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>
43 #include <asm/tlbflush.h>
44 #include <asm/div64.h>
46 #include <linux/swapops.h>
51 /* Incremented by the number of inactive pages that were scanned */
52 unsigned long nr_scanned;
54 /* This context's GFP mask */
59 /* Can pages be swapped as part of reclaim? */
62 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
63 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
64 * In this context, it doesn't matter that we scan the
65 * whole list at once. */
70 int all_unreclaimable;
74 /* Which cgroup do we reclaim from */
75 struct mem_cgroup *mem_cgroup;
77 /* Pluggable isolate pages callback */
78 unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst,
79 unsigned long *scanned, int order, int mode,
80 struct zone *z, struct mem_cgroup *mem_cont,
81 int active, int file);
84 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
86 #ifdef ARCH_HAS_PREFETCH
87 #define prefetch_prev_lru_page(_page, _base, _field) \
89 if ((_page)->lru.prev != _base) { \
92 prev = lru_to_page(&(_page->lru)); \
93 prefetch(&prev->_field); \
97 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
100 #ifdef ARCH_HAS_PREFETCHW
101 #define prefetchw_prev_lru_page(_page, _base, _field) \
103 if ((_page)->lru.prev != _base) { \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetchw(&prev->_field); \
111 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
115 * From 0 .. 100. Higher means more swappy.
117 int vm_swappiness = 60;
118 long vm_total_pages; /* The total number of pages which the VM controls */
120 static LIST_HEAD(shrinker_list);
121 static DECLARE_RWSEM(shrinker_rwsem);
123 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
124 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
126 #define scan_global_lru(sc) (1)
130 * Add a shrinker callback to be called from the vm
132 void register_shrinker(struct shrinker *shrinker)
135 down_write(&shrinker_rwsem);
136 list_add_tail(&shrinker->list, &shrinker_list);
137 up_write(&shrinker_rwsem);
139 EXPORT_SYMBOL(register_shrinker);
144 void unregister_shrinker(struct shrinker *shrinker)
146 down_write(&shrinker_rwsem);
147 list_del(&shrinker->list);
148 up_write(&shrinker_rwsem);
150 EXPORT_SYMBOL(unregister_shrinker);
152 #define SHRINK_BATCH 128
154 * Call the shrink functions to age shrinkable caches
156 * Here we assume it costs one seek to replace a lru page and that it also
157 * takes a seek to recreate a cache object. With this in mind we age equal
158 * percentages of the lru and ageable caches. This should balance the seeks
159 * generated by these structures.
161 * If the vm encountered mapped pages on the LRU it increase the pressure on
162 * slab to avoid swapping.
164 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
166 * `lru_pages' represents the number of on-LRU pages in all the zones which
167 * are eligible for the caller's allocation attempt. It is used for balancing
168 * slab reclaim versus page reclaim.
170 * Returns the number of slab objects which we shrunk.
172 unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
173 unsigned long lru_pages)
175 struct shrinker *shrinker;
176 unsigned long ret = 0;
179 scanned = SWAP_CLUSTER_MAX;
181 if (!down_read_trylock(&shrinker_rwsem))
182 return 1; /* Assume we'll be able to shrink next time */
184 list_for_each_entry(shrinker, &shrinker_list, list) {
185 unsigned long long delta;
186 unsigned long total_scan;
187 unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask);
189 delta = (4 * scanned) / shrinker->seeks;
191 do_div(delta, lru_pages + 1);
192 shrinker->nr += delta;
193 if (shrinker->nr < 0) {
194 printk(KERN_ERR "%s: nr=%ld\n",
195 __func__, shrinker->nr);
196 shrinker->nr = max_pass;
200 * Avoid risking looping forever due to too large nr value:
201 * never try to free more than twice the estimate number of
204 if (shrinker->nr > max_pass * 2)
205 shrinker->nr = max_pass * 2;
207 total_scan = shrinker->nr;
210 while (total_scan >= SHRINK_BATCH) {
211 long this_scan = SHRINK_BATCH;
215 nr_before = (*shrinker->shrink)(0, gfp_mask);
216 shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask);
217 if (shrink_ret == -1)
219 if (shrink_ret < nr_before)
220 ret += nr_before - shrink_ret;
221 count_vm_events(SLABS_SCANNED, this_scan);
222 total_scan -= this_scan;
227 shrinker->nr += total_scan;
229 up_read(&shrinker_rwsem);
233 /* Called without lock on whether page is mapped, so answer is unstable */
234 static inline int page_mapping_inuse(struct page *page)
236 struct address_space *mapping;
238 /* Page is in somebody's page tables. */
239 if (page_mapped(page))
242 /* Be more reluctant to reclaim swapcache than pagecache */
243 if (PageSwapCache(page))
246 mapping = page_mapping(page);
250 /* File is mmap'd by somebody? */
251 return mapping_mapped(mapping);
254 static inline int is_page_cache_freeable(struct page *page)
256 return page_count(page) - !!PagePrivate(page) == 2;
259 static int may_write_to_queue(struct backing_dev_info *bdi)
261 if (current->flags & PF_SWAPWRITE)
263 if (!bdi_write_congested(bdi))
265 if (bdi == current->backing_dev_info)
271 * We detected a synchronous write error writing a page out. Probably
272 * -ENOSPC. We need to propagate that into the address_space for a subsequent
273 * fsync(), msync() or close().
275 * The tricky part is that after writepage we cannot touch the mapping: nothing
276 * prevents it from being freed up. But we have a ref on the page and once
277 * that page is locked, the mapping is pinned.
279 * We're allowed to run sleeping lock_page() here because we know the caller has
282 static void handle_write_error(struct address_space *mapping,
283 struct page *page, int error)
286 if (page_mapping(page) == mapping)
287 mapping_set_error(mapping, error);
291 /* Request for sync pageout. */
297 /* possible outcome of pageout() */
299 /* failed to write page out, page is locked */
301 /* move page to the active list, page is locked */
303 /* page has been sent to the disk successfully, page is unlocked */
305 /* page is clean and locked */
310 * pageout is called by shrink_page_list() for each dirty page.
311 * Calls ->writepage().
313 static pageout_t pageout(struct page *page, struct address_space *mapping,
314 enum pageout_io sync_writeback)
317 * If the page is dirty, only perform writeback if that write
318 * will be non-blocking. To prevent this allocation from being
319 * stalled by pagecache activity. But note that there may be
320 * stalls if we need to run get_block(). We could test
321 * PagePrivate for that.
323 * If this process is currently in generic_file_write() against
324 * this page's queue, we can perform writeback even if that
327 * If the page is swapcache, write it back even if that would
328 * block, for some throttling. This happens by accident, because
329 * swap_backing_dev_info is bust: it doesn't reflect the
330 * congestion state of the swapdevs. Easy to fix, if needed.
331 * See swapfile.c:page_queue_congested().
333 if (!is_page_cache_freeable(page))
337 * Some data journaling orphaned pages can have
338 * page->mapping == NULL while being dirty with clean buffers.
340 if (PagePrivate(page)) {
341 if (try_to_free_buffers(page)) {
342 ClearPageDirty(page);
343 printk("%s: orphaned page\n", __func__);
349 if (mapping->a_ops->writepage == NULL)
350 return PAGE_ACTIVATE;
351 if (!may_write_to_queue(mapping->backing_dev_info))
354 if (clear_page_dirty_for_io(page)) {
356 struct writeback_control wbc = {
357 .sync_mode = WB_SYNC_NONE,
358 .nr_to_write = SWAP_CLUSTER_MAX,
360 .range_end = LLONG_MAX,
365 SetPageReclaim(page);
366 res = mapping->a_ops->writepage(page, &wbc);
368 handle_write_error(mapping, page, res);
369 if (res == AOP_WRITEPAGE_ACTIVATE) {
370 ClearPageReclaim(page);
371 return PAGE_ACTIVATE;
375 * Wait on writeback if requested to. This happens when
376 * direct reclaiming a large contiguous area and the
377 * first attempt to free a range of pages fails.
379 if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC)
380 wait_on_page_writeback(page);
382 if (!PageWriteback(page)) {
383 /* synchronous write or broken a_ops? */
384 ClearPageReclaim(page);
386 inc_zone_page_state(page, NR_VMSCAN_WRITE);
394 * Same as remove_mapping, but if the page is removed from the mapping, it
395 * gets returned with a refcount of 0.
397 static int __remove_mapping(struct address_space *mapping, struct page *page)
399 BUG_ON(!PageLocked(page));
400 BUG_ON(mapping != page_mapping(page));
402 spin_lock_irq(&mapping->tree_lock);
404 * The non racy check for a busy page.
406 * Must be careful with the order of the tests. When someone has
407 * a ref to the page, it may be possible that they dirty it then
408 * drop the reference. So if PageDirty is tested before page_count
409 * here, then the following race may occur:
411 * get_user_pages(&page);
412 * [user mapping goes away]
414 * !PageDirty(page) [good]
415 * SetPageDirty(page);
417 * !page_count(page) [good, discard it]
419 * [oops, our write_to data is lost]
421 * Reversing the order of the tests ensures such a situation cannot
422 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
423 * load is not satisfied before that of page->_count.
425 * Note that if SetPageDirty is always performed via set_page_dirty,
426 * and thus under tree_lock, then this ordering is not required.
428 if (!page_freeze_refs(page, 2))
430 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
431 if (unlikely(PageDirty(page))) {
432 page_unfreeze_refs(page, 2);
436 if (PageSwapCache(page)) {
437 swp_entry_t swap = { .val = page_private(page) };
438 __delete_from_swap_cache(page);
439 spin_unlock_irq(&mapping->tree_lock);
442 __remove_from_page_cache(page);
443 spin_unlock_irq(&mapping->tree_lock);
449 spin_unlock_irq(&mapping->tree_lock);
454 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
455 * someone else has a ref on the page, abort and return 0. If it was
456 * successfully detached, return 1. Assumes the caller has a single ref on
459 int remove_mapping(struct address_space *mapping, struct page *page)
461 if (__remove_mapping(mapping, page)) {
463 * Unfreezing the refcount with 1 rather than 2 effectively
464 * drops the pagecache ref for us without requiring another
467 page_unfreeze_refs(page, 1);
474 * putback_lru_page - put previously isolated page onto appropriate LRU list
475 * @page: page to be put back to appropriate lru list
477 * Add previously isolated @page to appropriate LRU list.
478 * Page may still be unevictable for other reasons.
480 * lru_lock must not be held, interrupts must be enabled.
482 #ifdef CONFIG_UNEVICTABLE_LRU
483 void putback_lru_page(struct page *page)
486 int active = !!TestClearPageActive(page);
488 VM_BUG_ON(PageLRU(page));
491 ClearPageUnevictable(page);
493 if (page_evictable(page, NULL)) {
495 * For evictable pages, we can use the cache.
496 * In event of a race, worst case is we end up with an
497 * unevictable page on [in]active list.
498 * We know how to handle that.
500 lru = active + page_is_file_cache(page);
501 lru_cache_add_lru(page, lru);
504 * Put unevictable pages directly on zone's unevictable
507 lru = LRU_UNEVICTABLE;
508 add_page_to_unevictable_list(page);
510 mem_cgroup_move_lists(page, lru);
513 * page's status can change while we move it among lru. If an evictable
514 * page is on unevictable list, it never be freed. To avoid that,
515 * check after we added it to the list, again.
517 if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
518 if (!isolate_lru_page(page)) {
522 /* This means someone else dropped this page from LRU
523 * So, it will be freed or putback to LRU again. There is
524 * nothing to do here.
528 put_page(page); /* drop ref from isolate */
531 #else /* CONFIG_UNEVICTABLE_LRU */
533 void putback_lru_page(struct page *page)
536 VM_BUG_ON(PageLRU(page));
538 lru = !!TestClearPageActive(page) + page_is_file_cache(page);
539 lru_cache_add_lru(page, lru);
540 mem_cgroup_move_lists(page, lru);
543 #endif /* CONFIG_UNEVICTABLE_LRU */
547 * shrink_page_list() returns the number of reclaimed pages
549 static unsigned long shrink_page_list(struct list_head *page_list,
550 struct scan_control *sc,
551 enum pageout_io sync_writeback)
553 LIST_HEAD(ret_pages);
554 struct pagevec freed_pvec;
556 unsigned long nr_reclaimed = 0;
560 pagevec_init(&freed_pvec, 1);
561 while (!list_empty(page_list)) {
562 struct address_space *mapping;
569 page = lru_to_page(page_list);
570 list_del(&page->lru);
572 if (!trylock_page(page))
575 VM_BUG_ON(PageActive(page));
579 if (unlikely(!page_evictable(page, NULL))) {
581 putback_lru_page(page);
585 if (!sc->may_swap && page_mapped(page))
588 /* Double the slab pressure for mapped and swapcache pages */
589 if (page_mapped(page) || PageSwapCache(page))
592 may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
593 (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
595 if (PageWriteback(page)) {
597 * Synchronous reclaim is performed in two passes,
598 * first an asynchronous pass over the list to
599 * start parallel writeback, and a second synchronous
600 * pass to wait for the IO to complete. Wait here
601 * for any page for which writeback has already
604 if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs)
605 wait_on_page_writeback(page);
610 referenced = page_referenced(page, 1, sc->mem_cgroup);
611 /* In active use or really unfreeable? Activate it. */
612 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER &&
613 referenced && page_mapping_inuse(page))
614 goto activate_locked;
618 * Anonymous process memory has backing store?
619 * Try to allocate it some swap space here.
621 if (PageAnon(page) && !PageSwapCache(page))
622 if (!add_to_swap(page, GFP_ATOMIC))
623 goto activate_locked;
624 #endif /* CONFIG_SWAP */
626 mapping = page_mapping(page);
629 * The page is mapped into the page tables of one or more
630 * processes. Try to unmap it here.
632 if (page_mapped(page) && mapping) {
633 switch (try_to_unmap(page, 0)) {
635 goto activate_locked;
639 ; /* try to free the page below */
643 if (PageDirty(page)) {
644 if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced)
648 if (!sc->may_writepage)
651 /* Page is dirty, try to write it out here */
652 switch (pageout(page, mapping, sync_writeback)) {
656 goto activate_locked;
658 if (PageWriteback(page) || PageDirty(page))
661 * A synchronous write - probably a ramdisk. Go
662 * ahead and try to reclaim the page.
664 if (!trylock_page(page))
666 if (PageDirty(page) || PageWriteback(page))
668 mapping = page_mapping(page);
670 ; /* try to free the page below */
675 * If the page has buffers, try to free the buffer mappings
676 * associated with this page. If we succeed we try to free
679 * We do this even if the page is PageDirty().
680 * try_to_release_page() does not perform I/O, but it is
681 * possible for a page to have PageDirty set, but it is actually
682 * clean (all its buffers are clean). This happens if the
683 * buffers were written out directly, with submit_bh(). ext3
684 * will do this, as well as the blockdev mapping.
685 * try_to_release_page() will discover that cleanness and will
686 * drop the buffers and mark the page clean - it can be freed.
688 * Rarely, pages can have buffers and no ->mapping. These are
689 * the pages which were not successfully invalidated in
690 * truncate_complete_page(). We try to drop those buffers here
691 * and if that worked, and the page is no longer mapped into
692 * process address space (page_count == 1) it can be freed.
693 * Otherwise, leave the page on the LRU so it is swappable.
695 if (PagePrivate(page)) {
696 if (!try_to_release_page(page, sc->gfp_mask))
697 goto activate_locked;
698 if (!mapping && page_count(page) == 1) {
700 if (put_page_testzero(page))
704 * rare race with speculative reference.
705 * the speculative reference will free
706 * this page shortly, so we may
707 * increment nr_reclaimed here (and
708 * leave it off the LRU).
716 if (!mapping || !__remove_mapping(mapping, page))
722 if (!pagevec_add(&freed_pvec, page)) {
723 __pagevec_free(&freed_pvec);
724 pagevec_reinit(&freed_pvec);
729 /* Not a candidate for swapping, so reclaim swap space. */
730 if (PageSwapCache(page) && vm_swap_full())
731 remove_exclusive_swap_page_ref(page);
732 VM_BUG_ON(PageActive(page));
738 list_add(&page->lru, &ret_pages);
739 VM_BUG_ON(PageLRU(page));
741 list_splice(&ret_pages, page_list);
742 if (pagevec_count(&freed_pvec))
743 __pagevec_free(&freed_pvec);
744 count_vm_events(PGACTIVATE, pgactivate);
748 /* LRU Isolation modes. */
749 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
750 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
751 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
754 * Attempt to remove the specified page from its LRU. Only take this page
755 * if it is of the appropriate PageActive status. Pages which are being
756 * freed elsewhere are also ignored.
758 * page: page to consider
759 * mode: one of the LRU isolation modes defined above
761 * returns 0 on success, -ve errno on failure.
763 int __isolate_lru_page(struct page *page, int mode, int file)
767 /* Only take pages on the LRU. */
772 * When checking the active state, we need to be sure we are
773 * dealing with comparible boolean values. Take the logical not
776 if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode))
779 if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file))
783 * When this function is being called for lumpy reclaim, we
784 * initially look into all LRU pages, active, inactive and
785 * unevictable; only give shrink_page_list evictable pages.
787 if (PageUnevictable(page))
791 if (likely(get_page_unless_zero(page))) {
793 * Be careful not to clear PageLRU until after we're
794 * sure the page is not being freed elsewhere -- the
795 * page release code relies on it.
805 * zone->lru_lock is heavily contended. Some of the functions that
806 * shrink the lists perform better by taking out a batch of pages
807 * and working on them outside the LRU lock.
809 * For pagecache intensive workloads, this function is the hottest
810 * spot in the kernel (apart from copy_*_user functions).
812 * Appropriate locks must be held before calling this function.
814 * @nr_to_scan: The number of pages to look through on the list.
815 * @src: The LRU list to pull pages off.
816 * @dst: The temp list to put pages on to.
817 * @scanned: The number of pages that were scanned.
818 * @order: The caller's attempted allocation order
819 * @mode: One of the LRU isolation modes
820 * @file: True [1] if isolating file [!anon] pages
822 * returns how many pages were moved onto *@dst.
824 static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
825 struct list_head *src, struct list_head *dst,
826 unsigned long *scanned, int order, int mode, int file)
828 unsigned long nr_taken = 0;
831 for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
834 unsigned long end_pfn;
835 unsigned long page_pfn;
838 page = lru_to_page(src);
839 prefetchw_prev_lru_page(page, src, flags);
841 VM_BUG_ON(!PageLRU(page));
843 switch (__isolate_lru_page(page, mode, file)) {
845 list_move(&page->lru, dst);
850 /* else it is being freed elsewhere */
851 list_move(&page->lru, src);
862 * Attempt to take all pages in the order aligned region
863 * surrounding the tag page. Only take those pages of
864 * the same active state as that tag page. We may safely
865 * round the target page pfn down to the requested order
866 * as the mem_map is guarenteed valid out to MAX_ORDER,
867 * where that page is in a different zone we will detect
868 * it from its zone id and abort this block scan.
870 zone_id = page_zone_id(page);
871 page_pfn = page_to_pfn(page);
872 pfn = page_pfn & ~((1 << order) - 1);
873 end_pfn = pfn + (1 << order);
874 for (; pfn < end_pfn; pfn++) {
875 struct page *cursor_page;
877 /* The target page is in the block, ignore it. */
878 if (unlikely(pfn == page_pfn))
881 /* Avoid holes within the zone. */
882 if (unlikely(!pfn_valid_within(pfn)))
885 cursor_page = pfn_to_page(pfn);
887 /* Check that we have not crossed a zone boundary. */
888 if (unlikely(page_zone_id(cursor_page) != zone_id))
890 switch (__isolate_lru_page(cursor_page, mode, file)) {
892 list_move(&cursor_page->lru, dst);
898 /* else it is being freed elsewhere */
899 list_move(&cursor_page->lru, src);
901 break; /* ! on LRU or wrong list */
910 static unsigned long isolate_pages_global(unsigned long nr,
911 struct list_head *dst,
912 unsigned long *scanned, int order,
913 int mode, struct zone *z,
914 struct mem_cgroup *mem_cont,
915 int active, int file)
922 return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
927 * clear_active_flags() is a helper for shrink_active_list(), clearing
928 * any active bits from the pages in the list.
930 static unsigned long clear_active_flags(struct list_head *page_list,
937 list_for_each_entry(page, page_list, lru) {
938 lru = page_is_file_cache(page);
939 if (PageActive(page)) {
941 ClearPageActive(page);
951 * isolate_lru_page - tries to isolate a page from its LRU list
952 * @page: page to isolate from its LRU list
954 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
955 * vmstat statistic corresponding to whatever LRU list the page was on.
957 * Returns 0 if the page was removed from an LRU list.
958 * Returns -EBUSY if the page was not on an LRU list.
960 * The returned page will have PageLRU() cleared. If it was found on
961 * the active list, it will have PageActive set. If it was found on
962 * the unevictable list, it will have the PageUnevictable bit set. That flag
963 * may need to be cleared by the caller before letting the page go.
965 * The vmstat statistic corresponding to the list on which the page was
966 * found will be decremented.
969 * (1) Must be called with an elevated refcount on the page. This is a
970 * fundamentnal difference from isolate_lru_pages (which is called
971 * without a stable reference).
972 * (2) the lru_lock must not be held.
973 * (3) interrupts must be enabled.
975 int isolate_lru_page(struct page *page)
980 struct zone *zone = page_zone(page);
982 spin_lock_irq(&zone->lru_lock);
983 if (PageLRU(page) && get_page_unless_zero(page)) {
984 int lru = page_lru(page);
988 del_page_from_lru_list(zone, page, lru);
990 spin_unlock_irq(&zone->lru_lock);
996 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
999 static unsigned long shrink_inactive_list(unsigned long max_scan,
1000 struct zone *zone, struct scan_control *sc,
1001 int priority, int file)
1003 LIST_HEAD(page_list);
1004 struct pagevec pvec;
1005 unsigned long nr_scanned = 0;
1006 unsigned long nr_reclaimed = 0;
1008 pagevec_init(&pvec, 1);
1011 spin_lock_irq(&zone->lru_lock);
1014 unsigned long nr_taken;
1015 unsigned long nr_scan;
1016 unsigned long nr_freed;
1017 unsigned long nr_active;
1018 unsigned int count[NR_LRU_LISTS] = { 0, };
1019 int mode = ISOLATE_INACTIVE;
1022 * If we need a large contiguous chunk of memory, or have
1023 * trouble getting a small set of contiguous pages, we
1024 * will reclaim both active and inactive pages.
1026 * We use the same threshold as pageout congestion_wait below.
1028 if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
1029 mode = ISOLATE_BOTH;
1030 else if (sc->order && priority < DEF_PRIORITY - 2)
1031 mode = ISOLATE_BOTH;
1033 nr_taken = sc->isolate_pages(sc->swap_cluster_max,
1034 &page_list, &nr_scan, sc->order, mode,
1035 zone, sc->mem_cgroup, 0, file);
1036 nr_active = clear_active_flags(&page_list, count);
1037 __count_vm_events(PGDEACTIVATE, nr_active);
1039 __mod_zone_page_state(zone, NR_ACTIVE_FILE,
1040 -count[LRU_ACTIVE_FILE]);
1041 __mod_zone_page_state(zone, NR_INACTIVE_FILE,
1042 -count[LRU_INACTIVE_FILE]);
1043 __mod_zone_page_state(zone, NR_ACTIVE_ANON,
1044 -count[LRU_ACTIVE_ANON]);
1045 __mod_zone_page_state(zone, NR_INACTIVE_ANON,
1046 -count[LRU_INACTIVE_ANON]);
1048 if (scan_global_lru(sc)) {
1049 zone->pages_scanned += nr_scan;
1050 zone->recent_scanned[0] += count[LRU_INACTIVE_ANON];
1051 zone->recent_scanned[0] += count[LRU_ACTIVE_ANON];
1052 zone->recent_scanned[1] += count[LRU_INACTIVE_FILE];
1053 zone->recent_scanned[1] += count[LRU_ACTIVE_FILE];
1055 spin_unlock_irq(&zone->lru_lock);
1057 nr_scanned += nr_scan;
1058 nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
1061 * If we are direct reclaiming for contiguous pages and we do
1062 * not reclaim everything in the list, try again and wait
1063 * for IO to complete. This will stall high-order allocations
1064 * but that should be acceptable to the caller
1066 if (nr_freed < nr_taken && !current_is_kswapd() &&
1067 sc->order > PAGE_ALLOC_COSTLY_ORDER) {
1068 congestion_wait(WRITE, HZ/10);
1071 * The attempt at page out may have made some
1072 * of the pages active, mark them inactive again.
1074 nr_active = clear_active_flags(&page_list, count);
1075 count_vm_events(PGDEACTIVATE, nr_active);
1077 nr_freed += shrink_page_list(&page_list, sc,
1081 nr_reclaimed += nr_freed;
1082 local_irq_disable();
1083 if (current_is_kswapd()) {
1084 __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
1085 __count_vm_events(KSWAPD_STEAL, nr_freed);
1086 } else if (scan_global_lru(sc))
1087 __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
1089 __count_zone_vm_events(PGSTEAL, zone, nr_freed);
1094 spin_lock(&zone->lru_lock);
1096 * Put back any unfreeable pages.
1098 while (!list_empty(&page_list)) {
1100 page = lru_to_page(&page_list);
1101 VM_BUG_ON(PageLRU(page));
1102 list_del(&page->lru);
1103 if (unlikely(!page_evictable(page, NULL))) {
1104 spin_unlock_irq(&zone->lru_lock);
1105 putback_lru_page(page);
1106 spin_lock_irq(&zone->lru_lock);
1110 lru = page_lru(page);
1111 add_page_to_lru_list(zone, page, lru);
1112 mem_cgroup_move_lists(page, lru);
1113 if (PageActive(page) && scan_global_lru(sc)) {
1114 int file = !!page_is_file_cache(page);
1115 zone->recent_rotated[file]++;
1117 if (!pagevec_add(&pvec, page)) {
1118 spin_unlock_irq(&zone->lru_lock);
1119 __pagevec_release(&pvec);
1120 spin_lock_irq(&zone->lru_lock);
1123 } while (nr_scanned < max_scan);
1124 spin_unlock(&zone->lru_lock);
1127 pagevec_release(&pvec);
1128 return nr_reclaimed;
1132 * We are about to scan this zone at a certain priority level. If that priority
1133 * level is smaller (ie: more urgent) than the previous priority, then note
1134 * that priority level within the zone. This is done so that when the next
1135 * process comes in to scan this zone, it will immediately start out at this
1136 * priority level rather than having to build up its own scanning priority.
1137 * Here, this priority affects only the reclaim-mapped threshold.
1139 static inline void note_zone_scanning_priority(struct zone *zone, int priority)
1141 if (priority < zone->prev_priority)
1142 zone->prev_priority = priority;
1145 static inline int zone_is_near_oom(struct zone *zone)
1147 return zone->pages_scanned >= (zone_lru_pages(zone) * 3);
1151 * This moves pages from the active list to the inactive list.
1153 * We move them the other way if the page is referenced by one or more
1154 * processes, from rmap.
1156 * If the pages are mostly unmapped, the processing is fast and it is
1157 * appropriate to hold zone->lru_lock across the whole operation. But if
1158 * the pages are mapped, the processing is slow (page_referenced()) so we
1159 * should drop zone->lru_lock around each page. It's impossible to balance
1160 * this, so instead we remove the pages from the LRU while processing them.
1161 * It is safe to rely on PG_active against the non-LRU pages in here because
1162 * nobody will play with that bit on a non-LRU page.
1164 * The downside is that we have to touch page->_count against each page.
1165 * But we had to alter page->flags anyway.
1169 static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
1170 struct scan_control *sc, int priority, int file)
1172 unsigned long pgmoved;
1173 int pgdeactivate = 0;
1174 unsigned long pgscanned;
1175 LIST_HEAD(l_hold); /* The pages which were snipped off */
1176 LIST_HEAD(l_inactive);
1178 struct pagevec pvec;
1182 spin_lock_irq(&zone->lru_lock);
1183 pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order,
1184 ISOLATE_ACTIVE, zone,
1185 sc->mem_cgroup, 1, file);
1187 * zone->pages_scanned is used for detect zone's oom
1188 * mem_cgroup remembers nr_scan by itself.
1190 if (scan_global_lru(sc)) {
1191 zone->pages_scanned += pgscanned;
1192 zone->recent_scanned[!!file] += pgmoved;
1196 __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved);
1198 __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved);
1199 spin_unlock_irq(&zone->lru_lock);
1202 while (!list_empty(&l_hold)) {
1204 page = lru_to_page(&l_hold);
1205 list_del(&page->lru);
1207 if (unlikely(!page_evictable(page, NULL))) {
1208 putback_lru_page(page);
1212 /* page_referenced clears PageReferenced */
1213 if (page_mapping_inuse(page) &&
1214 page_referenced(page, 0, sc->mem_cgroup))
1217 list_add(&page->lru, &l_inactive);
1221 * Count referenced pages from currently used mappings as
1222 * rotated, even though they are moved to the inactive list.
1223 * This helps balance scan pressure between file and anonymous
1224 * pages in get_scan_ratio.
1226 zone->recent_rotated[!!file] += pgmoved;
1229 * Move the pages to the [file or anon] inactive list.
1231 pagevec_init(&pvec, 1);
1234 lru = LRU_BASE + file * LRU_FILE;
1235 spin_lock_irq(&zone->lru_lock);
1236 while (!list_empty(&l_inactive)) {
1237 page = lru_to_page(&l_inactive);
1238 prefetchw_prev_lru_page(page, &l_inactive, flags);
1239 VM_BUG_ON(PageLRU(page));
1241 VM_BUG_ON(!PageActive(page));
1242 ClearPageActive(page);
1244 list_move(&page->lru, &zone->lru[lru].list);
1245 mem_cgroup_move_lists(page, lru);
1247 if (!pagevec_add(&pvec, page)) {
1248 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1249 spin_unlock_irq(&zone->lru_lock);
1250 pgdeactivate += pgmoved;
1252 if (buffer_heads_over_limit)
1253 pagevec_strip(&pvec);
1254 __pagevec_release(&pvec);
1255 spin_lock_irq(&zone->lru_lock);
1258 __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
1259 pgdeactivate += pgmoved;
1260 if (buffer_heads_over_limit) {
1261 spin_unlock_irq(&zone->lru_lock);
1262 pagevec_strip(&pvec);
1263 spin_lock_irq(&zone->lru_lock);
1265 __count_zone_vm_events(PGREFILL, zone, pgscanned);
1266 __count_vm_events(PGDEACTIVATE, pgdeactivate);
1267 spin_unlock_irq(&zone->lru_lock);
1269 pagevec_swap_free(&pvec);
1271 pagevec_release(&pvec);
1274 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
1275 struct zone *zone, struct scan_control *sc, int priority)
1277 int file = is_file_lru(lru);
1279 if (lru == LRU_ACTIVE_FILE) {
1280 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1284 if (lru == LRU_ACTIVE_ANON &&
1285 (!scan_global_lru(sc) || inactive_anon_is_low(zone))) {
1286 shrink_active_list(nr_to_scan, zone, sc, priority, file);
1289 return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
1293 * Determine how aggressively the anon and file LRU lists should be
1294 * scanned. The relative value of each set of LRU lists is determined
1295 * by looking at the fraction of the pages scanned we did rotate back
1296 * onto the active list instead of evict.
1298 * percent[0] specifies how much pressure to put on ram/swap backed
1299 * memory, while percent[1] determines pressure on the file LRUs.
1301 static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
1302 unsigned long *percent)
1304 unsigned long anon, file, free;
1305 unsigned long anon_prio, file_prio;
1306 unsigned long ap, fp;
1308 anon = zone_page_state(zone, NR_ACTIVE_ANON) +
1309 zone_page_state(zone, NR_INACTIVE_ANON);
1310 file = zone_page_state(zone, NR_ACTIVE_FILE) +
1311 zone_page_state(zone, NR_INACTIVE_FILE);
1312 free = zone_page_state(zone, NR_FREE_PAGES);
1314 /* If we have no swap space, do not bother scanning anon pages. */
1315 if (nr_swap_pages <= 0) {
1321 /* If we have very few page cache pages, force-scan anon pages. */
1322 if (unlikely(file + free <= zone->pages_high)) {
1329 * OK, so we have swap space and a fair amount of page cache
1330 * pages. We use the recently rotated / recently scanned
1331 * ratios to determine how valuable each cache is.
1333 * Because workloads change over time (and to avoid overflow)
1334 * we keep these statistics as a floating average, which ends
1335 * up weighing recent references more than old ones.
1337 * anon in [0], file in [1]
1339 if (unlikely(zone->recent_scanned[0] > anon / 4)) {
1340 spin_lock_irq(&zone->lru_lock);
1341 zone->recent_scanned[0] /= 2;
1342 zone->recent_rotated[0] /= 2;
1343 spin_unlock_irq(&zone->lru_lock);
1346 if (unlikely(zone->recent_scanned[1] > file / 4)) {
1347 spin_lock_irq(&zone->lru_lock);
1348 zone->recent_scanned[1] /= 2;
1349 zone->recent_rotated[1] /= 2;
1350 spin_unlock_irq(&zone->lru_lock);
1354 * With swappiness at 100, anonymous and file have the same priority.
1355 * This scanning priority is essentially the inverse of IO cost.
1357 anon_prio = sc->swappiness;
1358 file_prio = 200 - sc->swappiness;
1361 * anon recent_rotated[0]
1362 * %anon = 100 * ----------- / ----------------- * IO cost
1363 * anon + file rotate_sum
1365 ap = (anon_prio + 1) * (zone->recent_scanned[0] + 1);
1366 ap /= zone->recent_rotated[0] + 1;
1368 fp = (file_prio + 1) * (zone->recent_scanned[1] + 1);
1369 fp /= zone->recent_rotated[1] + 1;
1371 /* Normalize to percentages */
1372 percent[0] = 100 * ap / (ap + fp + 1);
1373 percent[1] = 100 - percent[0];
1378 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1380 static unsigned long shrink_zone(int priority, struct zone *zone,
1381 struct scan_control *sc)
1383 unsigned long nr[NR_LRU_LISTS];
1384 unsigned long nr_to_scan;
1385 unsigned long nr_reclaimed = 0;
1386 unsigned long percent[2]; /* anon @ 0; file @ 1 */
1389 get_scan_ratio(zone, sc, percent);
1391 for_each_evictable_lru(l) {
1392 if (scan_global_lru(sc)) {
1393 int file = is_file_lru(l);
1396 * Add one to nr_to_scan just to make sure that the
1397 * kernel will slowly sift through each list.
1399 scan = zone_page_state(zone, NR_LRU_BASE + l);
1402 scan = (scan * percent[file]) / 100;
1404 zone->lru[l].nr_scan += scan + 1;
1405 nr[l] = zone->lru[l].nr_scan;
1406 if (nr[l] >= sc->swap_cluster_max)
1407 zone->lru[l].nr_scan = 0;
1412 * This reclaim occurs not because zone memory shortage
1413 * but because memory controller hits its limit.
1414 * Don't modify zone reclaim related data.
1416 nr[l] = mem_cgroup_calc_reclaim(sc->mem_cgroup, zone,
1421 while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
1422 nr[LRU_INACTIVE_FILE]) {
1423 for_each_evictable_lru(l) {
1425 nr_to_scan = min(nr[l],
1426 (unsigned long)sc->swap_cluster_max);
1427 nr[l] -= nr_to_scan;
1429 nr_reclaimed += shrink_list(l, nr_to_scan,
1430 zone, sc, priority);
1436 * Even if we did not try to evict anon pages at all, we want to
1437 * rebalance the anon lru active/inactive ratio.
1439 if (!scan_global_lru(sc) || inactive_anon_is_low(zone))
1440 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1441 else if (!scan_global_lru(sc))
1442 shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
1444 throttle_vm_writeout(sc->gfp_mask);
1445 return nr_reclaimed;
1449 * This is the direct reclaim path, for page-allocating processes. We only
1450 * try to reclaim pages from zones which will satisfy the caller's allocation
1453 * We reclaim from a zone even if that zone is over pages_high. Because:
1454 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1456 * b) The zones may be over pages_high but they must go *over* pages_high to
1457 * satisfy the `incremental min' zone defense algorithm.
1459 * Returns the number of reclaimed pages.
1461 * If a zone is deemed to be full of pinned pages then just give it a light
1462 * scan then give up on it.
1464 static unsigned long shrink_zones(int priority, struct zonelist *zonelist,
1465 struct scan_control *sc)
1467 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1468 unsigned long nr_reclaimed = 0;
1472 sc->all_unreclaimable = 1;
1473 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1474 if (!populated_zone(zone))
1477 * Take care memory controller reclaiming has small influence
1480 if (scan_global_lru(sc)) {
1481 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1483 note_zone_scanning_priority(zone, priority);
1485 if (zone_is_all_unreclaimable(zone) &&
1486 priority != DEF_PRIORITY)
1487 continue; /* Let kswapd poll it */
1488 sc->all_unreclaimable = 0;
1491 * Ignore cpuset limitation here. We just want to reduce
1492 * # of used pages by us regardless of memory shortage.
1494 sc->all_unreclaimable = 0;
1495 mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
1499 nr_reclaimed += shrink_zone(priority, zone, sc);
1502 return nr_reclaimed;
1506 * This is the main entry point to direct page reclaim.
1508 * If a full scan of the inactive list fails to free enough memory then we
1509 * are "out of memory" and something needs to be killed.
1511 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1512 * high - the zone may be full of dirty or under-writeback pages, which this
1513 * caller can't do much about. We kick pdflush and take explicit naps in the
1514 * hope that some of these pages can be written. But if the allocating task
1515 * holds filesystem locks which prevent writeout this might not work, and the
1516 * allocation attempt will fail.
1518 * returns: 0, if no pages reclaimed
1519 * else, the number of pages reclaimed
1521 static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
1522 struct scan_control *sc)
1525 unsigned long ret = 0;
1526 unsigned long total_scanned = 0;
1527 unsigned long nr_reclaimed = 0;
1528 struct reclaim_state *reclaim_state = current->reclaim_state;
1529 unsigned long lru_pages = 0;
1532 enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
1534 delayacct_freepages_start();
1536 if (scan_global_lru(sc))
1537 count_vm_event(ALLOCSTALL);
1539 * mem_cgroup will not do shrink_slab.
1541 if (scan_global_lru(sc)) {
1542 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1544 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1547 lru_pages += zone_lru_pages(zone);
1551 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1554 disable_swap_token();
1555 nr_reclaimed += shrink_zones(priority, zonelist, sc);
1557 * Don't shrink slabs when reclaiming memory from
1558 * over limit cgroups
1560 if (scan_global_lru(sc)) {
1561 shrink_slab(sc->nr_scanned, sc->gfp_mask, lru_pages);
1562 if (reclaim_state) {
1563 nr_reclaimed += reclaim_state->reclaimed_slab;
1564 reclaim_state->reclaimed_slab = 0;
1567 total_scanned += sc->nr_scanned;
1568 if (nr_reclaimed >= sc->swap_cluster_max) {
1574 * Try to write back as many pages as we just scanned. This
1575 * tends to cause slow streaming writers to write data to the
1576 * disk smoothly, at the dirtying rate, which is nice. But
1577 * that's undesirable in laptop mode, where we *want* lumpy
1578 * writeout. So in laptop mode, write out the whole world.
1580 if (total_scanned > sc->swap_cluster_max +
1581 sc->swap_cluster_max / 2) {
1582 wakeup_pdflush(laptop_mode ? 0 : total_scanned);
1583 sc->may_writepage = 1;
1586 /* Take a nap, wait for some writeback to complete */
1587 if (sc->nr_scanned && priority < DEF_PRIORITY - 2)
1588 congestion_wait(WRITE, HZ/10);
1590 /* top priority shrink_zones still had more to do? don't OOM, then */
1591 if (!sc->all_unreclaimable && scan_global_lru(sc))
1595 * Now that we've scanned all the zones at this priority level, note
1596 * that level within the zone so that the next thread which performs
1597 * scanning of this zone will immediately start out at this priority
1598 * level. This affects only the decision whether or not to bring
1599 * mapped pages onto the inactive list.
1604 if (scan_global_lru(sc)) {
1605 for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
1607 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1610 zone->prev_priority = priority;
1613 mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
1615 delayacct_freepages_end();
1620 unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
1623 struct scan_control sc = {
1624 .gfp_mask = gfp_mask,
1625 .may_writepage = !laptop_mode,
1626 .swap_cluster_max = SWAP_CLUSTER_MAX,
1628 .swappiness = vm_swappiness,
1631 .isolate_pages = isolate_pages_global,
1634 return do_try_to_free_pages(zonelist, &sc);
1637 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1639 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
1642 struct scan_control sc = {
1643 .may_writepage = !laptop_mode,
1645 .swap_cluster_max = SWAP_CLUSTER_MAX,
1646 .swappiness = vm_swappiness,
1648 .mem_cgroup = mem_cont,
1649 .isolate_pages = mem_cgroup_isolate_pages,
1651 struct zonelist *zonelist;
1653 sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
1654 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
1655 zonelist = NODE_DATA(numa_node_id())->node_zonelists;
1656 return do_try_to_free_pages(zonelist, &sc);
1661 * For kswapd, balance_pgdat() will work across all this node's zones until
1662 * they are all at pages_high.
1664 * Returns the number of pages which were actually freed.
1666 * There is special handling here for zones which are full of pinned pages.
1667 * This can happen if the pages are all mlocked, or if they are all used by
1668 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1669 * What we do is to detect the case where all pages in the zone have been
1670 * scanned twice and there has been zero successful reclaim. Mark the zone as
1671 * dead and from now on, only perform a short scan. Basically we're polling
1672 * the zone for when the problem goes away.
1674 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1675 * zones which have free_pages > pages_high, but once a zone is found to have
1676 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1677 * of the number of free pages in the lower zones. This interoperates with
1678 * the page allocator fallback scheme to ensure that aging of pages is balanced
1681 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
1686 unsigned long total_scanned;
1687 unsigned long nr_reclaimed;
1688 struct reclaim_state *reclaim_state = current->reclaim_state;
1689 struct scan_control sc = {
1690 .gfp_mask = GFP_KERNEL,
1692 .swap_cluster_max = SWAP_CLUSTER_MAX,
1693 .swappiness = vm_swappiness,
1696 .isolate_pages = isolate_pages_global,
1699 * temp_priority is used to remember the scanning priority at which
1700 * this zone was successfully refilled to free_pages == pages_high.
1702 int temp_priority[MAX_NR_ZONES];
1707 sc.may_writepage = !laptop_mode;
1708 count_vm_event(PAGEOUTRUN);
1710 for (i = 0; i < pgdat->nr_zones; i++)
1711 temp_priority[i] = DEF_PRIORITY;
1713 for (priority = DEF_PRIORITY; priority >= 0; priority--) {
1714 int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
1715 unsigned long lru_pages = 0;
1717 /* The swap token gets in the way of swapout... */
1719 disable_swap_token();
1724 * Scan in the highmem->dma direction for the highest
1725 * zone which needs scanning
1727 for (i = pgdat->nr_zones - 1; i >= 0; i--) {
1728 struct zone *zone = pgdat->node_zones + i;
1730 if (!populated_zone(zone))
1733 if (zone_is_all_unreclaimable(zone) &&
1734 priority != DEF_PRIORITY)
1738 * Do some background aging of the anon list, to give
1739 * pages a chance to be referenced before reclaiming.
1741 if (inactive_anon_is_low(zone))
1742 shrink_active_list(SWAP_CLUSTER_MAX, zone,
1745 if (!zone_watermark_ok(zone, order, zone->pages_high,
1754 for (i = 0; i <= end_zone; i++) {
1755 struct zone *zone = pgdat->node_zones + i;
1757 lru_pages += zone_lru_pages(zone);
1761 * Now scan the zone in the dma->highmem direction, stopping
1762 * at the last zone which needs scanning.
1764 * We do this because the page allocator works in the opposite
1765 * direction. This prevents the page allocator from allocating
1766 * pages behind kswapd's direction of progress, which would
1767 * cause too much scanning of the lower zones.
1769 for (i = 0; i <= end_zone; i++) {
1770 struct zone *zone = pgdat->node_zones + i;
1773 if (!populated_zone(zone))
1776 if (zone_is_all_unreclaimable(zone) &&
1777 priority != DEF_PRIORITY)
1780 if (!zone_watermark_ok(zone, order, zone->pages_high,
1783 temp_priority[i] = priority;
1785 note_zone_scanning_priority(zone, priority);
1787 * We put equal pressure on every zone, unless one
1788 * zone has way too many pages free already.
1790 if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
1792 nr_reclaimed += shrink_zone(priority, zone, &sc);
1793 reclaim_state->reclaimed_slab = 0;
1794 nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
1796 nr_reclaimed += reclaim_state->reclaimed_slab;
1797 total_scanned += sc.nr_scanned;
1798 if (zone_is_all_unreclaimable(zone))
1800 if (nr_slab == 0 && zone->pages_scanned >=
1801 (zone_lru_pages(zone) * 6))
1803 ZONE_ALL_UNRECLAIMABLE);
1805 * If we've done a decent amount of scanning and
1806 * the reclaim ratio is low, start doing writepage
1807 * even in laptop mode
1809 if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
1810 total_scanned > nr_reclaimed + nr_reclaimed / 2)
1811 sc.may_writepage = 1;
1814 break; /* kswapd: all done */
1816 * OK, kswapd is getting into trouble. Take a nap, then take
1817 * another pass across the zones.
1819 if (total_scanned && priority < DEF_PRIORITY - 2)
1820 congestion_wait(WRITE, HZ/10);
1823 * We do this so kswapd doesn't build up large priorities for
1824 * example when it is freeing in parallel with allocators. It
1825 * matches the direct reclaim path behaviour in terms of impact
1826 * on zone->*_priority.
1828 if (nr_reclaimed >= SWAP_CLUSTER_MAX)
1833 * Note within each zone the priority level at which this zone was
1834 * brought into a happy state. So that the next thread which scans this
1835 * zone will start out at that priority level.
1837 for (i = 0; i < pgdat->nr_zones; i++) {
1838 struct zone *zone = pgdat->node_zones + i;
1840 zone->prev_priority = temp_priority[i];
1842 if (!all_zones_ok) {
1850 return nr_reclaimed;
1854 * The background pageout daemon, started as a kernel thread
1855 * from the init process.
1857 * This basically trickles out pages so that we have _some_
1858 * free memory available even if there is no other activity
1859 * that frees anything up. This is needed for things like routing
1860 * etc, where we otherwise might have all activity going on in
1861 * asynchronous contexts that cannot page things out.
1863 * If there are applications that are active memory-allocators
1864 * (most normal use), this basically shouldn't matter.
1866 static int kswapd(void *p)
1868 unsigned long order;
1869 pg_data_t *pgdat = (pg_data_t*)p;
1870 struct task_struct *tsk = current;
1872 struct reclaim_state reclaim_state = {
1873 .reclaimed_slab = 0,
1875 node_to_cpumask_ptr(cpumask, pgdat->node_id);
1877 if (!cpus_empty(*cpumask))
1878 set_cpus_allowed_ptr(tsk, cpumask);
1879 current->reclaim_state = &reclaim_state;
1882 * Tell the memory management that we're a "memory allocator",
1883 * and that if we need more memory we should get access to it
1884 * regardless (see "__alloc_pages()"). "kswapd" should
1885 * never get caught in the normal page freeing logic.
1887 * (Kswapd normally doesn't need memory anyway, but sometimes
1888 * you need a small amount of memory in order to be able to
1889 * page out something else, and this flag essentially protects
1890 * us from recursively trying to free more memory as we're
1891 * trying to free the first piece of memory in the first place).
1893 tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
1898 unsigned long new_order;
1900 prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
1901 new_order = pgdat->kswapd_max_order;
1902 pgdat->kswapd_max_order = 0;
1903 if (order < new_order) {
1905 * Don't sleep if someone wants a larger 'order'
1910 if (!freezing(current))
1913 order = pgdat->kswapd_max_order;
1915 finish_wait(&pgdat->kswapd_wait, &wait);
1917 if (!try_to_freeze()) {
1918 /* We can speed up thawing tasks if we don't call
1919 * balance_pgdat after returning from the refrigerator
1921 balance_pgdat(pgdat, order);
1928 * A zone is low on free memory, so wake its kswapd task to service it.
1930 void wakeup_kswapd(struct zone *zone, int order)
1934 if (!populated_zone(zone))
1937 pgdat = zone->zone_pgdat;
1938 if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
1940 if (pgdat->kswapd_max_order < order)
1941 pgdat->kswapd_max_order = order;
1942 if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
1944 if (!waitqueue_active(&pgdat->kswapd_wait))
1946 wake_up_interruptible(&pgdat->kswapd_wait);
1949 unsigned long global_lru_pages(void)
1951 return global_page_state(NR_ACTIVE_ANON)
1952 + global_page_state(NR_ACTIVE_FILE)
1953 + global_page_state(NR_INACTIVE_ANON)
1954 + global_page_state(NR_INACTIVE_FILE);
1959 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1960 * from LRU lists system-wide, for given pass and priority, and returns the
1961 * number of reclaimed pages
1963 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1965 static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
1966 int pass, struct scan_control *sc)
1969 unsigned long nr_to_scan, ret = 0;
1972 for_each_zone(zone) {
1974 if (!populated_zone(zone))
1977 if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY)
1980 for_each_evictable_lru(l) {
1981 /* For pass = 0, we don't shrink the active list */
1983 (l == LRU_ACTIVE || l == LRU_ACTIVE_FILE))
1986 zone->lru[l].nr_scan +=
1987 (zone_page_state(zone, NR_LRU_BASE + l)
1989 if (zone->lru[l].nr_scan >= nr_pages || pass > 3) {
1990 zone->lru[l].nr_scan = 0;
1991 nr_to_scan = min(nr_pages,
1992 zone_page_state(zone,
1994 ret += shrink_list(l, nr_to_scan, zone,
1996 if (ret >= nr_pages)
2006 * Try to free `nr_pages' of memory, system-wide, and return the number of
2009 * Rather than trying to age LRUs the aim is to preserve the overall
2010 * LRU order by reclaiming preferentially
2011 * inactive > active > active referenced > active mapped
2013 unsigned long shrink_all_memory(unsigned long nr_pages)
2015 unsigned long lru_pages, nr_slab;
2016 unsigned long ret = 0;
2018 struct reclaim_state reclaim_state;
2019 struct scan_control sc = {
2020 .gfp_mask = GFP_KERNEL,
2022 .swap_cluster_max = nr_pages,
2024 .swappiness = vm_swappiness,
2025 .isolate_pages = isolate_pages_global,
2028 current->reclaim_state = &reclaim_state;
2030 lru_pages = global_lru_pages();
2031 nr_slab = global_page_state(NR_SLAB_RECLAIMABLE);
2032 /* If slab caches are huge, it's better to hit them first */
2033 while (nr_slab >= lru_pages) {
2034 reclaim_state.reclaimed_slab = 0;
2035 shrink_slab(nr_pages, sc.gfp_mask, lru_pages);
2036 if (!reclaim_state.reclaimed_slab)
2039 ret += reclaim_state.reclaimed_slab;
2040 if (ret >= nr_pages)
2043 nr_slab -= reclaim_state.reclaimed_slab;
2047 * We try to shrink LRUs in 5 passes:
2048 * 0 = Reclaim from inactive_list only
2049 * 1 = Reclaim from active list but don't reclaim mapped
2050 * 2 = 2nd pass of type 1
2051 * 3 = Reclaim mapped (normal reclaim)
2052 * 4 = 2nd pass of type 3
2054 for (pass = 0; pass < 5; pass++) {
2057 /* Force reclaiming mapped pages in the passes #3 and #4 */
2060 sc.swappiness = 100;
2063 for (prio = DEF_PRIORITY; prio >= 0; prio--) {
2064 unsigned long nr_to_scan = nr_pages - ret;
2067 ret += shrink_all_zones(nr_to_scan, prio, pass, &sc);
2068 if (ret >= nr_pages)
2071 reclaim_state.reclaimed_slab = 0;
2072 shrink_slab(sc.nr_scanned, sc.gfp_mask,
2073 global_lru_pages());
2074 ret += reclaim_state.reclaimed_slab;
2075 if (ret >= nr_pages)
2078 if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
2079 congestion_wait(WRITE, HZ / 10);
2084 * If ret = 0, we could not shrink LRUs, but there may be something
2089 reclaim_state.reclaimed_slab = 0;
2090 shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages());
2091 ret += reclaim_state.reclaimed_slab;
2092 } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0);
2096 current->reclaim_state = NULL;
2102 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2103 not required for correctness. So if the last cpu in a node goes
2104 away, we get changed to run anywhere: as the first one comes back,
2105 restore their cpu bindings. */
2106 static int __devinit cpu_callback(struct notifier_block *nfb,
2107 unsigned long action, void *hcpu)
2111 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
2112 for_each_node_state(nid, N_HIGH_MEMORY) {
2113 pg_data_t *pgdat = NODE_DATA(nid);
2114 node_to_cpumask_ptr(mask, pgdat->node_id);
2116 if (any_online_cpu(*mask) < nr_cpu_ids)
2117 /* One of our CPUs online: restore mask */
2118 set_cpus_allowed_ptr(pgdat->kswapd, mask);
2125 * This kswapd start function will be called by init and node-hot-add.
2126 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2128 int kswapd_run(int nid)
2130 pg_data_t *pgdat = NODE_DATA(nid);
2136 pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
2137 if (IS_ERR(pgdat->kswapd)) {
2138 /* failure at boot is fatal */
2139 BUG_ON(system_state == SYSTEM_BOOTING);
2140 printk("Failed to start kswapd on node %d\n",nid);
2146 static int __init kswapd_init(void)
2151 for_each_node_state(nid, N_HIGH_MEMORY)
2153 hotcpu_notifier(cpu_callback, 0);
2157 module_init(kswapd_init)
2163 * If non-zero call zone_reclaim when the number of free pages falls below
2166 int zone_reclaim_mode __read_mostly;
2168 #define RECLAIM_OFF 0
2169 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2170 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2171 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2174 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2175 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2178 #define ZONE_RECLAIM_PRIORITY 4
2181 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2184 int sysctl_min_unmapped_ratio = 1;
2187 * If the number of slab pages in a zone grows beyond this percentage then
2188 * slab reclaim needs to occur.
2190 int sysctl_min_slab_ratio = 5;
2193 * Try to free up some pages from this zone through reclaim.
2195 static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2197 /* Minimum pages needed in order to stay on node */
2198 const unsigned long nr_pages = 1 << order;
2199 struct task_struct *p = current;
2200 struct reclaim_state reclaim_state;
2202 unsigned long nr_reclaimed = 0;
2203 struct scan_control sc = {
2204 .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
2205 .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP),
2206 .swap_cluster_max = max_t(unsigned long, nr_pages,
2208 .gfp_mask = gfp_mask,
2209 .swappiness = vm_swappiness,
2210 .isolate_pages = isolate_pages_global,
2212 unsigned long slab_reclaimable;
2214 disable_swap_token();
2217 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2218 * and we also need to be able to write out pages for RECLAIM_WRITE
2221 p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
2222 reclaim_state.reclaimed_slab = 0;
2223 p->reclaim_state = &reclaim_state;
2225 if (zone_page_state(zone, NR_FILE_PAGES) -
2226 zone_page_state(zone, NR_FILE_MAPPED) >
2227 zone->min_unmapped_pages) {
2229 * Free memory by calling shrink zone with increasing
2230 * priorities until we have enough memory freed.
2232 priority = ZONE_RECLAIM_PRIORITY;
2234 note_zone_scanning_priority(zone, priority);
2235 nr_reclaimed += shrink_zone(priority, zone, &sc);
2237 } while (priority >= 0 && nr_reclaimed < nr_pages);
2240 slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2241 if (slab_reclaimable > zone->min_slab_pages) {
2243 * shrink_slab() does not currently allow us to determine how
2244 * many pages were freed in this zone. So we take the current
2245 * number of slab pages and shake the slab until it is reduced
2246 * by the same nr_pages that we used for reclaiming unmapped
2249 * Note that shrink_slab will free memory on all zones and may
2252 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
2253 zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
2254 slab_reclaimable - nr_pages)
2258 * Update nr_reclaimed by the number of slab pages we
2259 * reclaimed from this zone.
2261 nr_reclaimed += slab_reclaimable -
2262 zone_page_state(zone, NR_SLAB_RECLAIMABLE);
2265 p->reclaim_state = NULL;
2266 current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
2267 return nr_reclaimed >= nr_pages;
2270 int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
2276 * Zone reclaim reclaims unmapped file backed pages and
2277 * slab pages if we are over the defined limits.
2279 * A small portion of unmapped file backed pages is needed for
2280 * file I/O otherwise pages read by file I/O will be immediately
2281 * thrown out if the zone is overallocated. So we do not reclaim
2282 * if less than a specified percentage of the zone is used by
2283 * unmapped file backed pages.
2285 if (zone_page_state(zone, NR_FILE_PAGES) -
2286 zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages
2287 && zone_page_state(zone, NR_SLAB_RECLAIMABLE)
2288 <= zone->min_slab_pages)
2291 if (zone_is_all_unreclaimable(zone))
2295 * Do not scan if the allocation should not be delayed.
2297 if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
2301 * Only run zone reclaim on the local zone or on zones that do not
2302 * have associated processors. This will favor the local processor
2303 * over remote processors and spread off node memory allocations
2304 * as wide as possible.
2306 node_id = zone_to_nid(zone);
2307 if (node_state(node_id, N_CPU) && node_id != numa_node_id())
2310 if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
2312 ret = __zone_reclaim(zone, gfp_mask, order);
2313 zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
2319 #ifdef CONFIG_UNEVICTABLE_LRU
2321 * page_evictable - test whether a page is evictable
2322 * @page: the page to test
2323 * @vma: the VMA in which the page is or will be mapped, may be NULL
2325 * Test whether page is evictable--i.e., should be placed on active/inactive
2326 * lists vs unevictable list.
2328 * Reasons page might not be evictable:
2329 * TODO - later patches
2331 int page_evictable(struct page *page, struct vm_area_struct *vma)
2334 /* TODO: test page [!]evictable conditions */