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 */