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/vmpressure.h>
23 #include <linux/vmstat.h>
24 #include <linux/file.h>
25 #include <linux/writeback.h>
26 #include <linux/blkdev.h>
27 #include <linux/buffer_head.h> /* for try_to_release_page(),
28 buffer_heads_over_limit */
29 #include <linux/mm_inline.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/compaction.h>
36 #include <linux/notifier.h>
37 #include <linux/rwsem.h>
38 #include <linux/delay.h>
39 #include <linux/kthread.h>
40 #include <linux/freezer.h>
41 #include <linux/memcontrol.h>
42 #include <linux/delayacct.h>
43 #include <linux/sysctl.h>
44 #include <linux/oom.h>
45 #include <linux/prefetch.h>
47 #include <asm/tlbflush.h>
48 #include <asm/div64.h>
50 #include <linux/swapops.h>
51 #include <linux/balloon_compaction.h>
55 #define CREATE_TRACE_POINTS
56 #include <trace/events/vmscan.h>
59 /* Incremented by the number of inactive pages that were scanned */
60 unsigned long nr_scanned
;
62 /* Number of pages freed so far during a call to shrink_zones() */
63 unsigned long nr_reclaimed
;
65 /* How many pages shrink_list() should reclaim */
66 unsigned long nr_to_reclaim
;
68 unsigned long hibernation_mode
;
70 /* This context's GFP mask */
75 /* Can mapped pages be reclaimed? */
78 /* Can pages be swapped as part of reclaim? */
83 /* Scan (total_size >> priority) pages at once */
87 * The memory cgroup that hit its limit and as a result is the
88 * primary target of this reclaim invocation.
90 struct mem_cgroup
*target_mem_cgroup
;
93 * Nodemask of nodes allowed by the caller. If NULL, all nodes
99 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
101 #ifdef ARCH_HAS_PREFETCH
102 #define prefetch_prev_lru_page(_page, _base, _field) \
104 if ((_page)->lru.prev != _base) { \
107 prev = lru_to_page(&(_page->lru)); \
108 prefetch(&prev->_field); \
112 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
115 #ifdef ARCH_HAS_PREFETCHW
116 #define prefetchw_prev_lru_page(_page, _base, _field) \
118 if ((_page)->lru.prev != _base) { \
121 prev = lru_to_page(&(_page->lru)); \
122 prefetchw(&prev->_field); \
126 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
130 * From 0 .. 100. Higher means more swappy.
132 int vm_swappiness
= 60;
133 unsigned long vm_total_pages
; /* The total number of pages which the VM controls */
135 static LIST_HEAD(shrinker_list
);
136 static DECLARE_RWSEM(shrinker_rwsem
);
139 static bool global_reclaim(struct scan_control
*sc
)
141 return !sc
->target_mem_cgroup
;
144 static bool global_reclaim(struct scan_control
*sc
)
150 static unsigned long get_lru_size(struct lruvec
*lruvec
, enum lru_list lru
)
152 if (!mem_cgroup_disabled())
153 return mem_cgroup_get_lru_size(lruvec
, lru
);
155 return zone_page_state(lruvec_zone(lruvec
), NR_LRU_BASE
+ lru
);
159 * Add a shrinker callback to be called from the vm
161 void register_shrinker(struct shrinker
*shrinker
)
163 atomic_long_set(&shrinker
->nr_in_batch
, 0);
164 down_write(&shrinker_rwsem
);
165 list_add_tail(&shrinker
->list
, &shrinker_list
);
166 up_write(&shrinker_rwsem
);
168 EXPORT_SYMBOL(register_shrinker
);
173 void unregister_shrinker(struct shrinker
*shrinker
)
175 down_write(&shrinker_rwsem
);
176 list_del(&shrinker
->list
);
177 up_write(&shrinker_rwsem
);
179 EXPORT_SYMBOL(unregister_shrinker
);
181 static inline int do_shrinker_shrink(struct shrinker
*shrinker
,
182 struct shrink_control
*sc
,
183 unsigned long nr_to_scan
)
185 sc
->nr_to_scan
= nr_to_scan
;
186 return (*shrinker
->shrink
)(shrinker
, sc
);
189 #define SHRINK_BATCH 128
191 * Call the shrink functions to age shrinkable caches
193 * Here we assume it costs one seek to replace a lru page and that it also
194 * takes a seek to recreate a cache object. With this in mind we age equal
195 * percentages of the lru and ageable caches. This should balance the seeks
196 * generated by these structures.
198 * If the vm encountered mapped pages on the LRU it increase the pressure on
199 * slab to avoid swapping.
201 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
203 * `lru_pages' represents the number of on-LRU pages in all the zones which
204 * are eligible for the caller's allocation attempt. It is used for balancing
205 * slab reclaim versus page reclaim.
207 * Returns the number of slab objects which we shrunk.
209 unsigned long shrink_slab(struct shrink_control
*shrink
,
210 unsigned long nr_pages_scanned
,
211 unsigned long lru_pages
)
213 struct shrinker
*shrinker
;
214 unsigned long ret
= 0;
216 if (nr_pages_scanned
== 0)
217 nr_pages_scanned
= SWAP_CLUSTER_MAX
;
219 if (!down_read_trylock(&shrinker_rwsem
)) {
220 /* Assume we'll be able to shrink next time */
225 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
226 unsigned long long delta
;
232 long batch_size
= shrinker
->batch
? shrinker
->batch
235 max_pass
= do_shrinker_shrink(shrinker
, shrink
, 0);
240 * copy the current shrinker scan count into a local variable
241 * and zero it so that other concurrent shrinker invocations
242 * don't also do this scanning work.
244 nr
= atomic_long_xchg(&shrinker
->nr_in_batch
, 0);
247 delta
= (4 * nr_pages_scanned
) / shrinker
->seeks
;
249 do_div(delta
, lru_pages
+ 1);
251 if (total_scan
< 0) {
252 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
254 shrinker
->shrink
, total_scan
);
255 total_scan
= max_pass
;
259 * We need to avoid excessive windup on filesystem shrinkers
260 * due to large numbers of GFP_NOFS allocations causing the
261 * shrinkers to return -1 all the time. This results in a large
262 * nr being built up so when a shrink that can do some work
263 * comes along it empties the entire cache due to nr >>>
264 * max_pass. This is bad for sustaining a working set in
267 * Hence only allow the shrinker to scan the entire cache when
268 * a large delta change is calculated directly.
270 if (delta
< max_pass
/ 4)
271 total_scan
= min(total_scan
, max_pass
/ 2);
274 * Avoid risking looping forever due to too large nr value:
275 * never try to free more than twice the estimate number of
278 if (total_scan
> max_pass
* 2)
279 total_scan
= max_pass
* 2;
281 trace_mm_shrink_slab_start(shrinker
, shrink
, nr
,
282 nr_pages_scanned
, lru_pages
,
283 max_pass
, delta
, total_scan
);
285 while (total_scan
>= batch_size
) {
288 nr_before
= do_shrinker_shrink(shrinker
, shrink
, 0);
289 shrink_ret
= do_shrinker_shrink(shrinker
, shrink
,
291 if (shrink_ret
== -1)
293 if (shrink_ret
< nr_before
)
294 ret
+= nr_before
- shrink_ret
;
295 count_vm_events(SLABS_SCANNED
, batch_size
);
296 total_scan
-= batch_size
;
302 * move the unused scan count back into the shrinker in a
303 * manner that handles concurrent updates. If we exhausted the
304 * scan, there is no need to do an update.
307 new_nr
= atomic_long_add_return(total_scan
,
308 &shrinker
->nr_in_batch
);
310 new_nr
= atomic_long_read(&shrinker
->nr_in_batch
);
312 trace_mm_shrink_slab_end(shrinker
, shrink_ret
, nr
, new_nr
);
314 up_read(&shrinker_rwsem
);
320 static inline int is_page_cache_freeable(struct page
*page
)
323 * A freeable page cache page is referenced only by the caller
324 * that isolated the page, the page cache radix tree and
325 * optional buffer heads at page->private.
327 return page_count(page
) - page_has_private(page
) == 2;
330 static int may_write_to_queue(struct backing_dev_info
*bdi
,
331 struct scan_control
*sc
)
333 if (current
->flags
& PF_SWAPWRITE
)
335 if (!bdi_write_congested(bdi
))
337 if (bdi
== current
->backing_dev_info
)
343 * We detected a synchronous write error writing a page out. Probably
344 * -ENOSPC. We need to propagate that into the address_space for a subsequent
345 * fsync(), msync() or close().
347 * The tricky part is that after writepage we cannot touch the mapping: nothing
348 * prevents it from being freed up. But we have a ref on the page and once
349 * that page is locked, the mapping is pinned.
351 * We're allowed to run sleeping lock_page() here because we know the caller has
354 static void handle_write_error(struct address_space
*mapping
,
355 struct page
*page
, int error
)
358 if (page_mapping(page
) == mapping
)
359 mapping_set_error(mapping
, error
);
363 /* possible outcome of pageout() */
365 /* failed to write page out, page is locked */
367 /* move page to the active list, page is locked */
369 /* page has been sent to the disk successfully, page is unlocked */
371 /* page is clean and locked */
376 * pageout is called by shrink_page_list() for each dirty page.
377 * Calls ->writepage().
379 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
380 struct scan_control
*sc
)
383 * If the page is dirty, only perform writeback if that write
384 * will be non-blocking. To prevent this allocation from being
385 * stalled by pagecache activity. But note that there may be
386 * stalls if we need to run get_block(). We could test
387 * PagePrivate for that.
389 * If this process is currently in __generic_file_aio_write() against
390 * this page's queue, we can perform writeback even if that
393 * If the page is swapcache, write it back even if that would
394 * block, for some throttling. This happens by accident, because
395 * swap_backing_dev_info is bust: it doesn't reflect the
396 * congestion state of the swapdevs. Easy to fix, if needed.
398 if (!is_page_cache_freeable(page
))
402 * Some data journaling orphaned pages can have
403 * page->mapping == NULL while being dirty with clean buffers.
405 if (page_has_private(page
)) {
406 if (try_to_free_buffers(page
)) {
407 ClearPageDirty(page
);
408 printk("%s: orphaned page\n", __func__
);
414 if (mapping
->a_ops
->writepage
== NULL
)
415 return PAGE_ACTIVATE
;
416 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
419 if (clear_page_dirty_for_io(page
)) {
421 struct writeback_control wbc
= {
422 .sync_mode
= WB_SYNC_NONE
,
423 .nr_to_write
= SWAP_CLUSTER_MAX
,
425 .range_end
= LLONG_MAX
,
429 SetPageReclaim(page
);
430 res
= mapping
->a_ops
->writepage(page
, &wbc
);
432 handle_write_error(mapping
, page
, res
);
433 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
434 ClearPageReclaim(page
);
435 return PAGE_ACTIVATE
;
438 if (!PageWriteback(page
)) {
439 /* synchronous write or broken a_ops? */
440 ClearPageReclaim(page
);
442 trace_mm_vmscan_writepage(page
, trace_reclaim_flags(page
));
443 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
451 * Same as remove_mapping, but if the page is removed from the mapping, it
452 * gets returned with a refcount of 0.
454 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
456 BUG_ON(!PageLocked(page
));
457 BUG_ON(mapping
!= page_mapping(page
));
459 spin_lock_irq(&mapping
->tree_lock
);
461 * The non racy check for a busy page.
463 * Must be careful with the order of the tests. When someone has
464 * a ref to the page, it may be possible that they dirty it then
465 * drop the reference. So if PageDirty is tested before page_count
466 * here, then the following race may occur:
468 * get_user_pages(&page);
469 * [user mapping goes away]
471 * !PageDirty(page) [good]
472 * SetPageDirty(page);
474 * !page_count(page) [good, discard it]
476 * [oops, our write_to data is lost]
478 * Reversing the order of the tests ensures such a situation cannot
479 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
480 * load is not satisfied before that of page->_count.
482 * Note that if SetPageDirty is always performed via set_page_dirty,
483 * and thus under tree_lock, then this ordering is not required.
485 if (!page_freeze_refs(page
, 2))
487 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
488 if (unlikely(PageDirty(page
))) {
489 page_unfreeze_refs(page
, 2);
493 if (PageSwapCache(page
)) {
494 swp_entry_t swap
= { .val
= page_private(page
) };
495 __delete_from_swap_cache(page
);
496 spin_unlock_irq(&mapping
->tree_lock
);
497 swapcache_free(swap
, page
);
499 void (*freepage
)(struct page
*);
501 freepage
= mapping
->a_ops
->freepage
;
503 __delete_from_page_cache(page
);
504 spin_unlock_irq(&mapping
->tree_lock
);
505 mem_cgroup_uncharge_cache_page(page
);
507 if (freepage
!= NULL
)
514 spin_unlock_irq(&mapping
->tree_lock
);
519 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
520 * someone else has a ref on the page, abort and return 0. If it was
521 * successfully detached, return 1. Assumes the caller has a single ref on
524 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
526 if (__remove_mapping(mapping
, page
)) {
528 * Unfreezing the refcount with 1 rather than 2 effectively
529 * drops the pagecache ref for us without requiring another
532 page_unfreeze_refs(page
, 1);
539 * putback_lru_page - put previously isolated page onto appropriate LRU list
540 * @page: page to be put back to appropriate lru list
542 * Add previously isolated @page to appropriate LRU list.
543 * Page may still be unevictable for other reasons.
545 * lru_lock must not be held, interrupts must be enabled.
547 void putback_lru_page(struct page
*page
)
550 int active
= !!TestClearPageActive(page
);
551 int was_unevictable
= PageUnevictable(page
);
553 VM_BUG_ON(PageLRU(page
));
556 ClearPageUnevictable(page
);
558 if (page_evictable(page
)) {
560 * For evictable pages, we can use the cache.
561 * In event of a race, worst case is we end up with an
562 * unevictable page on [in]active list.
563 * We know how to handle that.
565 lru
= active
+ page_lru_base_type(page
);
566 lru_cache_add_lru(page
, lru
);
569 * Put unevictable pages directly on zone's unevictable
572 lru
= LRU_UNEVICTABLE
;
573 add_page_to_unevictable_list(page
);
575 * When racing with an mlock or AS_UNEVICTABLE clearing
576 * (page is unlocked) make sure that if the other thread
577 * does not observe our setting of PG_lru and fails
578 * isolation/check_move_unevictable_pages,
579 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
580 * the page back to the evictable list.
582 * The other side is TestClearPageMlocked() or shmem_lock().
588 * page's status can change while we move it among lru. If an evictable
589 * page is on unevictable list, it never be freed. To avoid that,
590 * check after we added it to the list, again.
592 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
)) {
593 if (!isolate_lru_page(page
)) {
597 /* This means someone else dropped this page from LRU
598 * So, it will be freed or putback to LRU again. There is
599 * nothing to do here.
603 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
604 count_vm_event(UNEVICTABLE_PGRESCUED
);
605 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
606 count_vm_event(UNEVICTABLE_PGCULLED
);
608 put_page(page
); /* drop ref from isolate */
611 enum page_references
{
613 PAGEREF_RECLAIM_CLEAN
,
618 static enum page_references
page_check_references(struct page
*page
,
619 struct scan_control
*sc
)
621 int referenced_ptes
, referenced_page
;
622 unsigned long vm_flags
;
624 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
626 referenced_page
= TestClearPageReferenced(page
);
629 * Mlock lost the isolation race with us. Let try_to_unmap()
630 * move the page to the unevictable list.
632 if (vm_flags
& VM_LOCKED
)
633 return PAGEREF_RECLAIM
;
635 if (referenced_ptes
) {
636 if (PageSwapBacked(page
))
637 return PAGEREF_ACTIVATE
;
639 * All mapped pages start out with page table
640 * references from the instantiating fault, so we need
641 * to look twice if a mapped file page is used more
644 * Mark it and spare it for another trip around the
645 * inactive list. Another page table reference will
646 * lead to its activation.
648 * Note: the mark is set for activated pages as well
649 * so that recently deactivated but used pages are
652 SetPageReferenced(page
);
654 if (referenced_page
|| referenced_ptes
> 1)
655 return PAGEREF_ACTIVATE
;
658 * Activate file-backed executable pages after first usage.
660 if (vm_flags
& VM_EXEC
)
661 return PAGEREF_ACTIVATE
;
666 /* Reclaim if clean, defer dirty pages to writeback */
667 if (referenced_page
&& !PageSwapBacked(page
))
668 return PAGEREF_RECLAIM_CLEAN
;
670 return PAGEREF_RECLAIM
;
674 * shrink_page_list() returns the number of reclaimed pages
676 static unsigned long shrink_page_list(struct list_head
*page_list
,
678 struct scan_control
*sc
,
679 enum ttu_flags ttu_flags
,
680 unsigned long *ret_nr_dirty
,
681 unsigned long *ret_nr_writeback
,
684 LIST_HEAD(ret_pages
);
685 LIST_HEAD(free_pages
);
687 unsigned long nr_dirty
= 0;
688 unsigned long nr_congested
= 0;
689 unsigned long nr_reclaimed
= 0;
690 unsigned long nr_writeback
= 0;
694 mem_cgroup_uncharge_start();
695 while (!list_empty(page_list
)) {
696 struct address_space
*mapping
;
699 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
703 page
= lru_to_page(page_list
);
704 list_del(&page
->lru
);
706 if (!trylock_page(page
))
709 VM_BUG_ON(PageActive(page
));
710 VM_BUG_ON(page_zone(page
) != zone
);
714 if (unlikely(!page_evictable(page
)))
717 if (!sc
->may_unmap
&& page_mapped(page
))
720 /* Double the slab pressure for mapped and swapcache pages */
721 if (page_mapped(page
) || PageSwapCache(page
))
724 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
725 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
727 if (PageWriteback(page
)) {
729 * memcg doesn't have any dirty pages throttling so we
730 * could easily OOM just because too many pages are in
731 * writeback and there is nothing else to reclaim.
733 * Check __GFP_IO, certainly because a loop driver
734 * thread might enter reclaim, and deadlock if it waits
735 * on a page for which it is needed to do the write
736 * (loop masks off __GFP_IO|__GFP_FS for this reason);
737 * but more thought would probably show more reasons.
739 * Don't require __GFP_FS, since we're not going into
740 * the FS, just waiting on its writeback completion.
741 * Worryingly, ext4 gfs2 and xfs allocate pages with
742 * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so
743 * testing may_enter_fs here is liable to OOM on them.
745 if (global_reclaim(sc
) ||
746 !PageReclaim(page
) || !(sc
->gfp_mask
& __GFP_IO
)) {
748 * This is slightly racy - end_page_writeback()
749 * might have just cleared PageReclaim, then
750 * setting PageReclaim here end up interpreted
751 * as PageReadahead - but that does not matter
752 * enough to care. What we do want is for this
753 * page to have PageReclaim set next time memcg
754 * reclaim reaches the tests above, so it will
755 * then wait_on_page_writeback() to avoid OOM;
756 * and it's also appropriate in global reclaim.
758 SetPageReclaim(page
);
762 wait_on_page_writeback(page
);
766 references
= page_check_references(page
, sc
);
768 switch (references
) {
769 case PAGEREF_ACTIVATE
:
770 goto activate_locked
;
773 case PAGEREF_RECLAIM
:
774 case PAGEREF_RECLAIM_CLEAN
:
775 ; /* try to reclaim the page below */
779 * Anonymous process memory has backing store?
780 * Try to allocate it some swap space here.
782 if (PageAnon(page
) && !PageSwapCache(page
)) {
783 if (!(sc
->gfp_mask
& __GFP_IO
))
785 if (!add_to_swap(page
, page_list
))
786 goto activate_locked
;
790 mapping
= page_mapping(page
);
793 * The page is mapped into the page tables of one or more
794 * processes. Try to unmap it here.
796 if (page_mapped(page
) && mapping
) {
797 switch (try_to_unmap(page
, ttu_flags
)) {
799 goto activate_locked
;
805 ; /* try to free the page below */
809 if (PageDirty(page
)) {
813 * Only kswapd can writeback filesystem pages to
814 * avoid risk of stack overflow but do not writeback
815 * unless under significant pressure.
817 if (page_is_file_cache(page
) &&
818 (!current_is_kswapd() ||
819 sc
->priority
>= DEF_PRIORITY
- 2)) {
821 * Immediately reclaim when written back.
822 * Similar in principal to deactivate_page()
823 * except we already have the page isolated
824 * and know it's dirty
826 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
827 SetPageReclaim(page
);
832 if (references
== PAGEREF_RECLAIM_CLEAN
)
836 if (!sc
->may_writepage
)
839 /* Page is dirty, try to write it out here */
840 switch (pageout(page
, mapping
, sc
)) {
845 goto activate_locked
;
847 if (PageWriteback(page
))
853 * A synchronous write - probably a ramdisk. Go
854 * ahead and try to reclaim the page.
856 if (!trylock_page(page
))
858 if (PageDirty(page
) || PageWriteback(page
))
860 mapping
= page_mapping(page
);
862 ; /* try to free the page below */
867 * If the page has buffers, try to free the buffer mappings
868 * associated with this page. If we succeed we try to free
871 * We do this even if the page is PageDirty().
872 * try_to_release_page() does not perform I/O, but it is
873 * possible for a page to have PageDirty set, but it is actually
874 * clean (all its buffers are clean). This happens if the
875 * buffers were written out directly, with submit_bh(). ext3
876 * will do this, as well as the blockdev mapping.
877 * try_to_release_page() will discover that cleanness and will
878 * drop the buffers and mark the page clean - it can be freed.
880 * Rarely, pages can have buffers and no ->mapping. These are
881 * the pages which were not successfully invalidated in
882 * truncate_complete_page(). We try to drop those buffers here
883 * and if that worked, and the page is no longer mapped into
884 * process address space (page_count == 1) it can be freed.
885 * Otherwise, leave the page on the LRU so it is swappable.
887 if (page_has_private(page
)) {
888 if (!try_to_release_page(page
, sc
->gfp_mask
))
889 goto activate_locked
;
890 if (!mapping
&& page_count(page
) == 1) {
892 if (put_page_testzero(page
))
896 * rare race with speculative reference.
897 * the speculative reference will free
898 * this page shortly, so we may
899 * increment nr_reclaimed here (and
900 * leave it off the LRU).
908 if (!mapping
|| !__remove_mapping(mapping
, page
))
912 * At this point, we have no other references and there is
913 * no way to pick any more up (removed from LRU, removed
914 * from pagecache). Can use non-atomic bitops now (and
915 * we obviously don't have to worry about waking up a process
916 * waiting on the page lock, because there are no references.
918 __clear_page_locked(page
);
923 * Is there need to periodically free_page_list? It would
924 * appear not as the counts should be low
926 list_add(&page
->lru
, &free_pages
);
930 if (PageSwapCache(page
))
931 try_to_free_swap(page
);
933 putback_lru_page(page
);
937 /* Not a candidate for swapping, so reclaim swap space. */
938 if (PageSwapCache(page
) && vm_swap_full())
939 try_to_free_swap(page
);
940 VM_BUG_ON(PageActive(page
));
946 list_add(&page
->lru
, &ret_pages
);
947 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
951 * Tag a zone as congested if all the dirty pages encountered were
952 * backed by a congested BDI. In this case, reclaimers should just
953 * back off and wait for congestion to clear because further reclaim
954 * will encounter the same problem
956 if (nr_dirty
&& nr_dirty
== nr_congested
&& global_reclaim(sc
))
957 zone_set_flag(zone
, ZONE_CONGESTED
);
959 free_hot_cold_page_list(&free_pages
, 1);
961 list_splice(&ret_pages
, page_list
);
962 count_vm_events(PGACTIVATE
, pgactivate
);
963 mem_cgroup_uncharge_end();
964 *ret_nr_dirty
+= nr_dirty
;
965 *ret_nr_writeback
+= nr_writeback
;
969 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
970 struct list_head
*page_list
)
972 struct scan_control sc
= {
973 .gfp_mask
= GFP_KERNEL
,
974 .priority
= DEF_PRIORITY
,
977 unsigned long ret
, dummy1
, dummy2
;
978 struct page
*page
, *next
;
979 LIST_HEAD(clean_pages
);
981 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
982 if (page_is_file_cache(page
) && !PageDirty(page
) &&
983 !isolated_balloon_page(page
)) {
984 ClearPageActive(page
);
985 list_move(&page
->lru
, &clean_pages
);
989 ret
= shrink_page_list(&clean_pages
, zone
, &sc
,
990 TTU_UNMAP
|TTU_IGNORE_ACCESS
,
991 &dummy1
, &dummy2
, true);
992 list_splice(&clean_pages
, page_list
);
993 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -ret
);
998 * Attempt to remove the specified page from its LRU. Only take this page
999 * if it is of the appropriate PageActive status. Pages which are being
1000 * freed elsewhere are also ignored.
1002 * page: page to consider
1003 * mode: one of the LRU isolation modes defined above
1005 * returns 0 on success, -ve errno on failure.
1007 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1011 /* Only take pages on the LRU. */
1015 /* Compaction should not handle unevictable pages but CMA can do so */
1016 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1022 * To minimise LRU disruption, the caller can indicate that it only
1023 * wants to isolate pages it will be able to operate on without
1024 * blocking - clean pages for the most part.
1026 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1027 * is used by reclaim when it is cannot write to backing storage
1029 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1030 * that it is possible to migrate without blocking
1032 if (mode
& (ISOLATE_CLEAN
|ISOLATE_ASYNC_MIGRATE
)) {
1033 /* All the caller can do on PageWriteback is block */
1034 if (PageWriteback(page
))
1037 if (PageDirty(page
)) {
1038 struct address_space
*mapping
;
1040 /* ISOLATE_CLEAN means only clean pages */
1041 if (mode
& ISOLATE_CLEAN
)
1045 * Only pages without mappings or that have a
1046 * ->migratepage callback are possible to migrate
1049 mapping
= page_mapping(page
);
1050 if (mapping
&& !mapping
->a_ops
->migratepage
)
1055 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1058 if (likely(get_page_unless_zero(page
))) {
1060 * Be careful not to clear PageLRU until after we're
1061 * sure the page is not being freed elsewhere -- the
1062 * page release code relies on it.
1072 * zone->lru_lock is heavily contended. Some of the functions that
1073 * shrink the lists perform better by taking out a batch of pages
1074 * and working on them outside the LRU lock.
1076 * For pagecache intensive workloads, this function is the hottest
1077 * spot in the kernel (apart from copy_*_user functions).
1079 * Appropriate locks must be held before calling this function.
1081 * @nr_to_scan: The number of pages to look through on the list.
1082 * @lruvec: The LRU vector to pull pages from.
1083 * @dst: The temp list to put pages on to.
1084 * @nr_scanned: The number of pages that were scanned.
1085 * @sc: The scan_control struct for this reclaim session
1086 * @mode: One of the LRU isolation modes
1087 * @lru: LRU list id for isolating
1089 * returns how many pages were moved onto *@dst.
1091 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1092 struct lruvec
*lruvec
, struct list_head
*dst
,
1093 unsigned long *nr_scanned
, struct scan_control
*sc
,
1094 isolate_mode_t mode
, enum lru_list lru
)
1096 struct list_head
*src
= &lruvec
->lists
[lru
];
1097 unsigned long nr_taken
= 0;
1100 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1104 page
= lru_to_page(src
);
1105 prefetchw_prev_lru_page(page
, src
, flags
);
1107 VM_BUG_ON(!PageLRU(page
));
1109 switch (__isolate_lru_page(page
, mode
)) {
1111 nr_pages
= hpage_nr_pages(page
);
1112 mem_cgroup_update_lru_size(lruvec
, lru
, -nr_pages
);
1113 list_move(&page
->lru
, dst
);
1114 nr_taken
+= nr_pages
;
1118 /* else it is being freed elsewhere */
1119 list_move(&page
->lru
, src
);
1128 trace_mm_vmscan_lru_isolate(sc
->order
, nr_to_scan
, scan
,
1129 nr_taken
, mode
, is_file_lru(lru
));
1134 * isolate_lru_page - tries to isolate a page from its LRU list
1135 * @page: page to isolate from its LRU list
1137 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1138 * vmstat statistic corresponding to whatever LRU list the page was on.
1140 * Returns 0 if the page was removed from an LRU list.
1141 * Returns -EBUSY if the page was not on an LRU list.
1143 * The returned page will have PageLRU() cleared. If it was found on
1144 * the active list, it will have PageActive set. If it was found on
1145 * the unevictable list, it will have the PageUnevictable bit set. That flag
1146 * may need to be cleared by the caller before letting the page go.
1148 * The vmstat statistic corresponding to the list on which the page was
1149 * found will be decremented.
1152 * (1) Must be called with an elevated refcount on the page. This is a
1153 * fundamentnal difference from isolate_lru_pages (which is called
1154 * without a stable reference).
1155 * (2) the lru_lock must not be held.
1156 * (3) interrupts must be enabled.
1158 int isolate_lru_page(struct page
*page
)
1162 VM_BUG_ON(!page_count(page
));
1164 if (PageLRU(page
)) {
1165 struct zone
*zone
= page_zone(page
);
1166 struct lruvec
*lruvec
;
1168 spin_lock_irq(&zone
->lru_lock
);
1169 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1170 if (PageLRU(page
)) {
1171 int lru
= page_lru(page
);
1174 del_page_from_lru_list(page
, lruvec
, lru
);
1177 spin_unlock_irq(&zone
->lru_lock
);
1183 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1184 * then get resheduled. When there are massive number of tasks doing page
1185 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1186 * the LRU list will go small and be scanned faster than necessary, leading to
1187 * unnecessary swapping, thrashing and OOM.
1189 static int too_many_isolated(struct zone
*zone
, int file
,
1190 struct scan_control
*sc
)
1192 unsigned long inactive
, isolated
;
1194 if (current_is_kswapd())
1197 if (!global_reclaim(sc
))
1201 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1202 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1204 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1205 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1209 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1210 * won't get blocked by normal direct-reclaimers, forming a circular
1213 if ((sc
->gfp_mask
& GFP_IOFS
) == GFP_IOFS
)
1216 return isolated
> inactive
;
1219 static noinline_for_stack
void
1220 putback_inactive_pages(struct lruvec
*lruvec
, struct list_head
*page_list
)
1222 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1223 struct zone
*zone
= lruvec_zone(lruvec
);
1224 LIST_HEAD(pages_to_free
);
1227 * Put back any unfreeable pages.
1229 while (!list_empty(page_list
)) {
1230 struct page
*page
= lru_to_page(page_list
);
1233 VM_BUG_ON(PageLRU(page
));
1234 list_del(&page
->lru
);
1235 if (unlikely(!page_evictable(page
))) {
1236 spin_unlock_irq(&zone
->lru_lock
);
1237 putback_lru_page(page
);
1238 spin_lock_irq(&zone
->lru_lock
);
1242 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1245 lru
= page_lru(page
);
1246 add_page_to_lru_list(page
, lruvec
, lru
);
1248 if (is_active_lru(lru
)) {
1249 int file
= is_file_lru(lru
);
1250 int numpages
= hpage_nr_pages(page
);
1251 reclaim_stat
->recent_rotated
[file
] += numpages
;
1253 if (put_page_testzero(page
)) {
1254 __ClearPageLRU(page
);
1255 __ClearPageActive(page
);
1256 del_page_from_lru_list(page
, lruvec
, lru
);
1258 if (unlikely(PageCompound(page
))) {
1259 spin_unlock_irq(&zone
->lru_lock
);
1260 (*get_compound_page_dtor(page
))(page
);
1261 spin_lock_irq(&zone
->lru_lock
);
1263 list_add(&page
->lru
, &pages_to_free
);
1268 * To save our caller's stack, now use input list for pages to free.
1270 list_splice(&pages_to_free
, page_list
);
1274 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1275 * of reclaimed pages
1277 static noinline_for_stack
unsigned long
1278 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1279 struct scan_control
*sc
, enum lru_list lru
)
1281 LIST_HEAD(page_list
);
1282 unsigned long nr_scanned
;
1283 unsigned long nr_reclaimed
= 0;
1284 unsigned long nr_taken
;
1285 unsigned long nr_dirty
= 0;
1286 unsigned long nr_writeback
= 0;
1287 isolate_mode_t isolate_mode
= 0;
1288 int file
= is_file_lru(lru
);
1289 struct zone
*zone
= lruvec_zone(lruvec
);
1290 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1292 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1293 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1295 /* We are about to die and free our memory. Return now. */
1296 if (fatal_signal_pending(current
))
1297 return SWAP_CLUSTER_MAX
;
1303 isolate_mode
|= ISOLATE_UNMAPPED
;
1304 if (!sc
->may_writepage
)
1305 isolate_mode
|= ISOLATE_CLEAN
;
1307 spin_lock_irq(&zone
->lru_lock
);
1309 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1310 &nr_scanned
, sc
, isolate_mode
, lru
);
1312 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1313 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1315 if (global_reclaim(sc
)) {
1316 zone
->pages_scanned
+= nr_scanned
;
1317 if (current_is_kswapd())
1318 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scanned
);
1320 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scanned
);
1322 spin_unlock_irq(&zone
->lru_lock
);
1327 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, TTU_UNMAP
,
1328 &nr_dirty
, &nr_writeback
, false);
1330 spin_lock_irq(&zone
->lru_lock
);
1332 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1334 if (global_reclaim(sc
)) {
1335 if (current_is_kswapd())
1336 __count_zone_vm_events(PGSTEAL_KSWAPD
, zone
,
1339 __count_zone_vm_events(PGSTEAL_DIRECT
, zone
,
1343 putback_inactive_pages(lruvec
, &page_list
);
1345 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1347 spin_unlock_irq(&zone
->lru_lock
);
1349 free_hot_cold_page_list(&page_list
, 1);
1352 * If reclaim is isolating dirty pages under writeback, it implies
1353 * that the long-lived page allocation rate is exceeding the page
1354 * laundering rate. Either the global limits are not being effective
1355 * at throttling processes due to the page distribution throughout
1356 * zones or there is heavy usage of a slow backing device. The
1357 * only option is to throttle from reclaim context which is not ideal
1358 * as there is no guarantee the dirtying process is throttled in the
1359 * same way balance_dirty_pages() manages.
1361 * This scales the number of dirty pages that must be under writeback
1362 * before throttling depending on priority. It is a simple backoff
1363 * function that has the most effect in the range DEF_PRIORITY to
1364 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1365 * in trouble and reclaim is considered to be in trouble.
1367 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1368 * DEF_PRIORITY-1 50% must be PageWriteback
1369 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1371 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1372 * isolated page is PageWriteback
1374 if (nr_writeback
&& nr_writeback
>=
1375 (nr_taken
>> (DEF_PRIORITY
- sc
->priority
)))
1376 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1378 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1380 nr_scanned
, nr_reclaimed
,
1382 trace_shrink_flags(file
));
1383 return nr_reclaimed
;
1387 * This moves pages from the active list to the inactive list.
1389 * We move them the other way if the page is referenced by one or more
1390 * processes, from rmap.
1392 * If the pages are mostly unmapped, the processing is fast and it is
1393 * appropriate to hold zone->lru_lock across the whole operation. But if
1394 * the pages are mapped, the processing is slow (page_referenced()) so we
1395 * should drop zone->lru_lock around each page. It's impossible to balance
1396 * this, so instead we remove the pages from the LRU while processing them.
1397 * It is safe to rely on PG_active against the non-LRU pages in here because
1398 * nobody will play with that bit on a non-LRU page.
1400 * The downside is that we have to touch page->_count against each page.
1401 * But we had to alter page->flags anyway.
1404 static void move_active_pages_to_lru(struct lruvec
*lruvec
,
1405 struct list_head
*list
,
1406 struct list_head
*pages_to_free
,
1409 struct zone
*zone
= lruvec_zone(lruvec
);
1410 unsigned long pgmoved
= 0;
1414 while (!list_empty(list
)) {
1415 page
= lru_to_page(list
);
1416 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1418 VM_BUG_ON(PageLRU(page
));
1421 nr_pages
= hpage_nr_pages(page
);
1422 mem_cgroup_update_lru_size(lruvec
, lru
, nr_pages
);
1423 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1424 pgmoved
+= nr_pages
;
1426 if (put_page_testzero(page
)) {
1427 __ClearPageLRU(page
);
1428 __ClearPageActive(page
);
1429 del_page_from_lru_list(page
, lruvec
, lru
);
1431 if (unlikely(PageCompound(page
))) {
1432 spin_unlock_irq(&zone
->lru_lock
);
1433 (*get_compound_page_dtor(page
))(page
);
1434 spin_lock_irq(&zone
->lru_lock
);
1436 list_add(&page
->lru
, pages_to_free
);
1439 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1440 if (!is_active_lru(lru
))
1441 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1444 static void shrink_active_list(unsigned long nr_to_scan
,
1445 struct lruvec
*lruvec
,
1446 struct scan_control
*sc
,
1449 unsigned long nr_taken
;
1450 unsigned long nr_scanned
;
1451 unsigned long vm_flags
;
1452 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1453 LIST_HEAD(l_active
);
1454 LIST_HEAD(l_inactive
);
1456 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1457 unsigned long nr_rotated
= 0;
1458 isolate_mode_t isolate_mode
= 0;
1459 int file
= is_file_lru(lru
);
1460 struct zone
*zone
= lruvec_zone(lruvec
);
1465 isolate_mode
|= ISOLATE_UNMAPPED
;
1466 if (!sc
->may_writepage
)
1467 isolate_mode
|= ISOLATE_CLEAN
;
1469 spin_lock_irq(&zone
->lru_lock
);
1471 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
1472 &nr_scanned
, sc
, isolate_mode
, lru
);
1473 if (global_reclaim(sc
))
1474 zone
->pages_scanned
+= nr_scanned
;
1476 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1478 __count_zone_vm_events(PGREFILL
, zone
, nr_scanned
);
1479 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1480 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1481 spin_unlock_irq(&zone
->lru_lock
);
1483 while (!list_empty(&l_hold
)) {
1485 page
= lru_to_page(&l_hold
);
1486 list_del(&page
->lru
);
1488 if (unlikely(!page_evictable(page
))) {
1489 putback_lru_page(page
);
1493 if (unlikely(buffer_heads_over_limit
)) {
1494 if (page_has_private(page
) && trylock_page(page
)) {
1495 if (page_has_private(page
))
1496 try_to_release_page(page
, 0);
1501 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
1503 nr_rotated
+= hpage_nr_pages(page
);
1505 * Identify referenced, file-backed active pages and
1506 * give them one more trip around the active list. So
1507 * that executable code get better chances to stay in
1508 * memory under moderate memory pressure. Anon pages
1509 * are not likely to be evicted by use-once streaming
1510 * IO, plus JVM can create lots of anon VM_EXEC pages,
1511 * so we ignore them here.
1513 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1514 list_add(&page
->lru
, &l_active
);
1519 ClearPageActive(page
); /* we are de-activating */
1520 list_add(&page
->lru
, &l_inactive
);
1524 * Move pages back to the lru list.
1526 spin_lock_irq(&zone
->lru_lock
);
1528 * Count referenced pages from currently used mappings as rotated,
1529 * even though only some of them are actually re-activated. This
1530 * helps balance scan pressure between file and anonymous pages in
1533 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1535 move_active_pages_to_lru(lruvec
, &l_active
, &l_hold
, lru
);
1536 move_active_pages_to_lru(lruvec
, &l_inactive
, &l_hold
, lru
- LRU_ACTIVE
);
1537 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1538 spin_unlock_irq(&zone
->lru_lock
);
1540 free_hot_cold_page_list(&l_hold
, 1);
1544 static int inactive_anon_is_low_global(struct zone
*zone
)
1546 unsigned long active
, inactive
;
1548 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1549 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1551 if (inactive
* zone
->inactive_ratio
< active
)
1558 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1559 * @lruvec: LRU vector to check
1561 * Returns true if the zone does not have enough inactive anon pages,
1562 * meaning some active anon pages need to be deactivated.
1564 static int inactive_anon_is_low(struct lruvec
*lruvec
)
1567 * If we don't have swap space, anonymous page deactivation
1570 if (!total_swap_pages
)
1573 if (!mem_cgroup_disabled())
1574 return mem_cgroup_inactive_anon_is_low(lruvec
);
1576 return inactive_anon_is_low_global(lruvec_zone(lruvec
));
1579 static inline int inactive_anon_is_low(struct lruvec
*lruvec
)
1586 * inactive_file_is_low - check if file pages need to be deactivated
1587 * @lruvec: LRU vector to check
1589 * When the system is doing streaming IO, memory pressure here
1590 * ensures that active file pages get deactivated, until more
1591 * than half of the file pages are on the inactive list.
1593 * Once we get to that situation, protect the system's working
1594 * set from being evicted by disabling active file page aging.
1596 * This uses a different ratio than the anonymous pages, because
1597 * the page cache uses a use-once replacement algorithm.
1599 static int inactive_file_is_low(struct lruvec
*lruvec
)
1601 unsigned long inactive
;
1602 unsigned long active
;
1604 inactive
= get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1605 active
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
);
1607 return active
> inactive
;
1610 static int inactive_list_is_low(struct lruvec
*lruvec
, enum lru_list lru
)
1612 if (is_file_lru(lru
))
1613 return inactive_file_is_low(lruvec
);
1615 return inactive_anon_is_low(lruvec
);
1618 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1619 struct lruvec
*lruvec
, struct scan_control
*sc
)
1621 if (is_active_lru(lru
)) {
1622 if (inactive_list_is_low(lruvec
, lru
))
1623 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
1627 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
1630 static int vmscan_swappiness(struct scan_control
*sc
)
1632 if (global_reclaim(sc
))
1633 return vm_swappiness
;
1634 return mem_cgroup_swappiness(sc
->target_mem_cgroup
);
1645 * Determine how aggressively the anon and file LRU lists should be
1646 * scanned. The relative value of each set of LRU lists is determined
1647 * by looking at the fraction of the pages scanned we did rotate back
1648 * onto the active list instead of evict.
1650 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1651 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1653 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
1656 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1658 u64 denominator
= 0; /* gcc */
1659 struct zone
*zone
= lruvec_zone(lruvec
);
1660 unsigned long anon_prio
, file_prio
;
1661 enum scan_balance scan_balance
;
1662 unsigned long anon
, file
, free
;
1663 bool force_scan
= false;
1664 unsigned long ap
, fp
;
1668 * If the zone or memcg is small, nr[l] can be 0. This
1669 * results in no scanning on this priority and a potential
1670 * priority drop. Global direct reclaim can go to the next
1671 * zone and tends to have no problems. Global kswapd is for
1672 * zone balancing and it needs to scan a minimum amount. When
1673 * reclaiming for a memcg, a priority drop can cause high
1674 * latencies, so it's better to scan a minimum amount there as
1677 if (current_is_kswapd() && zone
->all_unreclaimable
)
1679 if (!global_reclaim(sc
))
1682 /* If we have no swap space, do not bother scanning anon pages. */
1683 if (!sc
->may_swap
|| (get_nr_swap_pages() <= 0)) {
1684 scan_balance
= SCAN_FILE
;
1689 * Global reclaim will swap to prevent OOM even with no
1690 * swappiness, but memcg users want to use this knob to
1691 * disable swapping for individual groups completely when
1692 * using the memory controller's swap limit feature would be
1695 if (!global_reclaim(sc
) && !vmscan_swappiness(sc
)) {
1696 scan_balance
= SCAN_FILE
;
1701 * Do not apply any pressure balancing cleverness when the
1702 * system is close to OOM, scan both anon and file equally
1703 * (unless the swappiness setting disagrees with swapping).
1705 if (!sc
->priority
&& vmscan_swappiness(sc
)) {
1706 scan_balance
= SCAN_EQUAL
;
1710 anon
= get_lru_size(lruvec
, LRU_ACTIVE_ANON
) +
1711 get_lru_size(lruvec
, LRU_INACTIVE_ANON
);
1712 file
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
) +
1713 get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1716 * If it's foreseeable that reclaiming the file cache won't be
1717 * enough to get the zone back into a desirable shape, we have
1718 * to swap. Better start now and leave the - probably heavily
1719 * thrashing - remaining file pages alone.
1721 if (global_reclaim(sc
)) {
1722 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1723 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1724 scan_balance
= SCAN_ANON
;
1730 * There is enough inactive page cache, do not reclaim
1731 * anything from the anonymous working set right now.
1733 if (!inactive_file_is_low(lruvec
)) {
1734 scan_balance
= SCAN_FILE
;
1738 scan_balance
= SCAN_FRACT
;
1741 * With swappiness at 100, anonymous and file have the same priority.
1742 * This scanning priority is essentially the inverse of IO cost.
1744 anon_prio
= vmscan_swappiness(sc
);
1745 file_prio
= 200 - anon_prio
;
1748 * OK, so we have swap space and a fair amount of page cache
1749 * pages. We use the recently rotated / recently scanned
1750 * ratios to determine how valuable each cache is.
1752 * Because workloads change over time (and to avoid overflow)
1753 * we keep these statistics as a floating average, which ends
1754 * up weighing recent references more than old ones.
1756 * anon in [0], file in [1]
1758 spin_lock_irq(&zone
->lru_lock
);
1759 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1760 reclaim_stat
->recent_scanned
[0] /= 2;
1761 reclaim_stat
->recent_rotated
[0] /= 2;
1764 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1765 reclaim_stat
->recent_scanned
[1] /= 2;
1766 reclaim_stat
->recent_rotated
[1] /= 2;
1770 * The amount of pressure on anon vs file pages is inversely
1771 * proportional to the fraction of recently scanned pages on
1772 * each list that were recently referenced and in active use.
1774 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
1775 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1777 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
1778 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1779 spin_unlock_irq(&zone
->lru_lock
);
1783 denominator
= ap
+ fp
+ 1;
1785 for_each_evictable_lru(lru
) {
1786 int file
= is_file_lru(lru
);
1790 size
= get_lru_size(lruvec
, lru
);
1791 scan
= size
>> sc
->priority
;
1793 if (!scan
&& force_scan
)
1794 scan
= min(size
, SWAP_CLUSTER_MAX
);
1796 switch (scan_balance
) {
1798 /* Scan lists relative to size */
1802 * Scan types proportional to swappiness and
1803 * their relative recent reclaim efficiency.
1805 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1809 /* Scan one type exclusively */
1810 if ((scan_balance
== SCAN_FILE
) != file
)
1814 /* Look ma, no brain */
1822 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1824 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
1826 unsigned long nr
[NR_LRU_LISTS
];
1827 unsigned long nr_to_scan
;
1829 unsigned long nr_reclaimed
= 0;
1830 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1831 struct blk_plug plug
;
1833 get_scan_count(lruvec
, sc
, nr
);
1835 blk_start_plug(&plug
);
1836 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1837 nr
[LRU_INACTIVE_FILE
]) {
1838 for_each_evictable_lru(lru
) {
1840 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
1841 nr
[lru
] -= nr_to_scan
;
1843 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
1848 * On large memory systems, scan >> priority can become
1849 * really large. This is fine for the starting priority;
1850 * we want to put equal scanning pressure on each zone.
1851 * However, if the VM has a harder time of freeing pages,
1852 * with multiple processes reclaiming pages, the total
1853 * freeing target can get unreasonably large.
1855 if (nr_reclaimed
>= nr_to_reclaim
&&
1856 sc
->priority
< DEF_PRIORITY
)
1859 blk_finish_plug(&plug
);
1860 sc
->nr_reclaimed
+= nr_reclaimed
;
1863 * Even if we did not try to evict anon pages at all, we want to
1864 * rebalance the anon lru active/inactive ratio.
1866 if (inactive_anon_is_low(lruvec
))
1867 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
1868 sc
, LRU_ACTIVE_ANON
);
1870 throttle_vm_writeout(sc
->gfp_mask
);
1873 /* Use reclaim/compaction for costly allocs or under memory pressure */
1874 static bool in_reclaim_compaction(struct scan_control
*sc
)
1876 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
1877 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
1878 sc
->priority
< DEF_PRIORITY
- 2))
1885 * Reclaim/compaction is used for high-order allocation requests. It reclaims
1886 * order-0 pages before compacting the zone. should_continue_reclaim() returns
1887 * true if more pages should be reclaimed such that when the page allocator
1888 * calls try_to_compact_zone() that it will have enough free pages to succeed.
1889 * It will give up earlier than that if there is difficulty reclaiming pages.
1891 static inline bool should_continue_reclaim(struct zone
*zone
,
1892 unsigned long nr_reclaimed
,
1893 unsigned long nr_scanned
,
1894 struct scan_control
*sc
)
1896 unsigned long pages_for_compaction
;
1897 unsigned long inactive_lru_pages
;
1899 /* If not in reclaim/compaction mode, stop */
1900 if (!in_reclaim_compaction(sc
))
1903 /* Consider stopping depending on scan and reclaim activity */
1904 if (sc
->gfp_mask
& __GFP_REPEAT
) {
1906 * For __GFP_REPEAT allocations, stop reclaiming if the
1907 * full LRU list has been scanned and we are still failing
1908 * to reclaim pages. This full LRU scan is potentially
1909 * expensive but a __GFP_REPEAT caller really wants to succeed
1911 if (!nr_reclaimed
&& !nr_scanned
)
1915 * For non-__GFP_REPEAT allocations which can presumably
1916 * fail without consequence, stop if we failed to reclaim
1917 * any pages from the last SWAP_CLUSTER_MAX number of
1918 * pages that were scanned. This will return to the
1919 * caller faster at the risk reclaim/compaction and
1920 * the resulting allocation attempt fails
1927 * If we have not reclaimed enough pages for compaction and the
1928 * inactive lists are large enough, continue reclaiming
1930 pages_for_compaction
= (2UL << sc
->order
);
1931 inactive_lru_pages
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1932 if (get_nr_swap_pages() > 0)
1933 inactive_lru_pages
+= zone_page_state(zone
, NR_INACTIVE_ANON
);
1934 if (sc
->nr_reclaimed
< pages_for_compaction
&&
1935 inactive_lru_pages
> pages_for_compaction
)
1938 /* If compaction would go ahead or the allocation would succeed, stop */
1939 switch (compaction_suitable(zone
, sc
->order
)) {
1940 case COMPACT_PARTIAL
:
1941 case COMPACT_CONTINUE
:
1948 static void shrink_zone(struct zone
*zone
, struct scan_control
*sc
)
1950 unsigned long nr_reclaimed
, nr_scanned
;
1953 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
1954 struct mem_cgroup_reclaim_cookie reclaim
= {
1956 .priority
= sc
->priority
,
1958 struct mem_cgroup
*memcg
;
1960 nr_reclaimed
= sc
->nr_reclaimed
;
1961 nr_scanned
= sc
->nr_scanned
;
1963 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
1965 struct lruvec
*lruvec
;
1967 lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
1969 shrink_lruvec(lruvec
, sc
);
1972 * Direct reclaim and kswapd have to scan all memory
1973 * cgroups to fulfill the overall scan target for the
1976 * Limit reclaim, on the other hand, only cares about
1977 * nr_to_reclaim pages to be reclaimed and it will
1978 * retry with decreasing priority if one round over the
1979 * whole hierarchy is not sufficient.
1981 if (!global_reclaim(sc
) &&
1982 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
1983 mem_cgroup_iter_break(root
, memcg
);
1986 memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
);
1989 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
,
1990 sc
->nr_scanned
- nr_scanned
,
1991 sc
->nr_reclaimed
- nr_reclaimed
);
1993 } while (should_continue_reclaim(zone
, sc
->nr_reclaimed
- nr_reclaimed
,
1994 sc
->nr_scanned
- nr_scanned
, sc
));
1997 /* Returns true if compaction should go ahead for a high-order request */
1998 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
2000 unsigned long balance_gap
, watermark
;
2003 /* Do not consider compaction for orders reclaim is meant to satisfy */
2004 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
)
2008 * Compaction takes time to run and there are potentially other
2009 * callers using the pages just freed. Continue reclaiming until
2010 * there is a buffer of free pages available to give compaction
2011 * a reasonable chance of completing and allocating the page
2013 balance_gap
= min(low_wmark_pages(zone
),
2014 (zone
->managed_pages
+ KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2015 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2016 watermark
= high_wmark_pages(zone
) + balance_gap
+ (2UL << sc
->order
);
2017 watermark_ok
= zone_watermark_ok_safe(zone
, 0, watermark
, 0, 0);
2020 * If compaction is deferred, reclaim up to a point where
2021 * compaction will have a chance of success when re-enabled
2023 if (compaction_deferred(zone
, sc
->order
))
2024 return watermark_ok
;
2026 /* If compaction is not ready to start, keep reclaiming */
2027 if (!compaction_suitable(zone
, sc
->order
))
2030 return watermark_ok
;
2034 * This is the direct reclaim path, for page-allocating processes. We only
2035 * try to reclaim pages from zones which will satisfy the caller's allocation
2038 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2040 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2042 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2043 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2044 * zone defense algorithm.
2046 * If a zone is deemed to be full of pinned pages then just give it a light
2047 * scan then give up on it.
2049 * This function returns true if a zone is being reclaimed for a costly
2050 * high-order allocation and compaction is ready to begin. This indicates to
2051 * the caller that it should consider retrying the allocation instead of
2054 static bool shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2058 unsigned long nr_soft_reclaimed
;
2059 unsigned long nr_soft_scanned
;
2060 bool aborted_reclaim
= false;
2063 * If the number of buffer_heads in the machine exceeds the maximum
2064 * allowed level, force direct reclaim to scan the highmem zone as
2065 * highmem pages could be pinning lowmem pages storing buffer_heads
2067 if (buffer_heads_over_limit
)
2068 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2070 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2071 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2072 if (!populated_zone(zone
))
2075 * Take care memory controller reclaiming has small influence
2078 if (global_reclaim(sc
)) {
2079 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2081 if (zone
->all_unreclaimable
&&
2082 sc
->priority
!= DEF_PRIORITY
)
2083 continue; /* Let kswapd poll it */
2084 if (IS_ENABLED(CONFIG_COMPACTION
)) {
2086 * If we already have plenty of memory free for
2087 * compaction in this zone, don't free any more.
2088 * Even though compaction is invoked for any
2089 * non-zero order, only frequent costly order
2090 * reclamation is disruptive enough to become a
2091 * noticeable problem, like transparent huge
2094 if (compaction_ready(zone
, sc
)) {
2095 aborted_reclaim
= true;
2100 * This steals pages from memory cgroups over softlimit
2101 * and returns the number of reclaimed pages and
2102 * scanned pages. This works for global memory pressure
2103 * and balancing, not for a memcg's limit.
2105 nr_soft_scanned
= 0;
2106 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2107 sc
->order
, sc
->gfp_mask
,
2109 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2110 sc
->nr_scanned
+= nr_soft_scanned
;
2111 /* need some check for avoid more shrink_zone() */
2114 shrink_zone(zone
, sc
);
2117 return aborted_reclaim
;
2120 static unsigned long zone_reclaimable_pages(struct zone
*zone
)
2124 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
2125 zone_page_state(zone
, NR_INACTIVE_FILE
);
2127 if (get_nr_swap_pages() > 0)
2128 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
2129 zone_page_state(zone
, NR_INACTIVE_ANON
);
2134 static bool zone_reclaimable(struct zone
*zone
)
2136 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2139 /* All zones in zonelist are unreclaimable? */
2140 static bool all_unreclaimable(struct zonelist
*zonelist
,
2141 struct scan_control
*sc
)
2146 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2147 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2148 if (!populated_zone(zone
))
2150 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2152 if (!zone
->all_unreclaimable
)
2160 * This is the main entry point to direct page reclaim.
2162 * If a full scan of the inactive list fails to free enough memory then we
2163 * are "out of memory" and something needs to be killed.
2165 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2166 * high - the zone may be full of dirty or under-writeback pages, which this
2167 * caller can't do much about. We kick the writeback threads and take explicit
2168 * naps in the hope that some of these pages can be written. But if the
2169 * allocating task holds filesystem locks which prevent writeout this might not
2170 * work, and the allocation attempt will fail.
2172 * returns: 0, if no pages reclaimed
2173 * else, the number of pages reclaimed
2175 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2176 struct scan_control
*sc
,
2177 struct shrink_control
*shrink
)
2179 unsigned long total_scanned
= 0;
2180 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2183 unsigned long writeback_threshold
;
2184 bool aborted_reclaim
;
2186 delayacct_freepages_start();
2188 if (global_reclaim(sc
))
2189 count_vm_event(ALLOCSTALL
);
2192 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2195 aborted_reclaim
= shrink_zones(zonelist
, sc
);
2198 * Don't shrink slabs when reclaiming memory from
2199 * over limit cgroups
2201 if (global_reclaim(sc
)) {
2202 unsigned long lru_pages
= 0;
2203 for_each_zone_zonelist(zone
, z
, zonelist
,
2204 gfp_zone(sc
->gfp_mask
)) {
2205 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2208 lru_pages
+= zone_reclaimable_pages(zone
);
2211 shrink_slab(shrink
, sc
->nr_scanned
, lru_pages
);
2212 if (reclaim_state
) {
2213 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2214 reclaim_state
->reclaimed_slab
= 0;
2217 total_scanned
+= sc
->nr_scanned
;
2218 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2222 * If we're getting trouble reclaiming, start doing
2223 * writepage even in laptop mode.
2225 if (sc
->priority
< DEF_PRIORITY
- 2)
2226 sc
->may_writepage
= 1;
2229 * Try to write back as many pages as we just scanned. This
2230 * tends to cause slow streaming writers to write data to the
2231 * disk smoothly, at the dirtying rate, which is nice. But
2232 * that's undesirable in laptop mode, where we *want* lumpy
2233 * writeout. So in laptop mode, write out the whole world.
2235 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2236 if (total_scanned
> writeback_threshold
) {
2237 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2238 WB_REASON_TRY_TO_FREE_PAGES
);
2239 sc
->may_writepage
= 1;
2242 /* Take a nap, wait for some writeback to complete */
2243 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2244 sc
->priority
< DEF_PRIORITY
- 2) {
2245 struct zone
*preferred_zone
;
2247 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2248 &cpuset_current_mems_allowed
,
2250 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2252 } while (--sc
->priority
>= 0);
2255 delayacct_freepages_end();
2257 if (sc
->nr_reclaimed
)
2258 return sc
->nr_reclaimed
;
2261 * As hibernation is going on, kswapd is freezed so that it can't mark
2262 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2265 if (oom_killer_disabled
)
2268 /* Aborted reclaim to try compaction? don't OOM, then */
2269 if (aborted_reclaim
)
2272 /* top priority shrink_zones still had more to do? don't OOM, then */
2273 if (global_reclaim(sc
) && !all_unreclaimable(zonelist
, sc
))
2279 static bool pfmemalloc_watermark_ok(pg_data_t
*pgdat
)
2282 unsigned long pfmemalloc_reserve
= 0;
2283 unsigned long free_pages
= 0;
2287 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
2288 zone
= &pgdat
->node_zones
[i
];
2289 pfmemalloc_reserve
+= min_wmark_pages(zone
);
2290 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
2293 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
2295 /* kswapd must be awake if processes are being throttled */
2296 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
2297 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
,
2298 (enum zone_type
)ZONE_NORMAL
);
2299 wake_up_interruptible(&pgdat
->kswapd_wait
);
2306 * Throttle direct reclaimers if backing storage is backed by the network
2307 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2308 * depleted. kswapd will continue to make progress and wake the processes
2309 * when the low watermark is reached.
2311 * Returns true if a fatal signal was delivered during throttling. If this
2312 * happens, the page allocator should not consider triggering the OOM killer.
2314 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
2315 nodemask_t
*nodemask
)
2318 int high_zoneidx
= gfp_zone(gfp_mask
);
2322 * Kernel threads should not be throttled as they may be indirectly
2323 * responsible for cleaning pages necessary for reclaim to make forward
2324 * progress. kjournald for example may enter direct reclaim while
2325 * committing a transaction where throttling it could forcing other
2326 * processes to block on log_wait_commit().
2328 if (current
->flags
& PF_KTHREAD
)
2332 * If a fatal signal is pending, this process should not throttle.
2333 * It should return quickly so it can exit and free its memory
2335 if (fatal_signal_pending(current
))
2338 /* Check if the pfmemalloc reserves are ok */
2339 first_zones_zonelist(zonelist
, high_zoneidx
, NULL
, &zone
);
2340 pgdat
= zone
->zone_pgdat
;
2341 if (pfmemalloc_watermark_ok(pgdat
))
2344 /* Account for the throttling */
2345 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
2348 * If the caller cannot enter the filesystem, it's possible that it
2349 * is due to the caller holding an FS lock or performing a journal
2350 * transaction in the case of a filesystem like ext[3|4]. In this case,
2351 * it is not safe to block on pfmemalloc_wait as kswapd could be
2352 * blocked waiting on the same lock. Instead, throttle for up to a
2353 * second before continuing.
2355 if (!(gfp_mask
& __GFP_FS
)) {
2356 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
2357 pfmemalloc_watermark_ok(pgdat
), HZ
);
2362 /* Throttle until kswapd wakes the process */
2363 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
2364 pfmemalloc_watermark_ok(pgdat
));
2367 if (fatal_signal_pending(current
))
2374 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2375 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2377 unsigned long nr_reclaimed
;
2378 struct scan_control sc
= {
2379 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
2380 .may_writepage
= !laptop_mode
,
2381 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2385 .priority
= DEF_PRIORITY
,
2386 .target_mem_cgroup
= NULL
,
2387 .nodemask
= nodemask
,
2389 struct shrink_control shrink
= {
2390 .gfp_mask
= sc
.gfp_mask
,
2394 * Do not enter reclaim if fatal signal was delivered while throttled.
2395 * 1 is returned so that the page allocator does not OOM kill at this
2398 if (throttle_direct_reclaim(gfp_mask
, zonelist
, nodemask
))
2401 trace_mm_vmscan_direct_reclaim_begin(order
,
2405 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2407 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2409 return nr_reclaimed
;
2414 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2415 gfp_t gfp_mask
, bool noswap
,
2417 unsigned long *nr_scanned
)
2419 struct scan_control sc
= {
2421 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2422 .may_writepage
= !laptop_mode
,
2424 .may_swap
= !noswap
,
2427 .target_mem_cgroup
= memcg
,
2429 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2431 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2432 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2434 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
2439 * NOTE: Although we can get the priority field, using it
2440 * here is not a good idea, since it limits the pages we can scan.
2441 * if we don't reclaim here, the shrink_zone from balance_pgdat
2442 * will pick up pages from other mem cgroup's as well. We hack
2443 * the priority and make it zero.
2445 shrink_lruvec(lruvec
, &sc
);
2447 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2449 *nr_scanned
= sc
.nr_scanned
;
2450 return sc
.nr_reclaimed
;
2453 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2457 struct zonelist
*zonelist
;
2458 unsigned long nr_reclaimed
;
2460 struct scan_control sc
= {
2461 .may_writepage
= !laptop_mode
,
2463 .may_swap
= !noswap
,
2464 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2466 .priority
= DEF_PRIORITY
,
2467 .target_mem_cgroup
= memcg
,
2468 .nodemask
= NULL
, /* we don't care the placement */
2469 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2470 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2472 struct shrink_control shrink
= {
2473 .gfp_mask
= sc
.gfp_mask
,
2477 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2478 * take care of from where we get pages. So the node where we start the
2479 * scan does not need to be the current node.
2481 nid
= mem_cgroup_select_victim_node(memcg
);
2483 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2485 trace_mm_vmscan_memcg_reclaim_begin(0,
2489 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2491 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2493 return nr_reclaimed
;
2497 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
)
2499 struct mem_cgroup
*memcg
;
2501 if (!total_swap_pages
)
2504 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2506 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2508 if (inactive_anon_is_low(lruvec
))
2509 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2510 sc
, LRU_ACTIVE_ANON
);
2512 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2516 static bool zone_balanced(struct zone
*zone
, int order
,
2517 unsigned long balance_gap
, int classzone_idx
)
2519 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
) +
2520 balance_gap
, classzone_idx
, 0))
2523 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&&
2524 !compaction_suitable(zone
, order
))
2531 * pgdat_balanced() is used when checking if a node is balanced.
2533 * For order-0, all zones must be balanced!
2535 * For high-order allocations only zones that meet watermarks and are in a
2536 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2537 * total of balanced pages must be at least 25% of the zones allowed by
2538 * classzone_idx for the node to be considered balanced. Forcing all zones to
2539 * be balanced for high orders can cause excessive reclaim when there are
2541 * The choice of 25% is due to
2542 * o a 16M DMA zone that is balanced will not balance a zone on any
2543 * reasonable sized machine
2544 * o On all other machines, the top zone must be at least a reasonable
2545 * percentage of the middle zones. For example, on 32-bit x86, highmem
2546 * would need to be at least 256M for it to be balance a whole node.
2547 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2548 * to balance a node on its own. These seemed like reasonable ratios.
2550 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2552 unsigned long managed_pages
= 0;
2553 unsigned long balanced_pages
= 0;
2556 /* Check the watermark levels */
2557 for (i
= 0; i
<= classzone_idx
; i
++) {
2558 struct zone
*zone
= pgdat
->node_zones
+ i
;
2560 if (!populated_zone(zone
))
2563 managed_pages
+= zone
->managed_pages
;
2566 * A special case here:
2568 * balance_pgdat() skips over all_unreclaimable after
2569 * DEF_PRIORITY. Effectively, it considers them balanced so
2570 * they must be considered balanced here as well!
2572 if (zone
->all_unreclaimable
) {
2573 balanced_pages
+= zone
->managed_pages
;
2577 if (zone_balanced(zone
, order
, 0, i
))
2578 balanced_pages
+= zone
->managed_pages
;
2584 return balanced_pages
>= (managed_pages
>> 2);
2590 * Prepare kswapd for sleeping. This verifies that there are no processes
2591 * waiting in throttle_direct_reclaim() and that watermarks have been met.
2593 * Returns true if kswapd is ready to sleep
2595 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, long remaining
,
2598 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2603 * There is a potential race between when kswapd checks its watermarks
2604 * and a process gets throttled. There is also a potential race if
2605 * processes get throttled, kswapd wakes, a large process exits therby
2606 * balancing the zones that causes kswapd to miss a wakeup. If kswapd
2607 * is going to sleep, no process should be sleeping on pfmemalloc_wait
2608 * so wake them now if necessary. If necessary, processes will wake
2609 * kswapd and get throttled again
2611 if (waitqueue_active(&pgdat
->pfmemalloc_wait
)) {
2612 wake_up(&pgdat
->pfmemalloc_wait
);
2616 return pgdat_balanced(pgdat
, order
, classzone_idx
);
2620 * For kswapd, balance_pgdat() will work across all this node's zones until
2621 * they are all at high_wmark_pages(zone).
2623 * Returns the final order kswapd was reclaiming at
2625 * There is special handling here for zones which are full of pinned pages.
2626 * This can happen if the pages are all mlocked, or if they are all used by
2627 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2628 * What we do is to detect the case where all pages in the zone have been
2629 * scanned twice and there has been zero successful reclaim. Mark the zone as
2630 * dead and from now on, only perform a short scan. Basically we're polling
2631 * the zone for when the problem goes away.
2633 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2634 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2635 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2636 * lower zones regardless of the number of free pages in the lower zones. This
2637 * interoperates with the page allocator fallback scheme to ensure that aging
2638 * of pages is balanced across the zones.
2640 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2643 bool pgdat_is_balanced
= false;
2645 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2646 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2647 unsigned long nr_soft_reclaimed
;
2648 unsigned long nr_soft_scanned
;
2649 struct scan_control sc
= {
2650 .gfp_mask
= GFP_KERNEL
,
2654 * kswapd doesn't want to be bailed out while reclaim. because
2655 * we want to put equal scanning pressure on each zone.
2657 .nr_to_reclaim
= ULONG_MAX
,
2659 .target_mem_cgroup
= NULL
,
2661 struct shrink_control shrink
= {
2662 .gfp_mask
= sc
.gfp_mask
,
2665 sc
.priority
= DEF_PRIORITY
;
2666 sc
.nr_reclaimed
= 0;
2667 sc
.may_writepage
= !laptop_mode
;
2668 count_vm_event(PAGEOUTRUN
);
2671 unsigned long lru_pages
= 0;
2674 * Scan in the highmem->dma direction for the highest
2675 * zone which needs scanning
2677 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2678 struct zone
*zone
= pgdat
->node_zones
+ i
;
2680 if (!populated_zone(zone
))
2683 if (zone
->all_unreclaimable
&&
2684 sc
.priority
!= DEF_PRIORITY
)
2688 * Do some background aging of the anon list, to give
2689 * pages a chance to be referenced before reclaiming.
2691 age_active_anon(zone
, &sc
);
2694 * If the number of buffer_heads in the machine
2695 * exceeds the maximum allowed level and this node
2696 * has a highmem zone, force kswapd to reclaim from
2697 * it to relieve lowmem pressure.
2699 if (buffer_heads_over_limit
&& is_highmem_idx(i
)) {
2704 if (!zone_balanced(zone
, order
, 0, 0)) {
2708 /* If balanced, clear the congested flag */
2709 zone_clear_flag(zone
, ZONE_CONGESTED
);
2714 pgdat_is_balanced
= true;
2718 for (i
= 0; i
<= end_zone
; i
++) {
2719 struct zone
*zone
= pgdat
->node_zones
+ i
;
2721 lru_pages
+= zone_reclaimable_pages(zone
);
2725 * Now scan the zone in the dma->highmem direction, stopping
2726 * at the last zone which needs scanning.
2728 * We do this because the page allocator works in the opposite
2729 * direction. This prevents the page allocator from allocating
2730 * pages behind kswapd's direction of progress, which would
2731 * cause too much scanning of the lower zones.
2733 for (i
= 0; i
<= end_zone
; i
++) {
2734 struct zone
*zone
= pgdat
->node_zones
+ i
;
2735 int nr_slab
, testorder
;
2736 unsigned long balance_gap
;
2738 if (!populated_zone(zone
))
2741 if (zone
->all_unreclaimable
&&
2742 sc
.priority
!= DEF_PRIORITY
)
2747 nr_soft_scanned
= 0;
2749 * Call soft limit reclaim before calling shrink_zone.
2751 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2754 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
2757 * We put equal pressure on every zone, unless
2758 * one zone has way too many pages free
2759 * already. The "too many pages" is defined
2760 * as the high wmark plus a "gap" where the
2761 * gap is either the low watermark or 1%
2762 * of the zone, whichever is smaller.
2764 balance_gap
= min(low_wmark_pages(zone
),
2765 (zone
->managed_pages
+
2766 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2767 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2769 * Kswapd reclaims only single pages with compaction
2770 * enabled. Trying too hard to reclaim until contiguous
2771 * free pages have become available can hurt performance
2772 * by evicting too much useful data from memory.
2773 * Do not reclaim more than needed for compaction.
2776 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&&
2777 compaction_suitable(zone
, order
) !=
2781 if ((buffer_heads_over_limit
&& is_highmem_idx(i
)) ||
2782 !zone_balanced(zone
, testorder
,
2783 balance_gap
, end_zone
)) {
2784 shrink_zone(zone
, &sc
);
2786 reclaim_state
->reclaimed_slab
= 0;
2787 nr_slab
= shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
);
2788 sc
.nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2790 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2791 zone
->all_unreclaimable
= 1;
2795 * If we're getting trouble reclaiming, start doing
2796 * writepage even in laptop mode.
2798 if (sc
.priority
< DEF_PRIORITY
- 2)
2799 sc
.may_writepage
= 1;
2801 if (zone
->all_unreclaimable
) {
2802 if (end_zone
&& end_zone
== i
)
2807 if (zone_balanced(zone
, testorder
, 0, end_zone
))
2809 * If a zone reaches its high watermark,
2810 * consider it to be no longer congested. It's
2811 * possible there are dirty pages backed by
2812 * congested BDIs but as pressure is relieved,
2813 * speculatively avoid congestion waits
2815 zone_clear_flag(zone
, ZONE_CONGESTED
);
2819 * If the low watermark is met there is no need for processes
2820 * to be throttled on pfmemalloc_wait as they should not be
2821 * able to safely make forward progress. Wake them
2823 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
2824 pfmemalloc_watermark_ok(pgdat
))
2825 wake_up(&pgdat
->pfmemalloc_wait
);
2827 if (pgdat_balanced(pgdat
, order
, *classzone_idx
)) {
2828 pgdat_is_balanced
= true;
2829 break; /* kswapd: all done */
2833 * We do this so kswapd doesn't build up large priorities for
2834 * example when it is freeing in parallel with allocators. It
2835 * matches the direct reclaim path behaviour in terms of impact
2836 * on zone->*_priority.
2838 if (sc
.nr_reclaimed
>= SWAP_CLUSTER_MAX
)
2840 } while (--sc
.priority
>= 0);
2843 if (!pgdat_is_balanced
) {
2849 * Fragmentation may mean that the system cannot be
2850 * rebalanced for high-order allocations in all zones.
2851 * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
2852 * it means the zones have been fully scanned and are still
2853 * not balanced. For high-order allocations, there is
2854 * little point trying all over again as kswapd may
2857 * Instead, recheck all watermarks at order-0 as they
2858 * are the most important. If watermarks are ok, kswapd will go
2859 * back to sleep. High-order users can still perform direct
2860 * reclaim if they wish.
2862 if (sc
.nr_reclaimed
< SWAP_CLUSTER_MAX
)
2863 order
= sc
.order
= 0;
2869 * If kswapd was reclaiming at a higher order, it has the option of
2870 * sleeping without all zones being balanced. Before it does, it must
2871 * ensure that the watermarks for order-0 on *all* zones are met and
2872 * that the congestion flags are cleared. The congestion flag must
2873 * be cleared as kswapd is the only mechanism that clears the flag
2874 * and it is potentially going to sleep here.
2877 int zones_need_compaction
= 1;
2879 for (i
= 0; i
<= end_zone
; i
++) {
2880 struct zone
*zone
= pgdat
->node_zones
+ i
;
2882 if (!populated_zone(zone
))
2885 /* Check if the memory needs to be defragmented. */
2886 if (zone_watermark_ok(zone
, order
,
2887 low_wmark_pages(zone
), *classzone_idx
, 0))
2888 zones_need_compaction
= 0;
2891 if (zones_need_compaction
)
2892 compact_pgdat(pgdat
, order
);
2896 * Return the order we were reclaiming at so prepare_kswapd_sleep()
2897 * makes a decision on the order we were last reclaiming at. However,
2898 * if another caller entered the allocator slow path while kswapd
2899 * was awake, order will remain at the higher level
2901 *classzone_idx
= end_zone
;
2905 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2910 if (freezing(current
) || kthread_should_stop())
2913 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2915 /* Try to sleep for a short interval */
2916 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
2917 remaining
= schedule_timeout(HZ
/10);
2918 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2919 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
2923 * After a short sleep, check if it was a premature sleep. If not, then
2924 * go fully to sleep until explicitly woken up.
2926 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
2927 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
2930 * vmstat counters are not perfectly accurate and the estimated
2931 * value for counters such as NR_FREE_PAGES can deviate from the
2932 * true value by nr_online_cpus * threshold. To avoid the zone
2933 * watermarks being breached while under pressure, we reduce the
2934 * per-cpu vmstat threshold while kswapd is awake and restore
2935 * them before going back to sleep.
2937 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
2940 * Compaction records what page blocks it recently failed to
2941 * isolate pages from and skips them in the future scanning.
2942 * When kswapd is going to sleep, it is reasonable to assume
2943 * that pages and compaction may succeed so reset the cache.
2945 reset_isolation_suitable(pgdat
);
2947 if (!kthread_should_stop())
2950 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
2953 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
2955 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
2957 finish_wait(&pgdat
->kswapd_wait
, &wait
);
2961 * The background pageout daemon, started as a kernel thread
2962 * from the init process.
2964 * This basically trickles out pages so that we have _some_
2965 * free memory available even if there is no other activity
2966 * that frees anything up. This is needed for things like routing
2967 * etc, where we otherwise might have all activity going on in
2968 * asynchronous contexts that cannot page things out.
2970 * If there are applications that are active memory-allocators
2971 * (most normal use), this basically shouldn't matter.
2973 static int kswapd(void *p
)
2975 unsigned long order
, new_order
;
2976 unsigned balanced_order
;
2977 int classzone_idx
, new_classzone_idx
;
2978 int balanced_classzone_idx
;
2979 pg_data_t
*pgdat
= (pg_data_t
*)p
;
2980 struct task_struct
*tsk
= current
;
2982 struct reclaim_state reclaim_state
= {
2983 .reclaimed_slab
= 0,
2985 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
2987 lockdep_set_current_reclaim_state(GFP_KERNEL
);
2989 if (!cpumask_empty(cpumask
))
2990 set_cpus_allowed_ptr(tsk
, cpumask
);
2991 current
->reclaim_state
= &reclaim_state
;
2994 * Tell the memory management that we're a "memory allocator",
2995 * and that if we need more memory we should get access to it
2996 * regardless (see "__alloc_pages()"). "kswapd" should
2997 * never get caught in the normal page freeing logic.
2999 * (Kswapd normally doesn't need memory anyway, but sometimes
3000 * you need a small amount of memory in order to be able to
3001 * page out something else, and this flag essentially protects
3002 * us from recursively trying to free more memory as we're
3003 * trying to free the first piece of memory in the first place).
3005 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3008 order
= new_order
= 0;
3010 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
3011 balanced_classzone_idx
= classzone_idx
;
3016 * If the last balance_pgdat was unsuccessful it's unlikely a
3017 * new request of a similar or harder type will succeed soon
3018 * so consider going to sleep on the basis we reclaimed at
3020 if (balanced_classzone_idx
>= new_classzone_idx
&&
3021 balanced_order
== new_order
) {
3022 new_order
= pgdat
->kswapd_max_order
;
3023 new_classzone_idx
= pgdat
->classzone_idx
;
3024 pgdat
->kswapd_max_order
= 0;
3025 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3028 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
3030 * Don't sleep if someone wants a larger 'order'
3031 * allocation or has tigher zone constraints
3034 classzone_idx
= new_classzone_idx
;
3036 kswapd_try_to_sleep(pgdat
, balanced_order
,
3037 balanced_classzone_idx
);
3038 order
= pgdat
->kswapd_max_order
;
3039 classzone_idx
= pgdat
->classzone_idx
;
3041 new_classzone_idx
= classzone_idx
;
3042 pgdat
->kswapd_max_order
= 0;
3043 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3046 ret
= try_to_freeze();
3047 if (kthread_should_stop())
3051 * We can speed up thawing tasks if we don't call balance_pgdat
3052 * after returning from the refrigerator
3055 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
3056 balanced_classzone_idx
= classzone_idx
;
3057 balanced_order
= balance_pgdat(pgdat
, order
,
3058 &balanced_classzone_idx
);
3062 current
->reclaim_state
= NULL
;
3067 * A zone is low on free memory, so wake its kswapd task to service it.
3069 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3073 if (!populated_zone(zone
))
3076 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
3078 pgdat
= zone
->zone_pgdat
;
3079 if (pgdat
->kswapd_max_order
< order
) {
3080 pgdat
->kswapd_max_order
= order
;
3081 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3083 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3085 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
3088 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3089 wake_up_interruptible(&pgdat
->kswapd_wait
);
3092 #ifdef CONFIG_HIBERNATION
3094 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3097 * Rather than trying to age LRUs the aim is to preserve the overall
3098 * LRU order by reclaiming preferentially
3099 * inactive > active > active referenced > active mapped
3101 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3103 struct reclaim_state reclaim_state
;
3104 struct scan_control sc
= {
3105 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3109 .nr_to_reclaim
= nr_to_reclaim
,
3110 .hibernation_mode
= 1,
3112 .priority
= DEF_PRIORITY
,
3114 struct shrink_control shrink
= {
3115 .gfp_mask
= sc
.gfp_mask
,
3117 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3118 struct task_struct
*p
= current
;
3119 unsigned long nr_reclaimed
;
3121 p
->flags
|= PF_MEMALLOC
;
3122 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3123 reclaim_state
.reclaimed_slab
= 0;
3124 p
->reclaim_state
= &reclaim_state
;
3126 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
3128 p
->reclaim_state
= NULL
;
3129 lockdep_clear_current_reclaim_state();
3130 p
->flags
&= ~PF_MEMALLOC
;
3132 return nr_reclaimed
;
3134 #endif /* CONFIG_HIBERNATION */
3136 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3137 not required for correctness. So if the last cpu in a node goes
3138 away, we get changed to run anywhere: as the first one comes back,
3139 restore their cpu bindings. */
3140 static int cpu_callback(struct notifier_block
*nfb
, unsigned long action
,
3145 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3146 for_each_node_state(nid
, N_MEMORY
) {
3147 pg_data_t
*pgdat
= NODE_DATA(nid
);
3148 const struct cpumask
*mask
;
3150 mask
= cpumask_of_node(pgdat
->node_id
);
3152 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3153 /* One of our CPUs online: restore mask */
3154 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3161 * This kswapd start function will be called by init and node-hot-add.
3162 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3164 int kswapd_run(int nid
)
3166 pg_data_t
*pgdat
= NODE_DATA(nid
);
3172 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3173 if (IS_ERR(pgdat
->kswapd
)) {
3174 /* failure at boot is fatal */
3175 BUG_ON(system_state
== SYSTEM_BOOTING
);
3176 pr_err("Failed to start kswapd on node %d\n", nid
);
3177 ret
= PTR_ERR(pgdat
->kswapd
);
3178 pgdat
->kswapd
= NULL
;
3184 * Called by memory hotplug when all memory in a node is offlined. Caller must
3185 * hold lock_memory_hotplug().
3187 void kswapd_stop(int nid
)
3189 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3192 kthread_stop(kswapd
);
3193 NODE_DATA(nid
)->kswapd
= NULL
;
3197 static int __init
kswapd_init(void)
3202 for_each_node_state(nid
, N_MEMORY
)
3204 hotcpu_notifier(cpu_callback
, 0);
3208 module_init(kswapd_init
)
3214 * If non-zero call zone_reclaim when the number of free pages falls below
3217 int zone_reclaim_mode __read_mostly
;
3219 #define RECLAIM_OFF 0
3220 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3221 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3222 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3225 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3226 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3229 #define ZONE_RECLAIM_PRIORITY 4
3232 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3235 int sysctl_min_unmapped_ratio
= 1;
3238 * If the number of slab pages in a zone grows beyond this percentage then
3239 * slab reclaim needs to occur.
3241 int sysctl_min_slab_ratio
= 5;
3243 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3245 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3246 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3247 zone_page_state(zone
, NR_ACTIVE_FILE
);
3250 * It's possible for there to be more file mapped pages than
3251 * accounted for by the pages on the file LRU lists because
3252 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3254 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3257 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3258 static long zone_pagecache_reclaimable(struct zone
*zone
)
3260 long nr_pagecache_reclaimable
;
3264 * If RECLAIM_SWAP is set, then all file pages are considered
3265 * potentially reclaimable. Otherwise, we have to worry about
3266 * pages like swapcache and zone_unmapped_file_pages() provides
3269 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3270 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3272 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3274 /* If we can't clean pages, remove dirty pages from consideration */
3275 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3276 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3278 /* Watch for any possible underflows due to delta */
3279 if (unlikely(delta
> nr_pagecache_reclaimable
))
3280 delta
= nr_pagecache_reclaimable
;
3282 return nr_pagecache_reclaimable
- delta
;
3286 * Try to free up some pages from this zone through reclaim.
3288 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3290 /* Minimum pages needed in order to stay on node */
3291 const unsigned long nr_pages
= 1 << order
;
3292 struct task_struct
*p
= current
;
3293 struct reclaim_state reclaim_state
;
3294 struct scan_control sc
= {
3295 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3296 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3298 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3299 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
3301 .priority
= ZONE_RECLAIM_PRIORITY
,
3303 struct shrink_control shrink
= {
3304 .gfp_mask
= sc
.gfp_mask
,
3306 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3310 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3311 * and we also need to be able to write out pages for RECLAIM_WRITE
3314 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3315 lockdep_set_current_reclaim_state(gfp_mask
);
3316 reclaim_state
.reclaimed_slab
= 0;
3317 p
->reclaim_state
= &reclaim_state
;
3319 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3321 * Free memory by calling shrink zone with increasing
3322 * priorities until we have enough memory freed.
3325 shrink_zone(zone
, &sc
);
3326 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
3329 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3330 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3332 * shrink_slab() does not currently allow us to determine how
3333 * many pages were freed in this zone. So we take the current
3334 * number of slab pages and shake the slab until it is reduced
3335 * by the same nr_pages that we used for reclaiming unmapped
3338 * Note that shrink_slab will free memory on all zones and may
3342 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3344 /* No reclaimable slab or very low memory pressure */
3345 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3348 /* Freed enough memory */
3349 nr_slab_pages1
= zone_page_state(zone
,
3350 NR_SLAB_RECLAIMABLE
);
3351 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3356 * Update nr_reclaimed by the number of slab pages we
3357 * reclaimed from this zone.
3359 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3360 if (nr_slab_pages1
< nr_slab_pages0
)
3361 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3364 p
->reclaim_state
= NULL
;
3365 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3366 lockdep_clear_current_reclaim_state();
3367 return sc
.nr_reclaimed
>= nr_pages
;
3370 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3376 * Zone reclaim reclaims unmapped file backed pages and
3377 * slab pages if we are over the defined limits.
3379 * A small portion of unmapped file backed pages is needed for
3380 * file I/O otherwise pages read by file I/O will be immediately
3381 * thrown out if the zone is overallocated. So we do not reclaim
3382 * if less than a specified percentage of the zone is used by
3383 * unmapped file backed pages.
3385 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3386 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3387 return ZONE_RECLAIM_FULL
;
3389 if (zone
->all_unreclaimable
)
3390 return ZONE_RECLAIM_FULL
;
3393 * Do not scan if the allocation should not be delayed.
3395 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3396 return ZONE_RECLAIM_NOSCAN
;
3399 * Only run zone reclaim on the local zone or on zones that do not
3400 * have associated processors. This will favor the local processor
3401 * over remote processors and spread off node memory allocations
3402 * as wide as possible.
3404 node_id
= zone_to_nid(zone
);
3405 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3406 return ZONE_RECLAIM_NOSCAN
;
3408 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3409 return ZONE_RECLAIM_NOSCAN
;
3411 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3412 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3415 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3422 * page_evictable - test whether a page is evictable
3423 * @page: the page to test
3425 * Test whether page is evictable--i.e., should be placed on active/inactive
3426 * lists vs unevictable list.
3428 * Reasons page might not be evictable:
3429 * (1) page's mapping marked unevictable
3430 * (2) page is part of an mlocked VMA
3433 int page_evictable(struct page
*page
)
3435 return !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
3440 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3441 * @pages: array of pages to check
3442 * @nr_pages: number of pages to check
3444 * Checks pages for evictability and moves them to the appropriate lru list.
3446 * This function is only used for SysV IPC SHM_UNLOCK.
3448 void check_move_unevictable_pages(struct page
**pages
, int nr_pages
)
3450 struct lruvec
*lruvec
;
3451 struct zone
*zone
= NULL
;
3456 for (i
= 0; i
< nr_pages
; i
++) {
3457 struct page
*page
= pages
[i
];
3458 struct zone
*pagezone
;
3461 pagezone
= page_zone(page
);
3462 if (pagezone
!= zone
) {
3464 spin_unlock_irq(&zone
->lru_lock
);
3466 spin_lock_irq(&zone
->lru_lock
);
3468 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
3470 if (!PageLRU(page
) || !PageUnevictable(page
))
3473 if (page_evictable(page
)) {
3474 enum lru_list lru
= page_lru_base_type(page
);
3476 VM_BUG_ON(PageActive(page
));
3477 ClearPageUnevictable(page
);
3478 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
3479 add_page_to_lru_list(page
, lruvec
, lru
);
3485 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
3486 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
3487 spin_unlock_irq(&zone
->lru_lock
);
3490 #endif /* CONFIG_SHMEM */
3492 static void warn_scan_unevictable_pages(void)
3494 printk_once(KERN_WARNING
3495 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3496 "disabled for lack of a legitimate use case. If you have "
3497 "one, please send an email to linux-mm@kvack.org.\n",
3502 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3503 * all nodes' unevictable lists for evictable pages
3505 unsigned long scan_unevictable_pages
;
3507 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3508 void __user
*buffer
,
3509 size_t *length
, loff_t
*ppos
)
3511 warn_scan_unevictable_pages();
3512 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3513 scan_unevictable_pages
= 0;
3519 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3520 * a specified node's per zone unevictable lists for evictable pages.
3523 static ssize_t
read_scan_unevictable_node(struct device
*dev
,
3524 struct device_attribute
*attr
,
3527 warn_scan_unevictable_pages();
3528 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3531 static ssize_t
write_scan_unevictable_node(struct device
*dev
,
3532 struct device_attribute
*attr
,
3533 const char *buf
, size_t count
)
3535 warn_scan_unevictable_pages();
3540 static DEVICE_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3541 read_scan_unevictable_node
,
3542 write_scan_unevictable_node
);
3544 int scan_unevictable_register_node(struct node
*node
)
3546 return device_create_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);
3549 void scan_unevictable_unregister_node(struct node
*node
)
3551 device_remove_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);