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? */
103 * Intend to reclaim enough continuous memory rather than reclaim
104 * enough amount of memory. i.e, mode for high order allocation.
106 reclaim_mode_t reclaim_mode;
108 /* Which cgroup do we reclaim from */
109 struct mem_cgroup *mem_cgroup;
112 * Nodemask of nodes allowed by the caller. If NULL, all nodes
115 nodemask_t *nodemask;
118 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
120 #ifdef ARCH_HAS_PREFETCH
121 #define prefetch_prev_lru_page(_page, _base, _field) \
123 if ((_page)->lru.prev != _base) { \
126 prev = lru_to_page(&(_page->lru)); \
127 prefetch(&prev->_field); \
131 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
134 #ifdef ARCH_HAS_PREFETCHW
135 #define prefetchw_prev_lru_page(_page, _base, _field) \
137 if ((_page)->lru.prev != _base) { \
140 prev = lru_to_page(&(_page->lru)); \
141 prefetchw(&prev->_field); \
145 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
149 * From 0 .. 100. Higher means more swappy.
151 int vm_swappiness = 60;
152 long vm_total_pages; /* The total number of pages which the VM controls */
154 static LIST_HEAD(shrinker_list);
155 static DECLARE_RWSEM(shrinker_rwsem);
157 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
158 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
160 #define scanning_global_lru(sc) (1)
163 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
164 struct scan_control *sc)
166 if (!scanning_global_lru(sc))
167 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
169 return &zone->reclaim_stat;
172 static unsigned long zone_nr_lru_pages(struct zone *zone,
173 struct scan_control *sc, enum lru_list lru)
175 if (!scanning_global_lru(sc))
176 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
178 return zone_page_state(zone, NR_LRU_BASE + lru);
183 * Add a shrinker callback to be called from the vm
185 void register_shrinker(struct shrinker *shrinker)
188 down_write(&shrinker_rwsem);
189 list_add_tail(&shrinker->list, &shrinker_list);
190 up_write(&shrinker_rwsem);
192 EXPORT_SYMBOL(register_shrinker);
197 void unregister_shrinker(struct shrinker *shrinker)
199 down_write(&shrinker_rwsem);
200 list_del(&shrinker->list);
201 up_write(&shrinker_rwsem);
203 EXPORT_SYMBOL(unregister_shrinker);
205 #define SHRINK_BATCH 128
207 * Call the shrink functions to age shrinkable caches
209 * Here we assume it costs one seek to replace a lru page and that it also
210 * takes a seek to recreate a cache object. With this in mind we age equal
211 * percentages of the lru and ageable caches. This should balance the seeks
212 * generated by these structures.
214 * If the vm encountered mapped pages on the LRU it increase the pressure on
215 * slab to avoid swapping.
217 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
219 * `lru_pages' represents the number of on-LRU pages in all the zones which
220 * are eligible for the caller's allocation attempt. It is used for balancing
221 * slab reclaim versus page reclaim.
223 * Returns the number of slab objects which we shrunk.
225 unsigned long shrink_slab(struct shrink_control *shrink,
226 unsigned long lru_pages)
228 struct shrinker *shrinker;
229 unsigned long ret = 0;
230 unsigned long scanned = shrink->nr_scanned;
231 gfp_t gfp_mask = shrink->gfp_mask;
234 scanned = SWAP_CLUSTER_MAX;
236 if (!down_read_trylock(&shrinker_rwsem)) {
237 /* Assume we'll be able to shrink next time */
242 list_for_each_entry(shrinker, &shrinker_list, list) {
243 unsigned long long delta;
244 unsigned long total_scan;
245 unsigned long max_pass;
247 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
248 delta = (4 * scanned) / shrinker->seeks;
250 do_div(delta, lru_pages + 1);
251 shrinker->nr += delta;
252 if (shrinker->nr < 0) {
253 printk(KERN_ERR "shrink_slab: %pF negative objects to "
255 shrinker->shrink, shrinker->nr);
256 shrinker->nr = max_pass;
260 * Avoid risking looping forever due to too large nr value:
261 * never try to free more than twice the estimate number of
264 if (shrinker->nr > max_pass * 2)
265 shrinker->nr = max_pass * 2;
267 total_scan = shrinker->nr;
270 while (total_scan >= SHRINK_BATCH) {
271 long this_scan = SHRINK_BATCH;
275 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
276 shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
278 if (shrink_ret == -1)
280 if (shrink_ret < nr_before)
281 ret += nr_before - shrink_ret;
282 count_vm_events(SLABS_SCANNED, this_scan);
283 total_scan -= this_scan;
288 shrinker->nr += total_scan;
290 up_read(&shrinker_rwsem);
296 static void set_reclaim_mode(int priority, struct scan_control *sc,
299 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
302 * Initially assume we are entering either lumpy reclaim or
303 * reclaim/compaction.Depending on the order, we will either set the
304 * sync mode or just reclaim order-0 pages later.
306 if (COMPACTION_BUILD)
307 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
309 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
312 * Avoid using lumpy reclaim or reclaim/compaction if possible by
313 * restricting when its set to either costly allocations or when
314 * under memory pressure
316 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
317 sc->reclaim_mode |= syncmode;
318 else if (sc->order && priority < DEF_PRIORITY - 2)
319 sc->reclaim_mode |= syncmode;
321 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
324 static void reset_reclaim_mode(struct scan_control *sc)
326 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
329 static inline int is_page_cache_freeable(struct page *page)
332 * A freeable page cache page is referenced only by the caller
333 * that isolated the page, the page cache radix tree and
334 * optional buffer heads at page->private.
336 return page_count(page) - page_has_private(page) == 2;
339 static int may_write_to_queue(struct backing_dev_info *bdi,
340 struct scan_control *sc)
342 if (current->flags & PF_SWAPWRITE)
344 if (!bdi_write_congested(bdi))
346 if (bdi == current->backing_dev_info)
349 /* lumpy reclaim for hugepage often need a lot of write */
350 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
356 * We detected a synchronous write error writing a page out. Probably
357 * -ENOSPC. We need to propagate that into the address_space for a subsequent
358 * fsync(), msync() or close().
360 * The tricky part is that after writepage we cannot touch the mapping: nothing
361 * prevents it from being freed up. But we have a ref on the page and once
362 * that page is locked, the mapping is pinned.
364 * We're allowed to run sleeping lock_page() here because we know the caller has
367 static void handle_write_error(struct address_space *mapping,
368 struct page *page, int error)
371 if (page_mapping(page) == mapping)
372 mapping_set_error(mapping, error);
376 /* possible outcome of pageout() */
378 /* failed to write page out, page is locked */
380 /* move page to the active list, page is locked */
382 /* page has been sent to the disk successfully, page is unlocked */
384 /* page is clean and locked */
389 * pageout is called by shrink_page_list() for each dirty page.
390 * Calls ->writepage().
392 static pageout_t pageout(struct page *page, struct address_space *mapping,
393 struct scan_control *sc)
396 * If the page is dirty, only perform writeback if that write
397 * will be non-blocking. To prevent this allocation from being
398 * stalled by pagecache activity. But note that there may be
399 * stalls if we need to run get_block(). We could test
400 * PagePrivate for that.
402 * If this process is currently in __generic_file_aio_write() against
403 * this page's queue, we can perform writeback even if that
406 * If the page is swapcache, write it back even if that would
407 * block, for some throttling. This happens by accident, because
408 * swap_backing_dev_info is bust: it doesn't reflect the
409 * congestion state of the swapdevs. Easy to fix, if needed.
411 if (!is_page_cache_freeable(page))
415 * Some data journaling orphaned pages can have
416 * page->mapping == NULL while being dirty with clean buffers.
418 if (page_has_private(page)) {
419 if (try_to_free_buffers(page)) {
420 ClearPageDirty(page);
421 printk("%s: orphaned page\n", __func__);
427 if (mapping->a_ops->writepage == NULL)
428 return PAGE_ACTIVATE;
429 if (!may_write_to_queue(mapping->backing_dev_info, sc))
432 if (clear_page_dirty_for_io(page)) {
434 struct writeback_control wbc = {
435 .sync_mode = WB_SYNC_NONE,
436 .nr_to_write = SWAP_CLUSTER_MAX,
438 .range_end = LLONG_MAX,
442 SetPageReclaim(page);
443 res = mapping->a_ops->writepage(page, &wbc);
445 handle_write_error(mapping, page, res);
446 if (res == AOP_WRITEPAGE_ACTIVATE) {
447 ClearPageReclaim(page);
448 return PAGE_ACTIVATE;
452 * Wait on writeback if requested to. This happens when
453 * direct reclaiming a large contiguous area and the
454 * first attempt to free a range of pages fails.
456 if (PageWriteback(page) &&
457 (sc->reclaim_mode & RECLAIM_MODE_SYNC))
458 wait_on_page_writeback(page);
460 if (!PageWriteback(page)) {
461 /* synchronous write or broken a_ops? */
462 ClearPageReclaim(page);
464 trace_mm_vmscan_writepage(page,
465 trace_reclaim_flags(page, sc->reclaim_mode));
466 inc_zone_page_state(page, NR_VMSCAN_WRITE);
474 * Same as remove_mapping, but if the page is removed from the mapping, it
475 * gets returned with a refcount of 0.
477 static int __remove_mapping(struct address_space *mapping, struct page *page)
479 BUG_ON(!PageLocked(page));
480 BUG_ON(mapping != page_mapping(page));
482 spin_lock_irq(&mapping->tree_lock);
484 * The non racy check for a busy page.
486 * Must be careful with the order of the tests. When someone has
487 * a ref to the page, it may be possible that they dirty it then
488 * drop the reference. So if PageDirty is tested before page_count
489 * here, then the following race may occur:
491 * get_user_pages(&page);
492 * [user mapping goes away]
494 * !PageDirty(page) [good]
495 * SetPageDirty(page);
497 * !page_count(page) [good, discard it]
499 * [oops, our write_to data is lost]
501 * Reversing the order of the tests ensures such a situation cannot
502 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
503 * load is not satisfied before that of page->_count.
505 * Note that if SetPageDirty is always performed via set_page_dirty,
506 * and thus under tree_lock, then this ordering is not required.
508 if (!page_freeze_refs(page, 2))
510 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
511 if (unlikely(PageDirty(page))) {
512 page_unfreeze_refs(page, 2);
516 if (PageSwapCache(page)) {
517 swp_entry_t swap = { .val = page_private(page) };
518 __delete_from_swap_cache(page);
519 spin_unlock_irq(&mapping->tree_lock);
520 swapcache_free(swap, page);
522 void (*freepage)(struct page *);
524 freepage = mapping->a_ops->freepage;
526 __delete_from_page_cache(page);
527 spin_unlock_irq(&mapping->tree_lock);
528 mem_cgroup_uncharge_cache_page(page);
530 if (freepage != NULL)
537 spin_unlock_irq(&mapping->tree_lock);
542 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
543 * someone else has a ref on the page, abort and return 0. If it was
544 * successfully detached, return 1. Assumes the caller has a single ref on
547 int remove_mapping(struct address_space *mapping, struct page *page)
549 if (__remove_mapping(mapping, page)) {
551 * Unfreezing the refcount with 1 rather than 2 effectively
552 * drops the pagecache ref for us without requiring another
555 page_unfreeze_refs(page, 1);
562 * putback_lru_page - put previously isolated page onto appropriate LRU list
563 * @page: page to be put back to appropriate lru list
565 * Add previously isolated @page to appropriate LRU list.
566 * Page may still be unevictable for other reasons.
568 * lru_lock must not be held, interrupts must be enabled.
570 void putback_lru_page(struct page *page)
573 int active = !!TestClearPageActive(page);
574 int was_unevictable = PageUnevictable(page);
576 VM_BUG_ON(PageLRU(page));
579 ClearPageUnevictable(page);
581 if (page_evictable(page, NULL)) {
583 * For evictable pages, we can use the cache.
584 * In event of a race, worst case is we end up with an
585 * unevictable page on [in]active list.
586 * We know how to handle that.
588 lru = active + page_lru_base_type(page);
589 lru_cache_add_lru(page, lru);
592 * Put unevictable pages directly on zone's unevictable
595 lru = LRU_UNEVICTABLE;
596 add_page_to_unevictable_list(page);
598 * When racing with an mlock clearing (page is
599 * unlocked), make sure that if the other thread does
600 * not observe our setting of PG_lru and fails
601 * isolation, we see PG_mlocked cleared below and move
602 * the page back to the evictable list.
604 * The other side is TestClearPageMlocked().
610 * page's status can change while we move it among lru. If an evictable
611 * page is on unevictable list, it never be freed. To avoid that,
612 * check after we added it to the list, again.
614 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
615 if (!isolate_lru_page(page)) {
619 /* This means someone else dropped this page from LRU
620 * So, it will be freed or putback to LRU again. There is
621 * nothing to do here.
625 if (was_unevictable && lru != LRU_UNEVICTABLE)
626 count_vm_event(UNEVICTABLE_PGRESCUED);
627 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
628 count_vm_event(UNEVICTABLE_PGCULLED);
630 put_page(page); /* drop ref from isolate */
633 enum page_references {
635 PAGEREF_RECLAIM_CLEAN,
640 static enum page_references page_check_references(struct page *page,
641 struct scan_control *sc)
643 int referenced_ptes, referenced_page;
644 unsigned long vm_flags;
646 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
647 referenced_page = TestClearPageReferenced(page);
649 /* Lumpy reclaim - ignore references */
650 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
651 return PAGEREF_RECLAIM;
654 * Mlock lost the isolation race with us. Let try_to_unmap()
655 * move the page to the unevictable list.
657 if (vm_flags & VM_LOCKED)
658 return PAGEREF_RECLAIM;
660 if (referenced_ptes) {
662 return PAGEREF_ACTIVATE;
664 * All mapped pages start out with page table
665 * references from the instantiating fault, so we need
666 * to look twice if a mapped file page is used more
669 * Mark it and spare it for another trip around the
670 * inactive list. Another page table reference will
671 * lead to its activation.
673 * Note: the mark is set for activated pages as well
674 * so that recently deactivated but used pages are
677 SetPageReferenced(page);
680 return PAGEREF_ACTIVATE;
685 /* Reclaim if clean, defer dirty pages to writeback */
686 if (referenced_page && !PageSwapBacked(page))
687 return PAGEREF_RECLAIM_CLEAN;
689 return PAGEREF_RECLAIM;
692 static noinline_for_stack void free_page_list(struct list_head *free_pages)
694 struct pagevec freed_pvec;
695 struct page *page, *tmp;
697 pagevec_init(&freed_pvec, 1);
699 list_for_each_entry_safe(page, tmp, free_pages, lru) {
700 list_del(&page->lru);
701 if (!pagevec_add(&freed_pvec, page)) {
702 __pagevec_free(&freed_pvec);
703 pagevec_reinit(&freed_pvec);
707 pagevec_free(&freed_pvec);
711 * shrink_page_list() returns the number of reclaimed pages
713 static unsigned long shrink_page_list(struct list_head *page_list,
715 struct scan_control *sc)
717 LIST_HEAD(ret_pages);
718 LIST_HEAD(free_pages);
720 unsigned long nr_dirty = 0;
721 unsigned long nr_congested = 0;
722 unsigned long nr_reclaimed = 0;
726 while (!list_empty(page_list)) {
727 enum page_references references;
728 struct address_space *mapping;
734 page = lru_to_page(page_list);
735 list_del(&page->lru);
737 if (!trylock_page(page))
740 VM_BUG_ON(PageActive(page));
741 VM_BUG_ON(page_zone(page) != zone);
745 if (unlikely(!page_evictable(page, NULL)))
748 if (!sc->may_unmap && page_mapped(page))
751 /* Double the slab pressure for mapped and swapcache pages */
752 if (page_mapped(page) || PageSwapCache(page))
755 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
756 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
758 if (PageWriteback(page)) {
760 * Synchronous reclaim is performed in two passes,
761 * first an asynchronous pass over the list to
762 * start parallel writeback, and a second synchronous
763 * pass to wait for the IO to complete. Wait here
764 * for any page for which writeback has already
767 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
769 wait_on_page_writeback(page);
776 references = page_check_references(page, sc);
777 switch (references) {
778 case PAGEREF_ACTIVATE:
779 goto activate_locked;
782 case PAGEREF_RECLAIM:
783 case PAGEREF_RECLAIM_CLEAN:
784 ; /* try to reclaim the page below */
788 * Anonymous process memory has backing store?
789 * Try to allocate it some swap space here.
791 if (PageAnon(page) && !PageSwapCache(page)) {
792 if (!(sc->gfp_mask & __GFP_IO))
794 if (!add_to_swap(page))
795 goto activate_locked;
799 mapping = page_mapping(page);
802 * The page is mapped into the page tables of one or more
803 * processes. Try to unmap it here.
805 if (page_mapped(page) && mapping) {
806 switch (try_to_unmap(page, TTU_UNMAP)) {
808 goto activate_locked;
814 ; /* try to free the page below */
818 if (PageDirty(page)) {
821 if (references == PAGEREF_RECLAIM_CLEAN)
825 if (!sc->may_writepage)
828 /* Page is dirty, try to write it out here */
829 switch (pageout(page, mapping, sc)) {
834 goto activate_locked;
836 if (PageWriteback(page))
842 * A synchronous write - probably a ramdisk. Go
843 * ahead and try to reclaim the page.
845 if (!trylock_page(page))
847 if (PageDirty(page) || PageWriteback(page))
849 mapping = page_mapping(page);
851 ; /* try to free the page below */
856 * If the page has buffers, try to free the buffer mappings
857 * associated with this page. If we succeed we try to free
860 * We do this even if the page is PageDirty().
861 * try_to_release_page() does not perform I/O, but it is
862 * possible for a page to have PageDirty set, but it is actually
863 * clean (all its buffers are clean). This happens if the
864 * buffers were written out directly, with submit_bh(). ext3
865 * will do this, as well as the blockdev mapping.
866 * try_to_release_page() will discover that cleanness and will
867 * drop the buffers and mark the page clean - it can be freed.
869 * Rarely, pages can have buffers and no ->mapping. These are
870 * the pages which were not successfully invalidated in
871 * truncate_complete_page(). We try to drop those buffers here
872 * and if that worked, and the page is no longer mapped into
873 * process address space (page_count == 1) it can be freed.
874 * Otherwise, leave the page on the LRU so it is swappable.
876 if (page_has_private(page)) {
877 if (!try_to_release_page(page, sc->gfp_mask))
878 goto activate_locked;
879 if (!mapping && page_count(page) == 1) {
881 if (put_page_testzero(page))
885 * rare race with speculative reference.
886 * the speculative reference will free
887 * this page shortly, so we may
888 * increment nr_reclaimed here (and
889 * leave it off the LRU).
897 if (!mapping || !__remove_mapping(mapping, page))
901 * At this point, we have no other references and there is
902 * no way to pick any more up (removed from LRU, removed
903 * from pagecache). Can use non-atomic bitops now (and
904 * we obviously don't have to worry about waking up a process
905 * waiting on the page lock, because there are no references.
907 __clear_page_locked(page);
912 * Is there need to periodically free_page_list? It would
913 * appear not as the counts should be low
915 list_add(&page->lru, &free_pages);
919 if (PageSwapCache(page))
920 try_to_free_swap(page);
922 putback_lru_page(page);
923 reset_reclaim_mode(sc);
927 /* Not a candidate for swapping, so reclaim swap space. */
928 if (PageSwapCache(page) && vm_swap_full())
929 try_to_free_swap(page);
930 VM_BUG_ON(PageActive(page));
936 reset_reclaim_mode(sc);
938 list_add(&page->lru, &ret_pages);
939 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
943 * Tag a zone as congested if all the dirty pages encountered were
944 * backed by a congested BDI. In this case, reclaimers should just
945 * back off and wait for congestion to clear because further reclaim
946 * will encounter the same problem
948 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
949 zone_set_flag(zone, ZONE_CONGESTED);
951 free_page_list(&free_pages);
953 list_splice(&ret_pages, page_list);
954 count_vm_events(PGACTIVATE, pgactivate);
959 * Attempt to remove the specified page from its LRU. Only take this page
960 * if it is of the appropriate PageActive status. Pages which are being
961 * freed elsewhere are also ignored.
963 * page: page to consider
964 * mode: one of the LRU isolation modes defined above
966 * returns 0 on success, -ve errno on failure.
968 int __isolate_lru_page(struct page *page, int mode, int file)
972 /* Only take pages on the LRU. */
977 * When checking the active state, we need to be sure we are
978 * dealing with comparible boolean values. Take the logical not
981 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
984 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
988 * When this function is being called for lumpy reclaim, we
989 * initially look into all LRU pages, active, inactive and
990 * unevictable; only give shrink_page_list evictable pages.
992 if (PageUnevictable(page))
997 if (likely(get_page_unless_zero(page))) {
999 * Be careful not to clear PageLRU until after we're
1000 * sure the page is not being freed elsewhere -- the
1001 * page release code relies on it.
1011 * zone->lru_lock is heavily contended. Some of the functions that
1012 * shrink the lists perform better by taking out a batch of pages
1013 * and working on them outside the LRU lock.
1015 * For pagecache intensive workloads, this function is the hottest
1016 * spot in the kernel (apart from copy_*_user functions).
1018 * Appropriate locks must be held before calling this function.
1020 * @nr_to_scan: The number of pages to look through on the list.
1021 * @src: The LRU list to pull pages off.
1022 * @dst: The temp list to put pages on to.
1023 * @scanned: The number of pages that were scanned.
1024 * @order: The caller's attempted allocation order
1025 * @mode: One of the LRU isolation modes
1026 * @file: True [1] if isolating file [!anon] pages
1028 * returns how many pages were moved onto *@dst.
1030 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1031 struct list_head *src, struct list_head *dst,
1032 unsigned long *scanned, int order, int mode, int file)
1034 unsigned long nr_taken = 0;
1035 unsigned long nr_lumpy_taken = 0;
1036 unsigned long nr_lumpy_dirty = 0;
1037 unsigned long nr_lumpy_failed = 0;
1040 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1043 unsigned long end_pfn;
1044 unsigned long page_pfn;
1047 page = lru_to_page(src);
1048 prefetchw_prev_lru_page(page, src, flags);
1050 VM_BUG_ON(!PageLRU(page));
1052 switch (__isolate_lru_page(page, mode, file)) {
1054 list_move(&page->lru, dst);
1055 mem_cgroup_del_lru(page);
1056 nr_taken += hpage_nr_pages(page);
1060 /* else it is being freed elsewhere */
1061 list_move(&page->lru, src);
1062 mem_cgroup_rotate_lru_list(page, page_lru(page));
1073 * Attempt to take all pages in the order aligned region
1074 * surrounding the tag page. Only take those pages of
1075 * the same active state as that tag page. We may safely
1076 * round the target page pfn down to the requested order
1077 * as the mem_map is guaranteed valid out to MAX_ORDER,
1078 * where that page is in a different zone we will detect
1079 * it from its zone id and abort this block scan.
1081 zone_id = page_zone_id(page);
1082 page_pfn = page_to_pfn(page);
1083 pfn = page_pfn & ~((1 << order) - 1);
1084 end_pfn = pfn + (1 << order);
1085 for (; pfn < end_pfn; pfn++) {
1086 struct page *cursor_page;
1088 /* The target page is in the block, ignore it. */
1089 if (unlikely(pfn == page_pfn))
1092 /* Avoid holes within the zone. */
1093 if (unlikely(!pfn_valid_within(pfn)))
1096 cursor_page = pfn_to_page(pfn);
1098 /* Check that we have not crossed a zone boundary. */
1099 if (unlikely(page_zone_id(cursor_page) != zone_id))
1103 * If we don't have enough swap space, reclaiming of
1104 * anon page which don't already have a swap slot is
1107 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1108 !PageSwapCache(cursor_page))
1111 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1112 list_move(&cursor_page->lru, dst);
1113 mem_cgroup_del_lru(cursor_page);
1114 nr_taken += hpage_nr_pages(page);
1116 if (PageDirty(cursor_page))
1120 /* the page is freed already. */
1121 if (!page_count(cursor_page))
1127 /* If we break out of the loop above, lumpy reclaim failed */
1134 trace_mm_vmscan_lru_isolate(order,
1137 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1142 static unsigned long isolate_pages_global(unsigned long nr,
1143 struct list_head *dst,
1144 unsigned long *scanned, int order,
1145 int mode, struct zone *z,
1146 int active, int file)
1153 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1158 * clear_active_flags() is a helper for shrink_active_list(), clearing
1159 * any active bits from the pages in the list.
1161 static unsigned long clear_active_flags(struct list_head *page_list,
1162 unsigned int *count)
1168 list_for_each_entry(page, page_list, lru) {
1169 int numpages = hpage_nr_pages(page);
1170 lru = page_lru_base_type(page);
1171 if (PageActive(page)) {
1173 ClearPageActive(page);
1174 nr_active += numpages;
1177 count[lru] += numpages;
1184 * isolate_lru_page - tries to isolate a page from its LRU list
1185 * @page: page to isolate from its LRU list
1187 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1188 * vmstat statistic corresponding to whatever LRU list the page was on.
1190 * Returns 0 if the page was removed from an LRU list.
1191 * Returns -EBUSY if the page was not on an LRU list.
1193 * The returned page will have PageLRU() cleared. If it was found on
1194 * the active list, it will have PageActive set. If it was found on
1195 * the unevictable list, it will have the PageUnevictable bit set. That flag
1196 * may need to be cleared by the caller before letting the page go.
1198 * The vmstat statistic corresponding to the list on which the page was
1199 * found will be decremented.
1202 * (1) Must be called with an elevated refcount on the page. This is a
1203 * fundamentnal difference from isolate_lru_pages (which is called
1204 * without a stable reference).
1205 * (2) the lru_lock must not be held.
1206 * (3) interrupts must be enabled.
1208 int isolate_lru_page(struct page *page)
1212 VM_BUG_ON(!page_count(page));
1214 if (PageLRU(page)) {
1215 struct zone *zone = page_zone(page);
1217 spin_lock_irq(&zone->lru_lock);
1218 if (PageLRU(page)) {
1219 int lru = page_lru(page);
1224 del_page_from_lru_list(zone, page, lru);
1226 spin_unlock_irq(&zone->lru_lock);
1232 * Are there way too many processes in the direct reclaim path already?
1234 static int too_many_isolated(struct zone *zone, int file,
1235 struct scan_control *sc)
1237 unsigned long inactive, isolated;
1239 if (current_is_kswapd())
1242 if (!scanning_global_lru(sc))
1246 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1247 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1249 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1250 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1253 return isolated > inactive;
1257 * TODO: Try merging with migrations version of putback_lru_pages
1259 static noinline_for_stack void
1260 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1261 unsigned long nr_anon, unsigned long nr_file,
1262 struct list_head *page_list)
1265 struct pagevec pvec;
1266 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1268 pagevec_init(&pvec, 1);
1271 * Put back any unfreeable pages.
1273 spin_lock(&zone->lru_lock);
1274 while (!list_empty(page_list)) {
1276 page = lru_to_page(page_list);
1277 VM_BUG_ON(PageLRU(page));
1278 list_del(&page->lru);
1279 if (unlikely(!page_evictable(page, NULL))) {
1280 spin_unlock_irq(&zone->lru_lock);
1281 putback_lru_page(page);
1282 spin_lock_irq(&zone->lru_lock);
1286 lru = page_lru(page);
1287 add_page_to_lru_list(zone, page, lru);
1288 if (is_active_lru(lru)) {
1289 int file = is_file_lru(lru);
1290 int numpages = hpage_nr_pages(page);
1291 reclaim_stat->recent_rotated[file] += numpages;
1293 if (!pagevec_add(&pvec, page)) {
1294 spin_unlock_irq(&zone->lru_lock);
1295 __pagevec_release(&pvec);
1296 spin_lock_irq(&zone->lru_lock);
1299 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1300 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1302 spin_unlock_irq(&zone->lru_lock);
1303 pagevec_release(&pvec);
1306 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1307 struct scan_control *sc,
1308 unsigned long *nr_anon,
1309 unsigned long *nr_file,
1310 struct list_head *isolated_list)
1312 unsigned long nr_active;
1313 unsigned int count[NR_LRU_LISTS] = { 0, };
1314 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1316 nr_active = clear_active_flags(isolated_list, count);
1317 __count_vm_events(PGDEACTIVATE, nr_active);
1319 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1320 -count[LRU_ACTIVE_FILE]);
1321 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1322 -count[LRU_INACTIVE_FILE]);
1323 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1324 -count[LRU_ACTIVE_ANON]);
1325 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1326 -count[LRU_INACTIVE_ANON]);
1328 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1329 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1330 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1331 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1333 reclaim_stat->recent_scanned[0] += *nr_anon;
1334 reclaim_stat->recent_scanned[1] += *nr_file;
1338 * Returns true if the caller should wait to clean dirty/writeback pages.
1340 * If we are direct reclaiming for contiguous pages and we do not reclaim
1341 * everything in the list, try again and wait for writeback IO to complete.
1342 * This will stall high-order allocations noticeably. Only do that when really
1343 * need to free the pages under high memory pressure.
1345 static inline bool should_reclaim_stall(unsigned long nr_taken,
1346 unsigned long nr_freed,
1348 struct scan_control *sc)
1350 int lumpy_stall_priority;
1352 /* kswapd should not stall on sync IO */
1353 if (current_is_kswapd())
1356 /* Only stall on lumpy reclaim */
1357 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1360 /* If we have relaimed everything on the isolated list, no stall */
1361 if (nr_freed == nr_taken)
1365 * For high-order allocations, there are two stall thresholds.
1366 * High-cost allocations stall immediately where as lower
1367 * order allocations such as stacks require the scanning
1368 * priority to be much higher before stalling.
1370 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1371 lumpy_stall_priority = DEF_PRIORITY;
1373 lumpy_stall_priority = DEF_PRIORITY / 3;
1375 return priority <= lumpy_stall_priority;
1379 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1380 * of reclaimed pages
1382 static noinline_for_stack unsigned long
1383 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1384 struct scan_control *sc, int priority, int file)
1386 LIST_HEAD(page_list);
1387 unsigned long nr_scanned;
1388 unsigned long nr_reclaimed = 0;
1389 unsigned long nr_taken;
1390 unsigned long nr_anon;
1391 unsigned long nr_file;
1393 while (unlikely(too_many_isolated(zone, file, sc))) {
1394 congestion_wait(BLK_RW_ASYNC, HZ/10);
1396 /* We are about to die and free our memory. Return now. */
1397 if (fatal_signal_pending(current))
1398 return SWAP_CLUSTER_MAX;
1401 set_reclaim_mode(priority, sc, false);
1403 spin_lock_irq(&zone->lru_lock);
1405 if (scanning_global_lru(sc)) {
1406 nr_taken = isolate_pages_global(nr_to_scan,
1407 &page_list, &nr_scanned, sc->order,
1408 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1409 ISOLATE_BOTH : ISOLATE_INACTIVE,
1411 zone->pages_scanned += nr_scanned;
1412 if (current_is_kswapd())
1413 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1416 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1419 nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
1420 &page_list, &nr_scanned, sc->order,
1421 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1422 ISOLATE_BOTH : ISOLATE_INACTIVE,
1423 zone, sc->mem_cgroup,
1426 * mem_cgroup_isolate_pages() keeps track of
1427 * scanned pages on its own.
1431 if (nr_taken == 0) {
1432 spin_unlock_irq(&zone->lru_lock);
1436 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1438 spin_unlock_irq(&zone->lru_lock);
1440 nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1442 /* Check if we should syncronously wait for writeback */
1443 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1444 set_reclaim_mode(priority, sc, true);
1445 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1448 local_irq_disable();
1449 if (current_is_kswapd())
1450 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1451 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1453 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1455 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1457 nr_scanned, nr_reclaimed,
1459 trace_shrink_flags(file, sc->reclaim_mode));
1460 return nr_reclaimed;
1464 * This moves pages from the active list to the inactive list.
1466 * We move them the other way if the page is referenced by one or more
1467 * processes, from rmap.
1469 * If the pages are mostly unmapped, the processing is fast and it is
1470 * appropriate to hold zone->lru_lock across the whole operation. But if
1471 * the pages are mapped, the processing is slow (page_referenced()) so we
1472 * should drop zone->lru_lock around each page. It's impossible to balance
1473 * this, so instead we remove the pages from the LRU while processing them.
1474 * It is safe to rely on PG_active against the non-LRU pages in here because
1475 * nobody will play with that bit on a non-LRU page.
1477 * The downside is that we have to touch page->_count against each page.
1478 * But we had to alter page->flags anyway.
1481 static void move_active_pages_to_lru(struct zone *zone,
1482 struct list_head *list,
1485 unsigned long pgmoved = 0;
1486 struct pagevec pvec;
1489 pagevec_init(&pvec, 1);
1491 while (!list_empty(list)) {
1492 page = lru_to_page(list);
1494 VM_BUG_ON(PageLRU(page));
1497 list_move(&page->lru, &zone->lru[lru].list);
1498 mem_cgroup_add_lru_list(page, lru);
1499 pgmoved += hpage_nr_pages(page);
1501 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1502 spin_unlock_irq(&zone->lru_lock);
1503 if (buffer_heads_over_limit)
1504 pagevec_strip(&pvec);
1505 __pagevec_release(&pvec);
1506 spin_lock_irq(&zone->lru_lock);
1509 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1510 if (!is_active_lru(lru))
1511 __count_vm_events(PGDEACTIVATE, pgmoved);
1514 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1515 struct scan_control *sc, int priority, int file)
1517 unsigned long nr_taken;
1518 unsigned long pgscanned;
1519 unsigned long vm_flags;
1520 LIST_HEAD(l_hold); /* The pages which were snipped off */
1521 LIST_HEAD(l_active);
1522 LIST_HEAD(l_inactive);
1524 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1525 unsigned long nr_rotated = 0;
1528 spin_lock_irq(&zone->lru_lock);
1529 if (scanning_global_lru(sc)) {
1530 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1531 &pgscanned, sc->order,
1532 ISOLATE_ACTIVE, zone,
1534 zone->pages_scanned += pgscanned;
1536 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1537 &pgscanned, sc->order,
1538 ISOLATE_ACTIVE, zone,
1539 sc->mem_cgroup, 1, file);
1541 * mem_cgroup_isolate_pages() keeps track of
1542 * scanned pages on its own.
1546 reclaim_stat->recent_scanned[file] += nr_taken;
1548 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1550 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1552 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1553 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1554 spin_unlock_irq(&zone->lru_lock);
1556 while (!list_empty(&l_hold)) {
1558 page = lru_to_page(&l_hold);
1559 list_del(&page->lru);
1561 if (unlikely(!page_evictable(page, NULL))) {
1562 putback_lru_page(page);
1566 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1567 nr_rotated += hpage_nr_pages(page);
1569 * Identify referenced, file-backed active pages and
1570 * give them one more trip around the active list. So
1571 * that executable code get better chances to stay in
1572 * memory under moderate memory pressure. Anon pages
1573 * are not likely to be evicted by use-once streaming
1574 * IO, plus JVM can create lots of anon VM_EXEC pages,
1575 * so we ignore them here.
1577 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1578 list_add(&page->lru, &l_active);
1583 ClearPageActive(page); /* we are de-activating */
1584 list_add(&page->lru, &l_inactive);
1588 * Move pages back to the lru list.
1590 spin_lock_irq(&zone->lru_lock);
1592 * Count referenced pages from currently used mappings as rotated,
1593 * even though only some of them are actually re-activated. This
1594 * helps balance scan pressure between file and anonymous pages in
1597 reclaim_stat->recent_rotated[file] += nr_rotated;
1599 move_active_pages_to_lru(zone, &l_active,
1600 LRU_ACTIVE + file * LRU_FILE);
1601 move_active_pages_to_lru(zone, &l_inactive,
1602 LRU_BASE + file * LRU_FILE);
1603 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1604 spin_unlock_irq(&zone->lru_lock);
1608 static int inactive_anon_is_low_global(struct zone *zone)
1610 unsigned long active, inactive;
1612 active = zone_page_state(zone, NR_ACTIVE_ANON);
1613 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1615 if (inactive * zone->inactive_ratio < active)
1622 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1623 * @zone: zone to check
1624 * @sc: scan control of this context
1626 * Returns true if the zone does not have enough inactive anon pages,
1627 * meaning some active anon pages need to be deactivated.
1629 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1634 * If we don't have swap space, anonymous page deactivation
1637 if (!total_swap_pages)
1640 if (scanning_global_lru(sc))
1641 low = inactive_anon_is_low_global(zone);
1643 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1647 static inline int inactive_anon_is_low(struct zone *zone,
1648 struct scan_control *sc)
1654 static int inactive_file_is_low_global(struct zone *zone)
1656 unsigned long active, inactive;
1658 active = zone_page_state(zone, NR_ACTIVE_FILE);
1659 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1661 return (active > inactive);
1665 * inactive_file_is_low - check if file pages need to be deactivated
1666 * @zone: zone to check
1667 * @sc: scan control of this context
1669 * When the system is doing streaming IO, memory pressure here
1670 * ensures that active file pages get deactivated, until more
1671 * than half of the file pages are on the inactive list.
1673 * Once we get to that situation, protect the system's working
1674 * set from being evicted by disabling active file page aging.
1676 * This uses a different ratio than the anonymous pages, because
1677 * the page cache uses a use-once replacement algorithm.
1679 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1683 if (scanning_global_lru(sc))
1684 low = inactive_file_is_low_global(zone);
1686 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1690 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1694 return inactive_file_is_low(zone, sc);
1696 return inactive_anon_is_low(zone, sc);
1699 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1700 struct zone *zone, struct scan_control *sc, int priority)
1702 int file = is_file_lru(lru);
1704 if (is_active_lru(lru)) {
1705 if (inactive_list_is_low(zone, sc, file))
1706 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1710 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1714 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1715 * until we collected @swap_cluster_max pages to scan.
1717 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1718 unsigned long *nr_saved_scan)
1722 *nr_saved_scan += nr_to_scan;
1723 nr = *nr_saved_scan;
1725 if (nr >= SWAP_CLUSTER_MAX)
1734 * Determine how aggressively the anon and file LRU lists should be
1735 * scanned. The relative value of each set of LRU lists is determined
1736 * by looking at the fraction of the pages scanned we did rotate back
1737 * onto the active list instead of evict.
1739 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1741 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1742 unsigned long *nr, int priority)
1744 unsigned long anon, file, free;
1745 unsigned long anon_prio, file_prio;
1746 unsigned long ap, fp;
1747 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1748 u64 fraction[2], denominator;
1752 /* If we have no swap space, do not bother scanning anon pages. */
1753 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1761 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1762 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1763 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1764 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1766 if (scanning_global_lru(sc)) {
1767 free = zone_page_state(zone, NR_FREE_PAGES);
1768 /* If we have very few page cache pages,
1769 force-scan anon pages. */
1770 if (unlikely(file + free <= high_wmark_pages(zone))) {
1779 * With swappiness at 100, anonymous and file have the same priority.
1780 * This scanning priority is essentially the inverse of IO cost.
1782 anon_prio = sc->swappiness;
1783 file_prio = 200 - sc->swappiness;
1786 * OK, so we have swap space and a fair amount of page cache
1787 * pages. We use the recently rotated / recently scanned
1788 * ratios to determine how valuable each cache is.
1790 * Because workloads change over time (and to avoid overflow)
1791 * we keep these statistics as a floating average, which ends
1792 * up weighing recent references more than old ones.
1794 * anon in [0], file in [1]
1796 spin_lock_irq(&zone->lru_lock);
1797 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1798 reclaim_stat->recent_scanned[0] /= 2;
1799 reclaim_stat->recent_rotated[0] /= 2;
1802 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1803 reclaim_stat->recent_scanned[1] /= 2;
1804 reclaim_stat->recent_rotated[1] /= 2;
1808 * The amount of pressure on anon vs file pages is inversely
1809 * proportional to the fraction of recently scanned pages on
1810 * each list that were recently referenced and in active use.
1812 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1813 ap /= reclaim_stat->recent_rotated[0] + 1;
1815 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1816 fp /= reclaim_stat->recent_rotated[1] + 1;
1817 spin_unlock_irq(&zone->lru_lock);
1821 denominator = ap + fp + 1;
1823 for_each_evictable_lru(l) {
1824 int file = is_file_lru(l);
1827 scan = zone_nr_lru_pages(zone, sc, l);
1828 if (priority || noswap) {
1830 scan = div64_u64(scan * fraction[file], denominator);
1832 nr[l] = nr_scan_try_batch(scan,
1833 &reclaim_stat->nr_saved_scan[l]);
1838 * Reclaim/compaction depends on a number of pages being freed. To avoid
1839 * disruption to the system, a small number of order-0 pages continue to be
1840 * rotated and reclaimed in the normal fashion. However, by the time we get
1841 * back to the allocator and call try_to_compact_zone(), we ensure that
1842 * there are enough free pages for it to be likely successful
1844 static inline bool should_continue_reclaim(struct zone *zone,
1845 unsigned long nr_reclaimed,
1846 unsigned long nr_scanned,
1847 struct scan_control *sc)
1849 unsigned long pages_for_compaction;
1850 unsigned long inactive_lru_pages;
1852 /* If not in reclaim/compaction mode, stop */
1853 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1856 /* Consider stopping depending on scan and reclaim activity */
1857 if (sc->gfp_mask & __GFP_REPEAT) {
1859 * For __GFP_REPEAT allocations, stop reclaiming if the
1860 * full LRU list has been scanned and we are still failing
1861 * to reclaim pages. This full LRU scan is potentially
1862 * expensive but a __GFP_REPEAT caller really wants to succeed
1864 if (!nr_reclaimed && !nr_scanned)
1868 * For non-__GFP_REPEAT allocations which can presumably
1869 * fail without consequence, stop if we failed to reclaim
1870 * any pages from the last SWAP_CLUSTER_MAX number of
1871 * pages that were scanned. This will return to the
1872 * caller faster at the risk reclaim/compaction and
1873 * the resulting allocation attempt fails
1880 * If we have not reclaimed enough pages for compaction and the
1881 * inactive lists are large enough, continue reclaiming
1883 pages_for_compaction = (2UL << sc->order);
1884 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
1885 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1886 if (sc->nr_reclaimed < pages_for_compaction &&
1887 inactive_lru_pages > pages_for_compaction)
1890 /* If compaction would go ahead or the allocation would succeed, stop */
1891 switch (compaction_suitable(zone, sc->order)) {
1892 case COMPACT_PARTIAL:
1893 case COMPACT_CONTINUE:
1901 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1903 static void shrink_zone(int priority, struct zone *zone,
1904 struct scan_control *sc)
1906 unsigned long nr[NR_LRU_LISTS];
1907 unsigned long nr_to_scan;
1909 unsigned long nr_reclaimed, nr_scanned;
1910 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1914 nr_scanned = sc->nr_scanned;
1915 get_scan_count(zone, sc, nr, priority);
1917 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1918 nr[LRU_INACTIVE_FILE]) {
1919 for_each_evictable_lru(l) {
1921 nr_to_scan = min_t(unsigned long,
1922 nr[l], SWAP_CLUSTER_MAX);
1923 nr[l] -= nr_to_scan;
1925 nr_reclaimed += shrink_list(l, nr_to_scan,
1926 zone, sc, priority);
1930 * On large memory systems, scan >> priority can become
1931 * really large. This is fine for the starting priority;
1932 * we want to put equal scanning pressure on each zone.
1933 * However, if the VM has a harder time of freeing pages,
1934 * with multiple processes reclaiming pages, the total
1935 * freeing target can get unreasonably large.
1937 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1940 sc->nr_reclaimed += nr_reclaimed;
1943 * Even if we did not try to evict anon pages at all, we want to
1944 * rebalance the anon lru active/inactive ratio.
1946 if (inactive_anon_is_low(zone, sc))
1947 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1949 /* reclaim/compaction might need reclaim to continue */
1950 if (should_continue_reclaim(zone, nr_reclaimed,
1951 sc->nr_scanned - nr_scanned, sc))
1954 throttle_vm_writeout(sc->gfp_mask);
1958 * This is the direct reclaim path, for page-allocating processes. We only
1959 * try to reclaim pages from zones which will satisfy the caller's allocation
1962 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1964 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1966 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1967 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1968 * zone defense algorithm.
1970 * If a zone is deemed to be full of pinned pages then just give it a light
1971 * scan then give up on it.
1973 static void shrink_zones(int priority, struct zonelist *zonelist,
1974 struct scan_control *sc)
1979 for_each_zone_zonelist_nodemask(zone, z, zonelist,
1980 gfp_zone(sc->gfp_mask), sc->nodemask) {
1981 if (!populated_zone(zone))
1984 * Take care memory controller reclaiming has small influence
1987 if (scanning_global_lru(sc)) {
1988 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1990 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1991 continue; /* Let kswapd poll it */
1994 shrink_zone(priority, zone, sc);
1998 static bool zone_reclaimable(struct zone *zone)
2000 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2003 /* All zones in zonelist are unreclaimable? */
2004 static bool all_unreclaimable(struct zonelist *zonelist,
2005 struct scan_control *sc)
2010 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2011 gfp_zone(sc->gfp_mask), sc->nodemask) {
2012 if (!populated_zone(zone))
2014 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2016 if (!zone->all_unreclaimable)
2024 * This is the main entry point to direct page reclaim.
2026 * If a full scan of the inactive list fails to free enough memory then we
2027 * are "out of memory" and something needs to be killed.
2029 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2030 * high - the zone may be full of dirty or under-writeback pages, which this
2031 * caller can't do much about. We kick the writeback threads and take explicit
2032 * naps in the hope that some of these pages can be written. But if the
2033 * allocating task holds filesystem locks which prevent writeout this might not
2034 * work, and the allocation attempt will fail.
2036 * returns: 0, if no pages reclaimed
2037 * else, the number of pages reclaimed
2039 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2040 struct scan_control *sc,
2041 struct shrink_control *shrink)
2044 unsigned long total_scanned = 0;
2045 struct reclaim_state *reclaim_state = current->reclaim_state;
2048 unsigned long writeback_threshold;
2051 delayacct_freepages_start();
2053 if (scanning_global_lru(sc))
2054 count_vm_event(ALLOCSTALL);
2056 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2059 disable_swap_token();
2060 shrink_zones(priority, zonelist, sc);
2062 * Don't shrink slabs when reclaiming memory from
2063 * over limit cgroups
2065 if (scanning_global_lru(sc)) {
2066 unsigned long lru_pages = 0;
2067 for_each_zone_zonelist(zone, z, zonelist,
2068 gfp_zone(sc->gfp_mask)) {
2069 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2072 lru_pages += zone_reclaimable_pages(zone);
2075 shrink->nr_scanned = sc->nr_scanned;
2076 shrink_slab(shrink, lru_pages);
2077 if (reclaim_state) {
2078 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2079 reclaim_state->reclaimed_slab = 0;
2082 total_scanned += sc->nr_scanned;
2083 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2087 * Try to write back as many pages as we just scanned. This
2088 * tends to cause slow streaming writers to write data to the
2089 * disk smoothly, at the dirtying rate, which is nice. But
2090 * that's undesirable in laptop mode, where we *want* lumpy
2091 * writeout. So in laptop mode, write out the whole world.
2093 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2094 if (total_scanned > writeback_threshold) {
2095 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2096 sc->may_writepage = 1;
2099 /* Take a nap, wait for some writeback to complete */
2100 if (!sc->hibernation_mode && sc->nr_scanned &&
2101 priority < DEF_PRIORITY - 2) {
2102 struct zone *preferred_zone;
2104 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2105 &cpuset_current_mems_allowed,
2107 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2112 delayacct_freepages_end();
2115 if (sc->nr_reclaimed)
2116 return sc->nr_reclaimed;
2119 * As hibernation is going on, kswapd is freezed so that it can't mark
2120 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2123 if (oom_killer_disabled)
2126 /* top priority shrink_zones still had more to do? don't OOM, then */
2127 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2133 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2134 gfp_t gfp_mask, nodemask_t *nodemask)
2136 unsigned long nr_reclaimed;
2137 struct scan_control sc = {
2138 .gfp_mask = gfp_mask,
2139 .may_writepage = !laptop_mode,
2140 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2143 .swappiness = vm_swappiness,
2146 .nodemask = nodemask,
2148 struct shrink_control shrink = {
2149 .gfp_mask = sc.gfp_mask,
2152 trace_mm_vmscan_direct_reclaim_begin(order,
2156 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2158 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2160 return nr_reclaimed;
2163 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2165 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2166 gfp_t gfp_mask, bool noswap,
2167 unsigned int swappiness,
2170 struct scan_control sc = {
2171 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2172 .may_writepage = !laptop_mode,
2174 .may_swap = !noswap,
2175 .swappiness = swappiness,
2179 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2180 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2182 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2187 * NOTE: Although we can get the priority field, using it
2188 * here is not a good idea, since it limits the pages we can scan.
2189 * if we don't reclaim here, the shrink_zone from balance_pgdat
2190 * will pick up pages from other mem cgroup's as well. We hack
2191 * the priority and make it zero.
2193 shrink_zone(0, zone, &sc);
2195 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2197 return sc.nr_reclaimed;
2200 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2203 unsigned int swappiness)
2205 struct zonelist *zonelist;
2206 unsigned long nr_reclaimed;
2207 struct scan_control sc = {
2208 .may_writepage = !laptop_mode,
2210 .may_swap = !noswap,
2211 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2212 .swappiness = swappiness,
2214 .mem_cgroup = mem_cont,
2215 .nodemask = NULL, /* we don't care the placement */
2216 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2217 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2219 struct shrink_control shrink = {
2220 .gfp_mask = sc.gfp_mask,
2223 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
2225 trace_mm_vmscan_memcg_reclaim_begin(0,
2229 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2231 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2233 return nr_reclaimed;
2238 * pgdat_balanced is used when checking if a node is balanced for high-order
2239 * allocations. Only zones that meet watermarks and are in a zone allowed
2240 * by the callers classzone_idx are added to balanced_pages. The total of
2241 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2242 * for the node to be considered balanced. Forcing all zones to be balanced
2243 * for high orders can cause excessive reclaim when there are imbalanced zones.
2244 * The choice of 25% is due to
2245 * o a 16M DMA zone that is balanced will not balance a zone on any
2246 * reasonable sized machine
2247 * o On all other machines, the top zone must be at least a reasonable
2248 * percentage of the middle zones. For example, on 32-bit x86, highmem
2249 * would need to be at least 256M for it to be balance a whole node.
2250 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2251 * to balance a node on its own. These seemed like reasonable ratios.
2253 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2256 unsigned long present_pages = 0;
2259 for (i = 0; i <= classzone_idx; i++)
2260 present_pages += pgdat->node_zones[i].present_pages;
2262 return balanced_pages > (present_pages >> 2);
2265 /* is kswapd sleeping prematurely? */
2266 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2270 unsigned long balanced = 0;
2271 bool all_zones_ok = true;
2273 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2277 /* Check the watermark levels */
2278 for (i = 0; i < pgdat->nr_zones; i++) {
2279 struct zone *zone = pgdat->node_zones + i;
2281 if (!populated_zone(zone))
2285 * balance_pgdat() skips over all_unreclaimable after
2286 * DEF_PRIORITY. Effectively, it considers them balanced so
2287 * they must be considered balanced here as well if kswapd
2290 if (zone->all_unreclaimable) {
2291 balanced += zone->present_pages;
2295 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2297 all_zones_ok = false;
2299 balanced += zone->present_pages;
2303 * For high-order requests, the balanced zones must contain at least
2304 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2308 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2310 return !all_zones_ok;
2314 * For kswapd, balance_pgdat() will work across all this node's zones until
2315 * they are all at high_wmark_pages(zone).
2317 * Returns the final order kswapd was reclaiming at
2319 * There is special handling here for zones which are full of pinned pages.
2320 * This can happen if the pages are all mlocked, or if they are all used by
2321 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2322 * What we do is to detect the case where all pages in the zone have been
2323 * scanned twice and there has been zero successful reclaim. Mark the zone as
2324 * dead and from now on, only perform a short scan. Basically we're polling
2325 * the zone for when the problem goes away.
2327 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2328 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2329 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2330 * lower zones regardless of the number of free pages in the lower zones. This
2331 * interoperates with the page allocator fallback scheme to ensure that aging
2332 * of pages is balanced across the zones.
2334 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2338 unsigned long balanced;
2341 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2342 unsigned long total_scanned;
2343 struct reclaim_state *reclaim_state = current->reclaim_state;
2344 struct scan_control sc = {
2345 .gfp_mask = GFP_KERNEL,
2349 * kswapd doesn't want to be bailed out while reclaim. because
2350 * we want to put equal scanning pressure on each zone.
2352 .nr_to_reclaim = ULONG_MAX,
2353 .swappiness = vm_swappiness,
2357 struct shrink_control shrink = {
2358 .gfp_mask = sc.gfp_mask,
2362 sc.nr_reclaimed = 0;
2363 sc.may_writepage = !laptop_mode;
2364 count_vm_event(PAGEOUTRUN);
2366 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2367 unsigned long lru_pages = 0;
2368 int has_under_min_watermark_zone = 0;
2370 /* The swap token gets in the way of swapout... */
2372 disable_swap_token();
2378 * Scan in the highmem->dma direction for the highest
2379 * zone which needs scanning
2381 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2382 struct zone *zone = pgdat->node_zones + i;
2384 if (!populated_zone(zone))
2387 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2391 * Do some background aging of the anon list, to give
2392 * pages a chance to be referenced before reclaiming.
2394 if (inactive_anon_is_low(zone, &sc))
2395 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2398 if (!zone_watermark_ok_safe(zone, order,
2399 high_wmark_pages(zone), 0, 0)) {
2408 for (i = 0; i <= end_zone; i++) {
2409 struct zone *zone = pgdat->node_zones + i;
2411 lru_pages += zone_reclaimable_pages(zone);
2415 * Now scan the zone in the dma->highmem direction, stopping
2416 * at the last zone which needs scanning.
2418 * We do this because the page allocator works in the opposite
2419 * direction. This prevents the page allocator from allocating
2420 * pages behind kswapd's direction of progress, which would
2421 * cause too much scanning of the lower zones.
2423 for (i = 0; i <= end_zone; i++) {
2424 struct zone *zone = pgdat->node_zones + i;
2426 unsigned long balance_gap;
2428 if (!populated_zone(zone))
2431 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2437 * Call soft limit reclaim before calling shrink_zone.
2438 * For now we ignore the return value
2440 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);
2443 * We put equal pressure on every zone, unless
2444 * one zone has way too many pages free
2445 * already. The "too many pages" is defined
2446 * as the high wmark plus a "gap" where the
2447 * gap is either the low watermark or 1%
2448 * of the zone, whichever is smaller.
2450 balance_gap = min(low_wmark_pages(zone),
2451 (zone->present_pages +
2452 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2453 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2454 if (!zone_watermark_ok_safe(zone, order,
2455 high_wmark_pages(zone) + balance_gap,
2457 shrink_zone(priority, zone, &sc);
2458 reclaim_state->reclaimed_slab = 0;
2459 shrink.nr_scanned = sc.nr_scanned;
2460 nr_slab = shrink_slab(&shrink, lru_pages);
2461 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2462 total_scanned += sc.nr_scanned;
2464 if (zone->all_unreclaimable)
2467 !zone_reclaimable(zone))
2468 zone->all_unreclaimable = 1;
2470 * If we've done a decent amount of scanning and
2471 * the reclaim ratio is low, start doing writepage
2472 * even in laptop mode
2474 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2475 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2476 sc.may_writepage = 1;
2478 if (!zone_watermark_ok_safe(zone, order,
2479 high_wmark_pages(zone), end_zone, 0)) {
2482 * We are still under min water mark. This
2483 * means that we have a GFP_ATOMIC allocation
2484 * failure risk. Hurry up!
2486 if (!zone_watermark_ok_safe(zone, order,
2487 min_wmark_pages(zone), end_zone, 0))
2488 has_under_min_watermark_zone = 1;
2491 * If a zone reaches its high watermark,
2492 * consider it to be no longer congested. It's
2493 * possible there are dirty pages backed by
2494 * congested BDIs but as pressure is relieved,
2495 * spectulatively avoid congestion waits
2497 zone_clear_flag(zone, ZONE_CONGESTED);
2498 if (i <= *classzone_idx)
2499 balanced += zone->present_pages;
2503 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2504 break; /* kswapd: all done */
2506 * OK, kswapd is getting into trouble. Take a nap, then take
2507 * another pass across the zones.
2509 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2510 if (has_under_min_watermark_zone)
2511 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2513 congestion_wait(BLK_RW_ASYNC, HZ/10);
2517 * We do this so kswapd doesn't build up large priorities for
2518 * example when it is freeing in parallel with allocators. It
2519 * matches the direct reclaim path behaviour in terms of impact
2520 * on zone->*_priority.
2522 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2528 * order-0: All zones must meet high watermark for a balanced node
2529 * high-order: Balanced zones must make up at least 25% of the node
2530 * for the node to be balanced
2532 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2538 * Fragmentation may mean that the system cannot be
2539 * rebalanced for high-order allocations in all zones.
2540 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2541 * it means the zones have been fully scanned and are still
2542 * not balanced. For high-order allocations, there is
2543 * little point trying all over again as kswapd may
2546 * Instead, recheck all watermarks at order-0 as they
2547 * are the most important. If watermarks are ok, kswapd will go
2548 * back to sleep. High-order users can still perform direct
2549 * reclaim if they wish.
2551 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2552 order = sc.order = 0;
2558 * If kswapd was reclaiming at a higher order, it has the option of
2559 * sleeping without all zones being balanced. Before it does, it must
2560 * ensure that the watermarks for order-0 on *all* zones are met and
2561 * that the congestion flags are cleared. The congestion flag must
2562 * be cleared as kswapd is the only mechanism that clears the flag
2563 * and it is potentially going to sleep here.
2566 for (i = 0; i <= end_zone; i++) {
2567 struct zone *zone = pgdat->node_zones + i;
2569 if (!populated_zone(zone))
2572 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2575 /* Confirm the zone is balanced for order-0 */
2576 if (!zone_watermark_ok(zone, 0,
2577 high_wmark_pages(zone), 0, 0)) {
2578 order = sc.order = 0;
2582 /* If balanced, clear the congested flag */
2583 zone_clear_flag(zone, ZONE_CONGESTED);
2588 * Return the order we were reclaiming at so sleeping_prematurely()
2589 * makes a decision on the order we were last reclaiming at. However,
2590 * if another caller entered the allocator slow path while kswapd
2591 * was awake, order will remain at the higher level
2593 *classzone_idx = end_zone;
2597 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2602 if (freezing(current) || kthread_should_stop())
2605 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2607 /* Try to sleep for a short interval */
2608 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2609 remaining = schedule_timeout(HZ/10);
2610 finish_wait(&pgdat->kswapd_wait, &wait);
2611 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2615 * After a short sleep, check if it was a premature sleep. If not, then
2616 * go fully to sleep until explicitly woken up.
2618 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2619 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2622 * vmstat counters are not perfectly accurate and the estimated
2623 * value for counters such as NR_FREE_PAGES can deviate from the
2624 * true value by nr_online_cpus * threshold. To avoid the zone
2625 * watermarks being breached while under pressure, we reduce the
2626 * per-cpu vmstat threshold while kswapd is awake and restore
2627 * them before going back to sleep.
2629 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2631 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2634 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2636 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2638 finish_wait(&pgdat->kswapd_wait, &wait);
2642 * The background pageout daemon, started as a kernel thread
2643 * from the init process.
2645 * This basically trickles out pages so that we have _some_
2646 * free memory available even if there is no other activity
2647 * that frees anything up. This is needed for things like routing
2648 * etc, where we otherwise might have all activity going on in
2649 * asynchronous contexts that cannot page things out.
2651 * If there are applications that are active memory-allocators
2652 * (most normal use), this basically shouldn't matter.
2654 static int kswapd(void *p)
2656 unsigned long order;
2658 pg_data_t *pgdat = (pg_data_t*)p;
2659 struct task_struct *tsk = current;
2661 struct reclaim_state reclaim_state = {
2662 .reclaimed_slab = 0,
2664 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2666 lockdep_set_current_reclaim_state(GFP_KERNEL);
2668 if (!cpumask_empty(cpumask))
2669 set_cpus_allowed_ptr(tsk, cpumask);
2670 current->reclaim_state = &reclaim_state;
2673 * Tell the memory management that we're a "memory allocator",
2674 * and that if we need more memory we should get access to it
2675 * regardless (see "__alloc_pages()"). "kswapd" should
2676 * never get caught in the normal page freeing logic.
2678 * (Kswapd normally doesn't need memory anyway, but sometimes
2679 * you need a small amount of memory in order to be able to
2680 * page out something else, and this flag essentially protects
2681 * us from recursively trying to free more memory as we're
2682 * trying to free the first piece of memory in the first place).
2684 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2688 classzone_idx = MAX_NR_ZONES - 1;
2690 unsigned long new_order;
2691 int new_classzone_idx;
2694 new_order = pgdat->kswapd_max_order;
2695 new_classzone_idx = pgdat->classzone_idx;
2696 pgdat->kswapd_max_order = 0;
2697 pgdat->classzone_idx = MAX_NR_ZONES - 1;
2698 if (order < new_order || classzone_idx > new_classzone_idx) {
2700 * Don't sleep if someone wants a larger 'order'
2701 * allocation or has tigher zone constraints
2704 classzone_idx = new_classzone_idx;
2706 kswapd_try_to_sleep(pgdat, order, classzone_idx);
2707 order = pgdat->kswapd_max_order;
2708 classzone_idx = pgdat->classzone_idx;
2709 pgdat->kswapd_max_order = 0;
2710 pgdat->classzone_idx = MAX_NR_ZONES - 1;
2713 ret = try_to_freeze();
2714 if (kthread_should_stop())
2718 * We can speed up thawing tasks if we don't call balance_pgdat
2719 * after returning from the refrigerator
2722 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2723 order = balance_pgdat(pgdat, order, &classzone_idx);
2730 * A zone is low on free memory, so wake its kswapd task to service it.
2732 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2736 if (!populated_zone(zone))
2739 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2741 pgdat = zone->zone_pgdat;
2742 if (pgdat->kswapd_max_order < order) {
2743 pgdat->kswapd_max_order = order;
2744 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2746 if (!waitqueue_active(&pgdat->kswapd_wait))
2748 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2751 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2752 wake_up_interruptible(&pgdat->kswapd_wait);
2756 * The reclaimable count would be mostly accurate.
2757 * The less reclaimable pages may be
2758 * - mlocked pages, which will be moved to unevictable list when encountered
2759 * - mapped pages, which may require several travels to be reclaimed
2760 * - dirty pages, which is not "instantly" reclaimable
2762 unsigned long global_reclaimable_pages(void)
2766 nr = global_page_state(NR_ACTIVE_FILE) +
2767 global_page_state(NR_INACTIVE_FILE);
2769 if (nr_swap_pages > 0)
2770 nr += global_page_state(NR_ACTIVE_ANON) +
2771 global_page_state(NR_INACTIVE_ANON);
2776 unsigned long zone_reclaimable_pages(struct zone *zone)
2780 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2781 zone_page_state(zone, NR_INACTIVE_FILE);
2783 if (nr_swap_pages > 0)
2784 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2785 zone_page_state(zone, NR_INACTIVE_ANON);
2790 #ifdef CONFIG_HIBERNATION
2792 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2795 * Rather than trying to age LRUs the aim is to preserve the overall
2796 * LRU order by reclaiming preferentially
2797 * inactive > active > active referenced > active mapped
2799 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2801 struct reclaim_state reclaim_state;
2802 struct scan_control sc = {
2803 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2807 .nr_to_reclaim = nr_to_reclaim,
2808 .hibernation_mode = 1,
2809 .swappiness = vm_swappiness,
2812 struct shrink_control shrink = {
2813 .gfp_mask = sc.gfp_mask,
2815 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2816 struct task_struct *p = current;
2817 unsigned long nr_reclaimed;
2819 p->flags |= PF_MEMALLOC;
2820 lockdep_set_current_reclaim_state(sc.gfp_mask);
2821 reclaim_state.reclaimed_slab = 0;
2822 p->reclaim_state = &reclaim_state;
2824 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2826 p->reclaim_state = NULL;
2827 lockdep_clear_current_reclaim_state();
2828 p->flags &= ~PF_MEMALLOC;
2830 return nr_reclaimed;
2832 #endif /* CONFIG_HIBERNATION */
2834 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2835 not required for correctness. So if the last cpu in a node goes
2836 away, we get changed to run anywhere: as the first one comes back,
2837 restore their cpu bindings. */
2838 static int __devinit cpu_callback(struct notifier_block *nfb,
2839 unsigned long action, void *hcpu)
2843 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2844 for_each_node_state(nid, N_HIGH_MEMORY) {
2845 pg_data_t *pgdat = NODE_DATA(nid);
2846 const struct cpumask *mask;
2848 mask = cpumask_of_node(pgdat->node_id);
2850 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2851 /* One of our CPUs online: restore mask */
2852 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2859 * This kswapd start function will be called by init and node-hot-add.
2860 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2862 int kswapd_run(int nid)
2864 pg_data_t *pgdat = NODE_DATA(nid);
2870 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2871 if (IS_ERR(pgdat->kswapd)) {
2872 /* failure at boot is fatal */
2873 BUG_ON(system_state == SYSTEM_BOOTING);
2874 printk("Failed to start kswapd on node %d\n",nid);
2881 * Called by memory hotplug when all memory in a node is offlined.
2883 void kswapd_stop(int nid)
2885 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2888 kthread_stop(kswapd);
2891 static int __init kswapd_init(void)
2896 for_each_node_state(nid, N_HIGH_MEMORY)
2898 hotcpu_notifier(cpu_callback, 0);
2902 module_init(kswapd_init)
2908 * If non-zero call zone_reclaim when the number of free pages falls below
2911 int zone_reclaim_mode __read_mostly;
2913 #define RECLAIM_OFF 0
2914 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2915 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2916 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2919 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2920 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2923 #define ZONE_RECLAIM_PRIORITY 4
2926 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2929 int sysctl_min_unmapped_ratio = 1;
2932 * If the number of slab pages in a zone grows beyond this percentage then
2933 * slab reclaim needs to occur.
2935 int sysctl_min_slab_ratio = 5;
2937 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2939 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2940 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2941 zone_page_state(zone, NR_ACTIVE_FILE);
2944 * It's possible for there to be more file mapped pages than
2945 * accounted for by the pages on the file LRU lists because
2946 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2948 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2951 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2952 static long zone_pagecache_reclaimable(struct zone *zone)
2954 long nr_pagecache_reclaimable;
2958 * If RECLAIM_SWAP is set, then all file pages are considered
2959 * potentially reclaimable. Otherwise, we have to worry about
2960 * pages like swapcache and zone_unmapped_file_pages() provides
2963 if (zone_reclaim_mode & RECLAIM_SWAP)
2964 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2966 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2968 /* If we can't clean pages, remove dirty pages from consideration */
2969 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2970 delta += zone_page_state(zone, NR_FILE_DIRTY);
2972 /* Watch for any possible underflows due to delta */
2973 if (unlikely(delta > nr_pagecache_reclaimable))
2974 delta = nr_pagecache_reclaimable;
2976 return nr_pagecache_reclaimable - delta;
2980 * Try to free up some pages from this zone through reclaim.
2982 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2984 /* Minimum pages needed in order to stay on node */
2985 const unsigned long nr_pages = 1 << order;
2986 struct task_struct *p = current;
2987 struct reclaim_state reclaim_state;
2989 struct scan_control sc = {
2990 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2991 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2993 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2995 .gfp_mask = gfp_mask,
2996 .swappiness = vm_swappiness,
2999 struct shrink_control shrink = {
3000 .gfp_mask = sc.gfp_mask,
3002 unsigned long nr_slab_pages0, nr_slab_pages1;
3006 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3007 * and we also need to be able to write out pages for RECLAIM_WRITE
3010 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3011 lockdep_set_current_reclaim_state(gfp_mask);
3012 reclaim_state.reclaimed_slab = 0;
3013 p->reclaim_state = &reclaim_state;
3015 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3017 * Free memory by calling shrink zone with increasing
3018 * priorities until we have enough memory freed.
3020 priority = ZONE_RECLAIM_PRIORITY;
3022 shrink_zone(priority, zone, &sc);
3024 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3027 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3028 shrink.nr_scanned = sc.nr_scanned;
3029 if (nr_slab_pages0 > zone->min_slab_pages) {
3031 * shrink_slab() does not currently allow us to determine how
3032 * many pages were freed in this zone. So we take the current
3033 * number of slab pages and shake the slab until it is reduced
3034 * by the same nr_pages that we used for reclaiming unmapped
3037 * Note that shrink_slab will free memory on all zones and may
3041 unsigned long lru_pages = zone_reclaimable_pages(zone);
3043 /* No reclaimable slab or very low memory pressure */
3044 if (!shrink_slab(&shrink, lru_pages))
3047 /* Freed enough memory */
3048 nr_slab_pages1 = zone_page_state(zone,
3049 NR_SLAB_RECLAIMABLE);
3050 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3055 * Update nr_reclaimed by the number of slab pages we
3056 * reclaimed from this zone.
3058 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3059 if (nr_slab_pages1 < nr_slab_pages0)
3060 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3063 p->reclaim_state = NULL;
3064 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3065 lockdep_clear_current_reclaim_state();
3066 return sc.nr_reclaimed >= nr_pages;
3069 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3075 * Zone reclaim reclaims unmapped file backed pages and
3076 * slab pages if we are over the defined limits.
3078 * A small portion of unmapped file backed pages is needed for
3079 * file I/O otherwise pages read by file I/O will be immediately
3080 * thrown out if the zone is overallocated. So we do not reclaim
3081 * if less than a specified percentage of the zone is used by
3082 * unmapped file backed pages.
3084 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3085 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3086 return ZONE_RECLAIM_FULL;
3088 if (zone->all_unreclaimable)
3089 return ZONE_RECLAIM_FULL;
3092 * Do not scan if the allocation should not be delayed.
3094 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3095 return ZONE_RECLAIM_NOSCAN;
3098 * Only run zone reclaim on the local zone or on zones that do not
3099 * have associated processors. This will favor the local processor
3100 * over remote processors and spread off node memory allocations
3101 * as wide as possible.
3103 node_id = zone_to_nid(zone);
3104 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3105 return ZONE_RECLAIM_NOSCAN;
3107 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3108 return ZONE_RECLAIM_NOSCAN;
3110 ret = __zone_reclaim(zone, gfp_mask, order);
3111 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3114 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3121 * page_evictable - test whether a page is evictable
3122 * @page: the page to test
3123 * @vma: the VMA in which the page is or will be mapped, may be NULL
3125 * Test whether page is evictable--i.e., should be placed on active/inactive
3126 * lists vs unevictable list. The vma argument is !NULL when called from the
3127 * fault path to determine how to instantate a new page.
3129 * Reasons page might not be evictable:
3130 * (1) page's mapping marked unevictable
3131 * (2) page is part of an mlocked VMA
3134 int page_evictable(struct page *page, struct vm_area_struct *vma)
3137 if (mapping_unevictable(page_mapping(page)))
3140 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3147 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3148 * @page: page to check evictability and move to appropriate lru list
3149 * @zone: zone page is in
3151 * Checks a page for evictability and moves the page to the appropriate
3154 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3155 * have PageUnevictable set.
3157 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3159 VM_BUG_ON(PageActive(page));
3162 ClearPageUnevictable(page);
3163 if (page_evictable(page, NULL)) {
3164 enum lru_list l = page_lru_base_type(page);
3166 __dec_zone_state(zone, NR_UNEVICTABLE);
3167 list_move(&page->lru, &zone->lru[l].list);
3168 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3169 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3170 __count_vm_event(UNEVICTABLE_PGRESCUED);
3173 * rotate unevictable list
3175 SetPageUnevictable(page);
3176 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3177 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3178 if (page_evictable(page, NULL))
3184 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3185 * @mapping: struct address_space to scan for evictable pages
3187 * Scan all pages in mapping. Check unevictable pages for
3188 * evictability and move them to the appropriate zone lru list.
3190 void scan_mapping_unevictable_pages(struct address_space *mapping)
3193 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3196 struct pagevec pvec;
3198 if (mapping->nrpages == 0)
3201 pagevec_init(&pvec, 0);
3202 while (next < end &&
3203 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3209 for (i = 0; i < pagevec_count(&pvec); i++) {
3210 struct page *page = pvec.pages[i];
3211 pgoff_t page_index = page->index;
3212 struct zone *pagezone = page_zone(page);
3215 if (page_index > next)
3219 if (pagezone != zone) {
3221 spin_unlock_irq(&zone->lru_lock);
3223 spin_lock_irq(&zone->lru_lock);
3226 if (PageLRU(page) && PageUnevictable(page))
3227 check_move_unevictable_page(page, zone);
3230 spin_unlock_irq(&zone->lru_lock);
3231 pagevec_release(&pvec);
3233 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3239 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3240 * @zone - zone of which to scan the unevictable list
3242 * Scan @zone's unevictable LRU lists to check for pages that have become
3243 * evictable. Move those that have to @zone's inactive list where they
3244 * become candidates for reclaim, unless shrink_inactive_zone() decides
3245 * to reactivate them. Pages that are still unevictable are rotated
3246 * back onto @zone's unevictable list.
3248 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3249 static void scan_zone_unevictable_pages(struct zone *zone)
3251 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
3253 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
3255 while (nr_to_scan > 0) {
3256 unsigned long batch_size = min(nr_to_scan,
3257 SCAN_UNEVICTABLE_BATCH_SIZE);
3259 spin_lock_irq(&zone->lru_lock);
3260 for (scan = 0; scan < batch_size; scan++) {
3261 struct page *page = lru_to_page(l_unevictable);
3263 if (!trylock_page(page))
3266 prefetchw_prev_lru_page(page, l_unevictable, flags);
3268 if (likely(PageLRU(page) && PageUnevictable(page)))
3269 check_move_unevictable_page(page, zone);
3273 spin_unlock_irq(&zone->lru_lock);
3275 nr_to_scan -= batch_size;
3281 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3283 * A really big hammer: scan all zones' unevictable LRU lists to check for
3284 * pages that have become evictable. Move those back to the zones'
3285 * inactive list where they become candidates for reclaim.
3286 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3287 * and we add swap to the system. As such, it runs in the context of a task
3288 * that has possibly/probably made some previously unevictable pages
3291 static void scan_all_zones_unevictable_pages(void)
3295 for_each_zone(zone) {
3296 scan_zone_unevictable_pages(zone);
3301 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3302 * all nodes' unevictable lists for evictable pages
3304 unsigned long scan_unevictable_pages;
3306 int scan_unevictable_handler(struct ctl_table *table, int write,
3307 void __user *buffer,
3308 size_t *length, loff_t *ppos)
3310 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3312 if (write && *(unsigned long *)table->data)
3313 scan_all_zones_unevictable_pages();
3315 scan_unevictable_pages = 0;
3321 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3322 * a specified node's per zone unevictable lists for evictable pages.
3325 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3326 struct sysdev_attribute *attr,
3329 return sprintf(buf, "0\n"); /* always zero; should fit... */
3332 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3333 struct sysdev_attribute *attr,
3334 const char *buf, size_t count)
3336 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3339 unsigned long req = strict_strtoul(buf, 10, &res);
3342 return 1; /* zero is no-op */
3344 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3345 if (!populated_zone(zone))
3347 scan_zone_unevictable_pages(zone);
3353 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3354 read_scan_unevictable_node,
3355 write_scan_unevictable_node);
3357 int scan_unevictable_register_node(struct node *node)
3359 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3362 void scan_unevictable_unregister_node(struct node *node)
3364 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);