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_lru_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 static inline int do_shrinker_shrink(struct shrinker *shrinker,
206 struct shrink_control *sc,
207 unsigned long nr_to_scan)
209 sc->nr_to_scan = nr_to_scan;
210 return (*shrinker->shrink)(shrinker, sc);
213 #define SHRINK_BATCH 128
215 * Call the shrink functions to age shrinkable caches
217 * Here we assume it costs one seek to replace a lru page and that it also
218 * takes a seek to recreate a cache object. With this in mind we age equal
219 * percentages of the lru and ageable caches. This should balance the seeks
220 * generated by these structures.
222 * If the vm encountered mapped pages on the LRU it increase the pressure on
223 * slab to avoid swapping.
225 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
227 * `lru_pages' represents the number of on-LRU pages in all the zones which
228 * are eligible for the caller's allocation attempt. It is used for balancing
229 * slab reclaim versus page reclaim.
231 * Returns the number of slab objects which we shrunk.
233 unsigned long shrink_slab(struct shrink_control *shrink,
234 unsigned long nr_pages_scanned,
235 unsigned long lru_pages)
237 struct shrinker *shrinker;
238 unsigned long ret = 0;
240 if (nr_pages_scanned == 0)
241 nr_pages_scanned = SWAP_CLUSTER_MAX;
243 if (!down_read_trylock(&shrinker_rwsem)) {
244 /* Assume we'll be able to shrink next time */
249 list_for_each_entry(shrinker, &shrinker_list, list) {
250 unsigned long long delta;
251 unsigned long total_scan;
252 unsigned long max_pass;
258 * copy the current shrinker scan count into a local variable
259 * and zero it so that other concurrent shrinker invocations
260 * don't also do this scanning work.
264 } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
267 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
268 delta = (4 * nr_pages_scanned) / shrinker->seeks;
270 do_div(delta, lru_pages + 1);
272 if (total_scan < 0) {
273 printk(KERN_ERR "shrink_slab: %pF negative objects to "
275 shrinker->shrink, total_scan);
276 total_scan = max_pass;
280 * Avoid risking looping forever due to too large nr value:
281 * never try to free more than twice the estimate number of
284 if (total_scan > max_pass * 2)
285 total_scan = max_pass * 2;
287 trace_mm_shrink_slab_start(shrinker, shrink, nr,
288 nr_pages_scanned, lru_pages,
289 max_pass, delta, total_scan);
291 while (total_scan >= SHRINK_BATCH) {
292 long this_scan = SHRINK_BATCH;
295 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
296 shrink_ret = do_shrinker_shrink(shrinker, shrink,
298 if (shrink_ret == -1)
300 if (shrink_ret < nr_before)
301 ret += nr_before - shrink_ret;
302 count_vm_events(SLABS_SCANNED, this_scan);
303 total_scan -= this_scan;
309 * move the unused scan count back into the shrinker in a
310 * manner that handles concurrent updates. If we exhausted the
311 * scan, there is no need to do an update.
315 new_nr = total_scan + nr;
318 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
320 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
322 up_read(&shrinker_rwsem);
328 static void set_reclaim_mode(int priority, struct scan_control *sc,
331 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
334 * Initially assume we are entering either lumpy reclaim or
335 * reclaim/compaction.Depending on the order, we will either set the
336 * sync mode or just reclaim order-0 pages later.
338 if (COMPACTION_BUILD)
339 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
341 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
344 * Avoid using lumpy reclaim or reclaim/compaction if possible by
345 * restricting when its set to either costly allocations or when
346 * under memory pressure
348 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
349 sc->reclaim_mode |= syncmode;
350 else if (sc->order && priority < DEF_PRIORITY - 2)
351 sc->reclaim_mode |= syncmode;
353 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
356 static void reset_reclaim_mode(struct scan_control *sc)
358 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
361 static inline int is_page_cache_freeable(struct page *page)
364 * A freeable page cache page is referenced only by the caller
365 * that isolated the page, the page cache radix tree and
366 * optional buffer heads at page->private.
368 return page_count(page) - page_has_private(page) == 2;
371 static int may_write_to_queue(struct backing_dev_info *bdi,
372 struct scan_control *sc)
374 if (current->flags & PF_SWAPWRITE)
376 if (!bdi_write_congested(bdi))
378 if (bdi == current->backing_dev_info)
381 /* lumpy reclaim for hugepage often need a lot of write */
382 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
388 * We detected a synchronous write error writing a page out. Probably
389 * -ENOSPC. We need to propagate that into the address_space for a subsequent
390 * fsync(), msync() or close().
392 * The tricky part is that after writepage we cannot touch the mapping: nothing
393 * prevents it from being freed up. But we have a ref on the page and once
394 * that page is locked, the mapping is pinned.
396 * We're allowed to run sleeping lock_page() here because we know the caller has
399 static void handle_write_error(struct address_space *mapping,
400 struct page *page, int error)
403 if (page_mapping(page) == mapping)
404 mapping_set_error(mapping, error);
408 /* possible outcome of pageout() */
410 /* failed to write page out, page is locked */
412 /* move page to the active list, page is locked */
414 /* page has been sent to the disk successfully, page is unlocked */
416 /* page is clean and locked */
421 * pageout is called by shrink_page_list() for each dirty page.
422 * Calls ->writepage().
424 static pageout_t pageout(struct page *page, struct address_space *mapping,
425 struct scan_control *sc)
428 * If the page is dirty, only perform writeback if that write
429 * will be non-blocking. To prevent this allocation from being
430 * stalled by pagecache activity. But note that there may be
431 * stalls if we need to run get_block(). We could test
432 * PagePrivate for that.
434 * If this process is currently in __generic_file_aio_write() against
435 * this page's queue, we can perform writeback even if that
438 * If the page is swapcache, write it back even if that would
439 * block, for some throttling. This happens by accident, because
440 * swap_backing_dev_info is bust: it doesn't reflect the
441 * congestion state of the swapdevs. Easy to fix, if needed.
443 if (!is_page_cache_freeable(page))
447 * Some data journaling orphaned pages can have
448 * page->mapping == NULL while being dirty with clean buffers.
450 if (page_has_private(page)) {
451 if (try_to_free_buffers(page)) {
452 ClearPageDirty(page);
453 printk("%s: orphaned page\n", __func__);
459 if (mapping->a_ops->writepage == NULL)
460 return PAGE_ACTIVATE;
461 if (!may_write_to_queue(mapping->backing_dev_info, sc))
464 if (clear_page_dirty_for_io(page)) {
466 struct writeback_control wbc = {
467 .sync_mode = WB_SYNC_NONE,
468 .nr_to_write = SWAP_CLUSTER_MAX,
470 .range_end = LLONG_MAX,
474 SetPageReclaim(page);
475 res = mapping->a_ops->writepage(page, &wbc);
477 handle_write_error(mapping, page, res);
478 if (res == AOP_WRITEPAGE_ACTIVATE) {
479 ClearPageReclaim(page);
480 return PAGE_ACTIVATE;
484 * Wait on writeback if requested to. This happens when
485 * direct reclaiming a large contiguous area and the
486 * first attempt to free a range of pages fails.
488 if (PageWriteback(page) &&
489 (sc->reclaim_mode & RECLAIM_MODE_SYNC))
490 wait_on_page_writeback(page);
492 if (!PageWriteback(page)) {
493 /* synchronous write or broken a_ops? */
494 ClearPageReclaim(page);
496 trace_mm_vmscan_writepage(page,
497 trace_reclaim_flags(page, sc->reclaim_mode));
498 inc_zone_page_state(page, NR_VMSCAN_WRITE);
506 * Same as remove_mapping, but if the page is removed from the mapping, it
507 * gets returned with a refcount of 0.
509 static int __remove_mapping(struct address_space *mapping, struct page *page)
511 BUG_ON(!PageLocked(page));
512 BUG_ON(mapping != page_mapping(page));
514 spin_lock_irq(&mapping->tree_lock);
516 * The non racy check for a busy page.
518 * Must be careful with the order of the tests. When someone has
519 * a ref to the page, it may be possible that they dirty it then
520 * drop the reference. So if PageDirty is tested before page_count
521 * here, then the following race may occur:
523 * get_user_pages(&page);
524 * [user mapping goes away]
526 * !PageDirty(page) [good]
527 * SetPageDirty(page);
529 * !page_count(page) [good, discard it]
531 * [oops, our write_to data is lost]
533 * Reversing the order of the tests ensures such a situation cannot
534 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
535 * load is not satisfied before that of page->_count.
537 * Note that if SetPageDirty is always performed via set_page_dirty,
538 * and thus under tree_lock, then this ordering is not required.
540 if (!page_freeze_refs(page, 2))
542 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
543 if (unlikely(PageDirty(page))) {
544 page_unfreeze_refs(page, 2);
548 if (PageSwapCache(page)) {
549 swp_entry_t swap = { .val = page_private(page) };
550 __delete_from_swap_cache(page);
551 spin_unlock_irq(&mapping->tree_lock);
552 swapcache_free(swap, page);
554 void (*freepage)(struct page *);
556 freepage = mapping->a_ops->freepage;
558 __delete_from_page_cache(page);
559 spin_unlock_irq(&mapping->tree_lock);
560 mem_cgroup_uncharge_cache_page(page);
562 if (freepage != NULL)
569 spin_unlock_irq(&mapping->tree_lock);
574 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
575 * someone else has a ref on the page, abort and return 0. If it was
576 * successfully detached, return 1. Assumes the caller has a single ref on
579 int remove_mapping(struct address_space *mapping, struct page *page)
581 if (__remove_mapping(mapping, page)) {
583 * Unfreezing the refcount with 1 rather than 2 effectively
584 * drops the pagecache ref for us without requiring another
587 page_unfreeze_refs(page, 1);
594 * putback_lru_page - put previously isolated page onto appropriate LRU list
595 * @page: page to be put back to appropriate lru list
597 * Add previously isolated @page to appropriate LRU list.
598 * Page may still be unevictable for other reasons.
600 * lru_lock must not be held, interrupts must be enabled.
602 void putback_lru_page(struct page *page)
605 int active = !!TestClearPageActive(page);
606 int was_unevictable = PageUnevictable(page);
608 VM_BUG_ON(PageLRU(page));
611 ClearPageUnevictable(page);
613 if (page_evictable(page, NULL)) {
615 * For evictable pages, we can use the cache.
616 * In event of a race, worst case is we end up with an
617 * unevictable page on [in]active list.
618 * We know how to handle that.
620 lru = active + page_lru_base_type(page);
621 lru_cache_add_lru(page, lru);
624 * Put unevictable pages directly on zone's unevictable
627 lru = LRU_UNEVICTABLE;
628 add_page_to_unevictable_list(page);
630 * When racing with an mlock clearing (page is
631 * unlocked), make sure that if the other thread does
632 * not observe our setting of PG_lru and fails
633 * isolation, we see PG_mlocked cleared below and move
634 * the page back to the evictable list.
636 * The other side is TestClearPageMlocked().
642 * page's status can change while we move it among lru. If an evictable
643 * page is on unevictable list, it never be freed. To avoid that,
644 * check after we added it to the list, again.
646 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
647 if (!isolate_lru_page(page)) {
651 /* This means someone else dropped this page from LRU
652 * So, it will be freed or putback to LRU again. There is
653 * nothing to do here.
657 if (was_unevictable && lru != LRU_UNEVICTABLE)
658 count_vm_event(UNEVICTABLE_PGRESCUED);
659 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
660 count_vm_event(UNEVICTABLE_PGCULLED);
662 put_page(page); /* drop ref from isolate */
665 enum page_references {
667 PAGEREF_RECLAIM_CLEAN,
672 static enum page_references page_check_references(struct page *page,
673 struct scan_control *sc)
675 int referenced_ptes, referenced_page;
676 unsigned long vm_flags;
678 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
679 referenced_page = TestClearPageReferenced(page);
681 /* Lumpy reclaim - ignore references */
682 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
683 return PAGEREF_RECLAIM;
686 * Mlock lost the isolation race with us. Let try_to_unmap()
687 * move the page to the unevictable list.
689 if (vm_flags & VM_LOCKED)
690 return PAGEREF_RECLAIM;
692 if (referenced_ptes) {
694 return PAGEREF_ACTIVATE;
696 * All mapped pages start out with page table
697 * references from the instantiating fault, so we need
698 * to look twice if a mapped file page is used more
701 * Mark it and spare it for another trip around the
702 * inactive list. Another page table reference will
703 * lead to its activation.
705 * Note: the mark is set for activated pages as well
706 * so that recently deactivated but used pages are
709 SetPageReferenced(page);
712 return PAGEREF_ACTIVATE;
717 /* Reclaim if clean, defer dirty pages to writeback */
718 if (referenced_page && !PageSwapBacked(page))
719 return PAGEREF_RECLAIM_CLEAN;
721 return PAGEREF_RECLAIM;
724 static noinline_for_stack void free_page_list(struct list_head *free_pages)
726 struct pagevec freed_pvec;
727 struct page *page, *tmp;
729 pagevec_init(&freed_pvec, 1);
731 list_for_each_entry_safe(page, tmp, free_pages, lru) {
732 list_del(&page->lru);
733 if (!pagevec_add(&freed_pvec, page)) {
734 __pagevec_free(&freed_pvec);
735 pagevec_reinit(&freed_pvec);
739 pagevec_free(&freed_pvec);
743 * shrink_page_list() returns the number of reclaimed pages
745 static unsigned long shrink_page_list(struct list_head *page_list,
747 struct scan_control *sc)
749 LIST_HEAD(ret_pages);
750 LIST_HEAD(free_pages);
752 unsigned long nr_dirty = 0;
753 unsigned long nr_congested = 0;
754 unsigned long nr_reclaimed = 0;
758 while (!list_empty(page_list)) {
759 enum page_references references;
760 struct address_space *mapping;
766 page = lru_to_page(page_list);
767 list_del(&page->lru);
769 if (!trylock_page(page))
772 VM_BUG_ON(PageActive(page));
773 VM_BUG_ON(page_zone(page) != zone);
777 if (unlikely(!page_evictable(page, NULL)))
780 if (!sc->may_unmap && page_mapped(page))
783 /* Double the slab pressure for mapped and swapcache pages */
784 if (page_mapped(page) || PageSwapCache(page))
787 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
788 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
790 if (PageWriteback(page)) {
792 * Synchronous reclaim is performed in two passes,
793 * first an asynchronous pass over the list to
794 * start parallel writeback, and a second synchronous
795 * pass to wait for the IO to complete. Wait here
796 * for any page for which writeback has already
799 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
801 wait_on_page_writeback(page);
808 references = page_check_references(page, sc);
809 switch (references) {
810 case PAGEREF_ACTIVATE:
811 goto activate_locked;
814 case PAGEREF_RECLAIM:
815 case PAGEREF_RECLAIM_CLEAN:
816 ; /* try to reclaim the page below */
820 * Anonymous process memory has backing store?
821 * Try to allocate it some swap space here.
823 if (PageAnon(page) && !PageSwapCache(page)) {
824 if (!(sc->gfp_mask & __GFP_IO))
826 if (!add_to_swap(page))
827 goto activate_locked;
831 mapping = page_mapping(page);
834 * The page is mapped into the page tables of one or more
835 * processes. Try to unmap it here.
837 if (page_mapped(page) && mapping) {
838 switch (try_to_unmap(page, TTU_UNMAP)) {
840 goto activate_locked;
846 ; /* try to free the page below */
850 if (PageDirty(page)) {
853 if (references == PAGEREF_RECLAIM_CLEAN)
857 if (!sc->may_writepage)
860 /* Page is dirty, try to write it out here */
861 switch (pageout(page, mapping, sc)) {
866 goto activate_locked;
868 if (PageWriteback(page))
874 * A synchronous write - probably a ramdisk. Go
875 * ahead and try to reclaim the page.
877 if (!trylock_page(page))
879 if (PageDirty(page) || PageWriteback(page))
881 mapping = page_mapping(page);
883 ; /* try to free the page below */
888 * If the page has buffers, try to free the buffer mappings
889 * associated with this page. If we succeed we try to free
892 * We do this even if the page is PageDirty().
893 * try_to_release_page() does not perform I/O, but it is
894 * possible for a page to have PageDirty set, but it is actually
895 * clean (all its buffers are clean). This happens if the
896 * buffers were written out directly, with submit_bh(). ext3
897 * will do this, as well as the blockdev mapping.
898 * try_to_release_page() will discover that cleanness and will
899 * drop the buffers and mark the page clean - it can be freed.
901 * Rarely, pages can have buffers and no ->mapping. These are
902 * the pages which were not successfully invalidated in
903 * truncate_complete_page(). We try to drop those buffers here
904 * and if that worked, and the page is no longer mapped into
905 * process address space (page_count == 1) it can be freed.
906 * Otherwise, leave the page on the LRU so it is swappable.
908 if (page_has_private(page)) {
909 if (!try_to_release_page(page, sc->gfp_mask))
910 goto activate_locked;
911 if (!mapping && page_count(page) == 1) {
913 if (put_page_testzero(page))
917 * rare race with speculative reference.
918 * the speculative reference will free
919 * this page shortly, so we may
920 * increment nr_reclaimed here (and
921 * leave it off the LRU).
929 if (!mapping || !__remove_mapping(mapping, page))
933 * At this point, we have no other references and there is
934 * no way to pick any more up (removed from LRU, removed
935 * from pagecache). Can use non-atomic bitops now (and
936 * we obviously don't have to worry about waking up a process
937 * waiting on the page lock, because there are no references.
939 __clear_page_locked(page);
944 * Is there need to periodically free_page_list? It would
945 * appear not as the counts should be low
947 list_add(&page->lru, &free_pages);
951 if (PageSwapCache(page))
952 try_to_free_swap(page);
954 putback_lru_page(page);
955 reset_reclaim_mode(sc);
959 /* Not a candidate for swapping, so reclaim swap space. */
960 if (PageSwapCache(page) && vm_swap_full())
961 try_to_free_swap(page);
962 VM_BUG_ON(PageActive(page));
968 reset_reclaim_mode(sc);
970 list_add(&page->lru, &ret_pages);
971 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
975 * Tag a zone as congested if all the dirty pages encountered were
976 * backed by a congested BDI. In this case, reclaimers should just
977 * back off and wait for congestion to clear because further reclaim
978 * will encounter the same problem
980 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
981 zone_set_flag(zone, ZONE_CONGESTED);
983 free_page_list(&free_pages);
985 list_splice(&ret_pages, page_list);
986 count_vm_events(PGACTIVATE, pgactivate);
991 * Attempt to remove the specified page from its LRU. Only take this page
992 * if it is of the appropriate PageActive status. Pages which are being
993 * freed elsewhere are also ignored.
995 * page: page to consider
996 * mode: one of the LRU isolation modes defined above
998 * returns 0 on success, -ve errno on failure.
1000 int __isolate_lru_page(struct page *page, int mode, int file)
1004 /* Only take pages on the LRU. */
1009 * When checking the active state, we need to be sure we are
1010 * dealing with comparible boolean values. Take the logical not
1013 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
1016 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
1020 * When this function is being called for lumpy reclaim, we
1021 * initially look into all LRU pages, active, inactive and
1022 * unevictable; only give shrink_page_list evictable pages.
1024 if (PageUnevictable(page))
1029 if (likely(get_page_unless_zero(page))) {
1031 * Be careful not to clear PageLRU until after we're
1032 * sure the page is not being freed elsewhere -- the
1033 * page release code relies on it.
1043 * zone->lru_lock is heavily contended. Some of the functions that
1044 * shrink the lists perform better by taking out a batch of pages
1045 * and working on them outside the LRU lock.
1047 * For pagecache intensive workloads, this function is the hottest
1048 * spot in the kernel (apart from copy_*_user functions).
1050 * Appropriate locks must be held before calling this function.
1052 * @nr_to_scan: The number of pages to look through on the list.
1053 * @src: The LRU list to pull pages off.
1054 * @dst: The temp list to put pages on to.
1055 * @scanned: The number of pages that were scanned.
1056 * @order: The caller's attempted allocation order
1057 * @mode: One of the LRU isolation modes
1058 * @file: True [1] if isolating file [!anon] pages
1060 * returns how many pages were moved onto *@dst.
1062 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1063 struct list_head *src, struct list_head *dst,
1064 unsigned long *scanned, int order, int mode, int file)
1066 unsigned long nr_taken = 0;
1067 unsigned long nr_lumpy_taken = 0;
1068 unsigned long nr_lumpy_dirty = 0;
1069 unsigned long nr_lumpy_failed = 0;
1072 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1075 unsigned long end_pfn;
1076 unsigned long page_pfn;
1079 page = lru_to_page(src);
1080 prefetchw_prev_lru_page(page, src, flags);
1082 VM_BUG_ON(!PageLRU(page));
1084 switch (__isolate_lru_page(page, mode, file)) {
1086 list_move(&page->lru, dst);
1087 mem_cgroup_del_lru(page);
1088 nr_taken += hpage_nr_pages(page);
1092 /* else it is being freed elsewhere */
1093 list_move(&page->lru, src);
1094 mem_cgroup_rotate_lru_list(page, page_lru(page));
1105 * Attempt to take all pages in the order aligned region
1106 * surrounding the tag page. Only take those pages of
1107 * the same active state as that tag page. We may safely
1108 * round the target page pfn down to the requested order
1109 * as the mem_map is guaranteed valid out to MAX_ORDER,
1110 * where that page is in a different zone we will detect
1111 * it from its zone id and abort this block scan.
1113 zone_id = page_zone_id(page);
1114 page_pfn = page_to_pfn(page);
1115 pfn = page_pfn & ~((1 << order) - 1);
1116 end_pfn = pfn + (1 << order);
1117 for (; pfn < end_pfn; pfn++) {
1118 struct page *cursor_page;
1120 /* The target page is in the block, ignore it. */
1121 if (unlikely(pfn == page_pfn))
1124 /* Avoid holes within the zone. */
1125 if (unlikely(!pfn_valid_within(pfn)))
1128 cursor_page = pfn_to_page(pfn);
1130 /* Check that we have not crossed a zone boundary. */
1131 if (unlikely(page_zone_id(cursor_page) != zone_id))
1135 * If we don't have enough swap space, reclaiming of
1136 * anon page which don't already have a swap slot is
1139 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1140 !PageSwapCache(cursor_page))
1143 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1144 list_move(&cursor_page->lru, dst);
1145 mem_cgroup_del_lru(cursor_page);
1146 nr_taken += hpage_nr_pages(page);
1148 if (PageDirty(cursor_page))
1153 * Check if the page is freed already.
1155 * We can't use page_count() as that
1156 * requires compound_head and we don't
1157 * have a pin on the page here. If a
1158 * page is tail, we may or may not
1159 * have isolated the head, so assume
1160 * it's not free, it'd be tricky to
1161 * track the head status without a
1164 if (!PageTail(cursor_page) &&
1165 !atomic_read(&cursor_page->_count))
1171 /* If we break out of the loop above, lumpy reclaim failed */
1178 trace_mm_vmscan_lru_isolate(order,
1181 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1186 static unsigned long isolate_pages_global(unsigned long nr,
1187 struct list_head *dst,
1188 unsigned long *scanned, int order,
1189 int mode, struct zone *z,
1190 int active, int file)
1197 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1202 * clear_active_flags() is a helper for shrink_active_list(), clearing
1203 * any active bits from the pages in the list.
1205 static unsigned long clear_active_flags(struct list_head *page_list,
1206 unsigned int *count)
1212 list_for_each_entry(page, page_list, lru) {
1213 int numpages = hpage_nr_pages(page);
1214 lru = page_lru_base_type(page);
1215 if (PageActive(page)) {
1217 ClearPageActive(page);
1218 nr_active += numpages;
1221 count[lru] += numpages;
1228 * isolate_lru_page - tries to isolate a page from its LRU list
1229 * @page: page to isolate from its LRU list
1231 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1232 * vmstat statistic corresponding to whatever LRU list the page was on.
1234 * Returns 0 if the page was removed from an LRU list.
1235 * Returns -EBUSY if the page was not on an LRU list.
1237 * The returned page will have PageLRU() cleared. If it was found on
1238 * the active list, it will have PageActive set. If it was found on
1239 * the unevictable list, it will have the PageUnevictable bit set. That flag
1240 * may need to be cleared by the caller before letting the page go.
1242 * The vmstat statistic corresponding to the list on which the page was
1243 * found will be decremented.
1246 * (1) Must be called with an elevated refcount on the page. This is a
1247 * fundamentnal difference from isolate_lru_pages (which is called
1248 * without a stable reference).
1249 * (2) the lru_lock must not be held.
1250 * (3) interrupts must be enabled.
1252 int isolate_lru_page(struct page *page)
1256 VM_BUG_ON(!page_count(page));
1258 if (PageLRU(page)) {
1259 struct zone *zone = page_zone(page);
1261 spin_lock_irq(&zone->lru_lock);
1262 if (PageLRU(page)) {
1263 int lru = page_lru(page);
1268 del_page_from_lru_list(zone, page, lru);
1270 spin_unlock_irq(&zone->lru_lock);
1276 * Are there way too many processes in the direct reclaim path already?
1278 static int too_many_isolated(struct zone *zone, int file,
1279 struct scan_control *sc)
1281 unsigned long inactive, isolated;
1283 if (current_is_kswapd())
1286 if (!scanning_global_lru(sc))
1290 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1291 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1293 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1294 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1297 return isolated > inactive;
1301 * TODO: Try merging with migrations version of putback_lru_pages
1303 static noinline_for_stack void
1304 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1305 unsigned long nr_anon, unsigned long nr_file,
1306 struct list_head *page_list)
1309 struct pagevec pvec;
1310 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1312 pagevec_init(&pvec, 1);
1315 * Put back any unfreeable pages.
1317 spin_lock(&zone->lru_lock);
1318 while (!list_empty(page_list)) {
1320 page = lru_to_page(page_list);
1321 VM_BUG_ON(PageLRU(page));
1322 list_del(&page->lru);
1323 if (unlikely(!page_evictable(page, NULL))) {
1324 spin_unlock_irq(&zone->lru_lock);
1325 putback_lru_page(page);
1326 spin_lock_irq(&zone->lru_lock);
1330 lru = page_lru(page);
1331 add_page_to_lru_list(zone, page, lru);
1332 if (is_active_lru(lru)) {
1333 int file = is_file_lru(lru);
1334 int numpages = hpage_nr_pages(page);
1335 reclaim_stat->recent_rotated[file] += numpages;
1337 if (!pagevec_add(&pvec, page)) {
1338 spin_unlock_irq(&zone->lru_lock);
1339 __pagevec_release(&pvec);
1340 spin_lock_irq(&zone->lru_lock);
1343 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1344 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1346 spin_unlock_irq(&zone->lru_lock);
1347 pagevec_release(&pvec);
1350 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1351 struct scan_control *sc,
1352 unsigned long *nr_anon,
1353 unsigned long *nr_file,
1354 struct list_head *isolated_list)
1356 unsigned long nr_active;
1357 unsigned int count[NR_LRU_LISTS] = { 0, };
1358 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1360 nr_active = clear_active_flags(isolated_list, count);
1361 __count_vm_events(PGDEACTIVATE, nr_active);
1363 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1364 -count[LRU_ACTIVE_FILE]);
1365 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1366 -count[LRU_INACTIVE_FILE]);
1367 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1368 -count[LRU_ACTIVE_ANON]);
1369 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1370 -count[LRU_INACTIVE_ANON]);
1372 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1373 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1374 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1375 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1377 reclaim_stat->recent_scanned[0] += *nr_anon;
1378 reclaim_stat->recent_scanned[1] += *nr_file;
1382 * Returns true if the caller should wait to clean dirty/writeback pages.
1384 * If we are direct reclaiming for contiguous pages and we do not reclaim
1385 * everything in the list, try again and wait for writeback IO to complete.
1386 * This will stall high-order allocations noticeably. Only do that when really
1387 * need to free the pages under high memory pressure.
1389 static inline bool should_reclaim_stall(unsigned long nr_taken,
1390 unsigned long nr_freed,
1392 struct scan_control *sc)
1394 int lumpy_stall_priority;
1396 /* kswapd should not stall on sync IO */
1397 if (current_is_kswapd())
1400 /* Only stall on lumpy reclaim */
1401 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1404 /* If we have relaimed everything on the isolated list, no stall */
1405 if (nr_freed == nr_taken)
1409 * For high-order allocations, there are two stall thresholds.
1410 * High-cost allocations stall immediately where as lower
1411 * order allocations such as stacks require the scanning
1412 * priority to be much higher before stalling.
1414 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1415 lumpy_stall_priority = DEF_PRIORITY;
1417 lumpy_stall_priority = DEF_PRIORITY / 3;
1419 return priority <= lumpy_stall_priority;
1423 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1424 * of reclaimed pages
1426 static noinline_for_stack unsigned long
1427 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1428 struct scan_control *sc, int priority, int file)
1430 LIST_HEAD(page_list);
1431 unsigned long nr_scanned;
1432 unsigned long nr_reclaimed = 0;
1433 unsigned long nr_taken;
1434 unsigned long nr_anon;
1435 unsigned long nr_file;
1437 while (unlikely(too_many_isolated(zone, file, sc))) {
1438 congestion_wait(BLK_RW_ASYNC, HZ/10);
1440 /* We are about to die and free our memory. Return now. */
1441 if (fatal_signal_pending(current))
1442 return SWAP_CLUSTER_MAX;
1445 set_reclaim_mode(priority, sc, false);
1447 spin_lock_irq(&zone->lru_lock);
1449 if (scanning_global_lru(sc)) {
1450 nr_taken = isolate_pages_global(nr_to_scan,
1451 &page_list, &nr_scanned, sc->order,
1452 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1453 ISOLATE_BOTH : ISOLATE_INACTIVE,
1455 zone->pages_scanned += nr_scanned;
1456 if (current_is_kswapd())
1457 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1460 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1463 nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
1464 &page_list, &nr_scanned, sc->order,
1465 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1466 ISOLATE_BOTH : ISOLATE_INACTIVE,
1467 zone, sc->mem_cgroup,
1470 * mem_cgroup_isolate_pages() keeps track of
1471 * scanned pages on its own.
1475 if (nr_taken == 0) {
1476 spin_unlock_irq(&zone->lru_lock);
1480 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1482 spin_unlock_irq(&zone->lru_lock);
1484 nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1486 /* Check if we should syncronously wait for writeback */
1487 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1488 set_reclaim_mode(priority, sc, true);
1489 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1492 local_irq_disable();
1493 if (current_is_kswapd())
1494 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1495 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1497 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1499 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1501 nr_scanned, nr_reclaimed,
1503 trace_shrink_flags(file, sc->reclaim_mode));
1504 return nr_reclaimed;
1508 * This moves pages from the active list to the inactive list.
1510 * We move them the other way if the page is referenced by one or more
1511 * processes, from rmap.
1513 * If the pages are mostly unmapped, the processing is fast and it is
1514 * appropriate to hold zone->lru_lock across the whole operation. But if
1515 * the pages are mapped, the processing is slow (page_referenced()) so we
1516 * should drop zone->lru_lock around each page. It's impossible to balance
1517 * this, so instead we remove the pages from the LRU while processing them.
1518 * It is safe to rely on PG_active against the non-LRU pages in here because
1519 * nobody will play with that bit on a non-LRU page.
1521 * The downside is that we have to touch page->_count against each page.
1522 * But we had to alter page->flags anyway.
1525 static void move_active_pages_to_lru(struct zone *zone,
1526 struct list_head *list,
1529 unsigned long pgmoved = 0;
1530 struct pagevec pvec;
1533 pagevec_init(&pvec, 1);
1535 while (!list_empty(list)) {
1536 page = lru_to_page(list);
1538 VM_BUG_ON(PageLRU(page));
1541 list_move(&page->lru, &zone->lru[lru].list);
1542 mem_cgroup_add_lru_list(page, lru);
1543 pgmoved += hpage_nr_pages(page);
1545 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1546 spin_unlock_irq(&zone->lru_lock);
1547 if (buffer_heads_over_limit)
1548 pagevec_strip(&pvec);
1549 __pagevec_release(&pvec);
1550 spin_lock_irq(&zone->lru_lock);
1553 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1554 if (!is_active_lru(lru))
1555 __count_vm_events(PGDEACTIVATE, pgmoved);
1558 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1559 struct scan_control *sc, int priority, int file)
1561 unsigned long nr_taken;
1562 unsigned long pgscanned;
1563 unsigned long vm_flags;
1564 LIST_HEAD(l_hold); /* The pages which were snipped off */
1565 LIST_HEAD(l_active);
1566 LIST_HEAD(l_inactive);
1568 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1569 unsigned long nr_rotated = 0;
1572 spin_lock_irq(&zone->lru_lock);
1573 if (scanning_global_lru(sc)) {
1574 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1575 &pgscanned, sc->order,
1576 ISOLATE_ACTIVE, zone,
1578 zone->pages_scanned += pgscanned;
1580 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1581 &pgscanned, sc->order,
1582 ISOLATE_ACTIVE, zone,
1583 sc->mem_cgroup, 1, file);
1585 * mem_cgroup_isolate_pages() keeps track of
1586 * scanned pages on its own.
1590 reclaim_stat->recent_scanned[file] += nr_taken;
1592 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1594 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1596 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1597 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1598 spin_unlock_irq(&zone->lru_lock);
1600 while (!list_empty(&l_hold)) {
1602 page = lru_to_page(&l_hold);
1603 list_del(&page->lru);
1605 if (unlikely(!page_evictable(page, NULL))) {
1606 putback_lru_page(page);
1610 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1611 nr_rotated += hpage_nr_pages(page);
1613 * Identify referenced, file-backed active pages and
1614 * give them one more trip around the active list. So
1615 * that executable code get better chances to stay in
1616 * memory under moderate memory pressure. Anon pages
1617 * are not likely to be evicted by use-once streaming
1618 * IO, plus JVM can create lots of anon VM_EXEC pages,
1619 * so we ignore them here.
1621 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1622 list_add(&page->lru, &l_active);
1627 ClearPageActive(page); /* we are de-activating */
1628 list_add(&page->lru, &l_inactive);
1632 * Move pages back to the lru list.
1634 spin_lock_irq(&zone->lru_lock);
1636 * Count referenced pages from currently used mappings as rotated,
1637 * even though only some of them are actually re-activated. This
1638 * helps balance scan pressure between file and anonymous pages in
1641 reclaim_stat->recent_rotated[file] += nr_rotated;
1643 move_active_pages_to_lru(zone, &l_active,
1644 LRU_ACTIVE + file * LRU_FILE);
1645 move_active_pages_to_lru(zone, &l_inactive,
1646 LRU_BASE + file * LRU_FILE);
1647 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1648 spin_unlock_irq(&zone->lru_lock);
1652 static int inactive_anon_is_low_global(struct zone *zone)
1654 unsigned long active, inactive;
1656 active = zone_page_state(zone, NR_ACTIVE_ANON);
1657 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1659 if (inactive * zone->inactive_ratio < active)
1666 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1667 * @zone: zone to check
1668 * @sc: scan control of this context
1670 * Returns true if the zone does not have enough inactive anon pages,
1671 * meaning some active anon pages need to be deactivated.
1673 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1678 * If we don't have swap space, anonymous page deactivation
1681 if (!total_swap_pages)
1684 if (scanning_global_lru(sc))
1685 low = inactive_anon_is_low_global(zone);
1687 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1691 static inline int inactive_anon_is_low(struct zone *zone,
1692 struct scan_control *sc)
1698 static int inactive_file_is_low_global(struct zone *zone)
1700 unsigned long active, inactive;
1702 active = zone_page_state(zone, NR_ACTIVE_FILE);
1703 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1705 return (active > inactive);
1709 * inactive_file_is_low - check if file pages need to be deactivated
1710 * @zone: zone to check
1711 * @sc: scan control of this context
1713 * When the system is doing streaming IO, memory pressure here
1714 * ensures that active file pages get deactivated, until more
1715 * than half of the file pages are on the inactive list.
1717 * Once we get to that situation, protect the system's working
1718 * set from being evicted by disabling active file page aging.
1720 * This uses a different ratio than the anonymous pages, because
1721 * the page cache uses a use-once replacement algorithm.
1723 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1727 if (scanning_global_lru(sc))
1728 low = inactive_file_is_low_global(zone);
1730 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1734 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1738 return inactive_file_is_low(zone, sc);
1740 return inactive_anon_is_low(zone, sc);
1743 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1744 struct zone *zone, struct scan_control *sc, int priority)
1746 int file = is_file_lru(lru);
1748 if (is_active_lru(lru)) {
1749 if (inactive_list_is_low(zone, sc, file))
1750 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1754 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1758 * Determine how aggressively the anon and file LRU lists should be
1759 * scanned. The relative value of each set of LRU lists is determined
1760 * by looking at the fraction of the pages scanned we did rotate back
1761 * onto the active list instead of evict.
1763 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1765 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1766 unsigned long *nr, int priority)
1768 unsigned long anon, file, free;
1769 unsigned long anon_prio, file_prio;
1770 unsigned long ap, fp;
1771 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1772 u64 fraction[2], denominator;
1778 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1779 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1780 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1781 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1783 if (((anon + file) >> priority) < SWAP_CLUSTER_MAX) {
1784 /* kswapd does zone balancing and need to scan this zone */
1785 if (scanning_global_lru(sc) && current_is_kswapd())
1787 /* memcg may have small limit and need to avoid priority drop */
1788 if (!scanning_global_lru(sc))
1792 /* If we have no swap space, do not bother scanning anon pages. */
1793 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1801 if (scanning_global_lru(sc)) {
1802 free = zone_page_state(zone, NR_FREE_PAGES);
1803 /* If we have very few page cache pages,
1804 force-scan anon pages. */
1805 if (unlikely(file + free <= high_wmark_pages(zone))) {
1814 * With swappiness at 100, anonymous and file have the same priority.
1815 * This scanning priority is essentially the inverse of IO cost.
1817 anon_prio = sc->swappiness;
1818 file_prio = 200 - sc->swappiness;
1821 * OK, so we have swap space and a fair amount of page cache
1822 * pages. We use the recently rotated / recently scanned
1823 * ratios to determine how valuable each cache is.
1825 * Because workloads change over time (and to avoid overflow)
1826 * we keep these statistics as a floating average, which ends
1827 * up weighing recent references more than old ones.
1829 * anon in [0], file in [1]
1831 spin_lock_irq(&zone->lru_lock);
1832 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1833 reclaim_stat->recent_scanned[0] /= 2;
1834 reclaim_stat->recent_rotated[0] /= 2;
1837 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1838 reclaim_stat->recent_scanned[1] /= 2;
1839 reclaim_stat->recent_rotated[1] /= 2;
1843 * The amount of pressure on anon vs file pages is inversely
1844 * proportional to the fraction of recently scanned pages on
1845 * each list that were recently referenced and in active use.
1847 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1848 ap /= reclaim_stat->recent_rotated[0] + 1;
1850 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1851 fp /= reclaim_stat->recent_rotated[1] + 1;
1852 spin_unlock_irq(&zone->lru_lock);
1856 denominator = ap + fp + 1;
1858 for_each_evictable_lru(l) {
1859 int file = is_file_lru(l);
1862 scan = zone_nr_lru_pages(zone, sc, l);
1863 if (priority || noswap) {
1865 scan = div64_u64(scan * fraction[file], denominator);
1869 * If zone is small or memcg is small, nr[l] can be 0.
1870 * This results no-scan on this priority and priority drop down.
1871 * For global direct reclaim, it can visit next zone and tend
1872 * not to have problems. For global kswapd, it's for zone
1873 * balancing and it need to scan a small amounts. When using
1874 * memcg, priority drop can cause big latency. So, it's better
1875 * to scan small amount. See may_noscan above.
1877 if (!scan && force_scan) {
1879 scan = SWAP_CLUSTER_MAX;
1881 scan = SWAP_CLUSTER_MAX;
1888 * Reclaim/compaction depends on a number of pages being freed. To avoid
1889 * disruption to the system, a small number of order-0 pages continue to be
1890 * rotated and reclaimed in the normal fashion. However, by the time we get
1891 * back to the allocator and call try_to_compact_zone(), we ensure that
1892 * there are enough free pages for it to be likely successful
1894 static inline bool should_continue_reclaim(struct zone *zone,
1895 unsigned long nr_reclaimed,
1896 unsigned long nr_scanned,
1897 struct scan_control *sc)
1899 unsigned long pages_for_compaction;
1900 unsigned long inactive_lru_pages;
1902 /* If not in reclaim/compaction mode, stop */
1903 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1906 /* Consider stopping depending on scan and reclaim activity */
1907 if (sc->gfp_mask & __GFP_REPEAT) {
1909 * For __GFP_REPEAT allocations, stop reclaiming if the
1910 * full LRU list has been scanned and we are still failing
1911 * to reclaim pages. This full LRU scan is potentially
1912 * expensive but a __GFP_REPEAT caller really wants to succeed
1914 if (!nr_reclaimed && !nr_scanned)
1918 * For non-__GFP_REPEAT allocations which can presumably
1919 * fail without consequence, stop if we failed to reclaim
1920 * any pages from the last SWAP_CLUSTER_MAX number of
1921 * pages that were scanned. This will return to the
1922 * caller faster at the risk reclaim/compaction and
1923 * the resulting allocation attempt fails
1930 * If we have not reclaimed enough pages for compaction and the
1931 * inactive lists are large enough, continue reclaiming
1933 pages_for_compaction = (2UL << sc->order);
1934 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
1935 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1936 if (sc->nr_reclaimed < pages_for_compaction &&
1937 inactive_lru_pages > pages_for_compaction)
1940 /* If compaction would go ahead or the allocation would succeed, stop */
1941 switch (compaction_suitable(zone, sc->order)) {
1942 case COMPACT_PARTIAL:
1943 case COMPACT_CONTINUE:
1951 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1953 static void shrink_zone(int priority, struct zone *zone,
1954 struct scan_control *sc)
1956 unsigned long nr[NR_LRU_LISTS];
1957 unsigned long nr_to_scan;
1959 unsigned long nr_reclaimed, nr_scanned;
1960 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1964 nr_scanned = sc->nr_scanned;
1965 get_scan_count(zone, sc, nr, priority);
1967 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1968 nr[LRU_INACTIVE_FILE]) {
1969 for_each_evictable_lru(l) {
1971 nr_to_scan = min_t(unsigned long,
1972 nr[l], SWAP_CLUSTER_MAX);
1973 nr[l] -= nr_to_scan;
1975 nr_reclaimed += shrink_list(l, nr_to_scan,
1976 zone, sc, priority);
1980 * On large memory systems, scan >> priority can become
1981 * really large. This is fine for the starting priority;
1982 * we want to put equal scanning pressure on each zone.
1983 * However, if the VM has a harder time of freeing pages,
1984 * with multiple processes reclaiming pages, the total
1985 * freeing target can get unreasonably large.
1987 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1990 sc->nr_reclaimed += nr_reclaimed;
1993 * Even if we did not try to evict anon pages at all, we want to
1994 * rebalance the anon lru active/inactive ratio.
1996 if (inactive_anon_is_low(zone, sc))
1997 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1999 /* reclaim/compaction might need reclaim to continue */
2000 if (should_continue_reclaim(zone, nr_reclaimed,
2001 sc->nr_scanned - nr_scanned, sc))
2004 throttle_vm_writeout(sc->gfp_mask);
2008 * This is the direct reclaim path, for page-allocating processes. We only
2009 * try to reclaim pages from zones which will satisfy the caller's allocation
2012 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2014 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2016 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2017 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2018 * zone defense algorithm.
2020 * If a zone is deemed to be full of pinned pages then just give it a light
2021 * scan then give up on it.
2023 static void shrink_zones(int priority, struct zonelist *zonelist,
2024 struct scan_control *sc)
2028 unsigned long nr_soft_reclaimed;
2029 unsigned long nr_soft_scanned;
2031 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2032 gfp_zone(sc->gfp_mask), sc->nodemask) {
2033 if (!populated_zone(zone))
2036 * Take care memory controller reclaiming has small influence
2039 if (scanning_global_lru(sc)) {
2040 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2042 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2043 continue; /* Let kswapd poll it */
2045 * This steals pages from memory cgroups over softlimit
2046 * and returns the number of reclaimed pages and
2047 * scanned pages. This works for global memory pressure
2048 * and balancing, not for a memcg's limit.
2050 nr_soft_scanned = 0;
2051 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2052 sc->order, sc->gfp_mask,
2054 sc->nr_reclaimed += nr_soft_reclaimed;
2055 sc->nr_scanned += nr_soft_scanned;
2056 /* need some check for avoid more shrink_zone() */
2059 shrink_zone(priority, zone, sc);
2063 static bool zone_reclaimable(struct zone *zone)
2065 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2068 /* All zones in zonelist are unreclaimable? */
2069 static bool all_unreclaimable(struct zonelist *zonelist,
2070 struct scan_control *sc)
2075 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2076 gfp_zone(sc->gfp_mask), sc->nodemask) {
2077 if (!populated_zone(zone))
2079 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2081 if (!zone->all_unreclaimable)
2089 * This is the main entry point to direct page reclaim.
2091 * If a full scan of the inactive list fails to free enough memory then we
2092 * are "out of memory" and something needs to be killed.
2094 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2095 * high - the zone may be full of dirty or under-writeback pages, which this
2096 * caller can't do much about. We kick the writeback threads and take explicit
2097 * naps in the hope that some of these pages can be written. But if the
2098 * allocating task holds filesystem locks which prevent writeout this might not
2099 * work, and the allocation attempt will fail.
2101 * returns: 0, if no pages reclaimed
2102 * else, the number of pages reclaimed
2104 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2105 struct scan_control *sc,
2106 struct shrink_control *shrink)
2109 unsigned long total_scanned = 0;
2110 struct reclaim_state *reclaim_state = current->reclaim_state;
2113 unsigned long writeback_threshold;
2116 delayacct_freepages_start();
2118 if (scanning_global_lru(sc))
2119 count_vm_event(ALLOCSTALL);
2121 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2124 disable_swap_token(sc->mem_cgroup);
2125 shrink_zones(priority, zonelist, sc);
2127 * Don't shrink slabs when reclaiming memory from
2128 * over limit cgroups
2130 if (scanning_global_lru(sc)) {
2131 unsigned long lru_pages = 0;
2132 for_each_zone_zonelist(zone, z, zonelist,
2133 gfp_zone(sc->gfp_mask)) {
2134 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2137 lru_pages += zone_reclaimable_pages(zone);
2140 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2141 if (reclaim_state) {
2142 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2143 reclaim_state->reclaimed_slab = 0;
2146 total_scanned += sc->nr_scanned;
2147 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2151 * Try to write back as many pages as we just scanned. This
2152 * tends to cause slow streaming writers to write data to the
2153 * disk smoothly, at the dirtying rate, which is nice. But
2154 * that's undesirable in laptop mode, where we *want* lumpy
2155 * writeout. So in laptop mode, write out the whole world.
2157 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2158 if (total_scanned > writeback_threshold) {
2159 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2160 sc->may_writepage = 1;
2163 /* Take a nap, wait for some writeback to complete */
2164 if (!sc->hibernation_mode && sc->nr_scanned &&
2165 priority < DEF_PRIORITY - 2) {
2166 struct zone *preferred_zone;
2168 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2169 &cpuset_current_mems_allowed,
2171 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2176 delayacct_freepages_end();
2179 if (sc->nr_reclaimed)
2180 return sc->nr_reclaimed;
2183 * As hibernation is going on, kswapd is freezed so that it can't mark
2184 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2187 if (oom_killer_disabled)
2190 /* top priority shrink_zones still had more to do? don't OOM, then */
2191 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2197 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2198 gfp_t gfp_mask, nodemask_t *nodemask)
2200 unsigned long nr_reclaimed;
2201 struct scan_control sc = {
2202 .gfp_mask = gfp_mask,
2203 .may_writepage = !laptop_mode,
2204 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2207 .swappiness = vm_swappiness,
2210 .nodemask = nodemask,
2212 struct shrink_control shrink = {
2213 .gfp_mask = sc.gfp_mask,
2216 trace_mm_vmscan_direct_reclaim_begin(order,
2220 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2222 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2224 return nr_reclaimed;
2227 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2229 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2230 gfp_t gfp_mask, bool noswap,
2231 unsigned int swappiness,
2233 unsigned long *nr_scanned)
2235 struct scan_control sc = {
2237 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2238 .may_writepage = !laptop_mode,
2240 .may_swap = !noswap,
2241 .swappiness = swappiness,
2246 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2247 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2249 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2254 * NOTE: Although we can get the priority field, using it
2255 * here is not a good idea, since it limits the pages we can scan.
2256 * if we don't reclaim here, the shrink_zone from balance_pgdat
2257 * will pick up pages from other mem cgroup's as well. We hack
2258 * the priority and make it zero.
2260 shrink_zone(0, zone, &sc);
2262 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2264 *nr_scanned = sc.nr_scanned;
2265 return sc.nr_reclaimed;
2268 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2271 unsigned int swappiness)
2273 struct zonelist *zonelist;
2274 unsigned long nr_reclaimed;
2276 struct scan_control sc = {
2277 .may_writepage = !laptop_mode,
2279 .may_swap = !noswap,
2280 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2281 .swappiness = swappiness,
2283 .mem_cgroup = mem_cont,
2284 .nodemask = NULL, /* we don't care the placement */
2285 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2286 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2288 struct shrink_control shrink = {
2289 .gfp_mask = sc.gfp_mask,
2293 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2294 * take care of from where we get pages. So the node where we start the
2295 * scan does not need to be the current node.
2297 nid = mem_cgroup_select_victim_node(mem_cont);
2299 zonelist = NODE_DATA(nid)->node_zonelists;
2301 trace_mm_vmscan_memcg_reclaim_begin(0,
2305 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2307 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2309 return nr_reclaimed;
2314 * pgdat_balanced is used when checking if a node is balanced for high-order
2315 * allocations. Only zones that meet watermarks and are in a zone allowed
2316 * by the callers classzone_idx are added to balanced_pages. The total of
2317 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2318 * for the node to be considered balanced. Forcing all zones to be balanced
2319 * for high orders can cause excessive reclaim when there are imbalanced zones.
2320 * The choice of 25% is due to
2321 * o a 16M DMA zone that is balanced will not balance a zone on any
2322 * reasonable sized machine
2323 * o On all other machines, the top zone must be at least a reasonable
2324 * percentage of the middle zones. For example, on 32-bit x86, highmem
2325 * would need to be at least 256M for it to be balance a whole node.
2326 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2327 * to balance a node on its own. These seemed like reasonable ratios.
2329 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2332 unsigned long present_pages = 0;
2335 for (i = 0; i <= classzone_idx; i++)
2336 present_pages += pgdat->node_zones[i].present_pages;
2338 /* A special case here: if zone has no page, we think it's balanced */
2339 return balanced_pages >= (present_pages >> 2);
2342 /* is kswapd sleeping prematurely? */
2343 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2347 unsigned long balanced = 0;
2348 bool all_zones_ok = true;
2350 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2354 /* Check the watermark levels */
2355 for (i = 0; i <= classzone_idx; i++) {
2356 struct zone *zone = pgdat->node_zones + i;
2358 if (!populated_zone(zone))
2362 * balance_pgdat() skips over all_unreclaimable after
2363 * DEF_PRIORITY. Effectively, it considers them balanced so
2364 * they must be considered balanced here as well if kswapd
2367 if (zone->all_unreclaimable) {
2368 balanced += zone->present_pages;
2372 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2374 all_zones_ok = false;
2376 balanced += zone->present_pages;
2380 * For high-order requests, the balanced zones must contain at least
2381 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2385 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2387 return !all_zones_ok;
2391 * For kswapd, balance_pgdat() will work across all this node's zones until
2392 * they are all at high_wmark_pages(zone).
2394 * Returns the final order kswapd was reclaiming at
2396 * There is special handling here for zones which are full of pinned pages.
2397 * This can happen if the pages are all mlocked, or if they are all used by
2398 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2399 * What we do is to detect the case where all pages in the zone have been
2400 * scanned twice and there has been zero successful reclaim. Mark the zone as
2401 * dead and from now on, only perform a short scan. Basically we're polling
2402 * the zone for when the problem goes away.
2404 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2405 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2406 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2407 * lower zones regardless of the number of free pages in the lower zones. This
2408 * interoperates with the page allocator fallback scheme to ensure that aging
2409 * of pages is balanced across the zones.
2411 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2415 unsigned long balanced;
2418 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2419 unsigned long total_scanned;
2420 struct reclaim_state *reclaim_state = current->reclaim_state;
2421 unsigned long nr_soft_reclaimed;
2422 unsigned long nr_soft_scanned;
2423 struct scan_control sc = {
2424 .gfp_mask = GFP_KERNEL,
2428 * kswapd doesn't want to be bailed out while reclaim. because
2429 * we want to put equal scanning pressure on each zone.
2431 .nr_to_reclaim = ULONG_MAX,
2432 .swappiness = vm_swappiness,
2436 struct shrink_control shrink = {
2437 .gfp_mask = sc.gfp_mask,
2441 sc.nr_reclaimed = 0;
2442 sc.may_writepage = !laptop_mode;
2443 count_vm_event(PAGEOUTRUN);
2445 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2446 unsigned long lru_pages = 0;
2447 int has_under_min_watermark_zone = 0;
2449 /* The swap token gets in the way of swapout... */
2451 disable_swap_token(NULL);
2457 * Scan in the highmem->dma direction for the highest
2458 * zone which needs scanning
2460 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2461 struct zone *zone = pgdat->node_zones + i;
2463 if (!populated_zone(zone))
2466 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2470 * Do some background aging of the anon list, to give
2471 * pages a chance to be referenced before reclaiming.
2473 if (inactive_anon_is_low(zone, &sc))
2474 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2477 if (!zone_watermark_ok_safe(zone, order,
2478 high_wmark_pages(zone), 0, 0)) {
2486 for (i = 0; i <= end_zone; i++) {
2487 struct zone *zone = pgdat->node_zones + i;
2489 lru_pages += zone_reclaimable_pages(zone);
2493 * Now scan the zone in the dma->highmem direction, stopping
2494 * at the last zone which needs scanning.
2496 * We do this because the page allocator works in the opposite
2497 * direction. This prevents the page allocator from allocating
2498 * pages behind kswapd's direction of progress, which would
2499 * cause too much scanning of the lower zones.
2501 for (i = 0; i <= end_zone; i++) {
2502 struct zone *zone = pgdat->node_zones + i;
2504 unsigned long balance_gap;
2506 if (!populated_zone(zone))
2509 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2514 nr_soft_scanned = 0;
2516 * Call soft limit reclaim before calling shrink_zone.
2518 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2521 sc.nr_reclaimed += nr_soft_reclaimed;
2522 total_scanned += nr_soft_scanned;
2525 * We put equal pressure on every zone, unless
2526 * one zone has way too many pages free
2527 * already. The "too many pages" is defined
2528 * as the high wmark plus a "gap" where the
2529 * gap is either the low watermark or 1%
2530 * of the zone, whichever is smaller.
2532 balance_gap = min(low_wmark_pages(zone),
2533 (zone->present_pages +
2534 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2535 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2536 if (!zone_watermark_ok_safe(zone, order,
2537 high_wmark_pages(zone) + balance_gap,
2539 shrink_zone(priority, zone, &sc);
2541 reclaim_state->reclaimed_slab = 0;
2542 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2543 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2544 total_scanned += sc.nr_scanned;
2546 if (nr_slab == 0 && !zone_reclaimable(zone))
2547 zone->all_unreclaimable = 1;
2551 * If we've done a decent amount of scanning and
2552 * the reclaim ratio is low, start doing writepage
2553 * even in laptop mode
2555 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2556 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2557 sc.may_writepage = 1;
2559 if (zone->all_unreclaimable) {
2560 if (end_zone && end_zone == i)
2565 if (!zone_watermark_ok_safe(zone, order,
2566 high_wmark_pages(zone), end_zone, 0)) {
2569 * We are still under min water mark. This
2570 * means that we have a GFP_ATOMIC allocation
2571 * failure risk. Hurry up!
2573 if (!zone_watermark_ok_safe(zone, order,
2574 min_wmark_pages(zone), end_zone, 0))
2575 has_under_min_watermark_zone = 1;
2578 * If a zone reaches its high watermark,
2579 * consider it to be no longer congested. It's
2580 * possible there are dirty pages backed by
2581 * congested BDIs but as pressure is relieved,
2582 * spectulatively avoid congestion waits
2584 zone_clear_flag(zone, ZONE_CONGESTED);
2585 if (i <= *classzone_idx)
2586 balanced += zone->present_pages;
2590 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2591 break; /* kswapd: all done */
2593 * OK, kswapd is getting into trouble. Take a nap, then take
2594 * another pass across the zones.
2596 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2597 if (has_under_min_watermark_zone)
2598 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2600 congestion_wait(BLK_RW_ASYNC, HZ/10);
2604 * We do this so kswapd doesn't build up large priorities for
2605 * example when it is freeing in parallel with allocators. It
2606 * matches the direct reclaim path behaviour in terms of impact
2607 * on zone->*_priority.
2609 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2615 * order-0: All zones must meet high watermark for a balanced node
2616 * high-order: Balanced zones must make up at least 25% of the node
2617 * for the node to be balanced
2619 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2625 * Fragmentation may mean that the system cannot be
2626 * rebalanced for high-order allocations in all zones.
2627 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2628 * it means the zones have been fully scanned and are still
2629 * not balanced. For high-order allocations, there is
2630 * little point trying all over again as kswapd may
2633 * Instead, recheck all watermarks at order-0 as they
2634 * are the most important. If watermarks are ok, kswapd will go
2635 * back to sleep. High-order users can still perform direct
2636 * reclaim if they wish.
2638 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2639 order = sc.order = 0;
2645 * If kswapd was reclaiming at a higher order, it has the option of
2646 * sleeping without all zones being balanced. Before it does, it must
2647 * ensure that the watermarks for order-0 on *all* zones are met and
2648 * that the congestion flags are cleared. The congestion flag must
2649 * be cleared as kswapd is the only mechanism that clears the flag
2650 * and it is potentially going to sleep here.
2653 for (i = 0; i <= end_zone; i++) {
2654 struct zone *zone = pgdat->node_zones + i;
2656 if (!populated_zone(zone))
2659 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2662 /* Confirm the zone is balanced for order-0 */
2663 if (!zone_watermark_ok(zone, 0,
2664 high_wmark_pages(zone), 0, 0)) {
2665 order = sc.order = 0;
2669 /* If balanced, clear the congested flag */
2670 zone_clear_flag(zone, ZONE_CONGESTED);
2675 * Return the order we were reclaiming at so sleeping_prematurely()
2676 * makes a decision on the order we were last reclaiming at. However,
2677 * if another caller entered the allocator slow path while kswapd
2678 * was awake, order will remain at the higher level
2680 *classzone_idx = end_zone;
2684 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2689 if (freezing(current) || kthread_should_stop())
2692 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2694 /* Try to sleep for a short interval */
2695 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2696 remaining = schedule_timeout(HZ/10);
2697 finish_wait(&pgdat->kswapd_wait, &wait);
2698 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2702 * After a short sleep, check if it was a premature sleep. If not, then
2703 * go fully to sleep until explicitly woken up.
2705 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2706 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2709 * vmstat counters are not perfectly accurate and the estimated
2710 * value for counters such as NR_FREE_PAGES can deviate from the
2711 * true value by nr_online_cpus * threshold. To avoid the zone
2712 * watermarks being breached while under pressure, we reduce the
2713 * per-cpu vmstat threshold while kswapd is awake and restore
2714 * them before going back to sleep.
2716 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2718 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2721 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2723 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2725 finish_wait(&pgdat->kswapd_wait, &wait);
2729 * The background pageout daemon, started as a kernel thread
2730 * from the init process.
2732 * This basically trickles out pages so that we have _some_
2733 * free memory available even if there is no other activity
2734 * that frees anything up. This is needed for things like routing
2735 * etc, where we otherwise might have all activity going on in
2736 * asynchronous contexts that cannot page things out.
2738 * If there are applications that are active memory-allocators
2739 * (most normal use), this basically shouldn't matter.
2741 static int kswapd(void *p)
2743 unsigned long order, new_order;
2744 int classzone_idx, new_classzone_idx;
2745 pg_data_t *pgdat = (pg_data_t*)p;
2746 struct task_struct *tsk = current;
2748 struct reclaim_state reclaim_state = {
2749 .reclaimed_slab = 0,
2751 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2753 lockdep_set_current_reclaim_state(GFP_KERNEL);
2755 if (!cpumask_empty(cpumask))
2756 set_cpus_allowed_ptr(tsk, cpumask);
2757 current->reclaim_state = &reclaim_state;
2760 * Tell the memory management that we're a "memory allocator",
2761 * and that if we need more memory we should get access to it
2762 * regardless (see "__alloc_pages()"). "kswapd" should
2763 * never get caught in the normal page freeing logic.
2765 * (Kswapd normally doesn't need memory anyway, but sometimes
2766 * you need a small amount of memory in order to be able to
2767 * page out something else, and this flag essentially protects
2768 * us from recursively trying to free more memory as we're
2769 * trying to free the first piece of memory in the first place).
2771 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2774 order = new_order = 0;
2775 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2780 * If the last balance_pgdat was unsuccessful it's unlikely a
2781 * new request of a similar or harder type will succeed soon
2782 * so consider going to sleep on the basis we reclaimed at
2784 if (classzone_idx >= new_classzone_idx && order == new_order) {
2785 new_order = pgdat->kswapd_max_order;
2786 new_classzone_idx = pgdat->classzone_idx;
2787 pgdat->kswapd_max_order = 0;
2788 pgdat->classzone_idx = pgdat->nr_zones - 1;
2791 if (order < new_order || classzone_idx > new_classzone_idx) {
2793 * Don't sleep if someone wants a larger 'order'
2794 * allocation or has tigher zone constraints
2797 classzone_idx = new_classzone_idx;
2799 kswapd_try_to_sleep(pgdat, order, classzone_idx);
2800 order = pgdat->kswapd_max_order;
2801 classzone_idx = pgdat->classzone_idx;
2802 pgdat->kswapd_max_order = 0;
2803 pgdat->classzone_idx = pgdat->nr_zones - 1;
2806 ret = try_to_freeze();
2807 if (kthread_should_stop())
2811 * We can speed up thawing tasks if we don't call balance_pgdat
2812 * after returning from the refrigerator
2815 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2816 order = balance_pgdat(pgdat, order, &classzone_idx);
2823 * A zone is low on free memory, so wake its kswapd task to service it.
2825 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2829 if (!populated_zone(zone))
2832 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2834 pgdat = zone->zone_pgdat;
2835 if (pgdat->kswapd_max_order < order) {
2836 pgdat->kswapd_max_order = order;
2837 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2839 if (!waitqueue_active(&pgdat->kswapd_wait))
2841 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2844 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2845 wake_up_interruptible(&pgdat->kswapd_wait);
2849 * The reclaimable count would be mostly accurate.
2850 * The less reclaimable pages may be
2851 * - mlocked pages, which will be moved to unevictable list when encountered
2852 * - mapped pages, which may require several travels to be reclaimed
2853 * - dirty pages, which is not "instantly" reclaimable
2855 unsigned long global_reclaimable_pages(void)
2859 nr = global_page_state(NR_ACTIVE_FILE) +
2860 global_page_state(NR_INACTIVE_FILE);
2862 if (nr_swap_pages > 0)
2863 nr += global_page_state(NR_ACTIVE_ANON) +
2864 global_page_state(NR_INACTIVE_ANON);
2869 unsigned long zone_reclaimable_pages(struct zone *zone)
2873 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2874 zone_page_state(zone, NR_INACTIVE_FILE);
2876 if (nr_swap_pages > 0)
2877 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2878 zone_page_state(zone, NR_INACTIVE_ANON);
2883 #ifdef CONFIG_HIBERNATION
2885 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2888 * Rather than trying to age LRUs the aim is to preserve the overall
2889 * LRU order by reclaiming preferentially
2890 * inactive > active > active referenced > active mapped
2892 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2894 struct reclaim_state reclaim_state;
2895 struct scan_control sc = {
2896 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2900 .nr_to_reclaim = nr_to_reclaim,
2901 .hibernation_mode = 1,
2902 .swappiness = vm_swappiness,
2905 struct shrink_control shrink = {
2906 .gfp_mask = sc.gfp_mask,
2908 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2909 struct task_struct *p = current;
2910 unsigned long nr_reclaimed;
2912 p->flags |= PF_MEMALLOC;
2913 lockdep_set_current_reclaim_state(sc.gfp_mask);
2914 reclaim_state.reclaimed_slab = 0;
2915 p->reclaim_state = &reclaim_state;
2917 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2919 p->reclaim_state = NULL;
2920 lockdep_clear_current_reclaim_state();
2921 p->flags &= ~PF_MEMALLOC;
2923 return nr_reclaimed;
2925 #endif /* CONFIG_HIBERNATION */
2927 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2928 not required for correctness. So if the last cpu in a node goes
2929 away, we get changed to run anywhere: as the first one comes back,
2930 restore their cpu bindings. */
2931 static int __devinit cpu_callback(struct notifier_block *nfb,
2932 unsigned long action, void *hcpu)
2936 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2937 for_each_node_state(nid, N_HIGH_MEMORY) {
2938 pg_data_t *pgdat = NODE_DATA(nid);
2939 const struct cpumask *mask;
2941 mask = cpumask_of_node(pgdat->node_id);
2943 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2944 /* One of our CPUs online: restore mask */
2945 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2952 * This kswapd start function will be called by init and node-hot-add.
2953 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2955 int kswapd_run(int nid)
2957 pg_data_t *pgdat = NODE_DATA(nid);
2963 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2964 if (IS_ERR(pgdat->kswapd)) {
2965 /* failure at boot is fatal */
2966 BUG_ON(system_state == SYSTEM_BOOTING);
2967 printk("Failed to start kswapd on node %d\n",nid);
2974 * Called by memory hotplug when all memory in a node is offlined.
2976 void kswapd_stop(int nid)
2978 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2981 kthread_stop(kswapd);
2984 static int __init kswapd_init(void)
2989 for_each_node_state(nid, N_HIGH_MEMORY)
2991 hotcpu_notifier(cpu_callback, 0);
2995 module_init(kswapd_init)
3001 * If non-zero call zone_reclaim when the number of free pages falls below
3004 int zone_reclaim_mode __read_mostly;
3006 #define RECLAIM_OFF 0
3007 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3008 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3009 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3012 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3013 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3016 #define ZONE_RECLAIM_PRIORITY 4
3019 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3022 int sysctl_min_unmapped_ratio = 1;
3025 * If the number of slab pages in a zone grows beyond this percentage then
3026 * slab reclaim needs to occur.
3028 int sysctl_min_slab_ratio = 5;
3030 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3032 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3033 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3034 zone_page_state(zone, NR_ACTIVE_FILE);
3037 * It's possible for there to be more file mapped pages than
3038 * accounted for by the pages on the file LRU lists because
3039 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3041 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3044 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3045 static long zone_pagecache_reclaimable(struct zone *zone)
3047 long nr_pagecache_reclaimable;
3051 * If RECLAIM_SWAP is set, then all file pages are considered
3052 * potentially reclaimable. Otherwise, we have to worry about
3053 * pages like swapcache and zone_unmapped_file_pages() provides
3056 if (zone_reclaim_mode & RECLAIM_SWAP)
3057 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3059 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3061 /* If we can't clean pages, remove dirty pages from consideration */
3062 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3063 delta += zone_page_state(zone, NR_FILE_DIRTY);
3065 /* Watch for any possible underflows due to delta */
3066 if (unlikely(delta > nr_pagecache_reclaimable))
3067 delta = nr_pagecache_reclaimable;
3069 return nr_pagecache_reclaimable - delta;
3073 * Try to free up some pages from this zone through reclaim.
3075 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3077 /* Minimum pages needed in order to stay on node */
3078 const unsigned long nr_pages = 1 << order;
3079 struct task_struct *p = current;
3080 struct reclaim_state reclaim_state;
3082 struct scan_control sc = {
3083 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3084 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3086 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3088 .gfp_mask = gfp_mask,
3089 .swappiness = vm_swappiness,
3092 struct shrink_control shrink = {
3093 .gfp_mask = sc.gfp_mask,
3095 unsigned long nr_slab_pages0, nr_slab_pages1;
3099 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3100 * and we also need to be able to write out pages for RECLAIM_WRITE
3103 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3104 lockdep_set_current_reclaim_state(gfp_mask);
3105 reclaim_state.reclaimed_slab = 0;
3106 p->reclaim_state = &reclaim_state;
3108 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3110 * Free memory by calling shrink zone with increasing
3111 * priorities until we have enough memory freed.
3113 priority = ZONE_RECLAIM_PRIORITY;
3115 shrink_zone(priority, zone, &sc);
3117 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3120 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3121 if (nr_slab_pages0 > zone->min_slab_pages) {
3123 * shrink_slab() does not currently allow us to determine how
3124 * many pages were freed in this zone. So we take the current
3125 * number of slab pages and shake the slab until it is reduced
3126 * by the same nr_pages that we used for reclaiming unmapped
3129 * Note that shrink_slab will free memory on all zones and may
3133 unsigned long lru_pages = zone_reclaimable_pages(zone);
3135 /* No reclaimable slab or very low memory pressure */
3136 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3139 /* Freed enough memory */
3140 nr_slab_pages1 = zone_page_state(zone,
3141 NR_SLAB_RECLAIMABLE);
3142 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3147 * Update nr_reclaimed by the number of slab pages we
3148 * reclaimed from this zone.
3150 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3151 if (nr_slab_pages1 < nr_slab_pages0)
3152 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3155 p->reclaim_state = NULL;
3156 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3157 lockdep_clear_current_reclaim_state();
3158 return sc.nr_reclaimed >= nr_pages;
3161 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3167 * Zone reclaim reclaims unmapped file backed pages and
3168 * slab pages if we are over the defined limits.
3170 * A small portion of unmapped file backed pages is needed for
3171 * file I/O otherwise pages read by file I/O will be immediately
3172 * thrown out if the zone is overallocated. So we do not reclaim
3173 * if less than a specified percentage of the zone is used by
3174 * unmapped file backed pages.
3176 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3177 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3178 return ZONE_RECLAIM_FULL;
3180 if (zone->all_unreclaimable)
3181 return ZONE_RECLAIM_FULL;
3184 * Do not scan if the allocation should not be delayed.
3186 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3187 return ZONE_RECLAIM_NOSCAN;
3190 * Only run zone reclaim on the local zone or on zones that do not
3191 * have associated processors. This will favor the local processor
3192 * over remote processors and spread off node memory allocations
3193 * as wide as possible.
3195 node_id = zone_to_nid(zone);
3196 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3197 return ZONE_RECLAIM_NOSCAN;
3199 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3200 return ZONE_RECLAIM_NOSCAN;
3202 ret = __zone_reclaim(zone, gfp_mask, order);
3203 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3206 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3213 * page_evictable - test whether a page is evictable
3214 * @page: the page to test
3215 * @vma: the VMA in which the page is or will be mapped, may be NULL
3217 * Test whether page is evictable--i.e., should be placed on active/inactive
3218 * lists vs unevictable list. The vma argument is !NULL when called from the
3219 * fault path to determine how to instantate a new page.
3221 * Reasons page might not be evictable:
3222 * (1) page's mapping marked unevictable
3223 * (2) page is part of an mlocked VMA
3226 int page_evictable(struct page *page, struct vm_area_struct *vma)
3229 if (mapping_unevictable(page_mapping(page)))
3232 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3239 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3240 * @page: page to check evictability and move to appropriate lru list
3241 * @zone: zone page is in
3243 * Checks a page for evictability and moves the page to the appropriate
3246 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3247 * have PageUnevictable set.
3249 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3251 VM_BUG_ON(PageActive(page));
3254 ClearPageUnevictable(page);
3255 if (page_evictable(page, NULL)) {
3256 enum lru_list l = page_lru_base_type(page);
3258 __dec_zone_state(zone, NR_UNEVICTABLE);
3259 list_move(&page->lru, &zone->lru[l].list);
3260 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3261 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3262 __count_vm_event(UNEVICTABLE_PGRESCUED);
3265 * rotate unevictable list
3267 SetPageUnevictable(page);
3268 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3269 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3270 if (page_evictable(page, NULL))
3276 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3277 * @mapping: struct address_space to scan for evictable pages
3279 * Scan all pages in mapping. Check unevictable pages for
3280 * evictability and move them to the appropriate zone lru list.
3282 void scan_mapping_unevictable_pages(struct address_space *mapping)
3285 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3288 struct pagevec pvec;
3290 if (mapping->nrpages == 0)
3293 pagevec_init(&pvec, 0);
3294 while (next < end &&
3295 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3301 for (i = 0; i < pagevec_count(&pvec); i++) {
3302 struct page *page = pvec.pages[i];
3303 pgoff_t page_index = page->index;
3304 struct zone *pagezone = page_zone(page);
3307 if (page_index > next)
3311 if (pagezone != zone) {
3313 spin_unlock_irq(&zone->lru_lock);
3315 spin_lock_irq(&zone->lru_lock);
3318 if (PageLRU(page) && PageUnevictable(page))
3319 check_move_unevictable_page(page, zone);
3322 spin_unlock_irq(&zone->lru_lock);
3323 pagevec_release(&pvec);
3325 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3331 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3332 * @zone - zone of which to scan the unevictable list
3334 * Scan @zone's unevictable LRU lists to check for pages that have become
3335 * evictable. Move those that have to @zone's inactive list where they
3336 * become candidates for reclaim, unless shrink_inactive_zone() decides
3337 * to reactivate them. Pages that are still unevictable are rotated
3338 * back onto @zone's unevictable list.
3340 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3341 static void scan_zone_unevictable_pages(struct zone *zone)
3343 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
3345 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
3347 while (nr_to_scan > 0) {
3348 unsigned long batch_size = min(nr_to_scan,
3349 SCAN_UNEVICTABLE_BATCH_SIZE);
3351 spin_lock_irq(&zone->lru_lock);
3352 for (scan = 0; scan < batch_size; scan++) {
3353 struct page *page = lru_to_page(l_unevictable);
3355 if (!trylock_page(page))
3358 prefetchw_prev_lru_page(page, l_unevictable, flags);
3360 if (likely(PageLRU(page) && PageUnevictable(page)))
3361 check_move_unevictable_page(page, zone);
3365 spin_unlock_irq(&zone->lru_lock);
3367 nr_to_scan -= batch_size;
3373 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3375 * A really big hammer: scan all zones' unevictable LRU lists to check for
3376 * pages that have become evictable. Move those back to the zones'
3377 * inactive list where they become candidates for reclaim.
3378 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3379 * and we add swap to the system. As such, it runs in the context of a task
3380 * that has possibly/probably made some previously unevictable pages
3383 static void scan_all_zones_unevictable_pages(void)
3387 for_each_zone(zone) {
3388 scan_zone_unevictable_pages(zone);
3393 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3394 * all nodes' unevictable lists for evictable pages
3396 unsigned long scan_unevictable_pages;
3398 int scan_unevictable_handler(struct ctl_table *table, int write,
3399 void __user *buffer,
3400 size_t *length, loff_t *ppos)
3402 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3404 if (write && *(unsigned long *)table->data)
3405 scan_all_zones_unevictable_pages();
3407 scan_unevictable_pages = 0;
3413 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3414 * a specified node's per zone unevictable lists for evictable pages.
3417 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3418 struct sysdev_attribute *attr,
3421 return sprintf(buf, "0\n"); /* always zero; should fit... */
3424 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3425 struct sysdev_attribute *attr,
3426 const char *buf, size_t count)
3428 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3431 unsigned long req = strict_strtoul(buf, 10, &res);
3434 return 1; /* zero is no-op */
3436 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3437 if (!populated_zone(zone))
3439 scan_zone_unevictable_pages(zone);
3445 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3446 read_scan_unevictable_node,
3447 write_scan_unevictable_node);
3449 int scan_unevictable_register_node(struct node *node)
3451 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3454 void scan_unevictable_unregister_node(struct node *node)
3456 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);