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/slab.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>
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned;
55 /* Number of pages freed so far during a call to shrink_zones() */
56 unsigned long nr_reclaimed;
58 /* This context's GFP mask */
63 /* Can mapped pages be reclaimed? */
66 /* Can pages be swapped as part of reclaim? */
69 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
70 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
71 * In this context, it doesn't matter that we scan the
72 * whole list at once. */
77 int all_unreclaimable;
81 /* Which cgroup do we reclaim from */
82 struct mem_cgroup *mem_cgroup;
85 * Nodemask of nodes allowed by the caller. If NULL, all nodes
90 /* Pluggable isolate pages callback */
91 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
92 unsigned long *scanned, int order, int mode,
93 struct zone *z, struct mem_cgroup *mem_cont,
94 int active, int file);
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_pages(struct zone *zone, struct scan_control *sc,
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 = (*shrinker->shrink)(0, gfp_mask);
221 delta = (4 * scanned) / shrinker->seeks;
223 do_div(delta, lru_pages + 1);
224 shrinker->nr += delta;
225 if (shrinker->nr < 0) {
226 printk(KERN_ERR "shrink_slab: %pF negative objects to "
228 shrinker->shrink, shrinker->nr);
229 shrinker->nr = max_pass;
233 * Avoid risking looping forever due to too large nr value:
234 * never try to free more than twice the estimate number of
237 if (shrinker->nr > max_pass * 2)
238 shrinker->nr = max_pass * 2;
240 total_scan = shrinker->nr;
243 while (total_scan >= SHRINK_BATCH) {
244 long this_scan = SHRINK_BATCH;
248 nr_before = (*shrinker->shrink)(0, gfp_mask);
249 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
250 if (shrink_ret == -1)
252 if (shrink_ret < nr_before)
253 ret += nr_before - shrink_ret;
254 count_vm_events(SLABS_SCANNED, this_scan);
255 total_scan -= this_scan;
260 shrinker->nr += total_scan;
262 up_read(&shrinker_rwsem);
266 /* Called without lock on whether page is mapped, so answer is unstable */
267 static inline int page_mapping_inuse(struct page *page)
269 struct address_space *mapping;
271 /* Page is in somebody's page tables. */
272 if (page_mapped(page))
275 /* Be more reluctant to reclaim swapcache than pagecache */
276 if (PageSwapCache(page))
279 mapping = page_mapping(page);
283 /* File is mmap'd by somebody? */
284 return mapping_mapped(mapping);
287 static inline int is_page_cache_freeable(struct page *page)
289 return page_count(page) - !!page_has_private(page) == 2;
292 static int may_write_to_queue(struct backing_dev_info *bdi)
294 if (current->flags & PF_SWAPWRITE)
296 if (!bdi_write_congested(bdi))
298 if (bdi == current->backing_dev_info)
304 * We detected a synchronous write error writing a page out. Probably
305 * -ENOSPC. We need to propagate that into the address_space for a subsequent
306 * fsync(), msync() or close().
308 * The tricky part is that after writepage we cannot touch the mapping: nothing
309 * prevents it from being freed up. But we have a ref on the page and once
310 * that page is locked, the mapping is pinned.
312 * We're allowed to run sleeping lock_page() here because we know the caller has
315 static void handle_write_error(struct address_space *mapping,
316 struct page *page, int error)
319 if (page_mapping(page) == mapping)
320 mapping_set_error(mapping, error);
324 /* Request for sync pageout. */
330 /* possible outcome of pageout() */
332 /* failed to write page out, page is locked */
334 /* move page to the active list, page is locked */
336 /* page has been sent to the disk successfully, page is unlocked */
338 /* page is clean and locked */
343 * pageout is called by shrink_page_list() for each dirty page.
344 * Calls ->writepage().
346 static pageout_t pageout(struct page *page, struct address_space *mapping,
347 enum pageout_io sync_writeback)
350 * If the page is dirty, only perform writeback if that write
351 * will be non-blocking. To prevent this allocation from being
352 * stalled by pagecache activity. But note that there may be
353 * stalls if we need to run get_block(). We could test
354 * PagePrivate for that.
356 * If this process is currently in generic_file_write() against
357 * this page's queue, we can perform writeback even if that
360 * If the page is swapcache, write it back even if that would
361 * block, for some throttling. This happens by accident, because
362 * swap_backing_dev_info is bust: it doesn't reflect the
363 * congestion state of the swapdevs. Easy to fix, if needed.
364 * See swapfile.c:page_queue_congested().
366 if (!is_page_cache_freeable(page))
370 * Some data journaling orphaned pages can have
371 * page->mapping == NULL while being dirty with clean buffers.
373 if (page_has_private(page)) {
374 if (try_to_free_buffers(page)) {
375 ClearPageDirty(page);
376 printk("%s: orphaned page\n", __func__);
382 if (mapping->a_ops->writepage == NULL)
383 return PAGE_ACTIVATE;
384 if (!may_write_to_queue(mapping->backing_dev_info))
387 if (clear_page_dirty_for_io(page)) {
389 struct writeback_control wbc = {
390 .sync_mode = WB_SYNC_NONE,
391 .nr_to_write = SWAP_CLUSTER_MAX,
393 .range_end = LLONG_MAX,
398 SetPageReclaim(page);
399 res = mapping->a_ops->writepage(page, &wbc);
401 handle_write_error(mapping, page, res);
402 if (res == AOP_WRITEPAGE_ACTIVATE) {
403 ClearPageReclaim(page);
404 return PAGE_ACTIVATE;
408 * Wait on writeback if requested to. This happens when
409 * direct reclaiming a large contiguous area and the
410 * first attempt to free a range of pages fails.
412 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
413 wait_on_page_writeback(page);
415 if (!PageWriteback(page)) {
416 /* synchronous write or broken a_ops? */
417 ClearPageReclaim(page);
419 inc_zone_page_state(page, NR_VMSCAN_WRITE);
427 * Same as remove_mapping, but if the page is removed from the mapping, it
428 * gets returned with a refcount of 0.
430 static int __remove_mapping(struct address_space *mapping, struct page *page)
432 BUG_ON(!PageLocked(page));
433 BUG_ON(mapping != page_mapping(page));
435 spin_lock_irq(&mapping->tree_lock);
437 * The non racy check for a busy page.
439 * Must be careful with the order of the tests. When someone has
440 * a ref to the page, it may be possible that they dirty it then
441 * drop the reference. So if PageDirty is tested before page_count
442 * here, then the following race may occur:
444 * get_user_pages(&page);
445 * [user mapping goes away]
447 * !PageDirty(page) [good]
448 * SetPageDirty(page);
450 * !page_count(page) [good, discard it]
452 * [oops, our write_to data is lost]
454 * Reversing the order of the tests ensures such a situation cannot
455 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
456 * load is not satisfied before that of page->_count.
458 * Note that if SetPageDirty is always performed via set_page_dirty,
459 * and thus under tree_lock, then this ordering is not required.
461 if (!page_freeze_refs(page, 2))
463 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
464 if (unlikely(PageDirty(page))) {
465 page_unfreeze_refs(page, 2);
469 if (PageSwapCache(page)) {
470 swp_entry_t swap = { .val = page_private(page) };
471 __delete_from_swap_cache(page);
472 spin_unlock_irq(&mapping->tree_lock);
473 mem_cgroup_uncharge_swapcache(page, swap);
476 __remove_from_page_cache(page);
477 spin_unlock_irq(&mapping->tree_lock);
478 mem_cgroup_uncharge_cache_page(page);
484 spin_unlock_irq(&mapping->tree_lock);
489 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
490 * someone else has a ref on the page, abort and return 0. If it was
491 * successfully detached, return 1. Assumes the caller has a single ref on
494 int remove_mapping(struct address_space *mapping, struct page *page)
496 if (__remove_mapping(mapping, page)) {
498 * Unfreezing the refcount with 1 rather than 2 effectively
499 * drops the pagecache ref for us without requiring another
502 page_unfreeze_refs(page, 1);
509 * putback_lru_page - put previously isolated page onto appropriate LRU list
510 * @page: page to be put back to appropriate lru list
512 * Add previously isolated @page to appropriate LRU list.
513 * Page may still be unevictable for other reasons.
515 * lru_lock must not be held, interrupts must be enabled.
517 #ifdef CONFIG_UNEVICTABLE_LRU
518 void putback_lru_page(struct page *page)
521 int active = !!TestClearPageActive(page);
522 int was_unevictable = PageUnevictable(page);
524 VM_BUG_ON(PageLRU(page));
527 ClearPageUnevictable(page);
529 if (page_evictable(page, NULL)) {
531 * For evictable pages, we can use the cache.
532 * In event of a race, worst case is we end up with an
533 * unevictable page on [in]active list.
534 * We know how to handle that.
536 lru = active + page_is_file_cache(page);
537 lru_cache_add_lru(page, lru);
540 * Put unevictable pages directly on zone's unevictable
543 lru = LRU_UNEVICTABLE;
544 add_page_to_unevictable_list(page);
548 * page's status can change while we move it among lru. If an evictable
549 * page is on unevictable list, it never be freed. To avoid that,
550 * check after we added it to the list, again.
552 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
553 if (!isolate_lru_page(page)) {
557 /* This means someone else dropped this page from LRU
558 * So, it will be freed or putback to LRU again. There is
559 * nothing to do here.
563 if (was_unevictable && lru != LRU_UNEVICTABLE)
564 count_vm_event(UNEVICTABLE_PGRESCUED);
565 else if (!was_unevictable && lru == LRU_UNEVICTABLE)
566 count_vm_event(UNEVICTABLE_PGCULLED);
568 put_page(page); /* drop ref from isolate */
571 #else /* CONFIG_UNEVICTABLE_LRU */
573 void putback_lru_page(struct page *page)
576 VM_BUG_ON(PageLRU(page));
578 lru = !!TestClearPageActive(page) + page_is_file_cache(page);
579 lru_cache_add_lru(page, lru);
582 #endif /* CONFIG_UNEVICTABLE_LRU */
586 * shrink_page_list() returns the number of reclaimed pages
588 static unsigned long shrink_page_list(struct list_head *page_list,
589 struct scan_control *sc,
590 enum pageout_io sync_writeback)
592 LIST_HEAD(ret_pages);
593 struct pagevec freed_pvec;
595 unsigned long nr_reclaimed = 0;
599 pagevec_init(&freed_pvec, 1);
600 while (!list_empty(page_list)) {
601 struct address_space *mapping;
608 page = lru_to_page(page_list);
609 list_del(&page->lru);
611 if (!trylock_page(page))
614 VM_BUG_ON(PageActive(page));
618 if (unlikely(!page_evictable(page, NULL)))
621 if (!sc->may_unmap && page_mapped(page))
624 /* Double the slab pressure for mapped and swapcache pages */
625 if (page_mapped(page) || PageSwapCache(page))
628 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
629 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
631 if (PageWriteback(page)) {
633 * Synchronous reclaim is performed in two passes,
634 * first an asynchronous pass over the list to
635 * start parallel writeback, and a second synchronous
636 * pass to wait for the IO to complete. Wait here
637 * for any page for which writeback has already
640 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
641 wait_on_page_writeback(page);
646 referenced = page_referenced(page, 1, sc->mem_cgroup);
647 /* In active use or really unfreeable? Activate it. */
648 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
649 referenced && page_mapping_inuse(page))
650 goto activate_locked;
653 * Anonymous process memory has backing store?
654 * Try to allocate it some swap space here.
656 if (PageAnon(page) && !PageSwapCache(page)) {
657 if (!(sc->gfp_mask & __GFP_IO))
659 if (!add_to_swap(page))
660 goto activate_locked;
664 mapping = page_mapping(page);
667 * The page is mapped into the page tables of one or more
668 * processes. Try to unmap it here.
670 if (page_mapped(page) && mapping) {
671 switch (try_to_unmap(page, 0)) {
673 goto activate_locked;
679 ; /* try to free the page below */
683 if (PageDirty(page)) {
684 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
688 if (!sc->may_writepage)
691 /* Page is dirty, try to write it out here */
692 switch (pageout(page, mapping, sync_writeback)) {
696 goto activate_locked;
698 if (PageWriteback(page) || PageDirty(page))
701 * A synchronous write - probably a ramdisk. Go
702 * ahead and try to reclaim the page.
704 if (!trylock_page(page))
706 if (PageDirty(page) || PageWriteback(page))
708 mapping = page_mapping(page);
710 ; /* try to free the page below */
715 * If the page has buffers, try to free the buffer mappings
716 * associated with this page. If we succeed we try to free
719 * We do this even if the page is PageDirty().
720 * try_to_release_page() does not perform I/O, but it is
721 * possible for a page to have PageDirty set, but it is actually
722 * clean (all its buffers are clean). This happens if the
723 * buffers were written out directly, with submit_bh(). ext3
724 * will do this, as well as the blockdev mapping.
725 * try_to_release_page() will discover that cleanness and will
726 * drop the buffers and mark the page clean - it can be freed.
728 * Rarely, pages can have buffers and no ->mapping. These are
729 * the pages which were not successfully invalidated in
730 * truncate_complete_page(). We try to drop those buffers here
731 * and if that worked, and the page is no longer mapped into
732 * process address space (page_count == 1) it can be freed.
733 * Otherwise, leave the page on the LRU so it is swappable.
735 if (page_has_private(page)) {
736 if (!try_to_release_page(page, sc->gfp_mask))
737 goto activate_locked;
738 if (!mapping && page_count(page) == 1) {
740 if (put_page_testzero(page))
744 * rare race with speculative reference.
745 * the speculative reference will free
746 * this page shortly, so we may
747 * increment nr_reclaimed here (and
748 * leave it off the LRU).
756 if (!mapping || !__remove_mapping(mapping, page))
760 * At this point, we have no other references and there is
761 * no way to pick any more up (removed from LRU, removed
762 * from pagecache). Can use non-atomic bitops now (and
763 * we obviously don't have to worry about waking up a process
764 * waiting on the page lock, because there are no references.
766 __clear_page_locked(page);
769 if (!pagevec_add(&freed_pvec, page)) {
770 __pagevec_free(&freed_pvec);
771 pagevec_reinit(&freed_pvec);
776 if (PageSwapCache(page))
777 try_to_free_swap(page);
779 putback_lru_page(page);
783 /* Not a candidate for swapping, so reclaim swap space. */
784 if (PageSwapCache(page) && vm_swap_full())
785 try_to_free_swap(page);
786 VM_BUG_ON(PageActive(page));
792 list_add(&page->lru, &ret_pages);
793 VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
795 list_splice(&ret_pages, page_list);
796 if (pagevec_count(&freed_pvec))
797 __pagevec_free(&freed_pvec);
798 count_vm_events(PGACTIVATE, pgactivate);
802 /* LRU Isolation modes. */
803 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
804 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
805 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
808 * Attempt to remove the specified page from its LRU. Only take this page
809 * if it is of the appropriate PageActive status. Pages which are being
810 * freed elsewhere are also ignored.
812 * page: page to consider
813 * mode: one of the LRU isolation modes defined above
815 * returns 0 on success, -ve errno on failure.
817 int __isolate_lru_page(struct page *page, int mode, int file)
821 /* Only take pages on the LRU. */
826 * When checking the active state, we need to be sure we are
827 * dealing with comparible boolean values. Take the logical not
830 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
833 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
837 * When this function is being called for lumpy reclaim, we
838 * initially look into all LRU pages, active, inactive and
839 * unevictable; only give shrink_page_list evictable pages.
841 if (PageUnevictable(page))
846 if (likely(get_page_unless_zero(page))) {
848 * Be careful not to clear PageLRU until after we're
849 * sure the page is not being freed elsewhere -- the
850 * page release code relies on it.
854 mem_cgroup_del_lru(page);
861 * zone->lru_lock is heavily contended. Some of the functions that
862 * shrink the lists perform better by taking out a batch of pages
863 * and working on them outside the LRU lock.
865 * For pagecache intensive workloads, this function is the hottest
866 * spot in the kernel (apart from copy_*_user functions).
868 * Appropriate locks must be held before calling this function.
870 * @nr_to_scan: The number of pages to look through on the list.
871 * @src: The LRU list to pull pages off.
872 * @dst: The temp list to put pages on to.
873 * @scanned: The number of pages that were scanned.
874 * @order: The caller's attempted allocation order
875 * @mode: One of the LRU isolation modes
876 * @file: True [1] if isolating file [!anon] pages
878 * returns how many pages were moved onto *@dst.
880 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
881 struct list_head *src, struct list_head *dst,
882 unsigned long *scanned, int order, int mode, int file)
884 unsigned long nr_taken = 0;
887 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
890 unsigned long end_pfn;
891 unsigned long page_pfn;
894 page = lru_to_page(src);
895 prefetchw_prev_lru_page(page, src, flags);
897 VM_BUG_ON(!PageLRU(page));
899 switch (__isolate_lru_page(page, mode, file)) {
901 list_move(&page->lru, dst);
906 /* else it is being freed elsewhere */
907 list_move(&page->lru, src);
918 * Attempt to take all pages in the order aligned region
919 * surrounding the tag page. Only take those pages of
920 * the same active state as that tag page. We may safely
921 * round the target page pfn down to the requested order
922 * as the mem_map is guarenteed valid out to MAX_ORDER,
923 * where that page is in a different zone we will detect
924 * it from its zone id and abort this block scan.
926 zone_id = page_zone_id(page);
927 page_pfn = page_to_pfn(page);
928 pfn = page_pfn & ~((1 << order) - 1);
929 end_pfn = pfn + (1 << order);
930 for (; pfn < end_pfn; pfn++) {
931 struct page *cursor_page;
933 /* The target page is in the block, ignore it. */
934 if (unlikely(pfn == page_pfn))
937 /* Avoid holes within the zone. */
938 if (unlikely(!pfn_valid_within(pfn)))
941 cursor_page = pfn_to_page(pfn);
943 /* Check that we have not crossed a zone boundary. */
944 if (unlikely(page_zone_id(cursor_page) != zone_id))
946 switch (__isolate_lru_page(cursor_page, mode, file)) {
948 list_move(&cursor_page->lru, dst);
954 /* else it is being freed elsewhere */
955 list_move(&cursor_page->lru, src);
957 break; /* ! on LRU or wrong list */
966 static unsigned long isolate_pages_global(unsigned long nr,
967 struct list_head *dst,
968 unsigned long *scanned, int order,
969 int mode, struct zone *z,
970 struct mem_cgroup *mem_cont,
971 int active, int file)
978 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
983 * clear_active_flags() is a helper for shrink_active_list(), clearing
984 * any active bits from the pages in the list.
986 static unsigned long clear_active_flags(struct list_head *page_list,
993 list_for_each_entry(page, page_list, lru) {
994 lru = page_is_file_cache(page);
995 if (PageActive(page)) {
997 ClearPageActive(page);
1007 * isolate_lru_page - tries to isolate a page from its LRU list
1008 * @page: page to isolate from its LRU list
1010 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1011 * vmstat statistic corresponding to whatever LRU list the page was on.
1013 * Returns 0 if the page was removed from an LRU list.
1014 * Returns -EBUSY if the page was not on an LRU list.
1016 * The returned page will have PageLRU() cleared. If it was found on
1017 * the active list, it will have PageActive set. If it was found on
1018 * the unevictable list, it will have the PageUnevictable bit set. That flag
1019 * may need to be cleared by the caller before letting the page go.
1021 * The vmstat statistic corresponding to the list on which the page was
1022 * found will be decremented.
1025 * (1) Must be called with an elevated refcount on the page. This is a
1026 * fundamentnal difference from isolate_lru_pages (which is called
1027 * without a stable reference).
1028 * (2) the lru_lock must not be held.
1029 * (3) interrupts must be enabled.
1031 int isolate_lru_page(struct page *page)
1035 if (PageLRU(page)) {
1036 struct zone *zone = page_zone(page);
1038 spin_lock_irq(&zone->lru_lock);
1039 if (PageLRU(page) && get_page_unless_zero(page)) {
1040 int lru = page_lru(page);
1044 del_page_from_lru_list(zone, page, lru);
1046 spin_unlock_irq(&zone->lru_lock);
1052 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1053 * of reclaimed pages
1055 static unsigned long shrink_inactive_list(unsigned long max_scan,
1056 struct zone *zone, struct scan_control *sc,
1057 int priority, int file)
1059 LIST_HEAD(page_list);
1060 struct pagevec pvec;
1061 unsigned long nr_scanned = 0;
1062 unsigned long nr_reclaimed = 0;
1063 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1064 int lumpy_reclaim = 0;
1067 * If we need a large contiguous chunk of memory, or have
1068 * trouble getting a small set of contiguous pages, we
1069 * will reclaim both active and inactive pages.
1071 * We use the same threshold as pageout congestion_wait below.
1073 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1075 else if (sc->order && priority < DEF_PRIORITY - 2)
1078 pagevec_init(&pvec, 1);
1081 spin_lock_irq(&zone->lru_lock);
1084 unsigned long nr_taken;
1085 unsigned long nr_scan;
1086 unsigned long nr_freed;
1087 unsigned long nr_active;
1088 unsigned int count[NR_LRU_LISTS] = { 0, };
1089 int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
1091 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1092 &page_list, &nr_scan, sc->order, mode,
1093 zone, sc->mem_cgroup, 0, file);
1094 nr_active = clear_active_flags(&page_list, count);
1095 __count_vm_events(PGDEACTIVATE, nr_active);
1097 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1098 -count[LRU_ACTIVE_FILE]);
1099 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1100 -count[LRU_INACTIVE_FILE]);
1101 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1102 -count[LRU_ACTIVE_ANON]);
1103 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1104 -count[LRU_INACTIVE_ANON]);
1106 if (scanning_global_lru(sc))
1107 zone->pages_scanned += nr_scan;
1109 reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1110 reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1111 reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1112 reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1114 spin_unlock_irq(&zone->lru_lock);
1116 nr_scanned += nr_scan;
1117 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1120 * If we are direct reclaiming for contiguous pages and we do
1121 * not reclaim everything in the list, try again and wait
1122 * for IO to complete. This will stall high-order allocations
1123 * but that should be acceptable to the caller
1125 if (nr_freed < nr_taken && !current_is_kswapd() &&
1127 congestion_wait(WRITE, HZ/10);
1130 * The attempt at page out may have made some
1131 * of the pages active, mark them inactive again.
1133 nr_active = clear_active_flags(&page_list, count);
1134 count_vm_events(PGDEACTIVATE, nr_active);
1136 nr_freed += shrink_page_list(&page_list, sc,
1140 nr_reclaimed += nr_freed;
1141 local_irq_disable();
1142 if (current_is_kswapd()) {
1143 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1144 __count_vm_events(KSWAPD_STEAL, nr_freed);
1145 } else if (scanning_global_lru(sc))
1146 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1148 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1153 spin_lock(&zone->lru_lock);
1155 * Put back any unfreeable pages.
1157 while (!list_empty(&page_list)) {
1159 page = lru_to_page(&page_list);
1160 VM_BUG_ON(PageLRU(page));
1161 list_del(&page->lru);
1162 if (unlikely(!page_evictable(page, NULL))) {
1163 spin_unlock_irq(&zone->lru_lock);
1164 putback_lru_page(page);
1165 spin_lock_irq(&zone->lru_lock);
1169 lru = page_lru(page);
1170 add_page_to_lru_list(zone, page, lru);
1171 if (PageActive(page)) {
1172 int file = !!page_is_file_cache(page);
1173 reclaim_stat->recent_rotated[file]++;
1175 if (!pagevec_add(&pvec, page)) {
1176 spin_unlock_irq(&zone->lru_lock);
1177 __pagevec_release(&pvec);
1178 spin_lock_irq(&zone->lru_lock);
1181 } while (nr_scanned < max_scan);
1182 spin_unlock(&zone->lru_lock);
1185 pagevec_release(&pvec);
1186 return nr_reclaimed;
1190 * We are about to scan this zone at a certain priority level. If that priority
1191 * level is smaller (ie: more urgent) than the previous priority, then note
1192 * that priority level within the zone. This is done so that when the next
1193 * process comes in to scan this zone, it will immediately start out at this
1194 * priority level rather than having to build up its own scanning priority.
1195 * Here, this priority affects only the reclaim-mapped threshold.
1197 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1199 if (priority < zone->prev_priority)
1200 zone->prev_priority = priority;
1204 * This moves pages from the active list to the inactive list.
1206 * We move them the other way if the page is referenced by one or more
1207 * processes, from rmap.
1209 * If the pages are mostly unmapped, the processing is fast and it is
1210 * appropriate to hold zone->lru_lock across the whole operation. But if
1211 * the pages are mapped, the processing is slow (page_referenced()) so we
1212 * should drop zone->lru_lock around each page. It's impossible to balance
1213 * this, so instead we remove the pages from the LRU while processing them.
1214 * It is safe to rely on PG_active against the non-LRU pages in here because
1215 * nobody will play with that bit on a non-LRU page.
1217 * The downside is that we have to touch page->_count against each page.
1218 * But we had to alter page->flags anyway.
1222 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1223 struct scan_control *sc, int priority, int file)
1225 unsigned long pgmoved;
1226 int pgdeactivate = 0;
1227 unsigned long pgscanned;
1228 LIST_HEAD(l_hold); /* The pages which were snipped off */
1229 LIST_HEAD(l_inactive);
1231 struct pagevec pvec;
1233 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1236 spin_lock_irq(&zone->lru_lock);
1237 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1238 ISOLATE_ACTIVE, zone,
1239 sc->mem_cgroup, 1, file);
1241 * zone->pages_scanned is used for detect zone's oom
1242 * mem_cgroup remembers nr_scan by itself.
1244 if (scanning_global_lru(sc)) {
1245 zone->pages_scanned += pgscanned;
1247 reclaim_stat->recent_scanned[!!file] += pgmoved;
1250 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1252 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1253 spin_unlock_irq(&zone->lru_lock);
1256 while (!list_empty(&l_hold)) {
1258 page = lru_to_page(&l_hold);
1259 list_del(&page->lru);
1261 if (unlikely(!page_evictable(page, NULL))) {
1262 putback_lru_page(page);
1266 /* page_referenced clears PageReferenced */
1267 if (page_mapping_inuse(page) &&
1268 page_referenced(page, 0, sc->mem_cgroup))
1271 list_add(&page->lru, &l_inactive);
1275 * Move the pages to the [file or anon] inactive list.
1277 pagevec_init(&pvec, 1);
1278 lru = LRU_BASE + file * LRU_FILE;
1280 spin_lock_irq(&zone->lru_lock);
1282 * Count referenced pages from currently used mappings as
1283 * rotated, even though they are moved to the inactive list.
1284 * This helps balance scan pressure between file and anonymous
1285 * pages in get_scan_ratio.
1287 reclaim_stat->recent_rotated[!!file] += pgmoved;
1290 while (!list_empty(&l_inactive)) {
1291 page = lru_to_page(&l_inactive);
1292 prefetchw_prev_lru_page(page, &l_inactive, flags);
1293 VM_BUG_ON(PageLRU(page));
1295 VM_BUG_ON(!PageActive(page));
1296 ClearPageActive(page);
1298 list_move(&page->lru, &zone->lru[lru].list);
1299 mem_cgroup_add_lru_list(page, lru);
1301 if (!pagevec_add(&pvec, page)) {
1302 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1303 spin_unlock_irq(&zone->lru_lock);
1304 pgdeactivate += pgmoved;
1306 if (buffer_heads_over_limit)
1307 pagevec_strip(&pvec);
1308 __pagevec_release(&pvec);
1309 spin_lock_irq(&zone->lru_lock);
1312 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1313 pgdeactivate += pgmoved;
1314 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1315 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1316 spin_unlock_irq(&zone->lru_lock);
1317 if (buffer_heads_over_limit)
1318 pagevec_strip(&pvec);
1319 pagevec_release(&pvec);
1322 static int inactive_anon_is_low_global(struct zone *zone)
1324 unsigned long active, inactive;
1326 active = zone_page_state(zone, NR_ACTIVE_ANON);
1327 inactive = zone_page_state(zone, NR_INACTIVE_ANON);
1329 if (inactive * zone->inactive_ratio < active)
1336 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1337 * @zone: zone to check
1338 * @sc: scan control of this context
1340 * Returns true if the zone does not have enough inactive anon pages,
1341 * meaning some active anon pages need to be deactivated.
1343 static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
1347 if (scanning_global_lru(sc))
1348 low = inactive_anon_is_low_global(zone);
1350 low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup);
1354 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1355 struct zone *zone, struct scan_control *sc, int priority)
1357 int file = is_file_lru(lru);
1359 if (lru == LRU_ACTIVE_FILE) {
1360 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1364 if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
1365 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1368 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1372 * Determine how aggressively the anon and file LRU lists should be
1373 * scanned. The relative value of each set of LRU lists is determined
1374 * by looking at the fraction of the pages scanned we did rotate back
1375 * onto the active list instead of evict.
1377 * percent[0] specifies how much pressure to put on ram/swap backed
1378 * memory, while percent[1] determines pressure on the file LRUs.
1380 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1381 unsigned long *percent)
1383 unsigned long anon, file, free;
1384 unsigned long anon_prio, file_prio;
1385 unsigned long ap, fp;
1386 struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
1388 /* If we have no swap space, do not bother scanning anon pages. */
1389 if (!sc->may_swap || (nr_swap_pages <= 0)) {
1395 anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) +
1396 zone_nr_pages(zone, sc, LRU_INACTIVE_ANON);
1397 file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) +
1398 zone_nr_pages(zone, sc, LRU_INACTIVE_FILE);
1400 if (scanning_global_lru(sc)) {
1401 free = zone_page_state(zone, NR_FREE_PAGES);
1402 /* If we have very few page cache pages,
1403 force-scan anon pages. */
1404 if (unlikely(file + free <= zone->pages_high)) {
1412 * OK, so we have swap space and a fair amount of page cache
1413 * pages. We use the recently rotated / recently scanned
1414 * ratios to determine how valuable each cache is.
1416 * Because workloads change over time (and to avoid overflow)
1417 * we keep these statistics as a floating average, which ends
1418 * up weighing recent references more than old ones.
1420 * anon in [0], file in [1]
1422 if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
1423 spin_lock_irq(&zone->lru_lock);
1424 reclaim_stat->recent_scanned[0] /= 2;
1425 reclaim_stat->recent_rotated[0] /= 2;
1426 spin_unlock_irq(&zone->lru_lock);
1429 if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
1430 spin_lock_irq(&zone->lru_lock);
1431 reclaim_stat->recent_scanned[1] /= 2;
1432 reclaim_stat->recent_rotated[1] /= 2;
1433 spin_unlock_irq(&zone->lru_lock);
1437 * With swappiness at 100, anonymous and file have the same priority.
1438 * This scanning priority is essentially the inverse of IO cost.
1440 anon_prio = sc->swappiness;
1441 file_prio = 200 - sc->swappiness;
1444 * The amount of pressure on anon vs file pages is inversely
1445 * proportional to the fraction of recently scanned pages on
1446 * each list that were recently referenced and in active use.
1448 ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
1449 ap /= reclaim_stat->recent_rotated[0] + 1;
1451 fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
1452 fp /= reclaim_stat->recent_rotated[1] + 1;
1454 /* Normalize to percentages */
1455 percent[0] = 100 * ap / (ap + fp + 1);
1456 percent[1] = 100 - percent[0];
1461 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1463 static void shrink_zone(int priority, struct zone *zone,
1464 struct scan_control *sc)
1466 unsigned long nr[NR_LRU_LISTS];
1467 unsigned long nr_to_scan;
1468 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1470 unsigned long nr_reclaimed = sc->nr_reclaimed;
1471 unsigned long swap_cluster_max = sc->swap_cluster_max;
1473 get_scan_ratio(zone, sc, percent);
1475 for_each_evictable_lru(l) {
1476 int file = is_file_lru(l);
1479 scan = zone_nr_pages(zone, sc, l);
1482 scan = (scan * percent[file]) / 100;
1484 if (scanning_global_lru(sc)) {
1485 zone->lru[l].nr_scan += scan;
1486 nr[l] = zone->lru[l].nr_scan;
1487 if (nr[l] >= swap_cluster_max)
1488 zone->lru[l].nr_scan = 0;
1495 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1496 nr[LRU_INACTIVE_FILE]) {
1497 for_each_evictable_lru(l) {
1499 nr_to_scan = min(nr[l], swap_cluster_max);
1500 nr[l] -= nr_to_scan;
1502 nr_reclaimed += shrink_list(l, nr_to_scan,
1503 zone, sc, priority);
1507 * On large memory systems, scan >> priority can become
1508 * really large. This is fine for the starting priority;
1509 * we want to put equal scanning pressure on each zone.
1510 * However, if the VM has a harder time of freeing pages,
1511 * with multiple processes reclaiming pages, the total
1512 * freeing target can get unreasonably large.
1514 if (nr_reclaimed > swap_cluster_max &&
1515 priority < DEF_PRIORITY && !current_is_kswapd())
1519 sc->nr_reclaimed = nr_reclaimed;
1522 * Even if we did not try to evict anon pages at all, we want to
1523 * rebalance the anon lru active/inactive ratio.
1525 if (inactive_anon_is_low(zone, sc))
1526 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1528 throttle_vm_writeout(sc->gfp_mask);
1532 * This is the direct reclaim path, for page-allocating processes. We only
1533 * try to reclaim pages from zones which will satisfy the caller's allocation
1536 * We reclaim from a zone even if that zone is over pages_high. Because:
1537 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1539 * b) The zones may be over pages_high but they must go *over* pages_high to
1540 * satisfy the `incremental min' zone defense algorithm.
1542 * If a zone is deemed to be full of pinned pages then just give it a light
1543 * scan then give up on it.
1545 static void shrink_zones(int priority, struct zonelist *zonelist,
1546 struct scan_control *sc)
1548 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1552 sc->all_unreclaimable = 1;
1553 for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
1555 if (!populated_zone(zone))
1558 * Take care memory controller reclaiming has small influence
1561 if (scanning_global_lru(sc)) {
1562 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1564 note_zone_scanning_priority(zone, priority);
1566 if (zone_is_all_unreclaimable(zone) &&
1567 priority != DEF_PRIORITY)
1568 continue; /* Let kswapd poll it */
1569 sc->all_unreclaimable = 0;
1572 * Ignore cpuset limitation here. We just want to reduce
1573 * # of used pages by us regardless of memory shortage.
1575 sc->all_unreclaimable = 0;
1576 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1580 shrink_zone(priority, zone, sc);
1585 * This is the main entry point to direct page reclaim.
1587 * If a full scan of the inactive list fails to free enough memory then we
1588 * are "out of memory" and something needs to be killed.
1590 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1591 * high - the zone may be full of dirty or under-writeback pages, which this
1592 * caller can't do much about. We kick pdflush and take explicit naps in the
1593 * hope that some of these pages can be written. But if the allocating task
1594 * holds filesystem locks which prevent writeout this might not work, and the
1595 * allocation attempt will fail.
1597 * returns: 0, if no pages reclaimed
1598 * else, the number of pages reclaimed
1600 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1601 struct scan_control *sc)
1604 unsigned long ret = 0;
1605 unsigned long total_scanned = 0;
1606 struct reclaim_state *reclaim_state = current->reclaim_state;
1607 unsigned long lru_pages = 0;
1610 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1612 delayacct_freepages_start();
1614 if (scanning_global_lru(sc))
1615 count_vm_event(ALLOCSTALL);
1617 * mem_cgroup will not do shrink_slab.
1619 if (scanning_global_lru(sc)) {
1620 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1622 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1625 lru_pages += zone_lru_pages(zone);
1629 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1632 disable_swap_token();
1633 shrink_zones(priority, zonelist, sc);
1635 * Don't shrink slabs when reclaiming memory from
1636 * over limit cgroups
1638 if (scanning_global_lru(sc)) {
1639 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1640 if (reclaim_state) {
1641 sc->nr_reclaimed += reclaim_state->reclaimed_slab;
1642 reclaim_state->reclaimed_slab = 0;
1645 total_scanned += sc->nr_scanned;
1646 if (sc->nr_reclaimed >= sc->swap_cluster_max) {
1647 ret = sc->nr_reclaimed;
1652 * Try to write back as many pages as we just scanned. This
1653 * tends to cause slow streaming writers to write data to the
1654 * disk smoothly, at the dirtying rate, which is nice. But
1655 * that's undesirable in laptop mode, where we *want* lumpy
1656 * writeout. So in laptop mode, write out the whole world.
1658 if (total_scanned > sc->swap_cluster_max +
1659 sc->swap_cluster_max / 2) {
1660 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1661 sc->may_writepage = 1;
1664 /* Take a nap, wait for some writeback to complete */
1665 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1666 congestion_wait(WRITE, HZ/10);
1668 /* top priority shrink_zones still had more to do? don't OOM, then */
1669 if (!sc->all_unreclaimable && scanning_global_lru(sc))
1670 ret = sc->nr_reclaimed;
1673 * Now that we've scanned all the zones at this priority level, note
1674 * that level within the zone so that the next thread which performs
1675 * scanning of this zone will immediately start out at this priority
1676 * level. This affects only the decision whether or not to bring
1677 * mapped pages onto the inactive list.
1682 if (scanning_global_lru(sc)) {
1683 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1685 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1688 zone->prev_priority = priority;
1691 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1693 delayacct_freepages_end();
1698 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1699 gfp_t gfp_mask, nodemask_t *nodemask)
1701 struct scan_control sc = {
1702 .gfp_mask = gfp_mask,
1703 .may_writepage = !laptop_mode,
1704 .swap_cluster_max = SWAP_CLUSTER_MAX,
1707 .swappiness = vm_swappiness,
1710 .isolate_pages = isolate_pages_global,
1711 .nodemask = nodemask,
1714 return do_try_to_free_pages(zonelist, &sc);
1717 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1719 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1722 unsigned int swappiness)
1724 struct scan_control sc = {
1725 .may_writepage = !laptop_mode,
1727 .may_swap = !noswap,
1728 .swap_cluster_max = SWAP_CLUSTER_MAX,
1729 .swappiness = swappiness,
1731 .mem_cgroup = mem_cont,
1732 .isolate_pages = mem_cgroup_isolate_pages,
1733 .nodemask = NULL, /* we don't care the placement */
1735 struct zonelist *zonelist;
1737 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1738 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1739 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1740 return do_try_to_free_pages(zonelist, &sc);
1745 * For kswapd, balance_pgdat() will work across all this node's zones until
1746 * they are all at pages_high.
1748 * Returns the number of pages which were actually freed.
1750 * There is special handling here for zones which are full of pinned pages.
1751 * This can happen if the pages are all mlocked, or if they are all used by
1752 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1753 * What we do is to detect the case where all pages in the zone have been
1754 * scanned twice and there has been zero successful reclaim. Mark the zone as
1755 * dead and from now on, only perform a short scan. Basically we're polling
1756 * the zone for when the problem goes away.
1758 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1759 * zones which have free_pages > pages_high, but once a zone is found to have
1760 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1761 * of the number of free pages in the lower zones. This interoperates with
1762 * the page allocator fallback scheme to ensure that aging of pages is balanced
1765 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1770 unsigned long total_scanned;
1771 struct reclaim_state *reclaim_state = current->reclaim_state;
1772 struct scan_control sc = {
1773 .gfp_mask = GFP_KERNEL,
1776 .swap_cluster_max = SWAP_CLUSTER_MAX,
1777 .swappiness = vm_swappiness,
1780 .isolate_pages = isolate_pages_global,
1783 * temp_priority is used to remember the scanning priority at which
1784 * this zone was successfully refilled to free_pages == pages_high.
1786 int temp_priority[MAX_NR_ZONES];
1790 sc.nr_reclaimed = 0;
1791 sc.may_writepage = !laptop_mode;
1792 count_vm_event(PAGEOUTRUN);
1794 for (i = 0; i < pgdat->nr_zones; i++)
1795 temp_priority[i] = DEF_PRIORITY;
1797 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1798 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1799 unsigned long lru_pages = 0;
1801 /* The swap token gets in the way of swapout... */
1803 disable_swap_token();
1808 * Scan in the highmem->dma direction for the highest
1809 * zone which needs scanning
1811 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1812 struct zone *zone = pgdat->node_zones + i;
1814 if (!populated_zone(zone))
1817 if (zone_is_all_unreclaimable(zone) &&
1818 priority != DEF_PRIORITY)
1822 * Do some background aging of the anon list, to give
1823 * pages a chance to be referenced before reclaiming.
1825 if (inactive_anon_is_low(zone, &sc))
1826 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1829 if (!zone_watermark_ok(zone, order, zone->pages_high,
1838 for (i = 0; i <= end_zone; i++) {
1839 struct zone *zone = pgdat->node_zones + i;
1841 lru_pages += zone_lru_pages(zone);
1845 * Now scan the zone in the dma->highmem direction, stopping
1846 * at the last zone which needs scanning.
1848 * We do this because the page allocator works in the opposite
1849 * direction. This prevents the page allocator from allocating
1850 * pages behind kswapd's direction of progress, which would
1851 * cause too much scanning of the lower zones.
1853 for (i = 0; i <= end_zone; i++) {
1854 struct zone *zone = pgdat->node_zones + i;
1857 if (!populated_zone(zone))
1860 if (zone_is_all_unreclaimable(zone) &&
1861 priority != DEF_PRIORITY)
1864 if (!zone_watermark_ok(zone, order, zone->pages_high,
1867 temp_priority[i] = priority;
1869 note_zone_scanning_priority(zone, priority);
1871 * We put equal pressure on every zone, unless one
1872 * zone has way too many pages free already.
1874 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1876 shrink_zone(priority, zone, &sc);
1877 reclaim_state->reclaimed_slab = 0;
1878 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1880 sc.nr_reclaimed += reclaim_state->reclaimed_slab;
1881 total_scanned += sc.nr_scanned;
1882 if (zone_is_all_unreclaimable(zone))
1884 if (nr_slab == 0 && zone->pages_scanned >=
1885 (zone_lru_pages(zone) * 6))
1887 ZONE_ALL_UNRECLAIMABLE);
1889 * If we've done a decent amount of scanning and
1890 * the reclaim ratio is low, start doing writepage
1891 * even in laptop mode
1893 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1894 total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
1895 sc.may_writepage = 1;
1898 break; /* kswapd: all done */
1900 * OK, kswapd is getting into trouble. Take a nap, then take
1901 * another pass across the zones.
1903 if (total_scanned && priority < DEF_PRIORITY - 2)
1904 congestion_wait(WRITE, HZ/10);
1907 * We do this so kswapd doesn't build up large priorities for
1908 * example when it is freeing in parallel with allocators. It
1909 * matches the direct reclaim path behaviour in terms of impact
1910 * on zone->*_priority.
1912 if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
1917 * Note within each zone the priority level at which this zone was
1918 * brought into a happy state. So that the next thread which scans this
1919 * zone will start out at that priority level.
1921 for (i = 0; i < pgdat->nr_zones; i++) {
1922 struct zone *zone = pgdat->node_zones + i;
1924 zone->prev_priority = temp_priority[i];
1926 if (!all_zones_ok) {
1932 * Fragmentation may mean that the system cannot be
1933 * rebalanced for high-order allocations in all zones.
1934 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
1935 * it means the zones have been fully scanned and are still
1936 * not balanced. For high-order allocations, there is
1937 * little point trying all over again as kswapd may
1940 * Instead, recheck all watermarks at order-0 as they
1941 * are the most important. If watermarks are ok, kswapd will go
1942 * back to sleep. High-order users can still perform direct
1943 * reclaim if they wish.
1945 if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
1946 order = sc.order = 0;
1951 return sc.nr_reclaimed;
1955 * The background pageout daemon, started as a kernel thread
1956 * from the init process.
1958 * This basically trickles out pages so that we have _some_
1959 * free memory available even if there is no other activity
1960 * that frees anything up. This is needed for things like routing
1961 * etc, where we otherwise might have all activity going on in
1962 * asynchronous contexts that cannot page things out.
1964 * If there are applications that are active memory-allocators
1965 * (most normal use), this basically shouldn't matter.
1967 static int kswapd(void *p)
1969 unsigned long order;
1970 pg_data_t *pgdat = (pg_data_t*)p;
1971 struct task_struct *tsk = current;
1973 struct reclaim_state reclaim_state = {
1974 .reclaimed_slab = 0,
1976 const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
1978 lockdep_set_current_reclaim_state(GFP_KERNEL);
1980 if (!cpumask_empty(cpumask))
1981 set_cpus_allowed_ptr(tsk, cpumask);
1982 current->reclaim_state = &reclaim_state;
1985 * Tell the memory management that we're a "memory allocator",
1986 * and that if we need more memory we should get access to it
1987 * regardless (see "__alloc_pages()"). "kswapd" should
1988 * never get caught in the normal page freeing logic.
1990 * (Kswapd normally doesn't need memory anyway, but sometimes
1991 * you need a small amount of memory in order to be able to
1992 * page out something else, and this flag essentially protects
1993 * us from recursively trying to free more memory as we're
1994 * trying to free the first piece of memory in the first place).
1996 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
2001 unsigned long new_order;
2003 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
2004 new_order = pgdat->kswapd_max_order;
2005 pgdat->kswapd_max_order = 0;
2006 if (order < new_order) {
2008 * Don't sleep if someone wants a larger 'order'
2013 if (!freezing(current))
2016 order = pgdat->kswapd_max_order;
2018 finish_wait(&pgdat->kswapd_wait, &wait);
2020 if (!try_to_freeze()) {
2021 /* We can speed up thawing tasks if we don't call
2022 * balance_pgdat after returning from the refrigerator
2024 balance_pgdat(pgdat, order);
2031 * A zone is low on free memory, so wake its kswapd task to service it.
2033 void wakeup_kswapd(struct zone *zone, int order)
2037 if (!populated_zone(zone))
2040 pgdat = zone->zone_pgdat;
2041 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
2043 if (pgdat->kswapd_max_order < order)
2044 pgdat->kswapd_max_order = order;
2045 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
2047 if (!waitqueue_active(&pgdat->kswapd_wait))
2049 wake_up_interruptible(&pgdat->kswapd_wait);
2052 unsigned long global_lru_pages(void)
2054 return global_page_state(NR_ACTIVE_ANON)
2055 + global_page_state(NR_ACTIVE_FILE)
2056 + global_page_state(NR_INACTIVE_ANON)
2057 + global_page_state(NR_INACTIVE_FILE);
2060 #ifdef CONFIG_HIBERNATION
2062 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
2063 * from LRU lists system-wide, for given pass and priority.
2065 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
2067 static void shrink_all_zones(unsigned long nr_pages, int prio,
2068 int pass, struct scan_control *sc)
2071 unsigned long nr_reclaimed = 0;
2073 for_each_populated_zone(zone) {
2076 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
2079 for_each_evictable_lru(l) {
2080 enum zone_stat_item ls = NR_LRU_BASE + l;
2081 unsigned long lru_pages = zone_page_state(zone, ls);
2083 /* For pass = 0, we don't shrink the active list */
2084 if (pass == 0 && (l == LRU_ACTIVE_ANON ||
2085 l == LRU_ACTIVE_FILE))
2088 zone->lru[l].nr_scan += (lru_pages >> prio) + 1;
2089 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
2090 unsigned long nr_to_scan;
2092 zone->lru[l].nr_scan = 0;
2093 nr_to_scan = min(nr_pages, lru_pages);
2094 nr_reclaimed += shrink_list(l, nr_to_scan, zone,
2096 if (nr_reclaimed >= nr_pages) {
2097 sc->nr_reclaimed += nr_reclaimed;
2103 sc->nr_reclaimed += nr_reclaimed;
2107 * Try to free `nr_pages' of memory, system-wide, and return the number of
2110 * Rather than trying to age LRUs the aim is to preserve the overall
2111 * LRU order by reclaiming preferentially
2112 * inactive > active > active referenced > active mapped
2114 unsigned long shrink_all_memory(unsigned long nr_pages)
2116 unsigned long lru_pages, nr_slab;
2118 struct reclaim_state reclaim_state;
2119 struct scan_control sc = {
2120 .gfp_mask = GFP_KERNEL,
2123 .isolate_pages = isolate_pages_global,
2127 current->reclaim_state = &reclaim_state;
2129 lru_pages = global_lru_pages();
2130 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2131 /* If slab caches are huge, it's better to hit them first */
2132 while (nr_slab >= lru_pages) {
2133 reclaim_state.reclaimed_slab = 0;
2134 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2135 if (!reclaim_state.reclaimed_slab)
2138 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2139 if (sc.nr_reclaimed >= nr_pages)
2142 nr_slab -= reclaim_state.reclaimed_slab;
2146 * We try to shrink LRUs in 5 passes:
2147 * 0 = Reclaim from inactive_list only
2148 * 1 = Reclaim from active list but don't reclaim mapped
2149 * 2 = 2nd pass of type 1
2150 * 3 = Reclaim mapped (normal reclaim)
2151 * 4 = 2nd pass of type 3
2153 for (pass = 0; pass < 5; pass++) {
2156 /* Force reclaiming mapped pages in the passes #3 and #4 */
2160 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2161 unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed;
2164 sc.swap_cluster_max = nr_to_scan;
2165 shrink_all_zones(nr_to_scan, prio, pass, &sc);
2166 if (sc.nr_reclaimed >= nr_pages)
2169 reclaim_state.reclaimed_slab = 0;
2170 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2171 global_lru_pages());
2172 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2173 if (sc.nr_reclaimed >= nr_pages)
2176 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2177 congestion_wait(WRITE, HZ / 10);
2182 * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be
2183 * something in slab caches
2185 if (!sc.nr_reclaimed) {
2187 reclaim_state.reclaimed_slab = 0;
2188 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2189 sc.nr_reclaimed += reclaim_state.reclaimed_slab;
2190 } while (sc.nr_reclaimed < nr_pages &&
2191 reclaim_state.reclaimed_slab > 0);
2196 current->reclaim_state = NULL;
2198 return sc.nr_reclaimed;
2200 #endif /* CONFIG_HIBERNATION */
2202 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2203 not required for correctness. So if the last cpu in a node goes
2204 away, we get changed to run anywhere: as the first one comes back,
2205 restore their cpu bindings. */
2206 static int __devinit cpu_callback(struct notifier_block *nfb,
2207 unsigned long action, void *hcpu)
2211 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2212 for_each_node_state(nid, N_HIGH_MEMORY) {
2213 pg_data_t *pgdat = NODE_DATA(nid);
2214 const struct cpumask *mask;
2216 mask = cpumask_of_node(pgdat->node_id);
2218 if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
2219 /* One of our CPUs online: restore mask */
2220 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2227 * This kswapd start function will be called by init and node-hot-add.
2228 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2230 int kswapd_run(int nid)
2232 pg_data_t *pgdat = NODE_DATA(nid);
2238 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2239 if (IS_ERR(pgdat->kswapd)) {
2240 /* failure at boot is fatal */
2241 BUG_ON(system_state == SYSTEM_BOOTING);
2242 printk("Failed to start kswapd on node %d\n",nid);
2248 static int __init kswapd_init(void)
2253 for_each_node_state(nid, N_HIGH_MEMORY)
2255 hotcpu_notifier(cpu_callback, 0);
2259 module_init(kswapd_init)
2265 * If non-zero call zone_reclaim when the number of free pages falls below
2268 int zone_reclaim_mode __read_mostly;
2270 #define RECLAIM_OFF 0
2271 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2272 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2273 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2276 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2277 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2280 #define ZONE_RECLAIM_PRIORITY 4
2283 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2286 int sysctl_min_unmapped_ratio = 1;
2289 * If the number of slab pages in a zone grows beyond this percentage then
2290 * slab reclaim needs to occur.
2292 int sysctl_min_slab_ratio = 5;
2295 * Try to free up some pages from this zone through reclaim.
2297 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2299 /* Minimum pages needed in order to stay on node */
2300 const unsigned long nr_pages = 1 << order;
2301 struct task_struct *p = current;
2302 struct reclaim_state reclaim_state;
2304 struct scan_control sc = {
2305 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2306 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2308 .swap_cluster_max = max_t(unsigned long, nr_pages,
2310 .gfp_mask = gfp_mask,
2311 .swappiness = vm_swappiness,
2313 .isolate_pages = isolate_pages_global,
2315 unsigned long slab_reclaimable;
2317 disable_swap_token();
2320 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2321 * and we also need to be able to write out pages for RECLAIM_WRITE
2324 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2325 reclaim_state.reclaimed_slab = 0;
2326 p->reclaim_state = &reclaim_state;
2328 if (zone_page_state(zone, NR_FILE_PAGES) -
2329 zone_page_state(zone, NR_FILE_MAPPED) >
2330 zone->min_unmapped_pages) {
2332 * Free memory by calling shrink zone with increasing
2333 * priorities until we have enough memory freed.
2335 priority = ZONE_RECLAIM_PRIORITY;
2337 note_zone_scanning_priority(zone, priority);
2338 shrink_zone(priority, zone, &sc);
2340 } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
2343 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2344 if (slab_reclaimable > zone->min_slab_pages) {
2346 * shrink_slab() does not currently allow us to determine how
2347 * many pages were freed in this zone. So we take the current
2348 * number of slab pages and shake the slab until it is reduced
2349 * by the same nr_pages that we used for reclaiming unmapped
2352 * Note that shrink_slab will free memory on all zones and may
2355 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2356 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2357 slab_reclaimable - nr_pages)
2361 * Update nr_reclaimed by the number of slab pages we
2362 * reclaimed from this zone.
2364 sc.nr_reclaimed += slab_reclaimable -
2365 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2368 p->reclaim_state = NULL;
2369 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2370 return sc.nr_reclaimed >= nr_pages;
2373 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2379 * Zone reclaim reclaims unmapped file backed pages and
2380 * slab pages if we are over the defined limits.
2382 * A small portion of unmapped file backed pages is needed for
2383 * file I/O otherwise pages read by file I/O will be immediately
2384 * thrown out if the zone is overallocated. So we do not reclaim
2385 * if less than a specified percentage of the zone is used by
2386 * unmapped file backed pages.
2388 if (zone_page_state(zone, NR_FILE_PAGES) -
2389 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2390 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2391 <= zone->min_slab_pages)
2394 if (zone_is_all_unreclaimable(zone))
2398 * Do not scan if the allocation should not be delayed.
2400 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2404 * Only run zone reclaim on the local zone or on zones that do not
2405 * have associated processors. This will favor the local processor
2406 * over remote processors and spread off node memory allocations
2407 * as wide as possible.
2409 node_id = zone_to_nid(zone);
2410 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2413 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2415 ret = __zone_reclaim(zone, gfp_mask, order);
2416 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2422 #ifdef CONFIG_UNEVICTABLE_LRU
2424 * page_evictable - test whether a page is evictable
2425 * @page: the page to test
2426 * @vma: the VMA in which the page is or will be mapped, may be NULL
2428 * Test whether page is evictable--i.e., should be placed on active/inactive
2429 * lists vs unevictable list. The vma argument is !NULL when called from the
2430 * fault path to determine how to instantate a new page.
2432 * Reasons page might not be evictable:
2433 * (1) page's mapping marked unevictable
2434 * (2) page is part of an mlocked VMA
2437 int page_evictable(struct page *page, struct vm_area_struct *vma)
2440 if (mapping_unevictable(page_mapping(page)))
2443 if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
2450 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2451 * @page: page to check evictability and move to appropriate lru list
2452 * @zone: zone page is in
2454 * Checks a page for evictability and moves the page to the appropriate
2457 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2458 * have PageUnevictable set.
2460 static void check_move_unevictable_page(struct page *page, struct zone *zone)
2462 VM_BUG_ON(PageActive(page));
2465 ClearPageUnevictable(page);
2466 if (page_evictable(page, NULL)) {
2467 enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
2469 __dec_zone_state(zone, NR_UNEVICTABLE);
2470 list_move(&page->lru, &zone->lru[l].list);
2471 mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l);
2472 __inc_zone_state(zone, NR_INACTIVE_ANON + l);
2473 __count_vm_event(UNEVICTABLE_PGRESCUED);
2476 * rotate unevictable list
2478 SetPageUnevictable(page);
2479 list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
2480 mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE);
2481 if (page_evictable(page, NULL))
2487 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2488 * @mapping: struct address_space to scan for evictable pages
2490 * Scan all pages in mapping. Check unevictable pages for
2491 * evictability and move them to the appropriate zone lru list.
2493 void scan_mapping_unevictable_pages(struct address_space *mapping)
2496 pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >>
2499 struct pagevec pvec;
2501 if (mapping->nrpages == 0)
2504 pagevec_init(&pvec, 0);
2505 while (next < end &&
2506 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
2512 for (i = 0; i < pagevec_count(&pvec); i++) {
2513 struct page *page = pvec.pages[i];
2514 pgoff_t page_index = page->index;
2515 struct zone *pagezone = page_zone(page);
2518 if (page_index > next)
2522 if (pagezone != zone) {
2524 spin_unlock_irq(&zone->lru_lock);
2526 spin_lock_irq(&zone->lru_lock);
2529 if (PageLRU(page) && PageUnevictable(page))
2530 check_move_unevictable_page(page, zone);
2533 spin_unlock_irq(&zone->lru_lock);
2534 pagevec_release(&pvec);
2536 count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned);
2542 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2543 * @zone - zone of which to scan the unevictable list
2545 * Scan @zone's unevictable LRU lists to check for pages that have become
2546 * evictable. Move those that have to @zone's inactive list where they
2547 * become candidates for reclaim, unless shrink_inactive_zone() decides
2548 * to reactivate them. Pages that are still unevictable are rotated
2549 * back onto @zone's unevictable list.
2551 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2552 static void scan_zone_unevictable_pages(struct zone *zone)
2554 struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list;
2556 unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE);
2558 while (nr_to_scan > 0) {
2559 unsigned long batch_size = min(nr_to_scan,
2560 SCAN_UNEVICTABLE_BATCH_SIZE);
2562 spin_lock_irq(&zone->lru_lock);
2563 for (scan = 0; scan < batch_size; scan++) {
2564 struct page *page = lru_to_page(l_unevictable);
2566 if (!trylock_page(page))
2569 prefetchw_prev_lru_page(page, l_unevictable, flags);
2571 if (likely(PageLRU(page) && PageUnevictable(page)))
2572 check_move_unevictable_page(page, zone);
2576 spin_unlock_irq(&zone->lru_lock);
2578 nr_to_scan -= batch_size;
2584 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2586 * A really big hammer: scan all zones' unevictable LRU lists to check for
2587 * pages that have become evictable. Move those back to the zones'
2588 * inactive list where they become candidates for reclaim.
2589 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2590 * and we add swap to the system. As such, it runs in the context of a task
2591 * that has possibly/probably made some previously unevictable pages
2594 static void scan_all_zones_unevictable_pages(void)
2598 for_each_zone(zone) {
2599 scan_zone_unevictable_pages(zone);
2604 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2605 * all nodes' unevictable lists for evictable pages
2607 unsigned long scan_unevictable_pages;
2609 int scan_unevictable_handler(struct ctl_table *table, int write,
2610 struct file *file, void __user *buffer,
2611 size_t *length, loff_t *ppos)
2613 proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
2615 if (write && *(unsigned long *)table->data)
2616 scan_all_zones_unevictable_pages();
2618 scan_unevictable_pages = 0;
2623 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2624 * a specified node's per zone unevictable lists for evictable pages.
2627 static ssize_t read_scan_unevictable_node(struct sys_device *dev,
2628 struct sysdev_attribute *attr,
2631 return sprintf(buf, "0\n"); /* always zero; should fit... */
2634 static ssize_t write_scan_unevictable_node(struct sys_device *dev,
2635 struct sysdev_attribute *attr,
2636 const char *buf, size_t count)
2638 struct zone *node_zones = NODE_DATA(dev->id)->node_zones;
2641 unsigned long req = strict_strtoul(buf, 10, &res);
2644 return 1; /* zero is no-op */
2646 for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
2647 if (!populated_zone(zone))
2649 scan_zone_unevictable_pages(zone);
2655 static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
2656 read_scan_unevictable_node,
2657 write_scan_unevictable_node);
2659 int scan_unevictable_register_node(struct node *node)
2661 return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages);
2664 void scan_unevictable_unregister_node(struct node *node)
2666 sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages);