ANON); 1521 1522 if (inactive * zone->inactive_ratio < active) 1523 return 1; 1524 1525 return 0; 1526} 1527 1528/** 1529 * inactive_anon_is_low - check if anonymous pages need to be deactivated 1530 * @zone: zone to check 1531 * @sc: scan control of this context 1532 * 1533 * Returns true if the zone does not have enough inactive anon pages, 1534 * meaning some active anon pages need to be deactivated. 1535 */ 1536static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) 1537{ 1538 int low; 1539 1540 /* 1541 * If we don't have swap space, anonymous page deactivation 1542 * is pointless. 1543 */ 1544 if (!total_swap_pages) 1545 return 0; 1546 1547 if (scanning_global_lru(sc)) 1548 low = inactive_anon_is_low_global(zone); 1549 else 1550 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); 1551 return low; 1552} 1553#else 1554static inline int inactive_anon_is_low(struct zone *zone, 1555 struct scan_control *sc) 1556{ 1557 return 0; 1558} 1559#endif 1560 1561static int inactive_file_is_low_global(struct zone *zone) 1562{ 1563 unsigned long active, inactive; 1564 1565 active = zone_page_state(zone, NR_ACTIVE_FILE); 1566 inactive = zone_page_state(zone, NR_INACTIVE_FILE); 1567 1568 return (active > inactive); 1569} 1570 1571/** 1572 * inactive_file_is_low - check if file pages need to be deactivated 1573 * @zone: zone to check 1574 * @sc: scan control of this context 1575 * 1576 * When the system is doing streaming IO, memory pressure here 1577 * ensures that active file pages get deactivated, until more 1578 * than half of the file pages are on the inactive list. 1579 * 1580 * Once we get to that situation, protect the system's working 1581 * set from being evicted by disabling active file page aging. 1582 * 1583 * This uses a different ratio than the anonymous pages, because 1584 * the page cache uses a use-once replacement algorithm. 1585 */ 1586static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) 1587{ 1588 int low; 1589 1590 if (scanning_global_lru(sc)) 1591 low = inactive_file_is_low_global(zone); 1592 else 1593 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); 1594 return low; 1595} 1596 1597static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, 1598 int file) 1599{ 1600 if (file) 1601 return inactive_file_is_low(zone, sc); 1602 else 1603 return inactive_anon_is_low(zone, sc); 1604} 1605 1606static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, 1607 struct zone *zone, struct scan_control *sc, int priority) 1608{ 1609 int file = is_file_lru(lru); 1610 1611 if (is_active_lru(lru)) { 1612 if (inactive_list_is_low(zone, sc, file)) 1613 shrink_active_list(nr_to_scan, zone, sc, priority, file); 1614 return 0; 1615 } 1616 1617 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); 1618} 1619 1620/* 1621 * Smallish @nr_to_scan's are deposited in @nr_saved_scan, 1622 * until we collected @swap_cluster_max pages to scan. 1623 */ 1624static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, 1625 unsigned long *nr_saved_scan) 1626{ 1627 unsigned long nr; 1628 1629 *nr_saved_scan += nr_to_scan; 1630 nr = *nr_saved_scan; 1631 1632 if (nr >= SWAP_CLUSTER_MAX) 1633 *nr_saved_scan = 0; 1634 else 1635 nr = 0; 1636 1637 return nr; 1638} 1639 1640/* 1641 * Determine how aggressively the anon and file LRU lists should be 1642 * scanned. The relative value of each set of LRU lists is determined 1643 * by looking at the fraction of the pages scanned we did rotate back 1644 * onto the active list instead of evict. 1645 * 1646 * nr[0] = anon pages to scan; nr[1] = file pages to scan 1647 */ 1648static void get_scan_count(struct zone *zone, struct scan_control *sc, 1649 unsigned long *nr, int priority) 1650{ 1651 unsigned long anon, file, free; 1652 unsigned long anon_prio, file_prio; 1653 unsigned long ap, fp; 1654 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); 1655 u64 fraction[2], denominator; 1656 enum lru_list l; 1657 int noswap = 0; 1658 1659 /* If we have no swap space, do not bother scanning anon pages. */ 1660 if (!sc->may_swap || (nr_swap_pages <= 0)) { 1661 noswap = 1; 1662 fraction[0] = 0; 1663 fraction[1] = 1; 1664 denominator = 1; 1665 goto out; 1666 } 1667 1668 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + 1669 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); 1670 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + 1671 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); 1672 1673 if (scanning_global_lru(sc)) { 1674 free = zone_page_state(zone, NR_FREE_PAGES); 1675 /* If we have very few page cache pages, 1676 force-scan anon pages. */ 1677 if (unlikely(file + free <= high_wmark_pages(zone))) { 1678 fraction[0] = 1; 1679 fraction[1] = 0; 1680 denominator = 1; 1681 goto out; 1682 } 1683 } 1684 1685 /* 1686 * With swappiness at 100, anonymous and file have the same priority. 1687 * This scanning priority is essentially the inverse of IO cost. 1688 */ 1689 anon_prio = sc->swappiness; 1690 file_prio = 200 - sc->swappiness; 1691 1692 /* 1693 * OK, so we have swap space and a fair amount of page cache 1694 * pages. We use the recently rotated / recently scanned 1695 * ratios to determine how valuable each cache is. 1696 * 1697 * Because workloads change over time (and to avoid overflow) 1698 * we keep these statistics as a floating average, which ends 1699 * up weighing recent references more than old ones. 1700 * 1701 * anon in [0], file in [1] 1702 */ 1703 spin_lock_irq(&zone->lru_lock); 1704 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { 1705 reclaim_stat->recent_scanned[0] /= 2; 1706 reclaim_stat->recent_rotated[0] /= 2; 1707 } 1708 1709 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { 1710 reclaim_stat->recent_scanned[1] /= 2; 1711 reclaim_stat->recent_rotated[1] /= 2; 1712 } 1713 1714 /* 1715 * The amount of pressure on anon vs file pages is inversely 1716 * proportional to the fraction of recently scanned pages on 1717 * each list that were recently referenced and in active use. 1718 */ 1719 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); 1720 ap /= reclaim_stat->recent_rotated[0] + 1; 1721 1722 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); 1723 fp /= reclaim_stat->recent_rotated[1] + 1; 1724 spin_unlock_irq(&zone->lru_lock); 1725 1726 fraction[0] = ap; 1727 fraction[1] = fp; 1728 denominator = ap + fp + 1; 1729out: 1730 for_each_evictable_lru(l) { 1731 int file = is_file_lru(l); 1732 unsigned long scan; 1733 1734 scan = zone_nr_lru_pages(zone, sc, l); 1735 if (priority || noswap) { 1736 scan >>= priority; 1737 scan = div64_u64(scan * fraction[file], denominator); 1738 } 1739 nr[l] = nr_scan_try_batch(scan, 1740 &reclaim_stat->nr_saved_scan[l]); 1741 } 1742} 1743 1744static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc) 1745{ 1746 /* 1747 * If we need a large contiguous chunk of memory, or have 1748 * trouble getting a small set of contiguous pages, we 1749 * will reclaim both active and inactive pages. 1750 */ 1751 if (sc->order > PAGE_ALLOC_COSTLY_ORDER) 1752 sc->lumpy_reclaim_mode = 1; 1753 else if (sc->order && priority < DEF_PRIORITY - 2) 1754 sc->lumpy_reclaim_mode = 1; 1755 else 1756 sc->lumpy_reclaim_mode = 0; 1757} 1758 1759/* 1760 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. 1761 */ 1762static void shrink_zone(int priority, struct zone *zone, 1763 struct scan_control *sc) 1764{ 1765 unsigned long nr[NR_LRU_LISTS]; 1766 unsigned long nr_to_scan; 1767 enum lru_list l; 1768 unsigned long nr_reclaimed = sc->nr_reclaimed; 1769 unsigned long nr_to_reclaim = sc->nr_to_reclaim; 1770 1771 get_scan_count(zone, sc, nr, priority); 1772 1773 set_lumpy_reclaim_mode(priority, sc); 1774 1775 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || 1776 nr[LRU_INACTIVE_FILE]) { 1777 for_each_evictable_lru(l) { 1778 if (nr[l]) { 1779 nr_to_scan = min_t(unsigned long, 1780 nr[l], SWAP_CLUSTER_MAX); 1781 nr[l] -= nr_to_scan; 1782 1783 nr_reclaimed += shrink_list(l, nr_to_scan, 1784 zone, sc, priority); 1785 } 1786 } 1787 /* 1788 * On large memory systems, scan >> priority can become 1789 * really large. This is fine for the starting priority; 1790 * we want to put equal scanning pressure on each zone. 1791 * However, if the VM has a harder time of freeing pages, 1792 * with multiple processes reclaiming pages, the total 1793 * freeing target can get unreasonably large. 1794 */ 1795 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) 1796 break; 1797 } 1798 1799 sc->nr_reclaimed = nr_reclaimed; 1800 1801 /* 1802 * Even if we did not try to evict anon pages at all, we want to 1803 * rebalance the anon lru active/inactive ratio. 1804 */ 1805 if (inactive_anon_is_low(zone, sc)) 1806 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); 1807 1808 throttle_vm_writeout(sc->gfp_mask); 1809} 1810 1811/* 1812 * This is the direct reclaim path, for page-allocating processes. We only 1813 * try to reclaim pages from zones which will satisfy the caller's allocation 1814 * request. 1815 * 1816 * We reclaim from a zone even if that zone is over high_wmark_pages(zone). 1817 * Because: 1818 * a) The caller may be trying to free *extra* pages to satisfy a higher-order 1819 * allocation or 1820 * b) The target zone may be at high_wmark_pages(zone) but the lower zones 1821 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' 1822 * zone defense algorithm. 1823 * 1824 * If a zone is deemed to be full of pinned pages then just give it a light 1825 * scan then give up on it. 1826 */ 1827static void shrink_zones(int priority, struct zonelist *zonelist, 1828 struct scan_control *sc) 1829{ 1830 struct zoneref *z; 1831 struct zone *zone; 1832 1833 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1834 gfp_zone(sc->gfp_mask), sc->nodemask) { 1835 if (!populated_zone(zone)) 1836 continue; 1837 /* 1838 * Take care memory controller reclaiming has small influence 1839 * to global LRU. 1840 */ 1841 if (scanning_global_lru(sc)) { 1842 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1843 continue; 1844 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 1845 continue; /* Let kswapd poll it */ 1846 } 1847 1848 shrink_zone(priority, zone, sc); 1849 } 1850} 1851 1852static bool zone_reclaimable(struct zone *zone) 1853{ 1854 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; 1855} 1856 1857/* 1858 * As hibernation is going on, kswapd is freezed so that it can't mark 1859 * the zone into all_unreclaimable. It can't handle OOM during hibernation. 1860 * So let's check zone's unreclaimable in direct reclaim as well as kswapd. 1861 */ 1862static bool all_unreclaimable(struct zonelist *zonelist, 1863 struct scan_control *sc) 1864{ 1865 struct zoneref *z; 1866 struct zone *zone; 1867 bool all_unreclaimable = true; 1868 1869 for_each_zone_zonelist_nodemask(zone, z, zonelist, 1870 gfp_zone(sc->gfp_mask), sc->nodemask) { 1871 if (!populated_zone(zone)) 1872 continue; 1873 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1874 continue; 1875 if (zone_reclaimable(zone)) { 1876 all_unreclaimable = false; 1877 break; 1878 } 1879 } 1880 1881 return all_unreclaimable; 1882} 1883 1884/* 1885 * This is the main entry point to direct page reclaim. 1886 * 1887 * If a full scan of the inactive list fails to free enough memory then we 1888 * are "out of memory" and something needs to be killed. 1889 * 1890 * If the caller is !__GFP_FS then the probability of a failure is reasonably 1891 * high - the zone may be full of dirty or under-writeback pages, which this 1892 * caller can't do much about. We kick the writeback threads and take explicit 1893 * naps in the hope that some of these pages can be written. But if the 1894 * allocating task holds filesystem locks which prevent writeout this might not 1895 * work, and the allocation attempt will fail. 1896 * 1897 * returns: 0, if no pages reclaimed 1898 * else, the number of pages reclaimed 1899 */ 1900static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 1901 struct scan_control *sc) 1902{ 1903 int priority; 1904 unsigned long total_scanned = 0; 1905 struct reclaim_state *reclaim_state = current->reclaim_state; 1906 struct zoneref *z; 1907 struct zone *zone; 1908 unsigned long writeback_threshold; 1909 1910 get_mems_allowed(); 1911 delayacct_freepages_start(); 1912 1913 if (scanning_global_lru(sc)) 1914 count_vm_event(ALLOCSTALL); 1915 1916 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 1917 sc->nr_scanned = 0; 1918 if (!priority) 1919 disable_swap_token(); 1920 shrink_zones(priority, zonelist, sc); 1921 /* 1922 * Don't shrink slabs when reclaiming memory from 1923 * over limit cgroups 1924 */ 1925 if (scanning_global_lru(sc)) { 1926 unsigned long lru_pages = 0; 1927 for_each_zone_zonelist(zone, z, zonelist, 1928 gfp_zone(sc->gfp_mask)) { 1929 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 1930 continue; 1931 1932 lru_pages += zone_reclaimable_pages(zone); 1933 } 1934 1935 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages); 1936 if (reclaim_state) { 1937 sc->nr_reclaimed += reclaim_state->reclaimed_slab; 1938 reclaim_state->reclaimed_slab = 0; 1939 } 1940 } 1941 total_scanned += sc->nr_scanned; 1942 if (sc->nr_reclaimed >= sc->nr_to_reclaim) 1943 goto out; 1944 1945 /* 1946 * Try to write back as many pages as we just scanned. This 1947 * tends to cause slow streaming writers to write data to the 1948 * disk smoothly, at the dirtying rate, which is nice. But 1949 * that's undesirable in laptop mode, where we *want* lumpy 1950 * writeout. So in laptop mode, write out the whole world. 1951 */ 1952 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; 1953 if (total_scanned > writeback_threshold) { 1954 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); 1955 sc->may_writepage = 1; 1956 } 1957 1958 /* Take a nap, wait for some writeback to complete */ 1959 if (!sc->hibernation_mode && sc->nr_scanned && 1960 priority < DEF_PRIORITY - 2) 1961 congestion_wait(BLK_RW_ASYNC, HZ/10); 1962 } 1963 1964out: 1965 delayacct_freepages_end(); 1966 put_mems_allowed(); 1967 1968 if (sc->nr_reclaimed) 1969 return sc->nr_reclaimed; 1970 1971 /* top priority shrink_zones still had more to do? don't OOM, then */ 1972 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) 1973 return 1; 1974 1975 return 0; 1976} 1977 1978unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 1979 gfp_t gfp_mask, nodemask_t *nodemask) 1980{ 1981 unsigned long nr_reclaimed; 1982 struct scan_control sc = { 1983 .gfp_mask = gfp_mask, 1984 .may_writepage = !laptop_mode, 1985 .nr_to_reclaim = SWAP_CLUSTER_MAX, 1986 .may_unmap = 1, 1987 .may_swap = 1, 1988 .swappiness = vm_swappiness, 1989 .order = order, 1990 .mem_cgroup = NULL, 1991 .nodemask = nodemask, 1992 }; 1993 1994 trace_mm_vmscan_direct_reclaim_begin(order, 1995 sc.may_writepage, 1996 gfp_mask); 1997 1998 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 1999 2000 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); 2001 2002 return nr_reclaimed; 2003} 2004 2005#ifdef CONFIG_CGROUP_MEM_RES_CTLR 2006 2007unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 2008 gfp_t gfp_mask, bool noswap, 2009 unsigned int swappiness, 2010 struct zone *zone) 2011{ 2012 struct scan_control sc = { 2013 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2014 .may_writepage = !laptop_mode, 2015 .may_unmap = 1, 2016 .may_swap = !noswap, 2017 .swappiness = swappiness, 2018 .order = 0, 2019 .mem_cgroup = mem, 2020 }; 2021 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2022 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2023 2024 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, 2025 sc.may_writepage, 2026 sc.gfp_mask); 2027 2028 /* 2029 * NOTE: Although we can get the priority field, using it 2030 * here is not a good idea, since it limits the pages we can scan. 2031 * if we don't reclaim here, the shrink_zone from balance_pgdat 2032 * will pick up pages from other mem cgroup's as well. We hack 2033 * the priority and make it zero. 2034 */ 2035 shrink_zone(0, zone, &sc); 2036 2037 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); 2038 2039 return sc.nr_reclaimed; 2040} 2041 2042unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, 2043 gfp_t gfp_mask, 2044 bool noswap, 2045 unsigned int swappiness) 2046{ 2047 struct zonelist *zonelist; 2048 unsigned long nr_reclaimed; 2049 struct scan_control sc = { 2050 .may_writepage = !laptop_mode, 2051 .may_unmap = 1, 2052 .may_swap = !noswap, 2053 .nr_to_reclaim = SWAP_CLUSTER_MAX, 2054 .swappiness = swappiness, 2055 .order = 0, 2056 .mem_cgroup = mem_cont, 2057 .nodemask = NULL, /* we don't care the placement */ 2058 }; 2059 2060 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | 2061 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); 2062 zonelist = NODE_DATA(numa_node_id())->node_zonelists; 2063 2064 trace_mm_vmscan_memcg_reclaim_begin(0, 2065 sc.may_writepage, 2066 sc.gfp_mask); 2067 2068 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2069 2070 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); 2071 2072 return nr_reclaimed; 2073} 2074#endif 2075 2076/* is kswapd sleeping prematurely? */ 2077static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) 2078{ 2079 int i; 2080 2081 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ 2082 if (remaining) 2083 return 1; 2084 2085 /* If after HZ/10, a zone is below the high mark, it's premature */ 2086 for (i = 0; i < pgdat->nr_zones; i++) { 2087 struct zone *zone = pgdat->node_zones + i; 2088 2089 if (!populated_zone(zone)) 2090 continue; 2091 2092 if (zone->all_unreclaimable) 2093 continue; 2094 2095 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone), 2096 0, 0)) 2097 return 1; 2098 } 2099 2100 return 0; 2101} 2102 2103/* 2104 * For kswapd, balance_pgdat() will work across all this node's zones until 2105 * they are all at high_wmark_pages(zone). 2106 * 2107 * Returns the number of pages which were actually freed. 2108 * 2109 * There is special handling here for zones which are full of pinned pages. 2110 * This can happen if the pages are all mlocked, or if they are all used by 2111 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. 2112 * What we do is to detect the case where all pages in the zone have been 2113 * scanned twice and there has been zero successful reclaim. Mark the zone as 2114 * dead and from now on, only perform a short scan. Basically we're polling 2115 * the zone for when the problem goes away. 2116 * 2117 * kswapd scans the zones in the highmem->normal->dma direction. It skips 2118 * zones which have free_pages > high_wmark_pages(zone), but once a zone is 2119 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the 2120 * lower zones regardless of the number of free pages in the lower zones. This 2121 * interoperates with the page allocator fallback scheme to ensure that aging 2122 * of pages is balanced across the zones. 2123 */ 2124static unsigned long balance_pgdat(pg_data_t *pgdat, int order) 2125{ 2126 int all_zones_ok; 2127 int priority; 2128 int i; 2129 unsigned long total_scanned; 2130 struct reclaim_state *reclaim_state = current->reclaim_state; 2131 struct scan_control sc = { 2132 .gfp_mask = GFP_KERNEL, 2133 .may_unmap = 1, 2134 .may_swap = 1, 2135 /* 2136 * kswapd doesn't want to be bailed out while reclaim. because 2137 * we want to put equal scanning pressure on each zone. 2138 */ 2139 .nr_to_reclaim = ULONG_MAX, 2140 .swappiness = vm_swappiness, 2141 .order = order, 2142 .mem_cgroup = NULL, 2143 }; 2144loop_again: 2145 total_scanned = 0; 2146 sc.nr_reclaimed = 0; 2147 sc.may_writepage = !laptop_mode; 2148 count_vm_event(PAGEOUTRUN); 2149 2150 for (priority = DEF_PRIORITY; priority >= 0; priority--) { 2151 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ 2152 unsigned long lru_pages = 0; 2153 int has_under_min_watermark_zone = 0; 2154 2155 /* The swap token gets in the way of swapout... */ 2156 if (!priority) 2157 disable_swap_token(); 2158 2159 all_zones_ok = 1; 2160 2161 /* 2162 * Scan in the highmem->dma direction for the highest 2163 * zone which needs scanning 2164 */ 2165 for (i = pgdat->nr_zones - 1; i >= 0; i--) { 2166 struct zone *zone = pgdat->node_zones + i; 2167 2168 if (!populated_zone(zone)) 2169 continue; 2170 2171 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2172 continue; 2173 2174 /* 2175 * Do some background aging of the anon list, to give 2176 * pages a chance to be referenced before reclaiming. 2177 */ 2178 if (inactive_anon_is_low(zone, &sc)) 2179 shrink_active_list(SWAP_CLUSTER_MAX, zone, 2180 &sc, priority, 0); 2181 2182 if (!zone_watermark_ok(zone, order, 2183 high_wmark_pages(zone), 0, 0)) { 2184 end_zone = i; 2185 break; 2186 } 2187 } 2188 if (i < 0) 2189 goto out; 2190 2191 for (i = 0; i <= end_zone; i++) { 2192 struct zone *zone = pgdat->node_zones + i; 2193 2194 lru_pages += zone_reclaimable_pages(zone); 2195 } 2196 2197 /* 2198 * Now scan the zone in the dma->highmem direction, stopping 2199 * at the last zone which needs scanning. 2200 * 2201 * We do this because the page allocator works in the opposite 2202 * direction. This prevents the page allocator from allocating 2203 * pages behind kswapd's direction of progress, which would 2204 * cause too much scanning of the lower zones. 2205 */ 2206 for (i = 0; i <= end_zone; i++) { 2207 struct zone *zone = pgdat->node_zones + i; 2208 int nr_slab; 2209 2210 if (!populated_zone(zone)) 2211 continue; 2212 2213 if (zone->all_unreclaimable && priority != DEF_PRIORITY) 2214 continue; 2215 2216 sc.nr_scanned = 0; 2217 2218 /* 2219 * Call soft limit reclaim before calling shrink_zone. 2220 * For now we ignore the return value 2221 */ 2222 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask); 2223 2224 /* 2225 * We put equal pressure on every zone, unless one 2226 * zone has way too many pages free already. 2227 */ 2228 if (!zone_watermark_ok(zone, order, 2229 8*high_wmark_pages(zone), end_zone, 0)) 2230 shrink_zone(priority, zone, &sc); 2231 reclaim_state->reclaimed_slab = 0; 2232 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, 2233 lru_pages); 2234 sc.nr_reclaimed += reclaim_state->reclaimed_slab; 2235 total_scanned += sc.nr_scanned; 2236 if (zone->all_unreclaimable) 2237 continue; 2238 if (nr_slab == 0 && !zone_reclaimable(zone)) 2239 zone->all_unreclaimable = 1; 2240 /* 2241 * If we've done a decent amount of scanning and 2242 * the reclaim ratio is low, start doing writepage 2243 * even in laptop mode 2244 */ 2245 if (total_scanned > SWAP_CLUSTER_MAX * 2 && 2246 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) 2247 sc.may_writepage = 1; 2248 2249 if (!zone_watermark_ok(zone, order, 2250 high_wmark_pages(zone), end_zone, 0)) { 2251 all_zones_ok = 0; 2252 /* 2253 * We are still under min water mark. This 2254 * means that we have a GFP_ATOMIC allocation 2255 * failure risk. Hurry up! 2256 */ 2257 if (!zone_watermark_ok(zone, order, 2258 min_wmark_pages(zone), end_zone, 0)) 2259 has_under_min_watermark_zone = 1; 2260 } 2261 2262 } 2263 if (all_zones_ok) 2264 break; /* kswapd: all done */ 2265 /* 2266 * OK, kswapd is getting into trouble. Take a nap, then take 2267 * another pass across the zones. 2268 */ 2269 if (total_scanned && (priority < DEF_PRIORITY - 2)) { 2270 if (has_under_min_watermark_zone) 2271 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); 2272 else 2273 congestion_wait(BLK_RW_ASYNC, HZ/10); 2274 } 2275 2276 /* 2277 * We do this so kswapd doesn't build up large priorities for 2278 * example when it is freeing in parallel with allocators. It 2279 * matches the direct reclaim path behaviour in terms of impact 2280 * on zone->*_priority. 2281 */ 2282 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) 2283 break; 2284 } 2285out: 2286 if (!all_zones_ok) { 2287 cond_resched(); 2288 2289 try_to_freeze(); 2290 2291 /* 2292 * Fragmentation may mean that the system cannot be 2293 * rebalanced for high-order allocations in all zones. 2294 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, 2295 * it means the zones have been fully scanned and are still 2296 * not balanced. For high-order allocations, there is 2297 * little point trying all over again as kswapd may 2298 * infinite loop. 2299 * 2300 * Instead, recheck all watermarks at order-0 as they 2301 * are the most important. If watermarks are ok, kswapd will go 2302 * back to sleep. High-order users can still perform direct 2303 * reclaim if they wish. 2304 */ 2305 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) 2306 order = sc.order = 0; 2307 2308 goto loop_again; 2309 } 2310 2311 return sc.nr_reclaimed; 2312} 2313 2314/* 2315 * The background pageout daemon, started as a kernel thread 2316 * from the init process. 2317 * 2318 * This basically trickles out pages so that we have _some_ 2319 * free memory available even if there is no other activity 2320 * that frees anything up. This is needed for things like routing 2321 * etc, where we otherwise might have all activity going on in 2322 * asynchronous contexts that cannot page things out. 2323 * 2324 * If there are applications that are active memory-allocators 2325 * (most normal use), this basically shouldn't matter. 2326 */ 2327static int kswapd(void *p) 2328{ 2329 unsigned long order; 2330 pg_data_t *pgdat = (pg_data_t*)p; 2331 struct task_struct *tsk = current; 2332 DEFINE_WAIT(wait); 2333 struct reclaim_state reclaim_state = { 2334 .reclaimed_slab = 0, 2335 }; 2336 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); 2337 2338 lockdep_set_current_reclaim_state(GFP_KERNEL); 2339 2340 if (!cpumask_empty(cpumask)) 2341 set_cpus_allowed_ptr(tsk, cpumask); 2342 current->reclaim_state = &reclaim_state; 2343 2344 /* 2345 * Tell the memory management that we're a "memory allocator", 2346 * and that if we need more memory we should get access to it 2347 * regardless (see "__alloc_pages()"). "kswapd" should 2348 * never get caught in the normal page freeing logic. 2349 * 2350 * (Kswapd normally doesn't need memory anyway, but sometimes 2351 * you need a small amount of memory in order to be able to 2352 * page out something else, and this flag essentially protects 2353 * us from recursively trying to free more memory as we're 2354 * trying to free the first piece of memory in the first place). 2355 */ 2356 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; 2357 set_freezable(); 2358 2359 order = 0; 2360 for ( ; ; ) { 2361 unsigned long new_order; 2362 int ret; 2363 2364 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2365 new_order = pgdat->kswapd_max_order; 2366 pgdat->kswapd_max_order = 0; 2367 if (order < new_order) { 2368 /* 2369 * Don't sleep if someone wants a larger 'order' 2370 * allocation 2371 */ 2372 order = new_order; 2373 } else { 2374 if (!freezing(current) && !kthread_should_stop()) { 2375 long remaining = 0; 2376 2377 /* Try to sleep for a short interval */ 2378 if (!sleeping_prematurely(pgdat, order, remaining)) { 2379 remaining = schedule_timeout(HZ/10); 2380 finish_wait(&pgdat->kswapd_wait, &wait); 2381 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); 2382 } 2383 2384 /* 2385 * After a short sleep, check if it was a 2386 * premature sleep. If not, then go fully 2387 * to sleep until explicitly woken up 2388 */ 2389 if (!sleeping_prematurely(pgdat, order, remaining)) { 2390 trace_mm_vmscan_kswapd_sleep(pgdat->node_id); 2391 schedule(); 2392 } else { 2393 if (remaining) 2394 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); 2395 else 2396 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); 2397 } 2398 } 2399 2400 order = pgdat->kswapd_max_order; 2401 } 2402 finish_wait(&pgdat->kswapd_wait, &wait); 2403 2404 ret = try_to_freeze(); 2405 if (kthread_should_stop()) 2406 break; 2407 2408 /* 2409 * We can speed up thawing tasks if we don't call balance_pgdat 2410 * after returning from the refrigerator 2411 */ 2412 if (!ret) { 2413 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); 2414 balance_pgdat(pgdat, order); 2415 } 2416 } 2417 return 0; 2418} 2419 2420/* 2421 * A zone is low on free memory, so wake its kswapd task to service it. 2422 */ 2423void wakeup_kswapd(struct zone *zone, int order) 2424{ 2425 pg_data_t *pgdat; 2426 2427 if (!populated_zone(zone)) 2428 return; 2429 2430 pgdat = zone->zone_pgdat; 2431 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0)) 2432 return; 2433 if (pgdat->kswapd_max_order < order) 2434 pgdat->kswapd_max_order = order; 2435 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); 2436 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) 2437 return; 2438 if (!waitqueue_active(&pgdat->kswapd_wait)) 2439 return; 2440 wake_up_interruptible(&pgdat->kswapd_wait); 2441} 2442 2443/* 2444 * The reclaimable count would be mostly accurate. 2445 * The less reclaimable pages may be 2446 * - mlocked pages, which will be moved to unevictable list when encountered 2447 * - mapped pages, which may require several travels to be reclaimed 2448 * - dirty pages, which is not "instantly" reclaimable 2449 */ 2450unsigned long global_reclaimable_pages(void) 2451{ 2452 int nr; 2453 2454 nr = global_page_state(NR_ACTIVE_FILE) + 2455 global_page_state(NR_INACTIVE_FILE); 2456 2457 if (nr_swap_pages > 0) 2458 nr += global_page_state(NR_ACTIVE_ANON) + 2459 global_page_state(NR_INACTIVE_ANON); 2460 2461 return nr; 2462} 2463 2464unsigned long zone_reclaimable_pages(struct zone *zone) 2465{ 2466 int nr; 2467 2468 nr = zone_page_state(zone, NR_ACTIVE_FILE) + 2469 zone_page_state(zone, NR_INACTIVE_FILE); 2470 2471 if (nr_swap_pages > 0) 2472 nr += zone_page_state(zone, NR_ACTIVE_ANON) + 2473 zone_page_state(zone, NR_INACTIVE_ANON); 2474 2475 return nr; 2476} 2477 2478#ifdef CONFIG_HIBERNATION 2479/* 2480 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of 2481 * freed pages. 2482 * 2483 * Rather than trying to age LRUs the aim is to preserve the overall 2484 * LRU order by reclaiming preferentially 2485 * inactive > active > active referenced > active mapped 2486 */ 2487unsigned long shrink_all_memory(unsigned long nr_to_reclaim) 2488{ 2489 struct reclaim_state reclaim_state; 2490 struct scan_control sc = { 2491 .gfp_mask = GFP_HIGHUSER_MOVABLE, 2492 .may_swap = 1, 2493 .may_unmap = 1, 2494 .may_writepage = 1, 2495 .nr_to_reclaim = nr_to_reclaim, 2496 .hibernation_mode = 1, 2497 .swappiness = vm_swappiness, 2498 .order = 0, 2499 }; 2500 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); 2501 struct task_struct *p = current; 2502 unsigned long nr_reclaimed; 2503 2504 p->flags |= PF_MEMALLOC; 2505 lockdep_set_current_reclaim_state(sc.gfp_mask); 2506 reclaim_state.reclaimed_slab = 0; 2507 p->reclaim_state = &reclaim_state; 2508 2509 nr_reclaimed = do_try_to_free_pages(zonelist, &sc); 2510 2511 p->reclaim_state = NULL; 2512 lockdep_clear_current_reclaim_state(); 2513 p->flags &= ~PF_MEMALLOC; 2514 2515 return nr_reclaimed; 2516} 2517#endif /* CONFIG_HIBERNATION */ 2518 2519/* It's optimal to keep kswapds on the same CPUs as their memory, but 2520 not required for correctness. So if the last cpu in a node goes 2521 away, we get changed to run anywhere: as the first one comes back, 2522 restore their cpu bindings. */ 2523static int __devinit cpu_callback(struct notifier_block *nfb, 2524 unsigned long action, void *hcpu) 2525{ 2526 int nid; 2527 2528 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { 2529 for_each_node_state(nid, N_HIGH_MEMORY) { 2530 pg_data_t *pgdat = NODE_DATA(nid); 2531 const struct cpumask *mask; 2532 2533 mask = cpumask_of_node(pgdat->node_id); 2534 2535 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) 2536 /* One of our CPUs online: restore mask */ 2537 set_cpus_allowed_ptr(pgdat->kswapd, mask); 2538 } 2539 } 2540 return NOTIFY_OK; 2541} 2542 2543/* 2544 * This kswapd start function will be called by init and node-hot-add. 2545 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. 2546 */ 2547int kswapd_run(int nid) 2548{ 2549 pg_data_t *pgdat = NODE_DATA(nid); 2550 int ret = 0; 2551 2552 if (pgdat->kswapd) 2553 return 0; 2554 2555 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); 2556 if (IS_ERR(pgdat->kswapd)) { 2557 /* failure at boot is fatal */ 2558 BUG_ON(system_state == SYSTEM_BOOTING); 2559 printk("Failed to start kswapd on node %d\n",nid); 2560 ret = -1; 2561 } 2562 return ret; 2563} 2564 2565/* 2566 * Called by memory hotplug when all memory in a node is offlined. 2567 */ 2568void kswapd_stop(int nid) 2569{ 2570 struct task_struct *kswapd = NODE_DATA(nid)->kswapd; 2571 2572 if (kswapd) 2573 kthread_stop(kswapd); 2574} 2575 2576static int __init kswapd_init(void) 2577{ 2578 int nid; 2579 2580 swap_setup(); 2581 for_each_node_state(nid, N_HIGH_MEMORY) 2582 kswapd_run(nid); 2583 hotcpu_notifier(cpu_callback, 0); 2584 return 0; 2585} 2586 2587module_init(kswapd_init) 2588 2589#ifdef CONFIG_NUMA 2590/* 2591 * Zone reclaim mode 2592 * 2593 * If non-zero call zone_reclaim when the number of free pages falls below 2594 * the watermarks. 2595 */ 2596int zone_reclaim_mode __read_mostly; 2597 2598#define RECLAIM_OFF 0 2599#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ 2600#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ 2601#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ 2602 2603/* 2604 * Priority for ZONE_RECLAIM. This determines the fraction of pages 2605 * of a node considered for each zone_reclaim. 4 scans 1/16th of 2606 * a zone. 2607 */ 2608#define ZONE_RECLAIM_PRIORITY 4 2609 2610/* 2611 * Percentage of pages in a zone that must be unmapped for zone_reclaim to 2612 * occur. 2613 */ 2614int sysctl_min_unmapped_ratio = 1; 2615 2616/* 2617 * If the number of slab pages in a zone grows beyond this percentage then 2618 * slab reclaim needs to occur. 2619 */ 2620int sysctl_min_slab_ratio = 5; 2621 2622static inline unsigned long zone_unmapped_file_pages(struct zone *zone) 2623{ 2624 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); 2625 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + 2626 zone_page_state(zone, NR_ACTIVE_FILE); 2627 2628 /* 2629 * It's possible for there to be more file mapped pages than 2630 * accounted for by the pages on the file LRU lists because 2631 * tmpfs pages accounted for as ANON can also be FILE_MAPPED 2632 */ 2633 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; 2634} 2635 2636/* Work out how many page cache pages we can reclaim in this reclaim_mode */ 2637static long zone_pagecache_reclaimable(struct zone *zone) 2638{ 2639 long nr_pagecache_reclaimable; 2640 long delta = 0; 2641 2642 /* 2643 * If RECLAIM_SWAP is set, then all file pages are considered 2644 * potentially reclaimable. Otherwise, we have to worry about 2645 * pages like swapcache and zone_unmapped_file_pages() provides 2646 * a better estimate 2647 */ 2648 if (zone_reclaim_mode & RECLAIM_SWAP) 2649 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); 2650 else 2651 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); 2652 2653 /* If we can't clean pages, remove dirty pages from consideration */ 2654 if (!(zone_reclaim_mode & RECLAIM_WRITE)) 2655 delta += zone_page_state(zone, NR_FILE_DIRTY); 2656 2657 /* Watch for any possible underflows due to delta */ 2658 if (unlikely(delta > nr_pagecache_reclaimable)) 2659 delta = nr_pagecache_reclaimable; 2660 2661 return nr_pagecache_reclaimable - delta; 2662} 2663 2664/* 2665 * Try to free up some pages from this zone through reclaim. 2666 */ 2667static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2668{ 2669 /* Minimum pages needed in order to stay on node */ 2670 const unsigned long nr_pages = 1 << order; 2671 struct task_struct *p = current; 2672 struct reclaim_state reclaim_state; 2673 int priority; 2674 struct scan_control sc = { 2675 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), 2676 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), 2677 .may_swap = 1, 2678 .nr_to_reclaim = max_t(unsigned long, nr_pages, 2679 SWAP_CLUSTER_MAX), 2680 .gfp_mask = gfp_mask, 2681 .swappiness = vm_swappiness, 2682 .order = order, 2683 }; 2684 unsigned long nr_slab_pages0, nr_slab_pages1; 2685 2686 cond_resched(); 2687 /* 2688 * We need to be able to allocate from the reserves for RECLAIM_SWAP 2689 * and we also need to be able to write out pages for RECLAIM_WRITE 2690 * and RECLAIM_SWAP. 2691 */ 2692 p->flags |= PF_MEMALLOC | PF_SWAPWRITE; 2693 lockdep_set_current_reclaim_state(gfp_mask); 2694 reclaim_state.reclaimed_slab = 0; 2695 p->reclaim_state = &reclaim_state; 2696 2697 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { 2698 /* 2699 * Free memory by calling shrink zone with increasing 2700 * priorities until we have enough memory freed. 2701 */ 2702 priority = ZONE_RECLAIM_PRIORITY; 2703 do { 2704 shrink_zone(priority, zone, &sc); 2705 priority--; 2706 } while (priority >= 0 && sc.nr_reclaimed < nr_pages); 2707 } 2708 2709 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 2710 if (nr_slab_pages0 > zone->min_slab_pages) { 2711 /* 2712 * shrink_slab() does not currently allow us to determine how 2713 * many pages were freed in this zone. So we take the current 2714 * number of slab pages and shake the slab until it is reduced 2715 * by the same nr_pages that we used for reclaiming unmapped 2716 * pages. 2717 * 2718 * Note that shrink_slab will free memory on all zones and may 2719 * take a long time. 2720 */ 2721 for (;;) { 2722 unsigned long lru_pages = zone_reclaimable_pages(zone); 2723 2724 /* No reclaimable slab or very low memory pressure */ 2725 if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages)) 2726 break; 2727 2728 /* Freed enough memory */ 2729 nr_slab_pages1 = zone_page_state(zone, 2730 NR_SLAB_RECLAIMABLE); 2731 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) 2732 break; 2733 } 2734 2735 /* 2736 * Update nr_reclaimed by the number of slab pages we 2737 * reclaimed from this zone. 2738 */ 2739 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); 2740 if (nr_slab_pages1 < nr_slab_pages0) 2741 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; 2742 } 2743 2744 p->reclaim_state = NULL; 2745 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); 2746 lockdep_clear_current_reclaim_state(); 2747 return sc.nr_reclaimed >= nr_pages; 2748} 2749 2750int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 2751{ 2752 int node_id; 2753 int ret; 2754 2755 /* 2756 * Zone reclaim reclaims unmapped file backed pages and 2757 * slab pages if we are over the defined limits. 2758 * 2759 * A small portion of unmapped file backed pages is needed for 2760 * file I/O otherwise pages read by file I/O will be immediately 2761 * thrown out if the zone is overallocated. So we do not reclaim 2762 * if less than a specified percentage of the zone is used by 2763 * unmapped file backed pages. 2764 */ 2765 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && 2766 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) 2767 return ZONE_RECLAIM_FULL; 2768 2769 if (zone->all_unreclaimable) 2770 return ZONE_RECLAIM_FULL; 2771 2772 /* 2773 * Do not scan if the allocation should not be delayed. 2774 */ 2775 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) 2776 return ZONE_RECLAIM_NOSCAN; 2777 2778 /* 2779 * Only run zone reclaim on the local zone or on zones that do not 2780 * have associated processors. This will favor the local processor 2781 * over remote processors and spread off node memory allocations 2782 * as wide as possible. 2783 */ 2784 node_id = zone_to_nid(zone); 2785 if (node_state(node_id, N_CPU) && node_id != numa_node_id()) 2786 return ZONE_RECLAIM_NOSCAN; 2787 2788 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) 2789 return ZONE_RECLAIM_NOSCAN; 2790 2791 ret = __zone_reclaim(zone, gfp_mask, order); 2792 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); 2793 2794 if (!ret) 2795 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); 2796 2797 return ret; 2798} 2799#endif 2800 2801/* 2802 * page_evictable - test whether a page is evictable 2803 * @page: the page to test 2804 * @vma: the VMA in which the page is or will be mapped, may be NULL 2805 * 2806 * Test whether page is evictable--i.e., should be placed on active/inactive 2807 * lists vs unevictable list. The vma argument is !NULL when called from the 2808 * fault path to determine how to instantate a new page. 2809 * 2810 * Reasons page might not be evictable: 2811 * (1) page's mapping marked unevictable 2812 * (2) page is part of an mlocked VMA 2813 * 2814 */ 2815int page_evictable(struct page *page, struct vm_area_struct *vma) 2816{ 2817 2818 if (mapping_unevictable(page_mapping(page))) 2819 return 0; 2820 2821 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) 2822 return 0; 2823 2824 return 1; 2825} 2826 2827/** 2828 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list 2829 * @page: page to check evictability and move to appropriate lru list 2830 * @zone: zone page is in 2831 * 2832 * Checks a page for evictability and moves the page to the appropriate 2833 * zone lru list. 2834 * 2835 * Restrictions: zone->lru_lock must be held, page must be on LRU and must 2836 * have PageUnevictable set. 2837 */ 2838static void check_move_unevictable_page(struct page *page, struct zone *zone) 2839{ 2840 VM_BUG_ON(PageActive(page)); 2841 2842retry: 2843 ClearPageUnevictable(page); 2844 if (page_evictable(page, NULL)) { 2845 enum lru_list l = page_lru_base_type(page); 2846 2847 __dec_zone_state(zone, NR_UNEVICTABLE); 2848 list_move(&page->lru, &zone->lru[l].list); 2849 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); 2850 __inc_zone_state(zone, NR_INACTIVE_ANON + l); 2851 __count_vm_event(UNEVICTABLE_PGRESCUED); 2852 } else { 2853 /* 2854 * rotate unevictable list 2855 */ 2856 SetPageUnevictable(page); 2857 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); 2858 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); 2859 if (page_evictable(page, NULL)) 2860 goto retry; 2861 } 2862} 2863 2864/** 2865 * scan_mapping_unevictable_pages - scan an address space for evictable pages 2866 * @mapping: struct address_space to scan for evictable pages 2867 * 2868 * Scan all pages in mapping. Check unevictable pages for 2869 * evictability and move them to the appropriate zone lru list. 2870 */ 2871void scan_mapping_unevictable_pages(struct address_space *mapping) 2872{ 2873 pgoff_t next = 0; 2874 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> 2875 PAGE_CACHE_SHIFT; 2876 struct zone *zone; 2877 struct pagevec pvec; 2878 2879 if (mapping->nrpages == 0) 2880 return; 2881 2882 pagevec_init(&pvec, 0); 2883 while (next < end && 2884 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { 2885 int i; 2886 int pg_scanned = 0; 2887 2888 zone = NULL; 2889 2890 for (i = 0; i < pagevec_count(&pvec); i++) { 2891 struct page *page = pvec.pages[i]; 2892 pgoff_t page_index = page->index; 2893 struct zone *pagezone = page_zone(page); 2894 2895 pg_scanned++; 2896 if (page_index > next) 2897 next = page_index; 2898 next++; 2899 2900 if (pagezone != zone) { 2901 if (zone) 2902 spin_unlock_irq(&zone->lru_lock); 2903 zone = pagezone; 2904 spin_lock_irq(&zone->lru_lock); 2905 } 2906 2907 if (PageLRU(page) && PageUnevictable(page)) 2908 check_move_unevictable_page(page, zone); 2909 } 2910 if (zone) 2911 spin_unlock_irq(&zone->lru_lock); 2912 pagevec_release(&pvec); 2913 2914 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); 2915 } 2916 2917} 2918 2919/** 2920 * scan_zone_unevictable_pages - check unevictable list for evictable pages 2921 * @zone - zone of which to scan the unevictable list 2922 * 2923 * Scan @zone's unevictable LRU lists to check for pages that have become 2924 * evictable. Move those that have to @zone's inactive list where they 2925 * become candidates for reclaim, unless shrink_inactive_zone() decides 2926 * to reactivate them. Pages that are still unevictable are rotated 2927 * back onto @zone's unevictable list. 2928 */ 2929#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ 2930static void scan_zone_unevictable_pages(struct zone *zone) 2931{ 2932 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; 2933 unsigned long scan; 2934 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); 2935 2936 while (nr_to_scan > 0) { 2937 unsigned long batch_size = min(nr_to_scan, 2938 SCAN_UNEVICTABLE_BATCH_SIZE); 2939 2940 spin_lock_irq(&zone->lru_lock); 2941 for (scan = 0; scan < batch_size; scan++) { 2942 struct page *page = lru_to_page(l_unevictable); 2943 2944 if (!trylock_page(page)) 2945 continue; 2946 2947 prefetchw_prev_lru_page(page, l_unevictable, flags); 2948 2949 if (likely(PageLRU(page) && PageUnevictable(page))) 2950 check_move_unevictable_page(page, zone); 2951 2952 unlock_page(page); 2953 } 2954 spin_unlock_irq(&zone->lru_lock); 2955 2956 nr_to_scan -= batch_size; 2957 } 2958} 2959 2960 2961/** 2962 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages 2963 * 2964 * A really big hammer: scan all zones' unevictable LRU lists to check for 2965 * pages that have become evictable. Move those back to the zones' 2966 * inactive list where they become candidates for reclaim. 2967 * This occurs when, e.g., we have unswappable pages on the unevictable lists, 2968 * and we add swap to the system. As such, it runs in the context of a task 2969 * that has possibly/probably made some previously unevictable pages 2970 * evictable. 2971 */ 2972static void scan_all_zones_unevictable_pages(void) 2973{ 2974 struct zone *zone; 2975 2976 for_each_zone(zone) { 2977 scan_zone_unevictable_pages(zone); 2978 } 2979} 2980 2981/* 2982 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of 2983 * all nodes' unevictable lists for evictable pages 2984 */ 2985unsigned long scan_unevictable_pages; 2986 2987int scan_unevictable_handler(struct ctl_table *table, int write, 2988 void __user *buffer, 2989 size_t *length, loff_t *ppos) 2990{ 2991 proc_doulongvec_minmax(table, write, buffer, length, ppos); 2992 2993 if (write && *(unsigned long *)table->data) 2994 scan_all_zones_unevictable_pages(); 2995 2996 scan_unevictable_pages = 0; 2997 return 0; 2998} 2999 3000#ifdef CONFIG_NUMA 3001/* 3002 * per node 'scan_unevictable_pages' attribute. On demand re-scan of 3003 * a specified node's per zone unevictable lists for evictable pages. 3004 */ 3005 3006static ssize_t read_scan_unevictable_node(struct sys_device *dev, 3007 struct sysdev_attribute *attr, 3008 char *buf) 3009{ 3010 return sprintf(buf, "0\n"); /* always zero; should fit... */ 3011} 3012 3013static ssize_t write_scan_unevictable_node(struct sys_device *dev, 3014 struct sysdev_attribute *attr, 3015 const char *buf, size_t count) 3016{ 3017 struct zone *node_zones = NODE_DATA(dev->id)->node_zones; 3018 struct zone *zone; 3019 unsigned long res; 3020 unsigned long req = strict_strtoul(buf, 10, &res); 3021 3022 if (!req) 3023 return 1; /* zero is no-op */ 3024 3025 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { 3026 if (!populated_zone(zone)) 3027 continue; 3028 scan_zone_unevictable_pages(zone); 3029 } 3030 return 1; 3031} 3032 3033 3034static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, 3035 read_scan_unevictable_node, 3036 write_scan_unevictable_node); 3037 3038int scan_unevictable_register_node(struct node *node) 3039{ 3040 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); 3041} 3042 3043void scan_unevictable_unregister_node(struct node *node) 3044{ 3045 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); 3046} 3047#endif 3048