4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie.
7 * kswapd added: 7.1.96 sct
8 * Removed kswapd_ctl limits, and swap out as many pages as needed
9 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
10 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
11 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/swap.h>
19 #include <linux/pagemap.h>
20 #include <linux/init.h>
21 #include <linux/highmem.h>
22 #include <linux/vmstat.h>
23 #include <linux/file.h>
24 #include <linux/writeback.h>
25 #include <linux/blkdev.h>
26 #include <linux/buffer_head.h> /* for try_to_release_page(),
27 buffer_heads_over_limit */
28 #include <linux/mm_inline.h>
29 #include <linux/pagevec.h>
30 #include <linux/backing-dev.h>
31 #include <linux/rmap.h>
32 #include <linux/topology.h>
33 #include <linux/cpu.h>
34 #include <linux/cpuset.h>
35 #include <linux/notifier.h>
36 #include <linux/rwsem.h>
37 #include <linux/delay.h>
38 #include <linux/kthread.h>
39 #include <linux/freezer.h>
40 #include <linux/memcontrol.h>
41 #include <linux/delayacct.h>
42 #include <linux/sysctl.h>
44 #include <asm/tlbflush.h>
45 #include <asm/div64.h>
47 #include <linux/swapops.h>
52 /* Incremented by the number of inactive pages that were scanned */
53 unsigned long nr_scanned
;
55 /* This context's GFP mask */
60 /* Can pages be swapped as part of reclaim? */
63 /* This context's SWAP_CLUSTER_MAX. If freeing memory for
64 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
65 * In this context, it doesn't matter that we scan the
66 * whole list at once. */
71 int all_unreclaimable
;
75 /* Which cgroup do we reclaim from */
76 struct mem_cgroup
*mem_cgroup
;
78 /* Pluggable isolate pages callback */
79 unsigned long (*isolate_pages
)(unsigned long nr
, struct list_head
*dst
,
80 unsigned long *scanned
, int order
, int mode
,
81 struct zone
*z
, struct mem_cgroup
*mem_cont
,
82 int active
, int file
);
85 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
87 #ifdef ARCH_HAS_PREFETCH
88 #define prefetch_prev_lru_page(_page, _base, _field) \
90 if ((_page)->lru.prev != _base) { \
93 prev = lru_to_page(&(_page->lru)); \
94 prefetch(&prev->_field); \
98 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
101 #ifdef ARCH_HAS_PREFETCHW
102 #define prefetchw_prev_lru_page(_page, _base, _field) \
104 if ((_page)->lru.prev != _base) { \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetchw(&prev->_field); \
112 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
116 * From 0 .. 100. Higher means more swappy.
118 int vm_swappiness
= 60;
119 long vm_total_pages
; /* The total number of pages which the VM controls */
121 static LIST_HEAD(shrinker_list
);
122 static DECLARE_RWSEM(shrinker_rwsem
);
124 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
125 #define scan_global_lru(sc) (!(sc)->mem_cgroup)
127 #define scan_global_lru(sc) (1)
131 * Add a shrinker callback to be called from the vm
133 void register_shrinker(struct shrinker
*shrinker
)
136 down_write(&shrinker_rwsem
);
137 list_add_tail(&shrinker
->list
, &shrinker_list
);
138 up_write(&shrinker_rwsem
);
140 EXPORT_SYMBOL(register_shrinker
);
145 void unregister_shrinker(struct shrinker
*shrinker
)
147 down_write(&shrinker_rwsem
);
148 list_del(&shrinker
->list
);
149 up_write(&shrinker_rwsem
);
151 EXPORT_SYMBOL(unregister_shrinker
);
153 #define SHRINK_BATCH 128
155 * Call the shrink functions to age shrinkable caches
157 * Here we assume it costs one seek to replace a lru page and that it also
158 * takes a seek to recreate a cache object. With this in mind we age equal
159 * percentages of the lru and ageable caches. This should balance the seeks
160 * generated by these structures.
162 * If the vm encountered mapped pages on the LRU it increase the pressure on
163 * slab to avoid swapping.
165 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
167 * `lru_pages' represents the number of on-LRU pages in all the zones which
168 * are eligible for the caller's allocation attempt. It is used for balancing
169 * slab reclaim versus page reclaim.
171 * Returns the number of slab objects which we shrunk.
173 unsigned long shrink_slab(unsigned long scanned
, gfp_t gfp_mask
,
174 unsigned long lru_pages
)
176 struct shrinker
*shrinker
;
177 unsigned long ret
= 0;
180 scanned
= SWAP_CLUSTER_MAX
;
182 if (!down_read_trylock(&shrinker_rwsem
))
183 return 1; /* Assume we'll be able to shrink next time */
185 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
186 unsigned long long delta
;
187 unsigned long total_scan
;
188 unsigned long max_pass
= (*shrinker
->shrink
)(0, gfp_mask
);
190 delta
= (4 * scanned
) / shrinker
->seeks
;
192 do_div(delta
, lru_pages
+ 1);
193 shrinker
->nr
+= delta
;
194 if (shrinker
->nr
< 0) {
195 printk(KERN_ERR
"%s: nr=%ld\n",
196 __func__
, shrinker
->nr
);
197 shrinker
->nr
= max_pass
;
201 * Avoid risking looping forever due to too large nr value:
202 * never try to free more than twice the estimate number of
205 if (shrinker
->nr
> max_pass
* 2)
206 shrinker
->nr
= max_pass
* 2;
208 total_scan
= shrinker
->nr
;
211 while (total_scan
>= SHRINK_BATCH
) {
212 long this_scan
= SHRINK_BATCH
;
216 nr_before
= (*shrinker
->shrink
)(0, gfp_mask
);
217 shrink_ret
= (*shrinker
->shrink
)(this_scan
, gfp_mask
);
218 if (shrink_ret
== -1)
220 if (shrink_ret
< nr_before
)
221 ret
+= nr_before
- shrink_ret
;
222 count_vm_events(SLABS_SCANNED
, this_scan
);
223 total_scan
-= this_scan
;
228 shrinker
->nr
+= total_scan
;
230 up_read(&shrinker_rwsem
);
234 /* Called without lock on whether page is mapped, so answer is unstable */
235 static inline int page_mapping_inuse(struct page
*page
)
237 struct address_space
*mapping
;
239 /* Page is in somebody's page tables. */
240 if (page_mapped(page
))
243 /* Be more reluctant to reclaim swapcache than pagecache */
244 if (PageSwapCache(page
))
247 mapping
= page_mapping(page
);
251 /* File is mmap'd by somebody? */
252 return mapping_mapped(mapping
);
255 static inline int is_page_cache_freeable(struct page
*page
)
257 return page_count(page
) - !!PagePrivate(page
) == 2;
260 static int may_write_to_queue(struct backing_dev_info
*bdi
)
262 if (current
->flags
& PF_SWAPWRITE
)
264 if (!bdi_write_congested(bdi
))
266 if (bdi
== current
->backing_dev_info
)
272 * We detected a synchronous write error writing a page out. Probably
273 * -ENOSPC. We need to propagate that into the address_space for a subsequent
274 * fsync(), msync() or close().
276 * The tricky part is that after writepage we cannot touch the mapping: nothing
277 * prevents it from being freed up. But we have a ref on the page and once
278 * that page is locked, the mapping is pinned.
280 * We're allowed to run sleeping lock_page() here because we know the caller has
283 static void handle_write_error(struct address_space
*mapping
,
284 struct page
*page
, int error
)
287 if (page_mapping(page
) == mapping
)
288 mapping_set_error(mapping
, error
);
292 /* Request for sync pageout. */
298 /* possible outcome of pageout() */
300 /* failed to write page out, page is locked */
302 /* move page to the active list, page is locked */
304 /* page has been sent to the disk successfully, page is unlocked */
306 /* page is clean and locked */
311 * pageout is called by shrink_page_list() for each dirty page.
312 * Calls ->writepage().
314 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
315 enum pageout_io sync_writeback
)
318 * If the page is dirty, only perform writeback if that write
319 * will be non-blocking. To prevent this allocation from being
320 * stalled by pagecache activity. But note that there may be
321 * stalls if we need to run get_block(). We could test
322 * PagePrivate for that.
324 * If this process is currently in generic_file_write() against
325 * this page's queue, we can perform writeback even if that
328 * If the page is swapcache, write it back even if that would
329 * block, for some throttling. This happens by accident, because
330 * swap_backing_dev_info is bust: it doesn't reflect the
331 * congestion state of the swapdevs. Easy to fix, if needed.
332 * See swapfile.c:page_queue_congested().
334 if (!is_page_cache_freeable(page
))
338 * Some data journaling orphaned pages can have
339 * page->mapping == NULL while being dirty with clean buffers.
341 if (PagePrivate(page
)) {
342 if (try_to_free_buffers(page
)) {
343 ClearPageDirty(page
);
344 printk("%s: orphaned page\n", __func__
);
350 if (mapping
->a_ops
->writepage
== NULL
)
351 return PAGE_ACTIVATE
;
352 if (!may_write_to_queue(mapping
->backing_dev_info
))
355 if (clear_page_dirty_for_io(page
)) {
357 struct writeback_control wbc
= {
358 .sync_mode
= WB_SYNC_NONE
,
359 .nr_to_write
= SWAP_CLUSTER_MAX
,
361 .range_end
= LLONG_MAX
,
366 SetPageReclaim(page
);
367 res
= mapping
->a_ops
->writepage(page
, &wbc
);
369 handle_write_error(mapping
, page
, res
);
370 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
371 ClearPageReclaim(page
);
372 return PAGE_ACTIVATE
;
376 * Wait on writeback if requested to. This happens when
377 * direct reclaiming a large contiguous area and the
378 * first attempt to free a range of pages fails.
380 if (PageWriteback(page
) && sync_writeback
== PAGEOUT_IO_SYNC
)
381 wait_on_page_writeback(page
);
383 if (!PageWriteback(page
)) {
384 /* synchronous write or broken a_ops? */
385 ClearPageReclaim(page
);
387 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
395 * Same as remove_mapping, but if the page is removed from the mapping, it
396 * gets returned with a refcount of 0.
398 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
400 BUG_ON(!PageLocked(page
));
401 BUG_ON(mapping
!= page_mapping(page
));
403 spin_lock_irq(&mapping
->tree_lock
);
405 * The non racy check for a busy page.
407 * Must be careful with the order of the tests. When someone has
408 * a ref to the page, it may be possible that they dirty it then
409 * drop the reference. So if PageDirty is tested before page_count
410 * here, then the following race may occur:
412 * get_user_pages(&page);
413 * [user mapping goes away]
415 * !PageDirty(page) [good]
416 * SetPageDirty(page);
418 * !page_count(page) [good, discard it]
420 * [oops, our write_to data is lost]
422 * Reversing the order of the tests ensures such a situation cannot
423 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
424 * load is not satisfied before that of page->_count.
426 * Note that if SetPageDirty is always performed via set_page_dirty,
427 * and thus under tree_lock, then this ordering is not required.
429 if (!page_freeze_refs(page
, 2))
431 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
432 if (unlikely(PageDirty(page
))) {
433 page_unfreeze_refs(page
, 2);
437 if (PageSwapCache(page
)) {
438 swp_entry_t swap
= { .val
= page_private(page
) };
439 __delete_from_swap_cache(page
);
440 spin_unlock_irq(&mapping
->tree_lock
);
443 __remove_from_page_cache(page
);
444 spin_unlock_irq(&mapping
->tree_lock
);
450 spin_unlock_irq(&mapping
->tree_lock
);
455 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
456 * someone else has a ref on the page, abort and return 0. If it was
457 * successfully detached, return 1. Assumes the caller has a single ref on
460 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
462 if (__remove_mapping(mapping
, page
)) {
464 * Unfreezing the refcount with 1 rather than 2 effectively
465 * drops the pagecache ref for us without requiring another
468 page_unfreeze_refs(page
, 1);
475 * putback_lru_page - put previously isolated page onto appropriate LRU list
476 * @page: page to be put back to appropriate lru list
478 * Add previously isolated @page to appropriate LRU list.
479 * Page may still be unevictable for other reasons.
481 * lru_lock must not be held, interrupts must be enabled.
483 #ifdef CONFIG_UNEVICTABLE_LRU
484 void putback_lru_page(struct page
*page
)
487 int active
= !!TestClearPageActive(page
);
488 int was_unevictable
= PageUnevictable(page
);
490 VM_BUG_ON(PageLRU(page
));
493 ClearPageUnevictable(page
);
495 if (page_evictable(page
, NULL
)) {
497 * For evictable pages, we can use the cache.
498 * In event of a race, worst case is we end up with an
499 * unevictable page on [in]active list.
500 * We know how to handle that.
502 lru
= active
+ page_is_file_cache(page
);
503 lru_cache_add_lru(page
, lru
);
506 * Put unevictable pages directly on zone's unevictable
509 lru
= LRU_UNEVICTABLE
;
510 add_page_to_unevictable_list(page
);
512 mem_cgroup_move_lists(page
, lru
);
515 * page's status can change while we move it among lru. If an evictable
516 * page is on unevictable list, it never be freed. To avoid that,
517 * check after we added it to the list, again.
519 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
520 if (!isolate_lru_page(page
)) {
524 /* This means someone else dropped this page from LRU
525 * So, it will be freed or putback to LRU again. There is
526 * nothing to do here.
530 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
531 count_vm_event(UNEVICTABLE_PGRESCUED
);
532 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
533 count_vm_event(UNEVICTABLE_PGCULLED
);
535 put_page(page
); /* drop ref from isolate */
538 #else /* CONFIG_UNEVICTABLE_LRU */
540 void putback_lru_page(struct page
*page
)
543 VM_BUG_ON(PageLRU(page
));
545 lru
= !!TestClearPageActive(page
) + page_is_file_cache(page
);
546 lru_cache_add_lru(page
, lru
);
547 mem_cgroup_move_lists(page
, lru
);
550 #endif /* CONFIG_UNEVICTABLE_LRU */
554 * shrink_page_list() returns the number of reclaimed pages
556 static unsigned long shrink_page_list(struct list_head
*page_list
,
557 struct scan_control
*sc
,
558 enum pageout_io sync_writeback
)
560 LIST_HEAD(ret_pages
);
561 struct pagevec freed_pvec
;
563 unsigned long nr_reclaimed
= 0;
567 pagevec_init(&freed_pvec
, 1);
568 while (!list_empty(page_list
)) {
569 struct address_space
*mapping
;
576 page
= lru_to_page(page_list
);
577 list_del(&page
->lru
);
579 if (!trylock_page(page
))
582 VM_BUG_ON(PageActive(page
));
586 if (unlikely(!page_evictable(page
, NULL
)))
589 if (!sc
->may_swap
&& page_mapped(page
))
592 /* Double the slab pressure for mapped and swapcache pages */
593 if (page_mapped(page
) || PageSwapCache(page
))
596 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
597 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
599 if (PageWriteback(page
)) {
601 * Synchronous reclaim is performed in two passes,
602 * first an asynchronous pass over the list to
603 * start parallel writeback, and a second synchronous
604 * pass to wait for the IO to complete. Wait here
605 * for any page for which writeback has already
608 if (sync_writeback
== PAGEOUT_IO_SYNC
&& may_enter_fs
)
609 wait_on_page_writeback(page
);
614 referenced
= page_referenced(page
, 1, sc
->mem_cgroup
);
615 /* In active use or really unfreeable? Activate it. */
616 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&&
617 referenced
&& page_mapping_inuse(page
))
618 goto activate_locked
;
621 * Anonymous process memory has backing store?
622 * Try to allocate it some swap space here.
624 if (PageAnon(page
) && !PageSwapCache(page
)) {
625 if (!(sc
->gfp_mask
& __GFP_IO
))
627 if (!add_to_swap(page
))
628 goto activate_locked
;
632 mapping
= page_mapping(page
);
635 * The page is mapped into the page tables of one or more
636 * processes. Try to unmap it here.
638 if (page_mapped(page
) && mapping
) {
639 switch (try_to_unmap(page
, 0)) {
641 goto activate_locked
;
647 ; /* try to free the page below */
651 if (PageDirty(page
)) {
652 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
&& referenced
)
656 if (!sc
->may_writepage
)
659 /* Page is dirty, try to write it out here */
660 switch (pageout(page
, mapping
, sync_writeback
)) {
664 goto activate_locked
;
666 if (PageWriteback(page
) || PageDirty(page
))
669 * A synchronous write - probably a ramdisk. Go
670 * ahead and try to reclaim the page.
672 if (!trylock_page(page
))
674 if (PageDirty(page
) || PageWriteback(page
))
676 mapping
= page_mapping(page
);
678 ; /* try to free the page below */
683 * If the page has buffers, try to free the buffer mappings
684 * associated with this page. If we succeed we try to free
687 * We do this even if the page is PageDirty().
688 * try_to_release_page() does not perform I/O, but it is
689 * possible for a page to have PageDirty set, but it is actually
690 * clean (all its buffers are clean). This happens if the
691 * buffers were written out directly, with submit_bh(). ext3
692 * will do this, as well as the blockdev mapping.
693 * try_to_release_page() will discover that cleanness and will
694 * drop the buffers and mark the page clean - it can be freed.
696 * Rarely, pages can have buffers and no ->mapping. These are
697 * the pages which were not successfully invalidated in
698 * truncate_complete_page(). We try to drop those buffers here
699 * and if that worked, and the page is no longer mapped into
700 * process address space (page_count == 1) it can be freed.
701 * Otherwise, leave the page on the LRU so it is swappable.
703 if (PagePrivate(page
)) {
704 if (!try_to_release_page(page
, sc
->gfp_mask
))
705 goto activate_locked
;
706 if (!mapping
&& page_count(page
) == 1) {
708 if (put_page_testzero(page
))
712 * rare race with speculative reference.
713 * the speculative reference will free
714 * this page shortly, so we may
715 * increment nr_reclaimed here (and
716 * leave it off the LRU).
724 if (!mapping
|| !__remove_mapping(mapping
, page
))
728 * At this point, we have no other references and there is
729 * no way to pick any more up (removed from LRU, removed
730 * from pagecache). Can use non-atomic bitops now (and
731 * we obviously don't have to worry about waking up a process
732 * waiting on the page lock, because there are no references.
734 __clear_page_locked(page
);
737 if (!pagevec_add(&freed_pvec
, page
)) {
738 __pagevec_free(&freed_pvec
);
739 pagevec_reinit(&freed_pvec
);
744 if (PageSwapCache(page
))
745 try_to_free_swap(page
);
747 putback_lru_page(page
);
751 /* Not a candidate for swapping, so reclaim swap space. */
752 if (PageSwapCache(page
) && vm_swap_full())
753 try_to_free_swap(page
);
754 VM_BUG_ON(PageActive(page
));
760 list_add(&page
->lru
, &ret_pages
);
761 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
763 list_splice(&ret_pages
, page_list
);
764 if (pagevec_count(&freed_pvec
))
765 __pagevec_free(&freed_pvec
);
766 count_vm_events(PGACTIVATE
, pgactivate
);
770 /* LRU Isolation modes. */
771 #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */
772 #define ISOLATE_ACTIVE 1 /* Isolate active pages. */
773 #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */
776 * Attempt to remove the specified page from its LRU. Only take this page
777 * if it is of the appropriate PageActive status. Pages which are being
778 * freed elsewhere are also ignored.
780 * page: page to consider
781 * mode: one of the LRU isolation modes defined above
783 * returns 0 on success, -ve errno on failure.
785 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
789 /* Only take pages on the LRU. */
794 * When checking the active state, we need to be sure we are
795 * dealing with comparible boolean values. Take the logical not
798 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
801 if (mode
!= ISOLATE_BOTH
&& (!page_is_file_cache(page
) != !file
))
805 * When this function is being called for lumpy reclaim, we
806 * initially look into all LRU pages, active, inactive and
807 * unevictable; only give shrink_page_list evictable pages.
809 if (PageUnevictable(page
))
813 if (likely(get_page_unless_zero(page
))) {
815 * Be careful not to clear PageLRU until after we're
816 * sure the page is not being freed elsewhere -- the
817 * page release code relies on it.
827 * zone->lru_lock is heavily contended. Some of the functions that
828 * shrink the lists perform better by taking out a batch of pages
829 * and working on them outside the LRU lock.
831 * For pagecache intensive workloads, this function is the hottest
832 * spot in the kernel (apart from copy_*_user functions).
834 * Appropriate locks must be held before calling this function.
836 * @nr_to_scan: The number of pages to look through on the list.
837 * @src: The LRU list to pull pages off.
838 * @dst: The temp list to put pages on to.
839 * @scanned: The number of pages that were scanned.
840 * @order: The caller's attempted allocation order
841 * @mode: One of the LRU isolation modes
842 * @file: True [1] if isolating file [!anon] pages
844 * returns how many pages were moved onto *@dst.
846 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
847 struct list_head
*src
, struct list_head
*dst
,
848 unsigned long *scanned
, int order
, int mode
, int file
)
850 unsigned long nr_taken
= 0;
853 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
856 unsigned long end_pfn
;
857 unsigned long page_pfn
;
860 page
= lru_to_page(src
);
861 prefetchw_prev_lru_page(page
, src
, flags
);
863 VM_BUG_ON(!PageLRU(page
));
865 switch (__isolate_lru_page(page
, mode
, file
)) {
867 list_move(&page
->lru
, dst
);
872 /* else it is being freed elsewhere */
873 list_move(&page
->lru
, src
);
884 * Attempt to take all pages in the order aligned region
885 * surrounding the tag page. Only take those pages of
886 * the same active state as that tag page. We may safely
887 * round the target page pfn down to the requested order
888 * as the mem_map is guarenteed valid out to MAX_ORDER,
889 * where that page is in a different zone we will detect
890 * it from its zone id and abort this block scan.
892 zone_id
= page_zone_id(page
);
893 page_pfn
= page_to_pfn(page
);
894 pfn
= page_pfn
& ~((1 << order
) - 1);
895 end_pfn
= pfn
+ (1 << order
);
896 for (; pfn
< end_pfn
; pfn
++) {
897 struct page
*cursor_page
;
899 /* The target page is in the block, ignore it. */
900 if (unlikely(pfn
== page_pfn
))
903 /* Avoid holes within the zone. */
904 if (unlikely(!pfn_valid_within(pfn
)))
907 cursor_page
= pfn_to_page(pfn
);
909 /* Check that we have not crossed a zone boundary. */
910 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
912 switch (__isolate_lru_page(cursor_page
, mode
, file
)) {
914 list_move(&cursor_page
->lru
, dst
);
920 /* else it is being freed elsewhere */
921 list_move(&cursor_page
->lru
, src
);
923 break; /* ! on LRU or wrong list */
932 static unsigned long isolate_pages_global(unsigned long nr
,
933 struct list_head
*dst
,
934 unsigned long *scanned
, int order
,
935 int mode
, struct zone
*z
,
936 struct mem_cgroup
*mem_cont
,
937 int active
, int file
)
944 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
949 * clear_active_flags() is a helper for shrink_active_list(), clearing
950 * any active bits from the pages in the list.
952 static unsigned long clear_active_flags(struct list_head
*page_list
,
959 list_for_each_entry(page
, page_list
, lru
) {
960 lru
= page_is_file_cache(page
);
961 if (PageActive(page
)) {
963 ClearPageActive(page
);
973 * isolate_lru_page - tries to isolate a page from its LRU list
974 * @page: page to isolate from its LRU list
976 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
977 * vmstat statistic corresponding to whatever LRU list the page was on.
979 * Returns 0 if the page was removed from an LRU list.
980 * Returns -EBUSY if the page was not on an LRU list.
982 * The returned page will have PageLRU() cleared. If it was found on
983 * the active list, it will have PageActive set. If it was found on
984 * the unevictable list, it will have the PageUnevictable bit set. That flag
985 * may need to be cleared by the caller before letting the page go.
987 * The vmstat statistic corresponding to the list on which the page was
988 * found will be decremented.
991 * (1) Must be called with an elevated refcount on the page. This is a
992 * fundamentnal difference from isolate_lru_pages (which is called
993 * without a stable reference).
994 * (2) the lru_lock must not be held.
995 * (3) interrupts must be enabled.
997 int isolate_lru_page(struct page
*page
)
1001 if (PageLRU(page
)) {
1002 struct zone
*zone
= page_zone(page
);
1004 spin_lock_irq(&zone
->lru_lock
);
1005 if (PageLRU(page
) && get_page_unless_zero(page
)) {
1006 int lru
= page_lru(page
);
1010 del_page_from_lru_list(zone
, page
, lru
);
1012 spin_unlock_irq(&zone
->lru_lock
);
1018 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1019 * of reclaimed pages
1021 static unsigned long shrink_inactive_list(unsigned long max_scan
,
1022 struct zone
*zone
, struct scan_control
*sc
,
1023 int priority
, int file
)
1025 LIST_HEAD(page_list
);
1026 struct pagevec pvec
;
1027 unsigned long nr_scanned
= 0;
1028 unsigned long nr_reclaimed
= 0;
1030 pagevec_init(&pvec
, 1);
1033 spin_lock_irq(&zone
->lru_lock
);
1036 unsigned long nr_taken
;
1037 unsigned long nr_scan
;
1038 unsigned long nr_freed
;
1039 unsigned long nr_active
;
1040 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1041 int mode
= ISOLATE_INACTIVE
;
1044 * If we need a large contiguous chunk of memory, or have
1045 * trouble getting a small set of contiguous pages, we
1046 * will reclaim both active and inactive pages.
1048 * We use the same threshold as pageout congestion_wait below.
1050 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1051 mode
= ISOLATE_BOTH
;
1052 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
1053 mode
= ISOLATE_BOTH
;
1055 nr_taken
= sc
->isolate_pages(sc
->swap_cluster_max
,
1056 &page_list
, &nr_scan
, sc
->order
, mode
,
1057 zone
, sc
->mem_cgroup
, 0, file
);
1058 nr_active
= clear_active_flags(&page_list
, count
);
1059 __count_vm_events(PGDEACTIVATE
, nr_active
);
1061 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1062 -count
[LRU_ACTIVE_FILE
]);
1063 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1064 -count
[LRU_INACTIVE_FILE
]);
1065 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1066 -count
[LRU_ACTIVE_ANON
]);
1067 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1068 -count
[LRU_INACTIVE_ANON
]);
1070 if (scan_global_lru(sc
)) {
1071 zone
->pages_scanned
+= nr_scan
;
1072 zone
->recent_scanned
[0] += count
[LRU_INACTIVE_ANON
];
1073 zone
->recent_scanned
[0] += count
[LRU_ACTIVE_ANON
];
1074 zone
->recent_scanned
[1] += count
[LRU_INACTIVE_FILE
];
1075 zone
->recent_scanned
[1] += count
[LRU_ACTIVE_FILE
];
1077 spin_unlock_irq(&zone
->lru_lock
);
1079 nr_scanned
+= nr_scan
;
1080 nr_freed
= shrink_page_list(&page_list
, sc
, PAGEOUT_IO_ASYNC
);
1083 * If we are direct reclaiming for contiguous pages and we do
1084 * not reclaim everything in the list, try again and wait
1085 * for IO to complete. This will stall high-order allocations
1086 * but that should be acceptable to the caller
1088 if (nr_freed
< nr_taken
&& !current_is_kswapd() &&
1089 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
) {
1090 congestion_wait(WRITE
, HZ
/10);
1093 * The attempt at page out may have made some
1094 * of the pages active, mark them inactive again.
1096 nr_active
= clear_active_flags(&page_list
, count
);
1097 count_vm_events(PGDEACTIVATE
, nr_active
);
1099 nr_freed
+= shrink_page_list(&page_list
, sc
,
1103 nr_reclaimed
+= nr_freed
;
1104 local_irq_disable();
1105 if (current_is_kswapd()) {
1106 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scan
);
1107 __count_vm_events(KSWAPD_STEAL
, nr_freed
);
1108 } else if (scan_global_lru(sc
))
1109 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scan
);
1111 __count_zone_vm_events(PGSTEAL
, zone
, nr_freed
);
1116 spin_lock(&zone
->lru_lock
);
1118 * Put back any unfreeable pages.
1120 while (!list_empty(&page_list
)) {
1122 page
= lru_to_page(&page_list
);
1123 VM_BUG_ON(PageLRU(page
));
1124 list_del(&page
->lru
);
1125 if (unlikely(!page_evictable(page
, NULL
))) {
1126 spin_unlock_irq(&zone
->lru_lock
);
1127 putback_lru_page(page
);
1128 spin_lock_irq(&zone
->lru_lock
);
1132 lru
= page_lru(page
);
1133 add_page_to_lru_list(zone
, page
, lru
);
1134 mem_cgroup_move_lists(page
, lru
);
1135 if (PageActive(page
) && scan_global_lru(sc
)) {
1136 int file
= !!page_is_file_cache(page
);
1137 zone
->recent_rotated
[file
]++;
1139 if (!pagevec_add(&pvec
, page
)) {
1140 spin_unlock_irq(&zone
->lru_lock
);
1141 __pagevec_release(&pvec
);
1142 spin_lock_irq(&zone
->lru_lock
);
1145 } while (nr_scanned
< max_scan
);
1146 spin_unlock(&zone
->lru_lock
);
1149 pagevec_release(&pvec
);
1150 return nr_reclaimed
;
1154 * We are about to scan this zone at a certain priority level. If that priority
1155 * level is smaller (ie: more urgent) than the previous priority, then note
1156 * that priority level within the zone. This is done so that when the next
1157 * process comes in to scan this zone, it will immediately start out at this
1158 * priority level rather than having to build up its own scanning priority.
1159 * Here, this priority affects only the reclaim-mapped threshold.
1161 static inline void note_zone_scanning_priority(struct zone
*zone
, int priority
)
1163 if (priority
< zone
->prev_priority
)
1164 zone
->prev_priority
= priority
;
1167 static inline int zone_is_near_oom(struct zone
*zone
)
1169 return zone
->pages_scanned
>= (zone_lru_pages(zone
) * 3);
1173 * This moves pages from the active list to the inactive list.
1175 * We move them the other way if the page is referenced by one or more
1176 * processes, from rmap.
1178 * If the pages are mostly unmapped, the processing is fast and it is
1179 * appropriate to hold zone->lru_lock across the whole operation. But if
1180 * the pages are mapped, the processing is slow (page_referenced()) so we
1181 * should drop zone->lru_lock around each page. It's impossible to balance
1182 * this, so instead we remove the pages from the LRU while processing them.
1183 * It is safe to rely on PG_active against the non-LRU pages in here because
1184 * nobody will play with that bit on a non-LRU page.
1186 * The downside is that we have to touch page->_count against each page.
1187 * But we had to alter page->flags anyway.
1191 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1192 struct scan_control
*sc
, int priority
, int file
)
1194 unsigned long pgmoved
;
1195 int pgdeactivate
= 0;
1196 unsigned long pgscanned
;
1197 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1198 LIST_HEAD(l_inactive
);
1200 struct pagevec pvec
;
1204 spin_lock_irq(&zone
->lru_lock
);
1205 pgmoved
= sc
->isolate_pages(nr_pages
, &l_hold
, &pgscanned
, sc
->order
,
1206 ISOLATE_ACTIVE
, zone
,
1207 sc
->mem_cgroup
, 1, file
);
1209 * zone->pages_scanned is used for detect zone's oom
1210 * mem_cgroup remembers nr_scan by itself.
1212 if (scan_global_lru(sc
)) {
1213 zone
->pages_scanned
+= pgscanned
;
1214 zone
->recent_scanned
[!!file
] += pgmoved
;
1218 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -pgmoved
);
1220 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -pgmoved
);
1221 spin_unlock_irq(&zone
->lru_lock
);
1224 while (!list_empty(&l_hold
)) {
1226 page
= lru_to_page(&l_hold
);
1227 list_del(&page
->lru
);
1229 if (unlikely(!page_evictable(page
, NULL
))) {
1230 putback_lru_page(page
);
1234 /* page_referenced clears PageReferenced */
1235 if (page_mapping_inuse(page
) &&
1236 page_referenced(page
, 0, sc
->mem_cgroup
))
1239 list_add(&page
->lru
, &l_inactive
);
1242 spin_lock_irq(&zone
->lru_lock
);
1244 * Count referenced pages from currently used mappings as
1245 * rotated, even though they are moved to the inactive list.
1246 * This helps balance scan pressure between file and anonymous
1247 * pages in get_scan_ratio.
1249 zone
->recent_rotated
[!!file
] += pgmoved
;
1252 * Move the pages to the [file or anon] inactive list.
1254 pagevec_init(&pvec
, 1);
1257 lru
= LRU_BASE
+ file
* LRU_FILE
;
1258 while (!list_empty(&l_inactive
)) {
1259 page
= lru_to_page(&l_inactive
);
1260 prefetchw_prev_lru_page(page
, &l_inactive
, flags
);
1261 VM_BUG_ON(PageLRU(page
));
1263 VM_BUG_ON(!PageActive(page
));
1264 ClearPageActive(page
);
1266 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1267 mem_cgroup_move_lists(page
, lru
);
1269 if (!pagevec_add(&pvec
, page
)) {
1270 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1271 spin_unlock_irq(&zone
->lru_lock
);
1272 pgdeactivate
+= pgmoved
;
1274 if (buffer_heads_over_limit
)
1275 pagevec_strip(&pvec
);
1276 __pagevec_release(&pvec
);
1277 spin_lock_irq(&zone
->lru_lock
);
1280 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1281 pgdeactivate
+= pgmoved
;
1282 if (buffer_heads_over_limit
) {
1283 spin_unlock_irq(&zone
->lru_lock
);
1284 pagevec_strip(&pvec
);
1285 spin_lock_irq(&zone
->lru_lock
);
1287 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1288 __count_vm_events(PGDEACTIVATE
, pgdeactivate
);
1289 spin_unlock_irq(&zone
->lru_lock
);
1291 pagevec_swap_free(&pvec
);
1293 pagevec_release(&pvec
);
1296 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1297 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1299 int file
= is_file_lru(lru
);
1301 if (lru
== LRU_ACTIVE_FILE
) {
1302 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1306 if (lru
== LRU_ACTIVE_ANON
&&
1307 (!scan_global_lru(sc
) || inactive_anon_is_low(zone
))) {
1308 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1311 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1315 * Determine how aggressively the anon and file LRU lists should be
1316 * scanned. The relative value of each set of LRU lists is determined
1317 * by looking at the fraction of the pages scanned we did rotate back
1318 * onto the active list instead of evict.
1320 * percent[0] specifies how much pressure to put on ram/swap backed
1321 * memory, while percent[1] determines pressure on the file LRUs.
1323 static void get_scan_ratio(struct zone
*zone
, struct scan_control
*sc
,
1324 unsigned long *percent
)
1326 unsigned long anon
, file
, free
;
1327 unsigned long anon_prio
, file_prio
;
1328 unsigned long ap
, fp
;
1330 anon
= zone_page_state(zone
, NR_ACTIVE_ANON
) +
1331 zone_page_state(zone
, NR_INACTIVE_ANON
);
1332 file
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
1333 zone_page_state(zone
, NR_INACTIVE_FILE
);
1334 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1336 /* If we have no swap space, do not bother scanning anon pages. */
1337 if (nr_swap_pages
<= 0) {
1343 /* If we have very few page cache pages, force-scan anon pages. */
1344 if (unlikely(file
+ free
<= zone
->pages_high
)) {
1351 * OK, so we have swap space and a fair amount of page cache
1352 * pages. We use the recently rotated / recently scanned
1353 * ratios to determine how valuable each cache is.
1355 * Because workloads change over time (and to avoid overflow)
1356 * we keep these statistics as a floating average, which ends
1357 * up weighing recent references more than old ones.
1359 * anon in [0], file in [1]
1361 if (unlikely(zone
->recent_scanned
[0] > anon
/ 4)) {
1362 spin_lock_irq(&zone
->lru_lock
);
1363 zone
->recent_scanned
[0] /= 2;
1364 zone
->recent_rotated
[0] /= 2;
1365 spin_unlock_irq(&zone
->lru_lock
);
1368 if (unlikely(zone
->recent_scanned
[1] > file
/ 4)) {
1369 spin_lock_irq(&zone
->lru_lock
);
1370 zone
->recent_scanned
[1] /= 2;
1371 zone
->recent_rotated
[1] /= 2;
1372 spin_unlock_irq(&zone
->lru_lock
);
1376 * With swappiness at 100, anonymous and file have the same priority.
1377 * This scanning priority is essentially the inverse of IO cost.
1379 anon_prio
= sc
->swappiness
;
1380 file_prio
= 200 - sc
->swappiness
;
1383 * The amount of pressure on anon vs file pages is inversely
1384 * proportional to the fraction of recently scanned pages on
1385 * each list that were recently referenced and in active use.
1387 ap
= (anon_prio
+ 1) * (zone
->recent_scanned
[0] + 1);
1388 ap
/= zone
->recent_rotated
[0] + 1;
1390 fp
= (file_prio
+ 1) * (zone
->recent_scanned
[1] + 1);
1391 fp
/= zone
->recent_rotated
[1] + 1;
1393 /* Normalize to percentages */
1394 percent
[0] = 100 * ap
/ (ap
+ fp
+ 1);
1395 percent
[1] = 100 - percent
[0];
1400 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1402 static unsigned long shrink_zone(int priority
, struct zone
*zone
,
1403 struct scan_control
*sc
)
1405 unsigned long nr
[NR_LRU_LISTS
];
1406 unsigned long nr_to_scan
;
1407 unsigned long nr_reclaimed
= 0;
1408 unsigned long percent
[2]; /* anon @ 0; file @ 1 */
1411 get_scan_ratio(zone
, sc
, percent
);
1413 for_each_evictable_lru(l
) {
1414 if (scan_global_lru(sc
)) {
1415 int file
= is_file_lru(l
);
1418 scan
= zone_page_state(zone
, NR_LRU_BASE
+ l
);
1421 scan
= (scan
* percent
[file
]) / 100;
1423 zone
->lru
[l
].nr_scan
+= scan
;
1424 nr
[l
] = zone
->lru
[l
].nr_scan
;
1425 if (nr
[l
] >= sc
->swap_cluster_max
)
1426 zone
->lru
[l
].nr_scan
= 0;
1431 * This reclaim occurs not because zone memory shortage
1432 * but because memory controller hits its limit.
1433 * Don't modify zone reclaim related data.
1435 nr
[l
] = mem_cgroup_calc_reclaim(sc
->mem_cgroup
, zone
,
1440 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1441 nr
[LRU_INACTIVE_FILE
]) {
1442 for_each_evictable_lru(l
) {
1444 nr_to_scan
= min(nr
[l
],
1445 (unsigned long)sc
->swap_cluster_max
);
1446 nr
[l
] -= nr_to_scan
;
1448 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1449 zone
, sc
, priority
);
1455 * Even if we did not try to evict anon pages at all, we want to
1456 * rebalance the anon lru active/inactive ratio.
1458 if (!scan_global_lru(sc
) || inactive_anon_is_low(zone
))
1459 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1460 else if (!scan_global_lru(sc
))
1461 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1463 throttle_vm_writeout(sc
->gfp_mask
);
1464 return nr_reclaimed
;
1468 * This is the direct reclaim path, for page-allocating processes. We only
1469 * try to reclaim pages from zones which will satisfy the caller's allocation
1472 * We reclaim from a zone even if that zone is over pages_high. Because:
1473 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1475 * b) The zones may be over pages_high but they must go *over* pages_high to
1476 * satisfy the `incremental min' zone defense algorithm.
1478 * Returns the number of reclaimed pages.
1480 * If a zone is deemed to be full of pinned pages then just give it a light
1481 * scan then give up on it.
1483 static unsigned long shrink_zones(int priority
, struct zonelist
*zonelist
,
1484 struct scan_control
*sc
)
1486 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1487 unsigned long nr_reclaimed
= 0;
1491 sc
->all_unreclaimable
= 1;
1492 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1493 if (!populated_zone(zone
))
1496 * Take care memory controller reclaiming has small influence
1499 if (scan_global_lru(sc
)) {
1500 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1502 note_zone_scanning_priority(zone
, priority
);
1504 if (zone_is_all_unreclaimable(zone
) &&
1505 priority
!= DEF_PRIORITY
)
1506 continue; /* Let kswapd poll it */
1507 sc
->all_unreclaimable
= 0;
1510 * Ignore cpuset limitation here. We just want to reduce
1511 * # of used pages by us regardless of memory shortage.
1513 sc
->all_unreclaimable
= 0;
1514 mem_cgroup_note_reclaim_priority(sc
->mem_cgroup
,
1518 nr_reclaimed
+= shrink_zone(priority
, zone
, sc
);
1521 return nr_reclaimed
;
1525 * This is the main entry point to direct page reclaim.
1527 * If a full scan of the inactive list fails to free enough memory then we
1528 * are "out of memory" and something needs to be killed.
1530 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1531 * high - the zone may be full of dirty or under-writeback pages, which this
1532 * caller can't do much about. We kick pdflush and take explicit naps in the
1533 * hope that some of these pages can be written. But if the allocating task
1534 * holds filesystem locks which prevent writeout this might not work, and the
1535 * allocation attempt will fail.
1537 * returns: 0, if no pages reclaimed
1538 * else, the number of pages reclaimed
1540 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
1541 struct scan_control
*sc
)
1544 unsigned long ret
= 0;
1545 unsigned long total_scanned
= 0;
1546 unsigned long nr_reclaimed
= 0;
1547 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1548 unsigned long lru_pages
= 0;
1551 enum zone_type high_zoneidx
= gfp_zone(sc
->gfp_mask
);
1553 delayacct_freepages_start();
1555 if (scan_global_lru(sc
))
1556 count_vm_event(ALLOCSTALL
);
1558 * mem_cgroup will not do shrink_slab.
1560 if (scan_global_lru(sc
)) {
1561 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1563 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1566 lru_pages
+= zone_lru_pages(zone
);
1570 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1573 disable_swap_token();
1574 nr_reclaimed
+= shrink_zones(priority
, zonelist
, sc
);
1576 * Don't shrink slabs when reclaiming memory from
1577 * over limit cgroups
1579 if (scan_global_lru(sc
)) {
1580 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
1581 if (reclaim_state
) {
1582 nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1583 reclaim_state
->reclaimed_slab
= 0;
1586 total_scanned
+= sc
->nr_scanned
;
1587 if (nr_reclaimed
>= sc
->swap_cluster_max
) {
1593 * Try to write back as many pages as we just scanned. This
1594 * tends to cause slow streaming writers to write data to the
1595 * disk smoothly, at the dirtying rate, which is nice. But
1596 * that's undesirable in laptop mode, where we *want* lumpy
1597 * writeout. So in laptop mode, write out the whole world.
1599 if (total_scanned
> sc
->swap_cluster_max
+
1600 sc
->swap_cluster_max
/ 2) {
1601 wakeup_pdflush(laptop_mode
? 0 : total_scanned
);
1602 sc
->may_writepage
= 1;
1605 /* Take a nap, wait for some writeback to complete */
1606 if (sc
->nr_scanned
&& priority
< DEF_PRIORITY
- 2)
1607 congestion_wait(WRITE
, HZ
/10);
1609 /* top priority shrink_zones still had more to do? don't OOM, then */
1610 if (!sc
->all_unreclaimable
&& scan_global_lru(sc
))
1614 * Now that we've scanned all the zones at this priority level, note
1615 * that level within the zone so that the next thread which performs
1616 * scanning of this zone will immediately start out at this priority
1617 * level. This affects only the decision whether or not to bring
1618 * mapped pages onto the inactive list.
1623 if (scan_global_lru(sc
)) {
1624 for_each_zone_zonelist(zone
, z
, zonelist
, high_zoneidx
) {
1626 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1629 zone
->prev_priority
= priority
;
1632 mem_cgroup_record_reclaim_priority(sc
->mem_cgroup
, priority
);
1634 delayacct_freepages_end();
1639 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
1642 struct scan_control sc
= {
1643 .gfp_mask
= gfp_mask
,
1644 .may_writepage
= !laptop_mode
,
1645 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1647 .swappiness
= vm_swappiness
,
1650 .isolate_pages
= isolate_pages_global
,
1653 return do_try_to_free_pages(zonelist
, &sc
);
1656 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1658 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
1661 struct scan_control sc
= {
1662 .may_writepage
= !laptop_mode
,
1664 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1665 .swappiness
= vm_swappiness
,
1667 .mem_cgroup
= mem_cont
,
1668 .isolate_pages
= mem_cgroup_isolate_pages
,
1670 struct zonelist
*zonelist
;
1672 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1673 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1674 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
1675 return do_try_to_free_pages(zonelist
, &sc
);
1680 * For kswapd, balance_pgdat() will work across all this node's zones until
1681 * they are all at pages_high.
1683 * Returns the number of pages which were actually freed.
1685 * There is special handling here for zones which are full of pinned pages.
1686 * This can happen if the pages are all mlocked, or if they are all used by
1687 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1688 * What we do is to detect the case where all pages in the zone have been
1689 * scanned twice and there has been zero successful reclaim. Mark the zone as
1690 * dead and from now on, only perform a short scan. Basically we're polling
1691 * the zone for when the problem goes away.
1693 * kswapd scans the zones in the highmem->normal->dma direction. It skips
1694 * zones which have free_pages > pages_high, but once a zone is found to have
1695 * free_pages <= pages_high, we scan that zone and the lower zones regardless
1696 * of the number of free pages in the lower zones. This interoperates with
1697 * the page allocator fallback scheme to ensure that aging of pages is balanced
1700 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
)
1705 unsigned long total_scanned
;
1706 unsigned long nr_reclaimed
;
1707 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1708 struct scan_control sc
= {
1709 .gfp_mask
= GFP_KERNEL
,
1711 .swap_cluster_max
= SWAP_CLUSTER_MAX
,
1712 .swappiness
= vm_swappiness
,
1715 .isolate_pages
= isolate_pages_global
,
1718 * temp_priority is used to remember the scanning priority at which
1719 * this zone was successfully refilled to free_pages == pages_high.
1721 int temp_priority
[MAX_NR_ZONES
];
1726 sc
.may_writepage
= !laptop_mode
;
1727 count_vm_event(PAGEOUTRUN
);
1729 for (i
= 0; i
< pgdat
->nr_zones
; i
++)
1730 temp_priority
[i
] = DEF_PRIORITY
;
1732 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1733 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
1734 unsigned long lru_pages
= 0;
1736 /* The swap token gets in the way of swapout... */
1738 disable_swap_token();
1743 * Scan in the highmem->dma direction for the highest
1744 * zone which needs scanning
1746 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
1747 struct zone
*zone
= pgdat
->node_zones
+ i
;
1749 if (!populated_zone(zone
))
1752 if (zone_is_all_unreclaimable(zone
) &&
1753 priority
!= DEF_PRIORITY
)
1757 * Do some background aging of the anon list, to give
1758 * pages a chance to be referenced before reclaiming.
1760 if (inactive_anon_is_low(zone
))
1761 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
1764 if (!zone_watermark_ok(zone
, order
, zone
->pages_high
,
1773 for (i
= 0; i
<= end_zone
; i
++) {
1774 struct zone
*zone
= pgdat
->node_zones
+ i
;
1776 lru_pages
+= zone_lru_pages(zone
);
1780 * Now scan the zone in the dma->highmem direction, stopping
1781 * at the last zone which needs scanning.
1783 * We do this because the page allocator works in the opposite
1784 * direction. This prevents the page allocator from allocating
1785 * pages behind kswapd's direction of progress, which would
1786 * cause too much scanning of the lower zones.
1788 for (i
= 0; i
<= end_zone
; i
++) {
1789 struct zone
*zone
= pgdat
->node_zones
+ i
;
1792 if (!populated_zone(zone
))
1795 if (zone_is_all_unreclaimable(zone
) &&
1796 priority
!= DEF_PRIORITY
)
1799 if (!zone_watermark_ok(zone
, order
, zone
->pages_high
,
1802 temp_priority
[i
] = priority
;
1804 note_zone_scanning_priority(zone
, priority
);
1806 * We put equal pressure on every zone, unless one
1807 * zone has way too many pages free already.
1809 if (!zone_watermark_ok(zone
, order
, 8*zone
->pages_high
,
1811 nr_reclaimed
+= shrink_zone(priority
, zone
, &sc
);
1812 reclaim_state
->reclaimed_slab
= 0;
1813 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
1815 nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1816 total_scanned
+= sc
.nr_scanned
;
1817 if (zone_is_all_unreclaimable(zone
))
1819 if (nr_slab
== 0 && zone
->pages_scanned
>=
1820 (zone_lru_pages(zone
) * 6))
1822 ZONE_ALL_UNRECLAIMABLE
);
1824 * If we've done a decent amount of scanning and
1825 * the reclaim ratio is low, start doing writepage
1826 * even in laptop mode
1828 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
1829 total_scanned
> nr_reclaimed
+ nr_reclaimed
/ 2)
1830 sc
.may_writepage
= 1;
1833 break; /* kswapd: all done */
1835 * OK, kswapd is getting into trouble. Take a nap, then take
1836 * another pass across the zones.
1838 if (total_scanned
&& priority
< DEF_PRIORITY
- 2)
1839 congestion_wait(WRITE
, HZ
/10);
1842 * We do this so kswapd doesn't build up large priorities for
1843 * example when it is freeing in parallel with allocators. It
1844 * matches the direct reclaim path behaviour in terms of impact
1845 * on zone->*_priority.
1847 if (nr_reclaimed
>= SWAP_CLUSTER_MAX
)
1852 * Note within each zone the priority level at which this zone was
1853 * brought into a happy state. So that the next thread which scans this
1854 * zone will start out at that priority level.
1856 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
1857 struct zone
*zone
= pgdat
->node_zones
+ i
;
1859 zone
->prev_priority
= temp_priority
[i
];
1861 if (!all_zones_ok
) {
1869 return nr_reclaimed
;
1873 * The background pageout daemon, started as a kernel thread
1874 * from the init process.
1876 * This basically trickles out pages so that we have _some_
1877 * free memory available even if there is no other activity
1878 * that frees anything up. This is needed for things like routing
1879 * etc, where we otherwise might have all activity going on in
1880 * asynchronous contexts that cannot page things out.
1882 * If there are applications that are active memory-allocators
1883 * (most normal use), this basically shouldn't matter.
1885 static int kswapd(void *p
)
1887 unsigned long order
;
1888 pg_data_t
*pgdat
= (pg_data_t
*)p
;
1889 struct task_struct
*tsk
= current
;
1891 struct reclaim_state reclaim_state
= {
1892 .reclaimed_slab
= 0,
1894 node_to_cpumask_ptr(cpumask
, pgdat
->node_id
);
1896 if (!cpumask_empty(cpumask
))
1897 set_cpus_allowed_ptr(tsk
, cpumask
);
1898 current
->reclaim_state
= &reclaim_state
;
1901 * Tell the memory management that we're a "memory allocator",
1902 * and that if we need more memory we should get access to it
1903 * regardless (see "__alloc_pages()"). "kswapd" should
1904 * never get caught in the normal page freeing logic.
1906 * (Kswapd normally doesn't need memory anyway, but sometimes
1907 * you need a small amount of memory in order to be able to
1908 * page out something else, and this flag essentially protects
1909 * us from recursively trying to free more memory as we're
1910 * trying to free the first piece of memory in the first place).
1912 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
1917 unsigned long new_order
;
1919 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
1920 new_order
= pgdat
->kswapd_max_order
;
1921 pgdat
->kswapd_max_order
= 0;
1922 if (order
< new_order
) {
1924 * Don't sleep if someone wants a larger 'order'
1929 if (!freezing(current
))
1932 order
= pgdat
->kswapd_max_order
;
1934 finish_wait(&pgdat
->kswapd_wait
, &wait
);
1936 if (!try_to_freeze()) {
1937 /* We can speed up thawing tasks if we don't call
1938 * balance_pgdat after returning from the refrigerator
1940 balance_pgdat(pgdat
, order
);
1947 * A zone is low on free memory, so wake its kswapd task to service it.
1949 void wakeup_kswapd(struct zone
*zone
, int order
)
1953 if (!populated_zone(zone
))
1956 pgdat
= zone
->zone_pgdat
;
1957 if (zone_watermark_ok(zone
, order
, zone
->pages_low
, 0, 0))
1959 if (pgdat
->kswapd_max_order
< order
)
1960 pgdat
->kswapd_max_order
= order
;
1961 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1963 if (!waitqueue_active(&pgdat
->kswapd_wait
))
1965 wake_up_interruptible(&pgdat
->kswapd_wait
);
1968 unsigned long global_lru_pages(void)
1970 return global_page_state(NR_ACTIVE_ANON
)
1971 + global_page_state(NR_ACTIVE_FILE
)
1972 + global_page_state(NR_INACTIVE_ANON
)
1973 + global_page_state(NR_INACTIVE_FILE
);
1978 * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
1979 * from LRU lists system-wide, for given pass and priority, and returns the
1980 * number of reclaimed pages
1982 * For pass > 3 we also try to shrink the LRU lists that contain a few pages
1984 static unsigned long shrink_all_zones(unsigned long nr_pages
, int prio
,
1985 int pass
, struct scan_control
*sc
)
1988 unsigned long nr_to_scan
, ret
= 0;
1991 for_each_zone(zone
) {
1993 if (!populated_zone(zone
))
1996 if (zone_is_all_unreclaimable(zone
) && prio
!= DEF_PRIORITY
)
1999 for_each_evictable_lru(l
) {
2000 /* For pass = 0, we don't shrink the active list */
2002 (l
== LRU_ACTIVE
|| l
== LRU_ACTIVE_FILE
))
2005 zone
->lru
[l
].nr_scan
+=
2006 (zone_page_state(zone
, NR_LRU_BASE
+ l
)
2008 if (zone
->lru
[l
].nr_scan
>= nr_pages
|| pass
> 3) {
2009 zone
->lru
[l
].nr_scan
= 0;
2010 nr_to_scan
= min(nr_pages
,
2011 zone_page_state(zone
,
2013 ret
+= shrink_list(l
, nr_to_scan
, zone
,
2015 if (ret
>= nr_pages
)
2025 * Try to free `nr_pages' of memory, system-wide, and return the number of
2028 * Rather than trying to age LRUs the aim is to preserve the overall
2029 * LRU order by reclaiming preferentially
2030 * inactive > active > active referenced > active mapped
2032 unsigned long shrink_all_memory(unsigned long nr_pages
)
2034 unsigned long lru_pages
, nr_slab
;
2035 unsigned long ret
= 0;
2037 struct reclaim_state reclaim_state
;
2038 struct scan_control sc
= {
2039 .gfp_mask
= GFP_KERNEL
,
2041 .swap_cluster_max
= nr_pages
,
2043 .swappiness
= vm_swappiness
,
2044 .isolate_pages
= isolate_pages_global
,
2047 current
->reclaim_state
= &reclaim_state
;
2049 lru_pages
= global_lru_pages();
2050 nr_slab
= global_page_state(NR_SLAB_RECLAIMABLE
);
2051 /* If slab caches are huge, it's better to hit them first */
2052 while (nr_slab
>= lru_pages
) {
2053 reclaim_state
.reclaimed_slab
= 0;
2054 shrink_slab(nr_pages
, sc
.gfp_mask
, lru_pages
);
2055 if (!reclaim_state
.reclaimed_slab
)
2058 ret
+= reclaim_state
.reclaimed_slab
;
2059 if (ret
>= nr_pages
)
2062 nr_slab
-= reclaim_state
.reclaimed_slab
;
2066 * We try to shrink LRUs in 5 passes:
2067 * 0 = Reclaim from inactive_list only
2068 * 1 = Reclaim from active list but don't reclaim mapped
2069 * 2 = 2nd pass of type 1
2070 * 3 = Reclaim mapped (normal reclaim)
2071 * 4 = 2nd pass of type 3
2073 for (pass
= 0; pass
< 5; pass
++) {
2076 /* Force reclaiming mapped pages in the passes #3 and #4 */
2079 sc
.swappiness
= 100;
2082 for (prio
= DEF_PRIORITY
; prio
>= 0; prio
--) {
2083 unsigned long nr_to_scan
= nr_pages
- ret
;
2086 ret
+= shrink_all_zones(nr_to_scan
, prio
, pass
, &sc
);
2087 if (ret
>= nr_pages
)
2090 reclaim_state
.reclaimed_slab
= 0;
2091 shrink_slab(sc
.nr_scanned
, sc
.gfp_mask
,
2092 global_lru_pages());
2093 ret
+= reclaim_state
.reclaimed_slab
;
2094 if (ret
>= nr_pages
)
2097 if (sc
.nr_scanned
&& prio
< DEF_PRIORITY
- 2)
2098 congestion_wait(WRITE
, HZ
/ 10);
2103 * If ret = 0, we could not shrink LRUs, but there may be something
2108 reclaim_state
.reclaimed_slab
= 0;
2109 shrink_slab(nr_pages
, sc
.gfp_mask
, global_lru_pages());
2110 ret
+= reclaim_state
.reclaimed_slab
;
2111 } while (ret
< nr_pages
&& reclaim_state
.reclaimed_slab
> 0);
2115 current
->reclaim_state
= NULL
;
2121 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2122 not required for correctness. So if the last cpu in a node goes
2123 away, we get changed to run anywhere: as the first one comes back,
2124 restore their cpu bindings. */
2125 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2126 unsigned long action
, void *hcpu
)
2130 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2131 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2132 pg_data_t
*pgdat
= NODE_DATA(nid
);
2133 node_to_cpumask_ptr(mask
, pgdat
->node_id
);
2135 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2136 /* One of our CPUs online: restore mask */
2137 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2144 * This kswapd start function will be called by init and node-hot-add.
2145 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2147 int kswapd_run(int nid
)
2149 pg_data_t
*pgdat
= NODE_DATA(nid
);
2155 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2156 if (IS_ERR(pgdat
->kswapd
)) {
2157 /* failure at boot is fatal */
2158 BUG_ON(system_state
== SYSTEM_BOOTING
);
2159 printk("Failed to start kswapd on node %d\n",nid
);
2165 static int __init
kswapd_init(void)
2170 for_each_node_state(nid
, N_HIGH_MEMORY
)
2172 hotcpu_notifier(cpu_callback
, 0);
2176 module_init(kswapd_init
)
2182 * If non-zero call zone_reclaim when the number of free pages falls below
2185 int zone_reclaim_mode __read_mostly
;
2187 #define RECLAIM_OFF 0
2188 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2189 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2190 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2193 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2194 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2197 #define ZONE_RECLAIM_PRIORITY 4
2200 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2203 int sysctl_min_unmapped_ratio
= 1;
2206 * If the number of slab pages in a zone grows beyond this percentage then
2207 * slab reclaim needs to occur.
2209 int sysctl_min_slab_ratio
= 5;
2212 * Try to free up some pages from this zone through reclaim.
2214 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2216 /* Minimum pages needed in order to stay on node */
2217 const unsigned long nr_pages
= 1 << order
;
2218 struct task_struct
*p
= current
;
2219 struct reclaim_state reclaim_state
;
2221 unsigned long nr_reclaimed
= 0;
2222 struct scan_control sc
= {
2223 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2224 .may_swap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2225 .swap_cluster_max
= max_t(unsigned long, nr_pages
,
2227 .gfp_mask
= gfp_mask
,
2228 .swappiness
= vm_swappiness
,
2229 .isolate_pages
= isolate_pages_global
,
2231 unsigned long slab_reclaimable
;
2233 disable_swap_token();
2236 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2237 * and we also need to be able to write out pages for RECLAIM_WRITE
2240 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2241 reclaim_state
.reclaimed_slab
= 0;
2242 p
->reclaim_state
= &reclaim_state
;
2244 if (zone_page_state(zone
, NR_FILE_PAGES
) -
2245 zone_page_state(zone
, NR_FILE_MAPPED
) >
2246 zone
->min_unmapped_pages
) {
2248 * Free memory by calling shrink zone with increasing
2249 * priorities until we have enough memory freed.
2251 priority
= ZONE_RECLAIM_PRIORITY
;
2253 note_zone_scanning_priority(zone
, priority
);
2254 nr_reclaimed
+= shrink_zone(priority
, zone
, &sc
);
2256 } while (priority
>= 0 && nr_reclaimed
< nr_pages
);
2259 slab_reclaimable
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2260 if (slab_reclaimable
> zone
->min_slab_pages
) {
2262 * shrink_slab() does not currently allow us to determine how
2263 * many pages were freed in this zone. So we take the current
2264 * number of slab pages and shake the slab until it is reduced
2265 * by the same nr_pages that we used for reclaiming unmapped
2268 * Note that shrink_slab will free memory on all zones and may
2271 while (shrink_slab(sc
.nr_scanned
, gfp_mask
, order
) &&
2272 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) >
2273 slab_reclaimable
- nr_pages
)
2277 * Update nr_reclaimed by the number of slab pages we
2278 * reclaimed from this zone.
2280 nr_reclaimed
+= slab_reclaimable
-
2281 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2284 p
->reclaim_state
= NULL
;
2285 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
2286 return nr_reclaimed
>= nr_pages
;
2289 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2295 * Zone reclaim reclaims unmapped file backed pages and
2296 * slab pages if we are over the defined limits.
2298 * A small portion of unmapped file backed pages is needed for
2299 * file I/O otherwise pages read by file I/O will be immediately
2300 * thrown out if the zone is overallocated. So we do not reclaim
2301 * if less than a specified percentage of the zone is used by
2302 * unmapped file backed pages.
2304 if (zone_page_state(zone
, NR_FILE_PAGES
) -
2305 zone_page_state(zone
, NR_FILE_MAPPED
) <= zone
->min_unmapped_pages
2306 && zone_page_state(zone
, NR_SLAB_RECLAIMABLE
)
2307 <= zone
->min_slab_pages
)
2310 if (zone_is_all_unreclaimable(zone
))
2314 * Do not scan if the allocation should not be delayed.
2316 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
2320 * Only run zone reclaim on the local zone or on zones that do not
2321 * have associated processors. This will favor the local processor
2322 * over remote processors and spread off node memory allocations
2323 * as wide as possible.
2325 node_id
= zone_to_nid(zone
);
2326 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
2329 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
2331 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
2332 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
2338 #ifdef CONFIG_UNEVICTABLE_LRU
2340 * page_evictable - test whether a page is evictable
2341 * @page: the page to test
2342 * @vma: the VMA in which the page is or will be mapped, may be NULL
2344 * Test whether page is evictable--i.e., should be placed on active/inactive
2345 * lists vs unevictable list. The vma argument is !NULL when called from the
2346 * fault path to determine how to instantate a new page.
2348 * Reasons page might not be evictable:
2349 * (1) page's mapping marked unevictable
2350 * (2) page is part of an mlocked VMA
2353 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
2356 if (mapping_unevictable(page_mapping(page
)))
2359 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
2366 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2367 * @page: page to check evictability and move to appropriate lru list
2368 * @zone: zone page is in
2370 * Checks a page for evictability and moves the page to the appropriate
2373 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2374 * have PageUnevictable set.
2376 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
2378 VM_BUG_ON(PageActive(page
));
2381 ClearPageUnevictable(page
);
2382 if (page_evictable(page
, NULL
)) {
2383 enum lru_list l
= LRU_INACTIVE_ANON
+ page_is_file_cache(page
);
2385 __dec_zone_state(zone
, NR_UNEVICTABLE
);
2386 list_move(&page
->lru
, &zone
->lru
[l
].list
);
2387 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
2388 __count_vm_event(UNEVICTABLE_PGRESCUED
);
2391 * rotate unevictable list
2393 SetPageUnevictable(page
);
2394 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
2395 if (page_evictable(page
, NULL
))
2401 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2402 * @mapping: struct address_space to scan for evictable pages
2404 * Scan all pages in mapping. Check unevictable pages for
2405 * evictability and move them to the appropriate zone lru list.
2407 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
2410 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
2413 struct pagevec pvec
;
2415 if (mapping
->nrpages
== 0)
2418 pagevec_init(&pvec
, 0);
2419 while (next
< end
&&
2420 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
2426 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
2427 struct page
*page
= pvec
.pages
[i
];
2428 pgoff_t page_index
= page
->index
;
2429 struct zone
*pagezone
= page_zone(page
);
2432 if (page_index
> next
)
2436 if (pagezone
!= zone
) {
2438 spin_unlock_irq(&zone
->lru_lock
);
2440 spin_lock_irq(&zone
->lru_lock
);
2443 if (PageLRU(page
) && PageUnevictable(page
))
2444 check_move_unevictable_page(page
, zone
);
2447 spin_unlock_irq(&zone
->lru_lock
);
2448 pagevec_release(&pvec
);
2450 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
2456 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2457 * @zone - zone of which to scan the unevictable list
2459 * Scan @zone's unevictable LRU lists to check for pages that have become
2460 * evictable. Move those that have to @zone's inactive list where they
2461 * become candidates for reclaim, unless shrink_inactive_zone() decides
2462 * to reactivate them. Pages that are still unevictable are rotated
2463 * back onto @zone's unevictable list.
2465 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2466 void scan_zone_unevictable_pages(struct zone
*zone
)
2468 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
2470 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
2472 while (nr_to_scan
> 0) {
2473 unsigned long batch_size
= min(nr_to_scan
,
2474 SCAN_UNEVICTABLE_BATCH_SIZE
);
2476 spin_lock_irq(&zone
->lru_lock
);
2477 for (scan
= 0; scan
< batch_size
; scan
++) {
2478 struct page
*page
= lru_to_page(l_unevictable
);
2480 if (!trylock_page(page
))
2483 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
2485 if (likely(PageLRU(page
) && PageUnevictable(page
)))
2486 check_move_unevictable_page(page
, zone
);
2490 spin_unlock_irq(&zone
->lru_lock
);
2492 nr_to_scan
-= batch_size
;
2498 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2500 * A really big hammer: scan all zones' unevictable LRU lists to check for
2501 * pages that have become evictable. Move those back to the zones'
2502 * inactive list where they become candidates for reclaim.
2503 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2504 * and we add swap to the system. As such, it runs in the context of a task
2505 * that has possibly/probably made some previously unevictable pages
2508 void scan_all_zones_unevictable_pages(void)
2512 for_each_zone(zone
) {
2513 scan_zone_unevictable_pages(zone
);
2518 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2519 * all nodes' unevictable lists for evictable pages
2521 unsigned long scan_unevictable_pages
;
2523 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
2524 struct file
*file
, void __user
*buffer
,
2525 size_t *length
, loff_t
*ppos
)
2527 proc_doulongvec_minmax(table
, write
, file
, buffer
, length
, ppos
);
2529 if (write
&& *(unsigned long *)table
->data
)
2530 scan_all_zones_unevictable_pages();
2532 scan_unevictable_pages
= 0;
2537 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2538 * a specified node's per zone unevictable lists for evictable pages.
2541 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
2542 struct sysdev_attribute
*attr
,
2545 return sprintf(buf
, "0\n"); /* always zero; should fit... */
2548 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
2549 struct sysdev_attribute
*attr
,
2550 const char *buf
, size_t count
)
2552 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
2555 unsigned long req
= strict_strtoul(buf
, 10, &res
);
2558 return 1; /* zero is no-op */
2560 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
2561 if (!populated_zone(zone
))
2563 scan_zone_unevictable_pages(zone
);
2569 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
2570 read_scan_unevictable_node
,
2571 write_scan_unevictable_node
);
2573 int scan_unevictable_register_node(struct node
*node
)
2575 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
2578 void scan_unevictable_unregister_node(struct node
*node
)
2580 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);