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 * shrink_page_list() returns the number of reclaimed pages
476 static unsigned long shrink_page_list(struct list_head
*page_list
,
477 struct scan_control
*sc
,
478 enum pageout_io sync_writeback
)
480 LIST_HEAD(ret_pages
);
481 struct pagevec freed_pvec
;
483 unsigned long nr_reclaimed
= 0;
487 pagevec_init(&freed_pvec
, 1);
488 while (!list_empty(page_list
)) {
489 struct address_space
*mapping
;
496 page
= lru_to_page(page_list
);
497 list_del(&page
->lru
);
499 if (!trylock_page(page
))
502 VM_BUG_ON(PageActive(page
));
506 if (!sc
->may_swap
&& page_mapped(page
))
509 /* Double the slab pressure for mapped and swapcache pages */
510 if (page_mapped(page
) || PageSwapCache(page
))
513 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
514 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
516 if (PageWriteback(page
)) {
518 * Synchronous reclaim is performed in two passes,
519 * first an asynchronous pass over the list to
520 * start parallel writeback, and a second synchronous
521 * pass to wait for the IO to complete. Wait here
522 * for any page for which writeback has already
525 if (sync_writeback
== PAGEOUT_IO_SYNC
&& may_enter_fs
)
526 wait_on_page_writeback(page
);
531 referenced
= page_referenced(page
, 1, sc
->mem_cgroup
);
532 /* In active use or really unfreeable? Activate it. */
533 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&&
534 referenced
&& page_mapping_inuse(page
))
535 goto activate_locked
;
539 * Anonymous process memory has backing store?
540 * Try to allocate it some swap space here.
542 if (PageAnon(page
) && !PageSwapCache(page
))
543 if (!add_to_swap(page
, GFP_ATOMIC
))
544 goto activate_locked
;
545 #endif /* CONFIG_SWAP */
547 mapping
= page_mapping(page
);
550 * The page is mapped into the page tables of one or more
551 * processes. Try to unmap it here.
553 if (page_mapped(page
) && mapping
) {
554 switch (try_to_unmap(page
, 0)) {
556 goto activate_locked
;
560 ; /* try to free the page below */
564 if (PageDirty(page
)) {
565 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&& referenced
)
569 if (!sc
->may_writepage
)
572 /* Page is dirty, try to write it out here */
573 switch (pageout(page
, mapping
, sync_writeback
)) {
577 goto activate_locked
;
579 if (PageWriteback(page
) || PageDirty(page
))
582 * A synchronous write - probably a ramdisk. Go
583 * ahead and try to reclaim the page.
585 if (!trylock_page(page
))
587 if (PageDirty(page
) || PageWriteback(page
))
589 mapping
= page_mapping(page
);
591 ; /* try to free the page below */
596 * If the page has buffers, try to free the buffer mappings
597 * associated with this page. If we succeed we try to free
600 * We do this even if the page is PageDirty().
601 * try_to_release_page() does not perform I/O, but it is
602 * possible for a page to have PageDirty set, but it is actually
603 * clean (all its buffers are clean). This happens if the
604 * buffers were written out directly, with submit_bh(). ext3
605 * will do this, as well as the blockdev mapping.
606 * try_to_release_page() will discover that cleanness and will
607 * drop the buffers and mark the page clean - it can be freed.
609 * Rarely, pages can have buffers and no ->mapping. These are
610 * the pages which were not successfully invalidated in
611 * truncate_complete_page(). We try to drop those buffers here
612 * and if that worked, and the page is no longer mapped into
613 * process address space (page_count == 1) it can be freed.
614 * Otherwise, leave the page on the LRU so it is swappable.
616 if (PagePrivate(page
)) {
617 if (!try_to_release_page(page
, sc
->gfp_mask
))
618 goto activate_locked
;
619 if (!mapping
&& page_count(page
) == 1) {
621 if (put_page_testzero(page
))
625 * rare race with speculative reference.
626 * the speculative reference will free
627 * this page shortly, so we may
628 * increment nr_reclaimed here (and
629 * leave it off the LRU).
637 if (!mapping
|| !__remove_mapping(mapping
, page
))
643 if (!pagevec_add(&freed_pvec
, page
)) {
644 __pagevec_free(&freed_pvec
);
645 pagevec_reinit(&freed_pvec
);
650 /* Not a candidate for swapping, so reclaim swap space. */
651 if (PageSwapCache(page
) && vm_swap_full())
652 remove_exclusive_swap_page_ref(page
);
658 list_add(&page
->lru
, &ret_pages
);
659 VM_BUG_ON(PageLRU(page
));
661 list_splice(&ret_pages
, page_list
);
662 if (pagevec_count(&freed_pvec
))
663 __pagevec_free(&freed_pvec
);
664 count_vm_events(PGACTIVATE
, pgactivate
);
668 /* LRU Isolation modes. */
669 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
670 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
671 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
674 * Attempt to remove the specified page from its LRU. Only take this page
675 * if it is of the appropriate PageActive status. Pages which are being
676 * freed elsewhere are also ignored.
678 * page: page to consider
679 * mode: one of the LRU isolation modes defined above
681 * returns 0 on success, -ve errno on failure.
683 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
687 /* Only take pages on the LRU. */
692 * When checking the active state, we need to be sure we are
693 * dealing with comparible boolean values. Take the logical not
696 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
699 if (mode
!= ISOLATE_BOTH
&& (!page_is_file_cache(page
) != !file
))
703 if (likely(get_page_unless_zero(page
))) {
705 * Be careful not to clear PageLRU until after we're
706 * sure the page is not being freed elsewhere -- the
707 * page release code relies on it.
717 * zone->lru_lock is heavily contended. Some of the functions that
718 * shrink the lists perform better by taking out a batch of pages
719 * and working on them outside the LRU lock.
721 * For pagecache intensive workloads, this function is the hottest
722 * spot in the kernel (apart from copy_*_user functions).
724 * Appropriate locks must be held before calling this function.
726 * @nr_to_scan: The number of pages to look through on the list.
727 * @src: The LRU list to pull pages off.
728 * @dst: The temp list to put pages on to.
729 * @scanned: The number of pages that were scanned.
730 * @order: The caller's attempted allocation order
731 * @mode: One of the LRU isolation modes
732 * @file: True [1] if isolating file [!anon] pages
734 * returns how many pages were moved onto *@dst.
736 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
737 struct list_head
*src
, struct list_head
*dst
,
738 unsigned long *scanned
, int order
, int mode
, int file
)
740 unsigned long nr_taken
= 0;
743 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
746 unsigned long end_pfn
;
747 unsigned long page_pfn
;
750 page
= lru_to_page(src
);
751 prefetchw_prev_lru_page(page
, src
, flags
);
753 VM_BUG_ON(!PageLRU(page
));
755 switch (__isolate_lru_page(page
, mode
, file
)) {
757 list_move(&page
->lru
, dst
);
762 /* else it is being freed elsewhere */
763 list_move(&page
->lru
, src
);
774 * Attempt to take all pages in the order aligned region
775 * surrounding the tag page. Only take those pages of
776 * the same active state as that tag page. We may safely
777 * round the target page pfn down to the requested order
778 * as the mem_map is guarenteed valid out to MAX_ORDER,
779 * where that page is in a different zone we will detect
780 * it from its zone id and abort this block scan.
782 zone_id
= page_zone_id(page
);
783 page_pfn
= page_to_pfn(page
);
784 pfn
= page_pfn
& ~((1 << order
) - 1);
785 end_pfn
= pfn
+ (1 << order
);
786 for (; pfn
< end_pfn
; pfn
++) {
787 struct page
*cursor_page
;
789 /* The target page is in the block, ignore it. */
790 if (unlikely(pfn
== page_pfn
))
793 /* Avoid holes within the zone. */
794 if (unlikely(!pfn_valid_within(pfn
)))
797 cursor_page
= pfn_to_page(pfn
);
799 /* Check that we have not crossed a zone boundary. */
800 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
802 switch (__isolate_lru_page(cursor_page
, mode
, file
)) {
804 list_move(&cursor_page
->lru
, dst
);
810 /* else it is being freed elsewhere */
811 list_move(&cursor_page
->lru
, src
);
822 static unsigned long isolate_pages_global(unsigned long nr
,
823 struct list_head
*dst
,
824 unsigned long *scanned
, int order
,
825 int mode
, struct zone
*z
,
826 struct mem_cgroup
*mem_cont
,
827 int active
, int file
)
834 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
839 * clear_active_flags() is a helper for shrink_active_list(), clearing
840 * any active bits from the pages in the list.
842 static unsigned long clear_active_flags(struct list_head
*page_list
,
849 list_for_each_entry(page
, page_list
, lru
) {
850 lru
= page_is_file_cache(page
);
851 if (PageActive(page
)) {
853 ClearPageActive(page
);
863 * isolate_lru_page - tries to isolate a page from its LRU list
864 * @page: page to isolate from its LRU list
866 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
867 * vmstat statistic corresponding to whatever LRU list the page was on.
869 * Returns 0 if the page was removed from an LRU list.
870 * Returns -EBUSY if the page was not on an LRU list.
872 * The returned page will have PageLRU() cleared. If it was found on
873 * the active list, it will have PageActive set. That flag may need
874 * to be cleared by the caller before letting the page go.
876 * The vmstat statistic corresponding to the list on which the page was
877 * found will be decremented.
880 * (1) Must be called with an elevated refcount on the page. This is a
881 * fundamentnal difference from isolate_lru_pages (which is called
882 * without a stable reference).
883 * (2) the lru_lock must not be held.
884 * (3) interrupts must be enabled.
886 int isolate_lru_page(struct page
*page
)
891 struct zone
*zone
= page_zone(page
);
893 spin_lock_irq(&zone
->lru_lock
);
894 if (PageLRU(page
) && get_page_unless_zero(page
)) {
899 lru
+= page_is_file_cache(page
) + !!PageActive(page
);
900 del_page_from_lru_list(zone
, page
, lru
);
902 spin_unlock_irq(&zone
->lru_lock
);
908 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
911 static unsigned long shrink_inactive_list(unsigned long max_scan
,
912 struct zone
*zone
, struct scan_control
*sc
, int file
)
914 LIST_HEAD(page_list
);
916 unsigned long nr_scanned
= 0;
917 unsigned long nr_reclaimed
= 0;
919 pagevec_init(&pvec
, 1);
922 spin_lock_irq(&zone
->lru_lock
);
925 unsigned long nr_taken
;
926 unsigned long nr_scan
;
927 unsigned long nr_freed
;
928 unsigned long nr_active
;
929 unsigned int count
[NR_LRU_LISTS
] = { 0, };
930 int mode
= (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
) ?
931 ISOLATE_BOTH
: ISOLATE_INACTIVE
;
933 nr_taken
= sc
->isolate_pages(sc
->swap_cluster_max
,
934 &page_list
, &nr_scan
, sc
->order
, mode
,
935 zone
, sc
->mem_cgroup
, 0, file
);
936 nr_active
= clear_active_flags(&page_list
, count
);
937 __count_vm_events(PGDEACTIVATE
, nr_active
);
939 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
940 -count
[LRU_ACTIVE_FILE
]);
941 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
942 -count
[LRU_INACTIVE_FILE
]);
943 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
944 -count
[LRU_ACTIVE_ANON
]);
945 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
946 -count
[LRU_INACTIVE_ANON
]);
948 if (scan_global_lru(sc
)) {
949 zone
->pages_scanned
+= nr_scan
;
950 zone
->recent_scanned
[0] += count
[LRU_INACTIVE_ANON
];
951 zone
->recent_scanned
[0] += count
[LRU_ACTIVE_ANON
];
952 zone
->recent_scanned
[1] += count
[LRU_INACTIVE_FILE
];
953 zone
->recent_scanned
[1] += count
[LRU_ACTIVE_FILE
];
955 spin_unlock_irq(&zone
->lru_lock
);
957 nr_scanned
+= nr_scan
;
958 nr_freed
= shrink_page_list(&page_list
, sc
, PAGEOUT_IO_ASYNC
);
961 * If we are direct reclaiming for contiguous pages and we do
962 * not reclaim everything in the list, try again and wait
963 * for IO to complete. This will stall high-order allocations
964 * but that should be acceptable to the caller
966 if (nr_freed
< nr_taken
&& !current_is_kswapd() &&
967 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
) {
968 congestion_wait(WRITE
, HZ
/10);
971 * The attempt at page out may have made some
972 * of the pages active, mark them inactive again.
974 nr_active
= clear_active_flags(&page_list
, count
);
975 count_vm_events(PGDEACTIVATE
, nr_active
);
977 nr_freed
+= shrink_page_list(&page_list
, sc
,
981 nr_reclaimed
+= nr_freed
;
983 if (current_is_kswapd()) {
984 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scan
);
985 __count_vm_events(KSWAPD_STEAL
, nr_freed
);
986 } else if (scan_global_lru(sc
))
987 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scan
);
989 __count_zone_vm_events(PGSTEAL
, zone
, nr_freed
);
994 spin_lock(&zone
->lru_lock
);
996 * Put back any unfreeable pages.
998 while (!list_empty(&page_list
)) {
999 page
= lru_to_page(&page_list
);
1000 VM_BUG_ON(PageLRU(page
));
1002 list_del(&page
->lru
);
1003 add_page_to_lru_list(zone
, page
, page_lru(page
));
1004 if (PageActive(page
) && scan_global_lru(sc
)) {
1005 int file
= !!page_is_file_cache(page
);
1006 zone
->recent_rotated
[file
]++;
1008 if (!pagevec_add(&pvec
, page
)) {
1009 spin_unlock_irq(&zone
->lru_lock
);
1010 __pagevec_release(&pvec
);
1011 spin_lock_irq(&zone
->lru_lock
);
1014 } while (nr_scanned
< max_scan
);
1015 spin_unlock(&zone
->lru_lock
);
1018 pagevec_release(&pvec
);
1019 return nr_reclaimed
;
1023 * We are about to scan this zone at a certain priority level. If that priority
1024 * level is smaller (ie: more urgent) than the previous priority, then note
1025 * that priority level within the zone. This is done so that when the next
1026 * process comes in to scan this zone, it will immediately start out at this
1027 * priority level rather than having to build up its own scanning priority.
1028 * Here, this priority affects only the reclaim-mapped threshold.
1030 static inline void note_zone_scanning_priority(struct zone
*zone
, int priority
)
1032 if (priority
< zone
->prev_priority
)
1033 zone
->prev_priority
= priority
;
1036 static inline int zone_is_near_oom(struct zone
*zone
)
1038 return zone
->pages_scanned
>= (zone_lru_pages(zone
) * 3);
1042 * This moves pages from the active list to the inactive list.
1044 * We move them the other way if the page is referenced by one or more
1045 * processes, from rmap.
1047 * If the pages are mostly unmapped, the processing is fast and it is
1048 * appropriate to hold zone->lru_lock across the whole operation. But if
1049 * the pages are mapped, the processing is slow (page_referenced()) so we
1050 * should drop zone->lru_lock around each page. It's impossible to balance
1051 * this, so instead we remove the pages from the LRU while processing them.
1052 * It is safe to rely on PG_active against the non-LRU pages in here because
1053 * nobody will play with that bit on a non-LRU page.
1055 * The downside is that we have to touch page->_count against each page.
1056 * But we had to alter page->flags anyway.
1060 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1061 struct scan_control
*sc
, int priority
, int file
)
1063 unsigned long pgmoved
;
1064 int pgdeactivate
= 0;
1065 unsigned long pgscanned
;
1066 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1067 LIST_HEAD(l_active
);
1068 LIST_HEAD(l_inactive
);
1070 struct pagevec pvec
;
1074 spin_lock_irq(&zone
->lru_lock
);
1075 pgmoved
= sc
->isolate_pages(nr_pages
, &l_hold
, &pgscanned
, sc
->order
,
1076 ISOLATE_ACTIVE
, zone
,
1077 sc
->mem_cgroup
, 1, file
);
1079 * zone->pages_scanned is used for detect zone's oom
1080 * mem_cgroup remembers nr_scan by itself.
1082 if (scan_global_lru(sc
)) {
1083 zone
->pages_scanned
+= pgscanned
;
1084 zone
->recent_scanned
[!!file
] += pgmoved
;
1088 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -pgmoved
);
1090 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -pgmoved
);
1091 spin_unlock_irq(&zone
->lru_lock
);
1094 while (!list_empty(&l_hold
)) {
1096 page
= lru_to_page(&l_hold
);
1097 list_del(&page
->lru
);
1098 list_add(&page
->lru
, &l_inactive
);
1102 * Count the referenced pages as rotated, even when they are moved
1103 * to the inactive list. This helps balance scan pressure between
1104 * file and anonymous pages in get_scan_ratio.
1106 zone
->recent_rotated
[!!file
] += pgmoved
;
1109 * Now put the pages back on the appropriate [file or anon] inactive
1112 pagevec_init(&pvec
, 1);
1114 lru
= LRU_BASE
+ file
* LRU_FILE
;
1115 spin_lock_irq(&zone
->lru_lock
);
1116 while (!list_empty(&l_inactive
)) {
1117 page
= lru_to_page(&l_inactive
);
1118 prefetchw_prev_lru_page(page
, &l_inactive
, flags
);
1119 VM_BUG_ON(PageLRU(page
));
1121 VM_BUG_ON(!PageActive(page
));
1122 ClearPageActive(page
);
1124 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1125 mem_cgroup_move_lists(page
, false);
1127 if (!pagevec_add(&pvec
, page
)) {
1128 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1129 spin_unlock_irq(&zone
->lru_lock
);
1130 pgdeactivate
+= pgmoved
;
1132 if (buffer_heads_over_limit
)
1133 pagevec_strip(&pvec
);
1134 __pagevec_release(&pvec
);
1135 spin_lock_irq(&zone
->lru_lock
);
1138 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1139 pgdeactivate
+= pgmoved
;
1140 if (buffer_heads_over_limit
) {
1141 spin_unlock_irq(&zone
->lru_lock
);
1142 pagevec_strip(&pvec
);
1143 spin_lock_irq(&zone
->lru_lock
);
1147 lru
= LRU_ACTIVE
+ file
* LRU_FILE
;
1148 while (!list_empty(&l_active
)) {
1149 page
= lru_to_page(&l_active
);
1150 prefetchw_prev_lru_page(page
, &l_active
, flags
);
1151 VM_BUG_ON(PageLRU(page
));
1153 VM_BUG_ON(!PageActive(page
));
1155 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1156 mem_cgroup_move_lists(page
, true);
1158 if (!pagevec_add(&pvec
, page
)) {
1159 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1161 spin_unlock_irq(&zone
->lru_lock
);
1163 pagevec_swap_free(&pvec
);
1164 __pagevec_release(&pvec
);
1165 spin_lock_irq(&zone
->lru_lock
);
1168 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1170 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1171 __count_vm_events(PGDEACTIVATE
, pgdeactivate
);
1172 spin_unlock_irq(&zone
->lru_lock
);
1174 pagevec_swap_free(&pvec
);
1176 pagevec_release(&pvec
);
1179 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1180 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1182 int file
= is_file_lru(lru
);
1184 if (lru
== LRU_ACTIVE_FILE
) {
1185 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1189 if (lru
== LRU_ACTIVE_ANON
&&
1190 (!scan_global_lru(sc
) || inactive_anon_is_low(zone
))) {
1191 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1194 return shrink_inactive_list(nr_to_scan
, zone
, sc
, file
);
1198 * Determine how aggressively the anon and file LRU lists should be
1199 * scanned. The relative value of each set of LRU lists is determined
1200 * by looking at the fraction of the pages scanned we did rotate back
1201 * onto the active list instead of evict.
1203 * percent[0] specifies how much pressure to put on ram/swap backed
1204 * memory, while percent[1] determines pressure on the file LRUs.
1206 static void get_scan_ratio(struct zone
*zone
, struct scan_control
*sc
,
1207 unsigned long *percent
)
1209 unsigned long anon
, file
, free
;
1210 unsigned long anon_prio
, file_prio
;
1211 unsigned long ap
, fp
;
1213 anon
= zone_page_state(zone
, NR_ACTIVE_ANON
) +
1214 zone_page_state(zone
, NR_INACTIVE_ANON
);
1215 file
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
1216 zone_page_state(zone
, NR_INACTIVE_FILE
);
1217 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1219 /* If we have no swap space, do not bother scanning anon pages. */
1220 if (nr_swap_pages
<= 0) {
1226 /* If we have very few page cache pages, force-scan anon pages. */
1227 if (unlikely(file
+ free
<= zone
->pages_high
)) {
1234 * OK, so we have swap space and a fair amount of page cache
1235 * pages. We use the recently rotated / recently scanned
1236 * ratios to determine how valuable each cache is.
1238 * Because workloads change over time (and to avoid overflow)
1239 * we keep these statistics as a floating average, which ends
1240 * up weighing recent references more than old ones.
1242 * anon in [0], file in [1]
1244 if (unlikely(zone
->recent_scanned
[0] > anon
/ 4)) {
1245 spin_lock_irq(&zone
->lru_lock
);
1246 zone
->recent_scanned
[0] /= 2;
1247 zone
->recent_rotated
[0] /= 2;
1248 spin_unlock_irq(&zone
->lru_lock
);
1251 if (unlikely(zone
->recent_scanned
[1] > file
/ 4)) {
1252 spin_lock_irq(&zone
->lru_lock
);
1253 zone
->recent_scanned
[1] /= 2;
1254 zone
->recent_rotated
[1] /= 2;
1255 spin_unlock_irq(&zone
->lru_lock
);
1259 * With swappiness at 100, anonymous and file have the same priority.
1260 * This scanning priority is essentially the inverse of IO cost.
1262 anon_prio
= sc
->swappiness
;
1263 file_prio
= 200 - sc
->swappiness
;
1266 * anon recent_rotated[0]
1267 * %anon = 100 * ----------- / ----------------- * IO cost
1268 * anon + file rotate_sum
1270 ap
= (anon_prio
+ 1) * (zone
->recent_scanned
[0] + 1);
1271 ap
/= zone
->recent_rotated
[0] + 1;
1273 fp
= (file_prio
+ 1) * (zone
->recent_scanned
[1] + 1);
1274 fp
/= zone
->recent_rotated
[1] + 1;
1276 /* Normalize to percentages */
1277 percent
[0] = 100 * ap
/ (ap
+ fp
+ 1);
1278 percent
[1] = 100 - percent
[0];
1283 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1285 static unsigned long shrink_zone(int priority
, struct zone
*zone
,
1286 struct scan_control
*sc
)
1288 unsigned long nr
[NR_LRU_LISTS
];
1289 unsigned long nr_to_scan
;
1290 unsigned long nr_reclaimed
= 0;
1291 unsigned long percent
[2]; /* anon @ 0; file @ 1 */
1294 get_scan_ratio(zone
, sc
, percent
);
1297 if (scan_global_lru(sc
)) {
1298 int file
= is_file_lru(l
);
1301 * Add one to nr_to_scan just to make sure that the
1302 * kernel will slowly sift through each list.
1304 scan
= zone_page_state(zone
, NR_LRU_BASE
+ l
);
1307 scan
= (scan
* percent
[file
]) / 100;
1309 zone
->lru
[l
].nr_scan
+= scan
+ 1;
1310 nr
[l
] = zone
->lru
[l
].nr_scan
;
1311 if (nr
[l
] >= sc
->swap_cluster_max
)
1312 zone
->lru
[l
].nr_scan
= 0;
1317 * This reclaim occurs not because zone memory shortage
1318 * but because memory controller hits its limit.
1319 * Don't modify zone reclaim related data.
1321 nr
[l
] = mem_cgroup_calc_reclaim(sc
->mem_cgroup
, zone
,
1326 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1327 nr
[LRU_INACTIVE_FILE
]) {
1330 nr_to_scan
= min(nr
[l
],
1331 (unsigned long)sc
->swap_cluster_max
);
1332 nr
[l
] -= nr_to_scan
;
1334 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1335 zone
, sc
, priority
);
1341 * Even if we did not try to evict anon pages at all, we want to
1342 * rebalance the anon lru active/inactive ratio.
1344 if (!scan_global_lru(sc
) || inactive_anon_is_low(zone
))
1345 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1346 else if (!scan_global_lru(sc
))
1347 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1349 throttle_vm_writeout(sc
->gfp_mask
);
1350 return nr_reclaimed
;
1354 * This is the direct reclaim path, for page-allocating processes. We only
1355 * try to reclaim pages from zones which will satisfy the caller's allocation
1358 * We reclaim from a zone even if that zone is over pages_high. Because:
1359 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1361 * b) The zones may be over pages_high but they must go *over* pages_high to
1362 * satisfy the `incremental min' zone defense algorithm.
1364 * Returns the number of reclaimed pages.
1366 * If a zone is deemed to be full of pinned pages then just give it a light
1367 * scan then give up on it.
1369 static unsigned long shrink_zones(int priority
, struct zonelist
*zonelist
,
1370 struct scan_control
*sc
)
1372 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1373 unsigned long nr_reclaimed
= 0;
1377 sc
->all_unreclaimable
= 1;
1378 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1379 if (!populated_zone(zone
))
1382 * Take care memory controller reclaiming has small influence
1385 if (scan_global_lru(sc
)) {
1386 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1388 note_zone_scanning_priority(zone
, priority
);
1390 if (zone_is_all_unreclaimable(zone
) &&
1391 priority
!= DEF_PRIORITY
)
1392 continue; /* Let kswapd poll it */
1393 sc
->all_unreclaimable
= 0;
1396 * Ignore cpuset limitation here. We just want to reduce
1397 * # of used pages by us regardless of memory shortage.
1399 sc
->all_unreclaimable
= 0;
1400 mem_cgroup_note_reclaim_priority(sc
->mem_cgroup
,
1404 nr_reclaimed
+= shrink_zone(priority
, zone
, sc
);
1407 return nr_reclaimed
;
1411 * This is the main entry point to direct page reclaim.
1413 * If a full scan of the inactive list fails to free enough memory then we
1414 * are "out of memory" and something needs to be killed.
1416 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1417 * high - the zone may be full of dirty or under-writeback pages, which this
1418 * caller can't do much about. We kick pdflush and take explicit naps in the
1419 * hope that some of these pages can be written. But if the allocating task
1420 * holds filesystem locks which prevent writeout this might not work, and the
1421 * allocation attempt will fail.
1423 * returns: 0, if no pages reclaimed
1424 * else, the number of pages reclaimed
1426 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
1427 struct scan_control
*sc
)
1430 unsigned long ret
= 0;
1431 unsigned long total_scanned
= 0;
1432 unsigned long nr_reclaimed
= 0;
1433 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1434 unsigned long lru_pages
= 0;
1437 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1439 delayacct_freepages_start();
1441 if (scan_global_lru(sc
))
1442 count_vm_event(ALLOCSTALL
);
1444 * mem_cgroup will not do shrink_slab.
1446 if (scan_global_lru(sc
)) {
1447 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1449 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1452 lru_pages
+= zone_lru_pages(zone
);
1456 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1459 disable_swap_token();
1460 nr_reclaimed
+= shrink_zones(priority
, zonelist
, sc
);
1462 * Don't shrink slabs when reclaiming memory from
1463 * over limit cgroups
1465 if (scan_global_lru(sc
)) {
1466 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
1467 if (reclaim_state
) {
1468 nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1469 reclaim_state
->reclaimed_slab
= 0;
1472 total_scanned
+= sc
->nr_scanned
;
1473 if (nr_reclaimed
>= sc
->swap_cluster_max
) {
1479 * Try to write back as many pages as we just scanned. This
1480 * tends to cause slow streaming writers to write data to the
1481 * disk smoothly, at the dirtying rate, which is nice. But
1482 * that's undesirable in laptop mode, where we *want* lumpy
1483 * writeout. So in laptop mode, write out the whole world.
1485 if (total_scanned
> sc
->swap_cluster_max
+
1486 sc
->swap_cluster_max
/ 2) {
1487 wakeup_pdflush(laptop_mode
? 0 : total_scanned
);
1488 sc
->may_writepage
= 1;
1491 /* Take a nap, wait for some writeback to complete */
1492 if (sc
->nr_scanned
&& priority
< DEF_PRIORITY
- 2)
1493 congestion_wait(WRITE
, HZ
/10);
1495 /* top priority shrink_zones still had more to do? don't OOM, then */
1496 if (!sc
->all_unreclaimable
&& scan_global_lru(sc
))
1500 * Now that we've scanned all the zones at this priority level, note
1501 * that level within the zone so that the next thread which performs
1502 * scanning of this zone will immediately start out at this priority
1503 * level. This affects only the decision whether or not to bring
1504 * mapped pages onto the inactive list.
1509 if (scan_global_lru(sc
)) {
1510 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1512 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1515 zone
->prev_priority
= priority
;
1518 mem_cgroup_record_reclaim_priority(sc
->mem_cgroup
, priority
);
1520 delayacct_freepages_end();
1525 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
1528 struct scan_control sc
= {
1529 .gfp_mask
= gfp_mask
,
1530 .may_writepage
= !laptop_mode
,
1531 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1533 .swappiness
= vm_swappiness
,
1536 .isolate_pages
= isolate_pages_global
,
1539 return do_try_to_free_pages(zonelist
, &sc
);
1542 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1544 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
1547 struct scan_control sc
= {
1548 .may_writepage
= !laptop_mode
,
1550 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1551 .swappiness
= vm_swappiness
,
1553 .mem_cgroup
= mem_cont
,
1554 .isolate_pages
= mem_cgroup_isolate_pages
,
1556 struct zonelist
*zonelist
;
1558 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1559 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1560 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
1561 return do_try_to_free_pages(zonelist
, &sc
);
1566 * For kswapd, balance_pgdat() will work across all this node's zones until
1567 * they are all at pages_high.
1569 * Returns the number of pages which were actually freed.
1571 * There is special handling here for zones which are full of pinned pages.
1572 * This can happen if the pages are all mlocked, or if they are all used by
1573 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1574 * What we do is to detect the case where all pages in the zone have been
1575 * scanned twice and there has been zero successful reclaim. Mark the zone as
1576 * dead and from now on, only perform a short scan. Basically we're polling
1577 * the zone for when the problem goes away.
1579 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1580 * zones which have free_pages > pages_high, but once a zone is found to have
1581 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1582 * of the number of free pages in the lower zones. This interoperates with
1583 * the page allocator fallback scheme to ensure that aging of pages is balanced
1586 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
)
1591 unsigned long total_scanned
;
1592 unsigned long nr_reclaimed
;
1593 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1594 struct scan_control sc
= {
1595 .gfp_mask
= GFP_KERNEL
,
1597 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1598 .swappiness
= vm_swappiness
,
1601 .isolate_pages
= isolate_pages_global
,
1604 * temp_priority is used to remember the scanning priority at which
1605 * this zone was successfully refilled to free_pages == pages_high.
1607 int temp_priority
[MAX_NR_ZONES
];
1612 sc
.may_writepage
= !laptop_mode
;
1613 count_vm_event(PAGEOUTRUN
);
1615 for (i
= 0; i
< pgdat
->nr_zones
; i
++)
1616 temp_priority
[i
] = DEF_PRIORITY
;
1618 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1619 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
1620 unsigned long lru_pages
= 0;
1622 /* The swap token gets in the way of swapout... */
1624 disable_swap_token();
1629 * Scan in the highmem->dma direction for the highest
1630 * zone which needs scanning
1632 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
1633 struct zone
*zone
= pgdat
->node_zones
+ i
;
1635 if (!populated_zone(zone
))
1638 if (zone_is_all_unreclaimable(zone
) &&
1639 priority
!= DEF_PRIORITY
)
1643 * Do some background aging of the anon list, to give
1644 * pages a chance to be referenced before reclaiming.
1646 if (inactive_anon_is_low(zone
))
1647 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
1650 if (!zone_watermark_ok(zone
, order
, zone
->pages_high
,
1659 for (i
= 0; i
<= end_zone
; i
++) {
1660 struct zone
*zone
= pgdat
->node_zones
+ i
;
1662 lru_pages
+= zone_lru_pages(zone
);
1666 * Now scan the zone in the dma->highmem direction, stopping
1667 * at the last zone which needs scanning.
1669 * We do this because the page allocator works in the opposite
1670 * direction. This prevents the page allocator from allocating
1671 * pages behind kswapd's direction of progress, which would
1672 * cause too much scanning of the lower zones.
1674 for (i
= 0; i
<= end_zone
; i
++) {
1675 struct zone
*zone
= pgdat
->node_zones
+ i
;
1678 if (!populated_zone(zone
))
1681 if (zone_is_all_unreclaimable(zone
) &&
1682 priority
!= DEF_PRIORITY
)
1685 if (!zone_watermark_ok(zone
, order
, zone
->pages_high
,
1688 temp_priority
[i
] = priority
;
1690 note_zone_scanning_priority(zone
, priority
);
1692 * We put equal pressure on every zone, unless one
1693 * zone has way too many pages free already.
1695 if (!zone_watermark_ok(zone
, order
, 8*zone
->pages_high
,
1697 nr_reclaimed
+= shrink_zone(priority
, zone
, &sc
);
1698 reclaim_state
->reclaimed_slab
= 0;
1699 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
1701 nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1702 total_scanned
+= sc
.nr_scanned
;
1703 if (zone_is_all_unreclaimable(zone
))
1705 if (nr_slab
== 0 && zone
->pages_scanned
>=
1706 (zone_lru_pages(zone
) * 6))
1708 ZONE_ALL_UNRECLAIMABLE
);
1710 * If we've done a decent amount of scanning and
1711 * the reclaim ratio is low, start doing writepage
1712 * even in laptop mode
1714 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
1715 total_scanned
> nr_reclaimed
+ nr_reclaimed
/ 2)
1716 sc
.may_writepage
= 1;
1719 break; /* kswapd: all done */
1721 * OK, kswapd is getting into trouble. Take a nap, then take
1722 * another pass across the zones.
1724 if (total_scanned
&& priority
< DEF_PRIORITY
- 2)
1725 congestion_wait(WRITE
, HZ
/10);
1728 * We do this so kswapd doesn't build up large priorities for
1729 * example when it is freeing in parallel with allocators. It
1730 * matches the direct reclaim path behaviour in terms of impact
1731 * on zone->*_priority.
1733 if (nr_reclaimed
>= SWAP_CLUSTER_MAX
)
1738 * Note within each zone the priority level at which this zone was
1739 * brought into a happy state. So that the next thread which scans this
1740 * zone will start out at that priority level.
1742 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
1743 struct zone
*zone
= pgdat
->node_zones
+ i
;
1745 zone
->prev_priority
= temp_priority
[i
];
1747 if (!all_zones_ok
) {
1755 return nr_reclaimed
;
1759 * The background pageout daemon, started as a kernel thread
1760 * from the init process.
1762 * This basically trickles out pages so that we have _some_
1763 * free memory available even if there is no other activity
1764 * that frees anything up. This is needed for things like routing
1765 * etc, where we otherwise might have all activity going on in
1766 * asynchronous contexts that cannot page things out.
1768 * If there are applications that are active memory-allocators
1769 * (most normal use), this basically shouldn't matter.
1771 static int kswapd(void *p
)
1773 unsigned long order
;
1774 pg_data_t
*pgdat
= (pg_data_t
*)p
;
1775 struct task_struct
*tsk
= current
;
1777 struct reclaim_state reclaim_state
= {
1778 .reclaimed_slab
= 0,
1780 node_to_cpumask_ptr(cpumask
, pgdat
->node_id
);
1782 if (!cpus_empty(*cpumask
))
1783 set_cpus_allowed_ptr(tsk
, cpumask
);
1784 current
->reclaim_state
= &reclaim_state
;
1787 * Tell the memory management that we're a "memory allocator",
1788 * and that if we need more memory we should get access to it
1789 * regardless (see "__alloc_pages()"). "kswapd" should
1790 * never get caught in the normal page freeing logic.
1792 * (Kswapd normally doesn't need memory anyway, but sometimes
1793 * you need a small amount of memory in order to be able to
1794 * page out something else, and this flag essentially protects
1795 * us from recursively trying to free more memory as we're
1796 * trying to free the first piece of memory in the first place).
1798 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
1803 unsigned long new_order
;
1805 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
1806 new_order
= pgdat
->kswapd_max_order
;
1807 pgdat
->kswapd_max_order
= 0;
1808 if (order
< new_order
) {
1810 * Don't sleep if someone wants a larger 'order'
1815 if (!freezing(current
))
1818 order
= pgdat
->kswapd_max_order
;
1820 finish_wait(&pgdat
->kswapd_wait
, &wait
);
1822 if (!try_to_freeze()) {
1823 /* We can speed up thawing tasks if we don't call
1824 * balance_pgdat after returning from the refrigerator
1826 balance_pgdat(pgdat
, order
);
1833 * A zone is low on free memory, so wake its kswapd task to service it.
1835 void wakeup_kswapd(struct zone
*zone
, int order
)
1839 if (!populated_zone(zone
))
1842 pgdat
= zone
->zone_pgdat
;
1843 if (zone_watermark_ok(zone
, order
, zone
->pages_low
, 0, 0))
1845 if (pgdat
->kswapd_max_order
< order
)
1846 pgdat
->kswapd_max_order
= order
;
1847 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1849 if (!waitqueue_active(&pgdat
->kswapd_wait
))
1851 wake_up_interruptible(&pgdat
->kswapd_wait
);
1854 unsigned long global_lru_pages(void)
1856 return global_page_state(NR_ACTIVE_ANON
)
1857 + global_page_state(NR_ACTIVE_FILE
)
1858 + global_page_state(NR_INACTIVE_ANON
)
1859 + global_page_state(NR_INACTIVE_FILE
);
1864 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1865 * from LRU lists system-wide, for given pass and priority, and returns the
1866 * number of reclaimed pages
1868 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1870 static unsigned long shrink_all_zones(unsigned long nr_pages
, int prio
,
1871 int pass
, struct scan_control
*sc
)
1874 unsigned long nr_to_scan
, ret
= 0;
1877 for_each_zone(zone
) {
1879 if (!populated_zone(zone
))
1882 if (zone_is_all_unreclaimable(zone
) && prio
!= DEF_PRIORITY
)
1886 /* For pass = 0 we don't shrink the active list */
1888 (l
== LRU_ACTIVE
|| l
== LRU_ACTIVE_FILE
))
1891 zone
->lru
[l
].nr_scan
+=
1892 (zone_page_state(zone
, NR_LRU_BASE
+ l
)
1894 if (zone
->lru
[l
].nr_scan
>= nr_pages
|| pass
> 3) {
1895 zone
->lru
[l
].nr_scan
= 0;
1896 nr_to_scan
= min(nr_pages
,
1897 zone_page_state(zone
,
1899 ret
+= shrink_list(l
, nr_to_scan
, zone
,
1901 if (ret
>= nr_pages
)
1911 * Try to free `nr_pages' of memory, system-wide, and return the number of
1914 * Rather than trying to age LRUs the aim is to preserve the overall
1915 * LRU order by reclaiming preferentially
1916 * inactive > active > active referenced > active mapped
1918 unsigned long shrink_all_memory(unsigned long nr_pages
)
1920 unsigned long lru_pages
, nr_slab
;
1921 unsigned long ret
= 0;
1923 struct reclaim_state reclaim_state
;
1924 struct scan_control sc
= {
1925 .gfp_mask
= GFP_KERNEL
,
1927 .swap_cluster_max
= nr_pages
,
1929 .swappiness
= vm_swappiness
,
1930 .isolate_pages
= isolate_pages_global
,
1933 current
->reclaim_state
= &reclaim_state
;
1935 lru_pages
= global_lru_pages();
1936 nr_slab
= global_page_state(NR_SLAB_RECLAIMABLE
);
1937 /* If slab caches are huge, it's better to hit them first */
1938 while (nr_slab
>= lru_pages
) {
1939 reclaim_state
.reclaimed_slab
= 0;
1940 shrink_slab(nr_pages
, sc
.gfp_mask
, lru_pages
);
1941 if (!reclaim_state
.reclaimed_slab
)
1944 ret
+= reclaim_state
.reclaimed_slab
;
1945 if (ret
>= nr_pages
)
1948 nr_slab
-= reclaim_state
.reclaimed_slab
;
1952 * We try to shrink LRUs in 5 passes:
1953 * 0 = Reclaim from inactive_list only
1954 * 1 = Reclaim from active list but don't reclaim mapped
1955 * 2 = 2nd pass of type 1
1956 * 3 = Reclaim mapped (normal reclaim)
1957 * 4 = 2nd pass of type 3
1959 for (pass
= 0; pass
< 5; pass
++) {
1962 /* Force reclaiming mapped pages in the passes #3 and #4 */
1965 sc
.swappiness
= 100;
1968 for (prio
= DEF_PRIORITY
; prio
>= 0; prio
--) {
1969 unsigned long nr_to_scan
= nr_pages
- ret
;
1972 ret
+= shrink_all_zones(nr_to_scan
, prio
, pass
, &sc
);
1973 if (ret
>= nr_pages
)
1976 reclaim_state
.reclaimed_slab
= 0;
1977 shrink_slab(sc
.nr_scanned
, sc
.gfp_mask
,
1978 global_lru_pages());
1979 ret
+= reclaim_state
.reclaimed_slab
;
1980 if (ret
>= nr_pages
)
1983 if (sc
.nr_scanned
&& prio
< DEF_PRIORITY
- 2)
1984 congestion_wait(WRITE
, HZ
/ 10);
1989 * If ret = 0, we could not shrink LRUs, but there may be something
1994 reclaim_state
.reclaimed_slab
= 0;
1995 shrink_slab(nr_pages
, sc
.gfp_mask
, global_lru_pages());
1996 ret
+= reclaim_state
.reclaimed_slab
;
1997 } while (ret
< nr_pages
&& reclaim_state
.reclaimed_slab
> 0);
2001 current
->reclaim_state
= NULL
;
2007 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2008 not required for correctness. So if the last cpu in a node goes
2009 away, we get changed to run anywhere: as the first one comes back,
2010 restore their cpu bindings. */
2011 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2012 unsigned long action
, void *hcpu
)
2016 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2017 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2018 pg_data_t
*pgdat
= NODE_DATA(nid
);
2019 node_to_cpumask_ptr(mask
, pgdat
->node_id
);
2021 if (any_online_cpu(*mask
) < nr_cpu_ids
)
2022 /* One of our CPUs online: restore mask */
2023 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2030 * This kswapd start function will be called by init and node-hot-add.
2031 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2033 int kswapd_run(int nid
)
2035 pg_data_t
*pgdat
= NODE_DATA(nid
);
2041 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2042 if (IS_ERR(pgdat
->kswapd
)) {
2043 /* failure at boot is fatal */
2044 BUG_ON(system_state
== SYSTEM_BOOTING
);
2045 printk("Failed to start kswapd on node %d\n",nid
);
2051 static int __init
kswapd_init(void)
2056 for_each_node_state(nid
, N_HIGH_MEMORY
)
2058 hotcpu_notifier(cpu_callback
, 0);
2062 module_init(kswapd_init
)
2068 * If non-zero call zone_reclaim when the number of free pages falls below
2071 int zone_reclaim_mode __read_mostly
;
2073 #define RECLAIM_OFF 0
2074 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2075 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2076 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2079 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2080 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2083 #define ZONE_RECLAIM_PRIORITY 4
2086 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2089 int sysctl_min_unmapped_ratio
= 1;
2092 * If the number of slab pages in a zone grows beyond this percentage then
2093 * slab reclaim needs to occur.
2095 int sysctl_min_slab_ratio
= 5;
2098 * Try to free up some pages from this zone through reclaim.
2100 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2102 /* Minimum pages needed in order to stay on node */
2103 const unsigned long nr_pages
= 1 << order
;
2104 struct task_struct
*p
= current
;
2105 struct reclaim_state reclaim_state
;
2107 unsigned long nr_reclaimed
= 0;
2108 struct scan_control sc
= {
2109 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2110 .may_swap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2111 .swap_cluster_max
= max_t(unsigned long, nr_pages
,
2113 .gfp_mask
= gfp_mask
,
2114 .swappiness
= vm_swappiness
,
2115 .isolate_pages
= isolate_pages_global
,
2117 unsigned long slab_reclaimable
;
2119 disable_swap_token();
2122 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2123 * and we also need to be able to write out pages for RECLAIM_WRITE
2126 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2127 reclaim_state
.reclaimed_slab
= 0;
2128 p
->reclaim_state
= &reclaim_state
;
2130 if (zone_page_state(zone
, NR_FILE_PAGES
) -
2131 zone_page_state(zone
, NR_FILE_MAPPED
) >
2132 zone
->min_unmapped_pages
) {
2134 * Free memory by calling shrink zone with increasing
2135 * priorities until we have enough memory freed.
2137 priority
= ZONE_RECLAIM_PRIORITY
;
2139 note_zone_scanning_priority(zone
, priority
);
2140 nr_reclaimed
+= shrink_zone(priority
, zone
, &sc
);
2142 } while (priority
>= 0 && nr_reclaimed
< nr_pages
);
2145 slab_reclaimable
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2146 if (slab_reclaimable
> zone
->min_slab_pages
) {
2148 * shrink_slab() does not currently allow us to determine how
2149 * many pages were freed in this zone. So we take the current
2150 * number of slab pages and shake the slab until it is reduced
2151 * by the same nr_pages that we used for reclaiming unmapped
2154 * Note that shrink_slab will free memory on all zones and may
2157 while (shrink_slab(sc
.nr_scanned
, gfp_mask
, order
) &&
2158 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) >
2159 slab_reclaimable
- nr_pages
)
2163 * Update nr_reclaimed by the number of slab pages we
2164 * reclaimed from this zone.
2166 nr_reclaimed
+= slab_reclaimable
-
2167 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2170 p
->reclaim_state
= NULL
;
2171 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
2172 return nr_reclaimed
>= nr_pages
;
2175 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2181 * Zone reclaim reclaims unmapped file backed pages and
2182 * slab pages if we are over the defined limits.
2184 * A small portion of unmapped file backed pages is needed for
2185 * file I/O otherwise pages read by file I/O will be immediately
2186 * thrown out if the zone is overallocated. So we do not reclaim
2187 * if less than a specified percentage of the zone is used by
2188 * unmapped file backed pages.
2190 if (zone_page_state(zone
, NR_FILE_PAGES
) -
2191 zone_page_state(zone
, NR_FILE_MAPPED
) <= zone
->min_unmapped_pages
2192 && zone_page_state(zone
, NR_SLAB_RECLAIMABLE
)
2193 <= zone
->min_slab_pages
)
2196 if (zone_is_all_unreclaimable(zone
))
2200 * Do not scan if the allocation should not be delayed.
2202 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
2206 * Only run zone reclaim on the local zone or on zones that do not
2207 * have associated processors. This will favor the local processor
2208 * over remote processors and spread off node memory allocations
2209 * as wide as possible.
2211 node_id
= zone_to_nid(zone
);
2212 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
2215 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
2217 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
2218 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);