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;
255 long batch_size = shrinker->batch ? shrinker->batch
258 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
263 * copy the current shrinker scan count into a local variable
264 * and zero it so that other concurrent shrinker invocations
265 * don't also do this scanning work.
269 } while (cmpxchg(&shrinker->nr, nr, 0) != nr);
272 delta = (4 * nr_pages_scanned) / shrinker->seeks;
274 do_div(delta, lru_pages + 1);
276 if (total_scan < 0) {
277 printk(KERN_ERR "shrink_slab: %pF negative objects to "
279 shrinker->shrink, total_scan);
280 total_scan = max_pass;
284 * We need to avoid excessive windup on filesystem shrinkers
285 * due to large numbers of GFP_NOFS allocations causing the
286 * shrinkers to return -1 all the time. This results in a large
287 * nr being built up so when a shrink that can do some work
288 * comes along it empties the entire cache due to nr >>>
289 * max_pass. This is bad for sustaining a working set in
292 * Hence only allow the shrinker to scan the entire cache when
293 * a large delta change is calculated directly.
295 if (delta < max_pass / 4)
296 total_scan = min(total_scan, max_pass / 2);
299 * Avoid risking looping forever due to too large nr value:
300 * never try to free more than twice the estimate number of
303 if (total_scan > max_pass * 2)
304 total_scan = max_pass * 2;
306 trace_mm_shrink_slab_start(shrinker, shrink, nr,
307 nr_pages_scanned, lru_pages,
308 max_pass, delta, total_scan);
310 while (total_scan >= batch_size) {
313 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
314 shrink_ret = do_shrinker_shrink(shrinker, shrink,
316 if (shrink_ret == -1)
318 if (shrink_ret < nr_before)
319 ret += nr_before - shrink_ret;
320 count_vm_events(SLABS_SCANNED, batch_size);
321 total_scan -= batch_size;
327 * move the unused scan count back into the shrinker in a
328 * manner that handles concurrent updates. If we exhausted the
329 * scan, there is no need to do an update.
333 new_nr = total_scan + nr;
336 } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr);
338 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
340 up_read(&shrinker_rwsem);
346 static void set_reclaim_mode(int priority, struct scan_control *sc,
349 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
352 * Initially assume we are entering either lumpy reclaim or
353 * reclaim/compaction.Depending on the order, we will either set the
354 * sync mode or just reclaim order-0 pages later.
356 if (COMPACTION_BUILD)
357 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
359 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
362 * Avoid using lumpy reclaim or reclaim/compaction if possible by
363 * restricting when its set to either costly allocations or when
364 * under memory pressure
366 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
367 sc->reclaim_mode |= syncmode;
368 else if (sc->order && priority < DEF_PRIORITY - 2)
369 sc->reclaim_mode |= syncmode;
371 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
374 static void reset_reclaim_mode(struct scan_control *sc)
376 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
379 static inline int is_page_cache_freeable(struct page *page)
382 * A freeable page cache page is referenced only by the caller
383 * that isolated the page, the page cache radix tree and
384 * optional buffer heads at page->private.
386 return page_count(page) - page_has_private(page) == 2;
389 static int may_write_to_queue(struct backing_dev_info *bdi,
390 struct scan_control *sc)
392 if (current->flags & PF_SWAPWRITE)
394 if (!bdi_write_congested(bdi))
396 if (bdi == current->backing_dev_info)
399 /* lumpy reclaim for hugepage often need a lot of write */
400 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
406 * We detected a synchronous write error writing a page out. Probably
407 * -ENOSPC. We need to propagate that into the address_space for a subsequent
408 * fsync(), msync() or close().
410 * The tricky part is that after writepage we cannot touch the mapping: nothing
411 * prevents it from being freed up. But we have a ref on the page and once
412 * that page is locked, the mapping is pinned.
414 * We're allowed to run sleeping lock_page() here because we know the caller has
417 static void handle_write_error(struct address_space *mapping,
418 struct page *page, int error)
421 if (page_mapping(page) == mapping)
422 mapping_set_error(mapping, error);
426 /* possible outcome of pageout() */
428 /* failed to write page out, page is locked */
430 /* move page to the active list, page is locked */
432 /* page has been sent to the disk successfully, page is unlocked */
434 /* page is clean and locked */
439 * pageout is called by shrink_page_list() for each dirty page.
440 * Calls ->writepage().
442 static pageout_t pageout(struct page *page, struct address_space *mapping,
443 struct scan_control *sc)
446 * If the page is dirty, only perform writeback if that write
447 * will be non-blocking. To prevent this allocation from being
448 * stalled by pagecache activity. But note that there may be
449 * stalls if we need to run get_block(). We could test
450 * PagePrivate for that.
452 * If this process is currently in __generic_file_aio_write() against
453 * this page's queue, we can perform writeback even if that
456 * If the page is swapcache, write it back even if that would
457 * block, for some throttling. This happens by accident, because
458 * swap_backing_dev_info is bust: it doesn't reflect the
459 * congestion state of the swapdevs. Easy to fix, if needed.
461 if (!is_page_cache_freeable(page))
465 * Some data journaling orphaned pages can have
466 * page->mapping == NULL while being dirty with clean buffers.
468 if (page_has_private(page)) {
469 if (try_to_free_buffers(page)) {
470 ClearPageDirty(page);
471 printk("%s: orphaned page\n", __func__);
477 if (mapping->a_ops->writepage == NULL)
478 return PAGE_ACTIVATE;
479 if (!may_write_to_queue(mapping->backing_dev_info, sc))
482 if (clear_page_dirty_for_io(page)) {
484 struct writeback_control wbc = {
485 .sync_mode = WB_SYNC_NONE,
486 .nr_to_write = SWAP_CLUSTER_MAX,
488 .range_end = LLONG_MAX,
492 SetPageReclaim(page);
493 res = mapping->a_ops->writepage(page, &wbc);
495 handle_write_error(mapping, page, res);
496 if (res == AOP_WRITEPAGE_ACTIVATE) {
497 ClearPageReclaim(page);
498 return PAGE_ACTIVATE;
501 if (!PageWriteback(page)) {
502 /* synchronous write or broken a_ops? */
503 ClearPageReclaim(page);
505 trace_mm_vmscan_writepage(page,
506 trace_reclaim_flags(page, sc->reclaim_mode));
507 inc_zone_page_state(page, NR_VMSCAN_WRITE);
515 * Same as remove_mapping, but if the page is removed from the mapping, it
516 * gets returned with a refcount of 0.
518 static int __remove_mapping(struct address_space *mapping, struct page *page)
520 BUG_ON(!PageLocked(page));
521 BUG_ON(mapping != page_mapping(page));
523 spin_lock_irq(&mapping->tree_lock);
525 * The non racy check for a busy page.
527 * Must be careful with the order of the tests. When someone has
528 * a ref to the page, it may be possible that they dirty it then
529 * drop the reference. So if PageDirty is tested before page_count
530 * here, then the following race may occur:
532 * get_user_pages(&page);
533 * [user mapping goes away]
535 * !PageDirty(page) [good]
536 * SetPageDirty(page);
538 * !page_count(page) [good, discard it]
540 * [oops, our write_to data is lost]
542 * Reversing the order of the tests ensures such a situation cannot
543 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
544 * load is not satisfied before that of page->_count.
546 * Note that if SetPageDirty is always performed via set_page_dirty,
547 * and thus under tree_lock, then this ordering is not required.
549 if (!page_freeze_refs(page, 2))
551 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
552 if (unlikely(PageDirty(page))) {
553 page_unfreeze_refs(page, 2);
557 if (PageSwapCache(page)) {
558 swp_entry_t swap = { .val = page_private(page) };
559 __delete_from_swap_cache(page);
560 spin_unlock_irq(&mapping->tree_lock);
561 swapcache_free(swap, page);
563 void (*freepage)(struct page *);
565 freepage = mapping->a_ops->freepage;
567 __delete_from_page_cache(page);
568 spin_unlock_irq(&mapping->tree_lock);
569 mem_cgroup_uncharge_cache_page(page);
571 if (freepage != NULL)
578 spin_unlock_irq(&mapping->tree_lock);
583 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
584 * someone else has a ref on the page, abort and return 0. If it was
585 * successfully detached, return 1. Assumes the caller has a single ref on
588 int remove_mapping(struct address_space *mapping, struct page *page)
590 if (__remove_mapping(mapping, page)) {
592 * Unfreezing the refcount with 1 rather than 2 effectively
593 * drops the pagecache ref for us without requiring another
596 page_unfreeze_refs(page, 1);
603 * putback_lru_page - put previously isolated page onto appropriate LRU list
604 * @page: page to be put back to appropriate lru list
606 * Add previously isolated @page to appropriate LRU list.
607 * Page may still be unevictable for other reasons.
609 * lru_lock must not be held, interrupts must be enabled.
611 void putback_lru_page(struct page *page)
614 int active = !!TestClearPageActive(page);
615 int was_unevictable = PageUnevictable(page);
617 VM_BUG_ON(PageLRU(page));
620 ClearPageUnevictable(page);
622 if (page_evictable(page, NULL)) {
624 * For evictable pages, we can use the cache.
625 * In event of a race, worst case is we end up with an
626 * unevictable page on [in]active list.
627 * We know how to handle that.
629 lru = active + page_lru_base_type(page);
630 lru_cache_add_lru(page, lru);
633 * Put unevictable pages directly on zone's unevictable
636 lru = LRU_UNEVICTABLE;
637 add_page_to_unevictable_list(page);
639 * When racing with an mlock or AS_UNEVICTABLE clearing
640 * (page is unlocked) make sure that if the other thread
641 * does not observe our setting of PG_lru and fails
642 * isolation/check_move_unevictable_page,
643 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
644 * the page back to the evictable list.
646 * The other side is TestClearPageMlocked() or shmem_lock().
652 * page's status can change while we move it among lru. If an evictable
653 * page is on unevictable list, it never be freed. To avoid that,
654 * check after we added it to the list, again.
656 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
657 if (!isolate_lru_page(page)) {
661 /* This means someone else dropped this page from LRU
662 * So, it will be freed or putback to LRU again. There is
663 * nothing to do here.
667 if (was_unevictable && lru != LRU_UNEVICTABLE)
668 count_vm_event(UNEVICTABLE_PGRESCUED);
669 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
670 count_vm_event(UNEVICTABLE_PGCULLED);
672 put_page(page); /* drop ref from isolate */
675 enum page_references {
677 PAGEREF_RECLAIM_CLEAN,
682 static enum page_references page_check_references(struct page *page,
683 struct scan_control *sc)
685 int referenced_ptes, referenced_page;
686 unsigned long vm_flags;
688 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
689 referenced_page = TestClearPageReferenced(page);
691 /* Lumpy reclaim - ignore references */
692 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
693 return PAGEREF_RECLAIM;
696 * Mlock lost the isolation race with us. Let try_to_unmap()
697 * move the page to the unevictable list.
699 if (vm_flags & VM_LOCKED)
700 return PAGEREF_RECLAIM;
702 if (referenced_ptes) {
704 return PAGEREF_ACTIVATE;
706 * All mapped pages start out with page table
707 * references from the instantiating fault, so we need
708 * to look twice if a mapped file page is used more
711 * Mark it and spare it for another trip around the
712 * inactive list. Another page table reference will
713 * lead to its activation.
715 * Note: the mark is set for activated pages as well
716 * so that recently deactivated but used pages are
719 SetPageReferenced(page);
722 return PAGEREF_ACTIVATE;
727 /* Reclaim if clean, defer dirty pages to writeback */
728 if (referenced_page && !PageSwapBacked(page))
729 return PAGEREF_RECLAIM_CLEAN;
731 return PAGEREF_RECLAIM;
734 static noinline_for_stack void free_page_list(struct list_head *free_pages)
736 struct pagevec freed_pvec;
737 struct page *page, *tmp;
739 pagevec_init(&freed_pvec, 1);
741 list_for_each_entry_safe(page, tmp, free_pages, lru) {
742 list_del(&page->lru);
743 if (!pagevec_add(&freed_pvec, page)) {
744 __pagevec_free(&freed_pvec);
745 pagevec_reinit(&freed_pvec);
749 pagevec_free(&freed_pvec);
753 * shrink_page_list() returns the number of reclaimed pages
755 static unsigned long shrink_page_list(struct list_head *page_list,
757 struct scan_control *sc,
759 unsigned long *ret_nr_dirty,
760 unsigned long *ret_nr_writeback)
762 LIST_HEAD(ret_pages);
763 LIST_HEAD(free_pages);
765 unsigned long nr_dirty = 0;
766 unsigned long nr_congested = 0;
767 unsigned long nr_reclaimed = 0;
768 unsigned long nr_writeback = 0;
772 while (!list_empty(page_list)) {
773 enum page_references references;
774 struct address_space *mapping;
780 page = lru_to_page(page_list);
781 list_del(&page->lru);
783 if (!trylock_page(page))
786 VM_BUG_ON(PageActive(page));
787 VM_BUG_ON(page_zone(page) != zone);
791 if (unlikely(!page_evictable(page, NULL)))
794 if (!sc->may_unmap && page_mapped(page))
797 /* Double the slab pressure for mapped and swapcache pages */
798 if (page_mapped(page) || PageSwapCache(page))
801 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
802 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
804 if (PageWriteback(page)) {
807 * Synchronous reclaim cannot queue pages for
808 * writeback due to the possibility of stack overflow
809 * but if it encounters a page under writeback, wait
810 * for the IO to complete.
812 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
814 wait_on_page_writeback(page);
821 references = page_check_references(page, sc);
822 switch (references) {
823 case PAGEREF_ACTIVATE:
824 goto activate_locked;
827 case PAGEREF_RECLAIM:
828 case PAGEREF_RECLAIM_CLEAN:
829 ; /* try to reclaim the page below */
833 * Anonymous process memory has backing store?
834 * Try to allocate it some swap space here.
836 if (PageAnon(page) && !PageSwapCache(page)) {
837 if (!(sc->gfp_mask & __GFP_IO))
839 if (!add_to_swap(page))
840 goto activate_locked;
844 mapping = page_mapping(page);
847 * The page is mapped into the page tables of one or more
848 * processes. Try to unmap it here.
850 if (page_mapped(page) && mapping) {
851 switch (try_to_unmap(page, TTU_UNMAP)) {
853 goto activate_locked;
859 ; /* try to free the page below */
863 if (PageDirty(page)) {
867 * Only kswapd can writeback filesystem pages to
868 * avoid risk of stack overflow but do not writeback
869 * unless under significant pressure.
871 if (page_is_file_cache(page) &&
872 (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
874 * Immediately reclaim when written back.
875 * Similar in principal to deactivate_page()
876 * except we already have the page isolated
877 * and know it's dirty
879 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
880 SetPageReclaim(page);
885 if (references == PAGEREF_RECLAIM_CLEAN)
889 if (!sc->may_writepage)
892 /* Page is dirty, try to write it out here */
893 switch (pageout(page, mapping, sc)) {
898 goto activate_locked;
900 if (PageWriteback(page))
906 * A synchronous write - probably a ramdisk. Go
907 * ahead and try to reclaim the page.
909 if (!trylock_page(page))
911 if (PageDirty(page) || PageWriteback(page))
913 mapping = page_mapping(page);
915 ; /* try to free the page below */
920 * If the page has buffers, try to free the buffer mappings
921 * associated with this page. If we succeed we try to free
924 * We do this even if the page is PageDirty().
925 * try_to_release_page() does not perform I/O, but it is
926 * possible for a page to have PageDirty set, but it is actually
927 * clean (all its buffers are clean). This happens if the
928 * buffers were written out directly, with submit_bh(). ext3
929 * will do this, as well as the blockdev mapping.
930 * try_to_release_page() will discover that cleanness and will
931 * drop the buffers and mark the page clean - it can be freed.
933 * Rarely, pages can have buffers and no ->mapping. These are
934 * the pages which were not successfully invalidated in
935 * truncate_complete_page(). We try to drop those buffers here
936 * and if that worked, and the page is no longer mapped into
937 * process address space (page_count == 1) it can be freed.
938 * Otherwise, leave the page on the LRU so it is swappable.
940 if (page_has_private(page)) {
941 if (!try_to_release_page(page, sc->gfp_mask))
942 goto activate_locked;
943 if (!mapping && page_count(page) == 1) {
945 if (put_page_testzero(page))
949 * rare race with speculative reference.
950 * the speculative reference will free
951 * this page shortly, so we may
952 * increment nr_reclaimed here (and
953 * leave it off the LRU).
961 if (!mapping || !__remove_mapping(mapping, page))
965 * At this point, we have no other references and there is
966 * no way to pick any more up (removed from LRU, removed
967 * from pagecache). Can use non-atomic bitops now (and
968 * we obviously don't have to worry about waking up a process
969 * waiting on the page lock, because there are no references.
971 __clear_page_locked(page);
976 * Is there need to periodically free_page_list? It would
977 * appear not as the counts should be low
979 list_add(&page->lru, &free_pages);
983 if (PageSwapCache(page))
984 try_to_free_swap(page);
986 putback_lru_page(page);
987 reset_reclaim_mode(sc);
991 /* Not a candidate for swapping, so reclaim swap space. */
992 if (PageSwapCache(page) && vm_swap_full())
993 try_to_free_swap(page);
994 VM_BUG_ON(PageActive(page));
1000 reset_reclaim_mode(sc);
1002 list_add(&page->lru, &ret_pages);
1003 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
1007 * Tag a zone as congested if all the dirty pages encountered were
1008 * backed by a congested BDI. In this case, reclaimers should just
1009 * back off and wait for congestion to clear because further reclaim
1010 * will encounter the same problem
1012 if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
1013 zone_set_flag(zone, ZONE_CONGESTED);
1015 free_page_list(&free_pages);
1017 list_splice(&ret_pages, page_list);
1018 count_vm_events(PGACTIVATE, pgactivate);
1019 *ret_nr_dirty += nr_dirty;
1020 *ret_nr_writeback += nr_writeback;
1021 return nr_reclaimed;
1025 * Attempt to remove the specified page from its LRU. Only take this page
1026 * if it is of the appropriate PageActive status. Pages which are being
1027 * freed elsewhere are also ignored.
1029 * page: page to consider
1030 * mode: one of the LRU isolation modes defined above
1032 * returns 0 on success, -ve errno on failure.
1034 int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
1039 /* Only take pages on the LRU. */
1043 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
1044 (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
1047 * When checking the active state, we need to be sure we are
1048 * dealing with comparible boolean values. Take the logical not
1051 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
1054 if (!all_lru_mode && !!page_is_file_cache(page) != file)
1058 * When this function is being called for lumpy reclaim, we
1059 * initially look into all LRU pages, active, inactive and
1060 * unevictable; only give shrink_page_list evictable pages.
1062 if (PageUnevictable(page))
1067 if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
1070 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1073 if (likely(get_page_unless_zero(page))) {
1075 * Be careful not to clear PageLRU until after we're
1076 * sure the page is not being freed elsewhere -- the
1077 * page release code relies on it.
1087 * zone->lru_lock is heavily contended. Some of the functions that
1088 * shrink the lists perform better by taking out a batch of pages
1089 * and working on them outside the LRU lock.
1091 * For pagecache intensive workloads, this function is the hottest
1092 * spot in the kernel (apart from copy_*_user functions).
1094 * Appropriate locks must be held before calling this function.
1096 * @nr_to_scan: The number of pages to look through on the list.
1097 * @src: The LRU list to pull pages off.
1098 * @dst: The temp list to put pages on to.
1099 * @scanned: The number of pages that were scanned.
1100 * @order: The caller's attempted allocation order
1101 * @mode: One of the LRU isolation modes
1102 * @file: True [1] if isolating file [!anon] pages
1104 * returns how many pages were moved onto *@dst.
1106 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1107 struct list_head *src, struct list_head *dst,
1108 unsigned long *scanned, int order, isolate_mode_t mode,
1111 unsigned long nr_taken = 0;
1112 unsigned long nr_lumpy_taken = 0;
1113 unsigned long nr_lumpy_dirty = 0;
1114 unsigned long nr_lumpy_failed = 0;
1117 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1120 unsigned long end_pfn;
1121 unsigned long page_pfn;
1124 page = lru_to_page(src);
1125 prefetchw_prev_lru_page(page, src, flags);
1127 VM_BUG_ON(!PageLRU(page));
1129 switch (__isolate_lru_page(page, mode, file)) {
1131 list_move(&page->lru, dst);
1132 mem_cgroup_del_lru(page);
1133 nr_taken += hpage_nr_pages(page);
1137 /* else it is being freed elsewhere */
1138 list_move(&page->lru, src);
1139 mem_cgroup_rotate_lru_list(page, page_lru(page));
1150 * Attempt to take all pages in the order aligned region
1151 * surrounding the tag page. Only take those pages of
1152 * the same active state as that tag page. We may safely
1153 * round the target page pfn down to the requested order
1154 * as the mem_map is guaranteed valid out to MAX_ORDER,
1155 * where that page is in a different zone we will detect
1156 * it from its zone id and abort this block scan.
1158 zone_id = page_zone_id(page);
1159 page_pfn = page_to_pfn(page);
1160 pfn = page_pfn & ~((1 << order) - 1);
1161 end_pfn = pfn + (1 << order);
1162 for (; pfn < end_pfn; pfn++) {
1163 struct page *cursor_page;
1165 /* The target page is in the block, ignore it. */
1166 if (unlikely(pfn == page_pfn))
1169 /* Avoid holes within the zone. */
1170 if (unlikely(!pfn_valid_within(pfn)))
1173 cursor_page = pfn_to_page(pfn);
1175 /* Check that we have not crossed a zone boundary. */
1176 if (unlikely(page_zone_id(cursor_page) != zone_id))
1180 * If we don't have enough swap space, reclaiming of
1181 * anon page which don't already have a swap slot is
1184 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1185 !PageSwapCache(cursor_page))
1188 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1189 list_move(&cursor_page->lru, dst);
1190 mem_cgroup_del_lru(cursor_page);
1191 nr_taken += hpage_nr_pages(page);
1193 if (PageDirty(cursor_page))
1198 * Check if the page is freed already.
1200 * We can't use page_count() as that
1201 * requires compound_head and we don't
1202 * have a pin on the page here. If a
1203 * page is tail, we may or may not
1204 * have isolated the head, so assume
1205 * it's not free, it'd be tricky to
1206 * track the head status without a
1209 if (!PageTail(cursor_page) &&
1210 !atomic_read(&cursor_page->_count))
1216 /* If we break out of the loop above, lumpy reclaim failed */
1223 trace_mm_vmscan_lru_isolate(order,
1226 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1231 static unsigned long isolate_pages_global(unsigned long nr,
1232 struct list_head *dst,
1233 unsigned long *scanned, int order,
1234 isolate_mode_t mode,
1235 struct zone *z, int active, int file)
1242 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1247 * clear_active_flags() is a helper for shrink_active_list(), clearing
1248 * any active bits from the pages in the list.
1250 static unsigned long clear_active_flags(struct list_head *page_list,
1251 unsigned int *count)
1257 list_for_each_entry(page, page_list, lru) {
1258 int numpages = hpage_nr_pages(page);
1259 lru = page_lru_base_type(page);
1260 if (PageActive(page)) {
1262 ClearPageActive(page);
1263 nr_active += numpages;
1266 count[lru] += numpages;
1273 * isolate_lru_page - tries to isolate a page from its LRU list
1274 * @page: page to isolate from its LRU list
1276 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1277 * vmstat statistic corresponding to whatever LRU list the page was on.
1279 * Returns 0 if the page was removed from an LRU list.
1280 * Returns -EBUSY if the page was not on an LRU list.
1282 * The returned page will have PageLRU() cleared. If it was found on
1283 * the active list, it will have PageActive set. If it was found on
1284 * the unevictable list, it will have the PageUnevictable bit set. That flag
1285 * may need to be cleared by the caller before letting the page go.
1287 * The vmstat statistic corresponding to the list on which the page was
1288 * found will be decremented.
1291 * (1) Must be called with an elevated refcount on the page. This is a
1292 * fundamentnal difference from isolate_lru_pages (which is called
1293 * without a stable reference).
1294 * (2) the lru_lock must not be held.
1295 * (3) interrupts must be enabled.
1297 int isolate_lru_page(struct page *page)
1301 VM_BUG_ON(!page_count(page));
1303 if (PageLRU(page)) {
1304 struct zone *zone = page_zone(page);
1306 spin_lock_irq(&zone->lru_lock);
1307 if (PageLRU(page)) {
1308 int lru = page_lru(page);
1313 del_page_from_lru_list(zone, page, lru);
1315 spin_unlock_irq(&zone->lru_lock);
1321 * Are there way too many processes in the direct reclaim path already?
1323 static int too_many_isolated(struct zone *zone, int file,
1324 struct scan_control *sc)
1326 unsigned long inactive, isolated;
1328 if (current_is_kswapd())
1331 if (!scanning_global_lru(sc))
1335 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1336 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1338 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1339 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1342 return isolated > inactive;
1346 * TODO: Try merging with migrations version of putback_lru_pages
1348 static noinline_for_stack void
1349 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1350 unsigned long nr_anon, unsigned long nr_file,
1351 struct list_head *page_list)
1354 struct pagevec pvec;
1355 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1357 pagevec_init(&pvec, 1);
1360 * Put back any unfreeable pages.
1362 spin_lock(&zone->lru_lock);
1363 while (!list_empty(page_list)) {
1365 page = lru_to_page(page_list);
1366 VM_BUG_ON(PageLRU(page));
1367 list_del(&page->lru);
1368 if (unlikely(!page_evictable(page, NULL))) {
1369 spin_unlock_irq(&zone->lru_lock);
1370 putback_lru_page(page);
1371 spin_lock_irq(&zone->lru_lock);
1375 lru = page_lru(page);
1376 add_page_to_lru_list(zone, page, lru);
1377 if (is_active_lru(lru)) {
1378 int file = is_file_lru(lru);
1379 int numpages = hpage_nr_pages(page);
1380 reclaim_stat->recent_rotated[file] += numpages;
1382 if (!pagevec_add(&pvec, page)) {
1383 spin_unlock_irq(&zone->lru_lock);
1384 __pagevec_release(&pvec);
1385 spin_lock_irq(&zone->lru_lock);
1388 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1389 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1391 spin_unlock_irq(&zone->lru_lock);
1392 pagevec_release(&pvec);
1395 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1396 struct scan_control *sc,
1397 unsigned long *nr_anon,
1398 unsigned long *nr_file,
1399 struct list_head *isolated_list)
1401 unsigned long nr_active;
1402 unsigned int count[NR_LRU_LISTS] = { 0, };
1403 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1405 nr_active = clear_active_flags(isolated_list, count);
1406 __count_vm_events(PGDEACTIVATE, nr_active);
1408 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1409 -count[LRU_ACTIVE_FILE]);
1410 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1411 -count[LRU_INACTIVE_FILE]);
1412 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1413 -count[LRU_ACTIVE_ANON]);
1414 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1415 -count[LRU_INACTIVE_ANON]);
1417 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1418 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1419 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1420 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1422 reclaim_stat->recent_scanned[0] += *nr_anon;
1423 reclaim_stat->recent_scanned[1] += *nr_file;
1427 * Returns true if a direct reclaim should wait on pages under writeback.
1429 * If we are direct reclaiming for contiguous pages and we do not reclaim
1430 * everything in the list, try again and wait for writeback IO to complete.
1431 * This will stall high-order allocations noticeably. Only do that when really
1432 * need to free the pages under high memory pressure.
1434 static inline bool should_reclaim_stall(unsigned long nr_taken,
1435 unsigned long nr_freed,
1437 struct scan_control *sc)
1439 int lumpy_stall_priority;
1441 /* kswapd should not stall on sync IO */
1442 if (current_is_kswapd())
1445 /* Only stall on lumpy reclaim */
1446 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1449 /* If we have reclaimed everything on the isolated list, no stall */
1450 if (nr_freed == nr_taken)
1454 * For high-order allocations, there are two stall thresholds.
1455 * High-cost allocations stall immediately where as lower
1456 * order allocations such as stacks require the scanning
1457 * priority to be much higher before stalling.
1459 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1460 lumpy_stall_priority = DEF_PRIORITY;
1462 lumpy_stall_priority = DEF_PRIORITY / 3;
1464 return priority <= lumpy_stall_priority;
1468 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1469 * of reclaimed pages
1471 static noinline_for_stack unsigned long
1472 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1473 struct scan_control *sc, int priority, int file)
1475 LIST_HEAD(page_list);
1476 unsigned long nr_scanned;
1477 unsigned long nr_reclaimed = 0;
1478 unsigned long nr_taken;
1479 unsigned long nr_anon;
1480 unsigned long nr_file;
1481 unsigned long nr_dirty = 0;
1482 unsigned long nr_writeback = 0;
1483 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1485 while (unlikely(too_many_isolated(zone, file, sc))) {
1486 congestion_wait(BLK_RW_ASYNC, HZ/10);
1488 /* We are about to die and free our memory. Return now. */
1489 if (fatal_signal_pending(current))
1490 return SWAP_CLUSTER_MAX;
1493 set_reclaim_mode(priority, sc, false);
1494 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
1495 reclaim_mode |= ISOLATE_ACTIVE;
1500 reclaim_mode |= ISOLATE_UNMAPPED;
1501 if (!sc->may_writepage)
1502 reclaim_mode |= ISOLATE_CLEAN;
1504 spin_lock_irq(&zone->lru_lock);
1506 if (scanning_global_lru(sc)) {
1507 nr_taken = isolate_pages_global(nr_to_scan, &page_list,
1508 &nr_scanned, sc->order, reclaim_mode, zone, 0, file);
1509 zone->pages_scanned += nr_scanned;
1510 if (current_is_kswapd())
1511 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1514 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1517 nr_taken = mem_cgroup_isolate_pages(nr_to_scan, &page_list,
1518 &nr_scanned, sc->order, reclaim_mode, zone,
1519 sc->mem_cgroup, 0, file);
1521 * mem_cgroup_isolate_pages() keeps track of
1522 * scanned pages on its own.
1526 if (nr_taken == 0) {
1527 spin_unlock_irq(&zone->lru_lock);
1531 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1533 spin_unlock_irq(&zone->lru_lock);
1535 nr_reclaimed = shrink_page_list(&page_list, zone, sc, priority,
1536 &nr_dirty, &nr_writeback);
1538 /* Check if we should syncronously wait for writeback */
1539 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1540 set_reclaim_mode(priority, sc, true);
1541 nr_reclaimed += shrink_page_list(&page_list, zone, sc,
1542 priority, &nr_dirty, &nr_writeback);
1545 local_irq_disable();
1546 if (current_is_kswapd())
1547 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1548 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1550 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1553 * If reclaim is isolating dirty pages under writeback, it implies
1554 * that the long-lived page allocation rate is exceeding the page
1555 * laundering rate. Either the global limits are not being effective
1556 * at throttling processes due to the page distribution throughout
1557 * zones or there is heavy usage of a slow backing device. The
1558 * only option is to throttle from reclaim context which is not ideal
1559 * as there is no guarantee the dirtying process is throttled in the
1560 * same way balance_dirty_pages() manages.
1562 * This scales the number of dirty pages that must be under writeback
1563 * before throttling depending on priority. It is a simple backoff
1564 * function that has the most effect in the range DEF_PRIORITY to
1565 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1566 * in trouble and reclaim is considered to be in trouble.
1568 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1569 * DEF_PRIORITY-1 50% must be PageWriteback
1570 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1572 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1573 * isolated page is PageWriteback
1575 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
1576 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1578 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1580 nr_scanned, nr_reclaimed,
1582 trace_shrink_flags(file, sc->reclaim_mode));
1583 return nr_reclaimed;
1587 * This moves pages from the active list to the inactive list.
1589 * We move them the other way if the page is referenced by one or more
1590 * processes, from rmap.
1592 * If the pages are mostly unmapped, the processing is fast and it is
1593 * appropriate to hold zone->lru_lock across the whole operation. But if
1594 * the pages are mapped, the processing is slow (page_referenced()) so we
1595 * should drop zone->lru_lock around each page. It's impossible to balance
1596 * this, so instead we remove the pages from the LRU while processing them.
1597 * It is safe to rely on PG_active against the non-LRU pages in here because
1598 * nobody will play with that bit on a non-LRU page.
1600 * The downside is that we have to touch page->_count against each page.
1601 * But we had to alter page->flags anyway.
1604 static void move_active_pages_to_lru(struct zone *zone,
1605 struct list_head *list,
1608 unsigned long pgmoved = 0;
1609 struct pagevec pvec;
1612 pagevec_init(&pvec, 1);
1614 while (!list_empty(list)) {
1615 page = lru_to_page(list);
1617 VM_BUG_ON(PageLRU(page));
1620 list_move(&page->lru, &zone->lru[lru].list);
1621 mem_cgroup_add_lru_list(page, lru);
1622 pgmoved += hpage_nr_pages(page);
1624 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1625 spin_unlock_irq(&zone->lru_lock);
1626 if (buffer_heads_over_limit)
1627 pagevec_strip(&pvec);
1628 __pagevec_release(&pvec);
1629 spin_lock_irq(&zone->lru_lock);
1632 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1633 if (!is_active_lru(lru))
1634 __count_vm_events(PGDEACTIVATE, pgmoved);
1637 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1638 struct scan_control *sc, int priority, int file)
1640 unsigned long nr_taken;
1641 unsigned long pgscanned;
1642 unsigned long vm_flags;
1643 LIST_HEAD(l_hold); /* The pages which were snipped off */
1644 LIST_HEAD(l_active);
1645 LIST_HEAD(l_inactive);
1647 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1648 unsigned long nr_rotated = 0;
1649 isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
1654 reclaim_mode |= ISOLATE_UNMAPPED;
1655 if (!sc->may_writepage)
1656 reclaim_mode |= ISOLATE_CLEAN;
1658 spin_lock_irq(&zone->lru_lock);
1659 if (scanning_global_lru(sc)) {
1660 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1661 &pgscanned, sc->order,
1664 zone->pages_scanned += pgscanned;
1666 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1667 &pgscanned, sc->order,
1669 sc->mem_cgroup, 1, file);
1671 * mem_cgroup_isolate_pages() keeps track of
1672 * scanned pages on its own.
1676 reclaim_stat->recent_scanned[file] += nr_taken;
1678 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1680 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1682 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1683 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1684 spin_unlock_irq(&zone->lru_lock);
1686 while (!list_empty(&l_hold)) {
1688 page = lru_to_page(&l_hold);
1689 list_del(&page->lru);
1691 if (unlikely(!page_evictable(page, NULL))) {
1692 putback_lru_page(page);
1696 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1697 nr_rotated += hpage_nr_pages(page);
1699 * Identify referenced, file-backed active pages and
1700 * give them one more trip around the active list. So
1701 * that executable code get better chances to stay in
1702 * memory under moderate memory pressure. Anon pages
1703 * are not likely to be evicted by use-once streaming
1704 * IO, plus JVM can create lots of anon VM_EXEC pages,
1705 * so we ignore them here.
1707 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1708 list_add(&page->lru, &l_active);
1713 ClearPageActive(page); /* we are de-activating */
1714 list_add(&page->lru, &l_inactive);
1718 * Move pages back to the lru list.
1720 spin_lock_irq(&zone->lru_lock);
1722 * Count referenced pages from currently used mappings as rotated,
1723 * even though only some of them are actually re-activated. This
1724 * helps balance scan pressure between file and anonymous pages in
1727 reclaim_stat->recent_rotated[file] += nr_rotated;
1729 move_active_pages_to_lru(zone, &l_active,
1730 LRU_ACTIVE + file * LRU_FILE);
1731 move_active_pages_to_lru(zone, &l_inactive,
1732 LRU_BASE + file * LRU_FILE);
1733 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1734 spin_unlock_irq(&zone->lru_lock);
1738 static int inactive_anon_is_low_global(struct zone *zone)
1740 unsigned long active, inactive;
1742 active = zone_page_state(zone, NR_ACTIVE_ANON);
1743 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1745 if (inactive * zone->inactive_ratio < active)
1752 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1753 * @zone: zone to check
1754 * @sc: scan control of this context
1756 * Returns true if the zone does not have enough inactive anon pages,
1757 * meaning some active anon pages need to be deactivated.
1759 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1764 * If we don't have swap space, anonymous page deactivation
1767 if (!total_swap_pages)
1770 if (scanning_global_lru(sc))
1771 low = inactive_anon_is_low_global(zone);
1773 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup, zone);
1777 static inline int inactive_anon_is_low(struct zone *zone,
1778 struct scan_control *sc)
1784 static int inactive_file_is_low_global(struct zone *zone)
1786 unsigned long active, inactive;
1788 active = zone_page_state(zone, NR_ACTIVE_FILE);
1789 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1791 return (active > inactive);
1795 * inactive_file_is_low - check if file pages need to be deactivated
1796 * @zone: zone to check
1797 * @sc: scan control of this context
1799 * When the system is doing streaming IO, memory pressure here
1800 * ensures that active file pages get deactivated, until more
1801 * than half of the file pages are on the inactive list.
1803 * Once we get to that situation, protect the system's working
1804 * set from being evicted by disabling active file page aging.
1806 * This uses a different ratio than the anonymous pages, because
1807 * the page cache uses a use-once replacement algorithm.
1809 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1813 if (scanning_global_lru(sc))
1814 low = inactive_file_is_low_global(zone);
1816 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup, zone);
1820 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1824 return inactive_file_is_low(zone, sc);
1826 return inactive_anon_is_low(zone, sc);
1829 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1830 struct zone *zone, struct scan_control *sc, int priority)
1832 int file = is_file_lru(lru);
1834 if (is_active_lru(lru)) {
1835 if (inactive_list_is_low(zone, sc, file))
1836 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1840 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1843 static int vmscan_swappiness(struct scan_control *sc)
1845 if (scanning_global_lru(sc))
1846 return vm_swappiness;
1847 return mem_cgroup_swappiness(sc->mem_cgroup);
1851 * Determine how aggressively the anon and file LRU lists should be
1852 * scanned. The relative value of each set of LRU lists is determined
1853 * by looking at the fraction of the pages scanned we did rotate back
1854 * onto the active list instead of evict.
1856 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1858 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1859 unsigned long *nr, int priority)
1861 unsigned long anon, file, free;
1862 unsigned long anon_prio, file_prio;
1863 unsigned long ap, fp;
1864 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1865 u64 fraction[2], denominator;
1868 bool force_scan = false;
1871 * If the zone or memcg is small, nr[l] can be 0. This
1872 * results in no scanning on this priority and a potential
1873 * priority drop. Global direct reclaim can go to the next
1874 * zone and tends to have no problems. Global kswapd is for
1875 * zone balancing and it needs to scan a minimum amount. When
1876 * reclaiming for a memcg, a priority drop can cause high
1877 * latencies, so it's better to scan a minimum amount there as
1880 if (scanning_global_lru(sc) && current_is_kswapd())
1882 if (!scanning_global_lru(sc))
1885 /* If we have no swap space, do not bother scanning anon pages. */
1886 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1894 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1895 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1896 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1897 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1899 if (scanning_global_lru(sc)) {
1900 free = zone_page_state(zone, NR_FREE_PAGES);
1901 /* If we have very few page cache pages,
1902 force-scan anon pages. */
1903 if (unlikely(file + free <= high_wmark_pages(zone))) {
1912 * With swappiness at 100, anonymous and file have the same priority.
1913 * This scanning priority is essentially the inverse of IO cost.
1915 anon_prio = vmscan_swappiness(sc);
1916 file_prio = 200 - vmscan_swappiness(sc);
1919 * OK, so we have swap space and a fair amount of page cache
1920 * pages. We use the recently rotated / recently scanned
1921 * ratios to determine how valuable each cache is.
1923 * Because workloads change over time (and to avoid overflow)
1924 * we keep these statistics as a floating average, which ends
1925 * up weighing recent references more than old ones.
1927 * anon in [0], file in [1]
1929 spin_lock_irq(&zone->lru_lock);
1930 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1931 reclaim_stat->recent_scanned[0] /= 2;
1932 reclaim_stat->recent_rotated[0] /= 2;
1935 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1936 reclaim_stat->recent_scanned[1] /= 2;
1937 reclaim_stat->recent_rotated[1] /= 2;
1941 * The amount of pressure on anon vs file pages is inversely
1942 * proportional to the fraction of recently scanned pages on
1943 * each list that were recently referenced and in active use.
1945 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1946 ap /= reclaim_stat->recent_rotated[0] + 1;
1948 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1949 fp /= reclaim_stat->recent_rotated[1] + 1;
1950 spin_unlock_irq(&zone->lru_lock);
1954 denominator = ap + fp + 1;
1956 for_each_evictable_lru(l) {
1957 int file = is_file_lru(l);
1960 scan = zone_nr_lru_pages(zone, sc, l);
1961 if (priority || noswap) {
1963 if (!scan && force_scan)
1964 scan = SWAP_CLUSTER_MAX;
1965 scan = div64_u64(scan * fraction[file], denominator);
1972 * Reclaim/compaction depends on a number of pages being freed. To avoid
1973 * disruption to the system, a small number of order-0 pages continue to be
1974 * rotated and reclaimed in the normal fashion. However, by the time we get
1975 * back to the allocator and call try_to_compact_zone(), we ensure that
1976 * there are enough free pages for it to be likely successful
1978 static inline bool should_continue_reclaim(struct zone *zone,
1979 unsigned long nr_reclaimed,
1980 unsigned long nr_scanned,
1981 struct scan_control *sc)
1983 unsigned long pages_for_compaction;
1984 unsigned long inactive_lru_pages;
1986 /* If not in reclaim/compaction mode, stop */
1987 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1990 /* Consider stopping depending on scan and reclaim activity */
1991 if (sc->gfp_mask & __GFP_REPEAT) {
1993 * For __GFP_REPEAT allocations, stop reclaiming if the
1994 * full LRU list has been scanned and we are still failing
1995 * to reclaim pages. This full LRU scan is potentially
1996 * expensive but a __GFP_REPEAT caller really wants to succeed
1998 if (!nr_reclaimed && !nr_scanned)
2002 * For non-__GFP_REPEAT allocations which can presumably
2003 * fail without consequence, stop if we failed to reclaim
2004 * any pages from the last SWAP_CLUSTER_MAX number of
2005 * pages that were scanned. This will return to the
2006 * caller faster at the risk reclaim/compaction and
2007 * the resulting allocation attempt fails
2014 * If we have not reclaimed enough pages for compaction and the
2015 * inactive lists are large enough, continue reclaiming
2017 pages_for_compaction = (2UL << sc->order);
2018 inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) +
2019 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
2020 if (sc->nr_reclaimed < pages_for_compaction &&
2021 inactive_lru_pages > pages_for_compaction)
2024 /* If compaction would go ahead or the allocation would succeed, stop */
2025 switch (compaction_suitable(zone, sc->order)) {
2026 case COMPACT_PARTIAL:
2027 case COMPACT_CONTINUE:
2035 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2037 static void shrink_zone(int priority, struct zone *zone,
2038 struct scan_control *sc)
2040 unsigned long nr[NR_LRU_LISTS];
2041 unsigned long nr_to_scan;
2043 unsigned long nr_reclaimed, nr_scanned;
2044 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2045 struct blk_plug plug;
2049 nr_scanned = sc->nr_scanned;
2050 get_scan_count(zone, sc, nr, priority);
2052 blk_start_plug(&plug);
2053 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2054 nr[LRU_INACTIVE_FILE]) {
2055 for_each_evictable_lru(l) {
2057 nr_to_scan = min_t(unsigned long,
2058 nr[l], SWAP_CLUSTER_MAX);
2059 nr[l] -= nr_to_scan;
2061 nr_reclaimed += shrink_list(l, nr_to_scan,
2062 zone, sc, priority);
2066 * On large memory systems, scan >> priority can become
2067 * really large. This is fine for the starting priority;
2068 * we want to put equal scanning pressure on each zone.
2069 * However, if the VM has a harder time of freeing pages,
2070 * with multiple processes reclaiming pages, the total
2071 * freeing target can get unreasonably large.
2073 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2076 blk_finish_plug(&plug);
2077 sc->nr_reclaimed += nr_reclaimed;
2080 * Even if we did not try to evict anon pages at all, we want to
2081 * rebalance the anon lru active/inactive ratio.
2083 if (inactive_anon_is_low(zone, sc))
2084 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
2086 /* reclaim/compaction might need reclaim to continue */
2087 if (should_continue_reclaim(zone, nr_reclaimed,
2088 sc->nr_scanned - nr_scanned, sc))
2091 throttle_vm_writeout(sc->gfp_mask);
2095 * This is the direct reclaim path, for page-allocating processes. We only
2096 * try to reclaim pages from zones which will satisfy the caller's allocation
2099 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2101 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2103 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2104 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2105 * zone defense algorithm.
2107 * If a zone is deemed to be full of pinned pages then just give it a light
2108 * scan then give up on it.
2110 * This function returns true if a zone is being reclaimed for a costly
2111 * high-order allocation and compaction is either ready to begin or deferred.
2112 * This indicates to the caller that it should retry the allocation or fail.
2114 static bool shrink_zones(int priority, struct zonelist *zonelist,
2115 struct scan_control *sc)
2119 unsigned long nr_soft_reclaimed;
2120 unsigned long nr_soft_scanned;
2121 bool should_abort_reclaim = false;
2123 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2124 gfp_zone(sc->gfp_mask), sc->nodemask) {
2125 if (!populated_zone(zone))
2128 * Take care memory controller reclaiming has small influence
2131 if (scanning_global_lru(sc)) {
2132 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2134 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2135 continue; /* Let kswapd poll it */
2136 if (COMPACTION_BUILD) {
2138 * If we already have plenty of memory free for
2139 * compaction in this zone, don't free any more.
2140 * Even though compaction is invoked for any
2141 * non-zero order, only frequent costly order
2142 * reclamation is disruptive enough to become a
2143 * noticable problem, like transparent huge page
2146 if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
2147 (compaction_suitable(zone, sc->order) ||
2148 compaction_deferred(zone))) {
2149 should_abort_reclaim = true;
2154 * This steals pages from memory cgroups over softlimit
2155 * and returns the number of reclaimed pages and
2156 * scanned pages. This works for global memory pressure
2157 * and balancing, not for a memcg's limit.
2159 nr_soft_scanned = 0;
2160 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2161 sc->order, sc->gfp_mask,
2163 sc->nr_reclaimed += nr_soft_reclaimed;
2164 sc->nr_scanned += nr_soft_scanned;
2165 /* need some check for avoid more shrink_zone() */
2168 shrink_zone(priority, zone, sc);
2171 return should_abort_reclaim;
2174 static bool zone_reclaimable(struct zone *zone)
2176 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2179 /* All zones in zonelist are unreclaimable? */
2180 static bool all_unreclaimable(struct zonelist *zonelist,
2181 struct scan_control *sc)
2186 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2187 gfp_zone(sc->gfp_mask), sc->nodemask) {
2188 if (!populated_zone(zone))
2190 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2192 if (!zone->all_unreclaimable)
2200 * This is the main entry point to direct page reclaim.
2202 * If a full scan of the inactive list fails to free enough memory then we
2203 * are "out of memory" and something needs to be killed.
2205 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2206 * high - the zone may be full of dirty or under-writeback pages, which this
2207 * caller can't do much about. We kick the writeback threads and take explicit
2208 * naps in the hope that some of these pages can be written. But if the
2209 * allocating task holds filesystem locks which prevent writeout this might not
2210 * work, and the allocation attempt will fail.
2212 * returns: 0, if no pages reclaimed
2213 * else, the number of pages reclaimed
2215 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2216 struct scan_control *sc,
2217 struct shrink_control *shrink)
2220 unsigned long total_scanned = 0;
2221 struct reclaim_state *reclaim_state = current->reclaim_state;
2224 unsigned long writeback_threshold;
2227 delayacct_freepages_start();
2229 if (scanning_global_lru(sc))
2230 count_vm_event(ALLOCSTALL);
2232 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2235 disable_swap_token(sc->mem_cgroup);
2236 if (shrink_zones(priority, zonelist, sc))
2240 * Don't shrink slabs when reclaiming memory from
2241 * over limit cgroups
2243 if (scanning_global_lru(sc)) {
2244 unsigned long lru_pages = 0;
2245 for_each_zone_zonelist(zone, z, zonelist,
2246 gfp_zone(sc->gfp_mask)) {
2247 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2250 lru_pages += zone_reclaimable_pages(zone);
2253 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2254 if (reclaim_state) {
2255 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2256 reclaim_state->reclaimed_slab = 0;
2259 total_scanned += sc->nr_scanned;
2260 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2264 * Try to write back as many pages as we just scanned. This
2265 * tends to cause slow streaming writers to write data to the
2266 * disk smoothly, at the dirtying rate, which is nice. But
2267 * that's undesirable in laptop mode, where we *want* lumpy
2268 * writeout. So in laptop mode, write out the whole world.
2270 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2271 if (total_scanned > writeback_threshold) {
2272 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2273 WB_REASON_TRY_TO_FREE_PAGES);
2274 sc->may_writepage = 1;
2277 /* Take a nap, wait for some writeback to complete */
2278 if (!sc->hibernation_mode && sc->nr_scanned &&
2279 priority < DEF_PRIORITY - 2) {
2280 struct zone *preferred_zone;
2282 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2283 &cpuset_current_mems_allowed,
2285 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2290 delayacct_freepages_end();
2293 if (sc->nr_reclaimed)
2294 return sc->nr_reclaimed;
2297 * As hibernation is going on, kswapd is freezed so that it can't mark
2298 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2301 if (oom_killer_disabled)
2304 /* top priority shrink_zones still had more to do? don't OOM, then */
2305 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
2311 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2312 gfp_t gfp_mask, nodemask_t *nodemask)
2314 unsigned long nr_reclaimed;
2315 struct scan_control sc = {
2316 .gfp_mask = gfp_mask,
2317 .may_writepage = !laptop_mode,
2318 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2323 .nodemask = nodemask,
2325 struct shrink_control shrink = {
2326 .gfp_mask = sc.gfp_mask,
2329 trace_mm_vmscan_direct_reclaim_begin(order,
2333 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2335 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2337 return nr_reclaimed;
2340 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2342 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2343 gfp_t gfp_mask, bool noswap,
2345 unsigned long *nr_scanned)
2347 struct scan_control sc = {
2349 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2350 .may_writepage = !laptop_mode,
2352 .may_swap = !noswap,
2357 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2358 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2360 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2365 * NOTE: Although we can get the priority field, using it
2366 * here is not a good idea, since it limits the pages we can scan.
2367 * if we don't reclaim here, the shrink_zone from balance_pgdat
2368 * will pick up pages from other mem cgroup's as well. We hack
2369 * the priority and make it zero.
2371 shrink_zone(0, zone, &sc);
2373 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2375 *nr_scanned = sc.nr_scanned;
2376 return sc.nr_reclaimed;
2379 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2383 struct zonelist *zonelist;
2384 unsigned long nr_reclaimed;
2386 struct scan_control sc = {
2387 .may_writepage = !laptop_mode,
2389 .may_swap = !noswap,
2390 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2392 .mem_cgroup = mem_cont,
2393 .nodemask = NULL, /* we don't care the placement */
2394 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2395 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2397 struct shrink_control shrink = {
2398 .gfp_mask = sc.gfp_mask,
2402 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2403 * take care of from where we get pages. So the node where we start the
2404 * scan does not need to be the current node.
2406 nid = mem_cgroup_select_victim_node(mem_cont);
2408 zonelist = NODE_DATA(nid)->node_zonelists;
2410 trace_mm_vmscan_memcg_reclaim_begin(0,
2414 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2416 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2418 return nr_reclaimed;
2423 * pgdat_balanced is used when checking if a node is balanced for high-order
2424 * allocations. Only zones that meet watermarks and are in a zone allowed
2425 * by the callers classzone_idx are added to balanced_pages. The total of
2426 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2427 * for the node to be considered balanced. Forcing all zones to be balanced
2428 * for high orders can cause excessive reclaim when there are imbalanced zones.
2429 * The choice of 25% is due to
2430 * o a 16M DMA zone that is balanced will not balance a zone on any
2431 * reasonable sized machine
2432 * o On all other machines, the top zone must be at least a reasonable
2433 * percentage of the middle zones. For example, on 32-bit x86, highmem
2434 * would need to be at least 256M for it to be balance a whole node.
2435 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2436 * to balance a node on its own. These seemed like reasonable ratios.
2438 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2441 unsigned long present_pages = 0;
2444 for (i = 0; i <= classzone_idx; i++)
2445 present_pages += pgdat->node_zones[i].present_pages;
2447 /* A special case here: if zone has no page, we think it's balanced */
2448 return balanced_pages >= (present_pages >> 2);
2451 /* is kswapd sleeping prematurely? */
2452 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2456 unsigned long balanced = 0;
2457 bool all_zones_ok = true;
2459 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2463 /* Check the watermark levels */
2464 for (i = 0; i <= classzone_idx; i++) {
2465 struct zone *zone = pgdat->node_zones + i;
2467 if (!populated_zone(zone))
2471 * balance_pgdat() skips over all_unreclaimable after
2472 * DEF_PRIORITY. Effectively, it considers them balanced so
2473 * they must be considered balanced here as well if kswapd
2476 if (zone->all_unreclaimable) {
2477 balanced += zone->present_pages;
2481 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2483 all_zones_ok = false;
2485 balanced += zone->present_pages;
2489 * For high-order requests, the balanced zones must contain at least
2490 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2494 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2496 return !all_zones_ok;
2500 * For kswapd, balance_pgdat() will work across all this node's zones until
2501 * they are all at high_wmark_pages(zone).
2503 * Returns the final order kswapd was reclaiming at
2505 * There is special handling here for zones which are full of pinned pages.
2506 * This can happen if the pages are all mlocked, or if they are all used by
2507 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2508 * What we do is to detect the case where all pages in the zone have been
2509 * scanned twice and there has been zero successful reclaim. Mark the zone as
2510 * dead and from now on, only perform a short scan. Basically we're polling
2511 * the zone for when the problem goes away.
2513 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2514 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2515 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2516 * lower zones regardless of the number of free pages in the lower zones. This
2517 * interoperates with the page allocator fallback scheme to ensure that aging
2518 * of pages is balanced across the zones.
2520 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2524 unsigned long balanced;
2527 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2528 unsigned long total_scanned;
2529 struct reclaim_state *reclaim_state = current->reclaim_state;
2530 unsigned long nr_soft_reclaimed;
2531 unsigned long nr_soft_scanned;
2532 struct scan_control sc = {
2533 .gfp_mask = GFP_KERNEL,
2537 * kswapd doesn't want to be bailed out while reclaim. because
2538 * we want to put equal scanning pressure on each zone.
2540 .nr_to_reclaim = ULONG_MAX,
2544 struct shrink_control shrink = {
2545 .gfp_mask = sc.gfp_mask,
2549 sc.nr_reclaimed = 0;
2550 sc.may_writepage = !laptop_mode;
2551 count_vm_event(PAGEOUTRUN);
2553 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2554 unsigned long lru_pages = 0;
2555 int has_under_min_watermark_zone = 0;
2557 /* The swap token gets in the way of swapout... */
2559 disable_swap_token(NULL);
2565 * Scan in the highmem->dma direction for the highest
2566 * zone which needs scanning
2568 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2569 struct zone *zone = pgdat->node_zones + i;
2571 if (!populated_zone(zone))
2574 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2578 * Do some background aging of the anon list, to give
2579 * pages a chance to be referenced before reclaiming.
2581 if (inactive_anon_is_low(zone, &sc))
2582 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2585 if (!zone_watermark_ok_safe(zone, order,
2586 high_wmark_pages(zone), 0, 0)) {
2590 /* If balanced, clear the congested flag */
2591 zone_clear_flag(zone, ZONE_CONGESTED);
2597 for (i = 0; i <= end_zone; i++) {
2598 struct zone *zone = pgdat->node_zones + i;
2600 lru_pages += zone_reclaimable_pages(zone);
2604 * Now scan the zone in the dma->highmem direction, stopping
2605 * at the last zone which needs scanning.
2607 * We do this because the page allocator works in the opposite
2608 * direction. This prevents the page allocator from allocating
2609 * pages behind kswapd's direction of progress, which would
2610 * cause too much scanning of the lower zones.
2612 for (i = 0; i <= end_zone; i++) {
2613 struct zone *zone = pgdat->node_zones + i;
2615 unsigned long balance_gap;
2617 if (!populated_zone(zone))
2620 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2625 nr_soft_scanned = 0;
2627 * Call soft limit reclaim before calling shrink_zone.
2629 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2632 sc.nr_reclaimed += nr_soft_reclaimed;
2633 total_scanned += nr_soft_scanned;
2636 * We put equal pressure on every zone, unless
2637 * one zone has way too many pages free
2638 * already. The "too many pages" is defined
2639 * as the high wmark plus a "gap" where the
2640 * gap is either the low watermark or 1%
2641 * of the zone, whichever is smaller.
2643 balance_gap = min(low_wmark_pages(zone),
2644 (zone->present_pages +
2645 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2646 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2647 if (!zone_watermark_ok_safe(zone, order,
2648 high_wmark_pages(zone) + balance_gap,
2650 shrink_zone(priority, zone, &sc);
2652 reclaim_state->reclaimed_slab = 0;
2653 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2654 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2655 total_scanned += sc.nr_scanned;
2657 if (nr_slab == 0 && !zone_reclaimable(zone))
2658 zone->all_unreclaimable = 1;
2662 * If we've done a decent amount of scanning and
2663 * the reclaim ratio is low, start doing writepage
2664 * even in laptop mode
2666 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2667 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2668 sc.may_writepage = 1;
2670 if (zone->all_unreclaimable) {
2671 if (end_zone && end_zone == i)
2676 if (!zone_watermark_ok_safe(zone, order,
2677 high_wmark_pages(zone), end_zone, 0)) {
2680 * We are still under min water mark. This
2681 * means that we have a GFP_ATOMIC allocation
2682 * failure risk. Hurry up!
2684 if (!zone_watermark_ok_safe(zone, order,
2685 min_wmark_pages(zone), end_zone, 0))
2686 has_under_min_watermark_zone = 1;
2689 * If a zone reaches its high watermark,
2690 * consider it to be no longer congested. It's
2691 * possible there are dirty pages backed by
2692 * congested BDIs but as pressure is relieved,
2693 * spectulatively avoid congestion waits
2695 zone_clear_flag(zone, ZONE_CONGESTED);
2696 if (i <= *classzone_idx)
2697 balanced += zone->present_pages;
2701 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2702 break; /* kswapd: all done */
2704 * OK, kswapd is getting into trouble. Take a nap, then take
2705 * another pass across the zones.
2707 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2708 if (has_under_min_watermark_zone)
2709 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2711 congestion_wait(BLK_RW_ASYNC, HZ/10);
2715 * We do this so kswapd doesn't build up large priorities for
2716 * example when it is freeing in parallel with allocators. It
2717 * matches the direct reclaim path behaviour in terms of impact
2718 * on zone->*_priority.
2720 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2726 * order-0: All zones must meet high watermark for a balanced node
2727 * high-order: Balanced zones must make up at least 25% of the node
2728 * for the node to be balanced
2730 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2736 * Fragmentation may mean that the system cannot be
2737 * rebalanced for high-order allocations in all zones.
2738 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2739 * it means the zones have been fully scanned and are still
2740 * not balanced. For high-order allocations, there is
2741 * little point trying all over again as kswapd may
2744 * Instead, recheck all watermarks at order-0 as they
2745 * are the most important. If watermarks are ok, kswapd will go
2746 * back to sleep. High-order users can still perform direct
2747 * reclaim if they wish.
2749 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2750 order = sc.order = 0;
2756 * If kswapd was reclaiming at a higher order, it has the option of
2757 * sleeping without all zones being balanced. Before it does, it must
2758 * ensure that the watermarks for order-0 on *all* zones are met and
2759 * that the congestion flags are cleared. The congestion flag must
2760 * be cleared as kswapd is the only mechanism that clears the flag
2761 * and it is potentially going to sleep here.
2764 for (i = 0; i <= end_zone; i++) {
2765 struct zone *zone = pgdat->node_zones + i;
2767 if (!populated_zone(zone))
2770 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2773 /* Confirm the zone is balanced for order-0 */
2774 if (!zone_watermark_ok(zone, 0,
2775 high_wmark_pages(zone), 0, 0)) {
2776 order = sc.order = 0;
2780 /* If balanced, clear the congested flag */
2781 zone_clear_flag(zone, ZONE_CONGESTED);
2782 if (i <= *classzone_idx)
2783 balanced += zone->present_pages;
2788 * Return the order we were reclaiming at so sleeping_prematurely()
2789 * makes a decision on the order we were last reclaiming at. However,
2790 * if another caller entered the allocator slow path while kswapd
2791 * was awake, order will remain at the higher level
2793 *classzone_idx = end_zone;
2797 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2802 if (freezing(current) || kthread_should_stop())
2805 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2807 /* Try to sleep for a short interval */
2808 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2809 remaining = schedule_timeout(HZ/10);
2810 finish_wait(&pgdat->kswapd_wait, &wait);
2811 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2815 * After a short sleep, check if it was a premature sleep. If not, then
2816 * go fully to sleep until explicitly woken up.
2818 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2819 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2822 * vmstat counters are not perfectly accurate and the estimated
2823 * value for counters such as NR_FREE_PAGES can deviate from the
2824 * true value by nr_online_cpus * threshold. To avoid the zone
2825 * watermarks being breached while under pressure, we reduce the
2826 * per-cpu vmstat threshold while kswapd is awake and restore
2827 * them before going back to sleep.
2829 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2831 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2834 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2836 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2838 finish_wait(&pgdat->kswapd_wait, &wait);
2842 * The background pageout daemon, started as a kernel thread
2843 * from the init process.
2845 * This basically trickles out pages so that we have _some_
2846 * free memory available even if there is no other activity
2847 * that frees anything up. This is needed for things like routing
2848 * etc, where we otherwise might have all activity going on in
2849 * asynchronous contexts that cannot page things out.
2851 * If there are applications that are active memory-allocators
2852 * (most normal use), this basically shouldn't matter.
2854 static int kswapd(void *p)
2856 unsigned long order, new_order;
2857 unsigned balanced_order;
2858 int classzone_idx, new_classzone_idx;
2859 int balanced_classzone_idx;
2860 pg_data_t *pgdat = (pg_data_t*)p;
2861 struct task_struct *tsk = current;
2863 struct reclaim_state reclaim_state = {
2864 .reclaimed_slab = 0,
2866 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2868 lockdep_set_current_reclaim_state(GFP_KERNEL);
2870 if (!cpumask_empty(cpumask))
2871 set_cpus_allowed_ptr(tsk, cpumask);
2872 current->reclaim_state = &reclaim_state;
2875 * Tell the memory management that we're a "memory allocator",
2876 * and that if we need more memory we should get access to it
2877 * regardless (see "__alloc_pages()"). "kswapd" should
2878 * never get caught in the normal page freeing logic.
2880 * (Kswapd normally doesn't need memory anyway, but sometimes
2881 * you need a small amount of memory in order to be able to
2882 * page out something else, and this flag essentially protects
2883 * us from recursively trying to free more memory as we're
2884 * trying to free the first piece of memory in the first place).
2886 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2889 order = new_order = 0;
2891 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2892 balanced_classzone_idx = classzone_idx;
2897 * If the last balance_pgdat was unsuccessful it's unlikely a
2898 * new request of a similar or harder type will succeed soon
2899 * so consider going to sleep on the basis we reclaimed at
2901 if (balanced_classzone_idx >= new_classzone_idx &&
2902 balanced_order == new_order) {
2903 new_order = pgdat->kswapd_max_order;
2904 new_classzone_idx = pgdat->classzone_idx;
2905 pgdat->kswapd_max_order = 0;
2906 pgdat->classzone_idx = pgdat->nr_zones - 1;
2909 if (order < new_order || classzone_idx > new_classzone_idx) {
2911 * Don't sleep if someone wants a larger 'order'
2912 * allocation or has tigher zone constraints
2915 classzone_idx = new_classzone_idx;
2917 kswapd_try_to_sleep(pgdat, balanced_order,
2918 balanced_classzone_idx);
2919 order = pgdat->kswapd_max_order;
2920 classzone_idx = pgdat->classzone_idx;
2922 new_classzone_idx = classzone_idx;
2923 pgdat->kswapd_max_order = 0;
2924 pgdat->classzone_idx = pgdat->nr_zones - 1;
2927 ret = try_to_freeze();
2928 if (kthread_should_stop())
2932 * We can speed up thawing tasks if we don't call balance_pgdat
2933 * after returning from the refrigerator
2936 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2937 balanced_classzone_idx = classzone_idx;
2938 balanced_order = balance_pgdat(pgdat, order,
2939 &balanced_classzone_idx);
2946 * A zone is low on free memory, so wake its kswapd task to service it.
2948 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
2952 if (!populated_zone(zone))
2955 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2957 pgdat = zone->zone_pgdat;
2958 if (pgdat->kswapd_max_order < order) {
2959 pgdat->kswapd_max_order = order;
2960 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
2962 if (!waitqueue_active(&pgdat->kswapd_wait))
2964 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
2967 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2968 wake_up_interruptible(&pgdat->kswapd_wait);
2972 * The reclaimable count would be mostly accurate.
2973 * The less reclaimable pages may be
2974 * - mlocked pages, which will be moved to unevictable list when encountered
2975 * - mapped pages, which may require several travels to be reclaimed
2976 * - dirty pages, which is not "instantly" reclaimable
2978 unsigned long global_reclaimable_pages(void)
2982 nr = global_page_state(NR_ACTIVE_FILE) +
2983 global_page_state(NR_INACTIVE_FILE);
2985 if (nr_swap_pages > 0)
2986 nr += global_page_state(NR_ACTIVE_ANON) +
2987 global_page_state(NR_INACTIVE_ANON);
2992 unsigned long zone_reclaimable_pages(struct zone *zone)
2996 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2997 zone_page_state(zone, NR_INACTIVE_FILE);
2999 if (nr_swap_pages > 0)
3000 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
3001 zone_page_state(zone, NR_INACTIVE_ANON);
3006 #ifdef CONFIG_HIBERNATION
3008 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3011 * Rather than trying to age LRUs the aim is to preserve the overall
3012 * LRU order by reclaiming preferentially
3013 * inactive > active > active referenced > active mapped
3015 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
3017 struct reclaim_state reclaim_state;
3018 struct scan_control sc = {
3019 .gfp_mask = GFP_HIGHUSER_MOVABLE,
3023 .nr_to_reclaim = nr_to_reclaim,
3024 .hibernation_mode = 1,
3027 struct shrink_control shrink = {
3028 .gfp_mask = sc.gfp_mask,
3030 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3031 struct task_struct *p = current;
3032 unsigned long nr_reclaimed;
3034 p->flags |= PF_MEMALLOC;
3035 lockdep_set_current_reclaim_state(sc.gfp_mask);
3036 reclaim_state.reclaimed_slab = 0;
3037 p->reclaim_state = &reclaim_state;
3039 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3041 p->reclaim_state = NULL;
3042 lockdep_clear_current_reclaim_state();
3043 p->flags &= ~PF_MEMALLOC;
3045 return nr_reclaimed;
3047 #endif /* CONFIG_HIBERNATION */
3049 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3050 not required for correctness. So if the last cpu in a node goes
3051 away, we get changed to run anywhere: as the first one comes back,
3052 restore their cpu bindings. */
3053 static int __devinit cpu_callback(struct notifier_block *nfb,
3054 unsigned long action, void *hcpu)
3058 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3059 for_each_node_state(nid, N_HIGH_MEMORY) {
3060 pg_data_t *pgdat = NODE_DATA(nid);
3061 const struct cpumask *mask;
3063 mask = cpumask_of_node(pgdat->node_id);
3065 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3066 /* One of our CPUs online: restore mask */
3067 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3074 * This kswapd start function will be called by init and node-hot-add.
3075 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3077 int kswapd_run(int nid)
3079 pg_data_t *pgdat = NODE_DATA(nid);
3085 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3086 if (IS_ERR(pgdat->kswapd)) {
3087 /* failure at boot is fatal */
3088 BUG_ON(system_state == SYSTEM_BOOTING);
3089 printk("Failed to start kswapd on node %d\n",nid);
3096 * Called by memory hotplug when all memory in a node is offlined.
3098 void kswapd_stop(int nid)
3100 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3103 kthread_stop(kswapd);
3106 static int __init kswapd_init(void)
3111 for_each_node_state(nid, N_HIGH_MEMORY)
3113 hotcpu_notifier(cpu_callback, 0);
3117 module_init(kswapd_init)
3123 * If non-zero call zone_reclaim when the number of free pages falls below
3126 int zone_reclaim_mode __read_mostly;
3128 #define RECLAIM_OFF 0
3129 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3130 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3131 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3134 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3135 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3138 #define ZONE_RECLAIM_PRIORITY 4
3141 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3144 int sysctl_min_unmapped_ratio = 1;
3147 * If the number of slab pages in a zone grows beyond this percentage then
3148 * slab reclaim needs to occur.
3150 int sysctl_min_slab_ratio = 5;
3152 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3154 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3155 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3156 zone_page_state(zone, NR_ACTIVE_FILE);
3159 * It's possible for there to be more file mapped pages than
3160 * accounted for by the pages on the file LRU lists because
3161 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3163 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3166 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3167 static long zone_pagecache_reclaimable(struct zone *zone)
3169 long nr_pagecache_reclaimable;
3173 * If RECLAIM_SWAP is set, then all file pages are considered
3174 * potentially reclaimable. Otherwise, we have to worry about
3175 * pages like swapcache and zone_unmapped_file_pages() provides
3178 if (zone_reclaim_mode & RECLAIM_SWAP)
3179 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3181 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3183 /* If we can't clean pages, remove dirty pages from consideration */
3184 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3185 delta += zone_page_state(zone, NR_FILE_DIRTY);
3187 /* Watch for any possible underflows due to delta */
3188 if (unlikely(delta > nr_pagecache_reclaimable))
3189 delta = nr_pagecache_reclaimable;
3191 return nr_pagecache_reclaimable - delta;
3195 * Try to free up some pages from this zone through reclaim.
3197 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3199 /* Minimum pages needed in order to stay on node */
3200 const unsigned long nr_pages = 1 << order;
3201 struct task_struct *p = current;
3202 struct reclaim_state reclaim_state;
3204 struct scan_control sc = {
3205 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3206 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3208 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3210 .gfp_mask = gfp_mask,
3213 struct shrink_control shrink = {
3214 .gfp_mask = sc.gfp_mask,
3216 unsigned long nr_slab_pages0, nr_slab_pages1;
3220 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3221 * and we also need to be able to write out pages for RECLAIM_WRITE
3224 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3225 lockdep_set_current_reclaim_state(gfp_mask);
3226 reclaim_state.reclaimed_slab = 0;
3227 p->reclaim_state = &reclaim_state;
3229 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3231 * Free memory by calling shrink zone with increasing
3232 * priorities until we have enough memory freed.
3234 priority = ZONE_RECLAIM_PRIORITY;
3236 shrink_zone(priority, zone, &sc);
3238 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3241 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3242 if (nr_slab_pages0 > zone->min_slab_pages) {
3244 * shrink_slab() does not currently allow us to determine how
3245 * many pages were freed in this zone. So we take the current
3246 * number of slab pages and shake the slab until it is reduced
3247 * by the same nr_pages that we used for reclaiming unmapped
3250 * Note that shrink_slab will free memory on all zones and may
3254 unsigned long lru_pages = zone_reclaimable_pages(zone);
3256 /* No reclaimable slab or very low memory pressure */
3257 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3260 /* Freed enough memory */
3261 nr_slab_pages1 = zone_page_state(zone,
3262 NR_SLAB_RECLAIMABLE);
3263 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3268 * Update nr_reclaimed by the number of slab pages we
3269 * reclaimed from this zone.
3271 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3272 if (nr_slab_pages1 < nr_slab_pages0)
3273 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3276 p->reclaim_state = NULL;
3277 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3278 lockdep_clear_current_reclaim_state();
3279 return sc.nr_reclaimed >= nr_pages;
3282 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3288 * Zone reclaim reclaims unmapped file backed pages and
3289 * slab pages if we are over the defined limits.
3291 * A small portion of unmapped file backed pages is needed for
3292 * file I/O otherwise pages read by file I/O will be immediately
3293 * thrown out if the zone is overallocated. So we do not reclaim
3294 * if less than a specified percentage of the zone is used by
3295 * unmapped file backed pages.
3297 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3298 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3299 return ZONE_RECLAIM_FULL;
3301 if (zone->all_unreclaimable)
3302 return ZONE_RECLAIM_FULL;
3305 * Do not scan if the allocation should not be delayed.
3307 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3308 return ZONE_RECLAIM_NOSCAN;
3311 * Only run zone reclaim on the local zone or on zones that do not
3312 * have associated processors. This will favor the local processor
3313 * over remote processors and spread off node memory allocations
3314 * as wide as possible.
3316 node_id = zone_to_nid(zone);
3317 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3318 return ZONE_RECLAIM_NOSCAN;
3320 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3321 return ZONE_RECLAIM_NOSCAN;
3323 ret = __zone_reclaim(zone, gfp_mask, order);
3324 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3327 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3334 * page_evictable - test whether a page is evictable
3335 * @page: the page to test
3336 * @vma: the VMA in which the page is or will be mapped, may be NULL
3338 * Test whether page is evictable--i.e., should be placed on active/inactive
3339 * lists vs unevictable list. The vma argument is !NULL when called from the
3340 * fault path to determine how to instantate a new page.
3342 * Reasons page might not be evictable:
3343 * (1) page's mapping marked unevictable
3344 * (2) page is part of an mlocked VMA
3347 int page_evictable(struct page *page, struct vm_area_struct *vma)
3350 if (mapping_unevictable(page_mapping(page)))
3353 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3360 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3361 * @page: page to check evictability and move to appropriate lru list
3362 * @zone: zone page is in
3364 * Checks a page for evictability and moves the page to the appropriate
3367 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3368 * have PageUnevictable set.
3370 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3372 VM_BUG_ON(PageActive(page));
3375 ClearPageUnevictable(page);
3376 if (page_evictable(page, NULL)) {
3377 enum lru_list l = page_lru_base_type(page);
3379 __dec_zone_state(zone, NR_UNEVICTABLE);
3380 list_move(&page->lru, &zone->lru[l].list);
3381 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
3382 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3383 __count_vm_event(UNEVICTABLE_PGRESCUED);
3386 * rotate unevictable list
3388 SetPageUnevictable(page);
3389 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
3390 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
3391 if (page_evictable(page, NULL))
3397 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3398 * @mapping: struct address_space to scan for evictable pages
3400 * Scan all pages in mapping. Check unevictable pages for
3401 * evictability and move them to the appropriate zone lru list.
3403 void scan_mapping_unevictable_pages(struct address_space *mapping)
3406 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3409 struct pagevec pvec;
3411 if (mapping->nrpages == 0)
3414 pagevec_init(&pvec, 0);
3415 while (next < end &&
3416 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3422 for (i = 0; i < pagevec_count(&pvec); i++) {
3423 struct page *page = pvec.pages[i];
3424 pgoff_t page_index = page->index;
3425 struct zone *pagezone = page_zone(page);
3428 if (page_index > next)
3432 if (pagezone != zone) {
3434 spin_unlock_irq(&zone->lru_lock);
3436 spin_lock_irq(&zone->lru_lock);
3439 if (PageLRU(page) && PageUnevictable(page))
3440 check_move_unevictable_page(page, zone);
3443 spin_unlock_irq(&zone->lru_lock);
3444 pagevec_release(&pvec);
3446 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3451 static void warn_scan_unevictable_pages(void)
3453 printk_once(KERN_WARNING
3454 "The scan_unevictable_pages sysctl/node-interface has been "
3455 "disabled for lack of a legitimate use case. If you have "
3456 "one, please send an email to linux-mm@kvack.org.\n");
3460 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3461 * all nodes' unevictable lists for evictable pages
3463 unsigned long scan_unevictable_pages;
3465 int scan_unevictable_handler(struct ctl_table *table, int write,
3466 void __user *buffer,
3467 size_t *length, loff_t *ppos)
3469 warn_scan_unevictable_pages();
3470 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3471 scan_unevictable_pages = 0;
3477 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3478 * a specified node's per zone unevictable lists for evictable pages.
3481 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3482 struct sysdev_attribute *attr,
3485 warn_scan_unevictable_pages();
3486 return sprintf(buf, "0\n"); /* always zero; should fit... */
3489 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3490 struct sysdev_attribute *attr,
3491 const char *buf, size_t count)
3493 warn_scan_unevictable_pages();
3498 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3499 read_scan_unevictable_node,
3500 write_scan_unevictable_node);
3502 int scan_unevictable_register_node(struct node *node)
3504 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3507 void scan_unevictable_unregister_node(struct node *node)
3509 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);