4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #include <linux/module.h>
16 #include <linux/gfp.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
45 #include <linux/prefetch.h>
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
50 #include <linux/swapops.h>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
58 * reclaim_mode determines how the inactive list is shrunk
59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60 * RECLAIM_MODE_ASYNC: Do not block
61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 * page from the LRU and reclaim all pages within a
64 * naturally aligned range
65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66 * order-0 pages and then compact the zone
68 typedef unsigned __bitwise__ reclaim_mode_t;
69 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
70 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
71 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
72 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
73 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
76 /* Incremented by the number of inactive pages that were scanned */
77 unsigned long nr_scanned;
79 /* Number of pages freed so far during a call to shrink_zones() */
80 unsigned long nr_reclaimed;
82 /* How many pages shrink_list() should reclaim */
83 unsigned long nr_to_reclaim;
85 unsigned long hibernation_mode;
87 /* This context's GFP mask */
92 /* Can mapped pages be reclaimed? */
95 /* Can pages be swapped as part of reclaim? */
101 * Intend to reclaim enough continuous memory rather than reclaim
102 * enough amount of memory. i.e, mode for high order allocation.
104 reclaim_mode_t reclaim_mode;
106 /* Which cgroup do we reclaim from */
107 struct mem_cgroup *mem_cgroup;
110 * Nodemask of nodes allowed by the caller. If NULL, all nodes
113 nodemask_t *nodemask;
116 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
118 #ifdef ARCH_HAS_PREFETCH
119 #define prefetch_prev_lru_page(_page, _base, _field) \
121 if ((_page)->lru.prev != _base) { \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetch(&prev->_field); \
129 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
132 #ifdef ARCH_HAS_PREFETCHW
133 #define prefetchw_prev_lru_page(_page, _base, _field) \
135 if ((_page)->lru.prev != _base) { \
138 prev = lru_to_page(&(_page->lru)); \
139 prefetchw(&prev->_field); \
143 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
147 * From 0 .. 100. Higher means more swappy.
149 int vm_swappiness = 60;
150 long vm_total_pages; /* The total number of pages which the VM controls */
152 static LIST_HEAD(shrinker_list);
153 static DECLARE_RWSEM(shrinker_rwsem);
155 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
156 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
158 #define scanning_global_lru(sc) (1)
161 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
162 struct scan_control *sc)
164 if (!scanning_global_lru(sc))
165 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
167 return &zone->reclaim_stat;
170 static unsigned long zone_nr_lru_pages(struct zone *zone,
171 struct scan_control *sc, enum lru_list lru)
173 if (!scanning_global_lru(sc))
174 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup, zone, lru);
176 return zone_page_state(zone, NR_LRU_BASE + lru);
181 * Add a shrinker callback to be called from the vm
183 void register_shrinker(struct shrinker *shrinker)
186 down_write(&shrinker_rwsem);
187 list_add_tail(&shrinker->list, &shrinker_list);
188 up_write(&shrinker_rwsem);
190 EXPORT_SYMBOL(register_shrinker);
195 void unregister_shrinker(struct shrinker *shrinker)
197 down_write(&shrinker_rwsem);
198 list_del(&shrinker->list);
199 up_write(&shrinker_rwsem);
201 EXPORT_SYMBOL(unregister_shrinker);
203 static inline int do_shrinker_shrink(struct shrinker *shrinker,
204 struct shrink_control *sc,
205 unsigned long nr_to_scan)
207 sc->nr_to_scan = nr_to_scan;
208 return (*shrinker->shrink)(shrinker, sc);
211 #define SHRINK_BATCH 128
213 * Call the shrink functions to age shrinkable caches
215 * Here we assume it costs one seek to replace a lru page and that it also
216 * takes a seek to recreate a cache object. With this in mind we age equal
217 * percentages of the lru and ageable caches. This should balance the seeks
218 * generated by these structures.
220 * If the vm encountered mapped pages on the LRU it increase the pressure on
221 * slab to avoid swapping.
223 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
225 * `lru_pages' represents the number of on-LRU pages in all the zones which
226 * are eligible for the caller's allocation attempt. It is used for balancing
227 * slab reclaim versus page reclaim.
229 * Returns the number of slab objects which we shrunk.
231 unsigned long shrink_slab(struct shrink_control *shrink,
232 unsigned long nr_pages_scanned,
233 unsigned long lru_pages)
235 struct shrinker *shrinker;
236 unsigned long ret = 0;
238 if (nr_pages_scanned == 0)
239 nr_pages_scanned = SWAP_CLUSTER_MAX;
241 if (!down_read_trylock(&shrinker_rwsem)) {
242 /* Assume we'll be able to shrink next time */
247 list_for_each_entry(shrinker, &shrinker_list, list) {
248 unsigned long long delta;
249 unsigned long total_scan;
250 unsigned long max_pass;
254 long batch_size = shrinker->batch ? shrinker->batch
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 * We need to avoid excessive windup on filesystem shrinkers
281 * due to large numbers of GFP_NOFS allocations causing the
282 * shrinkers to return -1 all the time. This results in a large
283 * nr being built up so when a shrink that can do some work
284 * comes along it empties the entire cache due to nr >>>
285 * max_pass. This is bad for sustaining a working set in
288 * Hence only allow the shrinker to scan the entire cache when
289 * a large delta change is calculated directly.
291 if (delta < max_pass / 4)
292 total_scan = min(total_scan, max_pass / 2);
295 * Avoid risking looping forever due to too large nr value:
296 * never try to free more than twice the estimate number of
299 if (total_scan > max_pass * 2)
300 total_scan = max_pass * 2;
302 trace_mm_shrink_slab_start(shrinker, shrink, nr,
303 nr_pages_scanned, lru_pages,
304 max_pass, delta, total_scan);
306 while (total_scan >= batch_size) {
309 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
310 shrink_ret = do_shrinker_shrink(shrinker, shrink,
312 if (shrink_ret == -1)
314 if (shrink_ret < nr_before)
315 ret += nr_before - shrink_ret;
316 count_vm_events(SLABS_SCANNED, batch_size);
317 total_scan -= batch_size;
323 * move the unused scan count back into the shrinker in a
324 * manner that handles concurrent updates. If we exhausted the
325 * scan, there is no need to do an update.
329 new_nr = total_scan + nr;
332 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
334 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
336 up_read(&shrinker_rwsem);
342 static void set_reclaim_mode(int priority, struct scan_control *sc,
345 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
348 * Initially assume we are entering either lumpy reclaim or
349 * reclaim/compaction.Depending on the order, we will either set the
350 * sync mode or just reclaim order-0 pages later.
352 if (COMPACTION_BUILD)
353 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
355 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
358 * Avoid using lumpy reclaim or reclaim/compaction if possible by
359 * restricting when its set to either costly allocations or when
360 * under memory pressure
362 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
363 sc->reclaim_mode |= syncmode;
364 else if (sc->order && priority < DEF_PRIORITY - 2)
365 sc->reclaim_mode |= syncmode;
367 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
370 static void reset_reclaim_mode(struct scan_control *sc)
372 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
375 static inline int is_page_cache_freeable(struct page *page)
378 * A freeable page cache page is referenced only by the caller
379 * that isolated the page, the page cache radix tree and
380 * optional buffer heads at page->private.
382 return page_count(page) - page_has_private(page) == 2;
385 static int may_write_to_queue(struct backing_dev_info *bdi,
386 struct scan_control *sc)
388 if (current->flags & PF_SWAPWRITE)
390 if (!bdi_write_congested(bdi))
392 if (bdi == current->backing_dev_info)
395 /* lumpy reclaim for hugepage often need a lot of write */
396 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
402 * We detected a synchronous write error writing a page out. Probably
403 * -ENOSPC. We need to propagate that into the address_space for a subsequent
404 * fsync(), msync() or close().
406 * The tricky part is that after writepage we cannot touch the mapping: nothing
407 * prevents it from being freed up. But we have a ref on the page and once
408 * that page is locked, the mapping is pinned.
410 * We're allowed to run sleeping lock_page() here because we know the caller has
413 static void handle_write_error(struct address_space *mapping,
414 struct page *page, int error)
417 if (page_mapping(page) == mapping)
418 mapping_set_error(mapping, error);
422 /* possible outcome of pageout() */
424 /* failed to write page out, page is locked */
426 /* move page to the active list, page is locked */
428 /* page has been sent to the disk successfully, page is unlocked */
430 /* page is clean and locked */
435 * pageout is called by shrink_page_list() for each dirty page.
436 * Calls ->writepage().
438 static pageout_t pageout(struct page *page, struct address_space *mapping,
439 struct scan_control *sc)
442 * If the page is dirty, only perform writeback if that write
443 * will be non-blocking. To prevent this allocation from being
444 * stalled by pagecache activity. But note that there may be
445 * stalls if we need to run get_block(). We could test
446 * PagePrivate for that.
448 * If this process is currently in __generic_file_aio_write() against
449 * this page's queue, we can perform writeback even if that
452 * If the page is swapcache, write it back even if that would
453 * block, for some throttling. This happens by accident, because
454 * swap_backing_dev_info is bust: it doesn't reflect the
455 * congestion state of the swapdevs. Easy to fix, if needed.
457 if (!is_page_cache_freeable(page))
461 * Some data journaling orphaned pages can have
462 * page->mapping == NULL while being dirty with clean buffers.
464 if (page_has_private(page)) {
465 if (try_to_free_buffers(page)) {
466 ClearPageDirty(page);
467 printk("%s: orphaned page\n", __func__);
473 if (mapping->a_ops->writepage == NULL)
474 return PAGE_ACTIVATE;
475 if (!may_write_to_queue(mapping->backing_dev_info, sc))
478 if (clear_page_dirty_for_io(page)) {
480 struct writeback_control wbc = {
481 .sync_mode = WB_SYNC_NONE,
482 .nr_to_write = SWAP_CLUSTER_MAX,
484 .range_end = LLONG_MAX,
488 SetPageReclaim(page);
489 res = mapping->a_ops->writepage(page, &wbc);
491 handle_write_error(mapping, page, res);
492 if (res == AOP_WRITEPAGE_ACTIVATE) {
493 ClearPageReclaim(page);
494 return PAGE_ACTIVATE;
498 * Wait on writeback if requested to. This happens when
499 * direct reclaiming a large contiguous area and the
500 * first attempt to free a range of pages fails.
502 if (PageWriteback(page) &&
503 (sc->reclaim_mode & RECLAIM_MODE_SYNC))
504 wait_on_page_writeback(page);
506 if (!PageWriteback(page)) {
507 /* synchronous write or broken a_ops? */
508 ClearPageReclaim(page);
510 trace_mm_vmscan_writepage(page,
511 trace_reclaim_flags(page, sc->reclaim_mode));
512 inc_zone_page_state(page, NR_VMSCAN_WRITE);
520 * Same as remove_mapping, but if the page is removed from the mapping, it
521 * gets returned with a refcount of 0.
523 static int __remove_mapping(struct address_space *mapping, struct page *page)
525 BUG_ON(!PageLocked(page));
526 BUG_ON(mapping != page_mapping(page));
528 spin_lock_irq(&mapping->tree_lock);
530 * The non racy check for a busy page.
532 * Must be careful with the order of the tests. When someone has
533 * a ref to the page, it may be possible that they dirty it then
534 * drop the reference. So if PageDirty is tested before page_count
535 * here, then the following race may occur:
537 * get_user_pages(&page);
538 * [user mapping goes away]
540 * !PageDirty(page) [good]
541 * SetPageDirty(page);
543 * !page_count(page) [good, discard it]
545 * [oops, our write_to data is lost]
547 * Reversing the order of the tests ensures such a situation cannot
548 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
549 * load is not satisfied before that of page->_count.
551 * Note that if SetPageDirty is always performed via set_page_dirty,
552 * and thus under tree_lock, then this ordering is not required.
554 if (!page_freeze_refs(page, 2))
556 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
557 if (unlikely(PageDirty(page))) {
558 page_unfreeze_refs(page, 2);
562 if (PageSwapCache(page)) {
563 swp_entry_t swap = { .val = page_private(page) };
564 __delete_from_swap_cache(page);
565 spin_unlock_irq(&mapping->tree_lock);
566 swapcache_free(swap, page);
568 void (*freepage)(struct page *);
570 freepage = mapping->a_ops->freepage;
572 __delete_from_page_cache(page);
573 spin_unlock_irq(&mapping->tree_lock);
574 mem_cgroup_uncharge_cache_page(page);
576 if (freepage != NULL)
583 spin_unlock_irq(&mapping->tree_lock);
588 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
589 * someone else has a ref on the page, abort and return 0. If it was
590 * successfully detached, return 1. Assumes the caller has a single ref on
593 int remove_mapping(struct address_space *mapping, struct page *page)
595 if (__remove_mapping(mapping, page)) {
597 * Unfreezing the refcount with 1 rather than 2 effectively
598 * drops the pagecache ref for us without requiring another
601 page_unfreeze_refs(page, 1);
608 * putback_lru_page - put previously isolated page onto appropriate LRU list
609 * @page: page to be put back to appropriate lru list
611 * Add previously isolated @page to appropriate LRU list.
612 * Page may still be unevictable for other reasons.
614 * lru_lock must not be held, interrupts must be enabled.
616 void putback_lru_page(struct page *page)
619 int active = !!TestClearPageActive(page);
620 int was_unevictable = PageUnevictable(page);
622 VM_BUG_ON(PageLRU(page));
625 ClearPageUnevictable(page);
627 if (page_evictable(page, NULL)) {
629 * For evictable pages, we can use the cache.
630 * In event of a race, worst case is we end up with an
631 * unevictable page on [in]active list.
632 * We know how to handle that.
634 lru = active + page_lru_base_type(page);
635 lru_cache_add_lru(page, lru);
638 * Put unevictable pages directly on zone's unevictable
641 lru = LRU_UNEVICTABLE;
642 add_page_to_unevictable_list(page);
644 * When racing with an mlock clearing (page is
645 * unlocked), make sure that if the other thread does
646 * not observe our setting of PG_lru and fails
647 * isolation, we see PG_mlocked cleared below and move
648 * the page back to the evictable list.
650 * The other side is TestClearPageMlocked().
656 * page's status can change while we move it among lru. If an evictable
657 * page is on unevictable list, it never be freed. To avoid that,
658 * check after we added it to the list, again.
660 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
661 if (!isolate_lru_page(page)) {
665 /* This means someone else dropped this page from LRU
666 * So, it will be freed or putback to LRU again. There is
667 * nothing to do here.
671 if (was_unevictable && lru != LRU_UNEVICTABLE)
672 count_vm_event(UNEVICTABLE_PGRESCUED);
673 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
674 count_vm_event(UNEVICTABLE_PGCULLED);
676 put_page(page); /* drop ref from isolate */
679 enum page_references {
681 PAGEREF_RECLAIM_CLEAN,
686 static enum page_references page_check_references(struct page *page,
687 struct scan_control *sc)
689 int referenced_ptes, referenced_page;
690 unsigned long vm_flags;
692 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
693 referenced_page = TestClearPageReferenced(page);
695 /* Lumpy reclaim - ignore references */
696 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
697 return PAGEREF_RECLAIM;
700 * Mlock lost the isolation race with us. Let try_to_unmap()
701 * move the page to the unevictable list.
703 if (vm_flags & VM_LOCKED)
704 return PAGEREF_RECLAIM;
706 if (referenced_ptes) {
708 return PAGEREF_ACTIVATE;
710 * All mapped pages start out with page table
711 * references from the instantiating fault, so we need
712 * to look twice if a mapped file page is used more
715 * Mark it and spare it for another trip around the
716 * inactive list. Another page table reference will
717 * lead to its activation.
719 * Note: the mark is set for activated pages as well
720 * so that recently deactivated but used pages are
723 SetPageReferenced(page);
726 return PAGEREF_ACTIVATE;
731 /* Reclaim if clean, defer dirty pages to writeback */
732 if (referenced_page && !PageSwapBacked(page))
733 return PAGEREF_RECLAIM_CLEAN;
735 return PAGEREF_RECLAIM;
738 static noinline_for_stack void free_page_list(struct list_head *free_pages)
740 struct pagevec freed_pvec;
741 struct page *page, *tmp;
743 pagevec_init(&freed_pvec, 1);
745 list_for_each_entry_safe(page, tmp, free_pages, lru) {
746 list_del(&page->lru);
747 if (!pagevec_add(&freed_pvec, page)) {
748 __pagevec_free(&freed_pvec);
749 pagevec_reinit(&freed_pvec);
753 pagevec_free(&freed_pvec);
757 * shrink_page_list() returns the number of reclaimed pages
759 static unsigned long shrink_page_list(struct list_head *page_list,
761 struct scan_control *sc)
763 LIST_HEAD(ret_pages);
764 LIST_HEAD(free_pages);
766 unsigned long nr_dirty = 0;
767 unsigned long nr_congested = 0;
768 unsigned long nr_reclaimed = 0;
772 while (!list_empty(page_list)) {
773 enum page_references references;
774 struct address_space *mapping;
780 page = lru_to_page(page_list);
781 list_del(&page->lru);
783 if (!trylock_page(page))
786 VM_BUG_ON(PageActive(page));
787 VM_BUG_ON(page_zone(page) != zone);
791 if (unlikely(!page_evictable(page, NULL)))
794 if (!sc->may_unmap && page_mapped(page))
797 /* Double the slab pressure for mapped and swapcache pages */
798 if (page_mapped(page) || PageSwapCache(page))
801 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
802 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
804 if (PageWriteback(page)) {
806 * Synchronous reclaim is performed in two passes,
807 * first an asynchronous pass over the list to
808 * start parallel writeback, and a second synchronous
809 * pass to wait for the IO to complete. Wait here
810 * for any page for which writeback has already
813 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
815 wait_on_page_writeback(page);
822 references = page_check_references(page, sc);
823 switch (references) {
824 case PAGEREF_ACTIVATE:
825 goto activate_locked;
828 case PAGEREF_RECLAIM:
829 case PAGEREF_RECLAIM_CLEAN:
830 ; /* try to reclaim the page below */
834 * Anonymous process memory has backing store?
835 * Try to allocate it some swap space here.
837 if (PageAnon(page) && !PageSwapCache(page)) {
838 if (!(sc->gfp_mask & __GFP_IO))
840 if (!add_to_swap(page))
841 goto activate_locked;
845 mapping = page_mapping(page);
848 * The page is mapped into the page tables of one or more
849 * processes. Try to unmap it here.
851 if (page_mapped(page) && mapping) {
852 switch (try_to_unmap(page, TTU_UNMAP)) {
854 goto activate_locked;
860 ; /* try to free the page below */
864 if (PageDirty(page)) {
867 if (references == PAGEREF_RECLAIM_CLEAN)
871 if (!sc->may_writepage)
874 /* Page is dirty, try to write it out here */
875 switch (pageout(page, mapping, sc)) {
880 goto activate_locked;
882 if (PageWriteback(page))
888 * A synchronous write - probably a ramdisk. Go
889 * ahead and try to reclaim the page.
891 if (!trylock_page(page))
893 if (PageDirty(page) || PageWriteback(page))
895 mapping = page_mapping(page);
897 ; /* try to free the page below */
902 * If the page has buffers, try to free the buffer mappings
903 * associated with this page. If we succeed we try to free
906 * We do this even if the page is PageDirty().
907 * try_to_release_page() does not perform I/O, but it is
908 * possible for a page to have PageDirty set, but it is actually
909 * clean (all its buffers are clean). This happens if the
910 * buffers were written out directly, with submit_bh(). ext3
911 * will do this, as well as the blockdev mapping.
912 * try_to_release_page() will discover that cleanness and will
913 * drop the buffers and mark the page clean - it can be freed.
915 * Rarely, pages can have buffers and no ->mapping. These are
916 * the pages which were not successfully invalidated in
917 * truncate_complete_page(). We try to drop those buffers here
918 * and if that worked, and the page is no longer mapped into
919 * process address space (page_count == 1) it can be freed.
920 * Otherwise, leave the page on the LRU so it is swappable.
922 if (page_has_private(page)) {
923 if (!try_to_release_page(page, sc->gfp_mask))
924 goto activate_locked;
925 if (!mapping && page_count(page) == 1) {
927 if (put_page_testzero(page))
931 * rare race with speculative reference.
932 * the speculative reference will free
933 * this page shortly, so we may
934 * increment nr_reclaimed here (and
935 * leave it off the LRU).
943 if (!mapping || !__remove_mapping(mapping, page))
947 * At this point, we have no other references and there is
948 * no way to pick any more up (removed from LRU, removed
949 * from pagecache). Can use non-atomic bitops now (and
950 * we obviously don't have to worry about waking up a process
951 * waiting on the page lock, because there are no references.
953 __clear_page_locked(page);
958 * Is there need to periodically free_page_list? It would
959 * appear not as the counts should be low
961 list_add(&page->lru, &free_pages);
965 if (PageSwapCache(page))
966 try_to_free_swap(page);
968 putback_lru_page(page);
969 reset_reclaim_mode(sc);
973 /* Not a candidate for swapping, so reclaim swap space. */
974 if (PageSwapCache(page) && vm_swap_full())
975 try_to_free_swap(page);
976 VM_BUG_ON(PageActive(page));
982 reset_reclaim_mode(sc);
984 list_add(&page->lru, &ret_pages);
985 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
989 * Tag a zone as congested if all the dirty pages encountered were
990 * backed by a congested BDI. In this case, reclaimers should just
991 * back off and wait for congestion to clear because further reclaim
992 * will encounter the same problem
994 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
995 zone_set_flag(zone, ZONE_CONGESTED);
997 free_page_list(&free_pages);
999 list_splice(&ret_pages, page_list);
1000 count_vm_events(PGACTIVATE, pgactivate);
1001 return nr_reclaimed;
1005 * Attempt to remove the specified page from its LRU. Only take this page
1006 * if it is of the appropriate PageActive status. Pages which are being
1007 * freed elsewhere are also ignored.
1009 * page: page to consider
1010 * mode: one of the LRU isolation modes defined above
1012 * returns 0 on success, -ve errno on failure.
1014 int __isolate_lru_page(struct page *page, int mode, int file)
1018 /* Only take pages on the LRU. */
1023 * When checking the active state, we need to be sure we are
1024 * dealing with comparible boolean values. Take the logical not
1027 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
1030 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
1034 * When this function is being called for lumpy reclaim, we
1035 * initially look into all LRU pages, active, inactive and
1036 * unevictable; only give shrink_page_list evictable pages.
1038 if (PageUnevictable(page))
1043 if (likely(get_page_unless_zero(page))) {
1045 * Be careful not to clear PageLRU until after we're
1046 * sure the page is not being freed elsewhere -- the
1047 * page release code relies on it.
1057 * zone->lru_lock is heavily contended. Some of the functions that
1058 * shrink the lists perform better by taking out a batch of pages
1059 * and working on them outside the LRU lock.
1061 * For pagecache intensive workloads, this function is the hottest
1062 * spot in the kernel (apart from copy_*_user functions).
1064 * Appropriate locks must be held before calling this function.
1066 * @nr_to_scan: The number of pages to look through on the list.
1067 * @src: The LRU list to pull pages off.
1068 * @dst: The temp list to put pages on to.
1069 * @scanned: The number of pages that were scanned.
1070 * @order: The caller's attempted allocation order
1071 * @mode: One of the LRU isolation modes
1072 * @file: True [1] if isolating file [!anon] pages
1074 * returns how many pages were moved onto *@dst.
1076 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1077 struct list_head *src, struct list_head *dst,
1078 unsigned long *scanned, int order, int mode, int file)
1080 unsigned long nr_taken = 0;
1081 unsigned long nr_lumpy_taken = 0;
1082 unsigned long nr_lumpy_dirty = 0;
1083 unsigned long nr_lumpy_failed = 0;
1086 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1089 unsigned long end_pfn;
1090 unsigned long page_pfn;
1093 page = lru_to_page(src);
1094 prefetchw_prev_lru_page(page, src, flags);
1096 VM_BUG_ON(!PageLRU(page));
1098 switch (__isolate_lru_page(page, mode, file)) {
1100 list_move(&page->lru, dst);
1101 mem_cgroup_del_lru(page);
1102 nr_taken += hpage_nr_pages(page);
1106 /* else it is being freed elsewhere */
1107 list_move(&page->lru, src);
1108 mem_cgroup_rotate_lru_list(page, page_lru(page));
1119 * Attempt to take all pages in the order aligned region
1120 * surrounding the tag page. Only take those pages of
1121 * the same active state as that tag page. We may safely
1122 * round the target page pfn down to the requested order
1123 * as the mem_map is guaranteed valid out to MAX_ORDER,
1124 * where that page is in a different zone we will detect
1125 * it from its zone id and abort this block scan.
1127 zone_id = page_zone_id(page);
1128 page_pfn = page_to_pfn(page);
1129 pfn = page_pfn & ~((1 << order) - 1);
1130 end_pfn = pfn + (1 << order);
1131 for (; pfn < end_pfn; pfn++) {
1132 struct page *cursor_page;
1134 /* The target page is in the block, ignore it. */
1135 if (unlikely(pfn == page_pfn))
1138 /* Avoid holes within the zone. */
1139 if (unlikely(!pfn_valid_within(pfn)))
1142 cursor_page = pfn_to_page(pfn);
1144 /* Check that we have not crossed a zone boundary. */
1145 if (unlikely(page_zone_id(cursor_page) != zone_id))
1149 * If we don't have enough swap space, reclaiming of
1150 * anon page which don't already have a swap slot is
1153 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1154 !PageSwapCache(cursor_page))
1157 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1158 list_move(&cursor_page->lru, dst);
1159 mem_cgroup_del_lru(cursor_page);
1160 nr_taken += hpage_nr_pages(page);
1162 if (PageDirty(cursor_page))
1167 * Check if the page is freed already.
1169 * We can't use page_count() as that
1170 * requires compound_head and we don't
1171 * have a pin on the page here. If a
1172 * page is tail, we may or may not
1173 * have isolated the head, so assume
1174 * it's not free, it'd be tricky to
1175 * track the head status without a
1178 if (!PageTail(cursor_page) &&
1179 !atomic_read(&cursor_page->_count))
1185 /* If we break out of the loop above, lumpy reclaim failed */
1192 trace_mm_vmscan_lru_isolate(order,
1195 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1200 static unsigned long isolate_pages_global(unsigned long nr,
1201 struct list_head *dst,
1202 unsigned long *scanned, int order,
1203 int mode, struct zone *z,
1204 int active, int file)
1211 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1216 * clear_active_flags() is a helper for shrink_active_list(), clearing
1217 * any active bits from the pages in the list.
1219 static unsigned long clear_active_flags(struct list_head *page_list,
1220 unsigned int *count)
1226 list_for_each_entry(page, page_list, lru) {
1227 int numpages = hpage_nr_pages(page);
1228 lru = page_lru_base_type(page);
1229 if (PageActive(page)) {
1231 ClearPageActive(page);
1232 nr_active += numpages;
1235 count[lru] += numpages;
1242 * isolate_lru_page - tries to isolate a page from its LRU list
1243 * @page: page to isolate from its LRU list
1245 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1246 * vmstat statistic corresponding to whatever LRU list the page was on.
1248 * Returns 0 if the page was removed from an LRU list.
1249 * Returns -EBUSY if the page was not on an LRU list.
1251 * The returned page will have PageLRU() cleared. If it was found on
1252 * the active list, it will have PageActive set. If it was found on
1253 * the unevictable list, it will have the PageUnevictable bit set. That flag
1254 * may need to be cleared by the caller before letting the page go.
1256 * The vmstat statistic corresponding to the list on which the page was
1257 * found will be decremented.
1260 * (1) Must be called with an elevated refcount on the page. This is a
1261 * fundamentnal difference from isolate_lru_pages (which is called
1262 * without a stable reference).
1263 * (2) the lru_lock must not be held.
1264 * (3) interrupts must be enabled.
1266 int isolate_lru_page(struct page *page)
1270 VM_BUG_ON(!page_count(page));
1272 if (PageLRU(page)) {
1273 struct zone *zone = page_zone(page);
1275 spin_lock_irq(&zone->lru_lock);
1276 if (PageLRU(page)) {
1277 int lru = page_lru(page);
1282 del_page_from_lru_list(zone, page, lru);
1284 spin_unlock_irq(&zone->lru_lock);
1290 * Are there way too many processes in the direct reclaim path already?
1292 static int too_many_isolated(struct zone *zone, int file,
1293 struct scan_control *sc)
1295 unsigned long inactive, isolated;
1297 if (current_is_kswapd())
1300 if (!scanning_global_lru(sc))
1304 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1305 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1307 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1308 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1311 return isolated > inactive;
1315 * TODO: Try merging with migrations version of putback_lru_pages
1317 static noinline_for_stack void
1318 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1319 unsigned long nr_anon, unsigned long nr_file,
1320 struct list_head *page_list)
1323 struct pagevec pvec;
1324 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1326 pagevec_init(&pvec, 1);
1329 * Put back any unfreeable pages.
1331 spin_lock(&zone->lru_lock);
1332 while (!list_empty(page_list)) {
1334 page = lru_to_page(page_list);
1335 VM_BUG_ON(PageLRU(page));
1336 list_del(&page->lru);
1337 if (unlikely(!page_evictable(page, NULL))) {
1338 spin_unlock_irq(&zone->lru_lock);
1339 putback_lru_page(page);
1340 spin_lock_irq(&zone->lru_lock);
1344 lru = page_lru(page);
1345 add_page_to_lru_list(zone, page, lru);
1346 if (is_active_lru(lru)) {
1347 int file = is_file_lru(lru);
1348 int numpages = hpage_nr_pages(page);
1349 reclaim_stat->recent_rotated[file] += numpages;
1351 if (!pagevec_add(&pvec, page)) {
1352 spin_unlock_irq(&zone->lru_lock);
1353 __pagevec_release(&pvec);
1354 spin_lock_irq(&zone->lru_lock);
1357 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1358 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1360 spin_unlock_irq(&zone->lru_lock);
1361 pagevec_release(&pvec);
1364 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1365 struct scan_control *sc,
1366 unsigned long *nr_anon,
1367 unsigned long *nr_file,
1368 struct list_head *isolated_list)
1370 unsigned long nr_active;
1371 unsigned int count[NR_LRU_LISTS] = { 0, };
1372 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1374 nr_active = clear_active_flags(isolated_list, count);
1375 __count_vm_events(PGDEACTIVATE, nr_active);
1377 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1378 -count[LRU_ACTIVE_FILE]);
1379 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1380 -count[LRU_INACTIVE_FILE]);
1381 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1382 -count[LRU_ACTIVE_ANON]);
1383 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1384 -count[LRU_INACTIVE_ANON]);
1386 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1387 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1388 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1389 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1391 reclaim_stat->recent_scanned[0] += *nr_anon;
1392 reclaim_stat->recent_scanned[1] += *nr_file;
1396 * Returns true if the caller should wait to clean dirty/writeback pages.
1398 * If we are direct reclaiming for contiguous pages and we do not reclaim
1399 * everything in the list, try again and wait for writeback IO to complete.
1400 * This will stall high-order allocations noticeably. Only do that when really
1401 * need to free the pages under high memory pressure.
1403 static inline bool should_reclaim_stall(unsigned long nr_taken,
1404 unsigned long nr_freed,
1406 struct scan_control *sc)
1408 int lumpy_stall_priority;
1410 /* kswapd should not stall on sync IO */
1411 if (current_is_kswapd())
1414 /* Only stall on lumpy reclaim */
1415 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1418 /* If we have relaimed everything on the isolated list, no stall */
1419 if (nr_freed == nr_taken)
1423 * For high-order allocations, there are two stall thresholds.
1424 * High-cost allocations stall immediately where as lower
1425 * order allocations such as stacks require the scanning
1426 * priority to be much higher before stalling.
1428 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1429 lumpy_stall_priority = DEF_PRIORITY;
1431 lumpy_stall_priority = DEF_PRIORITY / 3;
1433 return priority <= lumpy_stall_priority;
1437 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1438 * of reclaimed pages
1440 static noinline_for_stack unsigned long
1441 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1442 struct scan_control *sc, int priority, int file)
1444 LIST_HEAD(page_list);
1445 unsigned long nr_scanned;
1446 unsigned long nr_reclaimed = 0;
1447 unsigned long nr_taken;
1448 unsigned long nr_anon;
1449 unsigned long nr_file;
1451 while (unlikely(too_many_isolated(zone, file, sc))) {
1452 congestion_wait(BLK_RW_ASYNC, HZ/10);
1454 /* We are about to die and free our memory. Return now. */
1455 if (fatal_signal_pending(current))
1456 return SWAP_CLUSTER_MAX;
1459 set_reclaim_mode(priority, sc, false);
1461 spin_lock_irq(&zone->lru_lock);
1463 if (scanning_global_lru(sc)) {
1464 nr_taken = isolate_pages_global(nr_to_scan,
1465 &page_list, &nr_scanned, sc->order,
1466 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1467 ISOLATE_BOTH : ISOLATE_INACTIVE,
1469 zone->pages_scanned += nr_scanned;
1470 if (current_is_kswapd())
1471 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1474 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1477 nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
1478 &page_list, &nr_scanned, sc->order,
1479 sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
1480 ISOLATE_BOTH : ISOLATE_INACTIVE,
1481 zone, sc->mem_cgroup,
1484 * mem_cgroup_isolate_pages() keeps track of
1485 * scanned pages on its own.
1489 if (nr_taken == 0) {
1490 spin_unlock_irq(&zone->lru_lock);
1494 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1496 spin_unlock_irq(&zone->lru_lock);
1498 nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1500 /* Check if we should syncronously wait for writeback */
1501 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1502 set_reclaim_mode(priority, sc, true);
1503 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1506 local_irq_disable();
1507 if (current_is_kswapd())
1508 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1509 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1511 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1513 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1515 nr_scanned, nr_reclaimed,
1517 trace_shrink_flags(file, sc->reclaim_mode));
1518 return nr_reclaimed;
1522 * This moves pages from the active list to the inactive list.
1524 * We move them the other way if the page is referenced by one or more
1525 * processes, from rmap.
1527 * If the pages are mostly unmapped, the processing is fast and it is
1528 * appropriate to hold zone->lru_lock across the whole operation. But if
1529 * the pages are mapped, the processing is slow (page_referenced()) so we
1530 * should drop zone->lru_lock around each page. It's impossible to balance
1531 * this, so instead we remove the pages from the LRU while processing them.
1532 * It is safe to rely on PG_active against the non-LRU pages in here because
1533 * nobody will play with that bit on a non-LRU page.
1535 * The downside is that we have to touch page->_count against each page.
1536 * But we had to alter page->flags anyway.
1539 static void move_active_pages_to_lru(struct zone *zone,
1540 struct list_head *list,
1543 unsigned long pgmoved = 0;
1544 struct pagevec pvec;
1547 pagevec_init(&pvec, 1);
1549 while (!list_empty(list)) {
1550 page = lru_to_page(list);
1552 VM_BUG_ON(PageLRU(page));
1555 list_move(&page->lru, &zone->lru[lru].list);
1556 mem_cgroup_add_lru_list(page, lru);
1557 pgmoved += hpage_nr_pages(page);
1559 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1560 spin_unlock_irq(&zone->lru_lock);
1561 if (buffer_heads_over_limit)
1562 pagevec_strip(&pvec);
1563 __pagevec_release(&pvec);
1564 spin_lock_irq(&zone->lru_lock);
1567 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1568 if (!is_active_lru(lru))
1569 __count_vm_events(PGDEACTIVATE, pgmoved);
1572 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1573 struct scan_control *sc, int priority, int file)
1575 unsigned long nr_taken;
1576 unsigned long pgscanned;
1577 unsigned long vm_flags;
1578 LIST_HEAD(l_hold); /* The pages which were snipped off */
1579 LIST_HEAD(l_active);
1580 LIST_HEAD(l_inactive);
1582 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1583 unsigned long nr_rotated = 0;
1586 spin_lock_irq(&zone->lru_lock);
1587 if (scanning_global_lru(sc)) {
1588 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1589 &pgscanned, sc->order,
1590 ISOLATE_ACTIVE, zone,
1592 zone->pages_scanned += pgscanned;
1594 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1595 &pgscanned, sc->order,
1596 ISOLATE_ACTIVE, zone,
1597 sc->mem_cgroup, 1, file);
1599 * mem_cgroup_isolate_pages() keeps track of
1600 * scanned pages on its own.
1604 reclaim_stat->recent_scanned[file] += nr_taken;
1606 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1608 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1610 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1611 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1612 spin_unlock_irq(&zone->lru_lock);
1614 while (!list_empty(&l_hold)) {
1616 page = lru_to_page(&l_hold);
1617 list_del(&page->lru);
1619 if (unlikely(!page_evictable(page, NULL))) {
1620 putback_lru_page(page);
1624 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1625 nr_rotated += hpage_nr_pages(page);
1627 * Identify referenced, file-backed active pages and
1628 * give them one more trip around the active list. So
1629 * that executable code get better chances to stay in
1630 * memory under moderate memory pressure. Anon pages
1631 * are not likely to be evicted by use-once streaming
1632 * IO, plus JVM can create lots of anon VM_EXEC pages,
1633 * so we ignore them here.
1635 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1636 list_add(&page->lru, &l_active);
1641 ClearPageActive(page); /* we are de-activating */
1642 list_add(&page->lru, &l_inactive);
1646 * Move pages back to the lru list.
1648 spin_lock_irq(&zone->lru_lock);
1650 * Count referenced pages from currently used mappings as rotated,
1651 * even though only some of them are actually re-activated. This
1652 * helps balance scan pressure between file and anonymous pages in
1655 reclaim_stat->recent_rotated[file] += nr_rotated;
1657 move_active_pages_to_lru(zone, &l_active,
1658 LRU_ACTIVE + file * LRU_FILE);
1659 move_active_pages_to_lru(zone, &l_inactive,
1660 LRU_BASE + file * LRU_FILE);
1661 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1662 spin_unlock_irq(&zone->lru_lock);
1666 static int inactive_anon_is_low_global(struct zone *zone)
1668 unsigned long active, inactive;
1670 active = zone_page_state(zone, NR_ACTIVE_ANON);
1671 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1673 if (inactive * zone->inactive_ratio < active)
1680 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1681 * @zone: zone to check
1682 * @sc: scan control of this context
1684 * Returns true if the zone does not have enough inactive anon pages,
1685 * meaning some active anon pages need to be deactivated.
1687 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1692 * If we don't have swap space, anonymous page deactivation
1695 if (!total_swap_pages)
1698 if (scanning_global_lru(sc))
1699 low = inactive_anon_is_low_global(zone);
1701 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1705 static inline int inactive_anon_is_low(struct zone *zone,
1706 struct scan_control *sc)
1712 static int inactive_file_is_low_global(struct zone *zone)
1714 unsigned long active, inactive;
1716 active = zone_page_state(zone, NR_ACTIVE_FILE);
1717 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1719 return (active > inactive);
1723 * inactive_file_is_low - check if file pages need to be deactivated
1724 * @zone: zone to check
1725 * @sc: scan control of this context
1727 * When the system is doing streaming IO, memory pressure here
1728 * ensures that active file pages get deactivated, until more
1729 * than half of the file pages are on the inactive list.
1731 * Once we get to that situation, protect the system's working
1732 * set from being evicted by disabling active file page aging.
1734 * This uses a different ratio than the anonymous pages, because
1735 * the page cache uses a use-once replacement algorithm.
1737 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1741 if (scanning_global_lru(sc))
1742 low = inactive_file_is_low_global(zone);
1744 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1748 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1752 return inactive_file_is_low(zone, sc);
1754 return inactive_anon_is_low(zone, sc);
1757 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1758 struct zone *zone, struct scan_control *sc, int priority)
1760 int file = is_file_lru(lru);
1762 if (is_active_lru(lru)) {
1763 if (inactive_list_is_low(zone, sc, file))
1764 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1768 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1771 static int vmscan_swappiness(struct scan_control *sc)
1773 if (scanning_global_lru(sc))
1774 return vm_swappiness;
1775 return mem_cgroup_swappiness(sc->mem_cgroup);
1779 * Determine how aggressively the anon and file LRU lists should be
1780 * scanned. The relative value of each set of LRU lists is determined
1781 * by looking at the fraction of the pages scanned we did rotate back
1782 * onto the active list instead of evict.
1784 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1786 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1787 unsigned long *nr, int priority)
1789 unsigned long anon, file, free;
1790 unsigned long anon_prio, file_prio;
1791 unsigned long ap, fp;
1792 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1793 u64 fraction[2], denominator;
1799 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1800 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1801 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1802 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1804 if (((anon + file) >> priority) < SWAP_CLUSTER_MAX) {
1805 /* kswapd does zone balancing and need to scan this zone */
1806 if (scanning_global_lru(sc) && current_is_kswapd())
1808 /* memcg may have small limit and need to avoid priority drop */
1809 if (!scanning_global_lru(sc))
1813 /* If we have no swap space, do not bother scanning anon pages. */
1814 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1822 if (scanning_global_lru(sc)) {
1823 free = zone_page_state(zone, NR_FREE_PAGES);
1824 /* If we have very few page cache pages,
1825 force-scan anon pages. */
1826 if (unlikely(file + free <= high_wmark_pages(zone))) {
1835 * With swappiness at 100, anonymous and file have the same priority.
1836 * This scanning priority is essentially the inverse of IO cost.
1838 anon_prio = vmscan_swappiness(sc);
1839 file_prio = 200 - vmscan_swappiness(sc);
1842 * OK, so we have swap space and a fair amount of page cache
1843 * pages. We use the recently rotated / recently scanned
1844 * ratios to determine how valuable each cache is.
1846 * Because workloads change over time (and to avoid overflow)
1847 * we keep these statistics as a floating average, which ends
1848 * up weighing recent references more than old ones.
1850 * anon in [0], file in [1]
1852 spin_lock_irq(&zone->lru_lock);
1853 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1854 reclaim_stat->recent_scanned[0] /= 2;
1855 reclaim_stat->recent_rotated[0] /= 2;
1858 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1859 reclaim_stat->recent_scanned[1] /= 2;
1860 reclaim_stat->recent_rotated[1] /= 2;
1864 * The amount of pressure on anon vs file pages is inversely
1865 * proportional to the fraction of recently scanned pages on
1866 * each list that were recently referenced and in active use.
1868 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1869 ap /= reclaim_stat->recent_rotated[0] + 1;
1871 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1872 fp /= reclaim_stat->recent_rotated[1] + 1;
1873 spin_unlock_irq(&zone->lru_lock);
1877 denominator = ap + fp + 1;
1879 for_each_evictable_lru(l) {
1880 int file = is_file_lru(l);
1883 scan = zone_nr_lru_pages(zone, sc, l);
1884 if (priority || noswap) {
1886 scan = div64_u64(scan * fraction[file], denominator);
1890 * If zone is small or memcg is small, nr[l] can be 0.
1891 * This results no-scan on this priority and priority drop down.
1892 * For global direct reclaim, it can visit next zone and tend
1893 * not to have problems. For global kswapd, it's for zone
1894 * balancing and it need to scan a small amounts. When using
1895 * memcg, priority drop can cause big latency. So, it's better
1896 * to scan small amount. See may_noscan above.
1898 if (!scan && force_scan) {
1900 scan = SWAP_CLUSTER_MAX;
1902 scan = SWAP_CLUSTER_MAX;
1909 * Reclaim/compaction depends on a number of pages being freed. To avoid
1910 * disruption to the system, a small number of order-0 pages continue to be
1911 * rotated and reclaimed in the normal fashion. However, by the time we get
1912 * back to the allocator and call try_to_compact_zone(), we ensure that
1913 * there are enough free pages for it to be likely successful
1915 static inline bool should_continue_reclaim(struct zone *zone,
1916 unsigned long nr_reclaimed,
1917 unsigned long nr_scanned,
1918 struct scan_control *sc)
1920 unsigned long pages_for_compaction;
1921 unsigned long inactive_lru_pages;
1923 /* If not in reclaim/compaction mode, stop */
1924 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1927 /* Consider stopping depending on scan and reclaim activity */
1928 if (sc->gfp_mask & __GFP_REPEAT) {
1930 * For __GFP_REPEAT allocations, stop reclaiming if the
1931 * full LRU list has been scanned and we are still failing
1932 * to reclaim pages. This full LRU scan is potentially
1933 * expensive but a __GFP_REPEAT caller really wants to succeed
1935 if (!nr_reclaimed && !nr_scanned)
1939 * For non-__GFP_REPEAT allocations which can presumably
1940 * fail without consequence, stop if we failed to reclaim
1941 * any pages from the last SWAP_CLUSTER_MAX number of
1942 * pages that were scanned. This will return to the
1943 * caller faster at the risk reclaim/compaction and
1944 * the resulting allocation attempt fails
1951 * If we have not reclaimed enough pages for compaction and the
1952 * inactive lists are large enough, continue reclaiming
1954 pages_for_compaction = (2UL << sc->order);
1955 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
1956 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1957 if (sc->nr_reclaimed < pages_for_compaction &&
1958 inactive_lru_pages > pages_for_compaction)
1961 /* If compaction would go ahead or the allocation would succeed, stop */
1962 switch (compaction_suitable(zone, sc->order)) {
1963 case COMPACT_PARTIAL:
1964 case COMPACT_CONTINUE:
1972 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1974 static void shrink_zone(int priority, struct zone *zone,
1975 struct scan_control *sc)
1977 unsigned long nr[NR_LRU_LISTS];
1978 unsigned long nr_to_scan;
1980 unsigned long nr_reclaimed, nr_scanned;
1981 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1985 nr_scanned = sc->nr_scanned;
1986 get_scan_count(zone, sc, nr, priority);
1988 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1989 nr[LRU_INACTIVE_FILE]) {
1990 for_each_evictable_lru(l) {
1992 nr_to_scan = min_t(unsigned long,
1993 nr[l], SWAP_CLUSTER_MAX);
1994 nr[l] -= nr_to_scan;
1996 nr_reclaimed += shrink_list(l, nr_to_scan,
1997 zone, sc, priority);
2001 * On large memory systems, scan >> priority can become
2002 * really large. This is fine for the starting priority;
2003 * we want to put equal scanning pressure on each zone.
2004 * However, if the VM has a harder time of freeing pages,
2005 * with multiple processes reclaiming pages, the total
2006 * freeing target can get unreasonably large.
2008 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2011 sc->nr_reclaimed += nr_reclaimed;
2014 * Even if we did not try to evict anon pages at all, we want to
2015 * rebalance the anon lru active/inactive ratio.
2017 if (inactive_anon_is_low(zone, sc))
2018 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
2020 /* reclaim/compaction might need reclaim to continue */
2021 if (should_continue_reclaim(zone, nr_reclaimed,
2022 sc->nr_scanned - nr_scanned, sc))
2025 throttle_vm_writeout(sc->gfp_mask);
2029 * This is the direct reclaim path, for page-allocating processes. We only
2030 * try to reclaim pages from zones which will satisfy the caller's allocation
2033 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2035 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2037 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2038 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2039 * zone defense algorithm.
2041 * If a zone is deemed to be full of pinned pages then just give it a light
2042 * scan then give up on it.
2044 static void shrink_zones(int priority, struct zonelist *zonelist,
2045 struct scan_control *sc)
2049 unsigned long nr_soft_reclaimed;
2050 unsigned long nr_soft_scanned;
2052 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2053 gfp_zone(sc->gfp_mask), sc->nodemask) {
2054 if (!populated_zone(zone))
2057 * Take care memory controller reclaiming has small influence
2060 if (scanning_global_lru(sc)) {
2061 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2063 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2064 continue; /* Let kswapd poll it */
2066 * This steals pages from memory cgroups over softlimit
2067 * and returns the number of reclaimed pages and
2068 * scanned pages. This works for global memory pressure
2069 * and balancing, not for a memcg's limit.
2071 nr_soft_scanned = 0;
2072 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2073 sc->order, sc->gfp_mask,
2075 sc->nr_reclaimed += nr_soft_reclaimed;
2076 sc->nr_scanned += nr_soft_scanned;
2077 /* need some check for avoid more shrink_zone() */
2080 shrink_zone(priority, zone, sc);
2084 static bool zone_reclaimable(struct zone *zone)
2086 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2089 /* All zones in zonelist are unreclaimable? */
2090 static bool all_unreclaimable(struct zonelist *zonelist,
2091 struct scan_control *sc)
2096 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2097 gfp_zone(sc->gfp_mask), sc->nodemask) {
2098 if (!populated_zone(zone))
2100 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2102 if (!zone->all_unreclaimable)
2110 * This is the main entry point to direct page reclaim.
2112 * If a full scan of the inactive list fails to free enough memory then we
2113 * are "out of memory" and something needs to be killed.
2115 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2116 * high - the zone may be full of dirty or under-writeback pages, which this
2117 * caller can't do much about. We kick the writeback threads and take explicit
2118 * naps in the hope that some of these pages can be written. But if the
2119 * allocating task holds filesystem locks which prevent writeout this might not
2120 * work, and the allocation attempt will fail.
2122 * returns: 0, if no pages reclaimed
2123 * else, the number of pages reclaimed
2125 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2126 struct scan_control *sc,
2127 struct shrink_control *shrink)
2130 unsigned long total_scanned = 0;
2131 struct reclaim_state *reclaim_state = current->reclaim_state;
2134 unsigned long writeback_threshold;
2137 delayacct_freepages_start();
2139 if (scanning_global_lru(sc))
2140 count_vm_event(ALLOCSTALL);
2142 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2145 disable_swap_token(sc->mem_cgroup);
2146 shrink_zones(priority, zonelist, sc);
2148 * Don't shrink slabs when reclaiming memory from
2149 * over limit cgroups
2151 if (scanning_global_lru(sc)) {
2152 unsigned long lru_pages = 0;
2153 for_each_zone_zonelist(zone, z, zonelist,
2154 gfp_zone(sc->gfp_mask)) {
2155 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2158 lru_pages += zone_reclaimable_pages(zone);
2161 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2162 if (reclaim_state) {
2163 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2164 reclaim_state->reclaimed_slab = 0;
2167 total_scanned += sc->nr_scanned;
2168 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2172 * Try to write back as many pages as we just scanned. This
2173 * tends to cause slow streaming writers to write data to the
2174 * disk smoothly, at the dirtying rate, which is nice. But
2175 * that's undesirable in laptop mode, where we *want* lumpy
2176 * writeout. So in laptop mode, write out the whole world.
2178 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2179 if (total_scanned > writeback_threshold) {
2180 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2181 sc->may_writepage = 1;
2184 /* Take a nap, wait for some writeback to complete */
2185 if (!sc->hibernation_mode && sc->nr_scanned &&
2186 priority < DEF_PRIORITY - 2) {
2187 struct zone *preferred_zone;
2189 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2190 &cpuset_current_mems_allowed,
2192 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2197 delayacct_freepages_end();
2200 if (sc->nr_reclaimed)
2201 return sc->nr_reclaimed;
2204 * As hibernation is going on, kswapd is freezed so that it can't mark
2205 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2208 if (oom_killer_disabled)
2211 /* top priority shrink_zones still had more to do? don't OOM, then */
2212 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2218 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2219 gfp_t gfp_mask, nodemask_t *nodemask)
2221 unsigned long nr_reclaimed;
2222 struct scan_control sc = {
2223 .gfp_mask = gfp_mask,
2224 .may_writepage = !laptop_mode,
2225 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2230 .nodemask = nodemask,
2232 struct shrink_control shrink = {
2233 .gfp_mask = sc.gfp_mask,
2236 trace_mm_vmscan_direct_reclaim_begin(order,
2240 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2242 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2244 return nr_reclaimed;
2247 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2249 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2250 gfp_t gfp_mask, bool noswap,
2252 unsigned long *nr_scanned)
2254 struct scan_control sc = {
2256 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2257 .may_writepage = !laptop_mode,
2259 .may_swap = !noswap,
2264 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2265 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2267 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2272 * NOTE: Although we can get the priority field, using it
2273 * here is not a good idea, since it limits the pages we can scan.
2274 * if we don't reclaim here, the shrink_zone from balance_pgdat
2275 * will pick up pages from other mem cgroup's as well. We hack
2276 * the priority and make it zero.
2278 shrink_zone(0, zone, &sc);
2280 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2282 *nr_scanned = sc.nr_scanned;
2283 return sc.nr_reclaimed;
2286 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2290 struct zonelist *zonelist;
2291 unsigned long nr_reclaimed;
2293 struct scan_control sc = {
2294 .may_writepage = !laptop_mode,
2296 .may_swap = !noswap,
2297 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2299 .mem_cgroup = mem_cont,
2300 .nodemask = NULL, /* we don't care the placement */
2301 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2302 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2304 struct shrink_control shrink = {
2305 .gfp_mask = sc.gfp_mask,
2309 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2310 * take care of from where we get pages. So the node where we start the
2311 * scan does not need to be the current node.
2313 nid = mem_cgroup_select_victim_node(mem_cont);
2315 zonelist = NODE_DATA(nid)->node_zonelists;
2317 trace_mm_vmscan_memcg_reclaim_begin(0,
2321 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2323 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2325 return nr_reclaimed;
2330 * pgdat_balanced is used when checking if a node is balanced for high-order
2331 * allocations. Only zones that meet watermarks and are in a zone allowed
2332 * by the callers classzone_idx are added to balanced_pages. The total of
2333 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2334 * for the node to be considered balanced. Forcing all zones to be balanced
2335 * for high orders can cause excessive reclaim when there are imbalanced zones.
2336 * The choice of 25% is due to
2337 * o a 16M DMA zone that is balanced will not balance a zone on any
2338 * reasonable sized machine
2339 * o On all other machines, the top zone must be at least a reasonable
2340 * percentage of the middle zones. For example, on 32-bit x86, highmem
2341 * would need to be at least 256M for it to be balance a whole node.
2342 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2343 * to balance a node on its own. These seemed like reasonable ratios.
2345 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2348 unsigned long present_pages = 0;
2351 for (i = 0; i <= classzone_idx; i++)
2352 present_pages += pgdat->node_zones[i].present_pages;
2354 /* A special case here: if zone has no page, we think it's balanced */
2355 return balanced_pages >= (present_pages >> 2);
2358 /* is kswapd sleeping prematurely? */
2359 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2363 unsigned long balanced = 0;
2364 bool all_zones_ok = true;
2366 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2370 /* Check the watermark levels */
2371 for (i = 0; i <= classzone_idx; i++) {
2372 struct zone *zone = pgdat->node_zones + i;
2374 if (!populated_zone(zone))
2378 * balance_pgdat() skips over all_unreclaimable after
2379 * DEF_PRIORITY. Effectively, it considers them balanced so
2380 * they must be considered balanced here as well if kswapd
2383 if (zone->all_unreclaimable) {
2384 balanced += zone->present_pages;
2388 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2390 all_zones_ok = false;
2392 balanced += zone->present_pages;
2396 * For high-order requests, the balanced zones must contain at least
2397 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2401 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2403 return !all_zones_ok;
2407 * For kswapd, balance_pgdat() will work across all this node's zones until
2408 * they are all at high_wmark_pages(zone).
2410 * Returns the final order kswapd was reclaiming at
2412 * There is special handling here for zones which are full of pinned pages.
2413 * This can happen if the pages are all mlocked, or if they are all used by
2414 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2415 * What we do is to detect the case where all pages in the zone have been
2416 * scanned twice and there has been zero successful reclaim. Mark the zone as
2417 * dead and from now on, only perform a short scan. Basically we're polling
2418 * the zone for when the problem goes away.
2420 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2421 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2422 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2423 * lower zones regardless of the number of free pages in the lower zones. This
2424 * interoperates with the page allocator fallback scheme to ensure that aging
2425 * of pages is balanced across the zones.
2427 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2431 unsigned long balanced;
2434 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2435 unsigned long total_scanned;
2436 struct reclaim_state *reclaim_state = current->reclaim_state;
2437 unsigned long nr_soft_reclaimed;
2438 unsigned long nr_soft_scanned;
2439 struct scan_control sc = {
2440 .gfp_mask = GFP_KERNEL,
2444 * kswapd doesn't want to be bailed out while reclaim. because
2445 * we want to put equal scanning pressure on each zone.
2447 .nr_to_reclaim = ULONG_MAX,
2451 struct shrink_control shrink = {
2452 .gfp_mask = sc.gfp_mask,
2456 sc.nr_reclaimed = 0;
2457 sc.may_writepage = !laptop_mode;
2458 count_vm_event(PAGEOUTRUN);
2460 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2461 unsigned long lru_pages = 0;
2462 int has_under_min_watermark_zone = 0;
2464 /* The swap token gets in the way of swapout... */
2466 disable_swap_token(NULL);
2472 * Scan in the highmem->dma direction for the highest
2473 * zone which needs scanning
2475 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2476 struct zone *zone = pgdat->node_zones + i;
2478 if (!populated_zone(zone))
2481 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2485 * Do some background aging of the anon list, to give
2486 * pages a chance to be referenced before reclaiming.
2488 if (inactive_anon_is_low(zone, &sc))
2489 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2492 if (!zone_watermark_ok_safe(zone, order,
2493 high_wmark_pages(zone), 0, 0)) {
2501 for (i = 0; i <= end_zone; i++) {
2502 struct zone *zone = pgdat->node_zones + i;
2504 lru_pages += zone_reclaimable_pages(zone);
2508 * Now scan the zone in the dma->highmem direction, stopping
2509 * at the last zone which needs scanning.
2511 * We do this because the page allocator works in the opposite
2512 * direction. This prevents the page allocator from allocating
2513 * pages behind kswapd's direction of progress, which would
2514 * cause too much scanning of the lower zones.
2516 for (i = 0; i <= end_zone; i++) {
2517 struct zone *zone = pgdat->node_zones + i;
2519 unsigned long balance_gap;
2521 if (!populated_zone(zone))
2524 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2529 nr_soft_scanned = 0;
2531 * Call soft limit reclaim before calling shrink_zone.
2533 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2536 sc.nr_reclaimed += nr_soft_reclaimed;
2537 total_scanned += nr_soft_scanned;
2540 * We put equal pressure on every zone, unless
2541 * one zone has way too many pages free
2542 * already. The "too many pages" is defined
2543 * as the high wmark plus a "gap" where the
2544 * gap is either the low watermark or 1%
2545 * of the zone, whichever is smaller.
2547 balance_gap = min(low_wmark_pages(zone),
2548 (zone->present_pages +
2549 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2550 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2551 if (!zone_watermark_ok_safe(zone, order,
2552 high_wmark_pages(zone) + balance_gap,
2554 shrink_zone(priority, zone, &sc);
2556 reclaim_state->reclaimed_slab = 0;
2557 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2558 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2559 total_scanned += sc.nr_scanned;
2561 if (nr_slab == 0 && !zone_reclaimable(zone))
2562 zone->all_unreclaimable = 1;
2566 * If we've done a decent amount of scanning and
2567 * the reclaim ratio is low, start doing writepage
2568 * even in laptop mode
2570 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2571 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2572 sc.may_writepage = 1;
2574 if (zone->all_unreclaimable) {
2575 if (end_zone && end_zone == i)
2580 if (!zone_watermark_ok_safe(zone, order,
2581 high_wmark_pages(zone), end_zone, 0)) {
2584 * We are still under min water mark. This
2585 * means that we have a GFP_ATOMIC allocation
2586 * failure risk. Hurry up!
2588 if (!zone_watermark_ok_safe(zone, order,
2589 min_wmark_pages(zone), end_zone, 0))
2590 has_under_min_watermark_zone = 1;
2593 * If a zone reaches its high watermark,
2594 * consider it to be no longer congested. It's
2595 * possible there are dirty pages backed by
2596 * congested BDIs but as pressure is relieved,
2597 * spectulatively avoid congestion waits
2599 zone_clear_flag(zone, ZONE_CONGESTED);
2600 if (i <= *classzone_idx)
2601 balanced += zone->present_pages;
2605 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2606 break; /* kswapd: all done */
2608 * OK, kswapd is getting into trouble. Take a nap, then take
2609 * another pass across the zones.
2611 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2612 if (has_under_min_watermark_zone)
2613 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2615 congestion_wait(BLK_RW_ASYNC, HZ/10);
2619 * We do this so kswapd doesn't build up large priorities for
2620 * example when it is freeing in parallel with allocators. It
2621 * matches the direct reclaim path behaviour in terms of impact
2622 * on zone->*_priority.
2624 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2630 * order-0: All zones must meet high watermark for a balanced node
2631 * high-order: Balanced zones must make up at least 25% of the node
2632 * for the node to be balanced
2634 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2640 * Fragmentation may mean that the system cannot be
2641 * rebalanced for high-order allocations in all zones.
2642 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2643 * it means the zones have been fully scanned and are still
2644 * not balanced. For high-order allocations, there is
2645 * little point trying all over again as kswapd may
2648 * Instead, recheck all watermarks at order-0 as they
2649 * are the most important. If watermarks are ok, kswapd will go
2650 * back to sleep. High-order users can still perform direct
2651 * reclaim if they wish.
2653 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2654 order = sc.order = 0;
2660 * If kswapd was reclaiming at a higher order, it has the option of
2661 * sleeping without all zones being balanced. Before it does, it must
2662 * ensure that the watermarks for order-0 on *all* zones are met and
2663 * that the congestion flags are cleared. The congestion flag must
2664 * be cleared as kswapd is the only mechanism that clears the flag
2665 * and it is potentially going to sleep here.
2668 for (i = 0; i <= end_zone; i++) {
2669 struct zone *zone = pgdat->node_zones + i;
2671 if (!populated_zone(zone))
2674 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2677 /* Confirm the zone is balanced for order-0 */
2678 if (!zone_watermark_ok(zone, 0,
2679 high_wmark_pages(zone), 0, 0)) {
2680 order = sc.order = 0;
2684 /* If balanced, clear the congested flag */
2685 zone_clear_flag(zone, ZONE_CONGESTED);
2690 * Return the order we were reclaiming at so sleeping_prematurely()
2691 * makes a decision on the order we were last reclaiming at. However,
2692 * if another caller entered the allocator slow path while kswapd
2693 * was awake, order will remain at the higher level
2695 *classzone_idx = end_zone;
2699 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2704 if (freezing(current) || kthread_should_stop())
2707 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2709 /* Try to sleep for a short interval */
2710 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2711 remaining = schedule_timeout(HZ/10);
2712 finish_wait(&pgdat->kswapd_wait, &wait);
2713 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2717 * After a short sleep, check if it was a premature sleep. If not, then
2718 * go fully to sleep until explicitly woken up.
2720 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2721 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2724 * vmstat counters are not perfectly accurate and the estimated
2725 * value for counters such as NR_FREE_PAGES can deviate from the
2726 * true value by nr_online_cpus * threshold. To avoid the zone
2727 * watermarks being breached while under pressure, we reduce the
2728 * per-cpu vmstat threshold while kswapd is awake and restore
2729 * them before going back to sleep.
2731 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2733 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2736 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2738 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2740 finish_wait(&pgdat->kswapd_wait, &wait);
2744 * The background pageout daemon, started as a kernel thread
2745 * from the init process.
2747 * This basically trickles out pages so that we have _some_
2748 * free memory available even if there is no other activity
2749 * that frees anything up. This is needed for things like routing
2750 * etc, where we otherwise might have all activity going on in
2751 * asynchronous contexts that cannot page things out.
2753 * If there are applications that are active memory-allocators
2754 * (most normal use), this basically shouldn't matter.
2756 static int kswapd(void *p)
2758 unsigned long order, new_order;
2759 int classzone_idx, new_classzone_idx;
2760 pg_data_t *pgdat = (pg_data_t*)p;
2761 struct task_struct *tsk = current;
2763 struct reclaim_state reclaim_state = {
2764 .reclaimed_slab = 0,
2766 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2768 lockdep_set_current_reclaim_state(GFP_KERNEL);
2770 if (!cpumask_empty(cpumask))
2771 set_cpus_allowed_ptr(tsk, cpumask);
2772 current->reclaim_state = &reclaim_state;
2775 * Tell the memory management that we're a "memory allocator",
2776 * and that if we need more memory we should get access to it
2777 * regardless (see "__alloc_pages()"). "kswapd" should
2778 * never get caught in the normal page freeing logic.
2780 * (Kswapd normally doesn't need memory anyway, but sometimes
2781 * you need a small amount of memory in order to be able to
2782 * page out something else, and this flag essentially protects
2783 * us from recursively trying to free more memory as we're
2784 * trying to free the first piece of memory in the first place).
2786 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2789 order = new_order = 0;
2790 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2795 * If the last balance_pgdat was unsuccessful it's unlikely a
2796 * new request of a similar or harder type will succeed soon
2797 * so consider going to sleep on the basis we reclaimed at
2799 if (classzone_idx >= new_classzone_idx && order == new_order) {
2800 new_order = pgdat->kswapd_max_order;
2801 new_classzone_idx = pgdat->classzone_idx;
2802 pgdat->kswapd_max_order = 0;
2803 pgdat->classzone_idx = pgdat->nr_zones - 1;
2806 if (order < new_order || classzone_idx > new_classzone_idx) {
2808 * Don't sleep if someone wants a larger 'order'
2809 * allocation or has tigher zone constraints
2812 classzone_idx = new_classzone_idx;
2814 kswapd_try_to_sleep(pgdat, order, classzone_idx);
2815 order = pgdat->kswapd_max_order;
2816 classzone_idx = pgdat->classzone_idx;
2817 pgdat->kswapd_max_order = 0;
2818 pgdat->classzone_idx = pgdat->nr_zones - 1;
2821 ret = try_to_freeze();
2822 if (kthread_should_stop())
2826 * We can speed up thawing tasks if we don't call balance_pgdat
2827 * after returning from the refrigerator
2830 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2831 order = balance_pgdat(pgdat, order, &classzone_idx);
2838 * A zone is low on free memory, so wake its kswapd task to service it.
2840 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2844 if (!populated_zone(zone))
2847 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2849 pgdat = zone->zone_pgdat;
2850 if (pgdat->kswapd_max_order < order) {
2851 pgdat->kswapd_max_order = order;
2852 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2854 if (!waitqueue_active(&pgdat->kswapd_wait))
2856 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2859 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2860 wake_up_interruptible(&pgdat->kswapd_wait);
2864 * The reclaimable count would be mostly accurate.
2865 * The less reclaimable pages may be
2866 * - mlocked pages, which will be moved to unevictable list when encountered
2867 * - mapped pages, which may require several travels to be reclaimed
2868 * - dirty pages, which is not "instantly" reclaimable
2870 unsigned long global_reclaimable_pages(void)
2874 nr = global_page_state(NR_ACTIVE_FILE) +
2875 global_page_state(NR_INACTIVE_FILE);
2877 if (nr_swap_pages > 0)
2878 nr += global_page_state(NR_ACTIVE_ANON) +
2879 global_page_state(NR_INACTIVE_ANON);
2884 unsigned long zone_reclaimable_pages(struct zone *zone)
2888 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2889 zone_page_state(zone, NR_INACTIVE_FILE);
2891 if (nr_swap_pages > 0)
2892 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2893 zone_page_state(zone, NR_INACTIVE_ANON);
2898 #ifdef CONFIG_HIBERNATION
2900 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2903 * Rather than trying to age LRUs the aim is to preserve the overall
2904 * LRU order by reclaiming preferentially
2905 * inactive > active > active referenced > active mapped
2907 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2909 struct reclaim_state reclaim_state;
2910 struct scan_control sc = {
2911 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2915 .nr_to_reclaim = nr_to_reclaim,
2916 .hibernation_mode = 1,
2919 struct shrink_control shrink = {
2920 .gfp_mask = sc.gfp_mask,
2922 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2923 struct task_struct *p = current;
2924 unsigned long nr_reclaimed;
2926 p->flags |= PF_MEMALLOC;
2927 lockdep_set_current_reclaim_state(sc.gfp_mask);
2928 reclaim_state.reclaimed_slab = 0;
2929 p->reclaim_state = &reclaim_state;
2931 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2933 p->reclaim_state = NULL;
2934 lockdep_clear_current_reclaim_state();
2935 p->flags &= ~PF_MEMALLOC;
2937 return nr_reclaimed;
2939 #endif /* CONFIG_HIBERNATION */
2941 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2942 not required for correctness. So if the last cpu in a node goes
2943 away, we get changed to run anywhere: as the first one comes back,
2944 restore their cpu bindings. */
2945 static int __devinit cpu_callback(struct notifier_block *nfb,
2946 unsigned long action, void *hcpu)
2950 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2951 for_each_node_state(nid, N_HIGH_MEMORY) {
2952 pg_data_t *pgdat = NODE_DATA(nid);
2953 const struct cpumask *mask;
2955 mask = cpumask_of_node(pgdat->node_id);
2957 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2958 /* One of our CPUs online: restore mask */
2959 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2966 * This kswapd start function will be called by init and node-hot-add.
2967 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2969 int kswapd_run(int nid)
2971 pg_data_t *pgdat = NODE_DATA(nid);
2977 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2978 if (IS_ERR(pgdat->kswapd)) {
2979 /* failure at boot is fatal */
2980 BUG_ON(system_state == SYSTEM_BOOTING);
2981 printk("Failed to start kswapd on node %d\n",nid);
2988 * Called by memory hotplug when all memory in a node is offlined.
2990 void kswapd_stop(int nid)
2992 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2995 kthread_stop(kswapd);
2998 static int __init kswapd_init(void)
3003 for_each_node_state(nid, N_HIGH_MEMORY)
3005 hotcpu_notifier(cpu_callback, 0);
3009 module_init(kswapd_init)
3015 * If non-zero call zone_reclaim when the number of free pages falls below
3018 int zone_reclaim_mode __read_mostly;
3020 #define RECLAIM_OFF 0
3021 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3022 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3023 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3026 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3027 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3030 #define ZONE_RECLAIM_PRIORITY 4
3033 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3036 int sysctl_min_unmapped_ratio = 1;
3039 * If the number of slab pages in a zone grows beyond this percentage then
3040 * slab reclaim needs to occur.
3042 int sysctl_min_slab_ratio = 5;
3044 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3046 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3047 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3048 zone_page_state(zone, NR_ACTIVE_FILE);
3051 * It's possible for there to be more file mapped pages than
3052 * accounted for by the pages on the file LRU lists because
3053 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3055 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3058 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3059 static long zone_pagecache_reclaimable(struct zone *zone)
3061 long nr_pagecache_reclaimable;
3065 * If RECLAIM_SWAP is set, then all file pages are considered
3066 * potentially reclaimable. Otherwise, we have to worry about
3067 * pages like swapcache and zone_unmapped_file_pages() provides
3070 if (zone_reclaim_mode & RECLAIM_SWAP)
3071 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3073 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3075 /* If we can't clean pages, remove dirty pages from consideration */
3076 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3077 delta += zone_page_state(zone, NR_FILE_DIRTY);
3079 /* Watch for any possible underflows due to delta */
3080 if (unlikely(delta > nr_pagecache_reclaimable))
3081 delta = nr_pagecache_reclaimable;
3083 return nr_pagecache_reclaimable - delta;
3087 * Try to free up some pages from this zone through reclaim.
3089 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3091 /* Minimum pages needed in order to stay on node */
3092 const unsigned long nr_pages = 1 << order;
3093 struct task_struct *p = current;
3094 struct reclaim_state reclaim_state;
3096 struct scan_control sc = {
3097 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3098 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3100 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3102 .gfp_mask = gfp_mask,
3105 struct shrink_control shrink = {
3106 .gfp_mask = sc.gfp_mask,
3108 unsigned long nr_slab_pages0, nr_slab_pages1;
3112 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3113 * and we also need to be able to write out pages for RECLAIM_WRITE
3116 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3117 lockdep_set_current_reclaim_state(gfp_mask);
3118 reclaim_state.reclaimed_slab = 0;
3119 p->reclaim_state = &reclaim_state;
3121 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3123 * Free memory by calling shrink zone with increasing
3124 * priorities until we have enough memory freed.
3126 priority = ZONE_RECLAIM_PRIORITY;
3128 shrink_zone(priority, zone, &sc);
3130 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3133 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3134 if (nr_slab_pages0 > zone->min_slab_pages) {
3136 * shrink_slab() does not currently allow us to determine how
3137 * many pages were freed in this zone. So we take the current
3138 * number of slab pages and shake the slab until it is reduced
3139 * by the same nr_pages that we used for reclaiming unmapped
3142 * Note that shrink_slab will free memory on all zones and may
3146 unsigned long lru_pages = zone_reclaimable_pages(zone);
3148 /* No reclaimable slab or very low memory pressure */
3149 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3152 /* Freed enough memory */
3153 nr_slab_pages1 = zone_page_state(zone,
3154 NR_SLAB_RECLAIMABLE);
3155 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3160 * Update nr_reclaimed by the number of slab pages we
3161 * reclaimed from this zone.
3163 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3164 if (nr_slab_pages1 < nr_slab_pages0)
3165 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3168 p->reclaim_state = NULL;
3169 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3170 lockdep_clear_current_reclaim_state();
3171 return sc.nr_reclaimed >= nr_pages;
3174 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3180 * Zone reclaim reclaims unmapped file backed pages and
3181 * slab pages if we are over the defined limits.
3183 * A small portion of unmapped file backed pages is needed for
3184 * file I/O otherwise pages read by file I/O will be immediately
3185 * thrown out if the zone is overallocated. So we do not reclaim
3186 * if less than a specified percentage of the zone is used by
3187 * unmapped file backed pages.
3189 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3190 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3191 return ZONE_RECLAIM_FULL;
3193 if (zone->all_unreclaimable)
3194 return ZONE_RECLAIM_FULL;
3197 * Do not scan if the allocation should not be delayed.
3199 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3200 return ZONE_RECLAIM_NOSCAN;
3203 * Only run zone reclaim on the local zone or on zones that do not
3204 * have associated processors. This will favor the local processor
3205 * over remote processors and spread off node memory allocations
3206 * as wide as possible.
3208 node_id = zone_to_nid(zone);
3209 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3210 return ZONE_RECLAIM_NOSCAN;
3212 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3213 return ZONE_RECLAIM_NOSCAN;
3215 ret = __zone_reclaim(zone, gfp_mask, order);
3216 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3219 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3226 * page_evictable - test whether a page is evictable
3227 * @page: the page to test
3228 * @vma: the VMA in which the page is or will be mapped, may be NULL
3230 * Test whether page is evictable--i.e., should be placed on active/inactive
3231 * lists vs unevictable list. The vma argument is !NULL when called from the
3232 * fault path to determine how to instantate a new page.
3234 * Reasons page might not be evictable:
3235 * (1) page's mapping marked unevictable
3236 * (2) page is part of an mlocked VMA
3239 int page_evictable(struct page *page, struct vm_area_struct *vma)
3242 if (mapping_unevictable(page_mapping(page)))
3245 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3252 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3253 * @page: page to check evictability and move to appropriate lru list
3254 * @zone: zone page is in
3256 * Checks a page for evictability and moves the page to the appropriate
3259 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3260 * have PageUnevictable set.
3262 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3264 VM_BUG_ON(PageActive(page));
3267 ClearPageUnevictable(page);
3268 if (page_evictable(page, NULL)) {
3269 enum lru_list l = page_lru_base_type(page);
3271 __dec_zone_state(zone, NR_UNEVICTABLE);
3272 list_move(&page->lru, &zone->lru[l].list);
3273 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3274 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3275 __count_vm_event(UNEVICTABLE_PGRESCUED);
3278 * rotate unevictable list
3280 SetPageUnevictable(page);
3281 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3282 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3283 if (page_evictable(page, NULL))
3289 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3290 * @mapping: struct address_space to scan for evictable pages
3292 * Scan all pages in mapping. Check unevictable pages for
3293 * evictability and move them to the appropriate zone lru list.
3295 void scan_mapping_unevictable_pages(struct address_space *mapping)
3298 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3301 struct pagevec pvec;
3303 if (mapping->nrpages == 0)
3306 pagevec_init(&pvec, 0);
3307 while (next < end &&
3308 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3314 for (i = 0; i < pagevec_count(&pvec); i++) {
3315 struct page *page = pvec.pages[i];
3316 pgoff_t page_index = page->index;
3317 struct zone *pagezone = page_zone(page);
3320 if (page_index > next)
3324 if (pagezone != zone) {
3326 spin_unlock_irq(&zone->lru_lock);
3328 spin_lock_irq(&zone->lru_lock);
3331 if (PageLRU(page) && PageUnevictable(page))
3332 check_move_unevictable_page(page, zone);
3335 spin_unlock_irq(&zone->lru_lock);
3336 pagevec_release(&pvec);
3338 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3344 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3345 * @zone - zone of which to scan the unevictable list
3347 * Scan @zone's unevictable LRU lists to check for pages that have become
3348 * evictable. Move those that have to @zone's inactive list where they
3349 * become candidates for reclaim, unless shrink_inactive_zone() decides
3350 * to reactivate them. Pages that are still unevictable are rotated
3351 * back onto @zone's unevictable list.
3353 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3354 static void scan_zone_unevictable_pages(struct zone *zone)
3356 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
3358 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
3360 while (nr_to_scan > 0) {
3361 unsigned long batch_size = min(nr_to_scan,
3362 SCAN_UNEVICTABLE_BATCH_SIZE);
3364 spin_lock_irq(&zone->lru_lock);
3365 for (scan = 0; scan < batch_size; scan++) {
3366 struct page *page = lru_to_page(l_unevictable);
3368 if (!trylock_page(page))
3371 prefetchw_prev_lru_page(page, l_unevictable, flags);
3373 if (likely(PageLRU(page) && PageUnevictable(page)))
3374 check_move_unevictable_page(page, zone);
3378 spin_unlock_irq(&zone->lru_lock);
3380 nr_to_scan -= batch_size;
3386 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3388 * A really big hammer: scan all zones' unevictable LRU lists to check for
3389 * pages that have become evictable. Move those back to the zones'
3390 * inactive list where they become candidates for reclaim.
3391 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3392 * and we add swap to the system. As such, it runs in the context of a task
3393 * that has possibly/probably made some previously unevictable pages
3396 static void scan_all_zones_unevictable_pages(void)
3400 for_each_zone(zone) {
3401 scan_zone_unevictable_pages(zone);
3406 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3407 * all nodes' unevictable lists for evictable pages
3409 unsigned long scan_unevictable_pages;
3411 int scan_unevictable_handler(struct ctl_table *table, int write,
3412 void __user *buffer,
3413 size_t *length, loff_t *ppos)
3415 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3417 if (write && *(unsigned long *)table->data)
3418 scan_all_zones_unevictable_pages();
3420 scan_unevictable_pages = 0;
3426 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3427 * a specified node's per zone unevictable lists for evictable pages.
3430 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3431 struct sysdev_attribute *attr,
3434 return sprintf(buf, "0\n"); /* always zero; should fit... */
3437 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3438 struct sysdev_attribute *attr,
3439 const char *buf, size_t count)
3441 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3444 unsigned long req = strict_strtoul(buf, 10, &res);
3447 return 1; /* zero is no-op */
3449 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3450 if (!populated_zone(zone))
3452 scan_zone_unevictable_pages(zone);
3458 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3459 read_scan_unevictable_node,
3460 write_scan_unevictable_node);
3462 int scan_unevictable_register_node(struct node *node)
3464 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3467 void scan_unevictable_unregister_node(struct node *node)
3469 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);