4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #include <linux/module.h>
16 #include <linux/gfp.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
45 #include <linux/prefetch.h>
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
50 #include <linux/swapops.h>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
58 * reclaim_mode determines how the inactive list is shrunk
59 * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
60 * RECLAIM_MODE_ASYNC: Do not block
61 * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
62 * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
63 * page from the LRU and reclaim all pages within a
64 * naturally aligned range
65 * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
66 * order-0 pages and then compact the zone
68 typedef unsigned __bitwise__ reclaim_mode_t;
69 #define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
70 #define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
71 #define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
72 #define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
73 #define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
76 /* Incremented by the number of inactive pages that were scanned */
77 unsigned long nr_scanned;
79 /* Number of pages freed so far during a call to shrink_zones() */
80 unsigned long nr_reclaimed;
82 /* How many pages shrink_list() should reclaim */
83 unsigned long nr_to_reclaim;
85 unsigned long hibernation_mode;
87 /* This context's GFP mask */
92 /* Can mapped pages be reclaimed? */
95 /* Can pages be swapped as part of reclaim? */
101 * Intend to reclaim enough continuous memory rather than reclaim
102 * enough amount of memory. i.e, mode for high order allocation.
104 reclaim_mode_t reclaim_mode;
106 /* Which cgroup do we reclaim from */
107 struct mem_cgroup *mem_cgroup;
110 * Nodemask of nodes allowed by the caller. If NULL, all nodes
113 nodemask_t *nodemask;
116 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
118 #ifdef ARCH_HAS_PREFETCH
119 #define prefetch_prev_lru_page(_page, _base, _field) \
121 if ((_page)->lru.prev != _base) { \
124 prev = lru_to_page(&(_page->lru)); \
125 prefetch(&prev->_field); \
129 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
132 #ifdef ARCH_HAS_PREFETCHW
133 #define prefetchw_prev_lru_page(_page, _base, _field) \
135 if ((_page)->lru.prev != _base) { \
138 prev = lru_to_page(&(_page->lru)); \
139 prefetchw(&prev->_field); \
143 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
147 * From 0 .. 100. Higher means more swappy.
149 int vm_swappiness = 60;
150 long vm_total_pages; /* The total number of pages which the VM controls */
152 static LIST_HEAD(shrinker_list);
153 static DECLARE_RWSEM(shrinker_rwsem);
155 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
156 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
158 #define scanning_global_lru(sc) (1)
161 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
162 struct scan_control *sc)
164 if (!scanning_global_lru(sc))
165 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
167 return &zone->reclaim_stat;
170 static unsigned long zone_nr_lru_pages(struct zone *zone,
171 struct scan_control *sc, enum lru_list lru)
173 if (!scanning_global_lru(sc))
174 return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup,
175 zone_to_nid(zone), zone_idx(zone), BIT(lru));
177 return zone_page_state(zone, NR_LRU_BASE + lru);
182 * Add a shrinker callback to be called from the vm
184 void register_shrinker(struct shrinker *shrinker)
187 down_write(&shrinker_rwsem);
188 list_add_tail(&shrinker->list, &shrinker_list);
189 up_write(&shrinker_rwsem);
191 EXPORT_SYMBOL(register_shrinker);
196 void unregister_shrinker(struct shrinker *shrinker)
198 down_write(&shrinker_rwsem);
199 list_del(&shrinker->list);
200 up_write(&shrinker_rwsem);
202 EXPORT_SYMBOL(unregister_shrinker);
204 static inline int do_shrinker_shrink(struct shrinker *shrinker,
205 struct shrink_control *sc,
206 unsigned long nr_to_scan)
208 sc->nr_to_scan = nr_to_scan;
209 return (*shrinker->shrink)(shrinker, sc);
212 #define SHRINK_BATCH 128
214 * Call the shrink functions to age shrinkable caches
216 * Here we assume it costs one seek to replace a lru page and that it also
217 * takes a seek to recreate a cache object. With this in mind we age equal
218 * percentages of the lru and ageable caches. This should balance the seeks
219 * generated by these structures.
221 * If the vm encountered mapped pages on the LRU it increase the pressure on
222 * slab to avoid swapping.
224 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
226 * `lru_pages' represents the number of on-LRU pages in all the zones which
227 * are eligible for the caller's allocation attempt. It is used for balancing
228 * slab reclaim versus page reclaim.
230 * Returns the number of slab objects which we shrunk.
232 unsigned long shrink_slab(struct shrink_control *shrink,
233 unsigned long nr_pages_scanned,
234 unsigned long lru_pages)
236 struct shrinker *shrinker;
237 unsigned long ret = 0;
239 if (nr_pages_scanned == 0)
240 nr_pages_scanned = SWAP_CLUSTER_MAX;
242 if (!down_read_trylock(&shrinker_rwsem)) {
243 /* Assume we'll be able to shrink next time */
248 list_for_each_entry(shrinker, &shrinker_list, list) {
249 unsigned long long delta;
250 unsigned long total_scan;
251 unsigned long max_pass;
255 long batch_size = shrinker->batch ? shrinker->batch
259 * copy the current shrinker scan count into a local variable
260 * and zero it so that other concurrent shrinker invocations
261 * don't also do this scanning work.
265 } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
268 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
269 delta = (4 * nr_pages_scanned) / shrinker->seeks;
271 do_div(delta, lru_pages + 1);
273 if (total_scan < 0) {
274 printk(KERN_ERR "shrink_slab: %pF negative objects to "
276 shrinker->shrink, total_scan);
277 total_scan = max_pass;
281 * We need to avoid excessive windup on filesystem shrinkers
282 * due to large numbers of GFP_NOFS allocations causing the
283 * shrinkers to return -1 all the time. This results in a large
284 * nr being built up so when a shrink that can do some work
285 * comes along it empties the entire cache due to nr >>>
286 * max_pass. This is bad for sustaining a working set in
289 * Hence only allow the shrinker to scan the entire cache when
290 * a large delta change is calculated directly.
292 if (delta < max_pass / 4)
293 total_scan = min(total_scan, max_pass / 2);
296 * Avoid risking looping forever due to too large nr value:
297 * never try to free more than twice the estimate number of
300 if (total_scan > max_pass * 2)
301 total_scan = max_pass * 2;
303 trace_mm_shrink_slab_start(shrinker, shrink, nr,
304 nr_pages_scanned, lru_pages,
305 max_pass, delta, total_scan);
307 while (total_scan >= batch_size) {
310 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
311 shrink_ret = do_shrinker_shrink(shrinker, shrink,
313 if (shrink_ret == -1)
315 if (shrink_ret < nr_before)
316 ret += nr_before - shrink_ret;
317 count_vm_events(SLABS_SCANNED, batch_size);
318 total_scan -= batch_size;
324 * move the unused scan count back into the shrinker in a
325 * manner that handles concurrent updates. If we exhausted the
326 * scan, there is no need to do an update.
330 new_nr = total_scan + nr;
333 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
335 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
337 up_read(&shrinker_rwsem);
343 static void set_reclaim_mode(int priority, struct scan_control *sc,
346 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
349 * Initially assume we are entering either lumpy reclaim or
350 * reclaim/compaction.Depending on the order, we will either set the
351 * sync mode or just reclaim order-0 pages later.
353 if (COMPACTION_BUILD)
354 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
356 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
359 * Avoid using lumpy reclaim or reclaim/compaction if possible by
360 * restricting when its set to either costly allocations or when
361 * under memory pressure
363 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
364 sc->reclaim_mode |= syncmode;
365 else if (sc->order && priority < DEF_PRIORITY - 2)
366 sc->reclaim_mode |= syncmode;
368 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
371 static void reset_reclaim_mode(struct scan_control *sc)
373 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
376 static inline int is_page_cache_freeable(struct page *page)
379 * A freeable page cache page is referenced only by the caller
380 * that isolated the page, the page cache radix tree and
381 * optional buffer heads at page->private.
383 return page_count(page) - page_has_private(page) == 2;
386 static int may_write_to_queue(struct backing_dev_info *bdi,
387 struct scan_control *sc)
389 if (current->flags & PF_SWAPWRITE)
391 if (!bdi_write_congested(bdi))
393 if (bdi == current->backing_dev_info)
396 /* lumpy reclaim for hugepage often need a lot of write */
397 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
403 * We detected a synchronous write error writing a page out. Probably
404 * -ENOSPC. We need to propagate that into the address_space for a subsequent
405 * fsync(), msync() or close().
407 * The tricky part is that after writepage we cannot touch the mapping: nothing
408 * prevents it from being freed up. But we have a ref on the page and once
409 * that page is locked, the mapping is pinned.
411 * We're allowed to run sleeping lock_page() here because we know the caller has
414 static void handle_write_error(struct address_space *mapping,
415 struct page *page, int error)
418 if (page_mapping(page) == mapping)
419 mapping_set_error(mapping, error);
423 /* possible outcome of pageout() */
425 /* failed to write page out, page is locked */
427 /* move page to the active list, page is locked */
429 /* page has been sent to the disk successfully, page is unlocked */
431 /* page is clean and locked */
436 * pageout is called by shrink_page_list() for each dirty page.
437 * Calls ->writepage().
439 static pageout_t pageout(struct page *page, struct address_space *mapping,
440 struct scan_control *sc)
443 * If the page is dirty, only perform writeback if that write
444 * will be non-blocking. To prevent this allocation from being
445 * stalled by pagecache activity. But note that there may be
446 * stalls if we need to run get_block(). We could test
447 * PagePrivate for that.
449 * If this process is currently in __generic_file_aio_write() against
450 * this page's queue, we can perform writeback even if that
453 * If the page is swapcache, write it back even if that would
454 * block, for some throttling. This happens by accident, because
455 * swap_backing_dev_info is bust: it doesn't reflect the
456 * congestion state of the swapdevs. Easy to fix, if needed.
458 if (!is_page_cache_freeable(page))
462 * Some data journaling orphaned pages can have
463 * page->mapping == NULL while being dirty with clean buffers.
465 if (page_has_private(page)) {
466 if (try_to_free_buffers(page)) {
467 ClearPageDirty(page);
468 printk("%s: orphaned page\n", __func__);
474 if (mapping->a_ops->writepage == NULL)
475 return PAGE_ACTIVATE;
476 if (!may_write_to_queue(mapping->backing_dev_info, sc))
479 if (clear_page_dirty_for_io(page)) {
481 struct writeback_control wbc = {
482 .sync_mode = WB_SYNC_NONE,
483 .nr_to_write = SWAP_CLUSTER_MAX,
485 .range_end = LLONG_MAX,
489 SetPageReclaim(page);
490 res = mapping->a_ops->writepage(page, &wbc);
492 handle_write_error(mapping, page, res);
493 if (res == AOP_WRITEPAGE_ACTIVATE) {
494 ClearPageReclaim(page);
495 return PAGE_ACTIVATE;
499 * Wait on writeback if requested to. This happens when
500 * direct reclaiming a large contiguous area and the
501 * first attempt to free a range of pages fails.
503 if (PageWriteback(page) &&
504 (sc->reclaim_mode & RECLAIM_MODE_SYNC))
505 wait_on_page_writeback(page);
507 if (!PageWriteback(page)) {
508 /* synchronous write or broken a_ops? */
509 ClearPageReclaim(page);
511 trace_mm_vmscan_writepage(page,
512 trace_reclaim_flags(page, sc->reclaim_mode));
513 inc_zone_page_state(page, NR_VMSCAN_WRITE);
521 * Same as remove_mapping, but if the page is removed from the mapping, it
522 * gets returned with a refcount of 0.
524 static int __remove_mapping(struct address_space *mapping, struct page *page)
526 BUG_ON(!PageLocked(page));
527 BUG_ON(mapping != page_mapping(page));
529 spin_lock_irq(&mapping->tree_lock);
531 * The non racy check for a busy page.
533 * Must be careful with the order of the tests. When someone has
534 * a ref to the page, it may be possible that they dirty it then
535 * drop the reference. So if PageDirty is tested before page_count
536 * here, then the following race may occur:
538 * get_user_pages(&page);
539 * [user mapping goes away]
541 * !PageDirty(page) [good]
542 * SetPageDirty(page);
544 * !page_count(page) [good, discard it]
546 * [oops, our write_to data is lost]
548 * Reversing the order of the tests ensures such a situation cannot
549 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
550 * load is not satisfied before that of page->_count.
552 * Note that if SetPageDirty is always performed via set_page_dirty,
553 * and thus under tree_lock, then this ordering is not required.
555 if (!page_freeze_refs(page, 2))
557 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
558 if (unlikely(PageDirty(page))) {
559 page_unfreeze_refs(page, 2);
563 if (PageSwapCache(page)) {
564 swp_entry_t swap = { .val = page_private(page) };
565 __delete_from_swap_cache(page);
566 spin_unlock_irq(&mapping->tree_lock);
567 swapcache_free(swap, page);
569 void (*freepage)(struct page *);
571 freepage = mapping->a_ops->freepage;
573 __delete_from_page_cache(page);
574 spin_unlock_irq(&mapping->tree_lock);
575 mem_cgroup_uncharge_cache_page(page);
577 if (freepage != NULL)
584 spin_unlock_irq(&mapping->tree_lock);
589 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
590 * someone else has a ref on the page, abort and return 0. If it was
591 * successfully detached, return 1. Assumes the caller has a single ref on
594 int remove_mapping(struct address_space *mapping, struct page *page)
596 if (__remove_mapping(mapping, page)) {
598 * Unfreezing the refcount with 1 rather than 2 effectively
599 * drops the pagecache ref for us without requiring another
602 page_unfreeze_refs(page, 1);
609 * putback_lru_page - put previously isolated page onto appropriate LRU list
610 * @page: page to be put back to appropriate lru list
612 * Add previously isolated @page to appropriate LRU list.
613 * Page may still be unevictable for other reasons.
615 * lru_lock must not be held, interrupts must be enabled.
617 void putback_lru_page(struct page *page)
620 int active = !!TestClearPageActive(page);
621 int was_unevictable = PageUnevictable(page);
623 VM_BUG_ON(PageLRU(page));
626 ClearPageUnevictable(page);
628 if (page_evictable(page, NULL)) {
630 * For evictable pages, we can use the cache.
631 * In event of a race, worst case is we end up with an
632 * unevictable page on [in]active list.
633 * We know how to handle that.
635 lru = active + page_lru_base_type(page);
636 lru_cache_add_lru(page, lru);
639 * Put unevictable pages directly on zone's unevictable
642 lru = LRU_UNEVICTABLE;
643 add_page_to_unevictable_list(page);
645 * When racing with an mlock clearing (page is
646 * unlocked), make sure that if the other thread does
647 * not observe our setting of PG_lru and fails
648 * isolation, we see PG_mlocked cleared below and move
649 * the page back to the evictable list.
651 * The other side is TestClearPageMlocked().
657 * page's status can change while we move it among lru. If an evictable
658 * page is on unevictable list, it never be freed. To avoid that,
659 * check after we added it to the list, again.
661 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
662 if (!isolate_lru_page(page)) {
666 /* This means someone else dropped this page from LRU
667 * So, it will be freed or putback to LRU again. There is
668 * nothing to do here.
672 if (was_unevictable && lru != LRU_UNEVICTABLE)
673 count_vm_event(UNEVICTABLE_PGRESCUED);
674 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
675 count_vm_event(UNEVICTABLE_PGCULLED);
677 put_page(page); /* drop ref from isolate */
680 enum page_references {
682 PAGEREF_RECLAIM_CLEAN,
687 static enum page_references page_check_references(struct page *page,
688 struct scan_control *sc)
690 int referenced_ptes, referenced_page;
691 unsigned long vm_flags;
693 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
694 referenced_page = TestClearPageReferenced(page);
696 /* Lumpy reclaim - ignore references */
697 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
698 return PAGEREF_RECLAIM;
701 * Mlock lost the isolation race with us. Let try_to_unmap()
702 * move the page to the unevictable list.
704 if (vm_flags & VM_LOCKED)
705 return PAGEREF_RECLAIM;
707 if (referenced_ptes) {
709 return PAGEREF_ACTIVATE;
711 * All mapped pages start out with page table
712 * references from the instantiating fault, so we need
713 * to look twice if a mapped file page is used more
716 * Mark it and spare it for another trip around the
717 * inactive list. Another page table reference will
718 * lead to its activation.
720 * Note: the mark is set for activated pages as well
721 * so that recently deactivated but used pages are
724 SetPageReferenced(page);
727 return PAGEREF_ACTIVATE;
732 /* Reclaim if clean, defer dirty pages to writeback */
733 if (referenced_page && !PageSwapBacked(page))
734 return PAGEREF_RECLAIM_CLEAN;
736 return PAGEREF_RECLAIM;
739 static noinline_for_stack void free_page_list(struct list_head *free_pages)
741 struct pagevec freed_pvec;
742 struct page *page, *tmp;
744 pagevec_init(&freed_pvec, 1);
746 list_for_each_entry_safe(page, tmp, free_pages, lru) {
747 list_del(&page->lru);
748 if (!pagevec_add(&freed_pvec, page)) {
749 __pagevec_free(&freed_pvec);
750 pagevec_reinit(&freed_pvec);
754 pagevec_free(&freed_pvec);
758 * shrink_page_list() returns the number of reclaimed pages
760 static unsigned long shrink_page_list(struct list_head *page_list,
762 struct scan_control *sc)
764 LIST_HEAD(ret_pages);
765 LIST_HEAD(free_pages);
767 unsigned long nr_dirty = 0;
768 unsigned long nr_congested = 0;
769 unsigned long nr_reclaimed = 0;
773 while (!list_empty(page_list)) {
774 enum page_references references;
775 struct address_space *mapping;
781 page = lru_to_page(page_list);
782 list_del(&page->lru);
784 if (!trylock_page(page))
787 VM_BUG_ON(PageActive(page));
788 VM_BUG_ON(page_zone(page) != zone);
792 if (unlikely(!page_evictable(page, NULL)))
795 if (!sc->may_unmap && page_mapped(page))
798 /* Double the slab pressure for mapped and swapcache pages */
799 if (page_mapped(page) || PageSwapCache(page))
802 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
803 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
805 if (PageWriteback(page)) {
807 * Synchronous reclaim is performed in two passes,
808 * first an asynchronous pass over the list to
809 * start parallel writeback, and a second synchronous
810 * pass to wait for the IO to complete. Wait here
811 * for any page for which writeback has already
814 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
816 wait_on_page_writeback(page);
823 references = page_check_references(page, sc);
824 switch (references) {
825 case PAGEREF_ACTIVATE:
826 goto activate_locked;
829 case PAGEREF_RECLAIM:
830 case PAGEREF_RECLAIM_CLEAN:
831 ; /* try to reclaim the page below */
835 * Anonymous process memory has backing store?
836 * Try to allocate it some swap space here.
838 if (PageAnon(page) && !PageSwapCache(page)) {
839 if (!(sc->gfp_mask & __GFP_IO))
841 if (!add_to_swap(page))
842 goto activate_locked;
846 mapping = page_mapping(page);
849 * The page is mapped into the page tables of one or more
850 * processes. Try to unmap it here.
852 if (page_mapped(page) && mapping) {
853 switch (try_to_unmap(page, TTU_UNMAP)) {
855 goto activate_locked;
861 ; /* try to free the page below */
865 if (PageDirty(page)) {
868 if (references == PAGEREF_RECLAIM_CLEAN)
872 if (!sc->may_writepage)
875 /* Page is dirty, try to write it out here */
876 switch (pageout(page, mapping, sc)) {
881 goto activate_locked;
883 if (PageWriteback(page))
889 * A synchronous write - probably a ramdisk. Go
890 * ahead and try to reclaim the page.
892 if (!trylock_page(page))
894 if (PageDirty(page) || PageWriteback(page))
896 mapping = page_mapping(page);
898 ; /* try to free the page below */
903 * If the page has buffers, try to free the buffer mappings
904 * associated with this page. If we succeed we try to free
907 * We do this even if the page is PageDirty().
908 * try_to_release_page() does not perform I/O, but it is
909 * possible for a page to have PageDirty set, but it is actually
910 * clean (all its buffers are clean). This happens if the
911 * buffers were written out directly, with submit_bh(). ext3
912 * will do this, as well as the blockdev mapping.
913 * try_to_release_page() will discover that cleanness and will
914 * drop the buffers and mark the page clean - it can be freed.
916 * Rarely, pages can have buffers and no ->mapping. These are
917 * the pages which were not successfully invalidated in
918 * truncate_complete_page(). We try to drop those buffers here
919 * and if that worked, and the page is no longer mapped into
920 * process address space (page_count == 1) it can be freed.
921 * Otherwise, leave the page on the LRU so it is swappable.
923 if (page_has_private(page)) {
924 if (!try_to_release_page(page, sc->gfp_mask))
925 goto activate_locked;
926 if (!mapping && page_count(page) == 1) {
928 if (put_page_testzero(page))
932 * rare race with speculative reference.
933 * the speculative reference will free
934 * this page shortly, so we may
935 * increment nr_reclaimed here (and
936 * leave it off the LRU).
944 if (!mapping || !__remove_mapping(mapping, page))
948 * At this point, we have no other references and there is
949 * no way to pick any more up (removed from LRU, removed
950 * from pagecache). Can use non-atomic bitops now (and
951 * we obviously don't have to worry about waking up a process
952 * waiting on the page lock, because there are no references.
954 __clear_page_locked(page);
959 * Is there need to periodically free_page_list? It would
960 * appear not as the counts should be low
962 list_add(&page->lru, &free_pages);
966 if (PageSwapCache(page))
967 try_to_free_swap(page);
969 putback_lru_page(page);
970 reset_reclaim_mode(sc);
974 /* Not a candidate for swapping, so reclaim swap space. */
975 if (PageSwapCache(page) && vm_swap_full())
976 try_to_free_swap(page);
977 VM_BUG_ON(PageActive(page));
983 reset_reclaim_mode(sc);
985 list_add(&page->lru, &ret_pages);
986 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
990 * Tag a zone as congested if all the dirty pages encountered were
991 * backed by a congested BDI. In this case, reclaimers should just
992 * back off and wait for congestion to clear because further reclaim
993 * will encounter the same problem
995 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
996 zone_set_flag(zone, ZONE_CONGESTED);
998 free_page_list(&free_pages);
1000 list_splice(&ret_pages, page_list);
1001 count_vm_events(PGACTIVATE, pgactivate);
1002 return nr_reclaimed;
1006 * Attempt to remove the specified page from its LRU. Only take this page
1007 * if it is of the appropriate PageActive status. Pages which are being
1008 * freed elsewhere are also ignored.
1010 * page: page to consider
1011 * mode: one of the LRU isolation modes defined above
1013 * returns 0 on success, -ve errno on failure.
1015 int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
1020 /* Only take pages on the LRU. */
1024 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
1025 (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
1028 * When checking the active state, we need to be sure we are
1029 * dealing with comparible boolean values. Take the logical not
1032 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
1035 if (!all_lru_mode && !!page_is_file_cache(page) != file)
1039 * When this function is being called for lumpy reclaim, we
1040 * initially look into all LRU pages, active, inactive and
1041 * unevictable; only give shrink_page_list evictable pages.
1043 if (PageUnevictable(page))
1048 if (likely(get_page_unless_zero(page))) {
1050 * Be careful not to clear PageLRU until after we're
1051 * sure the page is not being freed elsewhere -- the
1052 * page release code relies on it.
1062 * zone->lru_lock is heavily contended. Some of the functions that
1063 * shrink the lists perform better by taking out a batch of pages
1064 * and working on them outside the LRU lock.
1066 * For pagecache intensive workloads, this function is the hottest
1067 * spot in the kernel (apart from copy_*_user functions).
1069 * Appropriate locks must be held before calling this function.
1071 * @nr_to_scan: The number of pages to look through on the list.
1072 * @src: The LRU list to pull pages off.
1073 * @dst: The temp list to put pages on to.
1074 * @scanned: The number of pages that were scanned.
1075 * @order: The caller's attempted allocation order
1076 * @mode: One of the LRU isolation modes
1077 * @file: True [1] if isolating file [!anon] pages
1079 * returns how many pages were moved onto *@dst.
1081 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1082 struct list_head *src, struct list_head *dst,
1083 unsigned long *scanned, int order, isolate_mode_t mode,
1086 unsigned long nr_taken = 0;
1087 unsigned long nr_lumpy_taken = 0;
1088 unsigned long nr_lumpy_dirty = 0;
1089 unsigned long nr_lumpy_failed = 0;
1092 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1095 unsigned long end_pfn;
1096 unsigned long page_pfn;
1099 page = lru_to_page(src);
1100 prefetchw_prev_lru_page(page, src, flags);
1102 VM_BUG_ON(!PageLRU(page));
1104 switch (__isolate_lru_page(page, mode, file)) {
1106 list_move(&page->lru, dst);
1107 mem_cgroup_del_lru(page);
1108 nr_taken += hpage_nr_pages(page);
1112 /* else it is being freed elsewhere */
1113 list_move(&page->lru, src);
1114 mem_cgroup_rotate_lru_list(page, page_lru(page));
1125 * Attempt to take all pages in the order aligned region
1126 * surrounding the tag page. Only take those pages of
1127 * the same active state as that tag page. We may safely
1128 * round the target page pfn down to the requested order
1129 * as the mem_map is guaranteed valid out to MAX_ORDER,
1130 * where that page is in a different zone we will detect
1131 * it from its zone id and abort this block scan.
1133 zone_id = page_zone_id(page);
1134 page_pfn = page_to_pfn(page);
1135 pfn = page_pfn & ~((1 << order) - 1);
1136 end_pfn = pfn + (1 << order);
1137 for (; pfn < end_pfn; pfn++) {
1138 struct page *cursor_page;
1140 /* The target page is in the block, ignore it. */
1141 if (unlikely(pfn == page_pfn))
1144 /* Avoid holes within the zone. */
1145 if (unlikely(!pfn_valid_within(pfn)))
1148 cursor_page = pfn_to_page(pfn);
1150 /* Check that we have not crossed a zone boundary. */
1151 if (unlikely(page_zone_id(cursor_page) != zone_id))
1155 * If we don't have enough swap space, reclaiming of
1156 * anon page which don't already have a swap slot is
1159 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1160 !PageSwapCache(cursor_page))
1163 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1164 list_move(&cursor_page->lru, dst);
1165 mem_cgroup_del_lru(cursor_page);
1166 nr_taken += hpage_nr_pages(page);
1168 if (PageDirty(cursor_page))
1173 * Check if the page is freed already.
1175 * We can't use page_count() as that
1176 * requires compound_head and we don't
1177 * have a pin on the page here. If a
1178 * page is tail, we may or may not
1179 * have isolated the head, so assume
1180 * it's not free, it'd be tricky to
1181 * track the head status without a
1184 if (!PageTail(cursor_page) &&
1185 !atomic_read(&cursor_page->_count))
1191 /* If we break out of the loop above, lumpy reclaim failed */
1198 trace_mm_vmscan_lru_isolate(order,
1201 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1206 static unsigned long isolate_pages_global(unsigned long nr,
1207 struct list_head *dst,
1208 unsigned long *scanned, int order,
1209 isolate_mode_t mode,
1210 struct zone *z, int active, int file)
1217 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1222 * clear_active_flags() is a helper for shrink_active_list(), clearing
1223 * any active bits from the pages in the list.
1225 static unsigned long clear_active_flags(struct list_head *page_list,
1226 unsigned int *count)
1232 list_for_each_entry(page, page_list, lru) {
1233 int numpages = hpage_nr_pages(page);
1234 lru = page_lru_base_type(page);
1235 if (PageActive(page)) {
1237 ClearPageActive(page);
1238 nr_active += numpages;
1241 count[lru] += numpages;
1248 * isolate_lru_page - tries to isolate a page from its LRU list
1249 * @page: page to isolate from its LRU list
1251 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1252 * vmstat statistic corresponding to whatever LRU list the page was on.
1254 * Returns 0 if the page was removed from an LRU list.
1255 * Returns -EBUSY if the page was not on an LRU list.
1257 * The returned page will have PageLRU() cleared. If it was found on
1258 * the active list, it will have PageActive set. If it was found on
1259 * the unevictable list, it will have the PageUnevictable bit set. That flag
1260 * may need to be cleared by the caller before letting the page go.
1262 * The vmstat statistic corresponding to the list on which the page was
1263 * found will be decremented.
1266 * (1) Must be called with an elevated refcount on the page. This is a
1267 * fundamentnal difference from isolate_lru_pages (which is called
1268 * without a stable reference).
1269 * (2) the lru_lock must not be held.
1270 * (3) interrupts must be enabled.
1272 int isolate_lru_page(struct page *page)
1276 VM_BUG_ON(!page_count(page));
1278 if (PageLRU(page)) {
1279 struct zone *zone = page_zone(page);
1281 spin_lock_irq(&zone->lru_lock);
1282 if (PageLRU(page)) {
1283 int lru = page_lru(page);
1288 del_page_from_lru_list(zone, page, lru);
1290 spin_unlock_irq(&zone->lru_lock);
1296 * Are there way too many processes in the direct reclaim path already?
1298 static int too_many_isolated(struct zone *zone, int file,
1299 struct scan_control *sc)
1301 unsigned long inactive, isolated;
1303 if (current_is_kswapd())
1306 if (!scanning_global_lru(sc))
1310 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1311 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1313 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1314 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1317 return isolated > inactive;
1321 * TODO: Try merging with migrations version of putback_lru_pages
1323 static noinline_for_stack void
1324 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1325 unsigned long nr_anon, unsigned long nr_file,
1326 struct list_head *page_list)
1329 struct pagevec pvec;
1330 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1332 pagevec_init(&pvec, 1);
1335 * Put back any unfreeable pages.
1337 spin_lock(&zone->lru_lock);
1338 while (!list_empty(page_list)) {
1340 page = lru_to_page(page_list);
1341 VM_BUG_ON(PageLRU(page));
1342 list_del(&page->lru);
1343 if (unlikely(!page_evictable(page, NULL))) {
1344 spin_unlock_irq(&zone->lru_lock);
1345 putback_lru_page(page);
1346 spin_lock_irq(&zone->lru_lock);
1350 lru = page_lru(page);
1351 add_page_to_lru_list(zone, page, lru);
1352 if (is_active_lru(lru)) {
1353 int file = is_file_lru(lru);
1354 int numpages = hpage_nr_pages(page);
1355 reclaim_stat->recent_rotated[file] += numpages;
1357 if (!pagevec_add(&pvec, page)) {
1358 spin_unlock_irq(&zone->lru_lock);
1359 __pagevec_release(&pvec);
1360 spin_lock_irq(&zone->lru_lock);
1363 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1364 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1366 spin_unlock_irq(&zone->lru_lock);
1367 pagevec_release(&pvec);
1370 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1371 struct scan_control *sc,
1372 unsigned long *nr_anon,
1373 unsigned long *nr_file,
1374 struct list_head *isolated_list)
1376 unsigned long nr_active;
1377 unsigned int count[NR_LRU_LISTS] = { 0, };
1378 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1380 nr_active = clear_active_flags(isolated_list, count);
1381 __count_vm_events(PGDEACTIVATE, nr_active);
1383 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1384 -count[LRU_ACTIVE_FILE]);
1385 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1386 -count[LRU_INACTIVE_FILE]);
1387 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1388 -count[LRU_ACTIVE_ANON]);
1389 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1390 -count[LRU_INACTIVE_ANON]);
1392 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1393 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1394 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1395 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1397 reclaim_stat->recent_scanned[0] += *nr_anon;
1398 reclaim_stat->recent_scanned[1] += *nr_file;
1402 * Returns true if the caller should wait to clean dirty/writeback pages.
1404 * If we are direct reclaiming for contiguous pages and we do not reclaim
1405 * everything in the list, try again and wait for writeback IO to complete.
1406 * This will stall high-order allocations noticeably. Only do that when really
1407 * need to free the pages under high memory pressure.
1409 static inline bool should_reclaim_stall(unsigned long nr_taken,
1410 unsigned long nr_freed,
1412 struct scan_control *sc)
1414 int lumpy_stall_priority;
1416 /* kswapd should not stall on sync IO */
1417 if (current_is_kswapd())
1420 /* Only stall on lumpy reclaim */
1421 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1424 /* If we have reclaimed everything on the isolated list, no stall */
1425 if (nr_freed == nr_taken)
1429 * For high-order allocations, there are two stall thresholds.
1430 * High-cost allocations stall immediately where as lower
1431 * order allocations such as stacks require the scanning
1432 * priority to be much higher before stalling.
1434 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1435 lumpy_stall_priority = DEF_PRIORITY;
1437 lumpy_stall_priority = DEF_PRIORITY / 3;
1439 return priority <= lumpy_stall_priority;
1443 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1444 * of reclaimed pages
1446 static noinline_for_stack unsigned long
1447 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1448 struct scan_control *sc, int priority, int file)
1450 LIST_HEAD(page_list);
1451 unsigned long nr_scanned;
1452 unsigned long nr_reclaimed = 0;
1453 unsigned long nr_taken;
1454 unsigned long nr_anon;
1455 unsigned long nr_file;
1456 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1458 while (unlikely(too_many_isolated(zone, file, sc))) {
1459 congestion_wait(BLK_RW_ASYNC, HZ/10);
1461 /* We are about to die and free our memory. Return now. */
1462 if (fatal_signal_pending(current))
1463 return SWAP_CLUSTER_MAX;
1466 set_reclaim_mode(priority, sc, false);
1467 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
1468 reclaim_mode |= ISOLATE_ACTIVE;
1471 spin_lock_irq(&zone->lru_lock);
1473 if (scanning_global_lru(sc)) {
1474 nr_taken = isolate_pages_global(nr_to_scan, &page_list,
1475 &nr_scanned, sc->order, reclaim_mode, zone, 0, file);
1476 zone->pages_scanned += nr_scanned;
1477 if (current_is_kswapd())
1478 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1481 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1484 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
1485 &nr_scanned, sc->order, reclaim_mode, zone,
1486 sc->mem_cgroup, 0, file);
1488 * mem_cgroup_isolate_pages() keeps track of
1489 * scanned pages on its own.
1493 if (nr_taken == 0) {
1494 spin_unlock_irq(&zone->lru_lock);
1498 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1500 spin_unlock_irq(&zone->lru_lock);
1502 nr_reclaimed = shrink_page_list(&page_list, zone, sc);
1504 /* Check if we should syncronously wait for writeback */
1505 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1506 set_reclaim_mode(priority, sc, true);
1507 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
1510 local_irq_disable();
1511 if (current_is_kswapd())
1512 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1513 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1515 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1517 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1519 nr_scanned, nr_reclaimed,
1521 trace_shrink_flags(file, sc->reclaim_mode));
1522 return nr_reclaimed;
1526 * This moves pages from the active list to the inactive list.
1528 * We move them the other way if the page is referenced by one or more
1529 * processes, from rmap.
1531 * If the pages are mostly unmapped, the processing is fast and it is
1532 * appropriate to hold zone->lru_lock across the whole operation. But if
1533 * the pages are mapped, the processing is slow (page_referenced()) so we
1534 * should drop zone->lru_lock around each page. It's impossible to balance
1535 * this, so instead we remove the pages from the LRU while processing them.
1536 * It is safe to rely on PG_active against the non-LRU pages in here because
1537 * nobody will play with that bit on a non-LRU page.
1539 * The downside is that we have to touch page->_count against each page.
1540 * But we had to alter page->flags anyway.
1543 static void move_active_pages_to_lru(struct zone *zone,
1544 struct list_head *list,
1547 unsigned long pgmoved = 0;
1548 struct pagevec pvec;
1551 pagevec_init(&pvec, 1);
1553 while (!list_empty(list)) {
1554 page = lru_to_page(list);
1556 VM_BUG_ON(PageLRU(page));
1559 list_move(&page->lru, &zone->lru[lru].list);
1560 mem_cgroup_add_lru_list(page, lru);
1561 pgmoved += hpage_nr_pages(page);
1563 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1564 spin_unlock_irq(&zone->lru_lock);
1565 if (buffer_heads_over_limit)
1566 pagevec_strip(&pvec);
1567 __pagevec_release(&pvec);
1568 spin_lock_irq(&zone->lru_lock);
1571 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1572 if (!is_active_lru(lru))
1573 __count_vm_events(PGDEACTIVATE, pgmoved);
1576 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1577 struct scan_control *sc, int priority, int file)
1579 unsigned long nr_taken;
1580 unsigned long pgscanned;
1581 unsigned long vm_flags;
1582 LIST_HEAD(l_hold); /* The pages which were snipped off */
1583 LIST_HEAD(l_active);
1584 LIST_HEAD(l_inactive);
1586 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1587 unsigned long nr_rotated = 0;
1590 spin_lock_irq(&zone->lru_lock);
1591 if (scanning_global_lru(sc)) {
1592 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1593 &pgscanned, sc->order,
1594 ISOLATE_ACTIVE, zone,
1596 zone->pages_scanned += pgscanned;
1598 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1599 &pgscanned, sc->order,
1600 ISOLATE_ACTIVE, zone,
1601 sc->mem_cgroup, 1, file);
1603 * mem_cgroup_isolate_pages() keeps track of
1604 * scanned pages on its own.
1608 reclaim_stat->recent_scanned[file] += nr_taken;
1610 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1612 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1614 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1615 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1616 spin_unlock_irq(&zone->lru_lock);
1618 while (!list_empty(&l_hold)) {
1620 page = lru_to_page(&l_hold);
1621 list_del(&page->lru);
1623 if (unlikely(!page_evictable(page, NULL))) {
1624 putback_lru_page(page);
1628 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1629 nr_rotated += hpage_nr_pages(page);
1631 * Identify referenced, file-backed active pages and
1632 * give them one more trip around the active list. So
1633 * that executable code get better chances to stay in
1634 * memory under moderate memory pressure. Anon pages
1635 * are not likely to be evicted by use-once streaming
1636 * IO, plus JVM can create lots of anon VM_EXEC pages,
1637 * so we ignore them here.
1639 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1640 list_add(&page->lru, &l_active);
1645 ClearPageActive(page); /* we are de-activating */
1646 list_add(&page->lru, &l_inactive);
1650 * Move pages back to the lru list.
1652 spin_lock_irq(&zone->lru_lock);
1654 * Count referenced pages from currently used mappings as rotated,
1655 * even though only some of them are actually re-activated. This
1656 * helps balance scan pressure between file and anonymous pages in
1659 reclaim_stat->recent_rotated[file] += nr_rotated;
1661 move_active_pages_to_lru(zone, &l_active,
1662 LRU_ACTIVE + file * LRU_FILE);
1663 move_active_pages_to_lru(zone, &l_inactive,
1664 LRU_BASE + file * LRU_FILE);
1665 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1666 spin_unlock_irq(&zone->lru_lock);
1670 static int inactive_anon_is_low_global(struct zone *zone)
1672 unsigned long active, inactive;
1674 active = zone_page_state(zone, NR_ACTIVE_ANON);
1675 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1677 if (inactive * zone->inactive_ratio < active)
1684 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1685 * @zone: zone to check
1686 * @sc: scan control of this context
1688 * Returns true if the zone does not have enough inactive anon pages,
1689 * meaning some active anon pages need to be deactivated.
1691 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1696 * If we don't have swap space, anonymous page deactivation
1699 if (!total_swap_pages)
1702 if (scanning_global_lru(sc))
1703 low = inactive_anon_is_low_global(zone);
1705 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1709 static inline int inactive_anon_is_low(struct zone *zone,
1710 struct scan_control *sc)
1716 static int inactive_file_is_low_global(struct zone *zone)
1718 unsigned long active, inactive;
1720 active = zone_page_state(zone, NR_ACTIVE_FILE);
1721 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1723 return (active > inactive);
1727 * inactive_file_is_low - check if file pages need to be deactivated
1728 * @zone: zone to check
1729 * @sc: scan control of this context
1731 * When the system is doing streaming IO, memory pressure here
1732 * ensures that active file pages get deactivated, until more
1733 * than half of the file pages are on the inactive list.
1735 * Once we get to that situation, protect the system's working
1736 * set from being evicted by disabling active file page aging.
1738 * This uses a different ratio than the anonymous pages, because
1739 * the page cache uses a use-once replacement algorithm.
1741 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1745 if (scanning_global_lru(sc))
1746 low = inactive_file_is_low_global(zone);
1748 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1752 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1756 return inactive_file_is_low(zone, sc);
1758 return inactive_anon_is_low(zone, sc);
1761 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1762 struct zone *zone, struct scan_control *sc, int priority)
1764 int file = is_file_lru(lru);
1766 if (is_active_lru(lru)) {
1767 if (inactive_list_is_low(zone, sc, file))
1768 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1772 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1775 static int vmscan_swappiness(struct scan_control *sc)
1777 if (scanning_global_lru(sc))
1778 return vm_swappiness;
1779 return mem_cgroup_swappiness(sc->mem_cgroup);
1783 * Determine how aggressively the anon and file LRU lists should be
1784 * scanned. The relative value of each set of LRU lists is determined
1785 * by looking at the fraction of the pages scanned we did rotate back
1786 * onto the active list instead of evict.
1788 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1790 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1791 unsigned long *nr, int priority)
1793 unsigned long anon, file, free;
1794 unsigned long anon_prio, file_prio;
1795 unsigned long ap, fp;
1796 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1797 u64 fraction[2], denominator;
1800 bool force_scan = false;
1801 unsigned long nr_force_scan[2];
1803 /* kswapd does zone balancing and needs to scan this zone */
1804 if (scanning_global_lru(sc) && current_is_kswapd())
1806 /* memcg may have small limit and need to avoid priority drop */
1807 if (!scanning_global_lru(sc))
1810 /* If we have no swap space, do not bother scanning anon pages. */
1811 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1816 nr_force_scan[0] = 0;
1817 nr_force_scan[1] = SWAP_CLUSTER_MAX;
1821 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1822 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1823 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1824 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1826 if (scanning_global_lru(sc)) {
1827 free = zone_page_state(zone, NR_FREE_PAGES);
1828 /* If we have very few page cache pages,
1829 force-scan anon pages. */
1830 if (unlikely(file + free <= high_wmark_pages(zone))) {
1834 nr_force_scan[0] = SWAP_CLUSTER_MAX;
1835 nr_force_scan[1] = 0;
1841 * With swappiness at 100, anonymous and file have the same priority.
1842 * This scanning priority is essentially the inverse of IO cost.
1844 anon_prio = vmscan_swappiness(sc);
1845 file_prio = 200 - vmscan_swappiness(sc);
1848 * OK, so we have swap space and a fair amount of page cache
1849 * pages. We use the recently rotated / recently scanned
1850 * ratios to determine how valuable each cache is.
1852 * Because workloads change over time (and to avoid overflow)
1853 * we keep these statistics as a floating average, which ends
1854 * up weighing recent references more than old ones.
1856 * anon in [0], file in [1]
1858 spin_lock_irq(&zone->lru_lock);
1859 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1860 reclaim_stat->recent_scanned[0] /= 2;
1861 reclaim_stat->recent_rotated[0] /= 2;
1864 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1865 reclaim_stat->recent_scanned[1] /= 2;
1866 reclaim_stat->recent_rotated[1] /= 2;
1870 * The amount of pressure on anon vs file pages is inversely
1871 * proportional to the fraction of recently scanned pages on
1872 * each list that were recently referenced and in active use.
1874 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1875 ap /= reclaim_stat->recent_rotated[0] + 1;
1877 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1878 fp /= reclaim_stat->recent_rotated[1] + 1;
1879 spin_unlock_irq(&zone->lru_lock);
1883 denominator = ap + fp + 1;
1885 unsigned long scan = SWAP_CLUSTER_MAX;
1886 nr_force_scan[0] = div64_u64(scan * ap, denominator);
1887 nr_force_scan[1] = div64_u64(scan * fp, denominator);
1890 for_each_evictable_lru(l) {
1891 int file = is_file_lru(l);
1894 scan = zone_nr_lru_pages(zone, sc, l);
1895 if (priority || noswap) {
1897 scan = div64_u64(scan * fraction[file], denominator);
1901 * If zone is small or memcg is small, nr[l] can be 0.
1902 * This results no-scan on this priority and priority drop down.
1903 * For global direct reclaim, it can visit next zone and tend
1904 * not to have problems. For global kswapd, it's for zone
1905 * balancing and it need to scan a small amounts. When using
1906 * memcg, priority drop can cause big latency. So, it's better
1907 * to scan small amount. See may_noscan above.
1909 if (!scan && force_scan)
1910 scan = nr_force_scan[file];
1916 * Reclaim/compaction depends on a number of pages being freed. To avoid
1917 * disruption to the system, a small number of order-0 pages continue to be
1918 * rotated and reclaimed in the normal fashion. However, by the time we get
1919 * back to the allocator and call try_to_compact_zone(), we ensure that
1920 * there are enough free pages for it to be likely successful
1922 static inline bool should_continue_reclaim(struct zone *zone,
1923 unsigned long nr_reclaimed,
1924 unsigned long nr_scanned,
1925 struct scan_control *sc)
1927 unsigned long pages_for_compaction;
1928 unsigned long inactive_lru_pages;
1930 /* If not in reclaim/compaction mode, stop */
1931 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1934 /* Consider stopping depending on scan and reclaim activity */
1935 if (sc->gfp_mask & __GFP_REPEAT) {
1937 * For __GFP_REPEAT allocations, stop reclaiming if the
1938 * full LRU list has been scanned and we are still failing
1939 * to reclaim pages. This full LRU scan is potentially
1940 * expensive but a __GFP_REPEAT caller really wants to succeed
1942 if (!nr_reclaimed && !nr_scanned)
1946 * For non-__GFP_REPEAT allocations which can presumably
1947 * fail without consequence, stop if we failed to reclaim
1948 * any pages from the last SWAP_CLUSTER_MAX number of
1949 * pages that were scanned. This will return to the
1950 * caller faster at the risk reclaim/compaction and
1951 * the resulting allocation attempt fails
1958 * If we have not reclaimed enough pages for compaction and the
1959 * inactive lists are large enough, continue reclaiming
1961 pages_for_compaction = (2UL << sc->order);
1962 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
1963 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1964 if (sc->nr_reclaimed < pages_for_compaction &&
1965 inactive_lru_pages > pages_for_compaction)
1968 /* If compaction would go ahead or the allocation would succeed, stop */
1969 switch (compaction_suitable(zone, sc->order)) {
1970 case COMPACT_PARTIAL:
1971 case COMPACT_CONTINUE:
1979 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1981 static void shrink_zone(int priority, struct zone *zone,
1982 struct scan_control *sc)
1984 unsigned long nr[NR_LRU_LISTS];
1985 unsigned long nr_to_scan;
1987 unsigned long nr_reclaimed, nr_scanned;
1988 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1992 nr_scanned = sc->nr_scanned;
1993 get_scan_count(zone, sc, nr, priority);
1995 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1996 nr[LRU_INACTIVE_FILE]) {
1997 for_each_evictable_lru(l) {
1999 nr_to_scan = min_t(unsigned long,
2000 nr[l], SWAP_CLUSTER_MAX);
2001 nr[l] -= nr_to_scan;
2003 nr_reclaimed += shrink_list(l, nr_to_scan,
2004 zone, sc, priority);
2008 * On large memory systems, scan >> priority can become
2009 * really large. This is fine for the starting priority;
2010 * we want to put equal scanning pressure on each zone.
2011 * However, if the VM has a harder time of freeing pages,
2012 * with multiple processes reclaiming pages, the total
2013 * freeing target can get unreasonably large.
2015 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2018 sc->nr_reclaimed += nr_reclaimed;
2021 * Even if we did not try to evict anon pages at all, we want to
2022 * rebalance the anon lru active/inactive ratio.
2024 if (inactive_anon_is_low(zone, sc))
2025 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
2027 /* reclaim/compaction might need reclaim to continue */
2028 if (should_continue_reclaim(zone, nr_reclaimed,
2029 sc->nr_scanned - nr_scanned, sc))
2032 throttle_vm_writeout(sc->gfp_mask);
2036 * This is the direct reclaim path, for page-allocating processes. We only
2037 * try to reclaim pages from zones which will satisfy the caller's allocation
2040 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2042 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2044 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2045 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2046 * zone defense algorithm.
2048 * If a zone is deemed to be full of pinned pages then just give it a light
2049 * scan then give up on it.
2051 static void shrink_zones(int priority, struct zonelist *zonelist,
2052 struct scan_control *sc)
2056 unsigned long nr_soft_reclaimed;
2057 unsigned long nr_soft_scanned;
2059 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2060 gfp_zone(sc->gfp_mask), sc->nodemask) {
2061 if (!populated_zone(zone))
2064 * Take care memory controller reclaiming has small influence
2067 if (scanning_global_lru(sc)) {
2068 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2070 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2071 continue; /* Let kswapd poll it */
2073 * This steals pages from memory cgroups over softlimit
2074 * and returns the number of reclaimed pages and
2075 * scanned pages. This works for global memory pressure
2076 * and balancing, not for a memcg's limit.
2078 nr_soft_scanned = 0;
2079 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2080 sc->order, sc->gfp_mask,
2082 sc->nr_reclaimed += nr_soft_reclaimed;
2083 sc->nr_scanned += nr_soft_scanned;
2084 /* need some check for avoid more shrink_zone() */
2087 shrink_zone(priority, zone, sc);
2091 static bool zone_reclaimable(struct zone *zone)
2093 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2096 /* All zones in zonelist are unreclaimable? */
2097 static bool all_unreclaimable(struct zonelist *zonelist,
2098 struct scan_control *sc)
2103 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2104 gfp_zone(sc->gfp_mask), sc->nodemask) {
2105 if (!populated_zone(zone))
2107 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2109 if (!zone->all_unreclaimable)
2117 * This is the main entry point to direct page reclaim.
2119 * If a full scan of the inactive list fails to free enough memory then we
2120 * are "out of memory" and something needs to be killed.
2122 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2123 * high - the zone may be full of dirty or under-writeback pages, which this
2124 * caller can't do much about. We kick the writeback threads and take explicit
2125 * naps in the hope that some of these pages can be written. But if the
2126 * allocating task holds filesystem locks which prevent writeout this might not
2127 * work, and the allocation attempt will fail.
2129 * returns: 0, if no pages reclaimed
2130 * else, the number of pages reclaimed
2132 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2133 struct scan_control *sc,
2134 struct shrink_control *shrink)
2137 unsigned long total_scanned = 0;
2138 struct reclaim_state *reclaim_state = current->reclaim_state;
2141 unsigned long writeback_threshold;
2144 delayacct_freepages_start();
2146 if (scanning_global_lru(sc))
2147 count_vm_event(ALLOCSTALL);
2149 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2152 disable_swap_token(sc->mem_cgroup);
2153 shrink_zones(priority, zonelist, sc);
2155 * Don't shrink slabs when reclaiming memory from
2156 * over limit cgroups
2158 if (scanning_global_lru(sc)) {
2159 unsigned long lru_pages = 0;
2160 for_each_zone_zonelist(zone, z, zonelist,
2161 gfp_zone(sc->gfp_mask)) {
2162 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2165 lru_pages += zone_reclaimable_pages(zone);
2168 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2169 if (reclaim_state) {
2170 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2171 reclaim_state->reclaimed_slab = 0;
2174 total_scanned += sc->nr_scanned;
2175 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2179 * Try to write back as many pages as we just scanned. This
2180 * tends to cause slow streaming writers to write data to the
2181 * disk smoothly, at the dirtying rate, which is nice. But
2182 * that's undesirable in laptop mode, where we *want* lumpy
2183 * writeout. So in laptop mode, write out the whole world.
2185 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2186 if (total_scanned > writeback_threshold) {
2187 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
2188 sc->may_writepage = 1;
2191 /* Take a nap, wait for some writeback to complete */
2192 if (!sc->hibernation_mode && sc->nr_scanned &&
2193 priority < DEF_PRIORITY - 2) {
2194 struct zone *preferred_zone;
2196 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2197 &cpuset_current_mems_allowed,
2199 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2204 delayacct_freepages_end();
2207 if (sc->nr_reclaimed)
2208 return sc->nr_reclaimed;
2211 * As hibernation is going on, kswapd is freezed so that it can't mark
2212 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2215 if (oom_killer_disabled)
2218 /* top priority shrink_zones still had more to do? don't OOM, then */
2219 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2225 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2226 gfp_t gfp_mask, nodemask_t *nodemask)
2228 unsigned long nr_reclaimed;
2229 struct scan_control sc = {
2230 .gfp_mask = gfp_mask,
2231 .may_writepage = !laptop_mode,
2232 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2237 .nodemask = nodemask,
2239 struct shrink_control shrink = {
2240 .gfp_mask = sc.gfp_mask,
2243 trace_mm_vmscan_direct_reclaim_begin(order,
2247 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2249 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2251 return nr_reclaimed;
2254 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2256 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2257 gfp_t gfp_mask, bool noswap,
2259 unsigned long *nr_scanned)
2261 struct scan_control sc = {
2263 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2264 .may_writepage = !laptop_mode,
2266 .may_swap = !noswap,
2271 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2272 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2274 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2279 * NOTE: Although we can get the priority field, using it
2280 * here is not a good idea, since it limits the pages we can scan.
2281 * if we don't reclaim here, the shrink_zone from balance_pgdat
2282 * will pick up pages from other mem cgroup's as well. We hack
2283 * the priority and make it zero.
2285 shrink_zone(0, zone, &sc);
2287 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2289 *nr_scanned = sc.nr_scanned;
2290 return sc.nr_reclaimed;
2293 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2297 struct zonelist *zonelist;
2298 unsigned long nr_reclaimed;
2300 struct scan_control sc = {
2301 .may_writepage = !laptop_mode,
2303 .may_swap = !noswap,
2304 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2306 .mem_cgroup = mem_cont,
2307 .nodemask = NULL, /* we don't care the placement */
2308 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2309 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2311 struct shrink_control shrink = {
2312 .gfp_mask = sc.gfp_mask,
2316 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2317 * take care of from where we get pages. So the node where we start the
2318 * scan does not need to be the current node.
2320 nid = mem_cgroup_select_victim_node(mem_cont);
2322 zonelist = NODE_DATA(nid)->node_zonelists;
2324 trace_mm_vmscan_memcg_reclaim_begin(0,
2328 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2330 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2332 return nr_reclaimed;
2337 * pgdat_balanced is used when checking if a node is balanced for high-order
2338 * allocations. Only zones that meet watermarks and are in a zone allowed
2339 * by the callers classzone_idx are added to balanced_pages. The total of
2340 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2341 * for the node to be considered balanced. Forcing all zones to be balanced
2342 * for high orders can cause excessive reclaim when there are imbalanced zones.
2343 * The choice of 25% is due to
2344 * o a 16M DMA zone that is balanced will not balance a zone on any
2345 * reasonable sized machine
2346 * o On all other machines, the top zone must be at least a reasonable
2347 * percentage of the middle zones. For example, on 32-bit x86, highmem
2348 * would need to be at least 256M for it to be balance a whole node.
2349 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2350 * to balance a node on its own. These seemed like reasonable ratios.
2352 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2355 unsigned long present_pages = 0;
2358 for (i = 0; i <= classzone_idx; i++)
2359 present_pages += pgdat->node_zones[i].present_pages;
2361 /* A special case here: if zone has no page, we think it's balanced */
2362 return balanced_pages >= (present_pages >> 2);
2365 /* is kswapd sleeping prematurely? */
2366 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2370 unsigned long balanced = 0;
2371 bool all_zones_ok = true;
2373 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2377 /* Check the watermark levels */
2378 for (i = 0; i <= classzone_idx; i++) {
2379 struct zone *zone = pgdat->node_zones + i;
2381 if (!populated_zone(zone))
2385 * balance_pgdat() skips over all_unreclaimable after
2386 * DEF_PRIORITY. Effectively, it considers them balanced so
2387 * they must be considered balanced here as well if kswapd
2390 if (zone->all_unreclaimable) {
2391 balanced += zone->present_pages;
2395 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2397 all_zones_ok = false;
2399 balanced += zone->present_pages;
2403 * For high-order requests, the balanced zones must contain at least
2404 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2408 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2410 return !all_zones_ok;
2414 * For kswapd, balance_pgdat() will work across all this node's zones until
2415 * they are all at high_wmark_pages(zone).
2417 * Returns the final order kswapd was reclaiming at
2419 * There is special handling here for zones which are full of pinned pages.
2420 * This can happen if the pages are all mlocked, or if they are all used by
2421 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2422 * What we do is to detect the case where all pages in the zone have been
2423 * scanned twice and there has been zero successful reclaim. Mark the zone as
2424 * dead and from now on, only perform a short scan. Basically we're polling
2425 * the zone for when the problem goes away.
2427 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2428 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2429 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2430 * lower zones regardless of the number of free pages in the lower zones. This
2431 * interoperates with the page allocator fallback scheme to ensure that aging
2432 * of pages is balanced across the zones.
2434 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2438 unsigned long balanced;
2441 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2442 unsigned long total_scanned;
2443 struct reclaim_state *reclaim_state = current->reclaim_state;
2444 unsigned long nr_soft_reclaimed;
2445 unsigned long nr_soft_scanned;
2446 struct scan_control sc = {
2447 .gfp_mask = GFP_KERNEL,
2451 * kswapd doesn't want to be bailed out while reclaim. because
2452 * we want to put equal scanning pressure on each zone.
2454 .nr_to_reclaim = ULONG_MAX,
2458 struct shrink_control shrink = {
2459 .gfp_mask = sc.gfp_mask,
2463 sc.nr_reclaimed = 0;
2464 sc.may_writepage = !laptop_mode;
2465 count_vm_event(PAGEOUTRUN);
2467 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2468 unsigned long lru_pages = 0;
2469 int has_under_min_watermark_zone = 0;
2471 /* The swap token gets in the way of swapout... */
2473 disable_swap_token(NULL);
2479 * Scan in the highmem->dma direction for the highest
2480 * zone which needs scanning
2482 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2483 struct zone *zone = pgdat->node_zones + i;
2485 if (!populated_zone(zone))
2488 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2492 * Do some background aging of the anon list, to give
2493 * pages a chance to be referenced before reclaiming.
2495 if (inactive_anon_is_low(zone, &sc))
2496 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2499 if (!zone_watermark_ok_safe(zone, order,
2500 high_wmark_pages(zone), 0, 0)) {
2504 /* If balanced, clear the congested flag */
2505 zone_clear_flag(zone, ZONE_CONGESTED);
2511 for (i = 0; i <= end_zone; i++) {
2512 struct zone *zone = pgdat->node_zones + i;
2514 lru_pages += zone_reclaimable_pages(zone);
2518 * Now scan the zone in the dma->highmem direction, stopping
2519 * at the last zone which needs scanning.
2521 * We do this because the page allocator works in the opposite
2522 * direction. This prevents the page allocator from allocating
2523 * pages behind kswapd's direction of progress, which would
2524 * cause too much scanning of the lower zones.
2526 for (i = 0; i <= end_zone; i++) {
2527 struct zone *zone = pgdat->node_zones + i;
2529 unsigned long balance_gap;
2531 if (!populated_zone(zone))
2534 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2539 nr_soft_scanned = 0;
2541 * Call soft limit reclaim before calling shrink_zone.
2543 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2546 sc.nr_reclaimed += nr_soft_reclaimed;
2547 total_scanned += nr_soft_scanned;
2550 * We put equal pressure on every zone, unless
2551 * one zone has way too many pages free
2552 * already. The "too many pages" is defined
2553 * as the high wmark plus a "gap" where the
2554 * gap is either the low watermark or 1%
2555 * of the zone, whichever is smaller.
2557 balance_gap = min(low_wmark_pages(zone),
2558 (zone->present_pages +
2559 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2560 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2561 if (!zone_watermark_ok_safe(zone, order,
2562 high_wmark_pages(zone) + balance_gap,
2564 shrink_zone(priority, zone, &sc);
2566 reclaim_state->reclaimed_slab = 0;
2567 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2568 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2569 total_scanned += sc.nr_scanned;
2571 if (nr_slab == 0 && !zone_reclaimable(zone))
2572 zone->all_unreclaimable = 1;
2576 * If we've done a decent amount of scanning and
2577 * the reclaim ratio is low, start doing writepage
2578 * even in laptop mode
2580 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2581 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2582 sc.may_writepage = 1;
2584 if (zone->all_unreclaimable) {
2585 if (end_zone && end_zone == i)
2590 if (!zone_watermark_ok_safe(zone, order,
2591 high_wmark_pages(zone), end_zone, 0)) {
2594 * We are still under min water mark. This
2595 * means that we have a GFP_ATOMIC allocation
2596 * failure risk. Hurry up!
2598 if (!zone_watermark_ok_safe(zone, order,
2599 min_wmark_pages(zone), end_zone, 0))
2600 has_under_min_watermark_zone = 1;
2603 * If a zone reaches its high watermark,
2604 * consider it to be no longer congested. It's
2605 * possible there are dirty pages backed by
2606 * congested BDIs but as pressure is relieved,
2607 * spectulatively avoid congestion waits
2609 zone_clear_flag(zone, ZONE_CONGESTED);
2610 if (i <= *classzone_idx)
2611 balanced += zone->present_pages;
2615 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2616 break; /* kswapd: all done */
2618 * OK, kswapd is getting into trouble. Take a nap, then take
2619 * another pass across the zones.
2621 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2622 if (has_under_min_watermark_zone)
2623 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2625 congestion_wait(BLK_RW_ASYNC, HZ/10);
2629 * We do this so kswapd doesn't build up large priorities for
2630 * example when it is freeing in parallel with allocators. It
2631 * matches the direct reclaim path behaviour in terms of impact
2632 * on zone->*_priority.
2634 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2640 * order-0: All zones must meet high watermark for a balanced node
2641 * high-order: Balanced zones must make up at least 25% of the node
2642 * for the node to be balanced
2644 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2650 * Fragmentation may mean that the system cannot be
2651 * rebalanced for high-order allocations in all zones.
2652 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2653 * it means the zones have been fully scanned and are still
2654 * not balanced. For high-order allocations, there is
2655 * little point trying all over again as kswapd may
2658 * Instead, recheck all watermarks at order-0 as they
2659 * are the most important. If watermarks are ok, kswapd will go
2660 * back to sleep. High-order users can still perform direct
2661 * reclaim if they wish.
2663 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2664 order = sc.order = 0;
2670 * If kswapd was reclaiming at a higher order, it has the option of
2671 * sleeping without all zones being balanced. Before it does, it must
2672 * ensure that the watermarks for order-0 on *all* zones are met and
2673 * that the congestion flags are cleared. The congestion flag must
2674 * be cleared as kswapd is the only mechanism that clears the flag
2675 * and it is potentially going to sleep here.
2678 for (i = 0; i <= end_zone; i++) {
2679 struct zone *zone = pgdat->node_zones + i;
2681 if (!populated_zone(zone))
2684 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2687 /* Confirm the zone is balanced for order-0 */
2688 if (!zone_watermark_ok(zone, 0,
2689 high_wmark_pages(zone), 0, 0)) {
2690 order = sc.order = 0;
2694 /* If balanced, clear the congested flag */
2695 zone_clear_flag(zone, ZONE_CONGESTED);
2700 * Return the order we were reclaiming at so sleeping_prematurely()
2701 * makes a decision on the order we were last reclaiming at. However,
2702 * if another caller entered the allocator slow path while kswapd
2703 * was awake, order will remain at the higher level
2705 *classzone_idx = end_zone;
2709 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2714 if (freezing(current) || kthread_should_stop())
2717 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2719 /* Try to sleep for a short interval */
2720 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2721 remaining = schedule_timeout(HZ/10);
2722 finish_wait(&pgdat->kswapd_wait, &wait);
2723 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2727 * After a short sleep, check if it was a premature sleep. If not, then
2728 * go fully to sleep until explicitly woken up.
2730 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2731 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2734 * vmstat counters are not perfectly accurate and the estimated
2735 * value for counters such as NR_FREE_PAGES can deviate from the
2736 * true value by nr_online_cpus * threshold. To avoid the zone
2737 * watermarks being breached while under pressure, we reduce the
2738 * per-cpu vmstat threshold while kswapd is awake and restore
2739 * them before going back to sleep.
2741 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2743 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2746 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2748 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2750 finish_wait(&pgdat->kswapd_wait, &wait);
2754 * The background pageout daemon, started as a kernel thread
2755 * from the init process.
2757 * This basically trickles out pages so that we have _some_
2758 * free memory available even if there is no other activity
2759 * that frees anything up. This is needed for things like routing
2760 * etc, where we otherwise might have all activity going on in
2761 * asynchronous contexts that cannot page things out.
2763 * If there are applications that are active memory-allocators
2764 * (most normal use), this basically shouldn't matter.
2766 static int kswapd(void *p)
2768 unsigned long order, new_order;
2769 int classzone_idx, new_classzone_idx;
2770 pg_data_t *pgdat = (pg_data_t*)p;
2771 struct task_struct *tsk = current;
2773 struct reclaim_state reclaim_state = {
2774 .reclaimed_slab = 0,
2776 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2778 lockdep_set_current_reclaim_state(GFP_KERNEL);
2780 if (!cpumask_empty(cpumask))
2781 set_cpus_allowed_ptr(tsk, cpumask);
2782 current->reclaim_state = &reclaim_state;
2785 * Tell the memory management that we're a "memory allocator",
2786 * and that if we need more memory we should get access to it
2787 * regardless (see "__alloc_pages()"). "kswapd" should
2788 * never get caught in the normal page freeing logic.
2790 * (Kswapd normally doesn't need memory anyway, but sometimes
2791 * you need a small amount of memory in order to be able to
2792 * page out something else, and this flag essentially protects
2793 * us from recursively trying to free more memory as we're
2794 * trying to free the first piece of memory in the first place).
2796 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2799 order = new_order = 0;
2800 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2805 * If the last balance_pgdat was unsuccessful it's unlikely a
2806 * new request of a similar or harder type will succeed soon
2807 * so consider going to sleep on the basis we reclaimed at
2809 if (classzone_idx >= new_classzone_idx && order == new_order) {
2810 new_order = pgdat->kswapd_max_order;
2811 new_classzone_idx = pgdat->classzone_idx;
2812 pgdat->kswapd_max_order = 0;
2813 pgdat->classzone_idx = pgdat->nr_zones - 1;
2816 if (order < new_order || classzone_idx > new_classzone_idx) {
2818 * Don't sleep if someone wants a larger 'order'
2819 * allocation or has tigher zone constraints
2822 classzone_idx = new_classzone_idx;
2824 kswapd_try_to_sleep(pgdat, order, classzone_idx);
2825 order = pgdat->kswapd_max_order;
2826 classzone_idx = pgdat->classzone_idx;
2827 pgdat->kswapd_max_order = 0;
2828 pgdat->classzone_idx = pgdat->nr_zones - 1;
2831 ret = try_to_freeze();
2832 if (kthread_should_stop())
2836 * We can speed up thawing tasks if we don't call balance_pgdat
2837 * after returning from the refrigerator
2840 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2841 order = balance_pgdat(pgdat, order, &classzone_idx);
2848 * A zone is low on free memory, so wake its kswapd task to service it.
2850 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2854 if (!populated_zone(zone))
2857 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2859 pgdat = zone->zone_pgdat;
2860 if (pgdat->kswapd_max_order < order) {
2861 pgdat->kswapd_max_order = order;
2862 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2864 if (!waitqueue_active(&pgdat->kswapd_wait))
2866 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2869 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2870 wake_up_interruptible(&pgdat->kswapd_wait);
2874 * The reclaimable count would be mostly accurate.
2875 * The less reclaimable pages may be
2876 * - mlocked pages, which will be moved to unevictable list when encountered
2877 * - mapped pages, which may require several travels to be reclaimed
2878 * - dirty pages, which is not "instantly" reclaimable
2880 unsigned long global_reclaimable_pages(void)
2884 nr = global_page_state(NR_ACTIVE_FILE) +
2885 global_page_state(NR_INACTIVE_FILE);
2887 if (nr_swap_pages > 0)
2888 nr += global_page_state(NR_ACTIVE_ANON) +
2889 global_page_state(NR_INACTIVE_ANON);
2894 unsigned long zone_reclaimable_pages(struct zone *zone)
2898 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2899 zone_page_state(zone, NR_INACTIVE_FILE);
2901 if (nr_swap_pages > 0)
2902 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2903 zone_page_state(zone, NR_INACTIVE_ANON);
2908 #ifdef CONFIG_HIBERNATION
2910 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2913 * Rather than trying to age LRUs the aim is to preserve the overall
2914 * LRU order by reclaiming preferentially
2915 * inactive > active > active referenced > active mapped
2917 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2919 struct reclaim_state reclaim_state;
2920 struct scan_control sc = {
2921 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2925 .nr_to_reclaim = nr_to_reclaim,
2926 .hibernation_mode = 1,
2929 struct shrink_control shrink = {
2930 .gfp_mask = sc.gfp_mask,
2932 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2933 struct task_struct *p = current;
2934 unsigned long nr_reclaimed;
2936 p->flags |= PF_MEMALLOC;
2937 lockdep_set_current_reclaim_state(sc.gfp_mask);
2938 reclaim_state.reclaimed_slab = 0;
2939 p->reclaim_state = &reclaim_state;
2941 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2943 p->reclaim_state = NULL;
2944 lockdep_clear_current_reclaim_state();
2945 p->flags &= ~PF_MEMALLOC;
2947 return nr_reclaimed;
2949 #endif /* CONFIG_HIBERNATION */
2951 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2952 not required for correctness. So if the last cpu in a node goes
2953 away, we get changed to run anywhere: as the first one comes back,
2954 restore their cpu bindings. */
2955 static int __devinit cpu_callback(struct notifier_block *nfb,
2956 unsigned long action, void *hcpu)
2960 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2961 for_each_node_state(nid, N_HIGH_MEMORY) {
2962 pg_data_t *pgdat = NODE_DATA(nid);
2963 const struct cpumask *mask;
2965 mask = cpumask_of_node(pgdat->node_id);
2967 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2968 /* One of our CPUs online: restore mask */
2969 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2976 * This kswapd start function will be called by init and node-hot-add.
2977 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2979 int kswapd_run(int nid)
2981 pg_data_t *pgdat = NODE_DATA(nid);
2987 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2988 if (IS_ERR(pgdat->kswapd)) {
2989 /* failure at boot is fatal */
2990 BUG_ON(system_state == SYSTEM_BOOTING);
2991 printk("Failed to start kswapd on node %d\n",nid);
2998 * Called by memory hotplug when all memory in a node is offlined.
3000 void kswapd_stop(int nid)
3002 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3005 kthread_stop(kswapd);
3008 static int __init kswapd_init(void)
3013 for_each_node_state(nid, N_HIGH_MEMORY)
3015 hotcpu_notifier(cpu_callback, 0);
3019 module_init(kswapd_init)
3025 * If non-zero call zone_reclaim when the number of free pages falls below
3028 int zone_reclaim_mode __read_mostly;
3030 #define RECLAIM_OFF 0
3031 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3032 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3033 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3036 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3037 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3040 #define ZONE_RECLAIM_PRIORITY 4
3043 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3046 int sysctl_min_unmapped_ratio = 1;
3049 * If the number of slab pages in a zone grows beyond this percentage then
3050 * slab reclaim needs to occur.
3052 int sysctl_min_slab_ratio = 5;
3054 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3056 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3057 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3058 zone_page_state(zone, NR_ACTIVE_FILE);
3061 * It's possible for there to be more file mapped pages than
3062 * accounted for by the pages on the file LRU lists because
3063 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3065 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3068 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3069 static long zone_pagecache_reclaimable(struct zone *zone)
3071 long nr_pagecache_reclaimable;
3075 * If RECLAIM_SWAP is set, then all file pages are considered
3076 * potentially reclaimable. Otherwise, we have to worry about
3077 * pages like swapcache and zone_unmapped_file_pages() provides
3080 if (zone_reclaim_mode & RECLAIM_SWAP)
3081 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3083 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3085 /* If we can't clean pages, remove dirty pages from consideration */
3086 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3087 delta += zone_page_state(zone, NR_FILE_DIRTY);
3089 /* Watch for any possible underflows due to delta */
3090 if (unlikely(delta > nr_pagecache_reclaimable))
3091 delta = nr_pagecache_reclaimable;
3093 return nr_pagecache_reclaimable - delta;
3097 * Try to free up some pages from this zone through reclaim.
3099 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3101 /* Minimum pages needed in order to stay on node */
3102 const unsigned long nr_pages = 1 << order;
3103 struct task_struct *p = current;
3104 struct reclaim_state reclaim_state;
3106 struct scan_control sc = {
3107 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3108 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3110 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3112 .gfp_mask = gfp_mask,
3115 struct shrink_control shrink = {
3116 .gfp_mask = sc.gfp_mask,
3118 unsigned long nr_slab_pages0, nr_slab_pages1;
3122 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3123 * and we also need to be able to write out pages for RECLAIM_WRITE
3126 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3127 lockdep_set_current_reclaim_state(gfp_mask);
3128 reclaim_state.reclaimed_slab = 0;
3129 p->reclaim_state = &reclaim_state;
3131 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3133 * Free memory by calling shrink zone with increasing
3134 * priorities until we have enough memory freed.
3136 priority = ZONE_RECLAIM_PRIORITY;
3138 shrink_zone(priority, zone, &sc);
3140 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3143 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3144 if (nr_slab_pages0 > zone->min_slab_pages) {
3146 * shrink_slab() does not currently allow us to determine how
3147 * many pages were freed in this zone. So we take the current
3148 * number of slab pages and shake the slab until it is reduced
3149 * by the same nr_pages that we used for reclaiming unmapped
3152 * Note that shrink_slab will free memory on all zones and may
3156 unsigned long lru_pages = zone_reclaimable_pages(zone);
3158 /* No reclaimable slab or very low memory pressure */
3159 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3162 /* Freed enough memory */
3163 nr_slab_pages1 = zone_page_state(zone,
3164 NR_SLAB_RECLAIMABLE);
3165 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3170 * Update nr_reclaimed by the number of slab pages we
3171 * reclaimed from this zone.
3173 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3174 if (nr_slab_pages1 < nr_slab_pages0)
3175 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3178 p->reclaim_state = NULL;
3179 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3180 lockdep_clear_current_reclaim_state();
3181 return sc.nr_reclaimed >= nr_pages;
3184 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3190 * Zone reclaim reclaims unmapped file backed pages and
3191 * slab pages if we are over the defined limits.
3193 * A small portion of unmapped file backed pages is needed for
3194 * file I/O otherwise pages read by file I/O will be immediately
3195 * thrown out if the zone is overallocated. So we do not reclaim
3196 * if less than a specified percentage of the zone is used by
3197 * unmapped file backed pages.
3199 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3200 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3201 return ZONE_RECLAIM_FULL;
3203 if (zone->all_unreclaimable)
3204 return ZONE_RECLAIM_FULL;
3207 * Do not scan if the allocation should not be delayed.
3209 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3210 return ZONE_RECLAIM_NOSCAN;
3213 * Only run zone reclaim on the local zone or on zones that do not
3214 * have associated processors. This will favor the local processor
3215 * over remote processors and spread off node memory allocations
3216 * as wide as possible.
3218 node_id = zone_to_nid(zone);
3219 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3220 return ZONE_RECLAIM_NOSCAN;
3222 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3223 return ZONE_RECLAIM_NOSCAN;
3225 ret = __zone_reclaim(zone, gfp_mask, order);
3226 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3229 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3236 * page_evictable - test whether a page is evictable
3237 * @page: the page to test
3238 * @vma: the VMA in which the page is or will be mapped, may be NULL
3240 * Test whether page is evictable--i.e., should be placed on active/inactive
3241 * lists vs unevictable list. The vma argument is !NULL when called from the
3242 * fault path to determine how to instantate a new page.
3244 * Reasons page might not be evictable:
3245 * (1) page's mapping marked unevictable
3246 * (2) page is part of an mlocked VMA
3249 int page_evictable(struct page *page, struct vm_area_struct *vma)
3252 if (mapping_unevictable(page_mapping(page)))
3255 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3262 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3263 * @page: page to check evictability and move to appropriate lru list
3264 * @zone: zone page is in
3266 * Checks a page for evictability and moves the page to the appropriate
3269 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3270 * have PageUnevictable set.
3272 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3274 VM_BUG_ON(PageActive(page));
3277 ClearPageUnevictable(page);
3278 if (page_evictable(page, NULL)) {
3279 enum lru_list l = page_lru_base_type(page);
3281 __dec_zone_state(zone, NR_UNEVICTABLE);
3282 list_move(&page->lru, &zone->lru[l].list);
3283 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3284 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3285 __count_vm_event(UNEVICTABLE_PGRESCUED);
3288 * rotate unevictable list
3290 SetPageUnevictable(page);
3291 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3292 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3293 if (page_evictable(page, NULL))
3299 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3300 * @mapping: struct address_space to scan for evictable pages
3302 * Scan all pages in mapping. Check unevictable pages for
3303 * evictability and move them to the appropriate zone lru list.
3305 void scan_mapping_unevictable_pages(struct address_space *mapping)
3308 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3311 struct pagevec pvec;
3313 if (mapping->nrpages == 0)
3316 pagevec_init(&pvec, 0);
3317 while (next < end &&
3318 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3324 for (i = 0; i < pagevec_count(&pvec); i++) {
3325 struct page *page = pvec.pages[i];
3326 pgoff_t page_index = page->index;
3327 struct zone *pagezone = page_zone(page);
3330 if (page_index > next)
3334 if (pagezone != zone) {
3336 spin_unlock_irq(&zone->lru_lock);
3338 spin_lock_irq(&zone->lru_lock);
3341 if (PageLRU(page) && PageUnevictable(page))
3342 check_move_unevictable_page(page, zone);
3345 spin_unlock_irq(&zone->lru_lock);
3346 pagevec_release(&pvec);
3348 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3354 * scan_zone_unevictable_pages - check unevictable list for evictable pages
3355 * @zone - zone of which to scan the unevictable list
3357 * Scan @zone's unevictable LRU lists to check for pages that have become
3358 * evictable. Move those that have to @zone's inactive list where they
3359 * become candidates for reclaim, unless shrink_inactive_zone() decides
3360 * to reactivate them. Pages that are still unevictable are rotated
3361 * back onto @zone's unevictable list.
3363 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
3364 static void scan_zone_unevictable_pages(struct zone *zone)
3366 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
3368 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
3370 while (nr_to_scan > 0) {
3371 unsigned long batch_size = min(nr_to_scan,
3372 SCAN_UNEVICTABLE_BATCH_SIZE);
3374 spin_lock_irq(&zone->lru_lock);
3375 for (scan = 0; scan < batch_size; scan++) {
3376 struct page *page = lru_to_page(l_unevictable);
3378 if (!trylock_page(page))
3381 prefetchw_prev_lru_page(page, l_unevictable, flags);
3383 if (likely(PageLRU(page) && PageUnevictable(page)))
3384 check_move_unevictable_page(page, zone);
3388 spin_unlock_irq(&zone->lru_lock);
3390 nr_to_scan -= batch_size;
3396 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
3398 * A really big hammer: scan all zones' unevictable LRU lists to check for
3399 * pages that have become evictable. Move those back to the zones'
3400 * inactive list where they become candidates for reclaim.
3401 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
3402 * and we add swap to the system. As such, it runs in the context of a task
3403 * that has possibly/probably made some previously unevictable pages
3406 static void scan_all_zones_unevictable_pages(void)
3410 for_each_zone(zone) {
3411 scan_zone_unevictable_pages(zone);
3416 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3417 * all nodes' unevictable lists for evictable pages
3419 unsigned long scan_unevictable_pages;
3421 int scan_unevictable_handler(struct ctl_table *table, int write,
3422 void __user *buffer,
3423 size_t *length, loff_t *ppos)
3425 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3427 if (write && *(unsigned long *)table->data)
3428 scan_all_zones_unevictable_pages();
3430 scan_unevictable_pages = 0;
3436 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3437 * a specified node's per zone unevictable lists for evictable pages.
3440 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3441 struct sysdev_attribute *attr,
3444 return sprintf(buf, "0\n"); /* always zero; should fit... */
3447 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3448 struct sysdev_attribute *attr,
3449 const char *buf, size_t count)
3451 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3454 unsigned long req = strict_strtoul(buf, 10, &res);
3457 return 1; /* zero is no-op */
3459 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3460 if (!populated_zone(zone))
3462 scan_zone_unevictable_pages(zone);
3468 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3469 read_scan_unevictable_node,
3470 write_scan_unevictable_node);
3472 int scan_unevictable_register_node(struct node *node)
3474 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3477 void scan_unevictable_unregister_node(struct node *node)
3479 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);