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 mem_cgroup_lru_del(cursor_page);
1200 list_move(&cursor_page->lru, dst);
1201 nr_taken += hpage_nr_pages(cursor_page);
1203 if (PageDirty(cursor_page))
1208 * Check if the page is freed already.
1210 * We can't use page_count() as that
1211 * requires compound_head and we don't
1212 * have a pin on the page here. If a
1213 * page is tail, we may or may not
1214 * have isolated the head, so assume
1215 * it's not free, it'd be tricky to
1216 * track the head status without a
1219 if (!PageTail(cursor_page) &&
1220 !atomic_read(&cursor_page->_count))
1226 /* If we break out of the loop above, lumpy reclaim failed */
1233 trace_mm_vmscan_lru_isolate(order,
1236 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1241 static unsigned long isolate_pages(unsigned long nr, struct mem_cgroup_zone *mz,
1242 struct list_head *dst,
1243 unsigned long *scanned, int order,
1244 isolate_mode_t mode, int active, int file)
1246 struct lruvec *lruvec;
1249 lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
1254 return isolate_lru_pages(nr, &lruvec->lists[lru], dst,
1255 scanned, order, mode, file);
1259 * clear_active_flags() is a helper for shrink_active_list(), clearing
1260 * any active bits from the pages in the list.
1262 static unsigned long clear_active_flags(struct list_head *page_list,
1263 unsigned int *count)
1269 list_for_each_entry(page, page_list, lru) {
1270 int numpages = hpage_nr_pages(page);
1271 lru = page_lru_base_type(page);
1272 if (PageActive(page)) {
1274 ClearPageActive(page);
1275 nr_active += numpages;
1278 count[lru] += numpages;
1285 * isolate_lru_page - tries to isolate a page from its LRU list
1286 * @page: page to isolate from its LRU list
1288 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1289 * vmstat statistic corresponding to whatever LRU list the page was on.
1291 * Returns 0 if the page was removed from an LRU list.
1292 * Returns -EBUSY if the page was not on an LRU list.
1294 * The returned page will have PageLRU() cleared. If it was found on
1295 * the active list, it will have PageActive set. If it was found on
1296 * the unevictable list, it will have the PageUnevictable bit set. That flag
1297 * may need to be cleared by the caller before letting the page go.
1299 * The vmstat statistic corresponding to the list on which the page was
1300 * found will be decremented.
1303 * (1) Must be called with an elevated refcount on the page. This is a
1304 * fundamentnal difference from isolate_lru_pages (which is called
1305 * without a stable reference).
1306 * (2) the lru_lock must not be held.
1307 * (3) interrupts must be enabled.
1309 int isolate_lru_page(struct page *page)
1313 VM_BUG_ON(!page_count(page));
1315 if (PageLRU(page)) {
1316 struct zone *zone = page_zone(page);
1318 spin_lock_irq(&zone->lru_lock);
1319 if (PageLRU(page)) {
1320 int lru = page_lru(page);
1325 del_page_from_lru_list(zone, page, lru);
1327 spin_unlock_irq(&zone->lru_lock);
1333 * Are there way too many processes in the direct reclaim path already?
1335 static int too_many_isolated(struct zone *zone, int file,
1336 struct scan_control *sc)
1338 unsigned long inactive, isolated;
1340 if (current_is_kswapd())
1343 if (!global_reclaim(sc))
1347 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1348 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1350 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1351 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1354 return isolated > inactive;
1358 * TODO: Try merging with migrations version of putback_lru_pages
1360 static noinline_for_stack void
1361 putback_lru_pages(struct mem_cgroup_zone *mz, struct scan_control *sc,
1362 unsigned long nr_anon, unsigned long nr_file,
1363 struct list_head *page_list)
1366 struct pagevec pvec;
1367 struct zone *zone = mz->zone;
1368 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1370 pagevec_init(&pvec, 1);
1373 * Put back any unfreeable pages.
1375 spin_lock(&zone->lru_lock);
1376 while (!list_empty(page_list)) {
1378 page = lru_to_page(page_list);
1379 VM_BUG_ON(PageLRU(page));
1380 list_del(&page->lru);
1381 if (unlikely(!page_evictable(page, NULL))) {
1382 spin_unlock_irq(&zone->lru_lock);
1383 putback_lru_page(page);
1384 spin_lock_irq(&zone->lru_lock);
1388 lru = page_lru(page);
1389 add_page_to_lru_list(zone, page, lru);
1390 if (is_active_lru(lru)) {
1391 int file = is_file_lru(lru);
1392 int numpages = hpage_nr_pages(page);
1393 reclaim_stat->recent_rotated[file] += numpages;
1395 if (!pagevec_add(&pvec, page)) {
1396 spin_unlock_irq(&zone->lru_lock);
1397 __pagevec_release(&pvec);
1398 spin_lock_irq(&zone->lru_lock);
1401 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1402 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1404 spin_unlock_irq(&zone->lru_lock);
1405 pagevec_release(&pvec);
1408 static noinline_for_stack void
1409 update_isolated_counts(struct mem_cgroup_zone *mz,
1410 struct scan_control *sc,
1411 unsigned long *nr_anon,
1412 unsigned long *nr_file,
1413 struct list_head *isolated_list)
1415 unsigned long nr_active;
1416 struct zone *zone = mz->zone;
1417 unsigned int count[NR_LRU_LISTS] = { 0, };
1418 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1420 nr_active = clear_active_flags(isolated_list, count);
1421 __count_vm_events(PGDEACTIVATE, nr_active);
1423 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1424 -count[LRU_ACTIVE_FILE]);
1425 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1426 -count[LRU_INACTIVE_FILE]);
1427 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1428 -count[LRU_ACTIVE_ANON]);
1429 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1430 -count[LRU_INACTIVE_ANON]);
1432 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1433 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1434 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1435 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1437 reclaim_stat->recent_scanned[0] += *nr_anon;
1438 reclaim_stat->recent_scanned[1] += *nr_file;
1442 * Returns true if a direct reclaim should wait on pages under writeback.
1444 * If we are direct reclaiming for contiguous pages and we do not reclaim
1445 * everything in the list, try again and wait for writeback IO to complete.
1446 * This will stall high-order allocations noticeably. Only do that when really
1447 * need to free the pages under high memory pressure.
1449 static inline bool should_reclaim_stall(unsigned long nr_taken,
1450 unsigned long nr_freed,
1452 struct scan_control *sc)
1454 int lumpy_stall_priority;
1456 /* kswapd should not stall on sync IO */
1457 if (current_is_kswapd())
1460 /* Only stall on lumpy reclaim */
1461 if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
1464 /* If we have reclaimed everything on the isolated list, no stall */
1465 if (nr_freed == nr_taken)
1469 * For high-order allocations, there are two stall thresholds.
1470 * High-cost allocations stall immediately where as lower
1471 * order allocations such as stacks require the scanning
1472 * priority to be much higher before stalling.
1474 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1475 lumpy_stall_priority = DEF_PRIORITY;
1477 lumpy_stall_priority = DEF_PRIORITY / 3;
1479 return priority <= lumpy_stall_priority;
1483 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1484 * of reclaimed pages
1486 static noinline_for_stack unsigned long
1487 shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
1488 struct scan_control *sc, int priority, int file)
1490 LIST_HEAD(page_list);
1491 unsigned long nr_scanned;
1492 unsigned long nr_reclaimed = 0;
1493 unsigned long nr_taken;
1494 unsigned long nr_anon;
1495 unsigned long nr_file;
1496 unsigned long nr_dirty = 0;
1497 unsigned long nr_writeback = 0;
1498 isolate_mode_t reclaim_mode = ISOLATE_INACTIVE;
1499 struct zone *zone = mz->zone;
1501 while (unlikely(too_many_isolated(zone, file, sc))) {
1502 congestion_wait(BLK_RW_ASYNC, HZ/10);
1504 /* We are about to die and free our memory. Return now. */
1505 if (fatal_signal_pending(current))
1506 return SWAP_CLUSTER_MAX;
1509 set_reclaim_mode(priority, sc, false);
1510 if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
1511 reclaim_mode |= ISOLATE_ACTIVE;
1516 reclaim_mode |= ISOLATE_UNMAPPED;
1517 if (!sc->may_writepage)
1518 reclaim_mode |= ISOLATE_CLEAN;
1520 spin_lock_irq(&zone->lru_lock);
1522 nr_taken = isolate_pages(nr_to_scan, mz, &page_list,
1523 &nr_scanned, sc->order,
1524 reclaim_mode, 0, file);
1525 if (global_reclaim(sc)) {
1526 zone->pages_scanned += nr_scanned;
1527 if (current_is_kswapd())
1528 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1531 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1535 if (nr_taken == 0) {
1536 spin_unlock_irq(&zone->lru_lock);
1540 update_isolated_counts(mz, sc, &nr_anon, &nr_file, &page_list);
1542 spin_unlock_irq(&zone->lru_lock);
1544 nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
1545 &nr_dirty, &nr_writeback);
1547 /* Check if we should syncronously wait for writeback */
1548 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1549 set_reclaim_mode(priority, sc, true);
1550 nr_reclaimed += shrink_page_list(&page_list, mz, sc,
1551 priority, &nr_dirty, &nr_writeback);
1554 local_irq_disable();
1555 if (current_is_kswapd())
1556 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1557 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1559 putback_lru_pages(mz, sc, nr_anon, nr_file, &page_list);
1562 * If reclaim is isolating dirty pages under writeback, it implies
1563 * that the long-lived page allocation rate is exceeding the page
1564 * laundering rate. Either the global limits are not being effective
1565 * at throttling processes due to the page distribution throughout
1566 * zones or there is heavy usage of a slow backing device. The
1567 * only option is to throttle from reclaim context which is not ideal
1568 * as there is no guarantee the dirtying process is throttled in the
1569 * same way balance_dirty_pages() manages.
1571 * This scales the number of dirty pages that must be under writeback
1572 * before throttling depending on priority. It is a simple backoff
1573 * function that has the most effect in the range DEF_PRIORITY to
1574 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1575 * in trouble and reclaim is considered to be in trouble.
1577 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1578 * DEF_PRIORITY-1 50% must be PageWriteback
1579 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1581 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1582 * isolated page is PageWriteback
1584 if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
1585 wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
1587 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1589 nr_scanned, nr_reclaimed,
1591 trace_shrink_flags(file, sc->reclaim_mode));
1592 return nr_reclaimed;
1596 * This moves pages from the active list to the inactive list.
1598 * We move them the other way if the page is referenced by one or more
1599 * processes, from rmap.
1601 * If the pages are mostly unmapped, the processing is fast and it is
1602 * appropriate to hold zone->lru_lock across the whole operation. But if
1603 * the pages are mapped, the processing is slow (page_referenced()) so we
1604 * should drop zone->lru_lock around each page. It's impossible to balance
1605 * this, so instead we remove the pages from the LRU while processing them.
1606 * It is safe to rely on PG_active against the non-LRU pages in here because
1607 * nobody will play with that bit on a non-LRU page.
1609 * The downside is that we have to touch page->_count against each page.
1610 * But we had to alter page->flags anyway.
1613 static void move_active_pages_to_lru(struct zone *zone,
1614 struct list_head *list,
1617 unsigned long pgmoved = 0;
1618 struct pagevec pvec;
1621 pagevec_init(&pvec, 1);
1623 while (!list_empty(list)) {
1624 struct lruvec *lruvec;
1626 page = lru_to_page(list);
1628 VM_BUG_ON(PageLRU(page));
1631 lruvec = mem_cgroup_lru_add_list(zone, page, lru);
1632 list_move(&page->lru, &lruvec->lists[lru]);
1633 pgmoved += hpage_nr_pages(page);
1635 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1636 spin_unlock_irq(&zone->lru_lock);
1637 if (buffer_heads_over_limit)
1638 pagevec_strip(&pvec);
1639 __pagevec_release(&pvec);
1640 spin_lock_irq(&zone->lru_lock);
1643 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1644 if (!is_active_lru(lru))
1645 __count_vm_events(PGDEACTIVATE, pgmoved);
1648 static void shrink_active_list(unsigned long nr_pages,
1649 struct mem_cgroup_zone *mz,
1650 struct scan_control *sc,
1651 int priority, int file)
1653 unsigned long nr_taken;
1654 unsigned long pgscanned;
1655 unsigned long vm_flags;
1656 LIST_HEAD(l_hold); /* The pages which were snipped off */
1657 LIST_HEAD(l_active);
1658 LIST_HEAD(l_inactive);
1660 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1661 unsigned long nr_rotated = 0;
1662 isolate_mode_t reclaim_mode = ISOLATE_ACTIVE;
1663 struct zone *zone = mz->zone;
1668 reclaim_mode |= ISOLATE_UNMAPPED;
1669 if (!sc->may_writepage)
1670 reclaim_mode |= ISOLATE_CLEAN;
1672 spin_lock_irq(&zone->lru_lock);
1674 nr_taken = isolate_pages(nr_pages, mz, &l_hold,
1675 &pgscanned, sc->order,
1676 reclaim_mode, 1, file);
1678 if (global_reclaim(sc))
1679 zone->pages_scanned += pgscanned;
1681 reclaim_stat->recent_scanned[file] += nr_taken;
1683 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1685 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1687 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1688 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1689 spin_unlock_irq(&zone->lru_lock);
1691 while (!list_empty(&l_hold)) {
1693 page = lru_to_page(&l_hold);
1694 list_del(&page->lru);
1696 if (unlikely(!page_evictable(page, NULL))) {
1697 putback_lru_page(page);
1701 if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
1702 nr_rotated += hpage_nr_pages(page);
1704 * Identify referenced, file-backed active pages and
1705 * give them one more trip around the active list. So
1706 * that executable code get better chances to stay in
1707 * memory under moderate memory pressure. Anon pages
1708 * are not likely to be evicted by use-once streaming
1709 * IO, plus JVM can create lots of anon VM_EXEC pages,
1710 * so we ignore them here.
1712 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1713 list_add(&page->lru, &l_active);
1718 ClearPageActive(page); /* we are de-activating */
1719 list_add(&page->lru, &l_inactive);
1723 * Move pages back to the lru list.
1725 spin_lock_irq(&zone->lru_lock);
1727 * Count referenced pages from currently used mappings as rotated,
1728 * even though only some of them are actually re-activated. This
1729 * helps balance scan pressure between file and anonymous pages in
1732 reclaim_stat->recent_rotated[file] += nr_rotated;
1734 move_active_pages_to_lru(zone, &l_active,
1735 LRU_ACTIVE + file * LRU_FILE);
1736 move_active_pages_to_lru(zone, &l_inactive,
1737 LRU_BASE + file * LRU_FILE);
1738 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1739 spin_unlock_irq(&zone->lru_lock);
1743 static int inactive_anon_is_low_global(struct zone *zone)
1745 unsigned long active, inactive;
1747 active = zone_page_state(zone, NR_ACTIVE_ANON);
1748 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1750 if (inactive * zone->inactive_ratio < active)
1757 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1758 * @zone: zone to check
1759 * @sc: scan control of this context
1761 * Returns true if the zone does not have enough inactive anon pages,
1762 * meaning some active anon pages need to be deactivated.
1764 static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1767 * If we don't have swap space, anonymous page deactivation
1770 if (!total_swap_pages)
1773 if (!scanning_global_lru(mz))
1774 return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
1777 return inactive_anon_is_low_global(mz->zone);
1780 static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz)
1786 static int inactive_file_is_low_global(struct zone *zone)
1788 unsigned long active, inactive;
1790 active = zone_page_state(zone, NR_ACTIVE_FILE);
1791 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1793 return (active > inactive);
1797 * inactive_file_is_low - check if file pages need to be deactivated
1798 * @mz: memory cgroup and zone to check
1800 * When the system is doing streaming IO, memory pressure here
1801 * ensures that active file pages get deactivated, until more
1802 * than half of the file pages are on the inactive list.
1804 * Once we get to that situation, protect the system's working
1805 * set from being evicted by disabling active file page aging.
1807 * This uses a different ratio than the anonymous pages, because
1808 * the page cache uses a use-once replacement algorithm.
1810 static int inactive_file_is_low(struct mem_cgroup_zone *mz)
1812 if (!scanning_global_lru(mz))
1813 return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
1816 return inactive_file_is_low_global(mz->zone);
1819 static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file)
1822 return inactive_file_is_low(mz);
1824 return inactive_anon_is_low(mz);
1827 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1828 struct mem_cgroup_zone *mz,
1829 struct scan_control *sc, int priority)
1831 int file = is_file_lru(lru);
1833 if (is_active_lru(lru)) {
1834 if (inactive_list_is_low(mz, file))
1835 shrink_active_list(nr_to_scan, mz, sc, priority, file);
1839 return shrink_inactive_list(nr_to_scan, mz, sc, priority, file);
1842 static int vmscan_swappiness(struct mem_cgroup_zone *mz,
1843 struct scan_control *sc)
1845 if (global_reclaim(sc))
1846 return vm_swappiness;
1847 return mem_cgroup_swappiness(mz->mem_cgroup);
1851 * Determine how aggressively the anon and file LRU lists should be
1852 * scanned. The relative value of each set of LRU lists is determined
1853 * by looking at the fraction of the pages scanned we did rotate back
1854 * onto the active list instead of evict.
1856 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1858 static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
1859 unsigned long *nr, int priority)
1861 unsigned long anon, file, free;
1862 unsigned long anon_prio, file_prio;
1863 unsigned long ap, fp;
1864 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
1865 u64 fraction[2], denominator;
1868 bool force_scan = false;
1871 * If the zone or memcg is small, nr[l] can be 0. This
1872 * results in no scanning on this priority and a potential
1873 * priority drop. Global direct reclaim can go to the next
1874 * zone and tends to have no problems. Global kswapd is for
1875 * zone balancing and it needs to scan a minimum amount. When
1876 * reclaiming for a memcg, a priority drop can cause high
1877 * latencies, so it's better to scan a minimum amount there as
1880 if (current_is_kswapd() && mz->zone->all_unreclaimable)
1882 if (!global_reclaim(sc))
1885 /* If we have no swap space, do not bother scanning anon pages. */
1886 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1894 anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) +
1895 zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
1896 file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) +
1897 zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
1899 if (global_reclaim(sc)) {
1900 free = zone_page_state(mz->zone, NR_FREE_PAGES);
1901 /* If we have very few page cache pages,
1902 force-scan anon pages. */
1903 if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
1912 * With swappiness at 100, anonymous and file have the same priority.
1913 * This scanning priority is essentially the inverse of IO cost.
1915 anon_prio = vmscan_swappiness(mz, sc);
1916 file_prio = 200 - vmscan_swappiness(mz, sc);
1919 * OK, so we have swap space and a fair amount of page cache
1920 * pages. We use the recently rotated / recently scanned
1921 * ratios to determine how valuable each cache is.
1923 * Because workloads change over time (and to avoid overflow)
1924 * we keep these statistics as a floating average, which ends
1925 * up weighing recent references more than old ones.
1927 * anon in [0], file in [1]
1929 spin_lock_irq(&mz->zone->lru_lock);
1930 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1931 reclaim_stat->recent_scanned[0] /= 2;
1932 reclaim_stat->recent_rotated[0] /= 2;
1935 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1936 reclaim_stat->recent_scanned[1] /= 2;
1937 reclaim_stat->recent_rotated[1] /= 2;
1941 * The amount of pressure on anon vs file pages is inversely
1942 * proportional to the fraction of recently scanned pages on
1943 * each list that were recently referenced and in active use.
1945 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1946 ap /= reclaim_stat->recent_rotated[0] + 1;
1948 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1949 fp /= reclaim_stat->recent_rotated[1] + 1;
1950 spin_unlock_irq(&mz->zone->lru_lock);
1954 denominator = ap + fp + 1;
1956 for_each_evictable_lru(l) {
1957 int file = is_file_lru(l);
1960 scan = zone_nr_lru_pages(mz, l);
1961 if (priority || noswap) {
1963 if (!scan && force_scan)
1964 scan = SWAP_CLUSTER_MAX;
1965 scan = div64_u64(scan * fraction[file], denominator);
1972 * Reclaim/compaction depends on a number of pages being freed. To avoid
1973 * disruption to the system, a small number of order-0 pages continue to be
1974 * rotated and reclaimed in the normal fashion. However, by the time we get
1975 * back to the allocator and call try_to_compact_zone(), we ensure that
1976 * there are enough free pages for it to be likely successful
1978 static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz,
1979 unsigned long nr_reclaimed,
1980 unsigned long nr_scanned,
1981 struct scan_control *sc)
1983 unsigned long pages_for_compaction;
1984 unsigned long inactive_lru_pages;
1986 /* If not in reclaim/compaction mode, stop */
1987 if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
1990 /* Consider stopping depending on scan and reclaim activity */
1991 if (sc->gfp_mask & __GFP_REPEAT) {
1993 * For __GFP_REPEAT allocations, stop reclaiming if the
1994 * full LRU list has been scanned and we are still failing
1995 * to reclaim pages. This full LRU scan is potentially
1996 * expensive but a __GFP_REPEAT caller really wants to succeed
1998 if (!nr_reclaimed && !nr_scanned)
2002 * For non-__GFP_REPEAT allocations which can presumably
2003 * fail without consequence, stop if we failed to reclaim
2004 * any pages from the last SWAP_CLUSTER_MAX number of
2005 * pages that were scanned. This will return to the
2006 * caller faster at the risk reclaim/compaction and
2007 * the resulting allocation attempt fails
2014 * If we have not reclaimed enough pages for compaction and the
2015 * inactive lists are large enough, continue reclaiming
2017 pages_for_compaction = (2UL << sc->order);
2018 inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
2019 if (nr_swap_pages > 0)
2020 inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
2021 if (sc->nr_reclaimed < pages_for_compaction &&
2022 inactive_lru_pages > pages_for_compaction)
2025 /* If compaction would go ahead or the allocation would succeed, stop */
2026 switch (compaction_suitable(mz->zone, sc->order)) {
2027 case COMPACT_PARTIAL:
2028 case COMPACT_CONTINUE:
2036 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
2038 static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz,
2039 struct scan_control *sc)
2041 unsigned long nr[NR_LRU_LISTS];
2042 unsigned long nr_to_scan;
2044 unsigned long nr_reclaimed, nr_scanned;
2045 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
2046 struct blk_plug plug;
2050 nr_scanned = sc->nr_scanned;
2051 get_scan_count(mz, sc, nr, priority);
2053 blk_start_plug(&plug);
2054 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
2055 nr[LRU_INACTIVE_FILE]) {
2056 for_each_evictable_lru(l) {
2058 nr_to_scan = min_t(unsigned long,
2059 nr[l], SWAP_CLUSTER_MAX);
2060 nr[l] -= nr_to_scan;
2062 nr_reclaimed += shrink_list(l, nr_to_scan,
2067 * On large memory systems, scan >> priority can become
2068 * really large. This is fine for the starting priority;
2069 * we want to put equal scanning pressure on each zone.
2070 * However, if the VM has a harder time of freeing pages,
2071 * with multiple processes reclaiming pages, the total
2072 * freeing target can get unreasonably large.
2074 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
2077 blk_finish_plug(&plug);
2078 sc->nr_reclaimed += nr_reclaimed;
2081 * Even if we did not try to evict anon pages at all, we want to
2082 * rebalance the anon lru active/inactive ratio.
2084 if (inactive_anon_is_low(mz))
2085 shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0);
2087 /* reclaim/compaction might need reclaim to continue */
2088 if (should_continue_reclaim(mz, nr_reclaimed,
2089 sc->nr_scanned - nr_scanned, sc))
2092 throttle_vm_writeout(sc->gfp_mask);
2095 static void shrink_zone(int priority, struct zone *zone,
2096 struct scan_control *sc)
2098 struct mem_cgroup *root = sc->target_mem_cgroup;
2099 struct mem_cgroup_reclaim_cookie reclaim = {
2101 .priority = priority,
2103 struct mem_cgroup *memcg;
2105 memcg = mem_cgroup_iter(root, NULL, &reclaim);
2107 struct mem_cgroup_zone mz = {
2108 .mem_cgroup = memcg,
2112 shrink_mem_cgroup_zone(priority, &mz, sc);
2114 * Limit reclaim has historically picked one memcg and
2115 * scanned it with decreasing priority levels until
2116 * nr_to_reclaim had been reclaimed. This priority
2117 * cycle is thus over after a single memcg.
2119 * Direct reclaim and kswapd, on the other hand, have
2120 * to scan all memory cgroups to fulfill the overall
2121 * scan target for the zone.
2123 if (!global_reclaim(sc)) {
2124 mem_cgroup_iter_break(root, memcg);
2127 memcg = mem_cgroup_iter(root, memcg, &reclaim);
2132 * This is the direct reclaim path, for page-allocating processes. We only
2133 * try to reclaim pages from zones which will satisfy the caller's allocation
2136 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2138 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2140 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2141 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2142 * zone defense algorithm.
2144 * If a zone is deemed to be full of pinned pages then just give it a light
2145 * scan then give up on it.
2147 * This function returns true if a zone is being reclaimed for a costly
2148 * high-order allocation and compaction is either ready to begin or deferred.
2149 * This indicates to the caller that it should retry the allocation or fail.
2151 static bool shrink_zones(int priority, struct zonelist *zonelist,
2152 struct scan_control *sc)
2156 unsigned long nr_soft_reclaimed;
2157 unsigned long nr_soft_scanned;
2158 bool should_abort_reclaim = false;
2160 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2161 gfp_zone(sc->gfp_mask), sc->nodemask) {
2162 if (!populated_zone(zone))
2165 * Take care memory controller reclaiming has small influence
2168 if (global_reclaim(sc)) {
2169 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2171 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2172 continue; /* Let kswapd poll it */
2173 if (COMPACTION_BUILD) {
2175 * If we already have plenty of memory free for
2176 * compaction in this zone, don't free any more.
2177 * Even though compaction is invoked for any
2178 * non-zero order, only frequent costly order
2179 * reclamation is disruptive enough to become a
2180 * noticable problem, like transparent huge page
2183 if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
2184 (compaction_suitable(zone, sc->order) ||
2185 compaction_deferred(zone))) {
2186 should_abort_reclaim = true;
2191 * This steals pages from memory cgroups over softlimit
2192 * and returns the number of reclaimed pages and
2193 * scanned pages. This works for global memory pressure
2194 * and balancing, not for a memcg's limit.
2196 nr_soft_scanned = 0;
2197 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2198 sc->order, sc->gfp_mask,
2200 sc->nr_reclaimed += nr_soft_reclaimed;
2201 sc->nr_scanned += nr_soft_scanned;
2202 /* need some check for avoid more shrink_zone() */
2205 shrink_zone(priority, zone, sc);
2208 return should_abort_reclaim;
2211 static bool zone_reclaimable(struct zone *zone)
2213 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
2216 /* All zones in zonelist are unreclaimable? */
2217 static bool all_unreclaimable(struct zonelist *zonelist,
2218 struct scan_control *sc)
2223 for_each_zone_zonelist_nodemask(zone, z, zonelist,
2224 gfp_zone(sc->gfp_mask), sc->nodemask) {
2225 if (!populated_zone(zone))
2227 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2229 if (!zone->all_unreclaimable)
2237 * This is the main entry point to direct page reclaim.
2239 * If a full scan of the inactive list fails to free enough memory then we
2240 * are "out of memory" and something needs to be killed.
2242 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2243 * high - the zone may be full of dirty or under-writeback pages, which this
2244 * caller can't do much about. We kick the writeback threads and take explicit
2245 * naps in the hope that some of these pages can be written. But if the
2246 * allocating task holds filesystem locks which prevent writeout this might not
2247 * work, and the allocation attempt will fail.
2249 * returns: 0, if no pages reclaimed
2250 * else, the number of pages reclaimed
2252 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
2253 struct scan_control *sc,
2254 struct shrink_control *shrink)
2257 unsigned long total_scanned = 0;
2258 struct reclaim_state *reclaim_state = current->reclaim_state;
2261 unsigned long writeback_threshold;
2264 delayacct_freepages_start();
2266 if (global_reclaim(sc))
2267 count_vm_event(ALLOCSTALL);
2269 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2272 disable_swap_token(sc->target_mem_cgroup);
2273 if (shrink_zones(priority, zonelist, sc))
2277 * Don't shrink slabs when reclaiming memory from
2278 * over limit cgroups
2280 if (global_reclaim(sc)) {
2281 unsigned long lru_pages = 0;
2282 for_each_zone_zonelist(zone, z, zonelist,
2283 gfp_zone(sc->gfp_mask)) {
2284 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2287 lru_pages += zone_reclaimable_pages(zone);
2290 shrink_slab(shrink, sc->nr_scanned, lru_pages);
2291 if (reclaim_state) {
2292 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
2293 reclaim_state->reclaimed_slab = 0;
2296 total_scanned += sc->nr_scanned;
2297 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
2301 * Try to write back as many pages as we just scanned. This
2302 * tends to cause slow streaming writers to write data to the
2303 * disk smoothly, at the dirtying rate, which is nice. But
2304 * that's undesirable in laptop mode, where we *want* lumpy
2305 * writeout. So in laptop mode, write out the whole world.
2307 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
2308 if (total_scanned > writeback_threshold) {
2309 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
2310 WB_REASON_TRY_TO_FREE_PAGES);
2311 sc->may_writepage = 1;
2314 /* Take a nap, wait for some writeback to complete */
2315 if (!sc->hibernation_mode && sc->nr_scanned &&
2316 priority < DEF_PRIORITY - 2) {
2317 struct zone *preferred_zone;
2319 first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
2320 &cpuset_current_mems_allowed,
2322 wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
2327 delayacct_freepages_end();
2330 if (sc->nr_reclaimed)
2331 return sc->nr_reclaimed;
2334 * As hibernation is going on, kswapd is freezed so that it can't mark
2335 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2338 if (oom_killer_disabled)
2341 /* top priority shrink_zones still had more to do? don't OOM, then */
2342 if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
2348 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
2349 gfp_t gfp_mask, nodemask_t *nodemask)
2351 unsigned long nr_reclaimed;
2352 struct scan_control sc = {
2353 .gfp_mask = gfp_mask,
2354 .may_writepage = !laptop_mode,
2355 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2359 .target_mem_cgroup = NULL,
2360 .nodemask = nodemask,
2362 struct shrink_control shrink = {
2363 .gfp_mask = sc.gfp_mask,
2366 trace_mm_vmscan_direct_reclaim_begin(order,
2370 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2372 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2374 return nr_reclaimed;
2377 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2379 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2380 gfp_t gfp_mask, bool noswap,
2382 unsigned long *nr_scanned)
2384 struct scan_control sc = {
2386 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2387 .may_writepage = !laptop_mode,
2389 .may_swap = !noswap,
2391 .target_mem_cgroup = mem,
2393 struct mem_cgroup_zone mz = {
2398 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2399 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2401 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2406 * NOTE: Although we can get the priority field, using it
2407 * here is not a good idea, since it limits the pages we can scan.
2408 * if we don't reclaim here, the shrink_zone from balance_pgdat
2409 * will pick up pages from other mem cgroup's as well. We hack
2410 * the priority and make it zero.
2412 shrink_mem_cgroup_zone(0, &mz, &sc);
2414 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2416 *nr_scanned = sc.nr_scanned;
2417 return sc.nr_reclaimed;
2420 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2424 struct zonelist *zonelist;
2425 unsigned long nr_reclaimed;
2427 struct scan_control sc = {
2428 .may_writepage = !laptop_mode,
2430 .may_swap = !noswap,
2431 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2433 .target_mem_cgroup = mem_cont,
2434 .nodemask = NULL, /* we don't care the placement */
2435 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2436 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
2438 struct shrink_control shrink = {
2439 .gfp_mask = sc.gfp_mask,
2443 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2444 * take care of from where we get pages. So the node where we start the
2445 * scan does not need to be the current node.
2447 nid = mem_cgroup_select_victim_node(mem_cont);
2449 zonelist = NODE_DATA(nid)->node_zonelists;
2451 trace_mm_vmscan_memcg_reclaim_begin(0,
2455 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
2457 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2459 return nr_reclaimed;
2463 static void age_active_anon(struct zone *zone, struct scan_control *sc,
2466 struct mem_cgroup *memcg;
2468 if (!total_swap_pages)
2471 memcg = mem_cgroup_iter(NULL, NULL, NULL);
2473 struct mem_cgroup_zone mz = {
2474 .mem_cgroup = memcg,
2478 if (inactive_anon_is_low(&mz))
2479 shrink_active_list(SWAP_CLUSTER_MAX, &mz,
2482 memcg = mem_cgroup_iter(NULL, memcg, NULL);
2487 * pgdat_balanced is used when checking if a node is balanced for high-order
2488 * allocations. Only zones that meet watermarks and are in a zone allowed
2489 * by the callers classzone_idx are added to balanced_pages. The total of
2490 * balanced pages must be at least 25% of the zones allowed by classzone_idx
2491 * for the node to be considered balanced. Forcing all zones to be balanced
2492 * for high orders can cause excessive reclaim when there are imbalanced zones.
2493 * The choice of 25% is due to
2494 * o a 16M DMA zone that is balanced will not balance a zone on any
2495 * reasonable sized machine
2496 * o On all other machines, the top zone must be at least a reasonable
2497 * percentage of the middle zones. For example, on 32-bit x86, highmem
2498 * would need to be at least 256M for it to be balance a whole node.
2499 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2500 * to balance a node on its own. These seemed like reasonable ratios.
2502 static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
2505 unsigned long present_pages = 0;
2508 for (i = 0; i <= classzone_idx; i++)
2509 present_pages += pgdat->node_zones[i].present_pages;
2511 /* A special case here: if zone has no page, we think it's balanced */
2512 return balanced_pages >= (present_pages >> 2);
2515 /* is kswapd sleeping prematurely? */
2516 static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
2520 unsigned long balanced = 0;
2521 bool all_zones_ok = true;
2523 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2527 /* Check the watermark levels */
2528 for (i = 0; i <= classzone_idx; i++) {
2529 struct zone *zone = pgdat->node_zones + i;
2531 if (!populated_zone(zone))
2535 * balance_pgdat() skips over all_unreclaimable after
2536 * DEF_PRIORITY. Effectively, it considers them balanced so
2537 * they must be considered balanced here as well if kswapd
2540 if (zone->all_unreclaimable) {
2541 balanced += zone->present_pages;
2545 if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone),
2547 all_zones_ok = false;
2549 balanced += zone->present_pages;
2553 * For high-order requests, the balanced zones must contain at least
2554 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
2558 return !pgdat_balanced(pgdat, balanced, classzone_idx);
2560 return !all_zones_ok;
2564 * For kswapd, balance_pgdat() will work across all this node's zones until
2565 * they are all at high_wmark_pages(zone).
2567 * Returns the final order kswapd was reclaiming at
2569 * There is special handling here for zones which are full of pinned pages.
2570 * This can happen if the pages are all mlocked, or if they are all used by
2571 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2572 * What we do is to detect the case where all pages in the zone have been
2573 * scanned twice and there has been zero successful reclaim. Mark the zone as
2574 * dead and from now on, only perform a short scan. Basically we're polling
2575 * the zone for when the problem goes away.
2577 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2578 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2579 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2580 * lower zones regardless of the number of free pages in the lower zones. This
2581 * interoperates with the page allocator fallback scheme to ensure that aging
2582 * of pages is balanced across the zones.
2584 static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
2588 unsigned long balanced;
2591 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2592 unsigned long total_scanned;
2593 struct reclaim_state *reclaim_state = current->reclaim_state;
2594 unsigned long nr_soft_reclaimed;
2595 unsigned long nr_soft_scanned;
2596 struct scan_control sc = {
2597 .gfp_mask = GFP_KERNEL,
2601 * kswapd doesn't want to be bailed out while reclaim. because
2602 * we want to put equal scanning pressure on each zone.
2604 .nr_to_reclaim = ULONG_MAX,
2606 .target_mem_cgroup = NULL,
2608 struct shrink_control shrink = {
2609 .gfp_mask = sc.gfp_mask,
2613 sc.nr_reclaimed = 0;
2614 sc.may_writepage = !laptop_mode;
2615 count_vm_event(PAGEOUTRUN);
2617 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2618 unsigned long lru_pages = 0;
2619 int has_under_min_watermark_zone = 0;
2621 /* The swap token gets in the way of swapout... */
2623 disable_swap_token(NULL);
2629 * Scan in the highmem->dma direction for the highest
2630 * zone which needs scanning
2632 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2633 struct zone *zone = pgdat->node_zones + i;
2635 if (!populated_zone(zone))
2638 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2642 * Do some background aging of the anon list, to give
2643 * pages a chance to be referenced before reclaiming.
2645 age_active_anon(zone, &sc, priority);
2647 if (!zone_watermark_ok_safe(zone, order,
2648 high_wmark_pages(zone), 0, 0)) {
2652 /* If balanced, clear the congested flag */
2653 zone_clear_flag(zone, ZONE_CONGESTED);
2659 for (i = 0; i <= end_zone; i++) {
2660 struct zone *zone = pgdat->node_zones + i;
2662 lru_pages += zone_reclaimable_pages(zone);
2666 * Now scan the zone in the dma->highmem direction, stopping
2667 * at the last zone which needs scanning.
2669 * We do this because the page allocator works in the opposite
2670 * direction. This prevents the page allocator from allocating
2671 * pages behind kswapd's direction of progress, which would
2672 * cause too much scanning of the lower zones.
2674 for (i = 0; i <= end_zone; i++) {
2675 struct zone *zone = pgdat->node_zones + i;
2677 unsigned long balance_gap;
2679 if (!populated_zone(zone))
2682 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2687 nr_soft_scanned = 0;
2689 * Call soft limit reclaim before calling shrink_zone.
2691 nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
2694 sc.nr_reclaimed += nr_soft_reclaimed;
2695 total_scanned += nr_soft_scanned;
2698 * We put equal pressure on every zone, unless
2699 * one zone has way too many pages free
2700 * already. The "too many pages" is defined
2701 * as the high wmark plus a "gap" where the
2702 * gap is either the low watermark or 1%
2703 * of the zone, whichever is smaller.
2705 balance_gap = min(low_wmark_pages(zone),
2706 (zone->present_pages +
2707 KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
2708 KSWAPD_ZONE_BALANCE_GAP_RATIO);
2709 if (!zone_watermark_ok_safe(zone, order,
2710 high_wmark_pages(zone) + balance_gap,
2712 shrink_zone(priority, zone, &sc);
2714 reclaim_state->reclaimed_slab = 0;
2715 nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
2716 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2717 total_scanned += sc.nr_scanned;
2719 if (nr_slab == 0 && !zone_reclaimable(zone))
2720 zone->all_unreclaimable = 1;
2724 * If we've done a decent amount of scanning and
2725 * the reclaim ratio is low, start doing writepage
2726 * even in laptop mode
2728 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2729 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2730 sc.may_writepage = 1;
2732 if (zone->all_unreclaimable) {
2733 if (end_zone && end_zone == i)
2738 if (!zone_watermark_ok_safe(zone, order,
2739 high_wmark_pages(zone), end_zone, 0)) {
2742 * We are still under min water mark. This
2743 * means that we have a GFP_ATOMIC allocation
2744 * failure risk. Hurry up!
2746 if (!zone_watermark_ok_safe(zone, order,
2747 min_wmark_pages(zone), end_zone, 0))
2748 has_under_min_watermark_zone = 1;
2751 * If a zone reaches its high watermark,
2752 * consider it to be no longer congested. It's
2753 * possible there are dirty pages backed by
2754 * congested BDIs but as pressure is relieved,
2755 * spectulatively avoid congestion waits
2757 zone_clear_flag(zone, ZONE_CONGESTED);
2758 if (i <= *classzone_idx)
2759 balanced += zone->present_pages;
2763 if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
2764 break; /* kswapd: all done */
2766 * OK, kswapd is getting into trouble. Take a nap, then take
2767 * another pass across the zones.
2769 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2770 if (has_under_min_watermark_zone)
2771 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2773 congestion_wait(BLK_RW_ASYNC, HZ/10);
2777 * We do this so kswapd doesn't build up large priorities for
2778 * example when it is freeing in parallel with allocators. It
2779 * matches the direct reclaim path behaviour in terms of impact
2780 * on zone->*_priority.
2782 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2788 * order-0: All zones must meet high watermark for a balanced node
2789 * high-order: Balanced zones must make up at least 25% of the node
2790 * for the node to be balanced
2792 if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
2798 * Fragmentation may mean that the system cannot be
2799 * rebalanced for high-order allocations in all zones.
2800 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2801 * it means the zones have been fully scanned and are still
2802 * not balanced. For high-order allocations, there is
2803 * little point trying all over again as kswapd may
2806 * Instead, recheck all watermarks at order-0 as they
2807 * are the most important. If watermarks are ok, kswapd will go
2808 * back to sleep. High-order users can still perform direct
2809 * reclaim if they wish.
2811 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2812 order = sc.order = 0;
2818 * If kswapd was reclaiming at a higher order, it has the option of
2819 * sleeping without all zones being balanced. Before it does, it must
2820 * ensure that the watermarks for order-0 on *all* zones are met and
2821 * that the congestion flags are cleared. The congestion flag must
2822 * be cleared as kswapd is the only mechanism that clears the flag
2823 * and it is potentially going to sleep here.
2826 for (i = 0; i <= end_zone; i++) {
2827 struct zone *zone = pgdat->node_zones + i;
2829 if (!populated_zone(zone))
2832 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2835 /* Confirm the zone is balanced for order-0 */
2836 if (!zone_watermark_ok(zone, 0,
2837 high_wmark_pages(zone), 0, 0)) {
2838 order = sc.order = 0;
2842 /* If balanced, clear the congested flag */
2843 zone_clear_flag(zone, ZONE_CONGESTED);
2844 if (i <= *classzone_idx)
2845 balanced += zone->present_pages;
2850 * Return the order we were reclaiming at so sleeping_prematurely()
2851 * makes a decision on the order we were last reclaiming at. However,
2852 * if another caller entered the allocator slow path while kswapd
2853 * was awake, order will remain at the higher level
2855 *classzone_idx = end_zone;
2859 static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
2864 if (freezing(current) || kthread_should_stop())
2867 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2869 /* Try to sleep for a short interval */
2870 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2871 remaining = schedule_timeout(HZ/10);
2872 finish_wait(&pgdat->kswapd_wait, &wait);
2873 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2877 * After a short sleep, check if it was a premature sleep. If not, then
2878 * go fully to sleep until explicitly woken up.
2880 if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
2881 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2884 * vmstat counters are not perfectly accurate and the estimated
2885 * value for counters such as NR_FREE_PAGES can deviate from the
2886 * true value by nr_online_cpus * threshold. To avoid the zone
2887 * watermarks being breached while under pressure, we reduce the
2888 * per-cpu vmstat threshold while kswapd is awake and restore
2889 * them before going back to sleep.
2891 set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
2893 set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
2896 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2898 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2900 finish_wait(&pgdat->kswapd_wait, &wait);
2904 * The background pageout daemon, started as a kernel thread
2905 * from the init process.
2907 * This basically trickles out pages so that we have _some_
2908 * free memory available even if there is no other activity
2909 * that frees anything up. This is needed for things like routing
2910 * etc, where we otherwise might have all activity going on in
2911 * asynchronous contexts that cannot page things out.
2913 * If there are applications that are active memory-allocators
2914 * (most normal use), this basically shouldn't matter.
2916 static int kswapd(void *p)
2918 unsigned long order, new_order;
2919 unsigned balanced_order;
2920 int classzone_idx, new_classzone_idx;
2921 int balanced_classzone_idx;
2922 pg_data_t *pgdat = (pg_data_t*)p;
2923 struct task_struct *tsk = current;
2925 struct reclaim_state reclaim_state = {
2926 .reclaimed_slab = 0,
2928 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2930 lockdep_set_current_reclaim_state(GFP_KERNEL);
2932 if (!cpumask_empty(cpumask))
2933 set_cpus_allowed_ptr(tsk, cpumask);
2934 current->reclaim_state = &reclaim_state;
2937 * Tell the memory management that we're a "memory allocator",
2938 * and that if we need more memory we should get access to it
2939 * regardless (see "__alloc_pages()"). "kswapd" should
2940 * never get caught in the normal page freeing logic.
2942 * (Kswapd normally doesn't need memory anyway, but sometimes
2943 * you need a small amount of memory in order to be able to
2944 * page out something else, and this flag essentially protects
2945 * us from recursively trying to free more memory as we're
2946 * trying to free the first piece of memory in the first place).
2948 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2951 order = new_order = 0;
2953 classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
2954 balanced_classzone_idx = classzone_idx;
2959 * If the last balance_pgdat was unsuccessful it's unlikely a
2960 * new request of a similar or harder type will succeed soon
2961 * so consider going to sleep on the basis we reclaimed at
2963 if (balanced_classzone_idx >= new_classzone_idx &&
2964 balanced_order == new_order) {
2965 new_order = pgdat->kswapd_max_order;
2966 new_classzone_idx = pgdat->classzone_idx;
2967 pgdat->kswapd_max_order = 0;
2968 pgdat->classzone_idx = pgdat->nr_zones - 1;
2971 if (order < new_order || classzone_idx > new_classzone_idx) {
2973 * Don't sleep if someone wants a larger 'order'
2974 * allocation or has tigher zone constraints
2977 classzone_idx = new_classzone_idx;
2979 kswapd_try_to_sleep(pgdat, balanced_order,
2980 balanced_classzone_idx);
2981 order = pgdat->kswapd_max_order;
2982 classzone_idx = pgdat->classzone_idx;
2984 new_classzone_idx = classzone_idx;
2985 pgdat->kswapd_max_order = 0;
2986 pgdat->classzone_idx = pgdat->nr_zones - 1;
2989 ret = try_to_freeze();
2990 if (kthread_should_stop())
2994 * We can speed up thawing tasks if we don't call balance_pgdat
2995 * after returning from the refrigerator
2998 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2999 balanced_classzone_idx = classzone_idx;
3000 balanced_order = balance_pgdat(pgdat, order,
3001 &balanced_classzone_idx);
3008 * A zone is low on free memory, so wake its kswapd task to service it.
3010 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
3014 if (!populated_zone(zone))
3017 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
3019 pgdat = zone->zone_pgdat;
3020 if (pgdat->kswapd_max_order < order) {
3021 pgdat->kswapd_max_order = order;
3022 pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
3024 if (!waitqueue_active(&pgdat->kswapd_wait))
3026 if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
3029 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
3030 wake_up_interruptible(&pgdat->kswapd_wait);
3034 * The reclaimable count would be mostly accurate.
3035 * The less reclaimable pages may be
3036 * - mlocked pages, which will be moved to unevictable list when encountered
3037 * - mapped pages, which may require several travels to be reclaimed
3038 * - dirty pages, which is not "instantly" reclaimable
3040 unsigned long global_reclaimable_pages(void)
3044 nr = global_page_state(NR_ACTIVE_FILE) +
3045 global_page_state(NR_INACTIVE_FILE);
3047 if (nr_swap_pages > 0)
3048 nr += global_page_state(NR_ACTIVE_ANON) +
3049 global_page_state(NR_INACTIVE_ANON);
3054 unsigned long zone_reclaimable_pages(struct zone *zone)
3058 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
3059 zone_page_state(zone, NR_INACTIVE_FILE);
3061 if (nr_swap_pages > 0)
3062 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
3063 zone_page_state(zone, NR_INACTIVE_ANON);
3068 #ifdef CONFIG_HIBERNATION
3070 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3073 * Rather than trying to age LRUs the aim is to preserve the overall
3074 * LRU order by reclaiming preferentially
3075 * inactive > active > active referenced > active mapped
3077 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
3079 struct reclaim_state reclaim_state;
3080 struct scan_control sc = {
3081 .gfp_mask = GFP_HIGHUSER_MOVABLE,
3085 .nr_to_reclaim = nr_to_reclaim,
3086 .hibernation_mode = 1,
3089 struct shrink_control shrink = {
3090 .gfp_mask = sc.gfp_mask,
3092 struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
3093 struct task_struct *p = current;
3094 unsigned long nr_reclaimed;
3096 p->flags |= PF_MEMALLOC;
3097 lockdep_set_current_reclaim_state(sc.gfp_mask);
3098 reclaim_state.reclaimed_slab = 0;
3099 p->reclaim_state = &reclaim_state;
3101 nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
3103 p->reclaim_state = NULL;
3104 lockdep_clear_current_reclaim_state();
3105 p->flags &= ~PF_MEMALLOC;
3107 return nr_reclaimed;
3109 #endif /* CONFIG_HIBERNATION */
3111 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3112 not required for correctness. So if the last cpu in a node goes
3113 away, we get changed to run anywhere: as the first one comes back,
3114 restore their cpu bindings. */
3115 static int __devinit cpu_callback(struct notifier_block *nfb,
3116 unsigned long action, void *hcpu)
3120 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
3121 for_each_node_state(nid, N_HIGH_MEMORY) {
3122 pg_data_t *pgdat = NODE_DATA(nid);
3123 const struct cpumask *mask;
3125 mask = cpumask_of_node(pgdat->node_id);
3127 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
3128 /* One of our CPUs online: restore mask */
3129 set_cpus_allowed_ptr(pgdat->kswapd, mask);
3136 * This kswapd start function will be called by init and node-hot-add.
3137 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3139 int kswapd_run(int nid)
3141 pg_data_t *pgdat = NODE_DATA(nid);
3147 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
3148 if (IS_ERR(pgdat->kswapd)) {
3149 /* failure at boot is fatal */
3150 BUG_ON(system_state == SYSTEM_BOOTING);
3151 printk("Failed to start kswapd on node %d\n",nid);
3158 * Called by memory hotplug when all memory in a node is offlined.
3160 void kswapd_stop(int nid)
3162 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
3165 kthread_stop(kswapd);
3168 static int __init kswapd_init(void)
3173 for_each_node_state(nid, N_HIGH_MEMORY)
3175 hotcpu_notifier(cpu_callback, 0);
3179 module_init(kswapd_init)
3185 * If non-zero call zone_reclaim when the number of free pages falls below
3188 int zone_reclaim_mode __read_mostly;
3190 #define RECLAIM_OFF 0
3191 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3192 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3193 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3196 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3197 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3200 #define ZONE_RECLAIM_PRIORITY 4
3203 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3206 int sysctl_min_unmapped_ratio = 1;
3209 * If the number of slab pages in a zone grows beyond this percentage then
3210 * slab reclaim needs to occur.
3212 int sysctl_min_slab_ratio = 5;
3214 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
3216 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
3217 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
3218 zone_page_state(zone, NR_ACTIVE_FILE);
3221 * It's possible for there to be more file mapped pages than
3222 * accounted for by the pages on the file LRU lists because
3223 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3225 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
3228 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3229 static long zone_pagecache_reclaimable(struct zone *zone)
3231 long nr_pagecache_reclaimable;
3235 * If RECLAIM_SWAP is set, then all file pages are considered
3236 * potentially reclaimable. Otherwise, we have to worry about
3237 * pages like swapcache and zone_unmapped_file_pages() provides
3240 if (zone_reclaim_mode & RECLAIM_SWAP)
3241 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
3243 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
3245 /* If we can't clean pages, remove dirty pages from consideration */
3246 if (!(zone_reclaim_mode & RECLAIM_WRITE))
3247 delta += zone_page_state(zone, NR_FILE_DIRTY);
3249 /* Watch for any possible underflows due to delta */
3250 if (unlikely(delta > nr_pagecache_reclaimable))
3251 delta = nr_pagecache_reclaimable;
3253 return nr_pagecache_reclaimable - delta;
3257 * Try to free up some pages from this zone through reclaim.
3259 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3261 /* Minimum pages needed in order to stay on node */
3262 const unsigned long nr_pages = 1 << order;
3263 struct task_struct *p = current;
3264 struct reclaim_state reclaim_state;
3266 struct scan_control sc = {
3267 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
3268 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
3270 .nr_to_reclaim = max_t(unsigned long, nr_pages,
3272 .gfp_mask = gfp_mask,
3275 struct shrink_control shrink = {
3276 .gfp_mask = sc.gfp_mask,
3278 unsigned long nr_slab_pages0, nr_slab_pages1;
3282 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3283 * and we also need to be able to write out pages for RECLAIM_WRITE
3286 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
3287 lockdep_set_current_reclaim_state(gfp_mask);
3288 reclaim_state.reclaimed_slab = 0;
3289 p->reclaim_state = &reclaim_state;
3291 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
3293 * Free memory by calling shrink zone with increasing
3294 * priorities until we have enough memory freed.
3296 priority = ZONE_RECLAIM_PRIORITY;
3298 shrink_zone(priority, zone, &sc);
3300 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
3303 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3304 if (nr_slab_pages0 > zone->min_slab_pages) {
3306 * shrink_slab() does not currently allow us to determine how
3307 * many pages were freed in this zone. So we take the current
3308 * number of slab pages and shake the slab until it is reduced
3309 * by the same nr_pages that we used for reclaiming unmapped
3312 * Note that shrink_slab will free memory on all zones and may
3316 unsigned long lru_pages = zone_reclaimable_pages(zone);
3318 /* No reclaimable slab or very low memory pressure */
3319 if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
3322 /* Freed enough memory */
3323 nr_slab_pages1 = zone_page_state(zone,
3324 NR_SLAB_RECLAIMABLE);
3325 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
3330 * Update nr_reclaimed by the number of slab pages we
3331 * reclaimed from this zone.
3333 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
3334 if (nr_slab_pages1 < nr_slab_pages0)
3335 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
3338 p->reclaim_state = NULL;
3339 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
3340 lockdep_clear_current_reclaim_state();
3341 return sc.nr_reclaimed >= nr_pages;
3344 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
3350 * Zone reclaim reclaims unmapped file backed pages and
3351 * slab pages if we are over the defined limits.
3353 * A small portion of unmapped file backed pages is needed for
3354 * file I/O otherwise pages read by file I/O will be immediately
3355 * thrown out if the zone is overallocated. So we do not reclaim
3356 * if less than a specified percentage of the zone is used by
3357 * unmapped file backed pages.
3359 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
3360 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
3361 return ZONE_RECLAIM_FULL;
3363 if (zone->all_unreclaimable)
3364 return ZONE_RECLAIM_FULL;
3367 * Do not scan if the allocation should not be delayed.
3369 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
3370 return ZONE_RECLAIM_NOSCAN;
3373 * Only run zone reclaim on the local zone or on zones that do not
3374 * have associated processors. This will favor the local processor
3375 * over remote processors and spread off node memory allocations
3376 * as wide as possible.
3378 node_id = zone_to_nid(zone);
3379 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
3380 return ZONE_RECLAIM_NOSCAN;
3382 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
3383 return ZONE_RECLAIM_NOSCAN;
3385 ret = __zone_reclaim(zone, gfp_mask, order);
3386 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
3389 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
3396 * page_evictable - test whether a page is evictable
3397 * @page: the page to test
3398 * @vma: the VMA in which the page is or will be mapped, may be NULL
3400 * Test whether page is evictable--i.e., should be placed on active/inactive
3401 * lists vs unevictable list. The vma argument is !NULL when called from the
3402 * fault path to determine how to instantate a new page.
3404 * Reasons page might not be evictable:
3405 * (1) page's mapping marked unevictable
3406 * (2) page is part of an mlocked VMA
3409 int page_evictable(struct page *page, struct vm_area_struct *vma)
3412 if (mapping_unevictable(page_mapping(page)))
3415 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
3422 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
3423 * @page: page to check evictability and move to appropriate lru list
3424 * @zone: zone page is in
3426 * Checks a page for evictability and moves the page to the appropriate
3429 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
3430 * have PageUnevictable set.
3432 static void check_move_unevictable_page(struct page *page, struct zone *zone)
3434 struct lruvec *lruvec;
3436 VM_BUG_ON(PageActive(page));
3438 ClearPageUnevictable(page);
3439 if (page_evictable(page, NULL)) {
3440 enum lru_list l = page_lru_base_type(page);
3442 __dec_zone_state(zone, NR_UNEVICTABLE);
3443 lruvec = mem_cgroup_lru_move_lists(zone, page,
3444 LRU_UNEVICTABLE, l);
3445 list_move(&page->lru, &lruvec->lists[l]);
3446 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
3447 __count_vm_event(UNEVICTABLE_PGRESCUED);
3450 * rotate unevictable list
3452 SetPageUnevictable(page);
3453 lruvec = mem_cgroup_lru_move_lists(zone, page, LRU_UNEVICTABLE,
3455 list_move(&page->lru, &lruvec->lists[LRU_UNEVICTABLE]);
3456 if (page_evictable(page, NULL))
3462 * scan_mapping_unevictable_pages - scan an address space for evictable pages
3463 * @mapping: struct address_space to scan for evictable pages
3465 * Scan all pages in mapping. Check unevictable pages for
3466 * evictability and move them to the appropriate zone lru list.
3468 void scan_mapping_unevictable_pages(struct address_space *mapping)
3471 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
3474 struct pagevec pvec;
3476 if (mapping->nrpages == 0)
3479 pagevec_init(&pvec, 0);
3480 while (next < end &&
3481 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
3487 for (i = 0; i < pagevec_count(&pvec); i++) {
3488 struct page *page = pvec.pages[i];
3489 pgoff_t page_index = page->index;
3490 struct zone *pagezone = page_zone(page);
3493 if (page_index > next)
3497 if (pagezone != zone) {
3499 spin_unlock_irq(&zone->lru_lock);
3501 spin_lock_irq(&zone->lru_lock);
3504 if (PageLRU(page) && PageUnevictable(page))
3505 check_move_unevictable_page(page, zone);
3508 spin_unlock_irq(&zone->lru_lock);
3509 pagevec_release(&pvec);
3511 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
3516 static void warn_scan_unevictable_pages(void)
3518 printk_once(KERN_WARNING
3519 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3520 "disabled for lack of a legitimate use case. If you have "
3521 "one, please send an email to linux-mm@kvack.org.\n",
3526 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3527 * all nodes' unevictable lists for evictable pages
3529 unsigned long scan_unevictable_pages;
3531 int scan_unevictable_handler(struct ctl_table *table, int write,
3532 void __user *buffer,
3533 size_t *length, loff_t *ppos)
3535 warn_scan_unevictable_pages();
3536 proc_doulongvec_minmax(table, write, buffer, length, ppos);
3537 scan_unevictable_pages = 0;
3543 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3544 * a specified node's per zone unevictable lists for evictable pages.
3547 static ssize_t read_scan_unevictable_node(struct device *dev,
3548 struct device_attribute *attr,
3551 warn_scan_unevictable_pages();
3552 return sprintf(buf, "0\n"); /* always zero; should fit... */
3555 static ssize_t write_scan_unevictable_node(struct device *dev,
3556 struct device_attribute *attr,
3557 const char *buf, size_t count)
3559 warn_scan_unevictable_pages();
3564 static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3565 read_scan_unevictable_node,
3566 write_scan_unevictable_node);
3568 int scan_unevictable_register_node(struct node *node)
3570 return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
3573 void scan_unevictable_unregister_node(struct node *node)
3575 device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);