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/gfp.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>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/vmscan.h>
55 /* Incremented by the number of inactive pages that were scanned */
56 unsigned long nr_scanned
;
58 /* Number of pages freed so far during a call to shrink_zones() */
59 unsigned long nr_reclaimed
;
61 /* How many pages shrink_list() should reclaim */
62 unsigned long nr_to_reclaim
;
64 unsigned long hibernation_mode
;
66 /* This context's GFP mask */
71 /* Can mapped pages be reclaimed? */
74 /* Can pages be swapped as part of reclaim? */
82 * Intend to reclaim enough contenious memory rather than to reclaim
83 * enough amount memory. I.e, it's the mode for high order allocation.
85 bool lumpy_reclaim_mode
;
87 /* Which cgroup do we reclaim from */
88 struct mem_cgroup
*mem_cgroup
;
91 * Nodemask of nodes allowed by the caller. If NULL, all nodes
97 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
99 #ifdef ARCH_HAS_PREFETCH
100 #define prefetch_prev_lru_page(_page, _base, _field) \
102 if ((_page)->lru.prev != _base) { \
105 prev = lru_to_page(&(_page->lru)); \
106 prefetch(&prev->_field); \
110 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
113 #ifdef ARCH_HAS_PREFETCHW
114 #define prefetchw_prev_lru_page(_page, _base, _field) \
116 if ((_page)->lru.prev != _base) { \
119 prev = lru_to_page(&(_page->lru)); \
120 prefetchw(&prev->_field); \
124 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
128 * From 0 .. 100. Higher means more swappy.
130 int vm_swappiness
= 60;
131 long vm_total_pages
; /* The total number of pages which the VM controls */
133 static LIST_HEAD(shrinker_list
);
134 static DECLARE_RWSEM(shrinker_rwsem
);
136 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
137 #define scanning_global_lru(sc) (!(sc)->mem_cgroup)
139 #define scanning_global_lru(sc) (1)
142 static struct zone_reclaim_stat
*get_reclaim_stat(struct zone
*zone
,
143 struct scan_control
*sc
)
145 if (!scanning_global_lru(sc
))
146 return mem_cgroup_get_reclaim_stat(sc
->mem_cgroup
, zone
);
148 return &zone
->reclaim_stat
;
151 static unsigned long zone_nr_lru_pages(struct zone
*zone
,
152 struct scan_control
*sc
, enum lru_list lru
)
154 if (!scanning_global_lru(sc
))
155 return mem_cgroup_zone_nr_pages(sc
->mem_cgroup
, zone
, lru
);
157 return zone_page_state(zone
, NR_LRU_BASE
+ lru
);
162 * Add a shrinker callback to be called from the vm
164 void register_shrinker(struct shrinker
*shrinker
)
167 down_write(&shrinker_rwsem
);
168 list_add_tail(&shrinker
->list
, &shrinker_list
);
169 up_write(&shrinker_rwsem
);
171 EXPORT_SYMBOL(register_shrinker
);
176 void unregister_shrinker(struct shrinker
*shrinker
)
178 down_write(&shrinker_rwsem
);
179 list_del(&shrinker
->list
);
180 up_write(&shrinker_rwsem
);
182 EXPORT_SYMBOL(unregister_shrinker
);
184 #define SHRINK_BATCH 128
186 * Call the shrink functions to age shrinkable caches
188 * Here we assume it costs one seek to replace a lru page and that it also
189 * takes a seek to recreate a cache object. With this in mind we age equal
190 * percentages of the lru and ageable caches. This should balance the seeks
191 * generated by these structures.
193 * If the vm encountered mapped pages on the LRU it increase the pressure on
194 * slab to avoid swapping.
196 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
198 * `lru_pages' represents the number of on-LRU pages in all the zones which
199 * are eligible for the caller's allocation attempt. It is used for balancing
200 * slab reclaim versus page reclaim.
202 * Returns the number of slab objects which we shrunk.
204 unsigned long shrink_slab(unsigned long scanned
, gfp_t gfp_mask
,
205 unsigned long lru_pages
)
207 struct shrinker
*shrinker
;
208 unsigned long ret
= 0;
211 scanned
= SWAP_CLUSTER_MAX
;
213 if (!down_read_trylock(&shrinker_rwsem
))
214 return 1; /* Assume we'll be able to shrink next time */
216 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
217 unsigned long long delta
;
218 unsigned long total_scan
;
219 unsigned long max_pass
;
221 max_pass
= (*shrinker
->shrink
)(shrinker
, 0, gfp_mask
);
222 delta
= (4 * scanned
) / shrinker
->seeks
;
224 do_div(delta
, lru_pages
+ 1);
225 shrinker
->nr
+= delta
;
226 if (shrinker
->nr
< 0) {
227 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
229 shrinker
->shrink
, shrinker
->nr
);
230 shrinker
->nr
= max_pass
;
234 * Avoid risking looping forever due to too large nr value:
235 * never try to free more than twice the estimate number of
238 if (shrinker
->nr
> max_pass
* 2)
239 shrinker
->nr
= max_pass
* 2;
241 total_scan
= shrinker
->nr
;
244 while (total_scan
>= SHRINK_BATCH
) {
245 long this_scan
= SHRINK_BATCH
;
249 nr_before
= (*shrinker
->shrink
)(shrinker
, 0, gfp_mask
);
250 shrink_ret
= (*shrinker
->shrink
)(shrinker
, this_scan
,
252 if (shrink_ret
== -1)
254 if (shrink_ret
< nr_before
)
255 ret
+= nr_before
- shrink_ret
;
256 count_vm_events(SLABS_SCANNED
, this_scan
);
257 total_scan
-= this_scan
;
262 shrinker
->nr
+= total_scan
;
264 up_read(&shrinker_rwsem
);
268 static inline int is_page_cache_freeable(struct page
*page
)
271 * A freeable page cache page is referenced only by the caller
272 * that isolated the page, the page cache radix tree and
273 * optional buffer heads at page->private.
275 return page_count(page
) - page_has_private(page
) == 2;
278 static int may_write_to_queue(struct backing_dev_info
*bdi
)
280 if (current
->flags
& PF_SWAPWRITE
)
282 if (!bdi_write_congested(bdi
))
284 if (bdi
== current
->backing_dev_info
)
290 * We detected a synchronous write error writing a page out. Probably
291 * -ENOSPC. We need to propagate that into the address_space for a subsequent
292 * fsync(), msync() or close().
294 * The tricky part is that after writepage we cannot touch the mapping: nothing
295 * prevents it from being freed up. But we have a ref on the page and once
296 * that page is locked, the mapping is pinned.
298 * We're allowed to run sleeping lock_page() here because we know the caller has
301 static void handle_write_error(struct address_space
*mapping
,
302 struct page
*page
, int error
)
304 lock_page_nosync(page
);
305 if (page_mapping(page
) == mapping
)
306 mapping_set_error(mapping
, error
);
310 /* Request for sync pageout. */
316 /* possible outcome of pageout() */
318 /* failed to write page out, page is locked */
320 /* move page to the active list, page is locked */
322 /* page has been sent to the disk successfully, page is unlocked */
324 /* page is clean and locked */
329 * pageout is called by shrink_page_list() for each dirty page.
330 * Calls ->writepage().
332 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
333 enum pageout_io sync_writeback
)
336 * If the page is dirty, only perform writeback if that write
337 * will be non-blocking. To prevent this allocation from being
338 * stalled by pagecache activity. But note that there may be
339 * stalls if we need to run get_block(). We could test
340 * PagePrivate for that.
342 * If this process is currently in __generic_file_aio_write() against
343 * this page's queue, we can perform writeback even if that
346 * If the page is swapcache, write it back even if that would
347 * block, for some throttling. This happens by accident, because
348 * swap_backing_dev_info is bust: it doesn't reflect the
349 * congestion state of the swapdevs. Easy to fix, if needed.
351 if (!is_page_cache_freeable(page
))
355 * Some data journaling orphaned pages can have
356 * page->mapping == NULL while being dirty with clean buffers.
358 if (page_has_private(page
)) {
359 if (try_to_free_buffers(page
)) {
360 ClearPageDirty(page
);
361 printk("%s: orphaned page\n", __func__
);
367 if (mapping
->a_ops
->writepage
== NULL
)
368 return PAGE_ACTIVATE
;
369 if (!may_write_to_queue(mapping
->backing_dev_info
))
372 if (clear_page_dirty_for_io(page
)) {
374 struct writeback_control wbc
= {
375 .sync_mode
= WB_SYNC_NONE
,
376 .nr_to_write
= SWAP_CLUSTER_MAX
,
378 .range_end
= LLONG_MAX
,
383 SetPageReclaim(page
);
384 res
= mapping
->a_ops
->writepage(page
, &wbc
);
386 handle_write_error(mapping
, page
, res
);
387 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
388 ClearPageReclaim(page
);
389 return PAGE_ACTIVATE
;
393 * Wait on writeback if requested to. This happens when
394 * direct reclaiming a large contiguous area and the
395 * first attempt to free a range of pages fails.
397 if (PageWriteback(page
) && sync_writeback
== PAGEOUT_IO_SYNC
)
398 wait_on_page_writeback(page
);
400 if (!PageWriteback(page
)) {
401 /* synchronous write or broken a_ops? */
402 ClearPageReclaim(page
);
404 trace_mm_vmscan_writepage(page
,
405 trace_reclaim_flags(page
, sync_writeback
));
406 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
414 * Same as remove_mapping, but if the page is removed from the mapping, it
415 * gets returned with a refcount of 0.
417 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
419 BUG_ON(!PageLocked(page
));
420 BUG_ON(mapping
!= page_mapping(page
));
422 spin_lock_irq(&mapping
->tree_lock
);
424 * The non racy check for a busy page.
426 * Must be careful with the order of the tests. When someone has
427 * a ref to the page, it may be possible that they dirty it then
428 * drop the reference. So if PageDirty is tested before page_count
429 * here, then the following race may occur:
431 * get_user_pages(&page);
432 * [user mapping goes away]
434 * !PageDirty(page) [good]
435 * SetPageDirty(page);
437 * !page_count(page) [good, discard it]
439 * [oops, our write_to data is lost]
441 * Reversing the order of the tests ensures such a situation cannot
442 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
443 * load is not satisfied before that of page->_count.
445 * Note that if SetPageDirty is always performed via set_page_dirty,
446 * and thus under tree_lock, then this ordering is not required.
448 if (!page_freeze_refs(page
, 2))
450 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
451 if (unlikely(PageDirty(page
))) {
452 page_unfreeze_refs(page
, 2);
456 if (PageSwapCache(page
)) {
457 swp_entry_t swap
= { .val
= page_private(page
) };
458 __delete_from_swap_cache(page
);
459 spin_unlock_irq(&mapping
->tree_lock
);
460 swapcache_free(swap
, page
);
462 __remove_from_page_cache(page
);
463 spin_unlock_irq(&mapping
->tree_lock
);
464 mem_cgroup_uncharge_cache_page(page
);
470 spin_unlock_irq(&mapping
->tree_lock
);
475 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
476 * someone else has a ref on the page, abort and return 0. If it was
477 * successfully detached, return 1. Assumes the caller has a single ref on
480 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
482 if (__remove_mapping(mapping
, page
)) {
484 * Unfreezing the refcount with 1 rather than 2 effectively
485 * drops the pagecache ref for us without requiring another
488 page_unfreeze_refs(page
, 1);
495 * putback_lru_page - put previously isolated page onto appropriate LRU list
496 * @page: page to be put back to appropriate lru list
498 * Add previously isolated @page to appropriate LRU list.
499 * Page may still be unevictable for other reasons.
501 * lru_lock must not be held, interrupts must be enabled.
503 void putback_lru_page(struct page
*page
)
506 int active
= !!TestClearPageActive(page
);
507 int was_unevictable
= PageUnevictable(page
);
509 VM_BUG_ON(PageLRU(page
));
512 ClearPageUnevictable(page
);
514 if (page_evictable(page
, NULL
)) {
516 * For evictable pages, we can use the cache.
517 * In event of a race, worst case is we end up with an
518 * unevictable page on [in]active list.
519 * We know how to handle that.
521 lru
= active
+ page_lru_base_type(page
);
522 lru_cache_add_lru(page
, lru
);
525 * Put unevictable pages directly on zone's unevictable
528 lru
= LRU_UNEVICTABLE
;
529 add_page_to_unevictable_list(page
);
531 * When racing with an mlock clearing (page is
532 * unlocked), make sure that if the other thread does
533 * not observe our setting of PG_lru and fails
534 * isolation, we see PG_mlocked cleared below and move
535 * the page back to the evictable list.
537 * The other side is TestClearPageMlocked().
543 * page's status can change while we move it among lru. If an evictable
544 * page is on unevictable list, it never be freed. To avoid that,
545 * check after we added it to the list, again.
547 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
, NULL
)) {
548 if (!isolate_lru_page(page
)) {
552 /* This means someone else dropped this page from LRU
553 * So, it will be freed or putback to LRU again. There is
554 * nothing to do here.
558 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
559 count_vm_event(UNEVICTABLE_PGRESCUED
);
560 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
561 count_vm_event(UNEVICTABLE_PGCULLED
);
563 put_page(page
); /* drop ref from isolate */
566 enum page_references
{
568 PAGEREF_RECLAIM_CLEAN
,
573 static enum page_references
page_check_references(struct page
*page
,
574 struct scan_control
*sc
)
576 int referenced_ptes
, referenced_page
;
577 unsigned long vm_flags
;
579 referenced_ptes
= page_referenced(page
, 1, sc
->mem_cgroup
, &vm_flags
);
580 referenced_page
= TestClearPageReferenced(page
);
582 /* Lumpy reclaim - ignore references */
583 if (sc
->lumpy_reclaim_mode
)
584 return PAGEREF_RECLAIM
;
587 * Mlock lost the isolation race with us. Let try_to_unmap()
588 * move the page to the unevictable list.
590 if (vm_flags
& VM_LOCKED
)
591 return PAGEREF_RECLAIM
;
593 if (referenced_ptes
) {
595 return PAGEREF_ACTIVATE
;
597 * All mapped pages start out with page table
598 * references from the instantiating fault, so we need
599 * to look twice if a mapped file page is used more
602 * Mark it and spare it for another trip around the
603 * inactive list. Another page table reference will
604 * lead to its activation.
606 * Note: the mark is set for activated pages as well
607 * so that recently deactivated but used pages are
610 SetPageReferenced(page
);
613 return PAGEREF_ACTIVATE
;
618 /* Reclaim if clean, defer dirty pages to writeback */
620 return PAGEREF_RECLAIM_CLEAN
;
622 return PAGEREF_RECLAIM
;
626 * shrink_page_list() returns the number of reclaimed pages
628 static unsigned long shrink_page_list(struct list_head
*page_list
,
629 struct scan_control
*sc
,
630 enum pageout_io sync_writeback
)
632 LIST_HEAD(ret_pages
);
633 struct pagevec freed_pvec
;
635 unsigned long nr_reclaimed
= 0;
639 pagevec_init(&freed_pvec
, 1);
640 while (!list_empty(page_list
)) {
641 enum page_references references
;
642 struct address_space
*mapping
;
648 page
= lru_to_page(page_list
);
649 list_del(&page
->lru
);
651 if (!trylock_page(page
))
654 VM_BUG_ON(PageActive(page
));
658 if (unlikely(!page_evictable(page
, NULL
)))
661 if (!sc
->may_unmap
&& page_mapped(page
))
664 /* Double the slab pressure for mapped and swapcache pages */
665 if (page_mapped(page
) || PageSwapCache(page
))
668 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
669 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
671 if (PageWriteback(page
)) {
673 * Synchronous reclaim is performed in two passes,
674 * first an asynchronous pass over the list to
675 * start parallel writeback, and a second synchronous
676 * pass to wait for the IO to complete. Wait here
677 * for any page for which writeback has already
680 if (sync_writeback
== PAGEOUT_IO_SYNC
&& may_enter_fs
)
681 wait_on_page_writeback(page
);
686 references
= page_check_references(page
, sc
);
687 switch (references
) {
688 case PAGEREF_ACTIVATE
:
689 goto activate_locked
;
692 case PAGEREF_RECLAIM
:
693 case PAGEREF_RECLAIM_CLEAN
:
694 ; /* try to reclaim the page below */
698 * Anonymous process memory has backing store?
699 * Try to allocate it some swap space here.
701 if (PageAnon(page
) && !PageSwapCache(page
)) {
702 if (!(sc
->gfp_mask
& __GFP_IO
))
704 if (!add_to_swap(page
))
705 goto activate_locked
;
709 mapping
= page_mapping(page
);
712 * The page is mapped into the page tables of one or more
713 * processes. Try to unmap it here.
715 if (page_mapped(page
) && mapping
) {
716 switch (try_to_unmap(page
, TTU_UNMAP
)) {
718 goto activate_locked
;
724 ; /* try to free the page below */
728 if (PageDirty(page
)) {
729 if (references
== PAGEREF_RECLAIM_CLEAN
)
733 if (!sc
->may_writepage
)
736 /* Page is dirty, try to write it out here */
737 switch (pageout(page
, mapping
, sync_writeback
)) {
741 goto activate_locked
;
743 if (PageWriteback(page
) || PageDirty(page
))
746 * A synchronous write - probably a ramdisk. Go
747 * ahead and try to reclaim the page.
749 if (!trylock_page(page
))
751 if (PageDirty(page
) || PageWriteback(page
))
753 mapping
= page_mapping(page
);
755 ; /* try to free the page below */
760 * If the page has buffers, try to free the buffer mappings
761 * associated with this page. If we succeed we try to free
764 * We do this even if the page is PageDirty().
765 * try_to_release_page() does not perform I/O, but it is
766 * possible for a page to have PageDirty set, but it is actually
767 * clean (all its buffers are clean). This happens if the
768 * buffers were written out directly, with submit_bh(). ext3
769 * will do this, as well as the blockdev mapping.
770 * try_to_release_page() will discover that cleanness and will
771 * drop the buffers and mark the page clean - it can be freed.
773 * Rarely, pages can have buffers and no ->mapping. These are
774 * the pages which were not successfully invalidated in
775 * truncate_complete_page(). We try to drop those buffers here
776 * and if that worked, and the page is no longer mapped into
777 * process address space (page_count == 1) it can be freed.
778 * Otherwise, leave the page on the LRU so it is swappable.
780 if (page_has_private(page
)) {
781 if (!try_to_release_page(page
, sc
->gfp_mask
))
782 goto activate_locked
;
783 if (!mapping
&& page_count(page
) == 1) {
785 if (put_page_testzero(page
))
789 * rare race with speculative reference.
790 * the speculative reference will free
791 * this page shortly, so we may
792 * increment nr_reclaimed here (and
793 * leave it off the LRU).
801 if (!mapping
|| !__remove_mapping(mapping
, page
))
805 * At this point, we have no other references and there is
806 * no way to pick any more up (removed from LRU, removed
807 * from pagecache). Can use non-atomic bitops now (and
808 * we obviously don't have to worry about waking up a process
809 * waiting on the page lock, because there are no references.
811 __clear_page_locked(page
);
814 if (!pagevec_add(&freed_pvec
, page
)) {
815 __pagevec_free(&freed_pvec
);
816 pagevec_reinit(&freed_pvec
);
821 if (PageSwapCache(page
))
822 try_to_free_swap(page
);
824 putback_lru_page(page
);
828 /* Not a candidate for swapping, so reclaim swap space. */
829 if (PageSwapCache(page
) && vm_swap_full())
830 try_to_free_swap(page
);
831 VM_BUG_ON(PageActive(page
));
837 list_add(&page
->lru
, &ret_pages
);
838 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
840 list_splice(&ret_pages
, page_list
);
841 if (pagevec_count(&freed_pvec
))
842 __pagevec_free(&freed_pvec
);
843 count_vm_events(PGACTIVATE
, pgactivate
);
848 * Attempt to remove the specified page from its LRU. Only take this page
849 * if it is of the appropriate PageActive status. Pages which are being
850 * freed elsewhere are also ignored.
852 * page: page to consider
853 * mode: one of the LRU isolation modes defined above
855 * returns 0 on success, -ve errno on failure.
857 int __isolate_lru_page(struct page
*page
, int mode
, int file
)
861 /* Only take pages on the LRU. */
866 * When checking the active state, we need to be sure we are
867 * dealing with comparible boolean values. Take the logical not
870 if (mode
!= ISOLATE_BOTH
&& (!PageActive(page
) != !mode
))
873 if (mode
!= ISOLATE_BOTH
&& page_is_file_cache(page
) != file
)
877 * When this function is being called for lumpy reclaim, we
878 * initially look into all LRU pages, active, inactive and
879 * unevictable; only give shrink_page_list evictable pages.
881 if (PageUnevictable(page
))
886 if (likely(get_page_unless_zero(page
))) {
888 * Be careful not to clear PageLRU until after we're
889 * sure the page is not being freed elsewhere -- the
890 * page release code relies on it.
900 * zone->lru_lock is heavily contended. Some of the functions that
901 * shrink the lists perform better by taking out a batch of pages
902 * and working on them outside the LRU lock.
904 * For pagecache intensive workloads, this function is the hottest
905 * spot in the kernel (apart from copy_*_user functions).
907 * Appropriate locks must be held before calling this function.
909 * @nr_to_scan: The number of pages to look through on the list.
910 * @src: The LRU list to pull pages off.
911 * @dst: The temp list to put pages on to.
912 * @scanned: The number of pages that were scanned.
913 * @order: The caller's attempted allocation order
914 * @mode: One of the LRU isolation modes
915 * @file: True [1] if isolating file [!anon] pages
917 * returns how many pages were moved onto *@dst.
919 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
920 struct list_head
*src
, struct list_head
*dst
,
921 unsigned long *scanned
, int order
, int mode
, int file
)
923 unsigned long nr_taken
= 0;
924 unsigned long nr_lumpy_taken
= 0;
925 unsigned long nr_lumpy_dirty
= 0;
926 unsigned long nr_lumpy_failed
= 0;
929 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
932 unsigned long end_pfn
;
933 unsigned long page_pfn
;
936 page
= lru_to_page(src
);
937 prefetchw_prev_lru_page(page
, src
, flags
);
939 VM_BUG_ON(!PageLRU(page
));
941 switch (__isolate_lru_page(page
, mode
, file
)) {
943 list_move(&page
->lru
, dst
);
944 mem_cgroup_del_lru(page
);
949 /* else it is being freed elsewhere */
950 list_move(&page
->lru
, src
);
951 mem_cgroup_rotate_lru_list(page
, page_lru(page
));
962 * Attempt to take all pages in the order aligned region
963 * surrounding the tag page. Only take those pages of
964 * the same active state as that tag page. We may safely
965 * round the target page pfn down to the requested order
966 * as the mem_map is guarenteed valid out to MAX_ORDER,
967 * where that page is in a different zone we will detect
968 * it from its zone id and abort this block scan.
970 zone_id
= page_zone_id(page
);
971 page_pfn
= page_to_pfn(page
);
972 pfn
= page_pfn
& ~((1 << order
) - 1);
973 end_pfn
= pfn
+ (1 << order
);
974 for (; pfn
< end_pfn
; pfn
++) {
975 struct page
*cursor_page
;
977 /* The target page is in the block, ignore it. */
978 if (unlikely(pfn
== page_pfn
))
981 /* Avoid holes within the zone. */
982 if (unlikely(!pfn_valid_within(pfn
)))
985 cursor_page
= pfn_to_page(pfn
);
987 /* Check that we have not crossed a zone boundary. */
988 if (unlikely(page_zone_id(cursor_page
) != zone_id
))
992 * If we don't have enough swap space, reclaiming of
993 * anon page which don't already have a swap slot is
996 if (nr_swap_pages
<= 0 && PageAnon(cursor_page
) &&
997 !PageSwapCache(cursor_page
))
1000 if (__isolate_lru_page(cursor_page
, mode
, file
) == 0) {
1001 list_move(&cursor_page
->lru
, dst
);
1002 mem_cgroup_del_lru(cursor_page
);
1005 if (PageDirty(cursor_page
))
1009 if (mode
== ISOLATE_BOTH
&&
1010 page_count(cursor_page
))
1018 trace_mm_vmscan_lru_isolate(order
,
1021 nr_lumpy_taken
, nr_lumpy_dirty
, nr_lumpy_failed
,
1026 static unsigned long isolate_pages_global(unsigned long nr
,
1027 struct list_head
*dst
,
1028 unsigned long *scanned
, int order
,
1029 int mode
, struct zone
*z
,
1030 int active
, int file
)
1037 return isolate_lru_pages(nr
, &z
->lru
[lru
].list
, dst
, scanned
, order
,
1042 * clear_active_flags() is a helper for shrink_active_list(), clearing
1043 * any active bits from the pages in the list.
1045 static unsigned long clear_active_flags(struct list_head
*page_list
,
1046 unsigned int *count
)
1052 list_for_each_entry(page
, page_list
, lru
) {
1053 lru
= page_lru_base_type(page
);
1054 if (PageActive(page
)) {
1056 ClearPageActive(page
);
1066 * isolate_lru_page - tries to isolate a page from its LRU list
1067 * @page: page to isolate from its LRU list
1069 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1070 * vmstat statistic corresponding to whatever LRU list the page was on.
1072 * Returns 0 if the page was removed from an LRU list.
1073 * Returns -EBUSY if the page was not on an LRU list.
1075 * The returned page will have PageLRU() cleared. If it was found on
1076 * the active list, it will have PageActive set. If it was found on
1077 * the unevictable list, it will have the PageUnevictable bit set. That flag
1078 * may need to be cleared by the caller before letting the page go.
1080 * The vmstat statistic corresponding to the list on which the page was
1081 * found will be decremented.
1084 * (1) Must be called with an elevated refcount on the page. This is a
1085 * fundamentnal difference from isolate_lru_pages (which is called
1086 * without a stable reference).
1087 * (2) the lru_lock must not be held.
1088 * (3) interrupts must be enabled.
1090 int isolate_lru_page(struct page
*page
)
1094 if (PageLRU(page
)) {
1095 struct zone
*zone
= page_zone(page
);
1097 spin_lock_irq(&zone
->lru_lock
);
1098 if (PageLRU(page
) && get_page_unless_zero(page
)) {
1099 int lru
= page_lru(page
);
1103 del_page_from_lru_list(zone
, page
, lru
);
1105 spin_unlock_irq(&zone
->lru_lock
);
1111 * Are there way too many processes in the direct reclaim path already?
1113 static int too_many_isolated(struct zone
*zone
, int file
,
1114 struct scan_control
*sc
)
1116 unsigned long inactive
, isolated
;
1118 if (current_is_kswapd())
1121 if (!scanning_global_lru(sc
))
1125 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1126 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1128 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1129 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1132 return isolated
> inactive
;
1136 * TODO: Try merging with migrations version of putback_lru_pages
1138 static noinline_for_stack
void
1139 putback_lru_pages(struct zone
*zone
, struct zone_reclaim_stat
*reclaim_stat
,
1140 unsigned long nr_anon
, unsigned long nr_file
,
1141 struct list_head
*page_list
)
1144 struct pagevec pvec
;
1146 pagevec_init(&pvec
, 1);
1149 * Put back any unfreeable pages.
1151 spin_lock(&zone
->lru_lock
);
1152 while (!list_empty(page_list
)) {
1154 page
= lru_to_page(page_list
);
1155 VM_BUG_ON(PageLRU(page
));
1156 list_del(&page
->lru
);
1157 if (unlikely(!page_evictable(page
, NULL
))) {
1158 spin_unlock_irq(&zone
->lru_lock
);
1159 putback_lru_page(page
);
1160 spin_lock_irq(&zone
->lru_lock
);
1164 lru
= page_lru(page
);
1165 add_page_to_lru_list(zone
, page
, lru
);
1166 if (is_active_lru(lru
)) {
1167 int file
= is_file_lru(lru
);
1168 reclaim_stat
->recent_rotated
[file
]++;
1170 if (!pagevec_add(&pvec
, page
)) {
1171 spin_unlock_irq(&zone
->lru_lock
);
1172 __pagevec_release(&pvec
);
1173 spin_lock_irq(&zone
->lru_lock
);
1176 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, -nr_anon
);
1177 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -nr_file
);
1179 spin_unlock_irq(&zone
->lru_lock
);
1180 pagevec_release(&pvec
);
1184 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1185 * of reclaimed pages
1187 static noinline_for_stack
unsigned long
1188 shrink_inactive_list(unsigned long nr_to_scan
, struct zone
*zone
,
1189 struct scan_control
*sc
, int priority
, int file
)
1191 LIST_HEAD(page_list
);
1192 unsigned long nr_scanned
;
1193 unsigned long nr_reclaimed
= 0;
1194 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1195 unsigned long nr_taken
;
1196 unsigned long nr_active
;
1197 unsigned int count
[NR_LRU_LISTS
] = { 0, };
1198 unsigned long nr_anon
;
1199 unsigned long nr_file
;
1201 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1202 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1204 /* We are about to die and free our memory. Return now. */
1205 if (fatal_signal_pending(current
))
1206 return SWAP_CLUSTER_MAX
;
1211 spin_lock_irq(&zone
->lru_lock
);
1213 if (scanning_global_lru(sc
)) {
1214 nr_taken
= isolate_pages_global(nr_to_scan
,
1215 &page_list
, &nr_scanned
, sc
->order
,
1216 sc
->lumpy_reclaim_mode
?
1217 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1219 zone
->pages_scanned
+= nr_scanned
;
1220 if (current_is_kswapd())
1221 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
,
1224 __count_zone_vm_events(PGSCAN_DIRECT
, zone
,
1227 nr_taken
= mem_cgroup_isolate_pages(nr_to_scan
,
1228 &page_list
, &nr_scanned
, sc
->order
,
1229 sc
->lumpy_reclaim_mode
?
1230 ISOLATE_BOTH
: ISOLATE_INACTIVE
,
1231 zone
, sc
->mem_cgroup
,
1234 * mem_cgroup_isolate_pages() keeps track of
1235 * scanned pages on its own.
1239 if (nr_taken
== 0) {
1240 spin_unlock_irq(&zone
->lru_lock
);
1244 nr_active
= clear_active_flags(&page_list
, count
);
1245 __count_vm_events(PGDEACTIVATE
, nr_active
);
1247 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
,
1248 -count
[LRU_ACTIVE_FILE
]);
1249 __mod_zone_page_state(zone
, NR_INACTIVE_FILE
,
1250 -count
[LRU_INACTIVE_FILE
]);
1251 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
,
1252 -count
[LRU_ACTIVE_ANON
]);
1253 __mod_zone_page_state(zone
, NR_INACTIVE_ANON
,
1254 -count
[LRU_INACTIVE_ANON
]);
1256 nr_anon
= count
[LRU_ACTIVE_ANON
] + count
[LRU_INACTIVE_ANON
];
1257 nr_file
= count
[LRU_ACTIVE_FILE
] + count
[LRU_INACTIVE_FILE
];
1258 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
, nr_anon
);
1259 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, nr_file
);
1261 reclaim_stat
->recent_scanned
[0] += nr_anon
;
1262 reclaim_stat
->recent_scanned
[1] += nr_file
;
1264 spin_unlock_irq(&zone
->lru_lock
);
1266 nr_reclaimed
= shrink_page_list(&page_list
, sc
, PAGEOUT_IO_ASYNC
);
1269 * If we are direct reclaiming for contiguous pages and we do
1270 * not reclaim everything in the list, try again and wait
1271 * for IO to complete. This will stall high-order allocations
1272 * but that should be acceptable to the caller
1274 if (nr_reclaimed
< nr_taken
&& !current_is_kswapd() &&
1275 sc
->lumpy_reclaim_mode
) {
1276 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1279 * The attempt at page out may have made some
1280 * of the pages active, mark them inactive again.
1282 nr_active
= clear_active_flags(&page_list
, count
);
1283 count_vm_events(PGDEACTIVATE
, nr_active
);
1285 nr_reclaimed
+= shrink_page_list(&page_list
, sc
, PAGEOUT_IO_SYNC
);
1288 local_irq_disable();
1289 if (current_is_kswapd())
1290 __count_vm_events(KSWAPD_STEAL
, nr_reclaimed
);
1291 __count_zone_vm_events(PGSTEAL
, zone
, nr_reclaimed
);
1293 putback_lru_pages(zone
, reclaim_stat
, nr_anon
, nr_file
, &page_list
);
1294 return nr_reclaimed
;
1298 * This moves pages from the active list to the inactive list.
1300 * We move them the other way if the page is referenced by one or more
1301 * processes, from rmap.
1303 * If the pages are mostly unmapped, the processing is fast and it is
1304 * appropriate to hold zone->lru_lock across the whole operation. But if
1305 * the pages are mapped, the processing is slow (page_referenced()) so we
1306 * should drop zone->lru_lock around each page. It's impossible to balance
1307 * this, so instead we remove the pages from the LRU while processing them.
1308 * It is safe to rely on PG_active against the non-LRU pages in here because
1309 * nobody will play with that bit on a non-LRU page.
1311 * The downside is that we have to touch page->_count against each page.
1312 * But we had to alter page->flags anyway.
1315 static void move_active_pages_to_lru(struct zone
*zone
,
1316 struct list_head
*list
,
1319 unsigned long pgmoved
= 0;
1320 struct pagevec pvec
;
1323 pagevec_init(&pvec
, 1);
1325 while (!list_empty(list
)) {
1326 page
= lru_to_page(list
);
1328 VM_BUG_ON(PageLRU(page
));
1331 list_move(&page
->lru
, &zone
->lru
[lru
].list
);
1332 mem_cgroup_add_lru_list(page
, lru
);
1335 if (!pagevec_add(&pvec
, page
) || list_empty(list
)) {
1336 spin_unlock_irq(&zone
->lru_lock
);
1337 if (buffer_heads_over_limit
)
1338 pagevec_strip(&pvec
);
1339 __pagevec_release(&pvec
);
1340 spin_lock_irq(&zone
->lru_lock
);
1343 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1344 if (!is_active_lru(lru
))
1345 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1348 static void shrink_active_list(unsigned long nr_pages
, struct zone
*zone
,
1349 struct scan_control
*sc
, int priority
, int file
)
1351 unsigned long nr_taken
;
1352 unsigned long pgscanned
;
1353 unsigned long vm_flags
;
1354 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1355 LIST_HEAD(l_active
);
1356 LIST_HEAD(l_inactive
);
1358 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1359 unsigned long nr_rotated
= 0;
1362 spin_lock_irq(&zone
->lru_lock
);
1363 if (scanning_global_lru(sc
)) {
1364 nr_taken
= isolate_pages_global(nr_pages
, &l_hold
,
1365 &pgscanned
, sc
->order
,
1366 ISOLATE_ACTIVE
, zone
,
1368 zone
->pages_scanned
+= pgscanned
;
1370 nr_taken
= mem_cgroup_isolate_pages(nr_pages
, &l_hold
,
1371 &pgscanned
, sc
->order
,
1372 ISOLATE_ACTIVE
, zone
,
1373 sc
->mem_cgroup
, 1, file
);
1375 * mem_cgroup_isolate_pages() keeps track of
1376 * scanned pages on its own.
1380 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1382 __count_zone_vm_events(PGREFILL
, zone
, pgscanned
);
1384 __mod_zone_page_state(zone
, NR_ACTIVE_FILE
, -nr_taken
);
1386 __mod_zone_page_state(zone
, NR_ACTIVE_ANON
, -nr_taken
);
1387 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1388 spin_unlock_irq(&zone
->lru_lock
);
1390 while (!list_empty(&l_hold
)) {
1392 page
= lru_to_page(&l_hold
);
1393 list_del(&page
->lru
);
1395 if (unlikely(!page_evictable(page
, NULL
))) {
1396 putback_lru_page(page
);
1400 if (page_referenced(page
, 0, sc
->mem_cgroup
, &vm_flags
)) {
1403 * Identify referenced, file-backed active pages and
1404 * give them one more trip around the active list. So
1405 * that executable code get better chances to stay in
1406 * memory under moderate memory pressure. Anon pages
1407 * are not likely to be evicted by use-once streaming
1408 * IO, plus JVM can create lots of anon VM_EXEC pages,
1409 * so we ignore them here.
1411 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1412 list_add(&page
->lru
, &l_active
);
1417 ClearPageActive(page
); /* we are de-activating */
1418 list_add(&page
->lru
, &l_inactive
);
1422 * Move pages back to the lru list.
1424 spin_lock_irq(&zone
->lru_lock
);
1426 * Count referenced pages from currently used mappings as rotated,
1427 * even though only some of them are actually re-activated. This
1428 * helps balance scan pressure between file and anonymous pages in
1431 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1433 move_active_pages_to_lru(zone
, &l_active
,
1434 LRU_ACTIVE
+ file
* LRU_FILE
);
1435 move_active_pages_to_lru(zone
, &l_inactive
,
1436 LRU_BASE
+ file
* LRU_FILE
);
1437 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1438 spin_unlock_irq(&zone
->lru_lock
);
1441 static int inactive_anon_is_low_global(struct zone
*zone
)
1443 unsigned long active
, inactive
;
1445 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1446 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1448 if (inactive
* zone
->inactive_ratio
< active
)
1455 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1456 * @zone: zone to check
1457 * @sc: scan control of this context
1459 * Returns true if the zone does not have enough inactive anon pages,
1460 * meaning some active anon pages need to be deactivated.
1462 static int inactive_anon_is_low(struct zone
*zone
, struct scan_control
*sc
)
1466 if (scanning_global_lru(sc
))
1467 low
= inactive_anon_is_low_global(zone
);
1469 low
= mem_cgroup_inactive_anon_is_low(sc
->mem_cgroup
);
1473 static int inactive_file_is_low_global(struct zone
*zone
)
1475 unsigned long active
, inactive
;
1477 active
= zone_page_state(zone
, NR_ACTIVE_FILE
);
1478 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1480 return (active
> inactive
);
1484 * inactive_file_is_low - check if file pages need to be deactivated
1485 * @zone: zone to check
1486 * @sc: scan control of this context
1488 * When the system is doing streaming IO, memory pressure here
1489 * ensures that active file pages get deactivated, until more
1490 * than half of the file pages are on the inactive list.
1492 * Once we get to that situation, protect the system's working
1493 * set from being evicted by disabling active file page aging.
1495 * This uses a different ratio than the anonymous pages, because
1496 * the page cache uses a use-once replacement algorithm.
1498 static int inactive_file_is_low(struct zone
*zone
, struct scan_control
*sc
)
1502 if (scanning_global_lru(sc
))
1503 low
= inactive_file_is_low_global(zone
);
1505 low
= mem_cgroup_inactive_file_is_low(sc
->mem_cgroup
);
1509 static int inactive_list_is_low(struct zone
*zone
, struct scan_control
*sc
,
1513 return inactive_file_is_low(zone
, sc
);
1515 return inactive_anon_is_low(zone
, sc
);
1518 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1519 struct zone
*zone
, struct scan_control
*sc
, int priority
)
1521 int file
= is_file_lru(lru
);
1523 if (is_active_lru(lru
)) {
1524 if (inactive_list_is_low(zone
, sc
, file
))
1525 shrink_active_list(nr_to_scan
, zone
, sc
, priority
, file
);
1529 return shrink_inactive_list(nr_to_scan
, zone
, sc
, priority
, file
);
1533 * Smallish @nr_to_scan's are deposited in @nr_saved_scan,
1534 * until we collected @swap_cluster_max pages to scan.
1536 static unsigned long nr_scan_try_batch(unsigned long nr_to_scan
,
1537 unsigned long *nr_saved_scan
)
1541 *nr_saved_scan
+= nr_to_scan
;
1542 nr
= *nr_saved_scan
;
1544 if (nr
>= SWAP_CLUSTER_MAX
)
1553 * Determine how aggressively the anon and file LRU lists should be
1554 * scanned. The relative value of each set of LRU lists is determined
1555 * by looking at the fraction of the pages scanned we did rotate back
1556 * onto the active list instead of evict.
1558 * nr[0] = anon pages to scan; nr[1] = file pages to scan
1560 static void get_scan_count(struct zone
*zone
, struct scan_control
*sc
,
1561 unsigned long *nr
, int priority
)
1563 unsigned long anon
, file
, free
;
1564 unsigned long anon_prio
, file_prio
;
1565 unsigned long ap
, fp
;
1566 struct zone_reclaim_stat
*reclaim_stat
= get_reclaim_stat(zone
, sc
);
1567 u64 fraction
[2], denominator
;
1571 /* If we have no swap space, do not bother scanning anon pages. */
1572 if (!sc
->may_swap
|| (nr_swap_pages
<= 0)) {
1580 anon
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_ANON
) +
1581 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_ANON
);
1582 file
= zone_nr_lru_pages(zone
, sc
, LRU_ACTIVE_FILE
) +
1583 zone_nr_lru_pages(zone
, sc
, LRU_INACTIVE_FILE
);
1585 if (scanning_global_lru(sc
)) {
1586 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1587 /* If we have very few page cache pages,
1588 force-scan anon pages. */
1589 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1598 * OK, so we have swap space and a fair amount of page cache
1599 * pages. We use the recently rotated / recently scanned
1600 * ratios to determine how valuable each cache is.
1602 * Because workloads change over time (and to avoid overflow)
1603 * we keep these statistics as a floating average, which ends
1604 * up weighing recent references more than old ones.
1606 * anon in [0], file in [1]
1608 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1609 spin_lock_irq(&zone
->lru_lock
);
1610 reclaim_stat
->recent_scanned
[0] /= 2;
1611 reclaim_stat
->recent_rotated
[0] /= 2;
1612 spin_unlock_irq(&zone
->lru_lock
);
1615 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1616 spin_lock_irq(&zone
->lru_lock
);
1617 reclaim_stat
->recent_scanned
[1] /= 2;
1618 reclaim_stat
->recent_rotated
[1] /= 2;
1619 spin_unlock_irq(&zone
->lru_lock
);
1623 * With swappiness at 100, anonymous and file have the same priority.
1624 * This scanning priority is essentially the inverse of IO cost.
1626 anon_prio
= sc
->swappiness
;
1627 file_prio
= 200 - sc
->swappiness
;
1630 * The amount of pressure on anon vs file pages is inversely
1631 * proportional to the fraction of recently scanned pages on
1632 * each list that were recently referenced and in active use.
1634 ap
= (anon_prio
+ 1) * (reclaim_stat
->recent_scanned
[0] + 1);
1635 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1637 fp
= (file_prio
+ 1) * (reclaim_stat
->recent_scanned
[1] + 1);
1638 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1642 denominator
= ap
+ fp
+ 1;
1644 for_each_evictable_lru(l
) {
1645 int file
= is_file_lru(l
);
1648 scan
= zone_nr_lru_pages(zone
, sc
, l
);
1649 if (priority
|| noswap
) {
1651 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1653 nr
[l
] = nr_scan_try_batch(scan
,
1654 &reclaim_stat
->nr_saved_scan
[l
]);
1658 static void set_lumpy_reclaim_mode(int priority
, struct scan_control
*sc
)
1661 * If we need a large contiguous chunk of memory, or have
1662 * trouble getting a small set of contiguous pages, we
1663 * will reclaim both active and inactive pages.
1665 if (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
)
1666 sc
->lumpy_reclaim_mode
= 1;
1667 else if (sc
->order
&& priority
< DEF_PRIORITY
- 2)
1668 sc
->lumpy_reclaim_mode
= 1;
1670 sc
->lumpy_reclaim_mode
= 0;
1674 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1676 static void shrink_zone(int priority
, struct zone
*zone
,
1677 struct scan_control
*sc
)
1679 unsigned long nr
[NR_LRU_LISTS
];
1680 unsigned long nr_to_scan
;
1682 unsigned long nr_reclaimed
= sc
->nr_reclaimed
;
1683 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1685 get_scan_count(zone
, sc
, nr
, priority
);
1687 set_lumpy_reclaim_mode(priority
, sc
);
1689 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1690 nr
[LRU_INACTIVE_FILE
]) {
1691 for_each_evictable_lru(l
) {
1693 nr_to_scan
= min_t(unsigned long,
1694 nr
[l
], SWAP_CLUSTER_MAX
);
1695 nr
[l
] -= nr_to_scan
;
1697 nr_reclaimed
+= shrink_list(l
, nr_to_scan
,
1698 zone
, sc
, priority
);
1702 * On large memory systems, scan >> priority can become
1703 * really large. This is fine for the starting priority;
1704 * we want to put equal scanning pressure on each zone.
1705 * However, if the VM has a harder time of freeing pages,
1706 * with multiple processes reclaiming pages, the total
1707 * freeing target can get unreasonably large.
1709 if (nr_reclaimed
>= nr_to_reclaim
&& priority
< DEF_PRIORITY
)
1713 sc
->nr_reclaimed
= nr_reclaimed
;
1716 * Even if we did not try to evict anon pages at all, we want to
1717 * rebalance the anon lru active/inactive ratio.
1719 if (inactive_anon_is_low(zone
, sc
) && nr_swap_pages
> 0)
1720 shrink_active_list(SWAP_CLUSTER_MAX
, zone
, sc
, priority
, 0);
1722 throttle_vm_writeout(sc
->gfp_mask
);
1726 * This is the direct reclaim path, for page-allocating processes. We only
1727 * try to reclaim pages from zones which will satisfy the caller's allocation
1730 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
1732 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
1734 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
1735 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
1736 * zone defense algorithm.
1738 * If a zone is deemed to be full of pinned pages then just give it a light
1739 * scan then give up on it.
1741 static bool shrink_zones(int priority
, struct zonelist
*zonelist
,
1742 struct scan_control
*sc
)
1746 bool all_unreclaimable
= true;
1748 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
1749 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
1750 if (!populated_zone(zone
))
1753 * Take care memory controller reclaiming has small influence
1756 if (scanning_global_lru(sc
)) {
1757 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1759 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
1760 continue; /* Let kswapd poll it */
1763 shrink_zone(priority
, zone
, sc
);
1764 all_unreclaimable
= false;
1766 return all_unreclaimable
;
1770 * This is the main entry point to direct page reclaim.
1772 * If a full scan of the inactive list fails to free enough memory then we
1773 * are "out of memory" and something needs to be killed.
1775 * If the caller is !__GFP_FS then the probability of a failure is reasonably
1776 * high - the zone may be full of dirty or under-writeback pages, which this
1777 * caller can't do much about. We kick the writeback threads and take explicit
1778 * naps in the hope that some of these pages can be written. But if the
1779 * allocating task holds filesystem locks which prevent writeout this might not
1780 * work, and the allocation attempt will fail.
1782 * returns: 0, if no pages reclaimed
1783 * else, the number of pages reclaimed
1785 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
1786 struct scan_control
*sc
)
1789 bool all_unreclaimable
;
1790 unsigned long total_scanned
= 0;
1791 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
1794 unsigned long writeback_threshold
;
1797 delayacct_freepages_start();
1799 if (scanning_global_lru(sc
))
1800 count_vm_event(ALLOCSTALL
);
1802 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
1805 disable_swap_token();
1806 all_unreclaimable
= shrink_zones(priority
, zonelist
, sc
);
1808 * Don't shrink slabs when reclaiming memory from
1809 * over limit cgroups
1811 if (scanning_global_lru(sc
)) {
1812 unsigned long lru_pages
= 0;
1813 for_each_zone_zonelist(zone
, z
, zonelist
,
1814 gfp_zone(sc
->gfp_mask
)) {
1815 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
1818 lru_pages
+= zone_reclaimable_pages(zone
);
1821 shrink_slab(sc
->nr_scanned
, sc
->gfp_mask
, lru_pages
);
1822 if (reclaim_state
) {
1823 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
1824 reclaim_state
->reclaimed_slab
= 0;
1827 total_scanned
+= sc
->nr_scanned
;
1828 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
1832 * Try to write back as many pages as we just scanned. This
1833 * tends to cause slow streaming writers to write data to the
1834 * disk smoothly, at the dirtying rate, which is nice. But
1835 * that's undesirable in laptop mode, where we *want* lumpy
1836 * writeout. So in laptop mode, write out the whole world.
1838 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
1839 if (total_scanned
> writeback_threshold
) {
1840 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
);
1841 sc
->may_writepage
= 1;
1844 /* Take a nap, wait for some writeback to complete */
1845 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
1846 priority
< DEF_PRIORITY
- 2)
1847 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1852 * Now that we've scanned all the zones at this priority level, note
1853 * that level within the zone so that the next thread which performs
1854 * scanning of this zone will immediately start out at this priority
1855 * level. This affects only the decision whether or not to bring
1856 * mapped pages onto the inactive list.
1861 delayacct_freepages_end();
1864 if (sc
->nr_reclaimed
)
1865 return sc
->nr_reclaimed
;
1867 /* top priority shrink_zones still had more to do? don't OOM, then */
1868 if (scanning_global_lru(sc
) && !all_unreclaimable
)
1874 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
1875 gfp_t gfp_mask
, nodemask_t
*nodemask
)
1877 unsigned long nr_reclaimed
;
1878 struct scan_control sc
= {
1879 .gfp_mask
= gfp_mask
,
1880 .may_writepage
= !laptop_mode
,
1881 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
1884 .swappiness
= vm_swappiness
,
1887 .nodemask
= nodemask
,
1890 trace_mm_vmscan_direct_reclaim_begin(order
,
1894 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
1896 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
1898 return nr_reclaimed
;
1901 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1903 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*mem
,
1904 gfp_t gfp_mask
, bool noswap
,
1905 unsigned int swappiness
,
1906 struct zone
*zone
, int nid
)
1908 struct scan_control sc
= {
1909 .may_writepage
= !laptop_mode
,
1911 .may_swap
= !noswap
,
1912 .swappiness
= swappiness
,
1916 nodemask_t nm
= nodemask_of_node(nid
);
1918 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1919 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1921 sc
.nr_reclaimed
= 0;
1924 * NOTE: Although we can get the priority field, using it
1925 * here is not a good idea, since it limits the pages we can scan.
1926 * if we don't reclaim here, the shrink_zone from balance_pgdat
1927 * will pick up pages from other mem cgroup's as well. We hack
1928 * the priority and make it zero.
1930 shrink_zone(0, zone
, &sc
);
1931 return sc
.nr_reclaimed
;
1934 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*mem_cont
,
1937 unsigned int swappiness
)
1939 struct zonelist
*zonelist
;
1940 struct scan_control sc
= {
1941 .may_writepage
= !laptop_mode
,
1943 .may_swap
= !noswap
,
1944 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
1945 .swappiness
= swappiness
,
1947 .mem_cgroup
= mem_cont
,
1948 .nodemask
= NULL
, /* we don't care the placement */
1951 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
1952 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
1953 zonelist
= NODE_DATA(numa_node_id())->node_zonelists
;
1954 return do_try_to_free_pages(zonelist
, &sc
);
1958 /* is kswapd sleeping prematurely? */
1959 static int sleeping_prematurely(pg_data_t
*pgdat
, int order
, long remaining
)
1963 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
1967 /* If after HZ/10, a zone is below the high mark, it's premature */
1968 for (i
= 0; i
< pgdat
->nr_zones
; i
++) {
1969 struct zone
*zone
= pgdat
->node_zones
+ i
;
1971 if (!populated_zone(zone
))
1974 if (zone
->all_unreclaimable
)
1977 if (!zone_watermark_ok(zone
, order
, high_wmark_pages(zone
),
1986 * For kswapd, balance_pgdat() will work across all this node's zones until
1987 * they are all at high_wmark_pages(zone).
1989 * Returns the number of pages which were actually freed.
1991 * There is special handling here for zones which are full of pinned pages.
1992 * This can happen if the pages are all mlocked, or if they are all used by
1993 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
1994 * What we do is to detect the case where all pages in the zone have been
1995 * scanned twice and there has been zero successful reclaim. Mark the zone as
1996 * dead and from now on, only perform a short scan. Basically we're polling
1997 * the zone for when the problem goes away.
1999 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2000 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2001 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2002 * lower zones regardless of the number of free pages in the lower zones. This
2003 * interoperates with the page allocator fallback scheme to ensure that aging
2004 * of pages is balanced across the zones.
2006 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
)
2011 unsigned long total_scanned
;
2012 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2013 struct scan_control sc
= {
2014 .gfp_mask
= GFP_KERNEL
,
2018 * kswapd doesn't want to be bailed out while reclaim. because
2019 * we want to put equal scanning pressure on each zone.
2021 .nr_to_reclaim
= ULONG_MAX
,
2022 .swappiness
= vm_swappiness
,
2028 sc
.nr_reclaimed
= 0;
2029 sc
.may_writepage
= !laptop_mode
;
2030 count_vm_event(PAGEOUTRUN
);
2032 for (priority
= DEF_PRIORITY
; priority
>= 0; priority
--) {
2033 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2034 unsigned long lru_pages
= 0;
2035 int has_under_min_watermark_zone
= 0;
2037 /* The swap token gets in the way of swapout... */
2039 disable_swap_token();
2044 * Scan in the highmem->dma direction for the highest
2045 * zone which needs scanning
2047 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2048 struct zone
*zone
= pgdat
->node_zones
+ i
;
2050 if (!populated_zone(zone
))
2053 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2057 * Do some background aging of the anon list, to give
2058 * pages a chance to be referenced before reclaiming.
2060 if (inactive_anon_is_low(zone
, &sc
))
2061 shrink_active_list(SWAP_CLUSTER_MAX
, zone
,
2064 if (!zone_watermark_ok(zone
, order
,
2065 high_wmark_pages(zone
), 0, 0)) {
2073 for (i
= 0; i
<= end_zone
; i
++) {
2074 struct zone
*zone
= pgdat
->node_zones
+ i
;
2076 lru_pages
+= zone_reclaimable_pages(zone
);
2080 * Now scan the zone in the dma->highmem direction, stopping
2081 * at the last zone which needs scanning.
2083 * We do this because the page allocator works in the opposite
2084 * direction. This prevents the page allocator from allocating
2085 * pages behind kswapd's direction of progress, which would
2086 * cause too much scanning of the lower zones.
2088 for (i
= 0; i
<= end_zone
; i
++) {
2089 struct zone
*zone
= pgdat
->node_zones
+ i
;
2093 if (!populated_zone(zone
))
2096 if (zone
->all_unreclaimable
&& priority
!= DEF_PRIORITY
)
2101 nid
= pgdat
->node_id
;
2102 zid
= zone_idx(zone
);
2104 * Call soft limit reclaim before calling shrink_zone.
2105 * For now we ignore the return value
2107 mem_cgroup_soft_limit_reclaim(zone
, order
, sc
.gfp_mask
,
2110 * We put equal pressure on every zone, unless one
2111 * zone has way too many pages free already.
2113 if (!zone_watermark_ok(zone
, order
,
2114 8*high_wmark_pages(zone
), end_zone
, 0))
2115 shrink_zone(priority
, zone
, &sc
);
2116 reclaim_state
->reclaimed_slab
= 0;
2117 nr_slab
= shrink_slab(sc
.nr_scanned
, GFP_KERNEL
,
2119 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2120 total_scanned
+= sc
.nr_scanned
;
2121 if (zone
->all_unreclaimable
)
2124 zone
->pages_scanned
>= (zone_reclaimable_pages(zone
) * 6))
2125 zone
->all_unreclaimable
= 1;
2127 * If we've done a decent amount of scanning and
2128 * the reclaim ratio is low, start doing writepage
2129 * even in laptop mode
2131 if (total_scanned
> SWAP_CLUSTER_MAX
* 2 &&
2132 total_scanned
> sc
.nr_reclaimed
+ sc
.nr_reclaimed
/ 2)
2133 sc
.may_writepage
= 1;
2135 if (!zone_watermark_ok(zone
, order
,
2136 high_wmark_pages(zone
), end_zone
, 0)) {
2139 * We are still under min water mark. This
2140 * means that we have a GFP_ATOMIC allocation
2141 * failure risk. Hurry up!
2143 if (!zone_watermark_ok(zone
, order
,
2144 min_wmark_pages(zone
), end_zone
, 0))
2145 has_under_min_watermark_zone
= 1;
2150 break; /* kswapd: all done */
2152 * OK, kswapd is getting into trouble. Take a nap, then take
2153 * another pass across the zones.
2155 if (total_scanned
&& (priority
< DEF_PRIORITY
- 2)) {
2156 if (has_under_min_watermark_zone
)
2157 count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT
);
2159 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2163 * We do this so kswapd doesn't build up large priorities for
2164 * example when it is freeing in parallel with allocators. It
2165 * matches the direct reclaim path behaviour in terms of impact
2166 * on zone->*_priority.
2168 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2172 if (!all_zones_ok
) {
2178 * Fragmentation may mean that the system cannot be
2179 * rebalanced for high-order allocations in all zones.
2180 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2181 * it means the zones have been fully scanned and are still
2182 * not balanced. For high-order allocations, there is
2183 * little point trying all over again as kswapd may
2186 * Instead, recheck all watermarks at order-0 as they
2187 * are the most important. If watermarks are ok, kswapd will go
2188 * back to sleep. High-order users can still perform direct
2189 * reclaim if they wish.
2191 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2192 order
= sc
.order
= 0;
2197 return sc
.nr_reclaimed
;
2201 * The background pageout daemon, started as a kernel thread
2202 * from the init process.
2204 * This basically trickles out pages so that we have _some_
2205 * free memory available even if there is no other activity
2206 * that frees anything up. This is needed for things like routing
2207 * etc, where we otherwise might have all activity going on in
2208 * asynchronous contexts that cannot page things out.
2210 * If there are applications that are active memory-allocators
2211 * (most normal use), this basically shouldn't matter.
2213 static int kswapd(void *p
)
2215 unsigned long order
;
2216 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2217 struct task_struct
*tsk
= current
;
2219 struct reclaim_state reclaim_state
= {
2220 .reclaimed_slab
= 0,
2222 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2224 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2226 if (!cpumask_empty(cpumask
))
2227 set_cpus_allowed_ptr(tsk
, cpumask
);
2228 current
->reclaim_state
= &reclaim_state
;
2231 * Tell the memory management that we're a "memory allocator",
2232 * and that if we need more memory we should get access to it
2233 * regardless (see "__alloc_pages()"). "kswapd" should
2234 * never get caught in the normal page freeing logic.
2236 * (Kswapd normally doesn't need memory anyway, but sometimes
2237 * you need a small amount of memory in order to be able to
2238 * page out something else, and this flag essentially protects
2239 * us from recursively trying to free more memory as we're
2240 * trying to free the first piece of memory in the first place).
2242 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
2247 unsigned long new_order
;
2250 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2251 new_order
= pgdat
->kswapd_max_order
;
2252 pgdat
->kswapd_max_order
= 0;
2253 if (order
< new_order
) {
2255 * Don't sleep if someone wants a larger 'order'
2260 if (!freezing(current
) && !kthread_should_stop()) {
2263 /* Try to sleep for a short interval */
2264 if (!sleeping_prematurely(pgdat
, order
, remaining
)) {
2265 remaining
= schedule_timeout(HZ
/10);
2266 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2267 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2271 * After a short sleep, check if it was a
2272 * premature sleep. If not, then go fully
2273 * to sleep until explicitly woken up
2275 if (!sleeping_prematurely(pgdat
, order
, remaining
)) {
2276 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2280 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2282 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2286 order
= pgdat
->kswapd_max_order
;
2288 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2290 ret
= try_to_freeze();
2291 if (kthread_should_stop())
2295 * We can speed up thawing tasks if we don't call balance_pgdat
2296 * after returning from the refrigerator
2299 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
2300 balance_pgdat(pgdat
, order
);
2307 * A zone is low on free memory, so wake its kswapd task to service it.
2309 void wakeup_kswapd(struct zone
*zone
, int order
)
2313 if (!populated_zone(zone
))
2316 pgdat
= zone
->zone_pgdat
;
2317 if (zone_watermark_ok(zone
, order
, low_wmark_pages(zone
), 0, 0))
2319 if (pgdat
->kswapd_max_order
< order
)
2320 pgdat
->kswapd_max_order
= order
;
2321 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
2322 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2324 if (!waitqueue_active(&pgdat
->kswapd_wait
))
2326 wake_up_interruptible(&pgdat
->kswapd_wait
);
2330 * The reclaimable count would be mostly accurate.
2331 * The less reclaimable pages may be
2332 * - mlocked pages, which will be moved to unevictable list when encountered
2333 * - mapped pages, which may require several travels to be reclaimed
2334 * - dirty pages, which is not "instantly" reclaimable
2336 unsigned long global_reclaimable_pages(void)
2340 nr
= global_page_state(NR_ACTIVE_FILE
) +
2341 global_page_state(NR_INACTIVE_FILE
);
2343 if (nr_swap_pages
> 0)
2344 nr
+= global_page_state(NR_ACTIVE_ANON
) +
2345 global_page_state(NR_INACTIVE_ANON
);
2350 unsigned long zone_reclaimable_pages(struct zone
*zone
)
2354 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2355 zone_page_state(zone
, NR_INACTIVE_FILE
);
2357 if (nr_swap_pages
> 0)
2358 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2359 zone_page_state(zone
, NR_INACTIVE_ANON
);
2364 #ifdef CONFIG_HIBERNATION
2366 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
2369 * Rather than trying to age LRUs the aim is to preserve the overall
2370 * LRU order by reclaiming preferentially
2371 * inactive > active > active referenced > active mapped
2373 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
2375 struct reclaim_state reclaim_state
;
2376 struct scan_control sc
= {
2377 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
2381 .nr_to_reclaim
= nr_to_reclaim
,
2382 .hibernation_mode
= 1,
2383 .swappiness
= vm_swappiness
,
2386 struct zonelist
* zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
2387 struct task_struct
*p
= current
;
2388 unsigned long nr_reclaimed
;
2390 p
->flags
|= PF_MEMALLOC
;
2391 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
2392 reclaim_state
.reclaimed_slab
= 0;
2393 p
->reclaim_state
= &reclaim_state
;
2395 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
2397 p
->reclaim_state
= NULL
;
2398 lockdep_clear_current_reclaim_state();
2399 p
->flags
&= ~PF_MEMALLOC
;
2401 return nr_reclaimed
;
2403 #endif /* CONFIG_HIBERNATION */
2405 /* It's optimal to keep kswapds on the same CPUs as their memory, but
2406 not required for correctness. So if the last cpu in a node goes
2407 away, we get changed to run anywhere: as the first one comes back,
2408 restore their cpu bindings. */
2409 static int __devinit
cpu_callback(struct notifier_block
*nfb
,
2410 unsigned long action
, void *hcpu
)
2414 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
2415 for_each_node_state(nid
, N_HIGH_MEMORY
) {
2416 pg_data_t
*pgdat
= NODE_DATA(nid
);
2417 const struct cpumask
*mask
;
2419 mask
= cpumask_of_node(pgdat
->node_id
);
2421 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
2422 /* One of our CPUs online: restore mask */
2423 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
2430 * This kswapd start function will be called by init and node-hot-add.
2431 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
2433 int kswapd_run(int nid
)
2435 pg_data_t
*pgdat
= NODE_DATA(nid
);
2441 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
2442 if (IS_ERR(pgdat
->kswapd
)) {
2443 /* failure at boot is fatal */
2444 BUG_ON(system_state
== SYSTEM_BOOTING
);
2445 printk("Failed to start kswapd on node %d\n",nid
);
2452 * Called by memory hotplug when all memory in a node is offlined.
2454 void kswapd_stop(int nid
)
2456 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
2459 kthread_stop(kswapd
);
2462 static int __init
kswapd_init(void)
2467 for_each_node_state(nid
, N_HIGH_MEMORY
)
2469 hotcpu_notifier(cpu_callback
, 0);
2473 module_init(kswapd_init
)
2479 * If non-zero call zone_reclaim when the number of free pages falls below
2482 int zone_reclaim_mode __read_mostly
;
2484 #define RECLAIM_OFF 0
2485 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
2486 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
2487 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
2490 * Priority for ZONE_RECLAIM. This determines the fraction of pages
2491 * of a node considered for each zone_reclaim. 4 scans 1/16th of
2494 #define ZONE_RECLAIM_PRIORITY 4
2497 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
2500 int sysctl_min_unmapped_ratio
= 1;
2503 * If the number of slab pages in a zone grows beyond this percentage then
2504 * slab reclaim needs to occur.
2506 int sysctl_min_slab_ratio
= 5;
2508 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
2510 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
2511 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
2512 zone_page_state(zone
, NR_ACTIVE_FILE
);
2515 * It's possible for there to be more file mapped pages than
2516 * accounted for by the pages on the file LRU lists because
2517 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
2519 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
2522 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
2523 static long zone_pagecache_reclaimable(struct zone
*zone
)
2525 long nr_pagecache_reclaimable
;
2529 * If RECLAIM_SWAP is set, then all file pages are considered
2530 * potentially reclaimable. Otherwise, we have to worry about
2531 * pages like swapcache and zone_unmapped_file_pages() provides
2534 if (zone_reclaim_mode
& RECLAIM_SWAP
)
2535 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
2537 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
2539 /* If we can't clean pages, remove dirty pages from consideration */
2540 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
2541 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
2543 /* Watch for any possible underflows due to delta */
2544 if (unlikely(delta
> nr_pagecache_reclaimable
))
2545 delta
= nr_pagecache_reclaimable
;
2547 return nr_pagecache_reclaimable
- delta
;
2551 * Try to free up some pages from this zone through reclaim.
2553 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2555 /* Minimum pages needed in order to stay on node */
2556 const unsigned long nr_pages
= 1 << order
;
2557 struct task_struct
*p
= current
;
2558 struct reclaim_state reclaim_state
;
2560 struct scan_control sc
= {
2561 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
2562 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
2564 .nr_to_reclaim
= max_t(unsigned long, nr_pages
,
2566 .gfp_mask
= gfp_mask
,
2567 .swappiness
= vm_swappiness
,
2570 unsigned long slab_reclaimable
;
2574 * We need to be able to allocate from the reserves for RECLAIM_SWAP
2575 * and we also need to be able to write out pages for RECLAIM_WRITE
2578 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
2579 lockdep_set_current_reclaim_state(gfp_mask
);
2580 reclaim_state
.reclaimed_slab
= 0;
2581 p
->reclaim_state
= &reclaim_state
;
2583 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
2585 * Free memory by calling shrink zone with increasing
2586 * priorities until we have enough memory freed.
2588 priority
= ZONE_RECLAIM_PRIORITY
;
2590 shrink_zone(priority
, zone
, &sc
);
2592 } while (priority
>= 0 && sc
.nr_reclaimed
< nr_pages
);
2595 slab_reclaimable
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2596 if (slab_reclaimable
> zone
->min_slab_pages
) {
2598 * shrink_slab() does not currently allow us to determine how
2599 * many pages were freed in this zone. So we take the current
2600 * number of slab pages and shake the slab until it is reduced
2601 * by the same nr_pages that we used for reclaiming unmapped
2604 * Note that shrink_slab will free memory on all zones and may
2607 while (shrink_slab(sc
.nr_scanned
, gfp_mask
, order
) &&
2608 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) >
2609 slab_reclaimable
- nr_pages
)
2613 * Update nr_reclaimed by the number of slab pages we
2614 * reclaimed from this zone.
2616 sc
.nr_reclaimed
+= slab_reclaimable
-
2617 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
2620 p
->reclaim_state
= NULL
;
2621 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
2622 lockdep_clear_current_reclaim_state();
2623 return sc
.nr_reclaimed
>= nr_pages
;
2626 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
2632 * Zone reclaim reclaims unmapped file backed pages and
2633 * slab pages if we are over the defined limits.
2635 * A small portion of unmapped file backed pages is needed for
2636 * file I/O otherwise pages read by file I/O will be immediately
2637 * thrown out if the zone is overallocated. So we do not reclaim
2638 * if less than a specified percentage of the zone is used by
2639 * unmapped file backed pages.
2641 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
2642 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
2643 return ZONE_RECLAIM_FULL
;
2645 if (zone
->all_unreclaimable
)
2646 return ZONE_RECLAIM_FULL
;
2649 * Do not scan if the allocation should not be delayed.
2651 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
2652 return ZONE_RECLAIM_NOSCAN
;
2655 * Only run zone reclaim on the local zone or on zones that do not
2656 * have associated processors. This will favor the local processor
2657 * over remote processors and spread off node memory allocations
2658 * as wide as possible.
2660 node_id
= zone_to_nid(zone
);
2661 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
2662 return ZONE_RECLAIM_NOSCAN
;
2664 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
2665 return ZONE_RECLAIM_NOSCAN
;
2667 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
2668 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
2671 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
2678 * page_evictable - test whether a page is evictable
2679 * @page: the page to test
2680 * @vma: the VMA in which the page is or will be mapped, may be NULL
2682 * Test whether page is evictable--i.e., should be placed on active/inactive
2683 * lists vs unevictable list. The vma argument is !NULL when called from the
2684 * fault path to determine how to instantate a new page.
2686 * Reasons page might not be evictable:
2687 * (1) page's mapping marked unevictable
2688 * (2) page is part of an mlocked VMA
2691 int page_evictable(struct page
*page
, struct vm_area_struct
*vma
)
2694 if (mapping_unevictable(page_mapping(page
)))
2697 if (PageMlocked(page
) || (vma
&& is_mlocked_vma(vma
, page
)))
2704 * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list
2705 * @page: page to check evictability and move to appropriate lru list
2706 * @zone: zone page is in
2708 * Checks a page for evictability and moves the page to the appropriate
2711 * Restrictions: zone->lru_lock must be held, page must be on LRU and must
2712 * have PageUnevictable set.
2714 static void check_move_unevictable_page(struct page
*page
, struct zone
*zone
)
2716 VM_BUG_ON(PageActive(page
));
2719 ClearPageUnevictable(page
);
2720 if (page_evictable(page
, NULL
)) {
2721 enum lru_list l
= page_lru_base_type(page
);
2723 __dec_zone_state(zone
, NR_UNEVICTABLE
);
2724 list_move(&page
->lru
, &zone
->lru
[l
].list
);
2725 mem_cgroup_move_lists(page
, LRU_UNEVICTABLE
, l
);
2726 __inc_zone_state(zone
, NR_INACTIVE_ANON
+ l
);
2727 __count_vm_event(UNEVICTABLE_PGRESCUED
);
2730 * rotate unevictable list
2732 SetPageUnevictable(page
);
2733 list_move(&page
->lru
, &zone
->lru
[LRU_UNEVICTABLE
].list
);
2734 mem_cgroup_rotate_lru_list(page
, LRU_UNEVICTABLE
);
2735 if (page_evictable(page
, NULL
))
2741 * scan_mapping_unevictable_pages - scan an address space for evictable pages
2742 * @mapping: struct address_space to scan for evictable pages
2744 * Scan all pages in mapping. Check unevictable pages for
2745 * evictability and move them to the appropriate zone lru list.
2747 void scan_mapping_unevictable_pages(struct address_space
*mapping
)
2750 pgoff_t end
= (i_size_read(mapping
->host
) + PAGE_CACHE_SIZE
- 1) >>
2753 struct pagevec pvec
;
2755 if (mapping
->nrpages
== 0)
2758 pagevec_init(&pvec
, 0);
2759 while (next
< end
&&
2760 pagevec_lookup(&pvec
, mapping
, next
, PAGEVEC_SIZE
)) {
2766 for (i
= 0; i
< pagevec_count(&pvec
); i
++) {
2767 struct page
*page
= pvec
.pages
[i
];
2768 pgoff_t page_index
= page
->index
;
2769 struct zone
*pagezone
= page_zone(page
);
2772 if (page_index
> next
)
2776 if (pagezone
!= zone
) {
2778 spin_unlock_irq(&zone
->lru_lock
);
2780 spin_lock_irq(&zone
->lru_lock
);
2783 if (PageLRU(page
) && PageUnevictable(page
))
2784 check_move_unevictable_page(page
, zone
);
2787 spin_unlock_irq(&zone
->lru_lock
);
2788 pagevec_release(&pvec
);
2790 count_vm_events(UNEVICTABLE_PGSCANNED
, pg_scanned
);
2796 * scan_zone_unevictable_pages - check unevictable list for evictable pages
2797 * @zone - zone of which to scan the unevictable list
2799 * Scan @zone's unevictable LRU lists to check for pages that have become
2800 * evictable. Move those that have to @zone's inactive list where they
2801 * become candidates for reclaim, unless shrink_inactive_zone() decides
2802 * to reactivate them. Pages that are still unevictable are rotated
2803 * back onto @zone's unevictable list.
2805 #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */
2806 static void scan_zone_unevictable_pages(struct zone
*zone
)
2808 struct list_head
*l_unevictable
= &zone
->lru
[LRU_UNEVICTABLE
].list
;
2810 unsigned long nr_to_scan
= zone_page_state(zone
, NR_UNEVICTABLE
);
2812 while (nr_to_scan
> 0) {
2813 unsigned long batch_size
= min(nr_to_scan
,
2814 SCAN_UNEVICTABLE_BATCH_SIZE
);
2816 spin_lock_irq(&zone
->lru_lock
);
2817 for (scan
= 0; scan
< batch_size
; scan
++) {
2818 struct page
*page
= lru_to_page(l_unevictable
);
2820 if (!trylock_page(page
))
2823 prefetchw_prev_lru_page(page
, l_unevictable
, flags
);
2825 if (likely(PageLRU(page
) && PageUnevictable(page
)))
2826 check_move_unevictable_page(page
, zone
);
2830 spin_unlock_irq(&zone
->lru_lock
);
2832 nr_to_scan
-= batch_size
;
2838 * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages
2840 * A really big hammer: scan all zones' unevictable LRU lists to check for
2841 * pages that have become evictable. Move those back to the zones'
2842 * inactive list where they become candidates for reclaim.
2843 * This occurs when, e.g., we have unswappable pages on the unevictable lists,
2844 * and we add swap to the system. As such, it runs in the context of a task
2845 * that has possibly/probably made some previously unevictable pages
2848 static void scan_all_zones_unevictable_pages(void)
2852 for_each_zone(zone
) {
2853 scan_zone_unevictable_pages(zone
);
2858 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
2859 * all nodes' unevictable lists for evictable pages
2861 unsigned long scan_unevictable_pages
;
2863 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
2864 void __user
*buffer
,
2865 size_t *length
, loff_t
*ppos
)
2867 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
2869 if (write
&& *(unsigned long *)table
->data
)
2870 scan_all_zones_unevictable_pages();
2872 scan_unevictable_pages
= 0;
2877 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
2878 * a specified node's per zone unevictable lists for evictable pages.
2881 static ssize_t
read_scan_unevictable_node(struct sys_device
*dev
,
2882 struct sysdev_attribute
*attr
,
2885 return sprintf(buf
, "0\n"); /* always zero; should fit... */
2888 static ssize_t
write_scan_unevictable_node(struct sys_device
*dev
,
2889 struct sysdev_attribute
*attr
,
2890 const char *buf
, size_t count
)
2892 struct zone
*node_zones
= NODE_DATA(dev
->id
)->node_zones
;
2895 unsigned long req
= strict_strtoul(buf
, 10, &res
);
2898 return 1; /* zero is no-op */
2900 for (zone
= node_zones
; zone
- node_zones
< MAX_NR_ZONES
; ++zone
) {
2901 if (!populated_zone(zone
))
2903 scan_zone_unevictable_pages(zone
);
2909 static SYSDEV_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
2910 read_scan_unevictable_node
,
2911 write_scan_unevictable_node
);
2913 int scan_unevictable_register_node(struct node
*node
)
2915 return sysdev_create_file(&node
->sysdev
, &attr_scan_unevictable_pages
);
2918 void scan_unevictable_unregister_node(struct node
*node
)
2920 sysdev_remove_file(&node
->sysdev
, &attr_scan_unevictable_pages
);