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;
107 * The memory cgroup that hit its limit and as a result is the
108 * primary target of this reclaim invocation.
110 struct mem_cgroup *target_mem_cgroup;
113 * Nodemask of nodes allowed by the caller. If NULL, all nodes
116 nodemask_t *nodemask;
119 struct mem_cgroup_zone {
120 struct mem_cgroup *mem_cgroup;
124 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
126 #ifdef ARCH_HAS_PREFETCH
127 #define prefetch_prev_lru_page(_page, _base, _field) \
129 if ((_page)->lru.prev != _base) { \
132 prev = lru_to_page(&(_page->lru)); \
133 prefetch(&prev->_field); \
137 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
140 #ifdef ARCH_HAS_PREFETCHW
141 #define prefetchw_prev_lru_page(_page, _base, _field) \
143 if ((_page)->lru.prev != _base) { \
146 prev = lru_to_page(&(_page->lru)); \
147 prefetchw(&prev->_field); \
151 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
155 * From 0 .. 100. Higher means more swappy.
157 int vm_swappiness = 60;
158 long vm_total_pages; /* The total number of pages which the VM controls */
160 static LIST_HEAD(shrinker_list);
161 static DECLARE_RWSEM(shrinker_rwsem);
163 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
164 static bool global_reclaim(struct scan_control *sc)
166 return !sc->target_mem_cgroup;
169 static bool scanning_global_lru(struct mem_cgroup_zone *mz)
171 return !mz->mem_cgroup;
174 static bool global_reclaim(struct scan_control *sc)
179 static bool scanning_global_lru(struct mem_cgroup_zone *mz)
185 static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz)
187 if (!scanning_global_lru(mz))
188 return mem_cgroup_get_reclaim_stat(mz->mem_cgroup, mz->zone);
190 return &mz->zone->reclaim_stat;
193 static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone *mz,
196 if (!scanning_global_lru(mz))
197 return mem_cgroup_zone_nr_lru_pages(mz->mem_cgroup,
198 zone_to_nid(mz->zone),
202 return zone_page_state(mz->zone, NR_LRU_BASE + lru);
207 * Add a shrinker callback to be called from the vm
209 void register_shrinker(struct shrinker *shrinker)
211 atomic_long_set(&shrinker->nr_in_batch, 0);
212 down_write(&shrinker_rwsem);
213 list_add_tail(&shrinker->list, &shrinker_list);
214 up_write(&shrinker_rwsem);
216 EXPORT_SYMBOL(register_shrinker);
221 void unregister_shrinker(struct shrinker *shrinker)
223 down_write(&shrinker_rwsem);
224 list_del(&shrinker->list);
225 up_write(&shrinker_rwsem);
227 EXPORT_SYMBOL(unregister_shrinker);
229 static inline int do_shrinker_shrink(struct shrinker *shrinker,
230 struct shrink_control *sc,
231 unsigned long nr_to_scan)
233 sc->nr_to_scan = nr_to_scan;
234 return (*shrinker->shrink)(shrinker, sc);
237 #define SHRINK_BATCH 128
239 * Call the shrink functions to age shrinkable caches
241 * Here we assume it costs one seek to replace a lru page and that it also
242 * takes a seek to recreate a cache object. With this in mind we age equal
243 * percentages of the lru and ageable caches. This should balance the seeks
244 * generated by these structures.
246 * If the vm encountered mapped pages on the LRU it increase the pressure on
247 * slab to avoid swapping.
249 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
251 * `lru_pages' represents the number of on-LRU pages in all the zones which
252 * are eligible for the caller's allocation attempt. It is used for balancing
253 * slab reclaim versus page reclaim.
255 * Returns the number of slab objects which we shrunk.
257 unsigned long shrink_slab(struct shrink_control *shrink,
258 unsigned long nr_pages_scanned,
259 unsigned long lru_pages)
261 struct shrinker *shrinker;
262 unsigned long ret = 0;
264 if (nr_pages_scanned == 0)
265 nr_pages_scanned = SWAP_CLUSTER_MAX;
267 if (!down_read_trylock(&shrinker_rwsem)) {
268 /* Assume we'll be able to shrink next time */
273 list_for_each_entry(shrinker, &shrinker_list, list) {
274 unsigned long long delta;
280 long batch_size = shrinker->batch ? shrinker->batch
283 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
288 * copy the current shrinker scan count into a local variable
289 * and zero it so that other concurrent shrinker invocations
290 * don't also do this scanning work.
292 nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
295 delta = (4 * nr_pages_scanned) / shrinker->seeks;
297 do_div(delta, lru_pages + 1);
299 if (total_scan < 0) {
300 printk(KERN_ERR "shrink_slab: %pF negative objects to "
302 shrinker->shrink, total_scan);
303 total_scan = max_pass;
307 * We need to avoid excessive windup on filesystem shrinkers
308 * due to large numbers of GFP_NOFS allocations causing the
309 * shrinkers to return -1 all the time. This results in a large
310 * nr being built up so when a shrink that can do some work
311 * comes along it empties the entire cache due to nr >>>
312 * max_pass. This is bad for sustaining a working set in
315 * Hence only allow the shrinker to scan the entire cache when
316 * a large delta change is calculated directly.
318 if (delta < max_pass / 4)
319 total_scan = min(total_scan, max_pass / 2);
322 * Avoid risking looping forever due to too large nr value:
323 * never try to free more than twice the estimate number of
326 if (total_scan > max_pass * 2)
327 total_scan = max_pass * 2;
329 trace_mm_shrink_slab_start(shrinker, shrink, nr,
330 nr_pages_scanned, lru_pages,
331 max_pass, delta, total_scan);
333 while (total_scan >= batch_size) {
336 nr_before = do_shrinker_shrink(shrinker, shrink, 0);
337 shrink_ret = do_shrinker_shrink(shrinker, shrink,
339 if (shrink_ret == -1)
341 if (shrink_ret < nr_before)
342 ret += nr_before - shrink_ret;
343 count_vm_events(SLABS_SCANNED, batch_size);
344 total_scan -= batch_size;
350 * move the unused scan count back into the shrinker in a
351 * manner that handles concurrent updates. If we exhausted the
352 * scan, there is no need to do an update.
355 new_nr = atomic_long_add_return(total_scan,
356 &shrinker->nr_in_batch);
358 new_nr = atomic_long_read(&shrinker->nr_in_batch);
360 trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
362 up_read(&shrinker_rwsem);
368 static void set_reclaim_mode(int priority, struct scan_control *sc,
371 reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
374 * Initially assume we are entering either lumpy reclaim or
375 * reclaim/compaction.Depending on the order, we will either set the
376 * sync mode or just reclaim order-0 pages later.
378 if (COMPACTION_BUILD)
379 sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
381 sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
384 * Avoid using lumpy reclaim or reclaim/compaction if possible by
385 * restricting when its set to either costly allocations or when
386 * under memory pressure
388 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
389 sc->reclaim_mode |= syncmode;
390 else if (sc->order && priority < DEF_PRIORITY - 2)
391 sc->reclaim_mode |= syncmode;
393 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
396 static void reset_reclaim_mode(struct scan_control *sc)
398 sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
401 static inline int is_page_cache_freeable(struct page *page)
404 * A freeable page cache page is referenced only by the caller
405 * that isolated the page, the page cache radix tree and
406 * optional buffer heads at page->private.
408 return page_count(page) - page_has_private(page) == 2;
411 static int may_write_to_queue(struct backing_dev_info *bdi,
412 struct scan_control *sc)
414 if (current->flags & PF_SWAPWRITE)
416 if (!bdi_write_congested(bdi))
418 if (bdi == current->backing_dev_info)
421 /* lumpy reclaim for hugepage often need a lot of write */
422 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
428 * We detected a synchronous write error writing a page out. Probably
429 * -ENOSPC. We need to propagate that into the address_space for a subsequent
430 * fsync(), msync() or close().
432 * The tricky part is that after writepage we cannot touch the mapping: nothing
433 * prevents it from being freed up. But we have a ref on the page and once
434 * that page is locked, the mapping is pinned.
436 * We're allowed to run sleeping lock_page() here because we know the caller has
439 static void handle_write_error(struct address_space *mapping,
440 struct page *page, int error)
443 if (page_mapping(page) == mapping)
444 mapping_set_error(mapping, error);
448 /* possible outcome of pageout() */
450 /* failed to write page out, page is locked */
452 /* move page to the active list, page is locked */
454 /* page has been sent to the disk successfully, page is unlocked */
456 /* page is clean and locked */
461 * pageout is called by shrink_page_list() for each dirty page.
462 * Calls ->writepage().
464 static pageout_t pageout(struct page *page, struct address_space *mapping,
465 struct scan_control *sc)
468 * If the page is dirty, only perform writeback if that write
469 * will be non-blocking. To prevent this allocation from being
470 * stalled by pagecache activity. But note that there may be
471 * stalls if we need to run get_block(). We could test
472 * PagePrivate for that.
474 * If this process is currently in __generic_file_aio_write() against
475 * this page's queue, we can perform writeback even if that
478 * If the page is swapcache, write it back even if that would
479 * block, for some throttling. This happens by accident, because
480 * swap_backing_dev_info is bust: it doesn't reflect the
481 * congestion state of the swapdevs. Easy to fix, if needed.
483 if (!is_page_cache_freeable(page))
487 * Some data journaling orphaned pages can have
488 * page->mapping == NULL while being dirty with clean buffers.
490 if (page_has_private(page)) {
491 if (try_to_free_buffers(page)) {
492 ClearPageDirty(page);
493 printk("%s: orphaned page\n", __func__);
499 if (mapping->a_ops->writepage == NULL)
500 return PAGE_ACTIVATE;
501 if (!may_write_to_queue(mapping->backing_dev_info, sc))
504 if (clear_page_dirty_for_io(page)) {
506 struct writeback_control wbc = {
507 .sync_mode = WB_SYNC_NONE,
508 .nr_to_write = SWAP_CLUSTER_MAX,
510 .range_end = LLONG_MAX,
514 SetPageReclaim(page);
515 res = mapping->a_ops->writepage(page, &wbc);
517 handle_write_error(mapping, page, res);
518 if (res == AOP_WRITEPAGE_ACTIVATE) {
519 ClearPageReclaim(page);
520 return PAGE_ACTIVATE;
523 if (!PageWriteback(page)) {
524 /* synchronous write or broken a_ops? */
525 ClearPageReclaim(page);
527 trace_mm_vmscan_writepage(page,
528 trace_reclaim_flags(page, sc->reclaim_mode));
529 inc_zone_page_state(page, NR_VMSCAN_WRITE);
537 * Same as remove_mapping, but if the page is removed from the mapping, it
538 * gets returned with a refcount of 0.
540 static int __remove_mapping(struct address_space *mapping, struct page *page)
542 BUG_ON(!PageLocked(page));
543 BUG_ON(mapping != page_mapping(page));
545 spin_lock_irq(&mapping->tree_lock);
547 * The non racy check for a busy page.
549 * Must be careful with the order of the tests. When someone has
550 * a ref to the page, it may be possible that they dirty it then
551 * drop the reference. So if PageDirty is tested before page_count
552 * here, then the following race may occur:
554 * get_user_pages(&page);
555 * [user mapping goes away]
557 * !PageDirty(page) [good]
558 * SetPageDirty(page);
560 * !page_count(page) [good, discard it]
562 * [oops, our write_to data is lost]
564 * Reversing the order of the tests ensures such a situation cannot
565 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
566 * load is not satisfied before that of page->_count.
568 * Note that if SetPageDirty is always performed via set_page_dirty,
569 * and thus under tree_lock, then this ordering is not required.
571 if (!page_freeze_refs(page, 2))
573 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
574 if (unlikely(PageDirty(page))) {
575 page_unfreeze_refs(page, 2);
579 if (PageSwapCache(page)) {
580 swp_entry_t swap = { .val = page_private(page) };
581 __delete_from_swap_cache(page);
582 spin_unlock_irq(&mapping->tree_lock);
583 swapcache_free(swap, page);
585 void (*freepage)(struct page *);
587 freepage = mapping->a_ops->freepage;
589 __delete_from_page_cache(page);
590 spin_unlock_irq(&mapping->tree_lock);
591 mem_cgroup_uncharge_cache_page(page);
593 if (freepage != NULL)
600 spin_unlock_irq(&mapping->tree_lock);
605 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
606 * someone else has a ref on the page, abort and return 0. If it was
607 * successfully detached, return 1. Assumes the caller has a single ref on
610 int remove_mapping(struct address_space *mapping, struct page *page)
612 if (__remove_mapping(mapping, page)) {
614 * Unfreezing the refcount with 1 rather than 2 effectively
615 * drops the pagecache ref for us without requiring another
618 page_unfreeze_refs(page, 1);
625 * putback_lru_page - put previously isolated page onto appropriate LRU list
626 * @page: page to be put back to appropriate lru list
628 * Add previously isolated @page to appropriate LRU list.
629 * Page may still be unevictable for other reasons.
631 * lru_lock must not be held, interrupts must be enabled.
633 void putback_lru_page(struct page *page)
636 int active = !!TestClearPageActive(page);
637 int was_unevictable = PageUnevictable(page);
639 VM_BUG_ON(PageLRU(page));
642 ClearPageUnevictable(page);
644 if (page_evictable(page, NULL)) {
646 * For evictable pages, we can use the cache.
647 * In event of a race, worst case is we end up with an
648 * unevictable page on [in]active list.
649 * We know how to handle that.
651 lru = active + page_lru_base_type(page);
652 lru_cache_add_lru(page, lru);
655 * Put unevictable pages directly on zone's unevictable
658 lru = LRU_UNEVICTABLE;
659 add_page_to_unevictable_list(page);
661 * When racing with an mlock or AS_UNEVICTABLE clearing
662 * (page is unlocked) make sure that if the other thread
663 * does not observe our setting of PG_lru and fails
664 * isolation/check_move_unevictable_page,
665 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
666 * the page back to the evictable list.
668 * The other side is TestClearPageMlocked() or shmem_lock().
674 * page's status can change while we move it among lru. If an evictable
675 * page is on unevictable list, it never be freed. To avoid that,
676 * check after we added it to the list, again.
678 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
679 if (!isolate_lru_page(page)) {
683 /* This means someone else dropped this page from LRU
684 * So, it will be freed or putback to LRU again. There is
685 * nothing to do here.
689 if (was_unevictable && lru != LRU_UNEVICTABLE)
690 count_vm_event(UNEVICTABLE_PGRESCUED);
691 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
692 count_vm_event(UNEVICTABLE_PGCULLED);
694 put_page(page); /* drop ref from isolate */
697 enum page_references {
699 PAGEREF_RECLAIM_CLEAN,
704 static enum page_references page_check_references(struct page *page,
705 struct mem_cgroup_zone *mz,
706 struct scan_control *sc)
708 int referenced_ptes, referenced_page;
709 unsigned long vm_flags;
711 referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
712 referenced_page = TestClearPageReferenced(page);
714 /* Lumpy reclaim - ignore references */
715 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
716 return PAGEREF_RECLAIM;
719 * Mlock lost the isolation race with us. Let try_to_unmap()
720 * move the page to the unevictable list.
722 if (vm_flags & VM_LOCKED)
723 return PAGEREF_RECLAIM;
725 if (referenced_ptes) {
727 return PAGEREF_ACTIVATE;
729 * All mapped pages start out with page table
730 * references from the instantiating fault, so we need
731 * to look twice if a mapped file page is used more
734 * Mark it and spare it for another trip around the
735 * inactive list. Another page table reference will
736 * lead to its activation.
738 * Note: the mark is set for activated pages as well
739 * so that recently deactivated but used pages are
742 SetPageReferenced(page);
744 if (referenced_page || referenced_ptes > 1)
745 return PAGEREF_ACTIVATE;
748 * Activate file-backed executable pages after first usage.
750 if (vm_flags & VM_EXEC)
751 return PAGEREF_ACTIVATE;
756 /* Reclaim if clean, defer dirty pages to writeback */
757 if (referenced_page && !PageSwapBacked(page))
758 return PAGEREF_RECLAIM_CLEAN;
760 return PAGEREF_RECLAIM;
764 * shrink_page_list() returns the number of reclaimed pages
766 static unsigned long shrink_page_list(struct list_head *page_list,
767 struct mem_cgroup_zone *mz,
768 struct scan_control *sc,
770 unsigned long *ret_nr_dirty,
771 unsigned long *ret_nr_writeback)
773 LIST_HEAD(ret_pages);
774 LIST_HEAD(free_pages);
776 unsigned long nr_dirty = 0;
777 unsigned long nr_congested = 0;
778 unsigned long nr_reclaimed = 0;
779 unsigned long nr_writeback = 0;
783 while (!list_empty(page_list)) {
784 enum page_references references;
785 struct address_space *mapping;
791 page = lru_to_page(page_list);
792 list_del(&page->lru);
794 if (!trylock_page(page))
797 VM_BUG_ON(PageActive(page));
798 VM_BUG_ON(page_zone(page) != mz->zone);
802 if (unlikely(!page_evictable(page, NULL)))
805 if (!sc->may_unmap && page_mapped(page))
808 /* Double the slab pressure for mapped and swapcache pages */
809 if (page_mapped(page) || PageSwapCache(page))
812 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
813 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
815 if (PageWriteback(page)) {
818 * Synchronous reclaim cannot queue pages for
819 * writeback due to the possibility of stack overflow
820 * but if it encounters a page under writeback, wait
821 * for the IO to complete.
823 if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
825 wait_on_page_writeback(page);
832 references = page_check_references(page, mz, sc);
833 switch (references) {
834 case PAGEREF_ACTIVATE:
835 goto activate_locked;
838 case PAGEREF_RECLAIM:
839 case PAGEREF_RECLAIM_CLEAN:
840 ; /* try to reclaim the page below */
844 * Anonymous process memory has backing store?
845 * Try to allocate it some swap space here.
847 if (PageAnon(page) && !PageSwapCache(page)) {
848 if (!(sc->gfp_mask & __GFP_IO))
850 if (!add_to_swap(page))
851 goto activate_locked;
855 mapping = page_mapping(page);
858 * The page is mapped into the page tables of one or more
859 * processes. Try to unmap it here.
861 if (page_mapped(page) && mapping) {
862 switch (try_to_unmap(page, TTU_UNMAP)) {
864 goto activate_locked;
870 ; /* try to free the page below */
874 if (PageDirty(page)) {
878 * Only kswapd can writeback filesystem pages to
879 * avoid risk of stack overflow but do not writeback
880 * unless under significant pressure.
882 if (page_is_file_cache(page) &&
883 (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
885 * Immediately reclaim when written back.
886 * Similar in principal to deactivate_page()
887 * except we already have the page isolated
888 * and know it's dirty
890 inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
891 SetPageReclaim(page);
896 if (references == PAGEREF_RECLAIM_CLEAN)
900 if (!sc->may_writepage)
903 /* Page is dirty, try to write it out here */
904 switch (pageout(page, mapping, sc)) {
909 goto activate_locked;
911 if (PageWriteback(page))
917 * A synchronous write - probably a ramdisk. Go
918 * ahead and try to reclaim the page.
920 if (!trylock_page(page))
922 if (PageDirty(page) || PageWriteback(page))
924 mapping = page_mapping(page);
926 ; /* try to free the page below */
931 * If the page has buffers, try to free the buffer mappings
932 * associated with this page. If we succeed we try to free
935 * We do this even if the page is PageDirty().
936 * try_to_release_page() does not perform I/O, but it is
937 * possible for a page to have PageDirty set, but it is actually
938 * clean (all its buffers are clean). This happens if the
939 * buffers were written out directly, with submit_bh(). ext3
940 * will do this, as well as the blockdev mapping.
941 * try_to_release_page() will discover that cleanness and will
942 * drop the buffers and mark the page clean - it can be freed.
944 * Rarely, pages can have buffers and no ->mapping. These are
945 * the pages which were not successfully invalidated in
946 * truncate_complete_page(). We try to drop those buffers here
947 * and if that worked, and the page is no longer mapped into
948 * process address space (page_count == 1) it can be freed.
949 * Otherwise, leave the page on the LRU so it is swappable.
951 if (page_has_private(page)) {
952 if (!try_to_release_page(page, sc->gfp_mask))
953 goto activate_locked;
954 if (!mapping && page_count(page) == 1) {
956 if (put_page_testzero(page))
960 * rare race with speculative reference.
961 * the speculative reference will free
962 * this page shortly, so we may
963 * increment nr_reclaimed here (and
964 * leave it off the LRU).
972 if (!mapping || !__remove_mapping(mapping, page))
976 * At this point, we have no other references and there is
977 * no way to pick any more up (removed from LRU, removed
978 * from pagecache). Can use non-atomic bitops now (and
979 * we obviously don't have to worry about waking up a process
980 * waiting on the page lock, because there are no references.
982 __clear_page_locked(page);
987 * Is there need to periodically free_page_list? It would
988 * appear not as the counts should be low
990 list_add(&page->lru, &free_pages);
994 if (PageSwapCache(page))
995 try_to_free_swap(page);
997 putback_lru_page(page);
998 reset_reclaim_mode(sc);
1002 /* Not a candidate for swapping, so reclaim swap space. */
1003 if (PageSwapCache(page) && vm_swap_full())
1004 try_to_free_swap(page);
1005 VM_BUG_ON(PageActive(page));
1006 SetPageActive(page);
1011 reset_reclaim_mode(sc);
1013 list_add(&page->lru, &ret_pages);
1014 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
1018 * Tag a zone as congested if all the dirty pages encountered were
1019 * backed by a congested BDI. In this case, reclaimers should just
1020 * back off and wait for congestion to clear because further reclaim
1021 * will encounter the same problem
1023 if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
1024 zone_set_flag(mz->zone, ZONE_CONGESTED);
1026 free_hot_cold_page_list(&free_pages, 1);
1028 list_splice(&ret_pages, page_list);
1029 count_vm_events(PGACTIVATE, pgactivate);
1030 *ret_nr_dirty += nr_dirty;
1031 *ret_nr_writeback += nr_writeback;
1032 return nr_reclaimed;
1036 * Attempt to remove the specified page from its LRU. Only take this page
1037 * if it is of the appropriate PageActive status. Pages which are being
1038 * freed elsewhere are also ignored.
1040 * page: page to consider
1041 * mode: one of the LRU isolation modes defined above
1043 * returns 0 on success, -ve errno on failure.
1045 int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
1050 /* Only take pages on the LRU. */
1054 all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
1055 (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
1058 * When checking the active state, we need to be sure we are
1059 * dealing with comparible boolean values. Take the logical not
1062 if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
1065 if (!all_lru_mode && !!page_is_file_cache(page) != file)
1069 * When this function is being called for lumpy reclaim, we
1070 * initially look into all LRU pages, active, inactive and
1071 * unevictable; only give shrink_page_list evictable pages.
1073 if (PageUnevictable(page))
1078 if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
1081 if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
1084 if (likely(get_page_unless_zero(page))) {
1086 * Be careful not to clear PageLRU until after we're
1087 * sure the page is not being freed elsewhere -- the
1088 * page release code relies on it.
1098 * zone->lru_lock is heavily contended. Some of the functions that
1099 * shrink the lists perform better by taking out a batch of pages
1100 * and working on them outside the LRU lock.
1102 * For pagecache intensive workloads, this function is the hottest
1103 * spot in the kernel (apart from copy_*_user functions).
1105 * Appropriate locks must be held before calling this function.
1107 * @nr_to_scan: The number of pages to look through on the list.
1108 * @src: The LRU list to pull pages off.
1109 * @dst: The temp list to put pages on to.
1110 * @scanned: The number of pages that were scanned.
1111 * @order: The caller's attempted allocation order
1112 * @mode: One of the LRU isolation modes
1113 * @file: True [1] if isolating file [!anon] pages
1115 * returns how many pages were moved onto *@dst.
1117 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
1118 struct list_head *src, struct list_head *dst,
1119 unsigned long *scanned, int order, isolate_mode_t mode,
1122 unsigned long nr_taken = 0;
1123 unsigned long nr_lumpy_taken = 0;
1124 unsigned long nr_lumpy_dirty = 0;
1125 unsigned long nr_lumpy_failed = 0;
1128 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
1131 unsigned long end_pfn;
1132 unsigned long page_pfn;
1135 page = lru_to_page(src);
1136 prefetchw_prev_lru_page(page, src, flags);
1138 VM_BUG_ON(!PageLRU(page));
1140 switch (__isolate_lru_page(page, mode, file)) {
1142 mem_cgroup_lru_del(page);
1143 list_move(&page->lru, dst);
1144 nr_taken += hpage_nr_pages(page);
1148 /* else it is being freed elsewhere */
1149 list_move(&page->lru, src);
1160 * Attempt to take all pages in the order aligned region
1161 * surrounding the tag page. Only take those pages of
1162 * the same active state as that tag page. We may safely
1163 * round the target page pfn down to the requested order
1164 * as the mem_map is guaranteed valid out to MAX_ORDER,
1165 * where that page is in a different zone we will detect
1166 * it from its zone id and abort this block scan.
1168 zone_id = page_zone_id(page);
1169 page_pfn = page_to_pfn(page);
1170 pfn = page_pfn & ~((1 << order) - 1);
1171 end_pfn = pfn + (1 << order);
1172 for (; pfn < end_pfn; pfn++) {
1173 struct page *cursor_page;
1175 /* The target page is in the block, ignore it. */
1176 if (unlikely(pfn == page_pfn))
1179 /* Avoid holes within the zone. */
1180 if (unlikely(!pfn_valid_within(pfn)))
1183 cursor_page = pfn_to_page(pfn);
1185 /* Check that we have not crossed a zone boundary. */
1186 if (unlikely(page_zone_id(cursor_page) != zone_id))
1190 * If we don't have enough swap space, reclaiming of
1191 * anon page which don't already have a swap slot is
1194 if (nr_swap_pages <= 0 && PageSwapBacked(cursor_page) &&
1195 !PageSwapCache(cursor_page))
1198 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1199 unsigned int isolated_pages;
1201 mem_cgroup_lru_del(cursor_page);
1202 list_move(&cursor_page->lru, dst);
1203 isolated_pages = hpage_nr_pages(cursor_page);
1204 nr_taken += isolated_pages;
1205 nr_lumpy_taken += isolated_pages;
1206 if (PageDirty(cursor_page))
1207 nr_lumpy_dirty += isolated_pages;
1209 pfn += isolated_pages - 1;
1212 * Check if the page is freed already.
1214 * We can't use page_count() as that
1215 * requires compound_head and we don't
1216 * have a pin on the page here. If a
1217 * page is tail, we may or may not
1218 * have isolated the head, so assume
1219 * it's not free, it'd be tricky to
1220 * track the head status without a
1223 if (!PageTail(cursor_page) &&
1224 !atomic_read(&cursor_page->_count))
1230 /* If we break out of the loop above, lumpy reclaim failed */
1237 trace_mm_vmscan_lru_isolate(order,
1240 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1245 static unsigned long isolate_pages(unsigned long nr, struct mem_cgroup_zone *mz,
1246 struct list_head *dst,
1247 unsigned long *scanned, int order,
1248 isolate_mode_t mode, int active, int file)
1250 struct lruvec *lruvec;
1253 lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
1258 return isolate_lru_pages(nr, &lruvec->lists[lru], dst,
1259 scanned, order, mode, file);
1263 * clear_active_flags() is a helper for shrink_active_list(), clearing
1264 * any active bits from the pages in the list.
1266 static unsigned long clear_active_flags(struct list_head *page_list,
1267 unsigned int *count)
1273 list_for_each_entry(page, page_list, lru) {
1274 int numpages = hpage_nr_pages(page);
1275 lru = page_lru_base_type(page);
1276 if (PageActive(page)) {
1278 ClearPageActive(page);
1279 nr_active += numpages;
1282 count[lru] += numpages;
1289 * isolate_lru_page - tries to isolate a page from its LRU list
1290 * @page: page to isolate from its LRU list
1292 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1293 * vmstat statistic corresponding to whatever LRU list the page was on.
1295 * Returns 0 if the page was removed from an LRU list.
1296 * Returns -EBUSY if the page was not on an LRU list.
1298 * The returned page will have PageLRU() cleared. If it was found on
1299 * the active list, it will have PageActive set. If it was found on
1300 * the unevictable list, it will have the PageUnevictable bit set. That flag
1301 * may need to be cleared by the caller before letting the page go.
1303 * The vmstat statistic corresponding to the list on which the page was
1304 * found will be decremented.
1307 * (1) Must be called with an elevated refcount on the page. This is a
1308 * fundamentnal difference from isolate_lru_pages (which is called
1309 * without a stable reference).
1310 * (2) the lru_lock must not be held.
1311 * (3) interrupts must be enabled.
1313 int isolate_lru_page(struct page *page)
1317 VM_BUG_ON(!page_count(page));
1319 if (PageLRU(page)) {
1320 struct zone *zone = page_zone(page);
1322 spin_lock_irq(&zone->lru_lock);
1323 if (PageLRU(page)) {
1324 int lru = page_lru(page);
1329 del_page_from_lru_list(zone, page, lru);
1331 spin_unlock_irq(&zone->lru_lock);
1337 * Are there way too many processes in the direct reclaim path already?
1339 static int too_many_isolated(struct zone *zone, int file,
1340 struct scan_control *sc)
1342 unsigned long inactive, isolated;
1344 if (current_is_kswapd())
1347 if (!global_reclaim(sc))
1351 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1352 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1354 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1355 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1358 return isolated > inactive;
1362 * TODO: Try merging with migrations version of putback_lru_pages
1364 static noinline_for_stack void
1365 putback_lru_pages(struct mem_cgroup_zone *mz, struct scan_control *sc,
1366 unsigned long nr_anon, unsigned long nr_file,
1367 struct list_head *page_list)
1370 struct pagevec pvec;
1371 struct zone *zone = mz->zone;
1372 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1374 pagevec_init(&pvec, 1);
1377 * Put back any unfreeable pages.
1379 spin_lock(&zone->lru_lock);
1380 while (!list_empty(page_list)) {
1382 page = lru_to_page(page_list);
1383 VM_BUG_ON(PageLRU(page));
1384 list_del(&page->lru);
1385 if (unlikely(!page_evictable(page, NULL))) {
1386 spin_unlock_irq(&zone->lru_lock);
1387 putback_lru_page(page);
1388 spin_lock_irq(&zone->lru_lock);
1392 lru = page_lru(page);
1393 add_page_to_lru_list(zone, page, lru);
1394 if (is_active_lru(lru)) {
1395 int file = is_file_lru(lru);
1396 int numpages = hpage_nr_pages(page);
1397 reclaim_stat->recent_rotated[file] += numpages;
1399 if (!pagevec_add(&pvec, page)) {
1400 spin_unlock_irq(&zone->lru_lock);
1401 __pagevec_release(&pvec);
1402 spin_lock_irq(&zone->lru_lock);
1405 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1406 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1408 spin_unlock_irq(&zone->lru_lock);
1409 pagevec_release(&pvec);
1412 static noinline_for_stack void
1413 update_isolated_counts(struct mem_cgroup_zone *mz,
1414 struct scan_control *sc,
1415 unsigned long *nr_anon,
1416 unsigned long *nr_file,
1417 struct list_head *isolated_list)
1419 unsigned long nr_active;
1420 struct zone *zone = mz->zone;
1421 unsigned int count[NR_LRU_LISTS] = { 0, };
1422 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1424 nr_active = clear_active_flags(isolated_list, count);
1425 __count_vm_events(PGDEACTIVATE, nr_active);
1427 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1428 -count[LRU_ACTIVE_FILE]);
1429 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1430 -count[LRU_INACTIVE_FILE]);
1431 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1432 -count[LRU_ACTIVE_ANON]);
1433 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1434 -count[LRU_INACTIVE_ANON]);
1436 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1437 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1438 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1439 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1441 reclaim_stat->recent_scanned[0] += *nr_anon;
1442 reclaim_stat->recent_scanned[1] += *nr_file;
1446 * Returns true if a direct reclaim should wait on pages under writeback.
1448 * If we are direct reclaiming for contiguous pages and we do not reclaim
1449 * everything in the list, try again and wait for writeback IO to complete.
1450 * This will stall high-order allocations noticeably. Only do that when really
1451 * need to free the pages under high memory pressure.
1453 static inline bool should_reclaim_stall(unsigned long nr_taken,
1454 unsigned long nr_freed,
1456 struct scan_control *sc)
1458 int lumpy_stall_priority;
1460 /* kswapd should not stall on sync IO */
1461 if (current_is_kswapd())
1464 /* Only stall on lumpy reclaim */
1465 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1468 /* If we have reclaimed everything on the isolated list, no stall */
1469 if (nr_freed == nr_taken)
1473 * For high-order allocations, there are two stall thresholds.
1474 * High-cost allocations stall immediately where as lower
1475 * order allocations such as stacks require the scanning
1476 * priority to be much higher before stalling.
1478 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1479 lumpy_stall_priority = DEF_PRIORITY;
1481 lumpy_stall_priority = DEF_PRIORITY / 3;
1483 return priority <= lumpy_stall_priority;
1487 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1488 * of reclaimed pages
1490 static noinline_for_stack unsigned long
1491 shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
1492 struct scan_control *sc, int priority, int file)
1494 LIST_HEAD(page_list);
1495 unsigned long nr_scanned;
1496 unsigned long nr_reclaimed = 0;
1497 unsigned long nr_taken;
1498 unsigned long nr_anon;
1499 unsigned long nr_file;
1500 unsigned long nr_dirty = 0;
1501 unsigned long nr_writeback = 0;
1502 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1503 struct zone *zone = mz->zone;
1505 while (unlikely(too_many_isolated(zone, file, sc))) {
1506 congestion_wait(BLK_RW_ASYNC, HZ/10);
1508 /* We are about to die and free our memory. Return now. */
1509 if (fatal_signal_pending(current))
1510 return SWAP_CLUSTER_MAX;
1513 set_reclaim_mode(priority, sc, false);
1514 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
1515 reclaim_mode |= ISOLATE_ACTIVE;
1520 reclaim_mode |= ISOLATE_UNMAPPED;
1521 if (!sc->may_writepage)
1522 reclaim_mode |= ISOLATE_CLEAN;
1524 spin_lock_irq(&zone->lru_lock);
1526 nr_taken = isolate_pages(nr_to_scan, mz, &page_list,
1527 &nr_scanned, sc->order,
1528 reclaim_mode, 0, file);
1529 if (global_reclaim(sc)) {
1530 zone->pages_scanned += nr_scanned;
1531 if (current_is_kswapd())
1532 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1535 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1539 if (nr_taken == 0) {
1540 spin_unlock_irq(&zone->lru_lock);
1544 update_isolated_counts(mz, sc, &nr_anon, &nr_file, &page_list);
1546 spin_unlock_irq(&zone->lru_lock);
1548 nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
1549 &nr_dirty, &nr_writeback);
1551 /* Check if we should syncronously wait for writeback */
1552 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1553 set_reclaim_mode(priority, sc, true);
1554 nr_reclaimed += shrink_page_list(&page_list, mz, sc,
1555 priority, &nr_dirty, &nr_writeback);
1558 local_irq_disable();
1559 if (current_is_kswapd())
1560 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1561 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1563 putback_lru_pages(mz, sc, nr_anon, nr_file, &page_list);
1566 * If reclaim is isolating dirty pages under writeback, it implies
1567 * that the long-lived page allocation rate is exceeding the page
1568 * laundering rate. Either the global limits are not being effective
1569 * at throttling processes due to the page distribution throughout
1570 * zones or there is heavy usage of a slow backing device. The
1571 * only option is to throttle from reclaim context which is not ideal
1572 * as there is no guarantee the dirtying process is throttled in the
1573 * same way balance_dirty_pages() manages.
1575 * This scales the number of dirty pages that must be under writeback
1576 * before throttling depending on priority. It is a simple backoff
1577 * function that has the most effect in the range DEF_PRIORITY to
1578 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1579 * in trouble and reclaim is considered to be in trouble.
1581 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1582 * DEF_PRIORITY-1 50% must be PageWriteback
1583 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1585 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1586 * isolated page is PageWriteback
1588 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
1589 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1591 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1593 nr_scanned, nr_reclaimed,
1595 trace_shrink_flags(file, sc->reclaim_mode));
1596 return nr_reclaimed;
1600 * This moves pages from the active list to the inactive list.
1602 * We move them the other way if the page is referenced by one or more
1603 * processes, from rmap.
1605 * If the pages are mostly unmapped, the processing is fast and it is
1606 * appropriate to hold zone->lru_lock across the whole operation. But if
1607 * the pages are mapped, the processing is slow (page_referenced()) so we
1608 * should drop zone->lru_lock around each page. It's impossible to balance
1609 * this, so instead we remove the pages from the LRU while processing them.
1610 * It is safe to rely on PG_active against the non-LRU pages in here because
1611 * nobody will play with that bit on a non-LRU page.
1613 * The downside is that we have to touch page->_count against each page.
1614 * But we had to alter page->flags anyway.
1617 static void move_active_pages_to_lru(struct zone *zone,
1618 struct list_head *list,
1621 unsigned long pgmoved = 0;
1622 struct pagevec pvec;
1625 pagevec_init(&pvec, 1);
1627 while (!list_empty(list)) {
1628 struct lruvec *lruvec;
1630 page = lru_to_page(list);
1632 VM_BUG_ON(PageLRU(page));
1635 lruvec = mem_cgroup_lru_add_list(zone, page, lru);
1636 list_move(&page->lru, &lruvec->lists[lru]);
1637 pgmoved += hpage_nr_pages(page);
1639 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1640 spin_unlock_irq(&zone->lru_lock);
1641 if (buffer_heads_over_limit)
1642 pagevec_strip(&pvec);
1643 __pagevec_release(&pvec);
1644 spin_lock_irq(&zone->lru_lock);
1647 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1648 if (!is_active_lru(lru))
1649 __count_vm_events(PGDEACTIVATE, pgmoved);
1652 static void shrink_active_list(unsigned long nr_pages,
1653 struct mem_cgroup_zone *mz,
1654 struct scan_control *sc,
1655 int priority, int file)
1657 unsigned long nr_taken;
1658 unsigned long pgscanned;
1659 unsigned long vm_flags;
1660 LIST_HEAD(l_hold); /* The pages which were snipped off */
1661 LIST_HEAD(l_active);
1662 LIST_HEAD(l_inactive);
1664 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1665 unsigned long nr_rotated = 0;
1666 isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
1667 struct zone *zone = mz->zone;
1672 reclaim_mode |= ISOLATE_UNMAPPED;
1673 if (!sc->may_writepage)
1674 reclaim_mode |= ISOLATE_CLEAN;
1676 spin_lock_irq(&zone->lru_lock);
1678 nr_taken = isolate_pages(nr_pages, mz, &l_hold,
1679 &pgscanned, sc->order,
1680 reclaim_mode, 1, file);
1682 if (global_reclaim(sc))
1683 zone->pages_scanned += pgscanned;
1685 reclaim_stat->recent_scanned[file] += nr_taken;
1687 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1689 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1691 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1692 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1693 spin_unlock_irq(&zone->lru_lock);
1695 while (!list_empty(&l_hold)) {
1697 page = lru_to_page(&l_hold);
1698 list_del(&page->lru);
1700 if (unlikely(!page_evictable(page, NULL))) {
1701 putback_lru_page(page);
1705 if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
1706 nr_rotated += hpage_nr_pages(page);
1708 * Identify referenced, file-backed active pages and
1709 * give them one more trip around the active list. So
1710 * that executable code get better chances to stay in
1711 * memory under moderate memory pressure. Anon pages
1712 * are not likely to be evicted by use-once streaming
1713 * IO, plus JVM can create lots of anon VM_EXEC pages,
1714 * so we ignore them here.
1716 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1717 list_add(&page->lru, &l_active);
1722 ClearPageActive(page); /* we are de-activating */
1723 list_add(&page->lru, &l_inactive);
1727 * Move pages back to the lru list.
1729 spin_lock_irq(&zone->lru_lock);
1731 * Count referenced pages from currently used mappings as rotated,
1732 * even though only some of them are actually re-activated. This
1733 * helps balance scan pressure between file and anonymous pages in
1736 reclaim_stat->recent_rotated[file] += nr_rotated;
1738 move_active_pages_to_lru(zone, &l_active,
1739 LRU_ACTIVE + file * LRU_FILE);
1740 move_active_pages_to_lru(zone, &l_inactive,
1741 LRU_BASE + file * LRU_FILE);
1742 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1743 spin_unlock_irq(&zone->lru_lock);
1747 static int inactive_anon_is_low_global(struct zone *zone)
1749 unsigned long active, inactive;
1751 active = zone_page_state(zone, NR_ACTIVE_ANON);
1752 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1754 if (inactive * zone->inactive_ratio < active)
1761 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1762 * @zone: zone to check
1763 * @sc: scan control of this context
1765 * Returns true if the zone does not have enough inactive anon pages,
1766 * meaning some active anon pages need to be deactivated.
1768 static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1771 * If we don't have swap space, anonymous page deactivation
1774 if (!total_swap_pages)
1777 if (!scanning_global_lru(mz))
1778 return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
1781 return inactive_anon_is_low_global(mz->zone);
1784 static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1790 static int inactive_file_is_low_global(struct zone *zone)
1792 unsigned long active, inactive;
1794 active = zone_page_state(zone, NR_ACTIVE_FILE);
1795 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1797 return (active > inactive);
1801 * inactive_file_is_low - check if file pages need to be deactivated
1802 * @mz: memory cgroup and zone to check
1804 * When the system is doing streaming IO, memory pressure here
1805 * ensures that active file pages get deactivated, until more
1806 * than half of the file pages are on the inactive list.
1808 * Once we get to that situation, protect the system's working
1809 * set from being evicted by disabling active file page aging.
1811 * This uses a different ratio than the anonymous pages, because
1812 * the page cache uses a use-once replacement algorithm.
1814 static int inactive_file_is_low(struct mem_cgroup_zone *mz)
1816 if (!scanning_global_lru(mz))
1817 return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
1820 return inactive_file_is_low_global(mz->zone);
1823 static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file)
1826 return inactive_file_is_low(mz);
1828 return inactive_anon_is_low(mz);
1831 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1832 struct mem_cgroup_zone *mz,
1833 struct scan_control *sc, int priority)
1835 int file = is_file_lru(lru);
1837 if (is_active_lru(lru)) {
1838 if (inactive_list_is_low(mz, file))
1839 shrink_active_list(nr_to_scan, mz, sc, priority, file);
1843 return shrink_inactive_list(nr_to_scan, mz, sc, priority, file);
1846 static int vmscan_swappiness(struct mem_cgroup_zone *mz,
1847 struct scan_control *sc)
1849 if (global_reclaim(sc))
1850 return vm_swappiness;
1851 return mem_cgroup_swappiness(mz->mem_cgroup);
1855 * Determine how aggressively the anon and file LRU lists should be
1856 * scanned. The relative value of each set of LRU lists is determined
1857 * by looking at the fraction of the pages scanned we did rotate back
1858 * onto the active list instead of evict.
1860 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1862 static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
1863 unsigned long *nr, int priority)
1865 unsigned long anon, file, free;
1866 unsigned long anon_prio, file_prio;
1867 unsigned long ap, fp;
1868 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1869 u64 fraction[2], denominator;
1872 bool force_scan = false;
1875 * If the zone or memcg is small, nr[l] can be 0. This
1876 * results in no scanning on this priority and a potential
1877 * priority drop. Global direct reclaim can go to the next
1878 * zone and tends to have no problems. Global kswapd is for
1879 * zone balancing and it needs to scan a minimum amount. When
1880 * reclaiming for a memcg, a priority drop can cause high
1881 * latencies, so it's better to scan a minimum amount there as
1884 if (current_is_kswapd() && mz->zone->all_unreclaimable)
1886 if (!global_reclaim(sc))
1889 /* If we have no swap space, do not bother scanning anon pages. */
1890 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1898 anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) +
1899 zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
1900 file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) +
1901 zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
1903 if (global_reclaim(sc)) {
1904 free = zone_page_state(mz->zone, NR_FREE_PAGES);
1905 /* If we have very few page cache pages,
1906 force-scan anon pages. */
1907 if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
1916 * With swappiness at 100, anonymous and file have the same priority.
1917 * This scanning priority is essentially the inverse of IO cost.
1919 anon_prio = vmscan_swappiness(mz, sc);
1920 file_prio = 200 - vmscan_swappiness(mz, sc);
1923 * OK, so we have swap space and a fair amount of page cache
1924 * pages. We use the recently rotated / recently scanned
1925 * ratios to determine how valuable each cache is.
1927 * Because workloads change over time (and to avoid overflow)
1928 * we keep these statistics as a floating average, which ends
1929 * up weighing recent references more than old ones.
1931 * anon in [0], file in [1]
1933 spin_lock_irq(&mz->zone->lru_lock);
1934 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1935 reclaim_stat->recent_scanned[0] /= 2;
1936 reclaim_stat->recent_rotated[0] /= 2;
1939 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1940 reclaim_stat->recent_scanned[1] /= 2;
1941 reclaim_stat->recent_rotated[1] /= 2;
1945 * The amount of pressure on anon vs file pages is inversely
1946 * proportional to the fraction of recently scanned pages on
1947 * each list that were recently referenced and in active use.
1949 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1950 ap /= reclaim_stat->recent_rotated[0] + 1;
1952 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1953 fp /= reclaim_stat->recent_rotated[1] + 1;
1954 spin_unlock_irq(&mz->zone->lru_lock);
1958 denominator = ap + fp + 1;
1960 for_each_evictable_lru(l) {
1961 int file = is_file_lru(l);
1964 scan = zone_nr_lru_pages(mz, l);
1965 if (priority || noswap) {
1967 if (!scan && force_scan)
1968 scan = SWAP_CLUSTER_MAX;
1969 scan = div64_u64(scan * fraction[file], denominator);
1976 * Reclaim/compaction depends on a number of pages being freed. To avoid
1977 * disruption to the system, a small number of order-0 pages continue to be
1978 * rotated and reclaimed in the normal fashion. However, by the time we get
1979 * back to the allocator and call try_to_compact_zone(), we ensure that
1980 * there are enough free pages for it to be likely successful
1982 static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz,
1983 unsigned long nr_reclaimed,
1984 unsigned long nr_scanned,
1985 struct scan_control *sc)
1987 unsigned long pages_for_compaction;
1988 unsigned long inactive_lru_pages;
1990 /* If not in reclaim/compaction mode, stop */
1991 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1994 /* Consider stopping depending on scan and reclaim activity */
1995 if (sc->gfp_mask & __GFP_REPEAT) {
1997 * For __GFP_REPEAT allocations, stop reclaiming if the
1998 * full LRU list has been scanned and we are still failing
1999 * to reclaim pages. This full LRU scan is potentially
2000 * expensive but a __GFP_REPEAT caller really wants to succeed
2002 if (!nr_reclaimed && !nr_scanned)
2006 * For non-__GFP_REPEAT allocations which can presumably
2007 * fail without consequence, stop if we failed to reclaim
2008 * any pages from the last SWAP_CLUSTER_MAX number of
2009 * pages that were scanned. This will return to the
2010 * caller faster at the risk reclaim/compaction and
2011 * the resulting allocation attempt fails
2018 * If we have not reclaimed enough pages for compaction and the
2019 * inactive lists are large enough, continue reclaiming
2021 pages_for_compaction = (2UL << sc->order);
2022 inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
2023 if (nr_swap_pages > 0)
2024 inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
2025 if (sc->nr_reclaimed < pages_for_compaction &&
2026 inactive_lru_pages > pages_for_compaction)
2029 /* If compaction would go ahead or the allocation would succeed, stop */
2030 switch (compaction_suitable(mz->zone, sc->order)) {
2031 case COMPACT_PARTIAL:
2032 case COMPACT_CONTINUE:
2040 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2042 static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz,
2043 struct scan_control *sc)
2045 unsigned long nr[NR_LRU_LISTS];
2046 unsigned long nr_to_scan;
2048 unsigned long nr_reclaimed, nr_scanned;
2049 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2050 struct blk_plug plug;
2054 nr_scanned = sc->nr_scanned;
2055 get_scan_count(mz, sc, nr, priority);
2057 blk_start_plug(&plug);
2058 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2059 nr[LRU_INACTIVE_FILE]) {
2060 for_each_evictable_lru(l) {
2062 nr_to_scan = min_t(unsigned long,
2063 nr[l], SWAP_CLUSTER_MAX);
2064 nr[l] -= nr_to_scan;
2066 nr_reclaimed += shrink_list(l, nr_to_scan,
2071 * On large memory systems, scan >> priority can become
2072 * really large. This is fine for the starting priority;
2073 * we want to put equal scanning pressure on each zone.
2074 * However, if the VM has a harder time of freeing pages,
2075 * with multiple processes reclaiming pages, the total
2076 * freeing target can get unreasonably large.
2078 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2081 blk_finish_plug(&plug);
2082 sc->nr_reclaimed += nr_reclaimed;
2085 * Even if we did not try to evict anon pages at all, we want to
2086 * rebalance the anon lru active/inactive ratio.
2088 if (inactive_anon_is_low(mz))
2089 shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0);
2091 /* reclaim/compaction might need reclaim to continue */
2092 if (should_continue_reclaim(mz, nr_reclaimed,
2093 sc->nr_scanned - nr_scanned, sc))
2096 throttle_vm_writeout(sc->gfp_mask);
2099 static void shrink_zone(int priority, struct zone *zone,
2100 struct scan_control *sc)
2102 struct mem_cgroup *root = sc->target_mem_cgroup;
2103 struct mem_cgroup_reclaim_cookie reclaim = {
2105 .priority = priority,
2107 struct mem_cgroup *memcg;
2109 memcg = mem_cgroup_iter(root, NULL, &reclaim);
2111 struct mem_cgroup_zone mz = {
2112 .mem_cgroup = memcg,
2116 shrink_mem_cgroup_zone(priority, &mz, sc);
2118 * Limit reclaim has historically picked one memcg and
2119 * scanned it with decreasing priority levels until
2120 * nr_to_reclaim had been reclaimed. This priority
2121 * cycle is thus over after a single memcg.
2123 * Direct reclaim and kswapd, on the other hand, have
2124 * to scan all memory cgroups to fulfill the overall
2125 * scan target for the zone.
2127 if (!global_reclaim(sc)) {
2128 mem_cgroup_iter_break(root, memcg);
2131 memcg = mem_cgroup_iter(root, memcg, &reclaim);
2136 * This is the direct reclaim path, for page-allocating processes. We only
2137 * try to reclaim pages from zones which will satisfy the caller's allocation
2140 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2142 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2144 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2145 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2146 * zone defense algorithm.
2148 * If a zone is deemed to be full of pinned pages then just give it a light
2149 * scan then give up on it.
2151 * This function returns true if a zone is being reclaimed for a costly
2152 * high-order allocation and compaction is either ready to begin or deferred.
2153 * This indicates to the caller that it should retry the allocation or fail.
2155 static bool shrink_zones(int priority, struct zonelist *zonelist,
2156 struct scan_control *sc)
2160 unsigned long nr_soft_reclaimed;
2161 unsigned long nr_soft_scanned;
2162 bool should_abort_reclaim = false;
2164 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2165 gfp_zone(sc->gfp_mask), sc->nodemask) {
2166 if (!populated_zone(zone))
2169 * Take care memory controller reclaiming has small influence
2172 if (global_reclaim(sc)) {
2173 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2175 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2176 continue; /* Let kswapd poll it */
2177 if (COMPACTION_BUILD) {
2179 * If we already have plenty of memory free for
2180 * compaction in this zone, don't free any more.
2181 * Even though compaction is invoked for any
2182 * non-zero order, only frequent costly order
2183 * reclamation is disruptive enough to become a
2184 * noticable problem, like transparent huge page
2187 if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
2188 (compaction_suitable(zone, sc->order) ||
2189 compaction_deferred(zone))) {
2190 should_abort_reclaim = true;
2195 * This steals pages from memory cgroups over softlimit
2196 * and returns the number of reclaimed pages and
2197 * scanned pages. This works for global memory pressure
2198 * and balancing, not for a memcg's limit.
2200 nr_soft_scanned = 0;
2201 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2202 sc->order, sc->gfp_mask,
2204 sc->nr_reclaimed += nr_soft_reclaimed;
2205 sc->nr_scanned += nr_soft_scanned;
2206 /* need some check for avoid more shrink_zone() */
2209 shrink_zone(priority, zone, sc);
2212 return should_abort_reclaim;
2215 static bool zone_reclaimable(struct zone *zone)
2217 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2220 /* All zones in zonelist are unreclaimable? */
2221 static bool all_unreclaimable(struct zonelist *zonelist,
2222 struct scan_control *sc)
2227 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2228 gfp_zone(sc->gfp_mask), sc->nodemask) {
2229 if (!populated_zone(zone))
2231 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2233 if (!zone->all_unreclaimable)
2241 * This is the main entry point to direct page reclaim.
2243 * If a full scan of the inactive list fails to free enough memory then we
2244 * are "out of memory" and something needs to be killed.
2246 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2247 * high - the zone may be full of dirty or under-writeback pages, which this
2248 * caller can't do much about. We kick the writeback threads and take explicit
2249 * naps in the hope that some of these pages can be written. But if the
2250 * allocating task holds filesystem locks which prevent writeout this might not
2251 * work, and the allocation attempt will fail.
2253 * returns: 0, if no pages reclaimed
2254 * else, the number of pages reclaimed
2256 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2257 struct scan_control *sc,
2258 struct shrink_control *shrink)
2261 unsigned long total_scanned = 0;
2262 struct reclaim_state *reclaim_state = current->reclaim_state;
2265 unsigned long writeback_threshold;
2266 bool should_abort_reclaim;
2269 delayacct_freepages_start();
2271 if (global_reclaim(sc))
2272 count_vm_event(ALLOCSTALL);
2274 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2277 disable_swap_token(sc->target_mem_cgroup);
2278 should_abort_reclaim = shrink_zones(priority, zonelist, sc);
2279 if (should_abort_reclaim)
2283 * Don't shrink slabs when reclaiming memory from
2284 * over limit cgroups
2286 if (global_reclaim(sc)) {
2287 unsigned long lru_pages = 0;
2288 for_each_zone_zonelist(zone, z, zonelist,
2289 gfp_zone(sc->gfp_mask)) {
2290 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2293 lru_pages += zone_reclaimable_pages(zone);
2296 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2297 if (reclaim_state) {
2298 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2299 reclaim_state->reclaimed_slab = 0;
2302 total_scanned += sc->nr_scanned;
2303 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2307 * Try to write back as many pages as we just scanned. This
2308 * tends to cause slow streaming writers to write data to the
2309 * disk smoothly, at the dirtying rate, which is nice. But
2310 * that's undesirable in laptop mode, where we *want* lumpy
2311 * writeout. So in laptop mode, write out the whole world.
2313 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2314 if (total_scanned > writeback_threshold) {
2315 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2316 WB_REASON_TRY_TO_FREE_PAGES);
2317 sc->may_writepage = 1;
2320 /* Take a nap, wait for some writeback to complete */
2321 if (!sc->hibernation_mode && sc->nr_scanned &&
2322 priority < DEF_PRIORITY - 2) {
2323 struct zone *preferred_zone;
2325 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2326 &cpuset_current_mems_allowed,
2328 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2333 delayacct_freepages_end();
2336 if (sc->nr_reclaimed)
2337 return sc->nr_reclaimed;
2340 * As hibernation is going on, kswapd is freezed so that it can't mark
2341 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2344 if (oom_killer_disabled)
2347 /* Aborting reclaim to try compaction? don't OOM, then */
2348 if (should_abort_reclaim)
2351 /* top priority shrink_zones still had more to do? don't OOM, then */
2352 if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2358 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2359 gfp_t gfp_mask, nodemask_t *nodemask)
2361 unsigned long nr_reclaimed;
2362 struct scan_control sc = {
2363 .gfp_mask = gfp_mask,
2364 .may_writepage = !laptop_mode,
2365 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2369 .target_mem_cgroup = NULL,
2370 .nodemask = nodemask,
2372 struct shrink_control shrink = {
2373 .gfp_mask = sc.gfp_mask,
2376 trace_mm_vmscan_direct_reclaim_begin(order,
2380 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2382 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2384 return nr_reclaimed;
2387 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2389 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
2390 gfp_t gfp_mask, bool noswap,
2392 unsigned long *nr_scanned)
2394 struct scan_control sc = {
2396 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2397 .may_writepage = !laptop_mode,
2399 .may_swap = !noswap,
2401 .target_mem_cgroup = memcg,
2403 struct mem_cgroup_zone mz = {
2404 .mem_cgroup = memcg,
2408 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2409 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2411 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2416 * NOTE: Although we can get the priority field, using it
2417 * here is not a good idea, since it limits the pages we can scan.
2418 * if we don't reclaim here, the shrink_zone from balance_pgdat
2419 * will pick up pages from other mem cgroup's as well. We hack
2420 * the priority and make it zero.
2422 shrink_mem_cgroup_zone(0, &mz, &sc);
2424 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2426 *nr_scanned = sc.nr_scanned;
2427 return sc.nr_reclaimed;
2430 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
2434 struct zonelist *zonelist;
2435 unsigned long nr_reclaimed;
2437 struct scan_control sc = {
2438 .may_writepage = !laptop_mode,
2440 .may_swap = !noswap,
2441 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2443 .target_mem_cgroup = memcg,
2444 .nodemask = NULL, /* we don't care the placement */
2445 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2446 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2448 struct shrink_control shrink = {
2449 .gfp_mask = sc.gfp_mask,
2453 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2454 * take care of from where we get pages. So the node where we start the
2455 * scan does not need to be the current node.
2457 nid = mem_cgroup_select_victim_node(memcg);
2459 zonelist = NODE_DATA(nid)->node_zonelists;
2461 trace_mm_vmscan_memcg_reclaim_begin(0,
2465 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2467 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2469 return nr_reclaimed;
2473 static void age_active_anon(struct zone *zone, struct scan_control *sc,
2476 struct mem_cgroup *memcg;
2478 if (!total_swap_pages)
2481 memcg = mem_cgroup_iter(NULL, NULL, NULL);
2483 struct mem_cgroup_zone mz = {
2484 .mem_cgroup = memcg,
2488 if (inactive_anon_is_low(&mz))
2489 shrink_active_list(SWAP_CLUSTER_MAX, &mz,
2492 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2497 * pgdat_balanced is used when checking if a node is balanced for high-order
2498 * allocations. Only zones that meet watermarks and are in a zone allowed
2499 * by the callers classzone_idx are added to balanced_pages. The total of
2500 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2501 * for the node to be considered balanced. Forcing all zones to be balanced
2502 * for high orders can cause excessive reclaim when there are imbalanced zones.
2503 * The choice of 25% is due to
2504 * o a 16M DMA zone that is balanced will not balance a zone on any
2505 * reasonable sized machine
2506 * o On all other machines, the top zone must be at least a reasonable
2507 * percentage of the middle zones. For example, on 32-bit x86, highmem
2508 * would need to be at least 256M for it to be balance a whole node.
2509 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2510 * to balance a node on its own. These seemed like reasonable ratios.
2512 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2515 unsigned long present_pages = 0;
2518 for (i = 0; i <= classzone_idx; i++)
2519 present_pages += pgdat->node_zones[i].present_pages;
2521 /* A special case here: if zone has no page, we think it's balanced */
2522 return balanced_pages >= (present_pages >> 2);
2525 /* is kswapd sleeping prematurely? */
2526 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2530 unsigned long balanced = 0;
2531 bool all_zones_ok = true;
2533 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2537 /* Check the watermark levels */
2538 for (i = 0; i <= classzone_idx; i++) {
2539 struct zone *zone = pgdat->node_zones + i;
2541 if (!populated_zone(zone))
2545 * balance_pgdat() skips over all_unreclaimable after
2546 * DEF_PRIORITY. Effectively, it considers them balanced so
2547 * they must be considered balanced here as well if kswapd
2550 if (zone->all_unreclaimable) {
2551 balanced += zone->present_pages;
2555 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2557 all_zones_ok = false;
2559 balanced += zone->present_pages;
2563 * For high-order requests, the balanced zones must contain at least
2564 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2568 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2570 return !all_zones_ok;
2574 * For kswapd, balance_pgdat() will work across all this node's zones until
2575 * they are all at high_wmark_pages(zone).
2577 * Returns the final order kswapd was reclaiming at
2579 * There is special handling here for zones which are full of pinned pages.
2580 * This can happen if the pages are all mlocked, or if they are all used by
2581 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2582 * What we do is to detect the case where all pages in the zone have been
2583 * scanned twice and there has been zero successful reclaim. Mark the zone as
2584 * dead and from now on, only perform a short scan. Basically we're polling
2585 * the zone for when the problem goes away.
2587 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2588 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2589 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2590 * lower zones regardless of the number of free pages in the lower zones. This
2591 * interoperates with the page allocator fallback scheme to ensure that aging
2592 * of pages is balanced across the zones.
2594 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2598 unsigned long balanced;
2601 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2602 unsigned long total_scanned;
2603 struct reclaim_state *reclaim_state = current->reclaim_state;
2604 unsigned long nr_soft_reclaimed;
2605 unsigned long nr_soft_scanned;
2606 struct scan_control sc = {
2607 .gfp_mask = GFP_KERNEL,
2611 * kswapd doesn't want to be bailed out while reclaim. because
2612 * we want to put equal scanning pressure on each zone.
2614 .nr_to_reclaim = ULONG_MAX,
2616 .target_mem_cgroup = NULL,
2618 struct shrink_control shrink = {
2619 .gfp_mask = sc.gfp_mask,
2623 sc.nr_reclaimed = 0;
2624 sc.may_writepage = !laptop_mode;
2625 count_vm_event(PAGEOUTRUN);
2627 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2628 unsigned long lru_pages = 0;
2629 int has_under_min_watermark_zone = 0;
2631 /* The swap token gets in the way of swapout... */
2633 disable_swap_token(NULL);
2639 * Scan in the highmem->dma direction for the highest
2640 * zone which needs scanning
2642 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2643 struct zone *zone = pgdat->node_zones + i;
2645 if (!populated_zone(zone))
2648 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2652 * Do some background aging of the anon list, to give
2653 * pages a chance to be referenced before reclaiming.
2655 age_active_anon(zone, &sc, priority);
2657 if (!zone_watermark_ok_safe(zone, order,
2658 high_wmark_pages(zone), 0, 0)) {
2662 /* If balanced, clear the congested flag */
2663 zone_clear_flag(zone, ZONE_CONGESTED);
2669 for (i = 0; i <= end_zone; i++) {
2670 struct zone *zone = pgdat->node_zones + i;
2672 lru_pages += zone_reclaimable_pages(zone);
2676 * Now scan the zone in the dma->highmem direction, stopping
2677 * at the last zone which needs scanning.
2679 * We do this because the page allocator works in the opposite
2680 * direction. This prevents the page allocator from allocating
2681 * pages behind kswapd's direction of progress, which would
2682 * cause too much scanning of the lower zones.
2684 for (i = 0; i <= end_zone; i++) {
2685 struct zone *zone = pgdat->node_zones + i;
2687 unsigned long balance_gap;
2689 if (!populated_zone(zone))
2692 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2697 nr_soft_scanned = 0;
2699 * Call soft limit reclaim before calling shrink_zone.
2701 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2704 sc.nr_reclaimed += nr_soft_reclaimed;
2705 total_scanned += nr_soft_scanned;
2708 * We put equal pressure on every zone, unless
2709 * one zone has way too many pages free
2710 * already. The "too many pages" is defined
2711 * as the high wmark plus a "gap" where the
2712 * gap is either the low watermark or 1%
2713 * of the zone, whichever is smaller.
2715 balance_gap = min(low_wmark_pages(zone),
2716 (zone->present_pages +
2717 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2718 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2719 if (!zone_watermark_ok_safe(zone, order,
2720 high_wmark_pages(zone) + balance_gap,
2722 shrink_zone(priority, zone, &sc);
2724 reclaim_state->reclaimed_slab = 0;
2725 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2726 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2727 total_scanned += sc.nr_scanned;
2729 if (nr_slab == 0 && !zone_reclaimable(zone))
2730 zone->all_unreclaimable = 1;
2734 * If we've done a decent amount of scanning and
2735 * the reclaim ratio is low, start doing writepage
2736 * even in laptop mode
2738 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2739 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2740 sc.may_writepage = 1;
2742 if (zone->all_unreclaimable) {
2743 if (end_zone && end_zone == i)
2748 if (!zone_watermark_ok_safe(zone, order,
2749 high_wmark_pages(zone), end_zone, 0)) {
2752 * We are still under min water mark. This
2753 * means that we have a GFP_ATOMIC allocation
2754 * failure risk. Hurry up!
2756 if (!zone_watermark_ok_safe(zone, order,
2757 min_wmark_pages(zone), end_zone, 0))
2758 has_under_min_watermark_zone = 1;
2761 * If a zone reaches its high watermark,
2762 * consider it to be no longer congested. It's
2763 * possible there are dirty pages backed by
2764 * congested BDIs but as pressure is relieved,
2765 * spectulatively avoid congestion waits
2767 zone_clear_flag(zone, ZONE_CONGESTED);
2768 if (i <= *classzone_idx)
2769 balanced += zone->present_pages;
2773 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2774 break; /* kswapd: all done */
2776 * OK, kswapd is getting into trouble. Take a nap, then take
2777 * another pass across the zones.
2779 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2780 if (has_under_min_watermark_zone)
2781 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2783 congestion_wait(BLK_RW_ASYNC, HZ/10);
2787 * We do this so kswapd doesn't build up large priorities for
2788 * example when it is freeing in parallel with allocators. It
2789 * matches the direct reclaim path behaviour in terms of impact
2790 * on zone->*_priority.
2792 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2798 * order-0: All zones must meet high watermark for a balanced node
2799 * high-order: Balanced zones must make up at least 25% of the node
2800 * for the node to be balanced
2802 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2808 * Fragmentation may mean that the system cannot be
2809 * rebalanced for high-order allocations in all zones.
2810 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2811 * it means the zones have been fully scanned and are still
2812 * not balanced. For high-order allocations, there is
2813 * little point trying all over again as kswapd may
2816 * Instead, recheck all watermarks at order-0 as they
2817 * are the most important. If watermarks are ok, kswapd will go
2818 * back to sleep. High-order users can still perform direct
2819 * reclaim if they wish.
2821 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2822 order = sc.order = 0;
2828 * If kswapd was reclaiming at a higher order, it has the option of
2829 * sleeping without all zones being balanced. Before it does, it must
2830 * ensure that the watermarks for order-0 on *all* zones are met and
2831 * that the congestion flags are cleared. The congestion flag must
2832 * be cleared as kswapd is the only mechanism that clears the flag
2833 * and it is potentially going to sleep here.
2836 for (i = 0; i <= end_zone; i++) {
2837 struct zone *zone = pgdat->node_zones + i;
2839 if (!populated_zone(zone))
2842 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2845 /* Confirm the zone is balanced for order-0 */
2846 if (!zone_watermark_ok(zone, 0,
2847 high_wmark_pages(zone), 0, 0)) {
2848 order = sc.order = 0;
2852 /* If balanced, clear the congested flag */
2853 zone_clear_flag(zone, ZONE_CONGESTED);
2854 if (i <= *classzone_idx)
2855 balanced += zone->present_pages;
2860 * Return the order we were reclaiming at so sleeping_prematurely()
2861 * makes a decision on the order we were last reclaiming at. However,
2862 * if another caller entered the allocator slow path while kswapd
2863 * was awake, order will remain at the higher level
2865 *classzone_idx = end_zone;
2869 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2874 if (freezing(current) || kthread_should_stop())
2877 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2879 /* Try to sleep for a short interval */
2880 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2881 remaining = schedule_timeout(HZ/10);
2882 finish_wait(&pgdat->kswapd_wait, &wait);
2883 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2887 * After a short sleep, check if it was a premature sleep. If not, then
2888 * go fully to sleep until explicitly woken up.
2890 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2891 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2894 * vmstat counters are not perfectly accurate and the estimated
2895 * value for counters such as NR_FREE_PAGES can deviate from the
2896 * true value by nr_online_cpus * threshold. To avoid the zone
2897 * watermarks being breached while under pressure, we reduce the
2898 * per-cpu vmstat threshold while kswapd is awake and restore
2899 * them before going back to sleep.
2901 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2903 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2906 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2908 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2910 finish_wait(&pgdat->kswapd_wait, &wait);
2914 * The background pageout daemon, started as a kernel thread
2915 * from the init process.
2917 * This basically trickles out pages so that we have _some_
2918 * free memory available even if there is no other activity
2919 * that frees anything up. This is needed for things like routing
2920 * etc, where we otherwise might have all activity going on in
2921 * asynchronous contexts that cannot page things out.
2923 * If there are applications that are active memory-allocators
2924 * (most normal use), this basically shouldn't matter.
2926 static int kswapd(void *p)
2928 unsigned long order, new_order;
2929 unsigned balanced_order;
2930 int classzone_idx, new_classzone_idx;
2931 int balanced_classzone_idx;
2932 pg_data_t *pgdat = (pg_data_t*)p;
2933 struct task_struct *tsk = current;
2935 struct reclaim_state reclaim_state = {
2936 .reclaimed_slab = 0,
2938 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2940 lockdep_set_current_reclaim_state(GFP_KERNEL);
2942 if (!cpumask_empty(cpumask))
2943 set_cpus_allowed_ptr(tsk, cpumask);
2944 current->reclaim_state = &reclaim_state;
2947 * Tell the memory management that we're a "memory allocator",
2948 * and that if we need more memory we should get access to it
2949 * regardless (see "__alloc_pages()"). "kswapd" should
2950 * never get caught in the normal page freeing logic.
2952 * (Kswapd normally doesn't need memory anyway, but sometimes
2953 * you need a small amount of memory in order to be able to
2954 * page out something else, and this flag essentially protects
2955 * us from recursively trying to free more memory as we're
2956 * trying to free the first piece of memory in the first place).
2958 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2961 order = new_order = 0;
2963 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2964 balanced_classzone_idx = classzone_idx;
2969 * If the last balance_pgdat was unsuccessful it's unlikely a
2970 * new request of a similar or harder type will succeed soon
2971 * so consider going to sleep on the basis we reclaimed at
2973 if (balanced_classzone_idx >= new_classzone_idx &&
2974 balanced_order == new_order) {
2975 new_order = pgdat->kswapd_max_order;
2976 new_classzone_idx = pgdat->classzone_idx;
2977 pgdat->kswapd_max_order = 0;
2978 pgdat->classzone_idx = pgdat->nr_zones - 1;
2981 if (order < new_order || classzone_idx > new_classzone_idx) {
2983 * Don't sleep if someone wants a larger 'order'
2984 * allocation or has tigher zone constraints
2987 classzone_idx = new_classzone_idx;
2989 kswapd_try_to_sleep(pgdat, balanced_order,
2990 balanced_classzone_idx);
2991 order = pgdat->kswapd_max_order;
2992 classzone_idx = pgdat->classzone_idx;
2994 new_classzone_idx = classzone_idx;
2995 pgdat->kswapd_max_order = 0;
2996 pgdat->classzone_idx = pgdat->nr_zones - 1;
2999 ret = try_to_freeze();
3000 if (kthread_should_stop())
3004 * We can speed up thawing tasks if we don't call balance_pgdat
3005 * after returning from the refrigerator
3008 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
3009 balanced_classzone_idx = classzone_idx;
3010 balanced_order = balance_pgdat(pgdat, order,
3011 &balanced_classzone_idx);
3018 * A zone is low on free memory, so wake its kswapd task to service it.
3020 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
3024 if (!populated_zone(zone))
3027 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
3029 pgdat = zone->zone_pgdat;
3030 if (pgdat->kswapd_max_order < order) {
3031 pgdat->kswapd_max_order = order;
3032 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
3034 if (!waitqueue_active(&pgdat->kswapd_wait))
3036 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
3039 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
3040 wake_up_interruptible(&pgdat->kswapd_wait);
3044 * The reclaimable count would be mostly accurate.
3045 * The less reclaimable pages may be
3046 * - mlocked pages, which will be moved to unevictable list when encountered
3047 * - mapped pages, which may require several travels to be reclaimed
3048 * - dirty pages, which is not "instantly" reclaimable
3050 unsigned long global_reclaimable_pages(void)
3054 nr = global_page_state(NR_ACTIVE_FILE) +
3055 global_page_state(NR_INACTIVE_FILE);
3057 if (nr_swap_pages > 0)
3058 nr += global_page_state(NR_ACTIVE_ANON) +
3059 global_page_state(NR_INACTIVE_ANON);
3064 unsigned long zone_reclaimable_pages(struct zone *zone)
3068 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
3069 zone_page_state(zone, NR_INACTIVE_FILE);
3071 if (nr_swap_pages > 0)
3072 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
3073 zone_page_state(zone, NR_INACTIVE_ANON);
3078 #ifdef CONFIG_HIBERNATION
3080 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3083 * Rather than trying to age LRUs the aim is to preserve the overall
3084 * LRU order by reclaiming preferentially
3085 * inactive > active > active referenced > active mapped
3087 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
3089 struct reclaim_state reclaim_state;
3090 struct scan_control sc = {
3091 .gfp_mask = GFP_HIGHUSER_MOVABLE,
3095 .nr_to_reclaim = nr_to_reclaim,
3096 .hibernation_mode = 1,
3099 struct shrink_control shrink = {
3100 .gfp_mask = sc.gfp_mask,
3102 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3103 struct task_struct *p = current;
3104 unsigned long nr_reclaimed;
3106 p->flags |= PF_MEMALLOC;
3107 lockdep_set_current_reclaim_state(sc.gfp_mask);
3108 reclaim_state.reclaimed_slab = 0;
3109 p->reclaim_state = &reclaim_state;
3111 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3113 p->reclaim_state = NULL;
3114 lockdep_clear_current_reclaim_state();
3115 p->flags &= ~PF_MEMALLOC;
3117 return nr_reclaimed;
3119 #endif /* CONFIG_HIBERNATION */
3121 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3122 not required for correctness. So if the last cpu in a node goes
3123 away, we get changed to run anywhere: as the first one comes back,
3124 restore their cpu bindings. */
3125 static int __devinit cpu_callback(struct notifier_block *nfb,
3126 unsigned long action, void *hcpu)
3130 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3131 for_each_node_state(nid, N_HIGH_MEMORY) {
3132 pg_data_t *pgdat = NODE_DATA(nid);
3133 const struct cpumask *mask;
3135 mask = cpumask_of_node(pgdat->node_id);
3137 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3138 /* One of our CPUs online: restore mask */
3139 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3146 * This kswapd start function will be called by init and node-hot-add.
3147 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3149 int kswapd_run(int nid)
3151 pg_data_t *pgdat = NODE_DATA(nid);
3157 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3158 if (IS_ERR(pgdat->kswapd)) {
3159 /* failure at boot is fatal */
3160 BUG_ON(system_state == SYSTEM_BOOTING);
3161 printk("Failed to start kswapd on node %d\n",nid);
3168 * Called by memory hotplug when all memory in a node is offlined.
3170 void kswapd_stop(int nid)
3172 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3175 kthread_stop(kswapd);
3178 static int __init kswapd_init(void)
3183 for_each_node_state(nid, N_HIGH_MEMORY)
3185 hotcpu_notifier(cpu_callback, 0);
3189 module_init(kswapd_init)
3195 * If non-zero call zone_reclaim when the number of free pages falls below
3198 int zone_reclaim_mode __read_mostly;
3200 #define RECLAIM_OFF 0
3201 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3202 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3203 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3206 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3207 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3210 #define ZONE_RECLAIM_PRIORITY 4
3213 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3216 int sysctl_min_unmapped_ratio = 1;
3219 * If the number of slab pages in a zone grows beyond this percentage then
3220 * slab reclaim needs to occur.
3222 int sysctl_min_slab_ratio = 5;
3224 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3226 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3227 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3228 zone_page_state(zone, NR_ACTIVE_FILE);
3231 * It's possible for there to be more file mapped pages than
3232 * accounted for by the pages on the file LRU lists because
3233 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3235 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3238 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3239 static long zone_pagecache_reclaimable(struct zone *zone)
3241 long nr_pagecache_reclaimable;
3245 * If RECLAIM_SWAP is set, then all file pages are considered
3246 * potentially reclaimable. Otherwise, we have to worry about
3247 * pages like swapcache and zone_unmapped_file_pages() provides
3250 if (zone_reclaim_mode & RECLAIM_SWAP)
3251 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3253 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3255 /* If we can't clean pages, remove dirty pages from consideration */
3256 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3257 delta += zone_page_state(zone, NR_FILE_DIRTY);
3259 /* Watch for any possible underflows due to delta */
3260 if (unlikely(delta > nr_pagecache_reclaimable))
3261 delta = nr_pagecache_reclaimable;
3263 return nr_pagecache_reclaimable - delta;
3267 * Try to free up some pages from this zone through reclaim.
3269 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3271 /* Minimum pages needed in order to stay on node */
3272 const unsigned long nr_pages = 1 << order;
3273 struct task_struct *p = current;
3274 struct reclaim_state reclaim_state;
3276 struct scan_control sc = {
3277 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3278 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3280 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3282 .gfp_mask = gfp_mask,
3285 struct shrink_control shrink = {
3286 .gfp_mask = sc.gfp_mask,
3288 unsigned long nr_slab_pages0, nr_slab_pages1;
3292 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3293 * and we also need to be able to write out pages for RECLAIM_WRITE
3296 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3297 lockdep_set_current_reclaim_state(gfp_mask);
3298 reclaim_state.reclaimed_slab = 0;
3299 p->reclaim_state = &reclaim_state;
3301 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3303 * Free memory by calling shrink zone with increasing
3304 * priorities until we have enough memory freed.
3306 priority = ZONE_RECLAIM_PRIORITY;
3308 shrink_zone(priority, zone, &sc);
3310 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3313 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3314 if (nr_slab_pages0 > zone->min_slab_pages) {
3316 * shrink_slab() does not currently allow us to determine how
3317 * many pages were freed in this zone. So we take the current
3318 * number of slab pages and shake the slab until it is reduced
3319 * by the same nr_pages that we used for reclaiming unmapped
3322 * Note that shrink_slab will free memory on all zones and may
3326 unsigned long lru_pages = zone_reclaimable_pages(zone);
3328 /* No reclaimable slab or very low memory pressure */
3329 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3332 /* Freed enough memory */
3333 nr_slab_pages1 = zone_page_state(zone,
3334 NR_SLAB_RECLAIMABLE);
3335 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3340 * Update nr_reclaimed by the number of slab pages we
3341 * reclaimed from this zone.
3343 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3344 if (nr_slab_pages1 < nr_slab_pages0)
3345 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3348 p->reclaim_state = NULL;
3349 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3350 lockdep_clear_current_reclaim_state();
3351 return sc.nr_reclaimed >= nr_pages;
3354 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3360 * Zone reclaim reclaims unmapped file backed pages and
3361 * slab pages if we are over the defined limits.
3363 * A small portion of unmapped file backed pages is needed for
3364 * file I/O otherwise pages read by file I/O will be immediately
3365 * thrown out if the zone is overallocated. So we do not reclaim
3366 * if less than a specified percentage of the zone is used by
3367 * unmapped file backed pages.
3369 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3370 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3371 return ZONE_RECLAIM_FULL;
3373 if (zone->all_unreclaimable)
3374 return ZONE_RECLAIM_FULL;
3377 * Do not scan if the allocation should not be delayed.
3379 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3380 return ZONE_RECLAIM_NOSCAN;
3383 * Only run zone reclaim on the local zone or on zones that do not
3384 * have associated processors. This will favor the local processor
3385 * over remote processors and spread off node memory allocations
3386 * as wide as possible.
3388 node_id = zone_to_nid(zone);
3389 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3390 return ZONE_RECLAIM_NOSCAN;
3392 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3393 return ZONE_RECLAIM_NOSCAN;
3395 ret = __zone_reclaim(zone, gfp_mask, order);
3396 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3399 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3406 * page_evictable - test whether a page is evictable
3407 * @page: the page to test
3408 * @vma: the VMA in which the page is or will be mapped, may be NULL
3410 * Test whether page is evictable--i.e., should be placed on active/inactive
3411 * lists vs unevictable list. The vma argument is !NULL when called from the
3412 * fault path to determine how to instantate a new page.
3414 * Reasons page might not be evictable:
3415 * (1) page's mapping marked unevictable
3416 * (2) page is part of an mlocked VMA
3419 int page_evictable(struct page *page, struct vm_area_struct *vma)
3422 if (mapping_unevictable(page_mapping(page)))
3425 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3432 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3433 * @page: page to check evictability and move to appropriate lru list
3434 * @zone: zone page is in
3436 * Checks a page for evictability and moves the page to the appropriate
3439 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3440 * have PageUnevictable set.
3442 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3444 struct lruvec *lruvec;
3446 VM_BUG_ON(PageActive(page));
3448 ClearPageUnevictable(page);
3449 if (page_evictable(page, NULL)) {
3450 enum lru_list l = page_lru_base_type(page);
3452 __dec_zone_state(zone, NR_UNEVICTABLE);
3453 lruvec = mem_cgroup_lru_move_lists(zone, page,
3454 LRU_UNEVICTABLE, l);
3455 list_move(&page->lru, &lruvec->lists[l]);
3456 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3457 __count_vm_event(UNEVICTABLE_PGRESCUED);
3460 * rotate unevictable list
3462 SetPageUnevictable(page);
3463 lruvec = mem_cgroup_lru_move_lists(zone, page, LRU_UNEVICTABLE,
3465 list_move(&page->lru, &lruvec->lists[LRU_UNEVICTABLE]);
3466 if (page_evictable(page, NULL))
3472 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3473 * @mapping: struct address_space to scan for evictable pages
3475 * Scan all pages in mapping. Check unevictable pages for
3476 * evictability and move them to the appropriate zone lru list.
3478 void scan_mapping_unevictable_pages(struct address_space *mapping)
3481 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3484 struct pagevec pvec;
3486 if (mapping->nrpages == 0)
3489 pagevec_init(&pvec, 0);
3490 while (next < end &&
3491 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3497 for (i = 0; i < pagevec_count(&pvec); i++) {
3498 struct page *page = pvec.pages[i];
3499 pgoff_t page_index = page->index;
3500 struct zone *pagezone = page_zone(page);
3503 if (page_index > next)
3507 if (pagezone != zone) {
3509 spin_unlock_irq(&zone->lru_lock);
3511 spin_lock_irq(&zone->lru_lock);
3514 if (PageLRU(page) && PageUnevictable(page))
3515 check_move_unevictable_page(page, zone);
3518 spin_unlock_irq(&zone->lru_lock);
3519 pagevec_release(&pvec);
3521 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3526 static void warn_scan_unevictable_pages(void)
3528 printk_once(KERN_WARNING
3529 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3530 "disabled for lack of a legitimate use case. If you have "
3531 "one, please send an email to linux-mm@kvack.org.\n",
3536 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3537 * all nodes' unevictable lists for evictable pages
3539 unsigned long scan_unevictable_pages;
3541 int scan_unevictable_handler(struct ctl_table *table, int write,
3542 void __user *buffer,
3543 size_t *length, loff_t *ppos)
3545 warn_scan_unevictable_pages();
3546 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3547 scan_unevictable_pages = 0;
3553 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3554 * a specified node's per zone unevictable lists for evictable pages.
3557 static ssize_t read_scan_unevictable_node(struct device *dev,
3558 struct device_attribute *attr,
3561 warn_scan_unevictable_pages();
3562 return sprintf(buf, "0\n"); /* always zero; should fit... */
3565 static ssize_t write_scan_unevictable_node(struct device *dev,
3566 struct device_attribute *attr,
3567 const char *buf, size_t count)
3569 warn_scan_unevictable_pages();
3574 static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3575 read_scan_unevictable_node,
3576 write_scan_unevictable_node);
3578 int scan_unevictable_register_node(struct node *node)
3580 return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3583 void scan_unevictable_unregister_node(struct node *node)
3585 device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);