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/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/vmscan.h>
55 /* Incremented by the number of inactive pages that were scanned */
56 unsigned long nr_scanned;
58 /* Number of pages freed so far during a call to shrink_zones() */
59 unsigned long nr_reclaimed;
61 /* How many pages shrink_list() should reclaim */
62 unsigned long nr_to_reclaim;
64 unsigned long hibernation_mode;
66 /* This context's GFP mask */
71 /* Can mapped pages be reclaimed? */
74 /* Can pages be swapped as part of reclaim? */
82 * Intend to reclaim enough continuous memory rather than reclaim
83 * enough amount of memory. i.e, mode for high order allocation.
85 bool lumpy_reclaim_mode;
87 /* Which cgroup do we reclaim from */
88 struct mem_cgroup *mem_cgroup;
91 * Nodemask of nodes allowed by the caller. If NULL, all nodes
97 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99 #ifdef ARCH_HAS_PREFETCH
100 #define prefetch_prev_lru_page(_page, _base, _field) \
102 if ((_page)->lru.prev != _base) { \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
110 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113 #ifdef ARCH_HAS_PREFETCHW
114 #define prefetchw_prev_lru_page(_page, _base, _field) \
116 if ((_page)->lru.prev != _base) { \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
124 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
128 * From 0 .. 100. Higher means more swappy.
130 int vm_swappiness = 60;
131 long vm_total_pages; /* The total number of pages which the VM controls */
133 static LIST_HEAD(shrinker_list);
134 static DECLARE_RWSEM(shrinker_rwsem);
136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
137 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
139 #define scanning_global_lru(sc) (1)
142 static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone,
143 struct scan_control *sc)
145 if (!scanning_global_lru(sc))
146 return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone);
148 return &zone->reclaim_stat;
151 static unsigned long zone_nr_lru_pages(struct zone *zone,
152 struct scan_control *sc, enum lru_list lru)
154 if (!scanning_global_lru(sc))
155 return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru);
157 return zone_page_state(zone, NR_LRU_BASE + lru);
162 * Add a shrinker callback to be called from the vm
164 void register_shrinker(struct shrinker *shrinker)
167 down_write(&shrinker_rwsem);
168 list_add_tail(&shrinker->list, &shrinker_list);
169 up_write(&shrinker_rwsem);
171 EXPORT_SYMBOL(register_shrinker);
176 void unregister_shrinker(struct shrinker *shrinker)
178 down_write(&shrinker_rwsem);
179 list_del(&shrinker->list);
180 up_write(&shrinker_rwsem);
182 EXPORT_SYMBOL(unregister_shrinker);
184 #define SHRINK_BATCH 128
186 * Call the shrink functions to age shrinkable caches
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
193 * If the vm encountered mapped pages on the LRU it increase the pressure on
194 * slab to avoid swapping.
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
202 * Returns the number of slab objects which we shrunk.
204 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
205 unsigned long lru_pages)
207 struct shrinker *shrinker;
208 unsigned long ret = 0;
211 scanned = SWAP_CLUSTER_MAX;
213 if (!down_read_trylock(&shrinker_rwsem))
214 return 1; /* Assume we'll be able to shrink next time */
216 list_for_each_entry(shrinker, &shrinker_list, list) {
217 unsigned long long delta;
218 unsigned long total_scan;
219 unsigned long max_pass;
221 max_pass = (*shrinker->shrink)(shrinker, 0, gfp_mask);
222 delta = (4 * scanned) / shrinker->seeks;
224 do_div(delta, lru_pages + 1);
225 shrinker->nr += delta;
226 if (shrinker->nr < 0) {
227 printk(KERN_ERR "shrink_slab: %pF negative objects to "
229 shrinker->shrink, shrinker->nr);
230 shrinker->nr = max_pass;
234 * Avoid risking looping forever due to too large nr value:
235 * never try to free more than twice the estimate number of
238 if (shrinker->nr > max_pass * 2)
239 shrinker->nr = max_pass * 2;
241 total_scan = shrinker->nr;
244 while (total_scan >= SHRINK_BATCH) {
245 long this_scan = SHRINK_BATCH;
249 nr_before = (*shrinker->shrink)(shrinker, 0, gfp_mask);
250 shrink_ret = (*shrinker->shrink)(shrinker, this_scan,
252 if (shrink_ret == -1)
254 if (shrink_ret < nr_before)
255 ret += nr_before - shrink_ret;
256 count_vm_events(SLABS_SCANNED, this_scan);
257 total_scan -= this_scan;
262 shrinker->nr += total_scan;
264 up_read(&shrinker_rwsem);
268 static inline int is_page_cache_freeable(struct page *page)
271 * A freeable page cache page is referenced only by the caller
272 * that isolated the page, the page cache radix tree and
273 * optional buffer heads at page->private.
275 return page_count(page) - page_has_private(page) == 2;
278 static int may_write_to_queue(struct backing_dev_info *bdi)
280 if (current->flags & PF_SWAPWRITE)
282 if (!bdi_write_congested(bdi))
284 if (bdi == current->backing_dev_info)
290 * We detected a synchronous write error writing a page out. Probably
291 * -ENOSPC. We need to propagate that into the address_space for a subsequent
292 * fsync(), msync() or close().
294 * The tricky part is that after writepage we cannot touch the mapping: nothing
295 * prevents it from being freed up. But we have a ref on the page and once
296 * that page is locked, the mapping is pinned.
298 * We're allowed to run sleeping lock_page() here because we know the caller has
301 static void handle_write_error(struct address_space *mapping,
302 struct page *page, int error)
304 lock_page_nosync(page);
305 if (page_mapping(page) == mapping)
306 mapping_set_error(mapping, error);
310 /* Request for sync pageout. */
316 /* possible outcome of pageout() */
318 /* failed to write page out, page is locked */
320 /* move page to the active list, page is locked */
322 /* page has been sent to the disk successfully, page is unlocked */
324 /* page is clean and locked */
329 * pageout is called by shrink_page_list() for each dirty page.
330 * Calls ->writepage().
332 static pageout_t pageout(struct page *page, struct address_space *mapping,
333 enum pageout_io sync_writeback)
336 * If the page is dirty, only perform writeback if that write
337 * will be non-blocking. To prevent this allocation from being
338 * stalled by pagecache activity. But note that there may be
339 * stalls if we need to run get_block(). We could test
340 * PagePrivate for that.
342 * If this process is currently in __generic_file_aio_write() against
343 * this page's queue, we can perform writeback even if that
346 * If the page is swapcache, write it back even if that would
347 * block, for some throttling. This happens by accident, because
348 * swap_backing_dev_info is bust: it doesn't reflect the
349 * congestion state of the swapdevs. Easy to fix, if needed.
351 if (!is_page_cache_freeable(page))
355 * Some data journaling orphaned pages can have
356 * page->mapping == NULL while being dirty with clean buffers.
358 if (page_has_private(page)) {
359 if (try_to_free_buffers(page)) {
360 ClearPageDirty(page);
361 printk("%s: orphaned page\n", __func__);
367 if (mapping->a_ops->writepage == NULL)
368 return PAGE_ACTIVATE;
369 if (!may_write_to_queue(mapping->backing_dev_info))
372 if (clear_page_dirty_for_io(page)) {
374 struct writeback_control wbc = {
375 .sync_mode = WB_SYNC_NONE,
376 .nr_to_write = SWAP_CLUSTER_MAX,
378 .range_end = LLONG_MAX,
382 SetPageReclaim(page);
383 res = mapping->a_ops->writepage(page, &wbc);
385 handle_write_error(mapping, page, res);
386 if (res == AOP_WRITEPAGE_ACTIVATE) {
387 ClearPageReclaim(page);
388 return PAGE_ACTIVATE;
392 * Wait on writeback if requested to. This happens when
393 * direct reclaiming a large contiguous area and the
394 * first attempt to free a range of pages fails.
396 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
397 wait_on_page_writeback(page);
399 if (!PageWriteback(page)) {
400 /* synchronous write or broken a_ops? */
401 ClearPageReclaim(page);
403 trace_mm_vmscan_writepage(page,
404 trace_reclaim_flags(page, sync_writeback));
405 inc_zone_page_state(page, NR_VMSCAN_WRITE);
413 * Same as remove_mapping, but if the page is removed from the mapping, it
414 * gets returned with a refcount of 0.
416 static int __remove_mapping(struct address_space *mapping, struct page *page)
418 BUG_ON(!PageLocked(page));
419 BUG_ON(mapping != page_mapping(page));
421 spin_lock_irq(&mapping->tree_lock);
423 * The non racy check for a busy page.
425 * Must be careful with the order of the tests. When someone has
426 * a ref to the page, it may be possible that they dirty it then
427 * drop the reference. So if PageDirty is tested before page_count
428 * here, then the following race may occur:
430 * get_user_pages(&page);
431 * [user mapping goes away]
433 * !PageDirty(page) [good]
434 * SetPageDirty(page);
436 * !page_count(page) [good, discard it]
438 * [oops, our write_to data is lost]
440 * Reversing the order of the tests ensures such a situation cannot
441 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
442 * load is not satisfied before that of page->_count.
444 * Note that if SetPageDirty is always performed via set_page_dirty,
445 * and thus under tree_lock, then this ordering is not required.
447 if (!page_freeze_refs(page, 2))
449 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
450 if (unlikely(PageDirty(page))) {
451 page_unfreeze_refs(page, 2);
455 if (PageSwapCache(page)) {
456 swp_entry_t swap = { .val = page_private(page) };
457 __delete_from_swap_cache(page);
458 spin_unlock_irq(&mapping->tree_lock);
459 swapcache_free(swap, page);
461 __remove_from_page_cache(page);
462 spin_unlock_irq(&mapping->tree_lock);
463 mem_cgroup_uncharge_cache_page(page);
469 spin_unlock_irq(&mapping->tree_lock);
474 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
475 * someone else has a ref on the page, abort and return 0. If it was
476 * successfully detached, return 1. Assumes the caller has a single ref on
479 int remove_mapping(struct address_space *mapping, struct page *page)
481 if (__remove_mapping(mapping, page)) {
483 * Unfreezing the refcount with 1 rather than 2 effectively
484 * drops the pagecache ref for us without requiring another
487 page_unfreeze_refs(page, 1);
494 * putback_lru_page - put previously isolated page onto appropriate LRU list
495 * @page: page to be put back to appropriate lru list
497 * Add previously isolated @page to appropriate LRU list.
498 * Page may still be unevictable for other reasons.
500 * lru_lock must not be held, interrupts must be enabled.
502 void putback_lru_page(struct page *page)
505 int active = !!TestClearPageActive(page);
506 int was_unevictable = PageUnevictable(page);
508 VM_BUG_ON(PageLRU(page));
511 ClearPageUnevictable(page);
513 if (page_evictable(page, NULL)) {
515 * For evictable pages, we can use the cache.
516 * In event of a race, worst case is we end up with an
517 * unevictable page on [in]active list.
518 * We know how to handle that.
520 lru = active + page_lru_base_type(page);
521 lru_cache_add_lru(page, lru);
524 * Put unevictable pages directly on zone's unevictable
527 lru = LRU_UNEVICTABLE;
528 add_page_to_unevictable_list(page);
530 * When racing with an mlock clearing (page is
531 * unlocked), make sure that if the other thread does
532 * not observe our setting of PG_lru and fails
533 * isolation, we see PG_mlocked cleared below and move
534 * the page back to the evictable list.
536 * The other side is TestClearPageMlocked().
542 * page's status can change while we move it among lru. If an evictable
543 * page is on unevictable list, it never be freed. To avoid that,
544 * check after we added it to the list, again.
546 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
547 if (!isolate_lru_page(page)) {
551 /* This means someone else dropped this page from LRU
552 * So, it will be freed or putback to LRU again. There is
553 * nothing to do here.
557 if (was_unevictable && lru != LRU_UNEVICTABLE)
558 count_vm_event(UNEVICTABLE_PGRESCUED);
559 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
560 count_vm_event(UNEVICTABLE_PGCULLED);
562 put_page(page); /* drop ref from isolate */
565 enum page_references {
567 PAGEREF_RECLAIM_CLEAN,
572 static enum page_references page_check_references(struct page *page,
573 struct scan_control *sc)
575 int referenced_ptes, referenced_page;
576 unsigned long vm_flags;
578 referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags);
579 referenced_page = TestClearPageReferenced(page);
581 /* Lumpy reclaim - ignore references */
582 if (sc->lumpy_reclaim_mode)
583 return PAGEREF_RECLAIM;
586 * Mlock lost the isolation race with us. Let try_to_unmap()
587 * move the page to the unevictable list.
589 if (vm_flags & VM_LOCKED)
590 return PAGEREF_RECLAIM;
592 if (referenced_ptes) {
594 return PAGEREF_ACTIVATE;
596 * All mapped pages start out with page table
597 * references from the instantiating fault, so we need
598 * to look twice if a mapped file page is used more
601 * Mark it and spare it for another trip around the
602 * inactive list. Another page table reference will
603 * lead to its activation.
605 * Note: the mark is set for activated pages as well
606 * so that recently deactivated but used pages are
609 SetPageReferenced(page);
612 return PAGEREF_ACTIVATE;
617 /* Reclaim if clean, defer dirty pages to writeback */
619 return PAGEREF_RECLAIM_CLEAN;
621 return PAGEREF_RECLAIM;
624 static noinline_for_stack void free_page_list(struct list_head *free_pages)
626 struct pagevec freed_pvec;
627 struct page *page, *tmp;
629 pagevec_init(&freed_pvec, 1);
631 list_for_each_entry_safe(page, tmp, free_pages, lru) {
632 list_del(&page->lru);
633 if (!pagevec_add(&freed_pvec, page)) {
634 __pagevec_free(&freed_pvec);
635 pagevec_reinit(&freed_pvec);
639 pagevec_free(&freed_pvec);
643 * shrink_page_list() returns the number of reclaimed pages
645 static unsigned long shrink_page_list(struct list_head *page_list,
646 struct scan_control *sc,
647 enum pageout_io sync_writeback)
649 LIST_HEAD(ret_pages);
650 LIST_HEAD(free_pages);
652 unsigned long nr_reclaimed = 0;
656 while (!list_empty(page_list)) {
657 enum page_references references;
658 struct address_space *mapping;
664 page = lru_to_page(page_list);
665 list_del(&page->lru);
667 if (!trylock_page(page))
670 VM_BUG_ON(PageActive(page));
674 if (unlikely(!page_evictable(page, NULL)))
677 if (!sc->may_unmap && page_mapped(page))
680 /* Double the slab pressure for mapped and swapcache pages */
681 if (page_mapped(page) || PageSwapCache(page))
684 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
685 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
687 if (PageWriteback(page)) {
689 * Synchronous reclaim is performed in two passes,
690 * first an asynchronous pass over the list to
691 * start parallel writeback, and a second synchronous
692 * pass to wait for the IO to complete. Wait here
693 * for any page for which writeback has already
696 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
697 wait_on_page_writeback(page);
702 references = page_check_references(page, sc);
703 switch (references) {
704 case PAGEREF_ACTIVATE:
705 goto activate_locked;
708 case PAGEREF_RECLAIM:
709 case PAGEREF_RECLAIM_CLEAN:
710 ; /* try to reclaim the page below */
714 * Anonymous process memory has backing store?
715 * Try to allocate it some swap space here.
717 if (PageAnon(page) && !PageSwapCache(page)) {
718 if (!(sc->gfp_mask & __GFP_IO))
720 if (!add_to_swap(page))
721 goto activate_locked;
725 mapping = page_mapping(page);
728 * The page is mapped into the page tables of one or more
729 * processes. Try to unmap it here.
731 if (page_mapped(page) && mapping) {
732 switch (try_to_unmap(page, TTU_UNMAP)) {
734 goto activate_locked;
740 ; /* try to free the page below */
744 if (PageDirty(page)) {
745 if (references == PAGEREF_RECLAIM_CLEAN)
749 if (!sc->may_writepage)
752 /* Page is dirty, try to write it out here */
753 switch (pageout(page, mapping, sync_writeback)) {
757 goto activate_locked;
759 if (PageWriteback(page) || PageDirty(page))
762 * A synchronous write - probably a ramdisk. Go
763 * ahead and try to reclaim the page.
765 if (!trylock_page(page))
767 if (PageDirty(page) || PageWriteback(page))
769 mapping = page_mapping(page);
771 ; /* try to free the page below */
776 * If the page has buffers, try to free the buffer mappings
777 * associated with this page. If we succeed we try to free
780 * We do this even if the page is PageDirty().
781 * try_to_release_page() does not perform I/O, but it is
782 * possible for a page to have PageDirty set, but it is actually
783 * clean (all its buffers are clean). This happens if the
784 * buffers were written out directly, with submit_bh(). ext3
785 * will do this, as well as the blockdev mapping.
786 * try_to_release_page() will discover that cleanness and will
787 * drop the buffers and mark the page clean - it can be freed.
789 * Rarely, pages can have buffers and no ->mapping. These are
790 * the pages which were not successfully invalidated in
791 * truncate_complete_page(). We try to drop those buffers here
792 * and if that worked, and the page is no longer mapped into
793 * process address space (page_count == 1) it can be freed.
794 * Otherwise, leave the page on the LRU so it is swappable.
796 if (page_has_private(page)) {
797 if (!try_to_release_page(page, sc->gfp_mask))
798 goto activate_locked;
799 if (!mapping && page_count(page) == 1) {
801 if (put_page_testzero(page))
805 * rare race with speculative reference.
806 * the speculative reference will free
807 * this page shortly, so we may
808 * increment nr_reclaimed here (and
809 * leave it off the LRU).
817 if (!mapping || !__remove_mapping(mapping, page))
821 * At this point, we have no other references and there is
822 * no way to pick any more up (removed from LRU, removed
823 * from pagecache). Can use non-atomic bitops now (and
824 * we obviously don't have to worry about waking up a process
825 * waiting on the page lock, because there are no references.
827 __clear_page_locked(page);
832 * Is there need to periodically free_page_list? It would
833 * appear not as the counts should be low
835 list_add(&page->lru, &free_pages);
839 if (PageSwapCache(page))
840 try_to_free_swap(page);
842 putback_lru_page(page);
846 /* Not a candidate for swapping, so reclaim swap space. */
847 if (PageSwapCache(page) && vm_swap_full())
848 try_to_free_swap(page);
849 VM_BUG_ON(PageActive(page));
855 list_add(&page->lru, &ret_pages);
856 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
859 free_page_list(&free_pages);
861 list_splice(&ret_pages, page_list);
862 count_vm_events(PGACTIVATE, pgactivate);
867 * Attempt to remove the specified page from its LRU. Only take this page
868 * if it is of the appropriate PageActive status. Pages which are being
869 * freed elsewhere are also ignored.
871 * page: page to consider
872 * mode: one of the LRU isolation modes defined above
874 * returns 0 on success, -ve errno on failure.
876 int __isolate_lru_page(struct page *page, int mode, int file)
880 /* Only take pages on the LRU. */
885 * When checking the active state, we need to be sure we are
886 * dealing with comparible boolean values. Take the logical not
889 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
892 if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
896 * When this function is being called for lumpy reclaim, we
897 * initially look into all LRU pages, active, inactive and
898 * unevictable; only give shrink_page_list evictable pages.
900 if (PageUnevictable(page))
905 if (likely(get_page_unless_zero(page))) {
907 * Be careful not to clear PageLRU until after we're
908 * sure the page is not being freed elsewhere -- the
909 * page release code relies on it.
919 * zone->lru_lock is heavily contended. Some of the functions that
920 * shrink the lists perform better by taking out a batch of pages
921 * and working on them outside the LRU lock.
923 * For pagecache intensive workloads, this function is the hottest
924 * spot in the kernel (apart from copy_*_user functions).
926 * Appropriate locks must be held before calling this function.
928 * @nr_to_scan: The number of pages to look through on the list.
929 * @src: The LRU list to pull pages off.
930 * @dst: The temp list to put pages on to.
931 * @scanned: The number of pages that were scanned.
932 * @order: The caller's attempted allocation order
933 * @mode: One of the LRU isolation modes
934 * @file: True [1] if isolating file [!anon] pages
936 * returns how many pages were moved onto *@dst.
938 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
939 struct list_head *src, struct list_head *dst,
940 unsigned long *scanned, int order, int mode, int file)
942 unsigned long nr_taken = 0;
943 unsigned long nr_lumpy_taken = 0;
944 unsigned long nr_lumpy_dirty = 0;
945 unsigned long nr_lumpy_failed = 0;
948 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
951 unsigned long end_pfn;
952 unsigned long page_pfn;
955 page = lru_to_page(src);
956 prefetchw_prev_lru_page(page, src, flags);
958 VM_BUG_ON(!PageLRU(page));
960 switch (__isolate_lru_page(page, mode, file)) {
962 list_move(&page->lru, dst);
963 mem_cgroup_del_lru(page);
968 /* else it is being freed elsewhere */
969 list_move(&page->lru, src);
970 mem_cgroup_rotate_lru_list(page, page_lru(page));
981 * Attempt to take all pages in the order aligned region
982 * surrounding the tag page. Only take those pages of
983 * the same active state as that tag page. We may safely
984 * round the target page pfn down to the requested order
985 * as the mem_map is guarenteed valid out to MAX_ORDER,
986 * where that page is in a different zone we will detect
987 * it from its zone id and abort this block scan.
989 zone_id = page_zone_id(page);
990 page_pfn = page_to_pfn(page);
991 pfn = page_pfn & ~((1 << order) - 1);
992 end_pfn = pfn + (1 << order);
993 for (; pfn < end_pfn; pfn++) {
994 struct page *cursor_page;
996 /* The target page is in the block, ignore it. */
997 if (unlikely(pfn == page_pfn))
1000 /* Avoid holes within the zone. */
1001 if (unlikely(!pfn_valid_within(pfn)))
1004 cursor_page = pfn_to_page(pfn);
1006 /* Check that we have not crossed a zone boundary. */
1007 if (unlikely(page_zone_id(cursor_page) != zone_id))
1011 * If we don't have enough swap space, reclaiming of
1012 * anon page which don't already have a swap slot is
1015 if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
1016 !PageSwapCache(cursor_page))
1019 if (__isolate_lru_page(cursor_page, mode, file) == 0) {
1020 list_move(&cursor_page->lru, dst);
1021 mem_cgroup_del_lru(cursor_page);
1024 if (PageDirty(cursor_page))
1028 if (mode == ISOLATE_BOTH &&
1029 page_count(cursor_page))
1037 trace_mm_vmscan_lru_isolate(order,
1040 nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
1045 static unsigned long isolate_pages_global(unsigned long nr,
1046 struct list_head *dst,
1047 unsigned long *scanned, int order,
1048 int mode, struct zone *z,
1049 int active, int file)
1056 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
1061 * clear_active_flags() is a helper for shrink_active_list(), clearing
1062 * any active bits from the pages in the list.
1064 static unsigned long clear_active_flags(struct list_head *page_list,
1065 unsigned int *count)
1071 list_for_each_entry(page, page_list, lru) {
1072 lru = page_lru_base_type(page);
1073 if (PageActive(page)) {
1075 ClearPageActive(page);
1086 * isolate_lru_page - tries to isolate a page from its LRU list
1087 * @page: page to isolate from its LRU list
1089 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1090 * vmstat statistic corresponding to whatever LRU list the page was on.
1092 * Returns 0 if the page was removed from an LRU list.
1093 * Returns -EBUSY if the page was not on an LRU list.
1095 * The returned page will have PageLRU() cleared. If it was found on
1096 * the active list, it will have PageActive set. If it was found on
1097 * the unevictable list, it will have the PageUnevictable bit set. That flag
1098 * may need to be cleared by the caller before letting the page go.
1100 * The vmstat statistic corresponding to the list on which the page was
1101 * found will be decremented.
1104 * (1) Must be called with an elevated refcount on the page. This is a
1105 * fundamentnal difference from isolate_lru_pages (which is called
1106 * without a stable reference).
1107 * (2) the lru_lock must not be held.
1108 * (3) interrupts must be enabled.
1110 int isolate_lru_page(struct page *page)
1114 if (PageLRU(page)) {
1115 struct zone *zone = page_zone(page);
1117 spin_lock_irq(&zone->lru_lock);
1118 if (PageLRU(page) && get_page_unless_zero(page)) {
1119 int lru = page_lru(page);
1123 del_page_from_lru_list(zone, page, lru);
1125 spin_unlock_irq(&zone->lru_lock);
1131 * Are there way too many processes in the direct reclaim path already?
1133 static int too_many_isolated(struct zone *zone, int file,
1134 struct scan_control *sc)
1136 unsigned long inactive, isolated;
1138 if (current_is_kswapd())
1141 if (!scanning_global_lru(sc))
1145 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1146 isolated = zone_page_state(zone, NR_ISOLATED_FILE);
1148 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1149 isolated = zone_page_state(zone, NR_ISOLATED_ANON);
1152 return isolated > inactive;
1156 * TODO: Try merging with migrations version of putback_lru_pages
1158 static noinline_for_stack void
1159 putback_lru_pages(struct zone *zone, struct scan_control *sc,
1160 unsigned long nr_anon, unsigned long nr_file,
1161 struct list_head *page_list)
1164 struct pagevec pvec;
1165 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1167 pagevec_init(&pvec, 1);
1170 * Put back any unfreeable pages.
1172 spin_lock(&zone->lru_lock);
1173 while (!list_empty(page_list)) {
1175 page = lru_to_page(page_list);
1176 VM_BUG_ON(PageLRU(page));
1177 list_del(&page->lru);
1178 if (unlikely(!page_evictable(page, NULL))) {
1179 spin_unlock_irq(&zone->lru_lock);
1180 putback_lru_page(page);
1181 spin_lock_irq(&zone->lru_lock);
1185 lru = page_lru(page);
1186 add_page_to_lru_list(zone, page, lru);
1187 if (is_active_lru(lru)) {
1188 int file = is_file_lru(lru);
1189 reclaim_stat->recent_rotated[file]++;
1191 if (!pagevec_add(&pvec, page)) {
1192 spin_unlock_irq(&zone->lru_lock);
1193 __pagevec_release(&pvec);
1194 spin_lock_irq(&zone->lru_lock);
1197 __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
1198 __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
1200 spin_unlock_irq(&zone->lru_lock);
1201 pagevec_release(&pvec);
1204 static noinline_for_stack void update_isolated_counts(struct zone *zone,
1205 struct scan_control *sc,
1206 unsigned long *nr_anon,
1207 unsigned long *nr_file,
1208 struct list_head *isolated_list)
1210 unsigned long nr_active;
1211 unsigned int count[NR_LRU_LISTS] = { 0, };
1212 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1214 nr_active = clear_active_flags(isolated_list, count);
1215 __count_vm_events(PGDEACTIVATE, nr_active);
1217 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1218 -count[LRU_ACTIVE_FILE]);
1219 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1220 -count[LRU_INACTIVE_FILE]);
1221 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1222 -count[LRU_ACTIVE_ANON]);
1223 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1224 -count[LRU_INACTIVE_ANON]);
1226 *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
1227 *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
1228 __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
1229 __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
1231 reclaim_stat->recent_scanned[0] += *nr_anon;
1232 reclaim_stat->recent_scanned[1] += *nr_file;
1236 * Returns true if the caller should wait to clean dirty/writeback pages.
1238 * If we are direct reclaiming for contiguous pages and we do not reclaim
1239 * everything in the list, try again and wait for writeback IO to complete.
1240 * This will stall high-order allocations noticeably. Only do that when really
1241 * need to free the pages under high memory pressure.
1243 static inline bool should_reclaim_stall(unsigned long nr_taken,
1244 unsigned long nr_freed,
1246 struct scan_control *sc)
1248 int lumpy_stall_priority;
1250 /* kswapd should not stall on sync IO */
1251 if (current_is_kswapd())
1254 /* Only stall on lumpy reclaim */
1255 if (!sc->lumpy_reclaim_mode)
1258 /* If we have relaimed everything on the isolated list, no stall */
1259 if (nr_freed == nr_taken)
1263 * For high-order allocations, there are two stall thresholds.
1264 * High-cost allocations stall immediately where as lower
1265 * order allocations such as stacks require the scanning
1266 * priority to be much higher before stalling.
1268 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1269 lumpy_stall_priority = DEF_PRIORITY;
1271 lumpy_stall_priority = DEF_PRIORITY / 3;
1273 return priority <= lumpy_stall_priority;
1277 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1278 * of reclaimed pages
1280 static noinline_for_stack unsigned long
1281 shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
1282 struct scan_control *sc, int priority, int file)
1284 LIST_HEAD(page_list);
1285 unsigned long nr_scanned;
1286 unsigned long nr_reclaimed = 0;
1287 unsigned long nr_taken;
1288 unsigned long nr_active;
1289 unsigned long nr_anon;
1290 unsigned long nr_file;
1292 while (unlikely(too_many_isolated(zone, file, sc))) {
1293 congestion_wait(BLK_RW_ASYNC, HZ/10);
1295 /* We are about to die and free our memory. Return now. */
1296 if (fatal_signal_pending(current))
1297 return SWAP_CLUSTER_MAX;
1302 spin_lock_irq(&zone->lru_lock);
1304 if (scanning_global_lru(sc)) {
1305 nr_taken = isolate_pages_global(nr_to_scan,
1306 &page_list, &nr_scanned, sc->order,
1307 sc->lumpy_reclaim_mode ?
1308 ISOLATE_BOTH : ISOLATE_INACTIVE,
1310 zone->pages_scanned += nr_scanned;
1311 if (current_is_kswapd())
1312 __count_zone_vm_events(PGSCAN_KSWAPD, zone,
1315 __count_zone_vm_events(PGSCAN_DIRECT, zone,
1318 nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
1319 &page_list, &nr_scanned, sc->order,
1320 sc->lumpy_reclaim_mode ?
1321 ISOLATE_BOTH : ISOLATE_INACTIVE,
1322 zone, sc->mem_cgroup,
1325 * mem_cgroup_isolate_pages() keeps track of
1326 * scanned pages on its own.
1330 if (nr_taken == 0) {
1331 spin_unlock_irq(&zone->lru_lock);
1335 update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list);
1337 spin_unlock_irq(&zone->lru_lock);
1339 nr_reclaimed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1341 /* Check if we should syncronously wait for writeback */
1342 if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
1344 * The attempt at page out may have made some
1345 * of the pages active, mark them inactive again.
1347 nr_active = clear_active_flags(&page_list, NULL);
1348 count_vm_events(PGDEACTIVATE, nr_active);
1350 nr_reclaimed += shrink_page_list(&page_list, sc, PAGEOUT_IO_SYNC);
1353 local_irq_disable();
1354 if (current_is_kswapd())
1355 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
1356 __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
1358 putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list);
1360 trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
1362 nr_scanned, nr_reclaimed,
1364 trace_shrink_flags(file, sc->lumpy_reclaim_mode));
1365 return nr_reclaimed;
1369 * This moves pages from the active list to the inactive list.
1371 * We move them the other way if the page is referenced by one or more
1372 * processes, from rmap.
1374 * If the pages are mostly unmapped, the processing is fast and it is
1375 * appropriate to hold zone->lru_lock across the whole operation. But if
1376 * the pages are mapped, the processing is slow (page_referenced()) so we
1377 * should drop zone->lru_lock around each page. It's impossible to balance
1378 * this, so instead we remove the pages from the LRU while processing them.
1379 * It is safe to rely on PG_active against the non-LRU pages in here because
1380 * nobody will play with that bit on a non-LRU page.
1382 * The downside is that we have to touch page->_count against each page.
1383 * But we had to alter page->flags anyway.
1386 static void move_active_pages_to_lru(struct zone *zone,
1387 struct list_head *list,
1390 unsigned long pgmoved = 0;
1391 struct pagevec pvec;
1394 pagevec_init(&pvec, 1);
1396 while (!list_empty(list)) {
1397 page = lru_to_page(list);
1399 VM_BUG_ON(PageLRU(page));
1402 list_move(&page->lru, &zone->lru[lru].list);
1403 mem_cgroup_add_lru_list(page, lru);
1406 if (!pagevec_add(&pvec, page) || list_empty(list)) {
1407 spin_unlock_irq(&zone->lru_lock);
1408 if (buffer_heads_over_limit)
1409 pagevec_strip(&pvec);
1410 __pagevec_release(&pvec);
1411 spin_lock_irq(&zone->lru_lock);
1414 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1415 if (!is_active_lru(lru))
1416 __count_vm_events(PGDEACTIVATE, pgmoved);
1419 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1420 struct scan_control *sc, int priority, int file)
1422 unsigned long nr_taken;
1423 unsigned long pgscanned;
1424 unsigned long vm_flags;
1425 LIST_HEAD(l_hold); /* The pages which were snipped off */
1426 LIST_HEAD(l_active);
1427 LIST_HEAD(l_inactive);
1429 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1430 unsigned long nr_rotated = 0;
1433 spin_lock_irq(&zone->lru_lock);
1434 if (scanning_global_lru(sc)) {
1435 nr_taken = isolate_pages_global(nr_pages, &l_hold,
1436 &pgscanned, sc->order,
1437 ISOLATE_ACTIVE, zone,
1439 zone->pages_scanned += pgscanned;
1441 nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold,
1442 &pgscanned, sc->order,
1443 ISOLATE_ACTIVE, zone,
1444 sc->mem_cgroup, 1, file);
1446 * mem_cgroup_isolate_pages() keeps track of
1447 * scanned pages on its own.
1451 reclaim_stat->recent_scanned[file] += nr_taken;
1453 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1455 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
1457 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
1458 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
1459 spin_unlock_irq(&zone->lru_lock);
1461 while (!list_empty(&l_hold)) {
1463 page = lru_to_page(&l_hold);
1464 list_del(&page->lru);
1466 if (unlikely(!page_evictable(page, NULL))) {
1467 putback_lru_page(page);
1471 if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
1474 * Identify referenced, file-backed active pages and
1475 * give them one more trip around the active list. So
1476 * that executable code get better chances to stay in
1477 * memory under moderate memory pressure. Anon pages
1478 * are not likely to be evicted by use-once streaming
1479 * IO, plus JVM can create lots of anon VM_EXEC pages,
1480 * so we ignore them here.
1482 if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
1483 list_add(&page->lru, &l_active);
1488 ClearPageActive(page); /* we are de-activating */
1489 list_add(&page->lru, &l_inactive);
1493 * Move pages back to the lru list.
1495 spin_lock_irq(&zone->lru_lock);
1497 * Count referenced pages from currently used mappings as rotated,
1498 * even though only some of them are actually re-activated. This
1499 * helps balance scan pressure between file and anonymous pages in
1502 reclaim_stat->recent_rotated[file] += nr_rotated;
1504 move_active_pages_to_lru(zone, &l_active,
1505 LRU_ACTIVE + file * LRU_FILE);
1506 move_active_pages_to_lru(zone, &l_inactive,
1507 LRU_BASE + file * LRU_FILE);
1508 __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
1509 spin_unlock_irq(&zone->lru_lock);
1513 static int inactive_anon_is_low_global(struct zone *zone)
1515 unsigned long active, inactive;
1517 active = zone_page_state(zone, NR_ACTIVE_ANON);
1518 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1520 if (inactive * zone->inactive_ratio < active)
1527 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1528 * @zone: zone to check
1529 * @sc: scan control of this context
1531 * Returns true if the zone does not have enough inactive anon pages,
1532 * meaning some active anon pages need to be deactivated.
1534 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1539 * If we don't have swap space, anonymous page deactivation
1542 if (!total_swap_pages)
1545 if (scanning_global_lru(sc))
1546 low = inactive_anon_is_low_global(zone);
1548 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1552 static inline int inactive_anon_is_low(struct zone *zone,
1553 struct scan_control *sc)
1559 static int inactive_file_is_low_global(struct zone *zone)
1561 unsigned long active, inactive;
1563 active = zone_page_state(zone, NR_ACTIVE_FILE);
1564 inactive = zone_page_state(zone, NR_INACTIVE_FILE);
1566 return (active > inactive);
1570 * inactive_file_is_low - check if file pages need to be deactivated
1571 * @zone: zone to check
1572 * @sc: scan control of this context
1574 * When the system is doing streaming IO, memory pressure here
1575 * ensures that active file pages get deactivated, until more
1576 * than half of the file pages are on the inactive list.
1578 * Once we get to that situation, protect the system's working
1579 * set from being evicted by disabling active file page aging.
1581 * This uses a different ratio than the anonymous pages, because
1582 * the page cache uses a use-once replacement algorithm.
1584 static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
1588 if (scanning_global_lru(sc))
1589 low = inactive_file_is_low_global(zone);
1591 low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
1595 static int inactive_list_is_low(struct zone *zone, struct scan_control *sc,
1599 return inactive_file_is_low(zone, sc);
1601 return inactive_anon_is_low(zone, sc);
1604 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1605 struct zone *zone, struct scan_control *sc, int priority)
1607 int file = is_file_lru(lru);
1609 if (is_active_lru(lru)) {
1610 if (inactive_list_is_low(zone, sc, file))
1611 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1615 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1619 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1620 * until we collected @swap_cluster_max pages to scan.
1622 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,
1623 unsigned long *nr_saved_scan)
1627 *nr_saved_scan += nr_to_scan;
1628 nr = *nr_saved_scan;
1630 if (nr >= SWAP_CLUSTER_MAX)
1639 * Determine how aggressively the anon and file LRU lists should be
1640 * scanned. The relative value of each set of LRU lists is determined
1641 * by looking at the fraction of the pages scanned we did rotate back
1642 * onto the active list instead of evict.
1644 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1646 static void get_scan_count(struct zone *zone, struct scan_control *sc,
1647 unsigned long *nr, int priority)
1649 unsigned long anon, file, free;
1650 unsigned long anon_prio, file_prio;
1651 unsigned long ap, fp;
1652 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1653 u64 fraction[2], denominator;
1657 /* If we have no swap space, do not bother scanning anon pages. */
1658 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1666 anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) +
1667 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON);
1668 file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) +
1669 zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE);
1671 if (scanning_global_lru(sc)) {
1672 free = zone_page_state(zone, NR_FREE_PAGES);
1673 /* If we have very few page cache pages,
1674 force-scan anon pages. */
1675 if (unlikely(file + free <= high_wmark_pages(zone))) {
1684 * With swappiness at 100, anonymous and file have the same priority.
1685 * This scanning priority is essentially the inverse of IO cost.
1687 anon_prio = sc->swappiness;
1688 file_prio = 200 - sc->swappiness;
1691 * OK, so we have swap space and a fair amount of page cache
1692 * pages. We use the recently rotated / recently scanned
1693 * ratios to determine how valuable each cache is.
1695 * Because workloads change over time (and to avoid overflow)
1696 * we keep these statistics as a floating average, which ends
1697 * up weighing recent references more than old ones.
1699 * anon in [0], file in [1]
1701 spin_lock_irq(&zone->lru_lock);
1702 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1703 reclaim_stat->recent_scanned[0] /= 2;
1704 reclaim_stat->recent_rotated[0] /= 2;
1707 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1708 reclaim_stat->recent_scanned[1] /= 2;
1709 reclaim_stat->recent_rotated[1] /= 2;
1713 * The amount of pressure on anon vs file pages is inversely
1714 * proportional to the fraction of recently scanned pages on
1715 * each list that were recently referenced and in active use.
1717 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1718 ap /= reclaim_stat->recent_rotated[0] + 1;
1720 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1721 fp /= reclaim_stat->recent_rotated[1] + 1;
1722 spin_unlock_irq(&zone->lru_lock);
1726 denominator = ap + fp + 1;
1728 for_each_evictable_lru(l) {
1729 int file = is_file_lru(l);
1732 scan = zone_nr_lru_pages(zone, sc, l);
1733 if (priority || noswap) {
1735 scan = div64_u64(scan * fraction[file], denominator);
1737 nr[l] = nr_scan_try_batch(scan,
1738 &reclaim_stat->nr_saved_scan[l]);
1742 static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc)
1745 * If we need a large contiguous chunk of memory, or have
1746 * trouble getting a small set of contiguous pages, we
1747 * will reclaim both active and inactive pages.
1749 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1750 sc->lumpy_reclaim_mode = 1;
1751 else if (sc->order && priority < DEF_PRIORITY - 2)
1752 sc->lumpy_reclaim_mode = 1;
1754 sc->lumpy_reclaim_mode = 0;
1758 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1760 static void shrink_zone(int priority, struct zone *zone,
1761 struct scan_control *sc)
1763 unsigned long nr[NR_LRU_LISTS];
1764 unsigned long nr_to_scan;
1766 unsigned long nr_reclaimed = sc->nr_reclaimed;
1767 unsigned long nr_to_reclaim = sc->nr_to_reclaim;
1769 get_scan_count(zone, sc, nr, priority);
1771 set_lumpy_reclaim_mode(priority, sc);
1773 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1774 nr[LRU_INACTIVE_FILE]) {
1775 for_each_evictable_lru(l) {
1777 nr_to_scan = min_t(unsigned long,
1778 nr[l], SWAP_CLUSTER_MAX);
1779 nr[l] -= nr_to_scan;
1781 nr_reclaimed += shrink_list(l, nr_to_scan,
1782 zone, sc, priority);
1786 * On large memory systems, scan >> priority can become
1787 * really large. This is fine for the starting priority;
1788 * we want to put equal scanning pressure on each zone.
1789 * However, if the VM has a harder time of freeing pages,
1790 * with multiple processes reclaiming pages, the total
1791 * freeing target can get unreasonably large.
1793 if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
1797 sc->nr_reclaimed = nr_reclaimed;
1800 * Even if we did not try to evict anon pages at all, we want to
1801 * rebalance the anon lru active/inactive ratio.
1803 if (inactive_anon_is_low(zone, sc))
1804 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1806 throttle_vm_writeout(sc->gfp_mask);
1810 * This is the direct reclaim path, for page-allocating processes. We only
1811 * try to reclaim pages from zones which will satisfy the caller's allocation
1814 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1816 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1818 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1819 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1820 * zone defense algorithm.
1822 * If a zone is deemed to be full of pinned pages then just give it a light
1823 * scan then give up on it.
1825 static void shrink_zones(int priority, struct zonelist *zonelist,
1826 struct scan_control *sc)
1831 for_each_zone_zonelist_nodemask(zone, z, zonelist,
1832 gfp_zone(sc->gfp_mask), sc->nodemask) {
1833 if (!populated_zone(zone))
1836 * Take care memory controller reclaiming has small influence
1839 if (scanning_global_lru(sc)) {
1840 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1842 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
1843 continue; /* Let kswapd poll it */
1846 shrink_zone(priority, zone, sc);
1850 static bool zone_reclaimable(struct zone *zone)
1852 return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
1856 * As hibernation is going on, kswapd is freezed so that it can't mark
1857 * the zone into all_unreclaimable. It can't handle OOM during hibernation.
1858 * So let's check zone's unreclaimable in direct reclaim as well as kswapd.
1860 static bool all_unreclaimable(struct zonelist *zonelist,
1861 struct scan_control *sc)
1865 bool all_unreclaimable = true;
1867 for_each_zone_zonelist_nodemask(zone, z, zonelist,
1868 gfp_zone(sc->gfp_mask), sc->nodemask) {
1869 if (!populated_zone(zone))
1871 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1873 if (zone_reclaimable(zone)) {
1874 all_unreclaimable = false;
1879 return all_unreclaimable;
1883 * This is the main entry point to direct page reclaim.
1885 * If a full scan of the inactive list fails to free enough memory then we
1886 * are "out of memory" and something needs to be killed.
1888 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1889 * high - the zone may be full of dirty or under-writeback pages, which this
1890 * caller can't do much about. We kick the writeback threads and take explicit
1891 * naps in the hope that some of these pages can be written. But if the
1892 * allocating task holds filesystem locks which prevent writeout this might not
1893 * work, and the allocation attempt will fail.
1895 * returns: 0, if no pages reclaimed
1896 * else, the number of pages reclaimed
1898 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1899 struct scan_control *sc)
1902 unsigned long total_scanned = 0;
1903 struct reclaim_state *reclaim_state = current->reclaim_state;
1906 unsigned long writeback_threshold;
1909 delayacct_freepages_start();
1911 if (scanning_global_lru(sc))
1912 count_vm_event(ALLOCSTALL);
1914 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1917 disable_swap_token();
1918 shrink_zones(priority, zonelist, sc);
1920 * Don't shrink slabs when reclaiming memory from
1921 * over limit cgroups
1923 if (scanning_global_lru(sc)) {
1924 unsigned long lru_pages = 0;
1925 for_each_zone_zonelist(zone, z, zonelist,
1926 gfp_zone(sc->gfp_mask)) {
1927 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1930 lru_pages += zone_reclaimable_pages(zone);
1933 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1934 if (reclaim_state) {
1935 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1936 reclaim_state->reclaimed_slab = 0;
1939 total_scanned += sc->nr_scanned;
1940 if (sc->nr_reclaimed >= sc->nr_to_reclaim)
1944 * Try to write back as many pages as we just scanned. This
1945 * tends to cause slow streaming writers to write data to the
1946 * disk smoothly, at the dirtying rate, which is nice. But
1947 * that's undesirable in laptop mode, where we *want* lumpy
1948 * writeout. So in laptop mode, write out the whole world.
1950 writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
1951 if (total_scanned > writeback_threshold) {
1952 wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
1953 sc->may_writepage = 1;
1956 /* Take a nap, wait for some writeback to complete */
1957 if (!sc->hibernation_mode && sc->nr_scanned &&
1958 priority < DEF_PRIORITY - 2)
1959 congestion_wait(BLK_RW_ASYNC, HZ/10);
1963 delayacct_freepages_end();
1966 if (sc->nr_reclaimed)
1967 return sc->nr_reclaimed;
1969 /* top priority shrink_zones still had more to do? don't OOM, then */
1970 if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
1976 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1977 gfp_t gfp_mask, nodemask_t *nodemask)
1979 unsigned long nr_reclaimed;
1980 struct scan_control sc = {
1981 .gfp_mask = gfp_mask,
1982 .may_writepage = !laptop_mode,
1983 .nr_to_reclaim = SWAP_CLUSTER_MAX,
1986 .swappiness = vm_swappiness,
1989 .nodemask = nodemask,
1992 trace_mm_vmscan_direct_reclaim_begin(order,
1996 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
1998 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
2000 return nr_reclaimed;
2003 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
2005 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
2006 gfp_t gfp_mask, bool noswap,
2007 unsigned int swappiness,
2010 struct scan_control sc = {
2011 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2012 .may_writepage = !laptop_mode,
2014 .may_swap = !noswap,
2015 .swappiness = swappiness,
2019 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2020 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2022 trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
2027 * NOTE: Although we can get the priority field, using it
2028 * here is not a good idea, since it limits the pages we can scan.
2029 * if we don't reclaim here, the shrink_zone from balance_pgdat
2030 * will pick up pages from other mem cgroup's as well. We hack
2031 * the priority and make it zero.
2033 shrink_zone(0, zone, &sc);
2035 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
2037 return sc.nr_reclaimed;
2040 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
2043 unsigned int swappiness)
2045 struct zonelist *zonelist;
2046 unsigned long nr_reclaimed;
2047 struct scan_control sc = {
2048 .may_writepage = !laptop_mode,
2050 .may_swap = !noswap,
2051 .nr_to_reclaim = SWAP_CLUSTER_MAX,
2052 .swappiness = swappiness,
2054 .mem_cgroup = mem_cont,
2055 .nodemask = NULL, /* we don't care the placement */
2058 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
2059 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
2060 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
2062 trace_mm_vmscan_memcg_reclaim_begin(0,
2066 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2068 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
2070 return nr_reclaimed;
2074 /* is kswapd sleeping prematurely? */
2075 static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
2079 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2083 /* If after HZ/10, a zone is below the high mark, it's premature */
2084 for (i = 0; i < pgdat->nr_zones; i++) {
2085 struct zone *zone = pgdat->node_zones + i;
2087 if (!populated_zone(zone))
2090 if (zone->all_unreclaimable)
2093 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
2102 * For kswapd, balance_pgdat() will work across all this node's zones until
2103 * they are all at high_wmark_pages(zone).
2105 * Returns the number of pages which were actually freed.
2107 * There is special handling here for zones which are full of pinned pages.
2108 * This can happen if the pages are all mlocked, or if they are all used by
2109 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2110 * What we do is to detect the case where all pages in the zone have been
2111 * scanned twice and there has been zero successful reclaim. Mark the zone as
2112 * dead and from now on, only perform a short scan. Basically we're polling
2113 * the zone for when the problem goes away.
2115 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2116 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2117 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2118 * lower zones regardless of the number of free pages in the lower zones. This
2119 * interoperates with the page allocator fallback scheme to ensure that aging
2120 * of pages is balanced across the zones.
2122 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
2127 unsigned long total_scanned;
2128 struct reclaim_state *reclaim_state = current->reclaim_state;
2129 struct scan_control sc = {
2130 .gfp_mask = GFP_KERNEL,
2134 * kswapd doesn't want to be bailed out while reclaim. because
2135 * we want to put equal scanning pressure on each zone.
2137 .nr_to_reclaim = ULONG_MAX,
2138 .swappiness = vm_swappiness,
2144 sc.nr_reclaimed = 0;
2145 sc.may_writepage = !laptop_mode;
2146 count_vm_event(PAGEOUTRUN);
2148 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
2149 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
2150 unsigned long lru_pages = 0;
2151 int has_under_min_watermark_zone = 0;
2153 /* The swap token gets in the way of swapout... */
2155 disable_swap_token();
2160 * Scan in the highmem->dma direction for the highest
2161 * zone which needs scanning
2163 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
2164 struct zone *zone = pgdat->node_zones + i;
2166 if (!populated_zone(zone))
2169 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2173 * Do some background aging of the anon list, to give
2174 * pages a chance to be referenced before reclaiming.
2176 if (inactive_anon_is_low(zone, &sc))
2177 shrink_active_list(SWAP_CLUSTER_MAX, zone,
2180 if (!zone_watermark_ok(zone, order,
2181 high_wmark_pages(zone), 0, 0)) {
2189 for (i = 0; i <= end_zone; i++) {
2190 struct zone *zone = pgdat->node_zones + i;
2192 lru_pages += zone_reclaimable_pages(zone);
2196 * Now scan the zone in the dma->highmem direction, stopping
2197 * at the last zone which needs scanning.
2199 * We do this because the page allocator works in the opposite
2200 * direction. This prevents the page allocator from allocating
2201 * pages behind kswapd's direction of progress, which would
2202 * cause too much scanning of the lower zones.
2204 for (i = 0; i <= end_zone; i++) {
2205 struct zone *zone = pgdat->node_zones + i;
2208 if (!populated_zone(zone))
2211 if (zone->all_unreclaimable && priority != DEF_PRIORITY)
2217 * Call soft limit reclaim before calling shrink_zone.
2218 * For now we ignore the return value
2220 mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);
2223 * We put equal pressure on every zone, unless one
2224 * zone has way too many pages free already.
2226 if (!zone_watermark_ok(zone, order,
2227 8*high_wmark_pages(zone), end_zone, 0))
2228 shrink_zone(priority, zone, &sc);
2229 reclaim_state->reclaimed_slab = 0;
2230 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
2232 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
2233 total_scanned += sc.nr_scanned;
2234 if (zone->all_unreclaimable)
2236 if (nr_slab == 0 && !zone_reclaimable(zone))
2237 zone->all_unreclaimable = 1;
2239 * If we've done a decent amount of scanning and
2240 * the reclaim ratio is low, start doing writepage
2241 * even in laptop mode
2243 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
2244 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
2245 sc.may_writepage = 1;
2247 if (!zone_watermark_ok(zone, order,
2248 high_wmark_pages(zone), end_zone, 0)) {
2251 * We are still under min water mark. This
2252 * means that we have a GFP_ATOMIC allocation
2253 * failure risk. Hurry up!
2255 if (!zone_watermark_ok(zone, order,
2256 min_wmark_pages(zone), end_zone, 0))
2257 has_under_min_watermark_zone = 1;
2262 break; /* kswapd: all done */
2264 * OK, kswapd is getting into trouble. Take a nap, then take
2265 * another pass across the zones.
2267 if (total_scanned && (priority < DEF_PRIORITY - 2)) {
2268 if (has_under_min_watermark_zone)
2269 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
2271 congestion_wait(BLK_RW_ASYNC, HZ/10);
2275 * We do this so kswapd doesn't build up large priorities for
2276 * example when it is freeing in parallel with allocators. It
2277 * matches the direct reclaim path behaviour in terms of impact
2278 * on zone->*_priority.
2280 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
2284 if (!all_zones_ok) {
2290 * Fragmentation may mean that the system cannot be
2291 * rebalanced for high-order allocations in all zones.
2292 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2293 * it means the zones have been fully scanned and are still
2294 * not balanced. For high-order allocations, there is
2295 * little point trying all over again as kswapd may
2298 * Instead, recheck all watermarks at order-0 as they
2299 * are the most important. If watermarks are ok, kswapd will go
2300 * back to sleep. High-order users can still perform direct
2301 * reclaim if they wish.
2303 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
2304 order = sc.order = 0;
2309 return sc.nr_reclaimed;
2313 * The background pageout daemon, started as a kernel thread
2314 * from the init process.
2316 * This basically trickles out pages so that we have _some_
2317 * free memory available even if there is no other activity
2318 * that frees anything up. This is needed for things like routing
2319 * etc, where we otherwise might have all activity going on in
2320 * asynchronous contexts that cannot page things out.
2322 * If there are applications that are active memory-allocators
2323 * (most normal use), this basically shouldn't matter.
2325 static int kswapd(void *p)
2327 unsigned long order;
2328 pg_data_t *pgdat = (pg_data_t*)p;
2329 struct task_struct *tsk = current;
2331 struct reclaim_state reclaim_state = {
2332 .reclaimed_slab = 0,
2334 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
2336 lockdep_set_current_reclaim_state(GFP_KERNEL);
2338 if (!cpumask_empty(cpumask))
2339 set_cpus_allowed_ptr(tsk, cpumask);
2340 current->reclaim_state = &reclaim_state;
2343 * Tell the memory management that we're a "memory allocator",
2344 * and that if we need more memory we should get access to it
2345 * regardless (see "__alloc_pages()"). "kswapd" should
2346 * never get caught in the normal page freeing logic.
2348 * (Kswapd normally doesn't need memory anyway, but sometimes
2349 * you need a small amount of memory in order to be able to
2350 * page out something else, and this flag essentially protects
2351 * us from recursively trying to free more memory as we're
2352 * trying to free the first piece of memory in the first place).
2354 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2359 unsigned long new_order;
2362 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2363 new_order = pgdat->kswapd_max_order;
2364 pgdat->kswapd_max_order = 0;
2365 if (order < new_order) {
2367 * Don't sleep if someone wants a larger 'order'
2372 if (!freezing(current) && !kthread_should_stop()) {
2375 /* Try to sleep for a short interval */
2376 if (!sleeping_prematurely(pgdat, order, remaining)) {
2377 remaining = schedule_timeout(HZ/10);
2378 finish_wait(&pgdat->kswapd_wait, &wait);
2379 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2383 * After a short sleep, check if it was a
2384 * premature sleep. If not, then go fully
2385 * to sleep until explicitly woken up
2387 if (!sleeping_prematurely(pgdat, order, remaining)) {
2388 trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
2392 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
2394 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
2398 order = pgdat->kswapd_max_order;
2400 finish_wait(&pgdat->kswapd_wait, &wait);
2402 ret = try_to_freeze();
2403 if (kthread_should_stop())
2407 * We can speed up thawing tasks if we don't call balance_pgdat
2408 * after returning from the refrigerator
2411 trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
2412 balance_pgdat(pgdat, order);
2419 * A zone is low on free memory, so wake its kswapd task to service it.
2421 void wakeup_kswapd(struct zone *zone, int order)
2425 if (!populated_zone(zone))
2428 pgdat = zone->zone_pgdat;
2429 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
2431 if (pgdat->kswapd_max_order < order)
2432 pgdat->kswapd_max_order = order;
2433 trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
2434 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2436 if (!waitqueue_active(&pgdat->kswapd_wait))
2438 wake_up_interruptible(&pgdat->kswapd_wait);
2442 * The reclaimable count would be mostly accurate.
2443 * The less reclaimable pages may be
2444 * - mlocked pages, which will be moved to unevictable list when encountered
2445 * - mapped pages, which may require several travels to be reclaimed
2446 * - dirty pages, which is not "instantly" reclaimable
2448 unsigned long global_reclaimable_pages(void)
2452 nr = global_page_state(NR_ACTIVE_FILE) +
2453 global_page_state(NR_INACTIVE_FILE);
2455 if (nr_swap_pages > 0)
2456 nr += global_page_state(NR_ACTIVE_ANON) +
2457 global_page_state(NR_INACTIVE_ANON);
2462 unsigned long zone_reclaimable_pages(struct zone *zone)
2466 nr = zone_page_state(zone, NR_ACTIVE_FILE) +
2467 zone_page_state(zone, NR_INACTIVE_FILE);
2469 if (nr_swap_pages > 0)
2470 nr += zone_page_state(zone, NR_ACTIVE_ANON) +
2471 zone_page_state(zone, NR_INACTIVE_ANON);
2476 #ifdef CONFIG_HIBERNATION
2478 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2481 * Rather than trying to age LRUs the aim is to preserve the overall
2482 * LRU order by reclaiming preferentially
2483 * inactive > active > active referenced > active mapped
2485 unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
2487 struct reclaim_state reclaim_state;
2488 struct scan_control sc = {
2489 .gfp_mask = GFP_HIGHUSER_MOVABLE,
2493 .nr_to_reclaim = nr_to_reclaim,
2494 .hibernation_mode = 1,
2495 .swappiness = vm_swappiness,
2498 struct zonelist * zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
2499 struct task_struct *p = current;
2500 unsigned long nr_reclaimed;
2502 p->flags |= PF_MEMALLOC;
2503 lockdep_set_current_reclaim_state(sc.gfp_mask);
2504 reclaim_state.reclaimed_slab = 0;
2505 p->reclaim_state = &reclaim_state;
2507 nr_reclaimed = do_try_to_free_pages(zonelist, &sc);
2509 p->reclaim_state = NULL;
2510 lockdep_clear_current_reclaim_state();
2511 p->flags &= ~PF_MEMALLOC;
2513 return nr_reclaimed;
2515 #endif /* CONFIG_HIBERNATION */
2517 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2518 not required for correctness. So if the last cpu in a node goes
2519 away, we get changed to run anywhere: as the first one comes back,
2520 restore their cpu bindings. */
2521 static int __devinit cpu_callback(struct notifier_block *nfb,
2522 unsigned long action, void *hcpu)
2526 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2527 for_each_node_state(nid, N_HIGH_MEMORY) {
2528 pg_data_t *pgdat = NODE_DATA(nid);
2529 const struct cpumask *mask;
2531 mask = cpumask_of_node(pgdat->node_id);
2533 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2534 /* One of our CPUs online: restore mask */
2535 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2542 * This kswapd start function will be called by init and node-hot-add.
2543 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2545 int kswapd_run(int nid)
2547 pg_data_t *pgdat = NODE_DATA(nid);
2553 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2554 if (IS_ERR(pgdat->kswapd)) {
2555 /* failure at boot is fatal */
2556 BUG_ON(system_state == SYSTEM_BOOTING);
2557 printk("Failed to start kswapd on node %d\n",nid);
2564 * Called by memory hotplug when all memory in a node is offlined.
2566 void kswapd_stop(int nid)
2568 struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
2571 kthread_stop(kswapd);
2574 static int __init kswapd_init(void)
2579 for_each_node_state(nid, N_HIGH_MEMORY)
2581 hotcpu_notifier(cpu_callback, 0);
2585 module_init(kswapd_init)
2591 * If non-zero call zone_reclaim when the number of free pages falls below
2594 int zone_reclaim_mode __read_mostly;
2596 #define RECLAIM_OFF 0
2597 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2598 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2599 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2602 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2603 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2606 #define ZONE_RECLAIM_PRIORITY 4
2609 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2612 int sysctl_min_unmapped_ratio = 1;
2615 * If the number of slab pages in a zone grows beyond this percentage then
2616 * slab reclaim needs to occur.
2618 int sysctl_min_slab_ratio = 5;
2620 static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
2622 unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
2623 unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
2624 zone_page_state(zone, NR_ACTIVE_FILE);
2627 * It's possible for there to be more file mapped pages than
2628 * accounted for by the pages on the file LRU lists because
2629 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2631 return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
2634 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2635 static long zone_pagecache_reclaimable(struct zone *zone)
2637 long nr_pagecache_reclaimable;
2641 * If RECLAIM_SWAP is set, then all file pages are considered
2642 * potentially reclaimable. Otherwise, we have to worry about
2643 * pages like swapcache and zone_unmapped_file_pages() provides
2646 if (zone_reclaim_mode & RECLAIM_SWAP)
2647 nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
2649 nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
2651 /* If we can't clean pages, remove dirty pages from consideration */
2652 if (!(zone_reclaim_mode & RECLAIM_WRITE))
2653 delta += zone_page_state(zone, NR_FILE_DIRTY);
2655 /* Watch for any possible underflows due to delta */
2656 if (unlikely(delta > nr_pagecache_reclaimable))
2657 delta = nr_pagecache_reclaimable;
2659 return nr_pagecache_reclaimable - delta;
2663 * Try to free up some pages from this zone through reclaim.
2665 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2667 /* Minimum pages needed in order to stay on node */
2668 const unsigned long nr_pages = 1 << order;
2669 struct task_struct *p = current;
2670 struct reclaim_state reclaim_state;
2672 struct scan_control sc = {
2673 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2674 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2676 .nr_to_reclaim = max_t(unsigned long, nr_pages,
2678 .gfp_mask = gfp_mask,
2679 .swappiness = vm_swappiness,
2682 unsigned long nr_slab_pages0, nr_slab_pages1;
2686 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2687 * and we also need to be able to write out pages for RECLAIM_WRITE
2690 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2691 lockdep_set_current_reclaim_state(gfp_mask);
2692 reclaim_state.reclaimed_slab = 0;
2693 p->reclaim_state = &reclaim_state;
2695 if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
2697 * Free memory by calling shrink zone with increasing
2698 * priorities until we have enough memory freed.
2700 priority = ZONE_RECLAIM_PRIORITY;
2702 shrink_zone(priority, zone, &sc);
2704 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2707 nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2708 if (nr_slab_pages0 > zone->min_slab_pages) {
2710 * shrink_slab() does not currently allow us to determine how
2711 * many pages were freed in this zone. So we take the current
2712 * number of slab pages and shake the slab until it is reduced
2713 * by the same nr_pages that we used for reclaiming unmapped
2716 * Note that shrink_slab will free memory on all zones and may
2720 unsigned long lru_pages = zone_reclaimable_pages(zone);
2722 /* No reclaimable slab or very low memory pressure */
2723 if (!shrink_slab(sc.nr_scanned, gfp_mask, lru_pages))
2726 /* Freed enough memory */
2727 nr_slab_pages1 = zone_page_state(zone,
2728 NR_SLAB_RECLAIMABLE);
2729 if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
2734 * Update nr_reclaimed by the number of slab pages we
2735 * reclaimed from this zone.
2737 nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2738 if (nr_slab_pages1 < nr_slab_pages0)
2739 sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
2742 p->reclaim_state = NULL;
2743 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2744 lockdep_clear_current_reclaim_state();
2745 return sc.nr_reclaimed >= nr_pages;
2748 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2754 * Zone reclaim reclaims unmapped file backed pages and
2755 * slab pages if we are over the defined limits.
2757 * A small portion of unmapped file backed pages is needed for
2758 * file I/O otherwise pages read by file I/O will be immediately
2759 * thrown out if the zone is overallocated. So we do not reclaim
2760 * if less than a specified percentage of the zone is used by
2761 * unmapped file backed pages.
2763 if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
2764 zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
2765 return ZONE_RECLAIM_FULL;
2767 if (zone->all_unreclaimable)
2768 return ZONE_RECLAIM_FULL;
2771 * Do not scan if the allocation should not be delayed.
2773 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2774 return ZONE_RECLAIM_NOSCAN;
2777 * Only run zone reclaim on the local zone or on zones that do not
2778 * have associated processors. This will favor the local processor
2779 * over remote processors and spread off node memory allocations
2780 * as wide as possible.
2782 node_id = zone_to_nid(zone);
2783 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2784 return ZONE_RECLAIM_NOSCAN;
2786 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2787 return ZONE_RECLAIM_NOSCAN;
2789 ret = __zone_reclaim(zone, gfp_mask, order);
2790 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2793 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
2800 * page_evictable - test whether a page is evictable
2801 * @page: the page to test
2802 * @vma: the VMA in which the page is or will be mapped, may be NULL
2804 * Test whether page is evictable--i.e., should be placed on active/inactive
2805 * lists vs unevictable list. The vma argument is !NULL when called from the
2806 * fault path to determine how to instantate a new page.
2808 * Reasons page might not be evictable:
2809 * (1) page's mapping marked unevictable
2810 * (2) page is part of an mlocked VMA
2813 int page_evictable(struct page *page, struct vm_area_struct *vma)
2816 if (mapping_unevictable(page_mapping(page)))
2819 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2826 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2827 * @page: page to check evictability and move to appropriate lru list
2828 * @zone: zone page is in
2830 * Checks a page for evictability and moves the page to the appropriate
2833 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2834 * have PageUnevictable set.
2836 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2838 VM_BUG_ON(PageActive(page));
2841 ClearPageUnevictable(page);
2842 if (page_evictable(page, NULL)) {
2843 enum lru_list l = page_lru_base_type(page);
2845 __dec_zone_state(zone, NR_UNEVICTABLE);
2846 list_move(&page->lru, &zone->lru[l].list);
2847 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2848 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2849 __count_vm_event(UNEVICTABLE_PGRESCUED);
2852 * rotate unevictable list
2854 SetPageUnevictable(page);
2855 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2856 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2857 if (page_evictable(page, NULL))
2863 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2864 * @mapping: struct address_space to scan for evictable pages
2866 * Scan all pages in mapping. Check unevictable pages for
2867 * evictability and move them to the appropriate zone lru list.
2869 void scan_mapping_unevictable_pages(struct address_space *mapping)
2872 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2875 struct pagevec pvec;
2877 if (mapping->nrpages == 0)
2880 pagevec_init(&pvec, 0);
2881 while (next < end &&
2882 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2888 for (i = 0; i < pagevec_count(&pvec); i++) {
2889 struct page *page = pvec.pages[i];
2890 pgoff_t page_index = page->index;
2891 struct zone *pagezone = page_zone(page);
2894 if (page_index > next)
2898 if (pagezone != zone) {
2900 spin_unlock_irq(&zone->lru_lock);
2902 spin_lock_irq(&zone->lru_lock);
2905 if (PageLRU(page) && PageUnevictable(page))
2906 check_move_unevictable_page(page, zone);
2909 spin_unlock_irq(&zone->lru_lock);
2910 pagevec_release(&pvec);
2912 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2918 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2919 * @zone - zone of which to scan the unevictable list
2921 * Scan @zone's unevictable LRU lists to check for pages that have become
2922 * evictable. Move those that have to @zone's inactive list where they
2923 * become candidates for reclaim, unless shrink_inactive_zone() decides
2924 * to reactivate them. Pages that are still unevictable are rotated
2925 * back onto @zone's unevictable list.
2927 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2928 static void scan_zone_unevictable_pages(struct zone *zone)
2930 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2932 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2934 while (nr_to_scan > 0) {
2935 unsigned long batch_size = min(nr_to_scan,
2936 SCAN_UNEVICTABLE_BATCH_SIZE);
2938 spin_lock_irq(&zone->lru_lock);
2939 for (scan = 0; scan < batch_size; scan++) {
2940 struct page *page = lru_to_page(l_unevictable);
2942 if (!trylock_page(page))
2945 prefetchw_prev_lru_page(page, l_unevictable, flags);
2947 if (likely(PageLRU(page) && PageUnevictable(page)))
2948 check_move_unevictable_page(page, zone);
2952 spin_unlock_irq(&zone->lru_lock);
2954 nr_to_scan -= batch_size;
2960 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2962 * A really big hammer: scan all zones' unevictable LRU lists to check for
2963 * pages that have become evictable. Move those back to the zones'
2964 * inactive list where they become candidates for reclaim.
2965 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2966 * and we add swap to the system. As such, it runs in the context of a task
2967 * that has possibly/probably made some previously unevictable pages
2970 static void scan_all_zones_unevictable_pages(void)
2974 for_each_zone(zone) {
2975 scan_zone_unevictable_pages(zone);
2980 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2981 * all nodes' unevictable lists for evictable pages
2983 unsigned long scan_unevictable_pages;
2985 int scan_unevictable_handler(struct ctl_table *table, int write,
2986 void __user *buffer,
2987 size_t *length, loff_t *ppos)
2989 proc_doulongvec_minmax(table, write, buffer, length, ppos);
2991 if (write && *(unsigned long *)table->data)
2992 scan_all_zones_unevictable_pages();
2994 scan_unevictable_pages = 0;
3000 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3001 * a specified node's per zone unevictable lists for evictable pages.
3004 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
3005 struct sysdev_attribute *attr,
3008 return sprintf(buf, "0\n"); /* always zero; should fit... */
3011 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
3012 struct sysdev_attribute *attr,
3013 const char *buf, size_t count)
3015 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
3018 unsigned long req = strict_strtoul(buf, 10, &res);
3021 return 1; /* zero is no-op */
3023 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
3024 if (!populated_zone(zone))
3026 scan_zone_unevictable_pages(zone);
3032 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
3033 read_scan_unevictable_node,
3034 write_scan_unevictable_node);
3036 int scan_unevictable_register_node(struct node *node)
3038 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
3041 void scan_unevictable_unregister_node(struct node *node)
3043 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);