4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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.
15 #include <linux/module.h>
16 #include <linux/gfp.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
45 #include <linux/prefetch.h>
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
50 #include <linux/swapops.h>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
58 * reclaim_mode determines how the inactive list is shrunk
59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60 * RECLAIM_MODE_ASYNC: Do not block
61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 * page from the LRU and reclaim all pages within a
64 * naturally aligned range
65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66 * order-0 pages and then compact the zone
68 typedef unsigned __bitwise__ reclaim_mode_t;
69 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
70 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
71 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
72 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
73 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
76 /* Incremented by the number of inactive pages that were scanned */
77 unsigned long nr_scanned;
79 /* Number of pages freed so far during a call to shrink_zones() */
80 unsigned long nr_reclaimed;
82 /* How many pages shrink_list() should reclaim */
83 unsigned long nr_to_reclaim;
85 unsigned long hibernation_mode;
87 /* This context's GFP mask */
92 /* Can mapped pages be reclaimed? */
95 /* Can pages be swapped as part of reclaim? */
101 * Intend to reclaim enough continuous memory rather than reclaim
102 * enough amount of memory. i.e, mode for high order allocation.
104 reclaim_mode_t reclaim_mode;
106 /* Which cgroup do we reclaim from */
107 struct mem_cgroup *mem_cgroup;
110 * Nodemask of nodes allowed by the caller. If NULL, all nodes
113 nodemask_t *nodemask;
116 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
118 #ifdef ARCH_HAS_PREFETCH
119 #define prefetch_prev_lru_page(_page, _base, _field) \
121 if ((_page)->lru.prev != _base) { \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetch(&prev->_field); \
129 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
132 #ifdef ARCH_HAS_PREFETCHW
133 #define prefetchw_prev_lru_page(_page, _base, _field) \
135 if ((_page)->lru.prev != _base) { \
138 prev = lru_to_page(&(_page->lru)); \
139 prefetchw(&prev->_field); \
143 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
147 * From 0 .. 100. Higher means more swappy.
149 int vm_swappiness = 60;
150 long vm_total_pages; /* The total number of pages which the VM controls */
152 static LIST_HEAD(shrinker_list);
153 static DECLARE_RWSEM(shrinker_rwsem);
155 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
156 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
158 #define scanning_global_lru(sc) (1)
161 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
162 struct scan_control *sc)
164 if (!scanning_global_lru(sc))
165 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
167 return &zone->reclaim_stat;
170 static unsigned long zone_nr_lru_pages(struct zone *zone,
171 struct scan_control *sc, enum lru_list lru)
173 if (!scanning_global_lru(sc))
174 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup,
175 zone_to_nid(zone), zone_idx(zone), BIT(lru));
177 return zone_page_state(zone, NR_LRU_BASE + lru);
182 * Add a shrinker callback to be called from the vm
184 void register_shrinker(struct shrinker *shrinker)
187 down_write(&shrinker_rwsem);
188 list_add_tail(&shrinker->list, &shrinker_list);
189 up_write(&shrinker_rwsem);
191 EXPORT_SYMBOL(register_shrinker);
196 void unregister_shrinker(struct shrinker *shrinker)
198 down_write(&shrinker_rwsem);
199 list_del(&shrinker->list);
200 up_write(&shrinker_rwsem);
202 EXPORT_SYMBOL(unregister_shrinker);
204 static inline int do_shrinker_shrink(struct shrinker *shrinker,
205 struct shrink_control *sc,
206 unsigned long nr_to_scan)
208 sc->nr_to_scan = nr_to_scan;
209 return (*shrinker->shrink)(shrinker, sc);
212 #define SHRINK_BATCH 128
214 * Call the shrink functions to age shrinkable caches
216 * Here we assume it costs one seek to replace a lru page and that it also
217 * takes a seek to recreate a cache object. With this in mind we age equal
218 * percentages of the lru and ageable caches. This should balance the seeks
219 * generated by these structures.
221 * If the vm encountered mapped pages on the LRU it increase the pressure on
222 * slab to avoid swapping.
224 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
226 * `lru_pages' represents the number of on-LRU pages in all the zones which
227 * are eligible for the caller's allocation attempt. It is used for balancing
228 * slab reclaim versus page reclaim.
230 * Returns the number of slab objects which we shrunk.
232 unsigned long shrink_slab(struct shrink_control *shrink,
233 unsigned long nr_pages_scanned,
234 unsigned long lru_pages)
236 struct shrinker *shrinker;
237 unsigned long ret = 0;
239 if (nr_pages_scanned == 0)
240 nr_pages_scanned = SWAP_CLUSTER_MAX;
242 if (!down_read_trylock(&shrinker_rwsem)) {
243 /* Assume we'll be able to shrink next time */
248 list_for_each_entry(shrinker, &shrinker_list, list) {
249 unsigned long long delta;
250 unsigned long total_scan;
251 unsigned long max_pass;
255 long batch_size = shrinker->batch ? shrinker->batch
259 * copy the current shrinker scan count into a local variable
260 * and zero it so that other concurrent shrinker invocations
261 * don't also do this scanning work.
265 } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
268 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
269 delta = (4 * nr_pages_scanned) / shrinker->seeks;
271 do_div(delta, lru_pages + 1);
273 if (total_scan < 0) {
274 printk(KERN_ERR "shrink_slab: %pF negative objects to "
276 shrinker->shrink, total_scan);
277 total_scan = max_pass;
281 * We need to avoid excessive windup on filesystem shrinkers
282 * due to large numbers of GFP_NOFS allocations causing the
283 * shrinkers to return -1 all the time. This results in a large
284 * nr being built up so when a shrink that can do some work
285 * comes along it empties the entire cache due to nr >>>
286 * max_pass. This is bad for sustaining a working set in
289 * Hence only allow the shrinker to scan the entire cache when
290 * a large delta change is calculated directly.
292 if (delta < max_pass / 4)
293 total_scan = min(total_scan, max_pass / 2);
296 * Avoid risking looping forever due to too large nr value:
297 * never try to free more than twice the estimate number of
300 if (total_scan > max_pass * 2)
301 total_scan = max_pass * 2;
303 trace_mm_shrink_slab_start(shrinker, shrink, nr,
304 nr_pages_scanned, lru_pages,
305 max_pass, delta, total_scan);
307 while (total_scan >= batch_size) {
310 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
311 shrink_ret = do_shrinker_shrink(shrinker, shrink,
313 if (shrink_ret == -1)
315 if (shrink_ret < nr_before)
316 ret += nr_before - shrink_ret;
317 count_vm_events(SLABS_SCANNED, batch_size);
318 total_scan -= batch_size;
324 * move the unused scan count back into the shrinker in a
325 * manner that handles concurrent updates. If we exhausted the
326 * scan, there is no need to do an update.
330 new_nr = total_scan + nr;
333 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
335 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
337 up_read(&shrinker_rwsem);
343 static void set_reclaim_mode(int priority, struct scan_control *sc,
346 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
349 * Initially assume we are entering either lumpy reclaim or
350 * reclaim/compaction.Depending on the order, we will either set the
351 * sync mode or just reclaim order-0 pages later.
353 if (COMPACTION_BUILD)
354 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
356 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
359 * Avoid using lumpy reclaim or reclaim/compaction if possible by
360 * restricting when its set to either costly allocations or when
361 * under memory pressure
363 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
364 sc->reclaim_mode |= syncmode;
365 else if (sc->order && priority < DEF_PRIORITY - 2)
366 sc->reclaim_mode |= syncmode;
368 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
371 static void reset_reclaim_mode(struct scan_control *sc)
373 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
376 static inline int is_page_cache_freeable(struct page *page)
379 * A freeable page cache page is referenced only by the caller
380 * that isolated the page, the page cache radix tree and
381 * optional buffer heads at page->private.
383 return page_count(page) - page_has_private(page) == 2;
386 static int may_write_to_queue(struct backing_dev_info *bdi,
387 struct scan_control *sc)
389 if (current->flags & PF_SWAPWRITE)
391 if (!bdi_write_congested(bdi))
393 if (bdi == current->backing_dev_info)
396 /* lumpy reclaim for hugepage often need a lot of write */
397 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
403 * We detected a synchronous write error writing a page out. Probably
404 * -ENOSPC. We need to propagate that into the address_space for a subsequent
405 * fsync(), msync() or close().
407 * The tricky part is that after writepage we cannot touch the mapping: nothing
408 * prevents it from being freed up. But we have a ref on the page and once
409 * that page is locked, the mapping is pinned.
411 * We're allowed to run sleeping lock_page() here because we know the caller has
414 static void handle_write_error(struct address_space *mapping,
415 struct page *page, int error)
418 if (page_mapping(page) == mapping)
419 mapping_set_error(mapping, error);
423 /* possible outcome of pageout() */
425 /* failed to write page out, page is locked */
427 /* move page to the active list, page is locked */
429 /* page has been sent to the disk successfully, page is unlocked */
431 /* page is clean and locked */
436 * pageout is called by shrink_page_list() for each dirty page.
437 * Calls ->writepage().
439 static pageout_t pageout(struct page *page, struct address_space *mapping,
440 struct scan_control *sc)
443 * If the page is dirty, only perform writeback if that write
444 * will be non-blocking. To prevent this allocation from being
445 * stalled by pagecache activity. But note that there may be
446 * stalls if we need to run get_block(). We could test
447 * PagePrivate for that.
449 * If this process is currently in __generic_file_aio_write() against
450 * this page's queue, we can perform writeback even if that
453 * If the page is swapcache, write it back even if that would
454 * block, for some throttling. This happens by accident, because
455 * swap_backing_dev_info is bust: it doesn't reflect the
456 * congestion state of the swapdevs. Easy to fix, if needed.
458 if (!is_page_cache_freeable(page))
462 * Some data journaling orphaned pages can have
463 * page->mapping == NULL while being dirty with clean buffers.
465 if (page_has_private(page)) {
466 if (try_to_free_buffers(page)) {
467 ClearPageDirty(page);
468 printk("%s: orphaned page\n", __func__);
474 if (mapping->a_ops->writepage == NULL)
475 return PAGE_ACTIVATE;
476 if (!may_write_to_queue(mapping->backing_dev_info, sc))
479 if (clear_page_dirty_for_io(page)) {
481 struct writeback_control wbc = {
482 .sync_mode = WB_SYNC_NONE,
483 .nr_to_write = SWAP_CLUSTER_MAX,
485 .range_end = LLONG_MAX,
489 SetPageReclaim(page);
490 res = mapping->a_ops->writepage(page, &wbc);
492 handle_write_error(mapping, page, res);
493 if (res == AOP_WRITEPAGE_ACTIVATE) {
494 ClearPageReclaim(page);
495 return PAGE_ACTIVATE;
498 if (!PageWriteback(page)) {
499 /* synchronous write or broken a_ops? */
500 ClearPageReclaim(page);
502 trace_mm_vmscan_writepage(page,
503 trace_reclaim_flags(page, sc->reclaim_mode));
504 inc_zone_page_state(page, NR_VMSCAN_WRITE);
512 * Same as remove_mapping, but if the page is removed from the mapping, it
513 * gets returned with a refcount of 0.
515 static int __remove_mapping(struct address_space *mapping, struct page *page)
517 BUG_ON(!PageLocked(page));
518 BUG_ON(mapping != page_mapping(page));
520 spin_lock_irq(&mapping->tree_lock);
522 * The non racy check for a busy page.
524 * Must be careful with the order of the tests. When someone has
525 * a ref to the page, it may be possible that they dirty it then
526 * drop the reference. So if PageDirty is tested before page_count
527 * here, then the following race may occur:
529 * get_user_pages(&page);
530 * [user mapping goes away]
532 * !PageDirty(page) [good]
533 * SetPageDirty(page);
535 * !page_count(page) [good, discard it]
537 * [oops, our write_to data is lost]
539 * Reversing the order of the tests ensures such a situation cannot
540 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
541 * load is not satisfied before that of page->_count.
543 * Note that if SetPageDirty is always performed via set_page_dirty,
544 * and thus under tree_lock, then this ordering is not required.
546 if (!page_freeze_refs(page, 2))
548 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
549 if (unlikely(PageDirty(page))) {
550 page_unfreeze_refs(page, 2);
554 if (PageSwapCache(page)) {
555 swp_entry_t swap = { .val = page_private(page) };
556 __delete_from_swap_cache(page);
557 spin_unlock_irq(&mapping->tree_lock);
558 swapcache_free(swap, page);
560 void (*freepage)(struct page *);
562 freepage = mapping->a_ops->freepage;
564 __delete_from_page_cache(page);
565 spin_unlock_irq(&mapping->tree_lock);
566 mem_cgroup_uncharge_cache_page(page);
568 if (freepage != NULL)
575 spin_unlock_irq(&mapping->tree_lock);
580 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
581 * someone else has a ref on the page, abort and return 0. If it was
582 * successfully detached, return 1. Assumes the caller has a single ref on
585 int remove_mapping(struct address_space *mapping, struct page *page)
587 if (__remove_mapping(mapping, page)) {
589 * Unfreezing the refcount with 1 rather than 2 effectively
590 * drops the pagecache ref for us without requiring another
593 page_unfreeze_refs(page, 1);
600 * putback_lru_page - put previously isolated page onto appropriate LRU list
601 * @page: page to be put back to appropriate lru list
603 * Add previously isolated @page to appropriate LRU list.
604 * Page may still be unevictable for other reasons.
606 * lru_lock must not be held, interrupts must be enabled.
608 void putback_lru_page(struct page *page)
611 int active = !!TestClearPageActive(page);
612 int was_unevictable = PageUnevictable(page);
614 VM_BUG_ON(PageLRU(page));
617 ClearPageUnevictable(page);
619 if (page_evictable(page, NULL)) {
621 * For evictable pages, we can use the cache.
622 * In event of a race, worst case is we end up with an
623 * unevictable page on [in]active list.
624 * We know how to handle that.
626 lru = active + page_lru_base_type(page);
627 lru_cache_add_lru(page, lru);
630 * Put unevictable pages directly on zone's unevictable
633 lru = LRU_UNEVICTABLE;
634 add_page_to_unevictable_list(page);
636 * When racing with an mlock or AS_UNEVICTABLE clearing
637 * (page is unlocked) make sure that if the other thread
638 * does not observe our setting of PG_lru and fails
639 * isolation/check_move_unevictable_page,
640 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
641 * the page back to the evictable list.
643 * The other side is TestClearPageMlocked() or shmem_lock().
649 * page's status can change while we move it among lru. If an evictable
650 * page is on unevictable list, it never be freed. To avoid that,
651 * check after we added it to the list, again.
653 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
654 if (!isolate_lru_page(page)) {
658 /* This means someone else dropped this page from LRU
659 * So, it will be freed or putback to LRU again. There is
660 * nothing to do here.
664 if (was_unevictable && lru != LRU_UNEVICTABLE)
665 count_vm_event(UNEVICTABLE_PGRESCUED);
666 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
667 count_vm_event(UNEVICTABLE_PGCULLED);
669 put_page(page); /* drop ref from isolate */
672 enum page_references {
674 PAGEREF_RECLAIM_CLEAN,
679 static enum page_references page_check_references(struct page *page,
680 struct scan_control *sc)
682 int referenced_ptes, referenced_page;
683 unsigned long vm_flags;
685 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
686 referenced_page = TestClearPageReferenced(page);
688 /* Lumpy reclaim - ignore references */
689 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
690 return PAGEREF_RECLAIM;
693 * Mlock lost the isolation race with us. Let try_to_unmap()
694 * move the page to the unevictable list.
696 if (vm_flags & VM_LOCKED)
697 return PAGEREF_RECLAIM;
699 if (referenced_ptes) {
701 return PAGEREF_ACTIVATE;
703 * All mapped pages start out with page table
704 * references from the instantiating fault, so we need
705 * to look twice if a mapped file page is used more
708 * Mark it and spare it for another trip around the
709 * inactive list. Another page table reference will
710 * lead to its activation.
712 * Note: the mark is set for activated pages as well
713 * so that recently deactivated but used pages are
716 SetPageReferenced(page);
719 return PAGEREF_ACTIVATE;
724 /* Reclaim if clean, defer dirty pages to writeback */
725 if (referenced_page && !PageSwapBacked(page))
726 return PAGEREF_RECLAIM_CLEAN;
728 return PAGEREF_RECLAIM;
731 static noinline_for_stack void free_page_list(struct list_head *free_pages)
733 struct pagevec freed_pvec;
734 struct page *page, *tmp;
736 pagevec_init(&freed_pvec, 1);
738 list_for_each_entry_safe(page, tmp, free_pages, lru) {
739 list_del(&page->lru);
740 if (!pagevec_add(&freed_pvec, page)) {
741 __pagevec_free(&freed_pvec);
742 pagevec_reinit(&freed_pvec);
746 pagevec_free(&freed_pvec);
750 * shrink_page_list() returns the number of reclaimed pages
752 static unsigned long shrink_page_list(struct list_head *page_list,
754 struct scan_control *sc,
756 unsigned long *ret_nr_dirty,
757 unsigned long *ret_nr_writeback)
759 LIST_HEAD(ret_pages);
760 LIST_HEAD(free_pages);
762 unsigned long nr_dirty = 0;
763 unsigned long nr_congested = 0;
764 unsigned long nr_reclaimed = 0;
765 unsigned long nr_writeback = 0;
769 while (!list_empty(page_list)) {
770 enum page_references references;
771 struct address_space *mapping;
777 page = lru_to_page(page_list);
778 list_del(&page->lru);
780 if (!trylock_page(page))
783 VM_BUG_ON(PageActive(page));
784 VM_BUG_ON(page_zone(page) != zone);
788 if (unlikely(!page_evictable(page, NULL)))
791 if (!sc->may_unmap && page_mapped(page))
794 /* Double the slab pressure for mapped and swapcache pages */
795 if (page_mapped(page) || PageSwapCache(page))
798 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
799 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
801 if (PageWriteback(page)) {
804 * Synchronous reclaim cannot queue pages for
805 * writeback due to the possibility of stack overflow
806 * but if it encounters a page under writeback, wait
807 * for the IO to complete.
809 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
811 wait_on_page_writeback(page);
818 references = page_check_references(page, sc);
819 switch (references) {
820 case PAGEREF_ACTIVATE:
821 goto activate_locked;
824 case PAGEREF_RECLAIM:
825 case PAGEREF_RECLAIM_CLEAN:
826 ; /* try to reclaim the page below */
830 * Anonymous process memory has backing store?
831 * Try to allocate it some swap space here.
833 if (PageAnon(page) && !PageSwapCache(page)) {
834 if (!(sc->gfp_mask & __GFP_IO))
836 if (!add_to_swap(page))
837 goto activate_locked;
841 mapping = page_mapping(page);
844 * The page is mapped into the page tables of one or more
845 * processes. Try to unmap it here.
847 if (page_mapped(page) && mapping) {
848 switch (try_to_unmap(page, TTU_UNMAP)) {
850 goto activate_locked;
856 ; /* try to free the page below */
860 if (PageDirty(page)) {
864 * Only kswapd can writeback filesystem pages to
865 * avoid risk of stack overflow but do not writeback
866 * unless under significant pressure.
868 if (page_is_file_cache(page) &&
869 (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
871 * Immediately reclaim when written back.
872 * Similar in principal to deactivate_page()
873 * except we already have the page isolated
874 * and know it's dirty
876 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
877 SetPageReclaim(page);
882 if (references == PAGEREF_RECLAIM_CLEAN)
886 if (!sc->may_writepage)
889 /* Page is dirty, try to write it out here */
890 switch (pageout(page, mapping, sc)) {
895 goto activate_locked;
897 if (PageWriteback(page))
903 * A synchronous write - probably a ramdisk. Go
904 * ahead and try to reclaim the page.
906 if (!trylock_page(page))
908 if (PageDirty(page) || PageWriteback(page))
910 mapping = page_mapping(page);
912 ; /* try to free the page below */
917 * If the page has buffers, try to free the buffer mappings
918 * associated with this page. If we succeed we try to free
921 * We do this even if the page is PageDirty().
922 * try_to_release_page() does not perform I/O, but it is
923 * possible for a page to have PageDirty set, but it is actually
924 * clean (all its buffers are clean). This happens if the
925 * buffers were written out directly, with submit_bh(). ext3
926 * will do this, as well as the blockdev mapping.
927 * try_to_release_page() will discover that cleanness and will
928 * drop the buffers and mark the page clean - it can be freed.
930 * Rarely, pages can have buffers and no ->mapping. These are
931 * the pages which were not successfully invalidated in
932 * truncate_complete_page(). We try to drop those buffers here
933 * and if that worked, and the page is no longer mapped into
934 * process address space (page_count == 1) it can be freed.
935 * Otherwise, leave the page on the LRU so it is swappable.
937 if (page_has_private(page)) {
938 if (!try_to_release_page(page, sc->gfp_mask))
939 goto activate_locked;
940 if (!mapping && page_count(page) == 1) {
942 if (put_page_testzero(page))
946 * rare race with speculative reference.
947 * the speculative reference will free
948 * this page shortly, so we may
949 * increment nr_reclaimed here (and
950 * leave it off the LRU).
958 if (!mapping || !__remove_mapping(mapping, page))
962 * At this point, we have no other references and there is
963 * no way to pick any more up (removed from LRU, removed
964 * from pagecache). Can use non-atomic bitops now (and
965 * we obviously don't have to worry about waking up a process
966 * waiting on the page lock, because there are no references.
968 __clear_page_locked(page);
973 * Is there need to periodically free_page_list? It would
974 * appear not as the counts should be low
976 list_add(&page->lru, &free_pages);
980 if (PageSwapCache(page))
981 try_to_free_swap(page);
983 putback_lru_page(page);
984 reset_reclaim_mode(sc);
988 /* Not a candidate for swapping, so reclaim swap space. */
989 if (PageSwapCache(page) && vm_swap_full())
990 try_to_free_swap(page);
991 VM_BUG_ON(PageActive(page));
997 reset_reclaim_mode(sc);
999 list_add(&page->lru, &ret_pages);
1000 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
1004 * Tag a zone as congested if all the dirty pages encountered were
1005 * backed by a congested BDI. In this case, reclaimers should just
1006 * back off and wait for congestion to clear because further reclaim
1007 * will encounter the same problem
1009 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
1010 zone_set_flag(zone, ZONE_CONGESTED);
1012 free_page_list(&free_pages);
1014 list_splice(&ret_pages, page_list);
1015 count_vm_events(PGACTIVATE, pgactivate);
1016 *ret_nr_dirty += nr_dirty;
1017 *ret_nr_writeback += nr_writeback;
1018 return nr_reclaimed;
1022 * Attempt to remove the specified page from its LRU. Only take this page
1023 * if it is of the appropriate PageActive status. Pages which are being
1024 * freed elsewhere are also ignored.
1026 * page: page to consider
1027 * mode: one of the LRU isolation modes defined above
1029 * returns 0 on success, -ve errno on failure.
1031 int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
1036 /* Only take pages on the LRU. */
1040 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
1041 (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
1044 * When checking the active state, we need to be sure we are
1045 * dealing with comparible boolean values. Take the logical not
1048 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
1051 if (!all_lru_mode && !!page_is_file_cache(page) != file)
1055 * When this function is being called for lumpy reclaim, we
1056 * initially look into all LRU pages, active, inactive and
1057 * unevictable; only give shrink_page_list evictable pages.
1059 if (PageUnevictable(page))
1064 if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
1067 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1070 if (likely(get_page_unless_zero(page))) {
1072 * Be careful not to clear PageLRU until after we're
1073 * sure the page is not being freed elsewhere -- the
1074 * page release code relies on it.
1084 * zone->lru_lock is heavily contended. Some of the functions that
1085 * shrink the lists perform better by taking out a batch of pages
1086 * and working on them outside the LRU lock.
1088 * For pagecache intensive workloads, this function is the hottest
1089 * spot in the kernel (apart from copy_*_user functions).
1091 * Appropriate locks must be held before calling this function.
1093 * @nr_to_scan: The number of pages to look through on the list.
1094 * @src: The LRU list to pull pages off.
1095 * @dst: The temp list to put pages on to.
1096 * @scanned: The number of pages that were scanned.
1097 * @order: The caller's attempted allocation order
1098 * @mode: One of the LRU isolation modes
1099 * @file: True [1] if isolating file [!anon] pages
1101 * returns how many pages were moved onto *@dst.
1103 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1104 struct list_head *src, struct list_head *dst,
1105 unsigned long *scanned, int order, isolate_mode_t mode,
1108 unsigned long nr_taken = 0;
1109 unsigned long nr_lumpy_taken = 0;
1110 unsigned long nr_lumpy_dirty = 0;
1111 unsigned long nr_lumpy_failed = 0;
1114 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1117 unsigned long end_pfn;
1118 unsigned long page_pfn;
1121 page = lru_to_page(src);
1122 prefetchw_prev_lru_page(page, src, flags);
1124 VM_BUG_ON(!PageLRU(page));
1126 switch (__isolate_lru_page(page, mode, file)) {
1128 list_move(&page->lru, dst);
1129 mem_cgroup_del_lru(page);
1130 nr_taken += hpage_nr_pages(page);
1134 /* else it is being freed elsewhere */
1135 list_move(&page->lru, src);
1136 mem_cgroup_rotate_lru_list(page, page_lru(page));
1147 * Attempt to take all pages in the order aligned region
1148 * surrounding the tag page. Only take those pages of
1149 * the same active state as that tag page. We may safely
1150 * round the target page pfn down to the requested order
1151 * as the mem_map is guaranteed valid out to MAX_ORDER,
1152 * where that page is in a different zone we will detect
1153 * it from its zone id and abort this block scan.
1155 zone_id = page_zone_id(page);
1156 page_pfn = page_to_pfn(page);
1157 pfn = page_pfn & ~((1 << order) - 1);
1158 end_pfn = pfn + (1 << order);
1159 for (; pfn < end_pfn; pfn++) {
1160 struct page *cursor_page;
1162 /* The target page is in the block, ignore it. */
1163 if (unlikely(pfn == page_pfn))
1166 /* Avoid holes within the zone. */
1167 if (unlikely(!pfn_valid_within(pfn)))
1170 cursor_page = pfn_to_page(pfn);
1172 /* Check that we have not crossed a zone boundary. */
1173 if (unlikely(page_zone_id(cursor_page) != zone_id))
1177 * If we don't have enough swap space, reclaiming of
1178 * anon page which don't already have a swap slot is
1181 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1182 !PageSwapCache(cursor_page))
1185 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1186 list_move(&cursor_page->lru, dst);
1187 mem_cgroup_del_lru(cursor_page);
1188 nr_taken += hpage_nr_pages(page);
1190 if (PageDirty(cursor_page))
1195 * Check if the page is freed already.
1197 * We can't use page_count() as that
1198 * requires compound_head and we don't
1199 * have a pin on the page here. If a
1200 * page is tail, we may or may not
1201 * have isolated the head, so assume
1202 * it's not free, it'd be tricky to
1203 * track the head status without a
1206 if (!PageTail(cursor_page) &&
1207 !atomic_read(&cursor_page->_count))
1213 /* If we break out of the loop above, lumpy reclaim failed */
1220 trace_mm_vmscan_lru_isolate(order,
1223 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1228 static unsigned long isolate_pages_global(unsigned long nr,
1229 struct list_head *dst,
1230 unsigned long *scanned, int order,
1231 isolate_mode_t mode,
1232 struct zone *z, int active, int file)
1239 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1244 * clear_active_flags() is a helper for shrink_active_list(), clearing
1245 * any active bits from the pages in the list.
1247 static unsigned long clear_active_flags(struct list_head *page_list,
1248 unsigned int *count)
1254 list_for_each_entry(page, page_list, lru) {
1255 int numpages = hpage_nr_pages(page);
1256 lru = page_lru_base_type(page);
1257 if (PageActive(page)) {
1259 ClearPageActive(page);
1260 nr_active += numpages;
1263 count[lru] += numpages;
1270 * isolate_lru_page - tries to isolate a page from its LRU list
1271 * @page: page to isolate from its LRU list
1273 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1274 * vmstat statistic corresponding to whatever LRU list the page was on.
1276 * Returns 0 if the page was removed from an LRU list.
1277 * Returns -EBUSY if the page was not on an LRU list.
1279 * The returned page will have PageLRU() cleared. If it was found on
1280 * the active list, it will have PageActive set. If it was found on
1281 * the unevictable list, it will have the PageUnevictable bit set. That flag
1282 * may need to be cleared by the caller before letting the page go.
1284 * The vmstat statistic corresponding to the list on which the page was
1285 * found will be decremented.
1288 * (1) Must be called with an elevated refcount on the page. This is a
1289 * fundamentnal difference from isolate_lru_pages (which is called
1290 * without a stable reference).
1291 * (2) the lru_lock must not be held.
1292 * (3) interrupts must be enabled.
1294 int isolate_lru_page(struct page *page)
1298 VM_BUG_ON(!page_count(page));
1300 if (PageLRU(page)) {
1301 struct zone *zone = page_zone(page);
1303 spin_lock_irq(&zone->lru_lock);
1304 if (PageLRU(page)) {
1305 int lru = page_lru(page);
1310 del_page_from_lru_list(zone, page, lru);
1312 spin_unlock_irq(&zone->lru_lock);
1318 * Are there way too many processes in the direct reclaim path already?
1320 static int too_many_isolated(struct zone *zone, int file,
1321 struct scan_control *sc)
1323 unsigned long inactive, isolated;
1325 if (current_is_kswapd())
1328 if (!scanning_global_lru(sc))
1332 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1333 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1335 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1336 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1339 return isolated > inactive;
1343 * TODO: Try merging with migrations version of putback_lru_pages
1345 static noinline_for_stack void
1346 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1347 unsigned long nr_anon, unsigned long nr_file,
1348 struct list_head *page_list)
1351 struct pagevec pvec;
1352 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1354 pagevec_init(&pvec, 1);
1357 * Put back any unfreeable pages.
1359 spin_lock(&zone->lru_lock);
1360 while (!list_empty(page_list)) {
1362 page = lru_to_page(page_list);
1363 VM_BUG_ON(PageLRU(page));
1364 list_del(&page->lru);
1365 if (unlikely(!page_evictable(page, NULL))) {
1366 spin_unlock_irq(&zone->lru_lock);
1367 putback_lru_page(page);
1368 spin_lock_irq(&zone->lru_lock);
1372 lru = page_lru(page);
1373 add_page_to_lru_list(zone, page, lru);
1374 if (is_active_lru(lru)) {
1375 int file = is_file_lru(lru);
1376 int numpages = hpage_nr_pages(page);
1377 reclaim_stat->recent_rotated[file] += numpages;
1379 if (!pagevec_add(&pvec, page)) {
1380 spin_unlock_irq(&zone->lru_lock);
1381 __pagevec_release(&pvec);
1382 spin_lock_irq(&zone->lru_lock);
1385 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1386 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1388 spin_unlock_irq(&zone->lru_lock);
1389 pagevec_release(&pvec);
1392 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1393 struct scan_control *sc,
1394 unsigned long *nr_anon,
1395 unsigned long *nr_file,
1396 struct list_head *isolated_list)
1398 unsigned long nr_active;
1399 unsigned int count[NR_LRU_LISTS] = { 0, };
1400 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1402 nr_active = clear_active_flags(isolated_list, count);
1403 __count_vm_events(PGDEACTIVATE, nr_active);
1405 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1406 -count[LRU_ACTIVE_FILE]);
1407 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1408 -count[LRU_INACTIVE_FILE]);
1409 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1410 -count[LRU_ACTIVE_ANON]);
1411 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1412 -count[LRU_INACTIVE_ANON]);
1414 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1415 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1416 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1417 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1419 reclaim_stat->recent_scanned[0] += *nr_anon;
1420 reclaim_stat->recent_scanned[1] += *nr_file;
1424 * Returns true if a direct reclaim should wait on pages under writeback.
1426 * If we are direct reclaiming for contiguous pages and we do not reclaim
1427 * everything in the list, try again and wait for writeback IO to complete.
1428 * This will stall high-order allocations noticeably. Only do that when really
1429 * need to free the pages under high memory pressure.
1431 static inline bool should_reclaim_stall(unsigned long nr_taken,
1432 unsigned long nr_freed,
1434 struct scan_control *sc)
1436 int lumpy_stall_priority;
1438 /* kswapd should not stall on sync IO */
1439 if (current_is_kswapd())
1442 /* Only stall on lumpy reclaim */
1443 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1446 /* If we have reclaimed everything on the isolated list, no stall */
1447 if (nr_freed == nr_taken)
1451 * For high-order allocations, there are two stall thresholds.
1452 * High-cost allocations stall immediately where as lower
1453 * order allocations such as stacks require the scanning
1454 * priority to be much higher before stalling.
1456 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1457 lumpy_stall_priority = DEF_PRIORITY;
1459 lumpy_stall_priority = DEF_PRIORITY / 3;
1461 return priority <= lumpy_stall_priority;
1465 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1466 * of reclaimed pages
1468 static noinline_for_stack unsigned long
1469 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1470 struct scan_control *sc, int priority, int file)
1472 LIST_HEAD(page_list);
1473 unsigned long nr_scanned;
1474 unsigned long nr_reclaimed = 0;
1475 unsigned long nr_taken;
1476 unsigned long nr_anon;
1477 unsigned long nr_file;
1478 unsigned long nr_dirty = 0;
1479 unsigned long nr_writeback = 0;
1480 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1482 while (unlikely(too_many_isolated(zone, file, sc))) {
1483 congestion_wait(BLK_RW_ASYNC, HZ/10);
1485 /* We are about to die and free our memory. Return now. */
1486 if (fatal_signal_pending(current))
1487 return SWAP_CLUSTER_MAX;
1490 set_reclaim_mode(priority, sc, false);
1491 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
1492 reclaim_mode |= ISOLATE_ACTIVE;
1497 reclaim_mode |= ISOLATE_UNMAPPED;
1498 if (!sc->may_writepage)
1499 reclaim_mode |= ISOLATE_CLEAN;
1501 spin_lock_irq(&zone->lru_lock);
1503 if (scanning_global_lru(sc)) {
1504 nr_taken = isolate_pages_global(nr_to_scan, &page_list,
1505 &nr_scanned, sc->order, reclaim_mode, zone, 0, file);
1506 zone->pages_scanned += nr_scanned;
1507 if (current_is_kswapd())
1508 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1511 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1514 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
1515 &nr_scanned, sc->order, reclaim_mode, zone,
1516 sc->mem_cgroup, 0, file);
1518 * mem_cgroup_isolate_pages() keeps track of
1519 * scanned pages on its own.
1523 if (nr_taken == 0) {
1524 spin_unlock_irq(&zone->lru_lock);
1528 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1530 spin_unlock_irq(&zone->lru_lock);
1532 nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority,
1533 &nr_dirty, &nr_writeback);
1535 /* Check if we should syncronously wait for writeback */
1536 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1537 set_reclaim_mode(priority, sc, true);
1538 nr_reclaimed += shrink_page_list(&page_list, zone, sc,
1539 priority, &nr_dirty, &nr_writeback);
1542 local_irq_disable();
1543 if (current_is_kswapd())
1544 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1545 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1547 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1550 * If reclaim is isolating dirty pages under writeback, it implies
1551 * that the long-lived page allocation rate is exceeding the page
1552 * laundering rate. Either the global limits are not being effective
1553 * at throttling processes due to the page distribution throughout
1554 * zones or there is heavy usage of a slow backing device. The
1555 * only option is to throttle from reclaim context which is not ideal
1556 * as there is no guarantee the dirtying process is throttled in the
1557 * same way balance_dirty_pages() manages.
1559 * This scales the number of dirty pages that must be under writeback
1560 * before throttling depending on priority. It is a simple backoff
1561 * function that has the most effect in the range DEF_PRIORITY to
1562 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1563 * in trouble and reclaim is considered to be in trouble.
1565 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1566 * DEF_PRIORITY-1 50% must be PageWriteback
1567 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1569 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1570 * isolated page is PageWriteback
1572 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
1573 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1575 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1577 nr_scanned, nr_reclaimed,
1579 trace_shrink_flags(file, sc->reclaim_mode));
1580 return nr_reclaimed;
1584 * This moves pages from the active list to the inactive list.
1586 * We move them the other way if the page is referenced by one or more
1587 * processes, from rmap.
1589 * If the pages are mostly unmapped, the processing is fast and it is
1590 * appropriate to hold zone->lru_lock across the whole operation. But if
1591 * the pages are mapped, the processing is slow (page_referenced()) so we
1592 * should drop zone->lru_lock around each page. It's impossible to balance
1593 * this, so instead we remove the pages from the LRU while processing them.
1594 * It is safe to rely on PG_active against the non-LRU pages in here because
1595 * nobody will play with that bit on a non-LRU page.
1597 * The downside is that we have to touch page->_count against each page.
1598 * But we had to alter page->flags anyway.
1601 static void move_active_pages_to_lru(struct zone *zone,
1602 struct list_head *list,
1605 unsigned long pgmoved = 0;
1606 struct pagevec pvec;
1609 pagevec_init(&pvec, 1);
1611 while (!list_empty(list)) {
1612 page = lru_to_page(list);
1614 VM_BUG_ON(PageLRU(page));
1617 list_move(&page->lru, &zone->lru[lru].list);
1618 mem_cgroup_add_lru_list(page, lru);
1619 pgmoved += hpage_nr_pages(page);
1621 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1622 spin_unlock_irq(&zone->lru_lock);
1623 if (buffer_heads_over_limit)
1624 pagevec_strip(&pvec);
1625 __pagevec_release(&pvec);
1626 spin_lock_irq(&zone->lru_lock);
1629 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1630 if (!is_active_lru(lru))
1631 __count_vm_events(PGDEACTIVATE, pgmoved);
1634 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1635 struct scan_control *sc, int priority, int file)
1637 unsigned long nr_taken;
1638 unsigned long pgscanned;
1639 unsigned long vm_flags;
1640 LIST_HEAD(l_hold); /* The pages which were snipped off */
1641 LIST_HEAD(l_active);
1642 LIST_HEAD(l_inactive);
1644 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1645 unsigned long nr_rotated = 0;
1646 isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
1651 reclaim_mode |= ISOLATE_UNMAPPED;
1652 if (!sc->may_writepage)
1653 reclaim_mode |= ISOLATE_CLEAN;
1655 spin_lock_irq(&zone->lru_lock);
1656 if (scanning_global_lru(sc)) {
1657 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1658 &pgscanned, sc->order,
1661 zone->pages_scanned += pgscanned;
1663 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1664 &pgscanned, sc->order,
1666 sc->mem_cgroup, 1, file);
1668 * mem_cgroup_isolate_pages() keeps track of
1669 * scanned pages on its own.
1673 reclaim_stat->recent_scanned[file] += nr_taken;
1675 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1677 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1679 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1680 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1681 spin_unlock_irq(&zone->lru_lock);
1683 while (!list_empty(&l_hold)) {
1685 page = lru_to_page(&l_hold);
1686 list_del(&page->lru);
1688 if (unlikely(!page_evictable(page, NULL))) {
1689 putback_lru_page(page);
1693 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1694 nr_rotated += hpage_nr_pages(page);
1696 * Identify referenced, file-backed active pages and
1697 * give them one more trip around the active list. So
1698 * that executable code get better chances to stay in
1699 * memory under moderate memory pressure. Anon pages
1700 * are not likely to be evicted by use-once streaming
1701 * IO, plus JVM can create lots of anon VM_EXEC pages,
1702 * so we ignore them here.
1704 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1705 list_add(&page->lru, &l_active);
1710 ClearPageActive(page); /* we are de-activating */
1711 list_add(&page->lru, &l_inactive);
1715 * Move pages back to the lru list.
1717 spin_lock_irq(&zone->lru_lock);
1719 * Count referenced pages from currently used mappings as rotated,
1720 * even though only some of them are actually re-activated. This
1721 * helps balance scan pressure between file and anonymous pages in
1724 reclaim_stat->recent_rotated[file] += nr_rotated;
1726 move_active_pages_to_lru(zone, &l_active,
1727 LRU_ACTIVE + file * LRU_FILE);
1728 move_active_pages_to_lru(zone, &l_inactive,
1729 LRU_BASE + file * LRU_FILE);
1730 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1731 spin_unlock_irq(&zone->lru_lock);
1735 static int inactive_anon_is_low_global(struct zone *zone)
1737 unsigned long active, inactive;
1739 active = zone_page_state(zone, NR_ACTIVE_ANON);
1740 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1742 if (inactive * zone->inactive_ratio < active)
1749 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1750 * @zone: zone to check
1751 * @sc: scan control of this context
1753 * Returns true if the zone does not have enough inactive anon pages,
1754 * meaning some active anon pages need to be deactivated.
1756 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1761 * If we don't have swap space, anonymous page deactivation
1764 if (!total_swap_pages)
1767 if (scanning_global_lru(sc))
1768 low = inactive_anon_is_low_global(zone);
1770 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1774 static inline int inactive_anon_is_low(struct zone *zone,
1775 struct scan_control *sc)
1781 static int inactive_file_is_low_global(struct zone *zone)
1783 unsigned long active, inactive;
1785 active = zone_page_state(zone, NR_ACTIVE_FILE);
1786 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1788 return (active > inactive);
1792 * inactive_file_is_low - check if file pages need to be deactivated
1793 * @zone: zone to check
1794 * @sc: scan control of this context
1796 * When the system is doing streaming IO, memory pressure here
1797 * ensures that active file pages get deactivated, until more
1798 * than half of the file pages are on the inactive list.
1800 * Once we get to that situation, protect the system's working
1801 * set from being evicted by disabling active file page aging.
1803 * This uses a different ratio than the anonymous pages, because
1804 * the page cache uses a use-once replacement algorithm.
1806 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1810 if (scanning_global_lru(sc))
1811 low = inactive_file_is_low_global(zone);
1813 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1817 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1821 return inactive_file_is_low(zone, sc);
1823 return inactive_anon_is_low(zone, sc);
1826 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1827 struct zone *zone, struct scan_control *sc, int priority)
1829 int file = is_file_lru(lru);
1831 if (is_active_lru(lru)) {
1832 if (inactive_list_is_low(zone, sc, file))
1833 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1837 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1840 static int vmscan_swappiness(struct scan_control *sc)
1842 if (scanning_global_lru(sc))
1843 return vm_swappiness;
1844 return mem_cgroup_swappiness(sc->mem_cgroup);
1848 * Determine how aggressively the anon and file LRU lists should be
1849 * scanned. The relative value of each set of LRU lists is determined
1850 * by looking at the fraction of the pages scanned we did rotate back
1851 * onto the active list instead of evict.
1853 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1855 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1856 unsigned long *nr, int priority)
1858 unsigned long anon, file, free;
1859 unsigned long anon_prio, file_prio;
1860 unsigned long ap, fp;
1861 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1862 u64 fraction[2], denominator;
1865 bool force_scan = false;
1868 * If the zone or memcg is small, nr[l] can be 0. This
1869 * results in no scanning on this priority and a potential
1870 * priority drop. Global direct reclaim can go to the next
1871 * zone and tends to have no problems. Global kswapd is for
1872 * zone balancing and it needs to scan a minimum amount. When
1873 * reclaiming for a memcg, a priority drop can cause high
1874 * latencies, so it's better to scan a minimum amount there as
1877 if (scanning_global_lru(sc) && current_is_kswapd())
1879 if (!scanning_global_lru(sc))
1882 /* If we have no swap space, do not bother scanning anon pages. */
1883 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1891 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1892 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1893 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1894 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1896 if (scanning_global_lru(sc)) {
1897 free = zone_page_state(zone, NR_FREE_PAGES);
1898 /* If we have very few page cache pages,
1899 force-scan anon pages. */
1900 if (unlikely(file + free <= high_wmark_pages(zone))) {
1909 * With swappiness at 100, anonymous and file have the same priority.
1910 * This scanning priority is essentially the inverse of IO cost.
1912 anon_prio = vmscan_swappiness(sc);
1913 file_prio = 200 - vmscan_swappiness(sc);
1916 * OK, so we have swap space and a fair amount of page cache
1917 * pages. We use the recently rotated / recently scanned
1918 * ratios to determine how valuable each cache is.
1920 * Because workloads change over time (and to avoid overflow)
1921 * we keep these statistics as a floating average, which ends
1922 * up weighing recent references more than old ones.
1924 * anon in [0], file in [1]
1926 spin_lock_irq(&zone->lru_lock);
1927 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1928 reclaim_stat->recent_scanned[0] /= 2;
1929 reclaim_stat->recent_rotated[0] /= 2;
1932 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1933 reclaim_stat->recent_scanned[1] /= 2;
1934 reclaim_stat->recent_rotated[1] /= 2;
1938 * The amount of pressure on anon vs file pages is inversely
1939 * proportional to the fraction of recently scanned pages on
1940 * each list that were recently referenced and in active use.
1942 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1943 ap /= reclaim_stat->recent_rotated[0] + 1;
1945 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1946 fp /= reclaim_stat->recent_rotated[1] + 1;
1947 spin_unlock_irq(&zone->lru_lock);
1951 denominator = ap + fp + 1;
1953 for_each_evictable_lru(l) {
1954 int file = is_file_lru(l);
1957 scan = zone_nr_lru_pages(zone, sc, l);
1958 if (priority || noswap) {
1960 if (!scan && force_scan)
1961 scan = SWAP_CLUSTER_MAX;
1962 scan = div64_u64(scan * fraction[file], denominator);
1969 * Reclaim/compaction depends on a number of pages being freed. To avoid
1970 * disruption to the system, a small number of order-0 pages continue to be
1971 * rotated and reclaimed in the normal fashion. However, by the time we get
1972 * back to the allocator and call try_to_compact_zone(), we ensure that
1973 * there are enough free pages for it to be likely successful
1975 static inline bool should_continue_reclaim(struct zone *zone,
1976 unsigned long nr_reclaimed,
1977 unsigned long nr_scanned,
1978 struct scan_control *sc)
1980 unsigned long pages_for_compaction;
1981 unsigned long inactive_lru_pages;
1983 /* If not in reclaim/compaction mode, stop */
1984 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1987 /* Consider stopping depending on scan and reclaim activity */
1988 if (sc->gfp_mask & __GFP_REPEAT) {
1990 * For __GFP_REPEAT allocations, stop reclaiming if the
1991 * full LRU list has been scanned and we are still failing
1992 * to reclaim pages. This full LRU scan is potentially
1993 * expensive but a __GFP_REPEAT caller really wants to succeed
1995 if (!nr_reclaimed && !nr_scanned)
1999 * For non-__GFP_REPEAT allocations which can presumably
2000 * fail without consequence, stop if we failed to reclaim
2001 * any pages from the last SWAP_CLUSTER_MAX number of
2002 * pages that were scanned. This will return to the
2003 * caller faster at the risk reclaim/compaction and
2004 * the resulting allocation attempt fails
2011 * If we have not reclaimed enough pages for compaction and the
2012 * inactive lists are large enough, continue reclaiming
2014 pages_for_compaction = (2UL << sc->order);
2015 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
2016 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
2017 if (sc->nr_reclaimed < pages_for_compaction &&
2018 inactive_lru_pages > pages_for_compaction)
2021 /* If compaction would go ahead or the allocation would succeed, stop */
2022 switch (compaction_suitable(zone, sc->order)) {
2023 case COMPACT_PARTIAL:
2024 case COMPACT_CONTINUE:
2032 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2034 static void shrink_zone(int priority, struct zone *zone,
2035 struct scan_control *sc)
2037 unsigned long nr[NR_LRU_LISTS];
2038 unsigned long nr_to_scan;
2040 unsigned long nr_reclaimed, nr_scanned;
2041 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2042 struct blk_plug plug;
2046 nr_scanned = sc->nr_scanned;
2047 get_scan_count(zone, sc, nr, priority);
2049 blk_start_plug(&plug);
2050 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2051 nr[LRU_INACTIVE_FILE]) {
2052 for_each_evictable_lru(l) {
2054 nr_to_scan = min_t(unsigned long,
2055 nr[l], SWAP_CLUSTER_MAX);
2056 nr[l] -= nr_to_scan;
2058 nr_reclaimed += shrink_list(l, nr_to_scan,
2059 zone, sc, priority);
2063 * On large memory systems, scan >> priority can become
2064 * really large. This is fine for the starting priority;
2065 * we want to put equal scanning pressure on each zone.
2066 * However, if the VM has a harder time of freeing pages,
2067 * with multiple processes reclaiming pages, the total
2068 * freeing target can get unreasonably large.
2070 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2073 blk_finish_plug(&plug);
2074 sc->nr_reclaimed += nr_reclaimed;
2077 * Even if we did not try to evict anon pages at all, we want to
2078 * rebalance the anon lru active/inactive ratio.
2080 if (inactive_anon_is_low(zone, sc))
2081 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
2083 /* reclaim/compaction might need reclaim to continue */
2084 if (should_continue_reclaim(zone, nr_reclaimed,
2085 sc->nr_scanned - nr_scanned, sc))
2088 throttle_vm_writeout(sc->gfp_mask);
2092 * This is the direct reclaim path, for page-allocating processes. We only
2093 * try to reclaim pages from zones which will satisfy the caller's allocation
2096 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2098 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2100 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2101 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2102 * zone defense algorithm.
2104 * If a zone is deemed to be full of pinned pages then just give it a light
2105 * scan then give up on it.
2107 static void shrink_zones(int priority, struct zonelist *zonelist,
2108 struct scan_control *sc)
2112 unsigned long nr_soft_reclaimed;
2113 unsigned long nr_soft_scanned;
2115 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2116 gfp_zone(sc->gfp_mask), sc->nodemask) {
2117 if (!populated_zone(zone))
2120 * Take care memory controller reclaiming has small influence
2123 if (scanning_global_lru(sc)) {
2124 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2126 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2127 continue; /* Let kswapd poll it */
2128 if (COMPACTION_BUILD) {
2130 * If we already have plenty of memory
2131 * free for compaction, don't free any
2132 * more. Even though compaction is
2133 * invoked for any non-zero order,
2134 * only frequent costly order
2135 * reclamation is disruptive enough to
2136 * become a noticable problem, like
2137 * transparent huge page allocations.
2139 if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
2140 (compaction_suitable(zone, sc->order) ||
2141 compaction_deferred(zone)))
2145 * This steals pages from memory cgroups over softlimit
2146 * and returns the number of reclaimed pages and
2147 * scanned pages. This works for global memory pressure
2148 * and balancing, not for a memcg's limit.
2150 nr_soft_scanned = 0;
2151 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2152 sc->order, sc->gfp_mask,
2154 sc->nr_reclaimed += nr_soft_reclaimed;
2155 sc->nr_scanned += nr_soft_scanned;
2156 /* need some check for avoid more shrink_zone() */
2159 shrink_zone(priority, zone, sc);
2163 static bool zone_reclaimable(struct zone *zone)
2165 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2168 /* All zones in zonelist are unreclaimable? */
2169 static bool all_unreclaimable(struct zonelist *zonelist,
2170 struct scan_control *sc)
2175 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2176 gfp_zone(sc->gfp_mask), sc->nodemask) {
2177 if (!populated_zone(zone))
2179 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2181 if (!zone->all_unreclaimable)
2189 * This is the main entry point to direct page reclaim.
2191 * If a full scan of the inactive list fails to free enough memory then we
2192 * are "out of memory" and something needs to be killed.
2194 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2195 * high - the zone may be full of dirty or under-writeback pages, which this
2196 * caller can't do much about. We kick the writeback threads and take explicit
2197 * naps in the hope that some of these pages can be written. But if the
2198 * allocating task holds filesystem locks which prevent writeout this might not
2199 * work, and the allocation attempt will fail.
2201 * returns: 0, if no pages reclaimed
2202 * else, the number of pages reclaimed
2204 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2205 struct scan_control *sc,
2206 struct shrink_control *shrink)
2209 unsigned long total_scanned = 0;
2210 struct reclaim_state *reclaim_state = current->reclaim_state;
2213 unsigned long writeback_threshold;
2216 delayacct_freepages_start();
2218 if (scanning_global_lru(sc))
2219 count_vm_event(ALLOCSTALL);
2221 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2224 disable_swap_token(sc->mem_cgroup);
2225 shrink_zones(priority, zonelist, sc);
2227 * Don't shrink slabs when reclaiming memory from
2228 * over limit cgroups
2230 if (scanning_global_lru(sc)) {
2231 unsigned long lru_pages = 0;
2232 for_each_zone_zonelist(zone, z, zonelist,
2233 gfp_zone(sc->gfp_mask)) {
2234 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2237 lru_pages += zone_reclaimable_pages(zone);
2240 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2241 if (reclaim_state) {
2242 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2243 reclaim_state->reclaimed_slab = 0;
2246 total_scanned += sc->nr_scanned;
2247 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2251 * Try to write back as many pages as we just scanned. This
2252 * tends to cause slow streaming writers to write data to the
2253 * disk smoothly, at the dirtying rate, which is nice. But
2254 * that's undesirable in laptop mode, where we *want* lumpy
2255 * writeout. So in laptop mode, write out the whole world.
2257 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2258 if (total_scanned > writeback_threshold) {
2259 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2260 sc->may_writepage = 1;
2263 /* Take a nap, wait for some writeback to complete */
2264 if (!sc->hibernation_mode && sc->nr_scanned &&
2265 priority < DEF_PRIORITY - 2) {
2266 struct zone *preferred_zone;
2268 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2269 &cpuset_current_mems_allowed,
2271 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2276 delayacct_freepages_end();
2279 if (sc->nr_reclaimed)
2280 return sc->nr_reclaimed;
2283 * As hibernation is going on, kswapd is freezed so that it can't mark
2284 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2287 if (oom_killer_disabled)
2290 /* top priority shrink_zones still had more to do? don't OOM, then */
2291 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2297 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2298 gfp_t gfp_mask, nodemask_t *nodemask)
2300 unsigned long nr_reclaimed;
2301 struct scan_control sc = {
2302 .gfp_mask = gfp_mask,
2303 .may_writepage = !laptop_mode,
2304 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2309 .nodemask = nodemask,
2311 struct shrink_control shrink = {
2312 .gfp_mask = sc.gfp_mask,
2315 trace_mm_vmscan_direct_reclaim_begin(order,
2319 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2321 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2323 return nr_reclaimed;
2326 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2328 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2329 gfp_t gfp_mask, bool noswap,
2331 unsigned long *nr_scanned)
2333 struct scan_control sc = {
2335 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2336 .may_writepage = !laptop_mode,
2338 .may_swap = !noswap,
2343 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2344 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2346 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2351 * NOTE: Although we can get the priority field, using it
2352 * here is not a good idea, since it limits the pages we can scan.
2353 * if we don't reclaim here, the shrink_zone from balance_pgdat
2354 * will pick up pages from other mem cgroup's as well. We hack
2355 * the priority and make it zero.
2357 shrink_zone(0, zone, &sc);
2359 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2361 *nr_scanned = sc.nr_scanned;
2362 return sc.nr_reclaimed;
2365 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2369 struct zonelist *zonelist;
2370 unsigned long nr_reclaimed;
2372 struct scan_control sc = {
2373 .may_writepage = !laptop_mode,
2375 .may_swap = !noswap,
2376 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2378 .mem_cgroup = mem_cont,
2379 .nodemask = NULL, /* we don't care the placement */
2380 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2381 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2383 struct shrink_control shrink = {
2384 .gfp_mask = sc.gfp_mask,
2388 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2389 * take care of from where we get pages. So the node where we start the
2390 * scan does not need to be the current node.
2392 nid = mem_cgroup_select_victim_node(mem_cont);
2394 zonelist = NODE_DATA(nid)->node_zonelists;
2396 trace_mm_vmscan_memcg_reclaim_begin(0,
2400 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2402 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2404 return nr_reclaimed;
2409 * pgdat_balanced is used when checking if a node is balanced for high-order
2410 * allocations. Only zones that meet watermarks and are in a zone allowed
2411 * by the callers classzone_idx are added to balanced_pages. The total of
2412 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2413 * for the node to be considered balanced. Forcing all zones to be balanced
2414 * for high orders can cause excessive reclaim when there are imbalanced zones.
2415 * The choice of 25% is due to
2416 * o a 16M DMA zone that is balanced will not balance a zone on any
2417 * reasonable sized machine
2418 * o On all other machines, the top zone must be at least a reasonable
2419 * percentage of the middle zones. For example, on 32-bit x86, highmem
2420 * would need to be at least 256M for it to be balance a whole node.
2421 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2422 * to balance a node on its own. These seemed like reasonable ratios.
2424 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2427 unsigned long present_pages = 0;
2430 for (i = 0; i <= classzone_idx; i++)
2431 present_pages += pgdat->node_zones[i].present_pages;
2433 /* A special case here: if zone has no page, we think it's balanced */
2434 return balanced_pages >= (present_pages >> 2);
2437 /* is kswapd sleeping prematurely? */
2438 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2442 unsigned long balanced = 0;
2443 bool all_zones_ok = true;
2445 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2449 /* Check the watermark levels */
2450 for (i = 0; i <= classzone_idx; i++) {
2451 struct zone *zone = pgdat->node_zones + i;
2453 if (!populated_zone(zone))
2457 * balance_pgdat() skips over all_unreclaimable after
2458 * DEF_PRIORITY. Effectively, it considers them balanced so
2459 * they must be considered balanced here as well if kswapd
2462 if (zone->all_unreclaimable) {
2463 balanced += zone->present_pages;
2467 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2469 all_zones_ok = false;
2471 balanced += zone->present_pages;
2475 * For high-order requests, the balanced zones must contain at least
2476 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2480 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2482 return !all_zones_ok;
2486 * For kswapd, balance_pgdat() will work across all this node's zones until
2487 * they are all at high_wmark_pages(zone).
2489 * Returns the final order kswapd was reclaiming at
2491 * There is special handling here for zones which are full of pinned pages.
2492 * This can happen if the pages are all mlocked, or if they are all used by
2493 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2494 * What we do is to detect the case where all pages in the zone have been
2495 * scanned twice and there has been zero successful reclaim. Mark the zone as
2496 * dead and from now on, only perform a short scan. Basically we're polling
2497 * the zone for when the problem goes away.
2499 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2500 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2501 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2502 * lower zones regardless of the number of free pages in the lower zones. This
2503 * interoperates with the page allocator fallback scheme to ensure that aging
2504 * of pages is balanced across the zones.
2506 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2510 unsigned long balanced;
2513 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2514 unsigned long total_scanned;
2515 struct reclaim_state *reclaim_state = current->reclaim_state;
2516 unsigned long nr_soft_reclaimed;
2517 unsigned long nr_soft_scanned;
2518 struct scan_control sc = {
2519 .gfp_mask = GFP_KERNEL,
2523 * kswapd doesn't want to be bailed out while reclaim. because
2524 * we want to put equal scanning pressure on each zone.
2526 .nr_to_reclaim = ULONG_MAX,
2530 struct shrink_control shrink = {
2531 .gfp_mask = sc.gfp_mask,
2535 sc.nr_reclaimed = 0;
2536 sc.may_writepage = !laptop_mode;
2537 count_vm_event(PAGEOUTRUN);
2539 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2540 unsigned long lru_pages = 0;
2541 int has_under_min_watermark_zone = 0;
2543 /* The swap token gets in the way of swapout... */
2545 disable_swap_token(NULL);
2551 * Scan in the highmem->dma direction for the highest
2552 * zone which needs scanning
2554 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2555 struct zone *zone = pgdat->node_zones + i;
2557 if (!populated_zone(zone))
2560 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2564 * Do some background aging of the anon list, to give
2565 * pages a chance to be referenced before reclaiming.
2567 if (inactive_anon_is_low(zone, &sc))
2568 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2571 if (!zone_watermark_ok_safe(zone, order,
2572 high_wmark_pages(zone), 0, 0)) {
2576 /* If balanced, clear the congested flag */
2577 zone_clear_flag(zone, ZONE_CONGESTED);
2583 for (i = 0; i <= end_zone; i++) {
2584 struct zone *zone = pgdat->node_zones + i;
2586 lru_pages += zone_reclaimable_pages(zone);
2590 * Now scan the zone in the dma->highmem direction, stopping
2591 * at the last zone which needs scanning.
2593 * We do this because the page allocator works in the opposite
2594 * direction. This prevents the page allocator from allocating
2595 * pages behind kswapd's direction of progress, which would
2596 * cause too much scanning of the lower zones.
2598 for (i = 0; i <= end_zone; i++) {
2599 struct zone *zone = pgdat->node_zones + i;
2601 unsigned long balance_gap;
2603 if (!populated_zone(zone))
2606 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2611 nr_soft_scanned = 0;
2613 * Call soft limit reclaim before calling shrink_zone.
2615 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2618 sc.nr_reclaimed += nr_soft_reclaimed;
2619 total_scanned += nr_soft_scanned;
2622 * We put equal pressure on every zone, unless
2623 * one zone has way too many pages free
2624 * already. The "too many pages" is defined
2625 * as the high wmark plus a "gap" where the
2626 * gap is either the low watermark or 1%
2627 * of the zone, whichever is smaller.
2629 balance_gap = min(low_wmark_pages(zone),
2630 (zone->present_pages +
2631 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2632 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2633 if (!zone_watermark_ok_safe(zone, order,
2634 high_wmark_pages(zone) + balance_gap,
2636 shrink_zone(priority, zone, &sc);
2638 reclaim_state->reclaimed_slab = 0;
2639 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2640 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2641 total_scanned += sc.nr_scanned;
2643 if (nr_slab == 0 && !zone_reclaimable(zone))
2644 zone->all_unreclaimable = 1;
2648 * If we've done a decent amount of scanning and
2649 * the reclaim ratio is low, start doing writepage
2650 * even in laptop mode
2652 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2653 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2654 sc.may_writepage = 1;
2656 if (zone->all_unreclaimable) {
2657 if (end_zone && end_zone == i)
2662 if (!zone_watermark_ok_safe(zone, order,
2663 high_wmark_pages(zone), end_zone, 0)) {
2666 * We are still under min water mark. This
2667 * means that we have a GFP_ATOMIC allocation
2668 * failure risk. Hurry up!
2670 if (!zone_watermark_ok_safe(zone, order,
2671 min_wmark_pages(zone), end_zone, 0))
2672 has_under_min_watermark_zone = 1;
2675 * If a zone reaches its high watermark,
2676 * consider it to be no longer congested. It's
2677 * possible there are dirty pages backed by
2678 * congested BDIs but as pressure is relieved,
2679 * spectulatively avoid congestion waits
2681 zone_clear_flag(zone, ZONE_CONGESTED);
2682 if (i <= *classzone_idx)
2683 balanced += zone->present_pages;
2687 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2688 break; /* kswapd: all done */
2690 * OK, kswapd is getting into trouble. Take a nap, then take
2691 * another pass across the zones.
2693 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2694 if (has_under_min_watermark_zone)
2695 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2697 congestion_wait(BLK_RW_ASYNC, HZ/10);
2701 * We do this so kswapd doesn't build up large priorities for
2702 * example when it is freeing in parallel with allocators. It
2703 * matches the direct reclaim path behaviour in terms of impact
2704 * on zone->*_priority.
2706 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2712 * order-0: All zones must meet high watermark for a balanced node
2713 * high-order: Balanced zones must make up at least 25% of the node
2714 * for the node to be balanced
2716 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2722 * Fragmentation may mean that the system cannot be
2723 * rebalanced for high-order allocations in all zones.
2724 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2725 * it means the zones have been fully scanned and are still
2726 * not balanced. For high-order allocations, there is
2727 * little point trying all over again as kswapd may
2730 * Instead, recheck all watermarks at order-0 as they
2731 * are the most important. If watermarks are ok, kswapd will go
2732 * back to sleep. High-order users can still perform direct
2733 * reclaim if they wish.
2735 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2736 order = sc.order = 0;
2742 * If kswapd was reclaiming at a higher order, it has the option of
2743 * sleeping without all zones being balanced. Before it does, it must
2744 * ensure that the watermarks for order-0 on *all* zones are met and
2745 * that the congestion flags are cleared. The congestion flag must
2746 * be cleared as kswapd is the only mechanism that clears the flag
2747 * and it is potentially going to sleep here.
2750 for (i = 0; i <= end_zone; i++) {
2751 struct zone *zone = pgdat->node_zones + i;
2753 if (!populated_zone(zone))
2756 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2759 /* Confirm the zone is balanced for order-0 */
2760 if (!zone_watermark_ok(zone, 0,
2761 high_wmark_pages(zone), 0, 0)) {
2762 order = sc.order = 0;
2766 /* If balanced, clear the congested flag */
2767 zone_clear_flag(zone, ZONE_CONGESTED);
2768 if (i <= *classzone_idx)
2769 balanced += zone->present_pages;
2774 * Return the order we were reclaiming at so sleeping_prematurely()
2775 * makes a decision on the order we were last reclaiming at. However,
2776 * if another caller entered the allocator slow path while kswapd
2777 * was awake, order will remain at the higher level
2779 *classzone_idx = end_zone;
2783 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2788 if (freezing(current) || kthread_should_stop())
2791 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2793 /* Try to sleep for a short interval */
2794 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2795 remaining = schedule_timeout(HZ/10);
2796 finish_wait(&pgdat->kswapd_wait, &wait);
2797 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2801 * After a short sleep, check if it was a premature sleep. If not, then
2802 * go fully to sleep until explicitly woken up.
2804 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2805 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2808 * vmstat counters are not perfectly accurate and the estimated
2809 * value for counters such as NR_FREE_PAGES can deviate from the
2810 * true value by nr_online_cpus * threshold. To avoid the zone
2811 * watermarks being breached while under pressure, we reduce the
2812 * per-cpu vmstat threshold while kswapd is awake and restore
2813 * them before going back to sleep.
2815 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2817 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2820 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2822 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2824 finish_wait(&pgdat->kswapd_wait, &wait);
2828 * The background pageout daemon, started as a kernel thread
2829 * from the init process.
2831 * This basically trickles out pages so that we have _some_
2832 * free memory available even if there is no other activity
2833 * that frees anything up. This is needed for things like routing
2834 * etc, where we otherwise might have all activity going on in
2835 * asynchronous contexts that cannot page things out.
2837 * If there are applications that are active memory-allocators
2838 * (most normal use), this basically shouldn't matter.
2840 static int kswapd(void *p)
2842 unsigned long order, new_order;
2843 unsigned balanced_order;
2844 int classzone_idx, new_classzone_idx;
2845 int balanced_classzone_idx;
2846 pg_data_t *pgdat = (pg_data_t*)p;
2847 struct task_struct *tsk = current;
2849 struct reclaim_state reclaim_state = {
2850 .reclaimed_slab = 0,
2852 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2854 lockdep_set_current_reclaim_state(GFP_KERNEL);
2856 if (!cpumask_empty(cpumask))
2857 set_cpus_allowed_ptr(tsk, cpumask);
2858 current->reclaim_state = &reclaim_state;
2861 * Tell the memory management that we're a "memory allocator",
2862 * and that if we need more memory we should get access to it
2863 * regardless (see "__alloc_pages()"). "kswapd" should
2864 * never get caught in the normal page freeing logic.
2866 * (Kswapd normally doesn't need memory anyway, but sometimes
2867 * you need a small amount of memory in order to be able to
2868 * page out something else, and this flag essentially protects
2869 * us from recursively trying to free more memory as we're
2870 * trying to free the first piece of memory in the first place).
2872 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2875 order = new_order = 0;
2877 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2878 balanced_classzone_idx = classzone_idx;
2883 * If the last balance_pgdat was unsuccessful it's unlikely a
2884 * new request of a similar or harder type will succeed soon
2885 * so consider going to sleep on the basis we reclaimed at
2887 if (balanced_classzone_idx >= new_classzone_idx &&
2888 balanced_order == new_order) {
2889 new_order = pgdat->kswapd_max_order;
2890 new_classzone_idx = pgdat->classzone_idx;
2891 pgdat->kswapd_max_order = 0;
2892 pgdat->classzone_idx = pgdat->nr_zones - 1;
2895 if (order < new_order || classzone_idx > new_classzone_idx) {
2897 * Don't sleep if someone wants a larger 'order'
2898 * allocation or has tigher zone constraints
2901 classzone_idx = new_classzone_idx;
2903 kswapd_try_to_sleep(pgdat, balanced_order,
2904 balanced_classzone_idx);
2905 order = pgdat->kswapd_max_order;
2906 classzone_idx = pgdat->classzone_idx;
2908 new_classzone_idx = classzone_idx;
2909 pgdat->kswapd_max_order = 0;
2910 pgdat->classzone_idx = pgdat->nr_zones - 1;
2913 ret = try_to_freeze();
2914 if (kthread_should_stop())
2918 * We can speed up thawing tasks if we don't call balance_pgdat
2919 * after returning from the refrigerator
2922 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2923 balanced_classzone_idx = classzone_idx;
2924 balanced_order = balance_pgdat(pgdat, order,
2925 &balanced_classzone_idx);
2932 * A zone is low on free memory, so wake its kswapd task to service it.
2934 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2938 if (!populated_zone(zone))
2941 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2943 pgdat = zone->zone_pgdat;
2944 if (pgdat->kswapd_max_order < order) {
2945 pgdat->kswapd_max_order = order;
2946 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2948 if (!waitqueue_active(&pgdat->kswapd_wait))
2950 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2953 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2954 wake_up_interruptible(&pgdat->kswapd_wait);
2958 * The reclaimable count would be mostly accurate.
2959 * The less reclaimable pages may be
2960 * - mlocked pages, which will be moved to unevictable list when encountered
2961 * - mapped pages, which may require several travels to be reclaimed
2962 * - dirty pages, which is not "instantly" reclaimable
2964 unsigned long global_reclaimable_pages(void)
2968 nr = global_page_state(NR_ACTIVE_FILE) +
2969 global_page_state(NR_INACTIVE_FILE);
2971 if (nr_swap_pages > 0)
2972 nr += global_page_state(NR_ACTIVE_ANON) +
2973 global_page_state(NR_INACTIVE_ANON);
2978 unsigned long zone_reclaimable_pages(struct zone *zone)
2982 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2983 zone_page_state(zone, NR_INACTIVE_FILE);
2985 if (nr_swap_pages > 0)
2986 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2987 zone_page_state(zone, NR_INACTIVE_ANON);
2992 #ifdef CONFIG_HIBERNATION
2994 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2997 * Rather than trying to age LRUs the aim is to preserve the overall
2998 * LRU order by reclaiming preferentially
2999 * inactive > active > active referenced > active mapped
3001 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
3003 struct reclaim_state reclaim_state;
3004 struct scan_control sc = {
3005 .gfp_mask = GFP_HIGHUSER_MOVABLE,
3009 .nr_to_reclaim = nr_to_reclaim,
3010 .hibernation_mode = 1,
3013 struct shrink_control shrink = {
3014 .gfp_mask = sc.gfp_mask,
3016 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3017 struct task_struct *p = current;
3018 unsigned long nr_reclaimed;
3020 p->flags |= PF_MEMALLOC;
3021 lockdep_set_current_reclaim_state(sc.gfp_mask);
3022 reclaim_state.reclaimed_slab = 0;
3023 p->reclaim_state = &reclaim_state;
3025 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3027 p->reclaim_state = NULL;
3028 lockdep_clear_current_reclaim_state();
3029 p->flags &= ~PF_MEMALLOC;
3031 return nr_reclaimed;
3033 #endif /* CONFIG_HIBERNATION */
3035 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3036 not required for correctness. So if the last cpu in a node goes
3037 away, we get changed to run anywhere: as the first one comes back,
3038 restore their cpu bindings. */
3039 static int __devinit cpu_callback(struct notifier_block *nfb,
3040 unsigned long action, void *hcpu)
3044 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3045 for_each_node_state(nid, N_HIGH_MEMORY) {
3046 pg_data_t *pgdat = NODE_DATA(nid);
3047 const struct cpumask *mask;
3049 mask = cpumask_of_node(pgdat->node_id);
3051 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3052 /* One of our CPUs online: restore mask */
3053 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3060 * This kswapd start function will be called by init and node-hot-add.
3061 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3063 int kswapd_run(int nid)
3065 pg_data_t *pgdat = NODE_DATA(nid);
3071 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3072 if (IS_ERR(pgdat->kswapd)) {
3073 /* failure at boot is fatal */
3074 BUG_ON(system_state == SYSTEM_BOOTING);
3075 printk("Failed to start kswapd on node %d\n",nid);
3082 * Called by memory hotplug when all memory in a node is offlined.
3084 void kswapd_stop(int nid)
3086 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3089 kthread_stop(kswapd);
3092 static int __init kswapd_init(void)
3097 for_each_node_state(nid, N_HIGH_MEMORY)
3099 hotcpu_notifier(cpu_callback, 0);
3103 module_init(kswapd_init)
3109 * If non-zero call zone_reclaim when the number of free pages falls below
3112 int zone_reclaim_mode __read_mostly;
3114 #define RECLAIM_OFF 0
3115 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3116 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3117 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3120 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3121 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3124 #define ZONE_RECLAIM_PRIORITY 4
3127 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3130 int sysctl_min_unmapped_ratio = 1;
3133 * If the number of slab pages in a zone grows beyond this percentage then
3134 * slab reclaim needs to occur.
3136 int sysctl_min_slab_ratio = 5;
3138 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3140 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3141 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3142 zone_page_state(zone, NR_ACTIVE_FILE);
3145 * It's possible for there to be more file mapped pages than
3146 * accounted for by the pages on the file LRU lists because
3147 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3149 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3152 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3153 static long zone_pagecache_reclaimable(struct zone *zone)
3155 long nr_pagecache_reclaimable;
3159 * If RECLAIM_SWAP is set, then all file pages are considered
3160 * potentially reclaimable. Otherwise, we have to worry about
3161 * pages like swapcache and zone_unmapped_file_pages() provides
3164 if (zone_reclaim_mode & RECLAIM_SWAP)
3165 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3167 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3169 /* If we can't clean pages, remove dirty pages from consideration */
3170 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3171 delta += zone_page_state(zone, NR_FILE_DIRTY);
3173 /* Watch for any possible underflows due to delta */
3174 if (unlikely(delta > nr_pagecache_reclaimable))
3175 delta = nr_pagecache_reclaimable;
3177 return nr_pagecache_reclaimable - delta;
3181 * Try to free up some pages from this zone through reclaim.
3183 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3185 /* Minimum pages needed in order to stay on node */
3186 const unsigned long nr_pages = 1 << order;
3187 struct task_struct *p = current;
3188 struct reclaim_state reclaim_state;
3190 struct scan_control sc = {
3191 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3192 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3194 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3196 .gfp_mask = gfp_mask,
3199 struct shrink_control shrink = {
3200 .gfp_mask = sc.gfp_mask,
3202 unsigned long nr_slab_pages0, nr_slab_pages1;
3206 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3207 * and we also need to be able to write out pages for RECLAIM_WRITE
3210 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3211 lockdep_set_current_reclaim_state(gfp_mask);
3212 reclaim_state.reclaimed_slab = 0;
3213 p->reclaim_state = &reclaim_state;
3215 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3217 * Free memory by calling shrink zone with increasing
3218 * priorities until we have enough memory freed.
3220 priority = ZONE_RECLAIM_PRIORITY;
3222 shrink_zone(priority, zone, &sc);
3224 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3227 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3228 if (nr_slab_pages0 > zone->min_slab_pages) {
3230 * shrink_slab() does not currently allow us to determine how
3231 * many pages were freed in this zone. So we take the current
3232 * number of slab pages and shake the slab until it is reduced
3233 * by the same nr_pages that we used for reclaiming unmapped
3236 * Note that shrink_slab will free memory on all zones and may
3240 unsigned long lru_pages = zone_reclaimable_pages(zone);
3242 /* No reclaimable slab or very low memory pressure */
3243 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3246 /* Freed enough memory */
3247 nr_slab_pages1 = zone_page_state(zone,
3248 NR_SLAB_RECLAIMABLE);
3249 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3254 * Update nr_reclaimed by the number of slab pages we
3255 * reclaimed from this zone.
3257 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3258 if (nr_slab_pages1 < nr_slab_pages0)
3259 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3262 p->reclaim_state = NULL;
3263 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3264 lockdep_clear_current_reclaim_state();
3265 return sc.nr_reclaimed >= nr_pages;
3268 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3274 * Zone reclaim reclaims unmapped file backed pages and
3275 * slab pages if we are over the defined limits.
3277 * A small portion of unmapped file backed pages is needed for
3278 * file I/O otherwise pages read by file I/O will be immediately
3279 * thrown out if the zone is overallocated. So we do not reclaim
3280 * if less than a specified percentage of the zone is used by
3281 * unmapped file backed pages.
3283 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3284 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3285 return ZONE_RECLAIM_FULL;
3287 if (zone->all_unreclaimable)
3288 return ZONE_RECLAIM_FULL;
3291 * Do not scan if the allocation should not be delayed.
3293 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3294 return ZONE_RECLAIM_NOSCAN;
3297 * Only run zone reclaim on the local zone or on zones that do not
3298 * have associated processors. This will favor the local processor
3299 * over remote processors and spread off node memory allocations
3300 * as wide as possible.
3302 node_id = zone_to_nid(zone);
3303 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3304 return ZONE_RECLAIM_NOSCAN;
3306 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3307 return ZONE_RECLAIM_NOSCAN;
3309 ret = __zone_reclaim(zone, gfp_mask, order);
3310 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3313 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3320 * page_evictable - test whether a page is evictable
3321 * @page: the page to test
3322 * @vma: the VMA in which the page is or will be mapped, may be NULL
3324 * Test whether page is evictable--i.e., should be placed on active/inactive
3325 * lists vs unevictable list. The vma argument is !NULL when called from the
3326 * fault path to determine how to instantate a new page.
3328 * Reasons page might not be evictable:
3329 * (1) page's mapping marked unevictable
3330 * (2) page is part of an mlocked VMA
3333 int page_evictable(struct page *page, struct vm_area_struct *vma)
3336 if (mapping_unevictable(page_mapping(page)))
3339 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3346 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3347 * @page: page to check evictability and move to appropriate lru list
3348 * @zone: zone page is in
3350 * Checks a page for evictability and moves the page to the appropriate
3353 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3354 * have PageUnevictable set.
3356 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3358 VM_BUG_ON(PageActive(page));
3361 ClearPageUnevictable(page);
3362 if (page_evictable(page, NULL)) {
3363 enum lru_list l = page_lru_base_type(page);
3365 __dec_zone_state(zone, NR_UNEVICTABLE);
3366 list_move(&page->lru, &zone->lru[l].list);
3367 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3368 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3369 __count_vm_event(UNEVICTABLE_PGRESCUED);
3372 * rotate unevictable list
3374 SetPageUnevictable(page);
3375 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3376 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3377 if (page_evictable(page, NULL))
3383 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3384 * @mapping: struct address_space to scan for evictable pages
3386 * Scan all pages in mapping. Check unevictable pages for
3387 * evictability and move them to the appropriate zone lru list.
3389 void scan_mapping_unevictable_pages(struct address_space *mapping)
3392 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3395 struct pagevec pvec;
3397 if (mapping->nrpages == 0)
3400 pagevec_init(&pvec, 0);
3401 while (next < end &&
3402 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3408 for (i = 0; i < pagevec_count(&pvec); i++) {
3409 struct page *page = pvec.pages[i];
3410 pgoff_t page_index = page->index;
3411 struct zone *pagezone = page_zone(page);
3414 if (page_index > next)
3418 if (pagezone != zone) {
3420 spin_unlock_irq(&zone->lru_lock);
3422 spin_lock_irq(&zone->lru_lock);
3425 if (PageLRU(page) && PageUnevictable(page))
3426 check_move_unevictable_page(page, zone);
3429 spin_unlock_irq(&zone->lru_lock);
3430 pagevec_release(&pvec);
3432 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3437 static void warn_scan_unevictable_pages(void)
3439 printk_once(KERN_WARNING
3440 "The scan_unevictable_pages sysctl/node-interface has been "
3441 "disabled for lack of a legitimate use case. If you have "
3442 "one, please send an email to linux-mm@kvack.org.\n");
3446 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3447 * all nodes' unevictable lists for evictable pages
3449 unsigned long scan_unevictable_pages;
3451 int scan_unevictable_handler(struct ctl_table *table, int write,
3452 void __user *buffer,
3453 size_t *length, loff_t *ppos)
3455 warn_scan_unevictable_pages();
3456 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3457 scan_unevictable_pages = 0;
3463 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3464 * a specified node's per zone unevictable lists for evictable pages.
3467 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3468 struct sysdev_attribute *attr,
3471 warn_scan_unevictable_pages();
3472 return sprintf(buf, "0\n"); /* always zero; should fit... */
3475 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3476 struct sysdev_attribute *attr,
3477 const char *buf, size_t count)
3479 warn_scan_unevictable_pages();
3484 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3485 read_scan_unevictable_node,
3486 write_scan_unevictable_node);
3488 int scan_unevictable_register_node(struct node *node)
3490 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3493 void scan_unevictable_unregister_node(struct node *node)
3495 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);