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>
54 #define CREATE_TRACE_POINTS
55 #include <trace/events/vmscan.h>
58 /* Incremented by the number of inactive pages that were scanned */
59 unsigned long nr_scanned
;
61 /* Number of pages freed so far during a call to shrink_zones() */
62 unsigned long nr_reclaimed
;
64 /* How many pages shrink_list() should reclaim */
65 unsigned long nr_to_reclaim
;
67 unsigned long hibernation_mode
;
69 /* This context's GFP mask */
74 /* Can mapped pages be reclaimed? */
77 /* Can pages be swapped as part of reclaim? */
82 /* Scan (total_size >> priority) pages at once */
86 * The memory cgroup that hit its limit and as a result is the
87 * primary target of this reclaim invocation.
89 struct mem_cgroup
*target_mem_cgroup
;
92 * Nodemask of nodes allowed by the caller. If NULL, all nodes
98 #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
100 #ifdef ARCH_HAS_PREFETCH
101 #define prefetch_prev_lru_page(_page, _base, _field) \
103 if ((_page)->lru.prev != _base) { \
106 prev = lru_to_page(&(_page->lru)); \
107 prefetch(&prev->_field); \
111 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
114 #ifdef ARCH_HAS_PREFETCHW
115 #define prefetchw_prev_lru_page(_page, _base, _field) \
117 if ((_page)->lru.prev != _base) { \
120 prev = lru_to_page(&(_page->lru)); \
121 prefetchw(&prev->_field); \
125 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
129 * From 0 .. 100. Higher means more swappy.
131 int vm_swappiness
= 60;
132 unsigned long vm_total_pages
; /* The total number of pages which the VM controls */
134 static LIST_HEAD(shrinker_list
);
135 static DECLARE_RWSEM(shrinker_rwsem
);
138 static bool global_reclaim(struct scan_control
*sc
)
140 return !sc
->target_mem_cgroup
;
143 static bool global_reclaim(struct scan_control
*sc
)
149 static unsigned long get_lru_size(struct lruvec
*lruvec
, enum lru_list lru
)
151 if (!mem_cgroup_disabled())
152 return mem_cgroup_get_lru_size(lruvec
, lru
);
154 return zone_page_state(lruvec_zone(lruvec
), NR_LRU_BASE
+ lru
);
158 * Add a shrinker callback to be called from the vm
160 void register_shrinker(struct shrinker
*shrinker
)
162 atomic_long_set(&shrinker
->nr_in_batch
, 0);
163 down_write(&shrinker_rwsem
);
164 list_add_tail(&shrinker
->list
, &shrinker_list
);
165 up_write(&shrinker_rwsem
);
167 EXPORT_SYMBOL(register_shrinker
);
172 void unregister_shrinker(struct shrinker
*shrinker
)
174 down_write(&shrinker_rwsem
);
175 list_del(&shrinker
->list
);
176 up_write(&shrinker_rwsem
);
178 EXPORT_SYMBOL(unregister_shrinker
);
180 static inline int do_shrinker_shrink(struct shrinker
*shrinker
,
181 struct shrink_control
*sc
,
182 unsigned long nr_to_scan
)
184 sc
->nr_to_scan
= nr_to_scan
;
185 return (*shrinker
->shrink
)(shrinker
, sc
);
188 #define SHRINK_BATCH 128
190 * Call the shrink functions to age shrinkable caches
192 * Here we assume it costs one seek to replace a lru page and that it also
193 * takes a seek to recreate a cache object. With this in mind we age equal
194 * percentages of the lru and ageable caches. This should balance the seeks
195 * generated by these structures.
197 * If the vm encountered mapped pages on the LRU it increase the pressure on
198 * slab to avoid swapping.
200 * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
202 * `lru_pages' represents the number of on-LRU pages in all the zones which
203 * are eligible for the caller's allocation attempt. It is used for balancing
204 * slab reclaim versus page reclaim.
206 * Returns the number of slab objects which we shrunk.
208 unsigned long shrink_slab(struct shrink_control
*shrink
,
209 unsigned long nr_pages_scanned
,
210 unsigned long lru_pages
)
212 struct shrinker
*shrinker
;
213 unsigned long ret
= 0;
215 if (nr_pages_scanned
== 0)
216 nr_pages_scanned
= SWAP_CLUSTER_MAX
;
218 if (!down_read_trylock(&shrinker_rwsem
)) {
219 /* Assume we'll be able to shrink next time */
224 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
225 unsigned long long delta
;
231 long batch_size
= shrinker
->batch
? shrinker
->batch
234 max_pass
= do_shrinker_shrink(shrinker
, shrink
, 0);
239 * copy the current shrinker scan count into a local variable
240 * and zero it so that other concurrent shrinker invocations
241 * don't also do this scanning work.
243 nr
= atomic_long_xchg(&shrinker
->nr_in_batch
, 0);
246 delta
= (4 * nr_pages_scanned
) / shrinker
->seeks
;
248 do_div(delta
, lru_pages
+ 1);
250 if (total_scan
< 0) {
251 printk(KERN_ERR
"shrink_slab: %pF negative objects to "
253 shrinker
->shrink
, total_scan
);
254 total_scan
= max_pass
;
258 * We need to avoid excessive windup on filesystem shrinkers
259 * due to large numbers of GFP_NOFS allocations causing the
260 * shrinkers to return -1 all the time. This results in a large
261 * nr being built up so when a shrink that can do some work
262 * comes along it empties the entire cache due to nr >>>
263 * max_pass. This is bad for sustaining a working set in
266 * Hence only allow the shrinker to scan the entire cache when
267 * a large delta change is calculated directly.
269 if (delta
< max_pass
/ 4)
270 total_scan
= min(total_scan
, max_pass
/ 2);
273 * Avoid risking looping forever due to too large nr value:
274 * never try to free more than twice the estimate number of
277 if (total_scan
> max_pass
* 2)
278 total_scan
= max_pass
* 2;
280 trace_mm_shrink_slab_start(shrinker
, shrink
, nr
,
281 nr_pages_scanned
, lru_pages
,
282 max_pass
, delta
, total_scan
);
284 while (total_scan
>= batch_size
) {
287 nr_before
= do_shrinker_shrink(shrinker
, shrink
, 0);
288 shrink_ret
= do_shrinker_shrink(shrinker
, shrink
,
290 if (shrink_ret
== -1)
292 if (shrink_ret
< nr_before
)
293 ret
+= nr_before
- shrink_ret
;
294 count_vm_events(SLABS_SCANNED
, batch_size
);
295 total_scan
-= batch_size
;
301 * move the unused scan count back into the shrinker in a
302 * manner that handles concurrent updates. If we exhausted the
303 * scan, there is no need to do an update.
306 new_nr
= atomic_long_add_return(total_scan
,
307 &shrinker
->nr_in_batch
);
309 new_nr
= atomic_long_read(&shrinker
->nr_in_batch
);
311 trace_mm_shrink_slab_end(shrinker
, shrink_ret
, nr
, new_nr
);
313 up_read(&shrinker_rwsem
);
319 static inline int is_page_cache_freeable(struct page
*page
)
322 * A freeable page cache page is referenced only by the caller
323 * that isolated the page, the page cache radix tree and
324 * optional buffer heads at page->private.
326 return page_count(page
) - page_has_private(page
) == 2;
329 static int may_write_to_queue(struct backing_dev_info
*bdi
,
330 struct scan_control
*sc
)
332 if (current
->flags
& PF_SWAPWRITE
)
334 if (!bdi_write_congested(bdi
))
336 if (bdi
== current
->backing_dev_info
)
342 * We detected a synchronous write error writing a page out. Probably
343 * -ENOSPC. We need to propagate that into the address_space for a subsequent
344 * fsync(), msync() or close().
346 * The tricky part is that after writepage we cannot touch the mapping: nothing
347 * prevents it from being freed up. But we have a ref on the page and once
348 * that page is locked, the mapping is pinned.
350 * We're allowed to run sleeping lock_page() here because we know the caller has
353 static void handle_write_error(struct address_space
*mapping
,
354 struct page
*page
, int error
)
357 if (page_mapping(page
) == mapping
)
358 mapping_set_error(mapping
, error
);
362 /* possible outcome of pageout() */
364 /* failed to write page out, page is locked */
366 /* move page to the active list, page is locked */
368 /* page has been sent to the disk successfully, page is unlocked */
370 /* page is clean and locked */
375 * pageout is called by shrink_page_list() for each dirty page.
376 * Calls ->writepage().
378 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
379 struct scan_control
*sc
)
382 * If the page is dirty, only perform writeback if that write
383 * will be non-blocking. To prevent this allocation from being
384 * stalled by pagecache activity. But note that there may be
385 * stalls if we need to run get_block(). We could test
386 * PagePrivate for that.
388 * If this process is currently in __generic_file_aio_write() against
389 * this page's queue, we can perform writeback even if that
392 * If the page is swapcache, write it back even if that would
393 * block, for some throttling. This happens by accident, because
394 * swap_backing_dev_info is bust: it doesn't reflect the
395 * congestion state of the swapdevs. Easy to fix, if needed.
397 if (!is_page_cache_freeable(page
))
401 * Some data journaling orphaned pages can have
402 * page->mapping == NULL while being dirty with clean buffers.
404 if (page_has_private(page
)) {
405 if (try_to_free_buffers(page
)) {
406 ClearPageDirty(page
);
407 printk("%s: orphaned page\n", __func__
);
413 if (mapping
->a_ops
->writepage
== NULL
)
414 return PAGE_ACTIVATE
;
415 if (!may_write_to_queue(mapping
->backing_dev_info
, sc
))
418 if (clear_page_dirty_for_io(page
)) {
420 struct writeback_control wbc
= {
421 .sync_mode
= WB_SYNC_NONE
,
422 .nr_to_write
= SWAP_CLUSTER_MAX
,
424 .range_end
= LLONG_MAX
,
428 SetPageReclaim(page
);
429 res
= mapping
->a_ops
->writepage(page
, &wbc
);
431 handle_write_error(mapping
, page
, res
);
432 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
433 ClearPageReclaim(page
);
434 return PAGE_ACTIVATE
;
437 if (!PageWriteback(page
)) {
438 /* synchronous write or broken a_ops? */
439 ClearPageReclaim(page
);
441 trace_mm_vmscan_writepage(page
, trace_reclaim_flags(page
));
442 inc_zone_page_state(page
, NR_VMSCAN_WRITE
);
450 * Same as remove_mapping, but if the page is removed from the mapping, it
451 * gets returned with a refcount of 0.
453 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
)
455 BUG_ON(!PageLocked(page
));
456 BUG_ON(mapping
!= page_mapping(page
));
458 spin_lock_irq(&mapping
->tree_lock
);
460 * The non racy check for a busy page.
462 * Must be careful with the order of the tests. When someone has
463 * a ref to the page, it may be possible that they dirty it then
464 * drop the reference. So if PageDirty is tested before page_count
465 * here, then the following race may occur:
467 * get_user_pages(&page);
468 * [user mapping goes away]
470 * !PageDirty(page) [good]
471 * SetPageDirty(page);
473 * !page_count(page) [good, discard it]
475 * [oops, our write_to data is lost]
477 * Reversing the order of the tests ensures such a situation cannot
478 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
479 * load is not satisfied before that of page->_count.
481 * Note that if SetPageDirty is always performed via set_page_dirty,
482 * and thus under tree_lock, then this ordering is not required.
484 if (!page_freeze_refs(page
, 2))
486 /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
487 if (unlikely(PageDirty(page
))) {
488 page_unfreeze_refs(page
, 2);
492 if (PageSwapCache(page
)) {
493 swp_entry_t swap
= { .val
= page_private(page
) };
494 __delete_from_swap_cache(page
);
495 spin_unlock_irq(&mapping
->tree_lock
);
496 swapcache_free(swap
, page
);
498 void (*freepage
)(struct page
*);
500 freepage
= mapping
->a_ops
->freepage
;
502 __delete_from_page_cache(page
);
503 spin_unlock_irq(&mapping
->tree_lock
);
504 mem_cgroup_uncharge_cache_page(page
);
506 if (freepage
!= NULL
)
513 spin_unlock_irq(&mapping
->tree_lock
);
518 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
519 * someone else has a ref on the page, abort and return 0. If it was
520 * successfully detached, return 1. Assumes the caller has a single ref on
523 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
525 if (__remove_mapping(mapping
, page
)) {
527 * Unfreezing the refcount with 1 rather than 2 effectively
528 * drops the pagecache ref for us without requiring another
531 page_unfreeze_refs(page
, 1);
538 * putback_lru_page - put previously isolated page onto appropriate LRU list
539 * @page: page to be put back to appropriate lru list
541 * Add previously isolated @page to appropriate LRU list.
542 * Page may still be unevictable for other reasons.
544 * lru_lock must not be held, interrupts must be enabled.
546 void putback_lru_page(struct page
*page
)
549 int active
= !!TestClearPageActive(page
);
550 int was_unevictable
= PageUnevictable(page
);
552 VM_BUG_ON(PageLRU(page
));
555 ClearPageUnevictable(page
);
557 if (page_evictable(page
)) {
559 * For evictable pages, we can use the cache.
560 * In event of a race, worst case is we end up with an
561 * unevictable page on [in]active list.
562 * We know how to handle that.
564 lru
= active
+ page_lru_base_type(page
);
565 lru_cache_add_lru(page
, lru
);
568 * Put unevictable pages directly on zone's unevictable
571 lru
= LRU_UNEVICTABLE
;
572 add_page_to_unevictable_list(page
);
574 * When racing with an mlock or AS_UNEVICTABLE clearing
575 * (page is unlocked) make sure that if the other thread
576 * does not observe our setting of PG_lru and fails
577 * isolation/check_move_unevictable_pages,
578 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
579 * the page back to the evictable list.
581 * The other side is TestClearPageMlocked() or shmem_lock().
587 * page's status can change while we move it among lru. If an evictable
588 * page is on unevictable list, it never be freed. To avoid that,
589 * check after we added it to the list, again.
591 if (lru
== LRU_UNEVICTABLE
&& page_evictable(page
)) {
592 if (!isolate_lru_page(page
)) {
596 /* This means someone else dropped this page from LRU
597 * So, it will be freed or putback to LRU again. There is
598 * nothing to do here.
602 if (was_unevictable
&& lru
!= LRU_UNEVICTABLE
)
603 count_vm_event(UNEVICTABLE_PGRESCUED
);
604 else if (!was_unevictable
&& lru
== LRU_UNEVICTABLE
)
605 count_vm_event(UNEVICTABLE_PGCULLED
);
607 put_page(page
); /* drop ref from isolate */
610 enum page_references
{
612 PAGEREF_RECLAIM_CLEAN
,
617 static enum page_references
page_check_references(struct page
*page
,
618 struct scan_control
*sc
)
620 int referenced_ptes
, referenced_page
;
621 unsigned long vm_flags
;
623 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
625 referenced_page
= TestClearPageReferenced(page
);
628 * Mlock lost the isolation race with us. Let try_to_unmap()
629 * move the page to the unevictable list.
631 if (vm_flags
& VM_LOCKED
)
632 return PAGEREF_RECLAIM
;
634 if (referenced_ptes
) {
635 if (PageSwapBacked(page
))
636 return PAGEREF_ACTIVATE
;
638 * All mapped pages start out with page table
639 * references from the instantiating fault, so we need
640 * to look twice if a mapped file page is used more
643 * Mark it and spare it for another trip around the
644 * inactive list. Another page table reference will
645 * lead to its activation.
647 * Note: the mark is set for activated pages as well
648 * so that recently deactivated but used pages are
651 SetPageReferenced(page
);
653 if (referenced_page
|| referenced_ptes
> 1)
654 return PAGEREF_ACTIVATE
;
657 * Activate file-backed executable pages after first usage.
659 if (vm_flags
& VM_EXEC
)
660 return PAGEREF_ACTIVATE
;
665 /* Reclaim if clean, defer dirty pages to writeback */
666 if (referenced_page
&& !PageSwapBacked(page
))
667 return PAGEREF_RECLAIM_CLEAN
;
669 return PAGEREF_RECLAIM
;
673 * shrink_page_list() returns the number of reclaimed pages
675 static unsigned long shrink_page_list(struct list_head
*page_list
,
677 struct scan_control
*sc
,
678 enum ttu_flags ttu_flags
,
679 unsigned long *ret_nr_unqueued_dirty
,
680 unsigned long *ret_nr_writeback
,
683 LIST_HEAD(ret_pages
);
684 LIST_HEAD(free_pages
);
686 unsigned long nr_unqueued_dirty
= 0;
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
));
728 * If a page at the tail of the LRU is under writeback, there
729 * are three cases to consider.
731 * 1) If reclaim is encountering an excessive number of pages
732 * under writeback and this page is both under writeback and
733 * PageReclaim then it indicates that pages are being queued
734 * for IO but are being recycled through the LRU before the
735 * IO can complete. Waiting on the page itself risks an
736 * indefinite stall if it is impossible to writeback the
737 * page due to IO error or disconnected storage so instead
738 * block for HZ/10 or until some IO completes then clear the
739 * ZONE_WRITEBACK flag to recheck if the condition exists.
741 * 2) Global reclaim encounters a page, memcg encounters a
742 * page that is not marked for immediate reclaim or
743 * the caller does not have __GFP_IO. In this case mark
744 * the page for immediate reclaim and continue scanning.
746 * __GFP_IO is checked because a loop driver thread might
747 * enter reclaim, and deadlock if it waits on a page for
748 * which it is needed to do the write (loop masks off
749 * __GFP_IO|__GFP_FS for this reason); but more thought
750 * would probably show more reasons.
752 * Don't require __GFP_FS, since we're not going into the
753 * FS, just waiting on its writeback completion. Worryingly,
754 * ext4 gfs2 and xfs allocate pages with
755 * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing
756 * may_enter_fs here is liable to OOM on them.
758 * 3) memcg encounters a page that is not already marked
759 * PageReclaim. memcg does not have any dirty pages
760 * throttling so we could easily OOM just because too many
761 * pages are in writeback and there is nothing else to
762 * reclaim. Wait for the writeback to complete.
764 if (PageWriteback(page
)) {
766 if (current_is_kswapd() &&
768 zone_is_reclaim_writeback(zone
)) {
770 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
771 zone_clear_flag(zone
, ZONE_WRITEBACK
);
775 } else if (global_reclaim(sc
) ||
776 !PageReclaim(page
) || !(sc
->gfp_mask
& __GFP_IO
)) {
778 * This is slightly racy - end_page_writeback()
779 * might have just cleared PageReclaim, then
780 * setting PageReclaim here end up interpreted
781 * as PageReadahead - but that does not matter
782 * enough to care. What we do want is for this
783 * page to have PageReclaim set next time memcg
784 * reclaim reaches the tests above, so it will
785 * then wait_on_page_writeback() to avoid OOM;
786 * and it's also appropriate in global reclaim.
788 SetPageReclaim(page
);
795 wait_on_page_writeback(page
);
800 references
= page_check_references(page
, sc
);
802 switch (references
) {
803 case PAGEREF_ACTIVATE
:
804 goto activate_locked
;
807 case PAGEREF_RECLAIM
:
808 case PAGEREF_RECLAIM_CLEAN
:
809 ; /* try to reclaim the page below */
813 * Anonymous process memory has backing store?
814 * Try to allocate it some swap space here.
816 if (PageAnon(page
) && !PageSwapCache(page
)) {
817 if (!(sc
->gfp_mask
& __GFP_IO
))
819 if (!add_to_swap(page
, page_list
))
820 goto activate_locked
;
824 mapping
= page_mapping(page
);
827 * The page is mapped into the page tables of one or more
828 * processes. Try to unmap it here.
830 if (page_mapped(page
) && mapping
) {
831 switch (try_to_unmap(page
, ttu_flags
)) {
833 goto activate_locked
;
839 ; /* try to free the page below */
843 if (PageDirty(page
)) {
846 if (!PageWriteback(page
))
850 * Only kswapd can writeback filesystem pages to
851 * avoid risk of stack overflow but only writeback
852 * if many dirty pages have been encountered.
854 if (page_is_file_cache(page
) &&
855 (!current_is_kswapd() ||
856 !zone_is_reclaim_dirty(zone
))) {
858 * Immediately reclaim when written back.
859 * Similar in principal to deactivate_page()
860 * except we already have the page isolated
861 * and know it's dirty
863 inc_zone_page_state(page
, NR_VMSCAN_IMMEDIATE
);
864 SetPageReclaim(page
);
869 if (references
== PAGEREF_RECLAIM_CLEAN
)
873 if (!sc
->may_writepage
)
876 /* Page is dirty, try to write it out here */
877 switch (pageout(page
, mapping
, sc
)) {
882 goto activate_locked
;
884 if (PageWriteback(page
))
890 * A synchronous write - probably a ramdisk. Go
891 * ahead and try to reclaim the page.
893 if (!trylock_page(page
))
895 if (PageDirty(page
) || PageWriteback(page
))
897 mapping
= page_mapping(page
);
899 ; /* try to free the page below */
904 * If the page has buffers, try to free the buffer mappings
905 * associated with this page. If we succeed we try to free
908 * We do this even if the page is PageDirty().
909 * try_to_release_page() does not perform I/O, but it is
910 * possible for a page to have PageDirty set, but it is actually
911 * clean (all its buffers are clean). This happens if the
912 * buffers were written out directly, with submit_bh(). ext3
913 * will do this, as well as the blockdev mapping.
914 * try_to_release_page() will discover that cleanness and will
915 * drop the buffers and mark the page clean - it can be freed.
917 * Rarely, pages can have buffers and no ->mapping. These are
918 * the pages which were not successfully invalidated in
919 * truncate_complete_page(). We try to drop those buffers here
920 * and if that worked, and the page is no longer mapped into
921 * process address space (page_count == 1) it can be freed.
922 * Otherwise, leave the page on the LRU so it is swappable.
924 if (page_has_private(page
)) {
925 if (!try_to_release_page(page
, sc
->gfp_mask
))
926 goto activate_locked
;
927 if (!mapping
&& page_count(page
) == 1) {
929 if (put_page_testzero(page
))
933 * rare race with speculative reference.
934 * the speculative reference will free
935 * this page shortly, so we may
936 * increment nr_reclaimed here (and
937 * leave it off the LRU).
945 if (!mapping
|| !__remove_mapping(mapping
, page
))
949 * At this point, we have no other references and there is
950 * no way to pick any more up (removed from LRU, removed
951 * from pagecache). Can use non-atomic bitops now (and
952 * we obviously don't have to worry about waking up a process
953 * waiting on the page lock, because there are no references.
955 __clear_page_locked(page
);
960 * Is there need to periodically free_page_list? It would
961 * appear not as the counts should be low
963 list_add(&page
->lru
, &free_pages
);
967 if (PageSwapCache(page
))
968 try_to_free_swap(page
);
970 putback_lru_page(page
);
974 /* Not a candidate for swapping, so reclaim swap space. */
975 if (PageSwapCache(page
) && vm_swap_full())
976 try_to_free_swap(page
);
977 VM_BUG_ON(PageActive(page
));
983 list_add(&page
->lru
, &ret_pages
);
984 VM_BUG_ON(PageLRU(page
) || PageUnevictable(page
));
988 * Tag a zone as congested if all the dirty pages encountered were
989 * backed by a congested BDI. In this case, reclaimers should just
990 * back off and wait for congestion to clear because further reclaim
991 * will encounter the same problem
993 if (nr_dirty
&& nr_dirty
== nr_congested
&& global_reclaim(sc
))
994 zone_set_flag(zone
, ZONE_CONGESTED
);
996 free_hot_cold_page_list(&free_pages
, 1);
998 list_splice(&ret_pages
, page_list
);
999 count_vm_events(PGACTIVATE
, pgactivate
);
1000 mem_cgroup_uncharge_end();
1001 *ret_nr_unqueued_dirty
+= nr_unqueued_dirty
;
1002 *ret_nr_writeback
+= nr_writeback
;
1003 return nr_reclaimed
;
1006 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1007 struct list_head
*page_list
)
1009 struct scan_control sc
= {
1010 .gfp_mask
= GFP_KERNEL
,
1011 .priority
= DEF_PRIORITY
,
1014 unsigned long ret
, dummy1
, dummy2
;
1015 struct page
*page
, *next
;
1016 LIST_HEAD(clean_pages
);
1018 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1019 if (page_is_file_cache(page
) && !PageDirty(page
)) {
1020 ClearPageActive(page
);
1021 list_move(&page
->lru
, &clean_pages
);
1025 ret
= shrink_page_list(&clean_pages
, zone
, &sc
,
1026 TTU_UNMAP
|TTU_IGNORE_ACCESS
,
1027 &dummy1
, &dummy2
, true);
1028 list_splice(&clean_pages
, page_list
);
1029 __mod_zone_page_state(zone
, NR_ISOLATED_FILE
, -ret
);
1034 * Attempt to remove the specified page from its LRU. Only take this page
1035 * if it is of the appropriate PageActive status. Pages which are being
1036 * freed elsewhere are also ignored.
1038 * page: page to consider
1039 * mode: one of the LRU isolation modes defined above
1041 * returns 0 on success, -ve errno on failure.
1043 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1047 /* Only take pages on the LRU. */
1051 /* Compaction should not handle unevictable pages but CMA can do so */
1052 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1058 * To minimise LRU disruption, the caller can indicate that it only
1059 * wants to isolate pages it will be able to operate on without
1060 * blocking - clean pages for the most part.
1062 * ISOLATE_CLEAN means that only clean pages should be isolated. This
1063 * is used by reclaim when it is cannot write to backing storage
1065 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1066 * that it is possible to migrate without blocking
1068 if (mode
& (ISOLATE_CLEAN
|ISOLATE_ASYNC_MIGRATE
)) {
1069 /* All the caller can do on PageWriteback is block */
1070 if (PageWriteback(page
))
1073 if (PageDirty(page
)) {
1074 struct address_space
*mapping
;
1076 /* ISOLATE_CLEAN means only clean pages */
1077 if (mode
& ISOLATE_CLEAN
)
1081 * Only pages without mappings or that have a
1082 * ->migratepage callback are possible to migrate
1085 mapping
= page_mapping(page
);
1086 if (mapping
&& !mapping
->a_ops
->migratepage
)
1091 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1094 if (likely(get_page_unless_zero(page
))) {
1096 * Be careful not to clear PageLRU until after we're
1097 * sure the page is not being freed elsewhere -- the
1098 * page release code relies on it.
1108 * zone->lru_lock is heavily contended. Some of the functions that
1109 * shrink the lists perform better by taking out a batch of pages
1110 * and working on them outside the LRU lock.
1112 * For pagecache intensive workloads, this function is the hottest
1113 * spot in the kernel (apart from copy_*_user functions).
1115 * Appropriate locks must be held before calling this function.
1117 * @nr_to_scan: The number of pages to look through on the list.
1118 * @lruvec: The LRU vector to pull pages from.
1119 * @dst: The temp list to put pages on to.
1120 * @nr_scanned: The number of pages that were scanned.
1121 * @sc: The scan_control struct for this reclaim session
1122 * @mode: One of the LRU isolation modes
1123 * @lru: LRU list id for isolating
1125 * returns how many pages were moved onto *@dst.
1127 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1128 struct lruvec
*lruvec
, struct list_head
*dst
,
1129 unsigned long *nr_scanned
, struct scan_control
*sc
,
1130 isolate_mode_t mode
, enum lru_list lru
)
1132 struct list_head
*src
= &lruvec
->lists
[lru
];
1133 unsigned long nr_taken
= 0;
1136 for (scan
= 0; scan
< nr_to_scan
&& !list_empty(src
); scan
++) {
1140 page
= lru_to_page(src
);
1141 prefetchw_prev_lru_page(page
, src
, flags
);
1143 VM_BUG_ON(!PageLRU(page
));
1145 switch (__isolate_lru_page(page
, mode
)) {
1147 nr_pages
= hpage_nr_pages(page
);
1148 mem_cgroup_update_lru_size(lruvec
, lru
, -nr_pages
);
1149 list_move(&page
->lru
, dst
);
1150 nr_taken
+= nr_pages
;
1154 /* else it is being freed elsewhere */
1155 list_move(&page
->lru
, src
);
1164 trace_mm_vmscan_lru_isolate(sc
->order
, nr_to_scan
, scan
,
1165 nr_taken
, mode
, is_file_lru(lru
));
1170 * isolate_lru_page - tries to isolate a page from its LRU list
1171 * @page: page to isolate from its LRU list
1173 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1174 * vmstat statistic corresponding to whatever LRU list the page was on.
1176 * Returns 0 if the page was removed from an LRU list.
1177 * Returns -EBUSY if the page was not on an LRU list.
1179 * The returned page will have PageLRU() cleared. If it was found on
1180 * the active list, it will have PageActive set. If it was found on
1181 * the unevictable list, it will have the PageUnevictable bit set. That flag
1182 * may need to be cleared by the caller before letting the page go.
1184 * The vmstat statistic corresponding to the list on which the page was
1185 * found will be decremented.
1188 * (1) Must be called with an elevated refcount on the page. This is a
1189 * fundamentnal difference from isolate_lru_pages (which is called
1190 * without a stable reference).
1191 * (2) the lru_lock must not be held.
1192 * (3) interrupts must be enabled.
1194 int isolate_lru_page(struct page
*page
)
1198 VM_BUG_ON(!page_count(page
));
1200 if (PageLRU(page
)) {
1201 struct zone
*zone
= page_zone(page
);
1202 struct lruvec
*lruvec
;
1204 spin_lock_irq(&zone
->lru_lock
);
1205 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1206 if (PageLRU(page
)) {
1207 int lru
= page_lru(page
);
1210 del_page_from_lru_list(page
, lruvec
, lru
);
1213 spin_unlock_irq(&zone
->lru_lock
);
1219 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1220 * then get resheduled. When there are massive number of tasks doing page
1221 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1222 * the LRU list will go small and be scanned faster than necessary, leading to
1223 * unnecessary swapping, thrashing and OOM.
1225 static int too_many_isolated(struct zone
*zone
, int file
,
1226 struct scan_control
*sc
)
1228 unsigned long inactive
, isolated
;
1230 if (current_is_kswapd())
1233 if (!global_reclaim(sc
))
1237 inactive
= zone_page_state(zone
, NR_INACTIVE_FILE
);
1238 isolated
= zone_page_state(zone
, NR_ISOLATED_FILE
);
1240 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1241 isolated
= zone_page_state(zone
, NR_ISOLATED_ANON
);
1245 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1246 * won't get blocked by normal direct-reclaimers, forming a circular
1249 if ((sc
->gfp_mask
& GFP_IOFS
) == GFP_IOFS
)
1252 return isolated
> inactive
;
1255 static noinline_for_stack
void
1256 putback_inactive_pages(struct lruvec
*lruvec
, struct list_head
*page_list
)
1258 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1259 struct zone
*zone
= lruvec_zone(lruvec
);
1260 LIST_HEAD(pages_to_free
);
1263 * Put back any unfreeable pages.
1265 while (!list_empty(page_list
)) {
1266 struct page
*page
= lru_to_page(page_list
);
1269 VM_BUG_ON(PageLRU(page
));
1270 list_del(&page
->lru
);
1271 if (unlikely(!page_evictable(page
))) {
1272 spin_unlock_irq(&zone
->lru_lock
);
1273 putback_lru_page(page
);
1274 spin_lock_irq(&zone
->lru_lock
);
1278 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1281 lru
= page_lru(page
);
1282 add_page_to_lru_list(page
, lruvec
, lru
);
1284 if (is_active_lru(lru
)) {
1285 int file
= is_file_lru(lru
);
1286 int numpages
= hpage_nr_pages(page
);
1287 reclaim_stat
->recent_rotated
[file
] += numpages
;
1289 if (put_page_testzero(page
)) {
1290 __ClearPageLRU(page
);
1291 __ClearPageActive(page
);
1292 del_page_from_lru_list(page
, lruvec
, lru
);
1294 if (unlikely(PageCompound(page
))) {
1295 spin_unlock_irq(&zone
->lru_lock
);
1296 (*get_compound_page_dtor(page
))(page
);
1297 spin_lock_irq(&zone
->lru_lock
);
1299 list_add(&page
->lru
, &pages_to_free
);
1304 * To save our caller's stack, now use input list for pages to free.
1306 list_splice(&pages_to_free
, page_list
);
1310 * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
1311 * of reclaimed pages
1313 static noinline_for_stack
unsigned long
1314 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1315 struct scan_control
*sc
, enum lru_list lru
)
1317 LIST_HEAD(page_list
);
1318 unsigned long nr_scanned
;
1319 unsigned long nr_reclaimed
= 0;
1320 unsigned long nr_taken
;
1321 unsigned long nr_dirty
= 0;
1322 unsigned long nr_writeback
= 0;
1323 isolate_mode_t isolate_mode
= 0;
1324 int file
= is_file_lru(lru
);
1325 struct zone
*zone
= lruvec_zone(lruvec
);
1326 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1328 while (unlikely(too_many_isolated(zone
, file
, sc
))) {
1329 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
1331 /* We are about to die and free our memory. Return now. */
1332 if (fatal_signal_pending(current
))
1333 return SWAP_CLUSTER_MAX
;
1339 isolate_mode
|= ISOLATE_UNMAPPED
;
1340 if (!sc
->may_writepage
)
1341 isolate_mode
|= ISOLATE_CLEAN
;
1343 spin_lock_irq(&zone
->lru_lock
);
1345 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1346 &nr_scanned
, sc
, isolate_mode
, lru
);
1348 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1349 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1351 if (global_reclaim(sc
)) {
1352 zone
->pages_scanned
+= nr_scanned
;
1353 if (current_is_kswapd())
1354 __count_zone_vm_events(PGSCAN_KSWAPD
, zone
, nr_scanned
);
1356 __count_zone_vm_events(PGSCAN_DIRECT
, zone
, nr_scanned
);
1358 spin_unlock_irq(&zone
->lru_lock
);
1363 nr_reclaimed
= shrink_page_list(&page_list
, zone
, sc
, TTU_UNMAP
,
1364 &nr_dirty
, &nr_writeback
, false);
1366 spin_lock_irq(&zone
->lru_lock
);
1368 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1370 if (global_reclaim(sc
)) {
1371 if (current_is_kswapd())
1372 __count_zone_vm_events(PGSTEAL_KSWAPD
, zone
,
1375 __count_zone_vm_events(PGSTEAL_DIRECT
, zone
,
1379 putback_inactive_pages(lruvec
, &page_list
);
1381 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1383 spin_unlock_irq(&zone
->lru_lock
);
1385 free_hot_cold_page_list(&page_list
, 1);
1388 * If reclaim is isolating dirty pages under writeback, it implies
1389 * that the long-lived page allocation rate is exceeding the page
1390 * laundering rate. Either the global limits are not being effective
1391 * at throttling processes due to the page distribution throughout
1392 * zones or there is heavy usage of a slow backing device. The
1393 * only option is to throttle from reclaim context which is not ideal
1394 * as there is no guarantee the dirtying process is throttled in the
1395 * same way balance_dirty_pages() manages.
1397 * This scales the number of dirty pages that must be under writeback
1398 * before throttling depending on priority. It is a simple backoff
1399 * function that has the most effect in the range DEF_PRIORITY to
1400 * DEF_PRIORITY-2 which is the priority reclaim is considered to be
1401 * in trouble and reclaim is considered to be in trouble.
1403 * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
1404 * DEF_PRIORITY-1 50% must be PageWriteback
1405 * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
1407 * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
1408 * isolated page is PageWriteback
1410 if (nr_writeback
&& nr_writeback
>=
1411 (nr_taken
>> (DEF_PRIORITY
- sc
->priority
))) {
1412 wait_iff_congested(zone
, BLK_RW_ASYNC
, HZ
/10);
1413 zone_set_flag(zone
, ZONE_WRITEBACK
);
1417 * Similarly, if many dirty pages are encountered that are not
1418 * currently being written then flag that kswapd should start
1419 * writing back pages.
1421 if (global_reclaim(sc
) && nr_dirty
&&
1422 nr_dirty
>= (nr_taken
>> (DEF_PRIORITY
- sc
->priority
)))
1423 zone_set_flag(zone
, ZONE_TAIL_LRU_DIRTY
);
1425 trace_mm_vmscan_lru_shrink_inactive(zone
->zone_pgdat
->node_id
,
1427 nr_scanned
, nr_reclaimed
,
1429 trace_shrink_flags(file
));
1430 return nr_reclaimed
;
1434 * This moves pages from the active list to the inactive list.
1436 * We move them the other way if the page is referenced by one or more
1437 * processes, from rmap.
1439 * If the pages are mostly unmapped, the processing is fast and it is
1440 * appropriate to hold zone->lru_lock across the whole operation. But if
1441 * the pages are mapped, the processing is slow (page_referenced()) so we
1442 * should drop zone->lru_lock around each page. It's impossible to balance
1443 * this, so instead we remove the pages from the LRU while processing them.
1444 * It is safe to rely on PG_active against the non-LRU pages in here because
1445 * nobody will play with that bit on a non-LRU page.
1447 * The downside is that we have to touch page->_count against each page.
1448 * But we had to alter page->flags anyway.
1451 static void move_active_pages_to_lru(struct lruvec
*lruvec
,
1452 struct list_head
*list
,
1453 struct list_head
*pages_to_free
,
1456 struct zone
*zone
= lruvec_zone(lruvec
);
1457 unsigned long pgmoved
= 0;
1461 while (!list_empty(list
)) {
1462 page
= lru_to_page(list
);
1463 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
1465 VM_BUG_ON(PageLRU(page
));
1468 nr_pages
= hpage_nr_pages(page
);
1469 mem_cgroup_update_lru_size(lruvec
, lru
, nr_pages
);
1470 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1471 pgmoved
+= nr_pages
;
1473 if (put_page_testzero(page
)) {
1474 __ClearPageLRU(page
);
1475 __ClearPageActive(page
);
1476 del_page_from_lru_list(page
, lruvec
, lru
);
1478 if (unlikely(PageCompound(page
))) {
1479 spin_unlock_irq(&zone
->lru_lock
);
1480 (*get_compound_page_dtor(page
))(page
);
1481 spin_lock_irq(&zone
->lru_lock
);
1483 list_add(&page
->lru
, pages_to_free
);
1486 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, pgmoved
);
1487 if (!is_active_lru(lru
))
1488 __count_vm_events(PGDEACTIVATE
, pgmoved
);
1491 static void shrink_active_list(unsigned long nr_to_scan
,
1492 struct lruvec
*lruvec
,
1493 struct scan_control
*sc
,
1496 unsigned long nr_taken
;
1497 unsigned long nr_scanned
;
1498 unsigned long vm_flags
;
1499 LIST_HEAD(l_hold
); /* The pages which were snipped off */
1500 LIST_HEAD(l_active
);
1501 LIST_HEAD(l_inactive
);
1503 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1504 unsigned long nr_rotated
= 0;
1505 isolate_mode_t isolate_mode
= 0;
1506 int file
= is_file_lru(lru
);
1507 struct zone
*zone
= lruvec_zone(lruvec
);
1512 isolate_mode
|= ISOLATE_UNMAPPED
;
1513 if (!sc
->may_writepage
)
1514 isolate_mode
|= ISOLATE_CLEAN
;
1516 spin_lock_irq(&zone
->lru_lock
);
1518 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
1519 &nr_scanned
, sc
, isolate_mode
, lru
);
1520 if (global_reclaim(sc
))
1521 zone
->pages_scanned
+= nr_scanned
;
1523 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1525 __count_zone_vm_events(PGREFILL
, zone
, nr_scanned
);
1526 __mod_zone_page_state(zone
, NR_LRU_BASE
+ lru
, -nr_taken
);
1527 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1528 spin_unlock_irq(&zone
->lru_lock
);
1530 while (!list_empty(&l_hold
)) {
1532 page
= lru_to_page(&l_hold
);
1533 list_del(&page
->lru
);
1535 if (unlikely(!page_evictable(page
))) {
1536 putback_lru_page(page
);
1540 if (unlikely(buffer_heads_over_limit
)) {
1541 if (page_has_private(page
) && trylock_page(page
)) {
1542 if (page_has_private(page
))
1543 try_to_release_page(page
, 0);
1548 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
1550 nr_rotated
+= hpage_nr_pages(page
);
1552 * Identify referenced, file-backed active pages and
1553 * give them one more trip around the active list. So
1554 * that executable code get better chances to stay in
1555 * memory under moderate memory pressure. Anon pages
1556 * are not likely to be evicted by use-once streaming
1557 * IO, plus JVM can create lots of anon VM_EXEC pages,
1558 * so we ignore them here.
1560 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
1561 list_add(&page
->lru
, &l_active
);
1566 ClearPageActive(page
); /* we are de-activating */
1567 list_add(&page
->lru
, &l_inactive
);
1571 * Move pages back to the lru list.
1573 spin_lock_irq(&zone
->lru_lock
);
1575 * Count referenced pages from currently used mappings as rotated,
1576 * even though only some of them are actually re-activated. This
1577 * helps balance scan pressure between file and anonymous pages in
1580 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
1582 move_active_pages_to_lru(lruvec
, &l_active
, &l_hold
, lru
);
1583 move_active_pages_to_lru(lruvec
, &l_inactive
, &l_hold
, lru
- LRU_ACTIVE
);
1584 __mod_zone_page_state(zone
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
1585 spin_unlock_irq(&zone
->lru_lock
);
1587 free_hot_cold_page_list(&l_hold
, 1);
1591 static int inactive_anon_is_low_global(struct zone
*zone
)
1593 unsigned long active
, inactive
;
1595 active
= zone_page_state(zone
, NR_ACTIVE_ANON
);
1596 inactive
= zone_page_state(zone
, NR_INACTIVE_ANON
);
1598 if (inactive
* zone
->inactive_ratio
< active
)
1605 * inactive_anon_is_low - check if anonymous pages need to be deactivated
1606 * @lruvec: LRU vector to check
1608 * Returns true if the zone does not have enough inactive anon pages,
1609 * meaning some active anon pages need to be deactivated.
1611 static int inactive_anon_is_low(struct lruvec
*lruvec
)
1614 * If we don't have swap space, anonymous page deactivation
1617 if (!total_swap_pages
)
1620 if (!mem_cgroup_disabled())
1621 return mem_cgroup_inactive_anon_is_low(lruvec
);
1623 return inactive_anon_is_low_global(lruvec_zone(lruvec
));
1626 static inline int inactive_anon_is_low(struct lruvec
*lruvec
)
1633 * inactive_file_is_low - check if file pages need to be deactivated
1634 * @lruvec: LRU vector to check
1636 * When the system is doing streaming IO, memory pressure here
1637 * ensures that active file pages get deactivated, until more
1638 * than half of the file pages are on the inactive list.
1640 * Once we get to that situation, protect the system's working
1641 * set from being evicted by disabling active file page aging.
1643 * This uses a different ratio than the anonymous pages, because
1644 * the page cache uses a use-once replacement algorithm.
1646 static int inactive_file_is_low(struct lruvec
*lruvec
)
1648 unsigned long inactive
;
1649 unsigned long active
;
1651 inactive
= get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1652 active
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
);
1654 return active
> inactive
;
1657 static int inactive_list_is_low(struct lruvec
*lruvec
, enum lru_list lru
)
1659 if (is_file_lru(lru
))
1660 return inactive_file_is_low(lruvec
);
1662 return inactive_anon_is_low(lruvec
);
1665 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
1666 struct lruvec
*lruvec
, struct scan_control
*sc
)
1668 if (is_active_lru(lru
)) {
1669 if (inactive_list_is_low(lruvec
, lru
))
1670 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
1674 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
1677 static int vmscan_swappiness(struct scan_control
*sc
)
1679 if (global_reclaim(sc
))
1680 return vm_swappiness
;
1681 return mem_cgroup_swappiness(sc
->target_mem_cgroup
);
1692 * Determine how aggressively the anon and file LRU lists should be
1693 * scanned. The relative value of each set of LRU lists is determined
1694 * by looking at the fraction of the pages scanned we did rotate back
1695 * onto the active list instead of evict.
1697 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
1698 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
1700 static void get_scan_count(struct lruvec
*lruvec
, struct scan_control
*sc
,
1703 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1705 u64 denominator
= 0; /* gcc */
1706 struct zone
*zone
= lruvec_zone(lruvec
);
1707 unsigned long anon_prio
, file_prio
;
1708 enum scan_balance scan_balance
;
1709 unsigned long anon
, file
, free
;
1710 bool force_scan
= false;
1711 unsigned long ap
, fp
;
1715 * If the zone or memcg is small, nr[l] can be 0. This
1716 * results in no scanning on this priority and a potential
1717 * priority drop. Global direct reclaim can go to the next
1718 * zone and tends to have no problems. Global kswapd is for
1719 * zone balancing and it needs to scan a minimum amount. When
1720 * reclaiming for a memcg, a priority drop can cause high
1721 * latencies, so it's better to scan a minimum amount there as
1724 if (current_is_kswapd() && zone
->all_unreclaimable
)
1726 if (!global_reclaim(sc
))
1729 /* If we have no swap space, do not bother scanning anon pages. */
1730 if (!sc
->may_swap
|| (get_nr_swap_pages() <= 0)) {
1731 scan_balance
= SCAN_FILE
;
1736 * Global reclaim will swap to prevent OOM even with no
1737 * swappiness, but memcg users want to use this knob to
1738 * disable swapping for individual groups completely when
1739 * using the memory controller's swap limit feature would be
1742 if (!global_reclaim(sc
) && !vmscan_swappiness(sc
)) {
1743 scan_balance
= SCAN_FILE
;
1748 * Do not apply any pressure balancing cleverness when the
1749 * system is close to OOM, scan both anon and file equally
1750 * (unless the swappiness setting disagrees with swapping).
1752 if (!sc
->priority
&& vmscan_swappiness(sc
)) {
1753 scan_balance
= SCAN_EQUAL
;
1757 anon
= get_lru_size(lruvec
, LRU_ACTIVE_ANON
) +
1758 get_lru_size(lruvec
, LRU_INACTIVE_ANON
);
1759 file
= get_lru_size(lruvec
, LRU_ACTIVE_FILE
) +
1760 get_lru_size(lruvec
, LRU_INACTIVE_FILE
);
1763 * If it's foreseeable that reclaiming the file cache won't be
1764 * enough to get the zone back into a desirable shape, we have
1765 * to swap. Better start now and leave the - probably heavily
1766 * thrashing - remaining file pages alone.
1768 if (global_reclaim(sc
)) {
1769 free
= zone_page_state(zone
, NR_FREE_PAGES
);
1770 if (unlikely(file
+ free
<= high_wmark_pages(zone
))) {
1771 scan_balance
= SCAN_ANON
;
1777 * There is enough inactive page cache, do not reclaim
1778 * anything from the anonymous working set right now.
1780 if (!inactive_file_is_low(lruvec
)) {
1781 scan_balance
= SCAN_FILE
;
1785 scan_balance
= SCAN_FRACT
;
1788 * With swappiness at 100, anonymous and file have the same priority.
1789 * This scanning priority is essentially the inverse of IO cost.
1791 anon_prio
= vmscan_swappiness(sc
);
1792 file_prio
= 200 - anon_prio
;
1795 * OK, so we have swap space and a fair amount of page cache
1796 * pages. We use the recently rotated / recently scanned
1797 * ratios to determine how valuable each cache is.
1799 * Because workloads change over time (and to avoid overflow)
1800 * we keep these statistics as a floating average, which ends
1801 * up weighing recent references more than old ones.
1803 * anon in [0], file in [1]
1805 spin_lock_irq(&zone
->lru_lock
);
1806 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
1807 reclaim_stat
->recent_scanned
[0] /= 2;
1808 reclaim_stat
->recent_rotated
[0] /= 2;
1811 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
1812 reclaim_stat
->recent_scanned
[1] /= 2;
1813 reclaim_stat
->recent_rotated
[1] /= 2;
1817 * The amount of pressure on anon vs file pages is inversely
1818 * proportional to the fraction of recently scanned pages on
1819 * each list that were recently referenced and in active use.
1821 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
1822 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
1824 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
1825 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
1826 spin_unlock_irq(&zone
->lru_lock
);
1830 denominator
= ap
+ fp
+ 1;
1832 for_each_evictable_lru(lru
) {
1833 int file
= is_file_lru(lru
);
1837 size
= get_lru_size(lruvec
, lru
);
1838 scan
= size
>> sc
->priority
;
1840 if (!scan
&& force_scan
)
1841 scan
= min(size
, SWAP_CLUSTER_MAX
);
1843 switch (scan_balance
) {
1845 /* Scan lists relative to size */
1849 * Scan types proportional to swappiness and
1850 * their relative recent reclaim efficiency.
1852 scan
= div64_u64(scan
* fraction
[file
], denominator
);
1856 /* Scan one type exclusively */
1857 if ((scan_balance
== SCAN_FILE
) != file
)
1861 /* Look ma, no brain */
1869 * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
1871 static void shrink_lruvec(struct lruvec
*lruvec
, struct scan_control
*sc
)
1873 unsigned long nr
[NR_LRU_LISTS
];
1874 unsigned long targets
[NR_LRU_LISTS
];
1875 unsigned long nr_to_scan
;
1877 unsigned long nr_reclaimed
= 0;
1878 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
1879 struct blk_plug plug
;
1880 bool scan_adjusted
= false;
1882 get_scan_count(lruvec
, sc
, nr
);
1884 /* Record the original scan target for proportional adjustments later */
1885 memcpy(targets
, nr
, sizeof(nr
));
1887 blk_start_plug(&plug
);
1888 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
1889 nr
[LRU_INACTIVE_FILE
]) {
1890 unsigned long nr_anon
, nr_file
, percentage
;
1891 unsigned long nr_scanned
;
1893 for_each_evictable_lru(lru
) {
1895 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
1896 nr
[lru
] -= nr_to_scan
;
1898 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
1903 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
1907 * For global direct reclaim, reclaim only the number of pages
1908 * requested. Less care is taken to scan proportionally as it
1909 * is more important to minimise direct reclaim stall latency
1910 * than it is to properly age the LRU lists.
1912 if (global_reclaim(sc
) && !current_is_kswapd())
1916 * For kswapd and memcg, reclaim at least the number of pages
1917 * requested. Ensure that the anon and file LRUs shrink
1918 * proportionally what was requested by get_scan_count(). We
1919 * stop reclaiming one LRU and reduce the amount scanning
1920 * proportional to the original scan target.
1922 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
1923 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
1925 if (nr_file
> nr_anon
) {
1926 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
1927 targets
[LRU_ACTIVE_ANON
] + 1;
1929 percentage
= nr_anon
* 100 / scan_target
;
1931 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
1932 targets
[LRU_ACTIVE_FILE
] + 1;
1934 percentage
= nr_file
* 100 / scan_target
;
1937 /* Stop scanning the smaller of the LRU */
1939 nr
[lru
+ LRU_ACTIVE
] = 0;
1942 * Recalculate the other LRU scan count based on its original
1943 * scan target and the percentage scanning already complete
1945 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
1946 nr_scanned
= targets
[lru
] - nr
[lru
];
1947 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
1948 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
1951 nr_scanned
= targets
[lru
] - nr
[lru
];
1952 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
1953 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
1955 scan_adjusted
= true;
1957 blk_finish_plug(&plug
);
1958 sc
->nr_reclaimed
+= nr_reclaimed
;
1961 * Even if we did not try to evict anon pages at all, we want to
1962 * rebalance the anon lru active/inactive ratio.
1964 if (inactive_anon_is_low(lruvec
))
1965 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
1966 sc
, LRU_ACTIVE_ANON
);
1968 throttle_vm_writeout(sc
->gfp_mask
);
1971 /* Use reclaim/compaction for costly allocs or under memory pressure */
1972 static bool in_reclaim_compaction(struct scan_control
*sc
)
1974 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
1975 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
1976 sc
->priority
< DEF_PRIORITY
- 2))
1983 * Reclaim/compaction is used for high-order allocation requests. It reclaims
1984 * order-0 pages before compacting the zone. should_continue_reclaim() returns
1985 * true if more pages should be reclaimed such that when the page allocator
1986 * calls try_to_compact_zone() that it will have enough free pages to succeed.
1987 * It will give up earlier than that if there is difficulty reclaiming pages.
1989 static inline bool should_continue_reclaim(struct zone
*zone
,
1990 unsigned long nr_reclaimed
,
1991 unsigned long nr_scanned
,
1992 struct scan_control
*sc
)
1994 unsigned long pages_for_compaction
;
1995 unsigned long inactive_lru_pages
;
1997 /* If not in reclaim/compaction mode, stop */
1998 if (!in_reclaim_compaction(sc
))
2001 /* Consider stopping depending on scan and reclaim activity */
2002 if (sc
->gfp_mask
& __GFP_REPEAT
) {
2004 * For __GFP_REPEAT allocations, stop reclaiming if the
2005 * full LRU list has been scanned and we are still failing
2006 * to reclaim pages. This full LRU scan is potentially
2007 * expensive but a __GFP_REPEAT caller really wants to succeed
2009 if (!nr_reclaimed
&& !nr_scanned
)
2013 * For non-__GFP_REPEAT allocations which can presumably
2014 * fail without consequence, stop if we failed to reclaim
2015 * any pages from the last SWAP_CLUSTER_MAX number of
2016 * pages that were scanned. This will return to the
2017 * caller faster at the risk reclaim/compaction and
2018 * the resulting allocation attempt fails
2025 * If we have not reclaimed enough pages for compaction and the
2026 * inactive lists are large enough, continue reclaiming
2028 pages_for_compaction
= (2UL << sc
->order
);
2029 inactive_lru_pages
= zone_page_state(zone
, NR_INACTIVE_FILE
);
2030 if (get_nr_swap_pages() > 0)
2031 inactive_lru_pages
+= zone_page_state(zone
, NR_INACTIVE_ANON
);
2032 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2033 inactive_lru_pages
> pages_for_compaction
)
2036 /* If compaction would go ahead or the allocation would succeed, stop */
2037 switch (compaction_suitable(zone
, sc
->order
)) {
2038 case COMPACT_PARTIAL
:
2039 case COMPACT_CONTINUE
:
2046 static void shrink_zone(struct zone
*zone
, struct scan_control
*sc
)
2048 unsigned long nr_reclaimed
, nr_scanned
;
2051 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2052 struct mem_cgroup_reclaim_cookie reclaim
= {
2054 .priority
= sc
->priority
,
2056 struct mem_cgroup
*memcg
;
2058 nr_reclaimed
= sc
->nr_reclaimed
;
2059 nr_scanned
= sc
->nr_scanned
;
2061 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2063 struct lruvec
*lruvec
;
2065 lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2067 shrink_lruvec(lruvec
, sc
);
2070 * Direct reclaim and kswapd have to scan all memory
2071 * cgroups to fulfill the overall scan target for the
2074 * Limit reclaim, on the other hand, only cares about
2075 * nr_to_reclaim pages to be reclaimed and it will
2076 * retry with decreasing priority if one round over the
2077 * whole hierarchy is not sufficient.
2079 if (!global_reclaim(sc
) &&
2080 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2081 mem_cgroup_iter_break(root
, memcg
);
2084 memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
);
2087 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2088 sc
->nr_scanned
- nr_scanned
,
2089 sc
->nr_reclaimed
- nr_reclaimed
);
2091 } while (should_continue_reclaim(zone
, sc
->nr_reclaimed
- nr_reclaimed
,
2092 sc
->nr_scanned
- nr_scanned
, sc
));
2095 /* Returns true if compaction should go ahead for a high-order request */
2096 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
2098 unsigned long balance_gap
, watermark
;
2101 /* Do not consider compaction for orders reclaim is meant to satisfy */
2102 if (sc
->order
<= PAGE_ALLOC_COSTLY_ORDER
)
2106 * Compaction takes time to run and there are potentially other
2107 * callers using the pages just freed. Continue reclaiming until
2108 * there is a buffer of free pages available to give compaction
2109 * a reasonable chance of completing and allocating the page
2111 balance_gap
= min(low_wmark_pages(zone
),
2112 (zone
->managed_pages
+ KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2113 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2114 watermark
= high_wmark_pages(zone
) + balance_gap
+ (2UL << sc
->order
);
2115 watermark_ok
= zone_watermark_ok_safe(zone
, 0, watermark
, 0, 0);
2118 * If compaction is deferred, reclaim up to a point where
2119 * compaction will have a chance of success when re-enabled
2121 if (compaction_deferred(zone
, sc
->order
))
2122 return watermark_ok
;
2124 /* If compaction is not ready to start, keep reclaiming */
2125 if (!compaction_suitable(zone
, sc
->order
))
2128 return watermark_ok
;
2132 * This is the direct reclaim path, for page-allocating processes. We only
2133 * try to reclaim pages from zones which will satisfy the caller's allocation
2136 * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
2138 * a) The caller may be trying to free *extra* pages to satisfy a higher-order
2140 * b) The target zone may be at high_wmark_pages(zone) but the lower zones
2141 * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
2142 * zone defense algorithm.
2144 * If a zone is deemed to be full of pinned pages then just give it a light
2145 * scan then give up on it.
2147 * This function returns true if a zone is being reclaimed for a costly
2148 * high-order allocation and compaction is ready to begin. This indicates to
2149 * the caller that it should consider retrying the allocation instead of
2152 static bool shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2156 unsigned long nr_soft_reclaimed
;
2157 unsigned long nr_soft_scanned
;
2158 bool aborted_reclaim
= false;
2161 * If the number of buffer_heads in the machine exceeds the maximum
2162 * allowed level, force direct reclaim to scan the highmem zone as
2163 * highmem pages could be pinning lowmem pages storing buffer_heads
2165 if (buffer_heads_over_limit
)
2166 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2168 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2169 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2170 if (!populated_zone(zone
))
2173 * Take care memory controller reclaiming has small influence
2176 if (global_reclaim(sc
)) {
2177 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2179 if (zone
->all_unreclaimable
&&
2180 sc
->priority
!= DEF_PRIORITY
)
2181 continue; /* Let kswapd poll it */
2182 if (IS_ENABLED(CONFIG_COMPACTION
)) {
2184 * If we already have plenty of memory free for
2185 * compaction in this zone, don't free any more.
2186 * Even though compaction is invoked for any
2187 * non-zero order, only frequent costly order
2188 * reclamation is disruptive enough to become a
2189 * noticeable problem, like transparent huge
2192 if (compaction_ready(zone
, sc
)) {
2193 aborted_reclaim
= true;
2198 * This steals pages from memory cgroups over softlimit
2199 * and returns the number of reclaimed pages and
2200 * scanned pages. This works for global memory pressure
2201 * and balancing, not for a memcg's limit.
2203 nr_soft_scanned
= 0;
2204 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2205 sc
->order
, sc
->gfp_mask
,
2207 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2208 sc
->nr_scanned
+= nr_soft_scanned
;
2209 /* need some check for avoid more shrink_zone() */
2212 shrink_zone(zone
, sc
);
2215 return aborted_reclaim
;
2218 static bool zone_reclaimable(struct zone
*zone
)
2220 return zone
->pages_scanned
< zone_reclaimable_pages(zone
) * 6;
2223 /* All zones in zonelist are unreclaimable? */
2224 static bool all_unreclaimable(struct zonelist
*zonelist
,
2225 struct scan_control
*sc
)
2230 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2231 gfp_zone(sc
->gfp_mask
), sc
->nodemask
) {
2232 if (!populated_zone(zone
))
2234 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2236 if (!zone
->all_unreclaimable
)
2244 * This is the main entry point to direct page reclaim.
2246 * If a full scan of the inactive list fails to free enough memory then we
2247 * are "out of memory" and something needs to be killed.
2249 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2250 * high - the zone may be full of dirty or under-writeback pages, which this
2251 * caller can't do much about. We kick the writeback threads and take explicit
2252 * naps in the hope that some of these pages can be written. But if the
2253 * allocating task holds filesystem locks which prevent writeout this might not
2254 * work, and the allocation attempt will fail.
2256 * returns: 0, if no pages reclaimed
2257 * else, the number of pages reclaimed
2259 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2260 struct scan_control
*sc
,
2261 struct shrink_control
*shrink
)
2263 unsigned long total_scanned
= 0;
2264 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2267 unsigned long writeback_threshold
;
2268 bool aborted_reclaim
;
2270 delayacct_freepages_start();
2272 if (global_reclaim(sc
))
2273 count_vm_event(ALLOCSTALL
);
2276 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
2279 aborted_reclaim
= shrink_zones(zonelist
, sc
);
2282 * Don't shrink slabs when reclaiming memory from
2283 * over limit cgroups
2285 if (global_reclaim(sc
)) {
2286 unsigned long lru_pages
= 0;
2287 for_each_zone_zonelist(zone
, z
, zonelist
,
2288 gfp_zone(sc
->gfp_mask
)) {
2289 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
2292 lru_pages
+= zone_reclaimable_pages(zone
);
2295 shrink_slab(shrink
, sc
->nr_scanned
, lru_pages
);
2296 if (reclaim_state
) {
2297 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2298 reclaim_state
->reclaimed_slab
= 0;
2301 total_scanned
+= sc
->nr_scanned
;
2302 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
2306 * If we're getting trouble reclaiming, start doing
2307 * writepage even in laptop mode.
2309 if (sc
->priority
< DEF_PRIORITY
- 2)
2310 sc
->may_writepage
= 1;
2313 * Try to write back as many pages as we just scanned. This
2314 * tends to cause slow streaming writers to write data to the
2315 * disk smoothly, at the dirtying rate, which is nice. But
2316 * that's undesirable in laptop mode, where we *want* lumpy
2317 * writeout. So in laptop mode, write out the whole world.
2319 writeback_threshold
= sc
->nr_to_reclaim
+ sc
->nr_to_reclaim
/ 2;
2320 if (total_scanned
> writeback_threshold
) {
2321 wakeup_flusher_threads(laptop_mode
? 0 : total_scanned
,
2322 WB_REASON_TRY_TO_FREE_PAGES
);
2323 sc
->may_writepage
= 1;
2326 /* Take a nap, wait for some writeback to complete */
2327 if (!sc
->hibernation_mode
&& sc
->nr_scanned
&&
2328 sc
->priority
< DEF_PRIORITY
- 2) {
2329 struct zone
*preferred_zone
;
2331 first_zones_zonelist(zonelist
, gfp_zone(sc
->gfp_mask
),
2332 &cpuset_current_mems_allowed
,
2334 wait_iff_congested(preferred_zone
, BLK_RW_ASYNC
, HZ
/10);
2336 } while (--sc
->priority
>= 0);
2339 delayacct_freepages_end();
2341 if (sc
->nr_reclaimed
)
2342 return sc
->nr_reclaimed
;
2345 * As hibernation is going on, kswapd is freezed so that it can't mark
2346 * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
2349 if (oom_killer_disabled
)
2352 /* Aborted reclaim to try compaction? don't OOM, then */
2353 if (aborted_reclaim
)
2356 /* top priority shrink_zones still had more to do? don't OOM, then */
2357 if (global_reclaim(sc
) && !all_unreclaimable(zonelist
, sc
))
2363 static bool pfmemalloc_watermark_ok(pg_data_t
*pgdat
)
2366 unsigned long pfmemalloc_reserve
= 0;
2367 unsigned long free_pages
= 0;
2371 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
2372 zone
= &pgdat
->node_zones
[i
];
2373 pfmemalloc_reserve
+= min_wmark_pages(zone
);
2374 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
2377 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
2379 /* kswapd must be awake if processes are being throttled */
2380 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
2381 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
,
2382 (enum zone_type
)ZONE_NORMAL
);
2383 wake_up_interruptible(&pgdat
->kswapd_wait
);
2390 * Throttle direct reclaimers if backing storage is backed by the network
2391 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
2392 * depleted. kswapd will continue to make progress and wake the processes
2393 * when the low watermark is reached.
2395 * Returns true if a fatal signal was delivered during throttling. If this
2396 * happens, the page allocator should not consider triggering the OOM killer.
2398 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
2399 nodemask_t
*nodemask
)
2402 int high_zoneidx
= gfp_zone(gfp_mask
);
2406 * Kernel threads should not be throttled as they may be indirectly
2407 * responsible for cleaning pages necessary for reclaim to make forward
2408 * progress. kjournald for example may enter direct reclaim while
2409 * committing a transaction where throttling it could forcing other
2410 * processes to block on log_wait_commit().
2412 if (current
->flags
& PF_KTHREAD
)
2416 * If a fatal signal is pending, this process should not throttle.
2417 * It should return quickly so it can exit and free its memory
2419 if (fatal_signal_pending(current
))
2422 /* Check if the pfmemalloc reserves are ok */
2423 first_zones_zonelist(zonelist
, high_zoneidx
, NULL
, &zone
);
2424 pgdat
= zone
->zone_pgdat
;
2425 if (pfmemalloc_watermark_ok(pgdat
))
2428 /* Account for the throttling */
2429 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
2432 * If the caller cannot enter the filesystem, it's possible that it
2433 * is due to the caller holding an FS lock or performing a journal
2434 * transaction in the case of a filesystem like ext[3|4]. In this case,
2435 * it is not safe to block on pfmemalloc_wait as kswapd could be
2436 * blocked waiting on the same lock. Instead, throttle for up to a
2437 * second before continuing.
2439 if (!(gfp_mask
& __GFP_FS
)) {
2440 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
2441 pfmemalloc_watermark_ok(pgdat
), HZ
);
2446 /* Throttle until kswapd wakes the process */
2447 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
2448 pfmemalloc_watermark_ok(pgdat
));
2451 if (fatal_signal_pending(current
))
2458 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
2459 gfp_t gfp_mask
, nodemask_t
*nodemask
)
2461 unsigned long nr_reclaimed
;
2462 struct scan_control sc
= {
2463 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
2464 .may_writepage
= !laptop_mode
,
2465 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2469 .priority
= DEF_PRIORITY
,
2470 .target_mem_cgroup
= NULL
,
2471 .nodemask
= nodemask
,
2473 struct shrink_control shrink
= {
2474 .gfp_mask
= sc
.gfp_mask
,
2478 * Do not enter reclaim if fatal signal was delivered while throttled.
2479 * 1 is returned so that the page allocator does not OOM kill at this
2482 if (throttle_direct_reclaim(gfp_mask
, zonelist
, nodemask
))
2485 trace_mm_vmscan_direct_reclaim_begin(order
,
2489 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2491 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
2493 return nr_reclaimed
;
2498 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup
*memcg
,
2499 gfp_t gfp_mask
, bool noswap
,
2501 unsigned long *nr_scanned
)
2503 struct scan_control sc
= {
2505 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2506 .may_writepage
= !laptop_mode
,
2508 .may_swap
= !noswap
,
2511 .target_mem_cgroup
= memcg
,
2513 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2515 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2516 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
2518 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
2523 * NOTE: Although we can get the priority field, using it
2524 * here is not a good idea, since it limits the pages we can scan.
2525 * if we don't reclaim here, the shrink_zone from balance_pgdat
2526 * will pick up pages from other mem cgroup's as well. We hack
2527 * the priority and make it zero.
2529 shrink_lruvec(lruvec
, &sc
);
2531 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
2533 *nr_scanned
= sc
.nr_scanned
;
2534 return sc
.nr_reclaimed
;
2537 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
2541 struct zonelist
*zonelist
;
2542 unsigned long nr_reclaimed
;
2544 struct scan_control sc
= {
2545 .may_writepage
= !laptop_mode
,
2547 .may_swap
= !noswap
,
2548 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
2550 .priority
= DEF_PRIORITY
,
2551 .target_mem_cgroup
= memcg
,
2552 .nodemask
= NULL
, /* we don't care the placement */
2553 .gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
2554 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
2556 struct shrink_control shrink
= {
2557 .gfp_mask
= sc
.gfp_mask
,
2561 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
2562 * take care of from where we get pages. So the node where we start the
2563 * scan does not need to be the current node.
2565 nid
= mem_cgroup_select_victim_node(memcg
);
2567 zonelist
= NODE_DATA(nid
)->node_zonelists
;
2569 trace_mm_vmscan_memcg_reclaim_begin(0,
2573 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
2575 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
2577 return nr_reclaimed
;
2581 static void age_active_anon(struct zone
*zone
, struct scan_control
*sc
)
2583 struct mem_cgroup
*memcg
;
2585 if (!total_swap_pages
)
2588 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
2590 struct lruvec
*lruvec
= mem_cgroup_zone_lruvec(zone
, memcg
);
2592 if (inactive_anon_is_low(lruvec
))
2593 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2594 sc
, LRU_ACTIVE_ANON
);
2596 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
2600 static bool zone_balanced(struct zone
*zone
, int order
,
2601 unsigned long balance_gap
, int classzone_idx
)
2603 if (!zone_watermark_ok_safe(zone
, order
, high_wmark_pages(zone
) +
2604 balance_gap
, classzone_idx
, 0))
2607 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&&
2608 !compaction_suitable(zone
, order
))
2615 * pgdat_balanced() is used when checking if a node is balanced.
2617 * For order-0, all zones must be balanced!
2619 * For high-order allocations only zones that meet watermarks and are in a
2620 * zone allowed by the callers classzone_idx are added to balanced_pages. The
2621 * total of balanced pages must be at least 25% of the zones allowed by
2622 * classzone_idx for the node to be considered balanced. Forcing all zones to
2623 * be balanced for high orders can cause excessive reclaim when there are
2625 * The choice of 25% is due to
2626 * o a 16M DMA zone that is balanced will not balance a zone on any
2627 * reasonable sized machine
2628 * o On all other machines, the top zone must be at least a reasonable
2629 * percentage of the middle zones. For example, on 32-bit x86, highmem
2630 * would need to be at least 256M for it to be balance a whole node.
2631 * Similarly, on x86-64 the Normal zone would need to be at least 1G
2632 * to balance a node on its own. These seemed like reasonable ratios.
2634 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
2636 unsigned long managed_pages
= 0;
2637 unsigned long balanced_pages
= 0;
2640 /* Check the watermark levels */
2641 for (i
= 0; i
<= classzone_idx
; i
++) {
2642 struct zone
*zone
= pgdat
->node_zones
+ i
;
2644 if (!populated_zone(zone
))
2647 managed_pages
+= zone
->managed_pages
;
2650 * A special case here:
2652 * balance_pgdat() skips over all_unreclaimable after
2653 * DEF_PRIORITY. Effectively, it considers them balanced so
2654 * they must be considered balanced here as well!
2656 if (zone
->all_unreclaimable
) {
2657 balanced_pages
+= zone
->managed_pages
;
2661 if (zone_balanced(zone
, order
, 0, i
))
2662 balanced_pages
+= zone
->managed_pages
;
2668 return balanced_pages
>= (managed_pages
>> 2);
2674 * Prepare kswapd for sleeping. This verifies that there are no processes
2675 * waiting in throttle_direct_reclaim() and that watermarks have been met.
2677 * Returns true if kswapd is ready to sleep
2679 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, long remaining
,
2682 /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
2687 * There is a potential race between when kswapd checks its watermarks
2688 * and a process gets throttled. There is also a potential race if
2689 * processes get throttled, kswapd wakes, a large process exits therby
2690 * balancing the zones that causes kswapd to miss a wakeup. If kswapd
2691 * is going to sleep, no process should be sleeping on pfmemalloc_wait
2692 * so wake them now if necessary. If necessary, processes will wake
2693 * kswapd and get throttled again
2695 if (waitqueue_active(&pgdat
->pfmemalloc_wait
)) {
2696 wake_up(&pgdat
->pfmemalloc_wait
);
2700 return pgdat_balanced(pgdat
, order
, classzone_idx
);
2704 * kswapd shrinks the zone by the number of pages required to reach
2705 * the high watermark.
2707 * Returns true if kswapd scanned at least the requested number of pages to
2708 * reclaim or if the lack of progress was due to pages under writeback.
2709 * This is used to determine if the scanning priority needs to be raised.
2711 static bool kswapd_shrink_zone(struct zone
*zone
,
2712 struct scan_control
*sc
,
2713 unsigned long lru_pages
,
2714 unsigned long *nr_attempted
)
2716 unsigned long nr_slab
;
2717 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2718 struct shrink_control shrink
= {
2719 .gfp_mask
= sc
->gfp_mask
,
2722 /* Reclaim above the high watermark. */
2723 sc
->nr_to_reclaim
= max(SWAP_CLUSTER_MAX
, high_wmark_pages(zone
));
2724 shrink_zone(zone
, sc
);
2726 reclaim_state
->reclaimed_slab
= 0;
2727 nr_slab
= shrink_slab(&shrink
, sc
->nr_scanned
, lru_pages
);
2728 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2730 /* Account for the number of pages attempted to reclaim */
2731 *nr_attempted
+= sc
->nr_to_reclaim
;
2733 if (nr_slab
== 0 && !zone_reclaimable(zone
))
2734 zone
->all_unreclaimable
= 1;
2736 zone_clear_flag(zone
, ZONE_WRITEBACK
);
2738 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
2742 * For kswapd, balance_pgdat() will work across all this node's zones until
2743 * they are all at high_wmark_pages(zone).
2745 * Returns the final order kswapd was reclaiming at
2747 * There is special handling here for zones which are full of pinned pages.
2748 * This can happen if the pages are all mlocked, or if they are all used by
2749 * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
2750 * What we do is to detect the case where all pages in the zone have been
2751 * scanned twice and there has been zero successful reclaim. Mark the zone as
2752 * dead and from now on, only perform a short scan. Basically we're polling
2753 * the zone for when the problem goes away.
2755 * kswapd scans the zones in the highmem->normal->dma direction. It skips
2756 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
2757 * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
2758 * lower zones regardless of the number of free pages in the lower zones. This
2759 * interoperates with the page allocator fallback scheme to ensure that aging
2760 * of pages is balanced across the zones.
2762 static unsigned long balance_pgdat(pg_data_t
*pgdat
, int order
,
2766 int end_zone
= 0; /* Inclusive. 0 = ZONE_DMA */
2767 unsigned long nr_soft_reclaimed
;
2768 unsigned long nr_soft_scanned
;
2769 struct scan_control sc
= {
2770 .gfp_mask
= GFP_KERNEL
,
2771 .priority
= DEF_PRIORITY
,
2774 .may_writepage
= !laptop_mode
,
2776 .target_mem_cgroup
= NULL
,
2778 count_vm_event(PAGEOUTRUN
);
2781 unsigned long lru_pages
= 0;
2782 unsigned long nr_attempted
= 0;
2783 bool raise_priority
= true;
2784 bool pgdat_needs_compaction
= (order
> 0);
2786 sc
.nr_reclaimed
= 0;
2789 * Scan in the highmem->dma direction for the highest
2790 * zone which needs scanning
2792 for (i
= pgdat
->nr_zones
- 1; i
>= 0; i
--) {
2793 struct zone
*zone
= pgdat
->node_zones
+ i
;
2795 if (!populated_zone(zone
))
2798 if (zone
->all_unreclaimable
&&
2799 sc
.priority
!= DEF_PRIORITY
)
2803 * Do some background aging of the anon list, to give
2804 * pages a chance to be referenced before reclaiming.
2806 age_active_anon(zone
, &sc
);
2809 * If the number of buffer_heads in the machine
2810 * exceeds the maximum allowed level and this node
2811 * has a highmem zone, force kswapd to reclaim from
2812 * it to relieve lowmem pressure.
2814 if (buffer_heads_over_limit
&& is_highmem_idx(i
)) {
2819 if (!zone_balanced(zone
, order
, 0, 0)) {
2824 * If balanced, clear the dirty and congested
2827 zone_clear_flag(zone
, ZONE_CONGESTED
);
2828 zone_clear_flag(zone
, ZONE_TAIL_LRU_DIRTY
);
2835 for (i
= 0; i
<= end_zone
; i
++) {
2836 struct zone
*zone
= pgdat
->node_zones
+ i
;
2838 if (!populated_zone(zone
))
2841 lru_pages
+= zone_reclaimable_pages(zone
);
2844 * If any zone is currently balanced then kswapd will
2845 * not call compaction as it is expected that the
2846 * necessary pages are already available.
2848 if (pgdat_needs_compaction
&&
2849 zone_watermark_ok(zone
, order
,
2850 low_wmark_pages(zone
),
2852 pgdat_needs_compaction
= false;
2856 * If we're getting trouble reclaiming, start doing writepage
2857 * even in laptop mode.
2859 if (sc
.priority
< DEF_PRIORITY
- 2)
2860 sc
.may_writepage
= 1;
2863 * Now scan the zone in the dma->highmem direction, stopping
2864 * at the last zone which needs scanning.
2866 * We do this because the page allocator works in the opposite
2867 * direction. This prevents the page allocator from allocating
2868 * pages behind kswapd's direction of progress, which would
2869 * cause too much scanning of the lower zones.
2871 for (i
= 0; i
<= end_zone
; i
++) {
2872 struct zone
*zone
= pgdat
->node_zones
+ i
;
2874 unsigned long balance_gap
;
2876 if (!populated_zone(zone
))
2879 if (zone
->all_unreclaimable
&&
2880 sc
.priority
!= DEF_PRIORITY
)
2885 nr_soft_scanned
= 0;
2887 * Call soft limit reclaim before calling shrink_zone.
2889 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
,
2892 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
2895 * We put equal pressure on every zone, unless
2896 * one zone has way too many pages free
2897 * already. The "too many pages" is defined
2898 * as the high wmark plus a "gap" where the
2899 * gap is either the low watermark or 1%
2900 * of the zone, whichever is smaller.
2902 balance_gap
= min(low_wmark_pages(zone
),
2903 (zone
->managed_pages
+
2904 KSWAPD_ZONE_BALANCE_GAP_RATIO
-1) /
2905 KSWAPD_ZONE_BALANCE_GAP_RATIO
);
2907 * Kswapd reclaims only single pages with compaction
2908 * enabled. Trying too hard to reclaim until contiguous
2909 * free pages have become available can hurt performance
2910 * by evicting too much useful data from memory.
2911 * Do not reclaim more than needed for compaction.
2914 if (IS_ENABLED(CONFIG_COMPACTION
) && order
&&
2915 compaction_suitable(zone
, order
) !=
2919 if ((buffer_heads_over_limit
&& is_highmem_idx(i
)) ||
2920 !zone_balanced(zone
, testorder
,
2921 balance_gap
, end_zone
)) {
2923 * There should be no need to raise the
2924 * scanning priority if enough pages are
2925 * already being scanned that high
2926 * watermark would be met at 100% efficiency.
2928 if (kswapd_shrink_zone(zone
, &sc
, lru_pages
,
2930 raise_priority
= false;
2933 if (zone
->all_unreclaimable
) {
2934 if (end_zone
&& end_zone
== i
)
2939 if (zone_balanced(zone
, testorder
, 0, end_zone
))
2941 * If a zone reaches its high watermark,
2942 * consider it to be no longer congested. It's
2943 * possible there are dirty pages backed by
2944 * congested BDIs but as pressure is relieved,
2945 * speculatively avoid congestion waits
2946 * or writing pages from kswapd context.
2948 zone_clear_flag(zone
, ZONE_CONGESTED
);
2949 zone_clear_flag(zone
, ZONE_TAIL_LRU_DIRTY
);
2953 * If the low watermark is met there is no need for processes
2954 * to be throttled on pfmemalloc_wait as they should not be
2955 * able to safely make forward progress. Wake them
2957 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
2958 pfmemalloc_watermark_ok(pgdat
))
2959 wake_up(&pgdat
->pfmemalloc_wait
);
2962 * Fragmentation may mean that the system cannot be rebalanced
2963 * for high-order allocations in all zones. If twice the
2964 * allocation size has been reclaimed and the zones are still
2965 * not balanced then recheck the watermarks at order-0 to
2966 * prevent kswapd reclaiming excessively. Assume that a
2967 * process requested a high-order can direct reclaim/compact.
2969 if (order
&& sc
.nr_reclaimed
>= 2UL << order
)
2970 order
= sc
.order
= 0;
2972 /* Check if kswapd should be suspending */
2973 if (try_to_freeze() || kthread_should_stop())
2977 * Compact if necessary and kswapd is reclaiming at least the
2978 * high watermark number of pages as requsted
2980 if (pgdat_needs_compaction
&& sc
.nr_reclaimed
> nr_attempted
)
2981 compact_pgdat(pgdat
, order
);
2984 * Raise priority if scanning rate is too low or there was no
2985 * progress in reclaiming pages
2987 if (raise_priority
|| !sc
.nr_reclaimed
)
2989 } while (sc
.priority
>= 1 &&
2990 !pgdat_balanced(pgdat
, order
, *classzone_idx
));
2994 * Return the order we were reclaiming at so prepare_kswapd_sleep()
2995 * makes a decision on the order we were last reclaiming at. However,
2996 * if another caller entered the allocator slow path while kswapd
2997 * was awake, order will remain at the higher level
2999 *classzone_idx
= end_zone
;
3003 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3008 if (freezing(current
) || kthread_should_stop())
3011 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3013 /* Try to sleep for a short interval */
3014 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3015 remaining
= schedule_timeout(HZ
/10);
3016 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3017 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3021 * After a short sleep, check if it was a premature sleep. If not, then
3022 * go fully to sleep until explicitly woken up.
3024 if (prepare_kswapd_sleep(pgdat
, order
, remaining
, classzone_idx
)) {
3025 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3028 * vmstat counters are not perfectly accurate and the estimated
3029 * value for counters such as NR_FREE_PAGES can deviate from the
3030 * true value by nr_online_cpus * threshold. To avoid the zone
3031 * watermarks being breached while under pressure, we reduce the
3032 * per-cpu vmstat threshold while kswapd is awake and restore
3033 * them before going back to sleep.
3035 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3038 * Compaction records what page blocks it recently failed to
3039 * isolate pages from and skips them in the future scanning.
3040 * When kswapd is going to sleep, it is reasonable to assume
3041 * that pages and compaction may succeed so reset the cache.
3043 reset_isolation_suitable(pgdat
);
3045 if (!kthread_should_stop())
3048 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3051 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3053 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3055 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3059 * The background pageout daemon, started as a kernel thread
3060 * from the init process.
3062 * This basically trickles out pages so that we have _some_
3063 * free memory available even if there is no other activity
3064 * that frees anything up. This is needed for things like routing
3065 * etc, where we otherwise might have all activity going on in
3066 * asynchronous contexts that cannot page things out.
3068 * If there are applications that are active memory-allocators
3069 * (most normal use), this basically shouldn't matter.
3071 static int kswapd(void *p
)
3073 unsigned long order
, new_order
;
3074 unsigned balanced_order
;
3075 int classzone_idx
, new_classzone_idx
;
3076 int balanced_classzone_idx
;
3077 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3078 struct task_struct
*tsk
= current
;
3080 struct reclaim_state reclaim_state
= {
3081 .reclaimed_slab
= 0,
3083 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3085 lockdep_set_current_reclaim_state(GFP_KERNEL
);
3087 if (!cpumask_empty(cpumask
))
3088 set_cpus_allowed_ptr(tsk
, cpumask
);
3089 current
->reclaim_state
= &reclaim_state
;
3092 * Tell the memory management that we're a "memory allocator",
3093 * and that if we need more memory we should get access to it
3094 * regardless (see "__alloc_pages()"). "kswapd" should
3095 * never get caught in the normal page freeing logic.
3097 * (Kswapd normally doesn't need memory anyway, but sometimes
3098 * you need a small amount of memory in order to be able to
3099 * page out something else, and this flag essentially protects
3100 * us from recursively trying to free more memory as we're
3101 * trying to free the first piece of memory in the first place).
3103 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3106 order
= new_order
= 0;
3108 classzone_idx
= new_classzone_idx
= pgdat
->nr_zones
- 1;
3109 balanced_classzone_idx
= classzone_idx
;
3114 * If the last balance_pgdat was unsuccessful it's unlikely a
3115 * new request of a similar or harder type will succeed soon
3116 * so consider going to sleep on the basis we reclaimed at
3118 if (balanced_classzone_idx
>= new_classzone_idx
&&
3119 balanced_order
== new_order
) {
3120 new_order
= pgdat
->kswapd_max_order
;
3121 new_classzone_idx
= pgdat
->classzone_idx
;
3122 pgdat
->kswapd_max_order
= 0;
3123 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3126 if (order
< new_order
|| classzone_idx
> new_classzone_idx
) {
3128 * Don't sleep if someone wants a larger 'order'
3129 * allocation or has tigher zone constraints
3132 classzone_idx
= new_classzone_idx
;
3134 kswapd_try_to_sleep(pgdat
, balanced_order
,
3135 balanced_classzone_idx
);
3136 order
= pgdat
->kswapd_max_order
;
3137 classzone_idx
= pgdat
->classzone_idx
;
3139 new_classzone_idx
= classzone_idx
;
3140 pgdat
->kswapd_max_order
= 0;
3141 pgdat
->classzone_idx
= pgdat
->nr_zones
- 1;
3144 ret
= try_to_freeze();
3145 if (kthread_should_stop())
3149 * We can speed up thawing tasks if we don't call balance_pgdat
3150 * after returning from the refrigerator
3153 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, order
);
3154 balanced_classzone_idx
= classzone_idx
;
3155 balanced_order
= balance_pgdat(pgdat
, order
,
3156 &balanced_classzone_idx
);
3160 current
->reclaim_state
= NULL
;
3165 * A zone is low on free memory, so wake its kswapd task to service it.
3167 void wakeup_kswapd(struct zone
*zone
, int order
, enum zone_type classzone_idx
)
3171 if (!populated_zone(zone
))
3174 if (!cpuset_zone_allowed_hardwall(zone
, GFP_KERNEL
))
3176 pgdat
= zone
->zone_pgdat
;
3177 if (pgdat
->kswapd_max_order
< order
) {
3178 pgdat
->kswapd_max_order
= order
;
3179 pgdat
->classzone_idx
= min(pgdat
->classzone_idx
, classzone_idx
);
3181 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3183 if (zone_watermark_ok_safe(zone
, order
, low_wmark_pages(zone
), 0, 0))
3186 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, zone_idx(zone
), order
);
3187 wake_up_interruptible(&pgdat
->kswapd_wait
);
3191 * The reclaimable count would be mostly accurate.
3192 * The less reclaimable pages may be
3193 * - mlocked pages, which will be moved to unevictable list when encountered
3194 * - mapped pages, which may require several travels to be reclaimed
3195 * - dirty pages, which is not "instantly" reclaimable
3197 unsigned long global_reclaimable_pages(void)
3201 nr
= global_page_state(NR_ACTIVE_FILE
) +
3202 global_page_state(NR_INACTIVE_FILE
);
3204 if (get_nr_swap_pages() > 0)
3205 nr
+= global_page_state(NR_ACTIVE_ANON
) +
3206 global_page_state(NR_INACTIVE_ANON
);
3211 unsigned long zone_reclaimable_pages(struct zone
*zone
)
3215 nr
= zone_page_state(zone
, NR_ACTIVE_FILE
) +
3216 zone_page_state(zone
, NR_INACTIVE_FILE
);
3218 if (get_nr_swap_pages() > 0)
3219 nr
+= zone_page_state(zone
, NR_ACTIVE_ANON
) +
3220 zone_page_state(zone
, NR_INACTIVE_ANON
);
3225 #ifdef CONFIG_HIBERNATION
3227 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3230 * Rather than trying to age LRUs the aim is to preserve the overall
3231 * LRU order by reclaiming preferentially
3232 * inactive > active > active referenced > active mapped
3234 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3236 struct reclaim_state reclaim_state
;
3237 struct scan_control sc
= {
3238 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3242 .nr_to_reclaim
= nr_to_reclaim
,
3243 .hibernation_mode
= 1,
3245 .priority
= DEF_PRIORITY
,
3247 struct shrink_control shrink
= {
3248 .gfp_mask
= sc
.gfp_mask
,
3250 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3251 struct task_struct
*p
= current
;
3252 unsigned long nr_reclaimed
;
3254 p
->flags
|= PF_MEMALLOC
;
3255 lockdep_set_current_reclaim_state(sc
.gfp_mask
);
3256 reclaim_state
.reclaimed_slab
= 0;
3257 p
->reclaim_state
= &reclaim_state
;
3259 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
, &shrink
);
3261 p
->reclaim_state
= NULL
;
3262 lockdep_clear_current_reclaim_state();
3263 p
->flags
&= ~PF_MEMALLOC
;
3265 return nr_reclaimed
;
3267 #endif /* CONFIG_HIBERNATION */
3269 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3270 not required for correctness. So if the last cpu in a node goes
3271 away, we get changed to run anywhere: as the first one comes back,
3272 restore their cpu bindings. */
3273 static int cpu_callback(struct notifier_block
*nfb
, unsigned long action
,
3278 if (action
== CPU_ONLINE
|| action
== CPU_ONLINE_FROZEN
) {
3279 for_each_node_state(nid
, N_MEMORY
) {
3280 pg_data_t
*pgdat
= NODE_DATA(nid
);
3281 const struct cpumask
*mask
;
3283 mask
= cpumask_of_node(pgdat
->node_id
);
3285 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3286 /* One of our CPUs online: restore mask */
3287 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
3294 * This kswapd start function will be called by init and node-hot-add.
3295 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
3297 int kswapd_run(int nid
)
3299 pg_data_t
*pgdat
= NODE_DATA(nid
);
3305 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
3306 if (IS_ERR(pgdat
->kswapd
)) {
3307 /* failure at boot is fatal */
3308 BUG_ON(system_state
== SYSTEM_BOOTING
);
3309 pr_err("Failed to start kswapd on node %d\n", nid
);
3310 ret
= PTR_ERR(pgdat
->kswapd
);
3311 pgdat
->kswapd
= NULL
;
3317 * Called by memory hotplug when all memory in a node is offlined. Caller must
3318 * hold lock_memory_hotplug().
3320 void kswapd_stop(int nid
)
3322 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
3325 kthread_stop(kswapd
);
3326 NODE_DATA(nid
)->kswapd
= NULL
;
3330 static int __init
kswapd_init(void)
3335 for_each_node_state(nid
, N_MEMORY
)
3337 hotcpu_notifier(cpu_callback
, 0);
3341 module_init(kswapd_init
)
3347 * If non-zero call zone_reclaim when the number of free pages falls below
3350 int zone_reclaim_mode __read_mostly
;
3352 #define RECLAIM_OFF 0
3353 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
3354 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
3355 #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
3358 * Priority for ZONE_RECLAIM. This determines the fraction of pages
3359 * of a node considered for each zone_reclaim. 4 scans 1/16th of
3362 #define ZONE_RECLAIM_PRIORITY 4
3365 * Percentage of pages in a zone that must be unmapped for zone_reclaim to
3368 int sysctl_min_unmapped_ratio
= 1;
3371 * If the number of slab pages in a zone grows beyond this percentage then
3372 * slab reclaim needs to occur.
3374 int sysctl_min_slab_ratio
= 5;
3376 static inline unsigned long zone_unmapped_file_pages(struct zone
*zone
)
3378 unsigned long file_mapped
= zone_page_state(zone
, NR_FILE_MAPPED
);
3379 unsigned long file_lru
= zone_page_state(zone
, NR_INACTIVE_FILE
) +
3380 zone_page_state(zone
, NR_ACTIVE_FILE
);
3383 * It's possible for there to be more file mapped pages than
3384 * accounted for by the pages on the file LRU lists because
3385 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
3387 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
3390 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
3391 static long zone_pagecache_reclaimable(struct zone
*zone
)
3393 long nr_pagecache_reclaimable
;
3397 * If RECLAIM_SWAP is set, then all file pages are considered
3398 * potentially reclaimable. Otherwise, we have to worry about
3399 * pages like swapcache and zone_unmapped_file_pages() provides
3402 if (zone_reclaim_mode
& RECLAIM_SWAP
)
3403 nr_pagecache_reclaimable
= zone_page_state(zone
, NR_FILE_PAGES
);
3405 nr_pagecache_reclaimable
= zone_unmapped_file_pages(zone
);
3407 /* If we can't clean pages, remove dirty pages from consideration */
3408 if (!(zone_reclaim_mode
& RECLAIM_WRITE
))
3409 delta
+= zone_page_state(zone
, NR_FILE_DIRTY
);
3411 /* Watch for any possible underflows due to delta */
3412 if (unlikely(delta
> nr_pagecache_reclaimable
))
3413 delta
= nr_pagecache_reclaimable
;
3415 return nr_pagecache_reclaimable
- delta
;
3419 * Try to free up some pages from this zone through reclaim.
3421 static int __zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3423 /* Minimum pages needed in order to stay on node */
3424 const unsigned long nr_pages
= 1 << order
;
3425 struct task_struct
*p
= current
;
3426 struct reclaim_state reclaim_state
;
3427 struct scan_control sc
= {
3428 .may_writepage
= !!(zone_reclaim_mode
& RECLAIM_WRITE
),
3429 .may_unmap
= !!(zone_reclaim_mode
& RECLAIM_SWAP
),
3431 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3432 .gfp_mask
= (gfp_mask
= memalloc_noio_flags(gfp_mask
)),
3434 .priority
= ZONE_RECLAIM_PRIORITY
,
3436 struct shrink_control shrink
= {
3437 .gfp_mask
= sc
.gfp_mask
,
3439 unsigned long nr_slab_pages0
, nr_slab_pages1
;
3443 * We need to be able to allocate from the reserves for RECLAIM_SWAP
3444 * and we also need to be able to write out pages for RECLAIM_WRITE
3447 p
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
;
3448 lockdep_set_current_reclaim_state(gfp_mask
);
3449 reclaim_state
.reclaimed_slab
= 0;
3450 p
->reclaim_state
= &reclaim_state
;
3452 if (zone_pagecache_reclaimable(zone
) > zone
->min_unmapped_pages
) {
3454 * Free memory by calling shrink zone with increasing
3455 * priorities until we have enough memory freed.
3458 shrink_zone(zone
, &sc
);
3459 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
3462 nr_slab_pages0
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3463 if (nr_slab_pages0
> zone
->min_slab_pages
) {
3465 * shrink_slab() does not currently allow us to determine how
3466 * many pages were freed in this zone. So we take the current
3467 * number of slab pages and shake the slab until it is reduced
3468 * by the same nr_pages that we used for reclaiming unmapped
3471 * Note that shrink_slab will free memory on all zones and may
3475 unsigned long lru_pages
= zone_reclaimable_pages(zone
);
3477 /* No reclaimable slab or very low memory pressure */
3478 if (!shrink_slab(&shrink
, sc
.nr_scanned
, lru_pages
))
3481 /* Freed enough memory */
3482 nr_slab_pages1
= zone_page_state(zone
,
3483 NR_SLAB_RECLAIMABLE
);
3484 if (nr_slab_pages1
+ nr_pages
<= nr_slab_pages0
)
3489 * Update nr_reclaimed by the number of slab pages we
3490 * reclaimed from this zone.
3492 nr_slab_pages1
= zone_page_state(zone
, NR_SLAB_RECLAIMABLE
);
3493 if (nr_slab_pages1
< nr_slab_pages0
)
3494 sc
.nr_reclaimed
+= nr_slab_pages0
- nr_slab_pages1
;
3497 p
->reclaim_state
= NULL
;
3498 current
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
);
3499 lockdep_clear_current_reclaim_state();
3500 return sc
.nr_reclaimed
>= nr_pages
;
3503 int zone_reclaim(struct zone
*zone
, gfp_t gfp_mask
, unsigned int order
)
3509 * Zone reclaim reclaims unmapped file backed pages and
3510 * slab pages if we are over the defined limits.
3512 * A small portion of unmapped file backed pages is needed for
3513 * file I/O otherwise pages read by file I/O will be immediately
3514 * thrown out if the zone is overallocated. So we do not reclaim
3515 * if less than a specified percentage of the zone is used by
3516 * unmapped file backed pages.
3518 if (zone_pagecache_reclaimable(zone
) <= zone
->min_unmapped_pages
&&
3519 zone_page_state(zone
, NR_SLAB_RECLAIMABLE
) <= zone
->min_slab_pages
)
3520 return ZONE_RECLAIM_FULL
;
3522 if (zone
->all_unreclaimable
)
3523 return ZONE_RECLAIM_FULL
;
3526 * Do not scan if the allocation should not be delayed.
3528 if (!(gfp_mask
& __GFP_WAIT
) || (current
->flags
& PF_MEMALLOC
))
3529 return ZONE_RECLAIM_NOSCAN
;
3532 * Only run zone reclaim on the local zone or on zones that do not
3533 * have associated processors. This will favor the local processor
3534 * over remote processors and spread off node memory allocations
3535 * as wide as possible.
3537 node_id
= zone_to_nid(zone
);
3538 if (node_state(node_id
, N_CPU
) && node_id
!= numa_node_id())
3539 return ZONE_RECLAIM_NOSCAN
;
3541 if (zone_test_and_set_flag(zone
, ZONE_RECLAIM_LOCKED
))
3542 return ZONE_RECLAIM_NOSCAN
;
3544 ret
= __zone_reclaim(zone
, gfp_mask
, order
);
3545 zone_clear_flag(zone
, ZONE_RECLAIM_LOCKED
);
3548 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
3555 * page_evictable - test whether a page is evictable
3556 * @page: the page to test
3558 * Test whether page is evictable--i.e., should be placed on active/inactive
3559 * lists vs unevictable list.
3561 * Reasons page might not be evictable:
3562 * (1) page's mapping marked unevictable
3563 * (2) page is part of an mlocked VMA
3566 int page_evictable(struct page
*page
)
3568 return !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
3573 * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
3574 * @pages: array of pages to check
3575 * @nr_pages: number of pages to check
3577 * Checks pages for evictability and moves them to the appropriate lru list.
3579 * This function is only used for SysV IPC SHM_UNLOCK.
3581 void check_move_unevictable_pages(struct page
**pages
, int nr_pages
)
3583 struct lruvec
*lruvec
;
3584 struct zone
*zone
= NULL
;
3589 for (i
= 0; i
< nr_pages
; i
++) {
3590 struct page
*page
= pages
[i
];
3591 struct zone
*pagezone
;
3594 pagezone
= page_zone(page
);
3595 if (pagezone
!= zone
) {
3597 spin_unlock_irq(&zone
->lru_lock
);
3599 spin_lock_irq(&zone
->lru_lock
);
3601 lruvec
= mem_cgroup_page_lruvec(page
, zone
);
3603 if (!PageLRU(page
) || !PageUnevictable(page
))
3606 if (page_evictable(page
)) {
3607 enum lru_list lru
= page_lru_base_type(page
);
3609 VM_BUG_ON(PageActive(page
));
3610 ClearPageUnevictable(page
);
3611 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
3612 add_page_to_lru_list(page
, lruvec
, lru
);
3618 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
3619 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
3620 spin_unlock_irq(&zone
->lru_lock
);
3623 #endif /* CONFIG_SHMEM */
3625 static void warn_scan_unevictable_pages(void)
3627 printk_once(KERN_WARNING
3628 "%s: The scan_unevictable_pages sysctl/node-interface has been "
3629 "disabled for lack of a legitimate use case. If you have "
3630 "one, please send an email to linux-mm@kvack.org.\n",
3635 * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
3636 * all nodes' unevictable lists for evictable pages
3638 unsigned long scan_unevictable_pages
;
3640 int scan_unevictable_handler(struct ctl_table
*table
, int write
,
3641 void __user
*buffer
,
3642 size_t *length
, loff_t
*ppos
)
3644 warn_scan_unevictable_pages();
3645 proc_doulongvec_minmax(table
, write
, buffer
, length
, ppos
);
3646 scan_unevictable_pages
= 0;
3652 * per node 'scan_unevictable_pages' attribute. On demand re-scan of
3653 * a specified node's per zone unevictable lists for evictable pages.
3656 static ssize_t
read_scan_unevictable_node(struct device
*dev
,
3657 struct device_attribute
*attr
,
3660 warn_scan_unevictable_pages();
3661 return sprintf(buf
, "0\n"); /* always zero; should fit... */
3664 static ssize_t
write_scan_unevictable_node(struct device
*dev
,
3665 struct device_attribute
*attr
,
3666 const char *buf
, size_t count
)
3668 warn_scan_unevictable_pages();
3673 static DEVICE_ATTR(scan_unevictable_pages
, S_IRUGO
| S_IWUSR
,
3674 read_scan_unevictable_node
,
3675 write_scan_unevictable_node
);
3677 int scan_unevictable_register_node(struct node
*node
)
3679 return device_create_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);
3682 void scan_unevictable_unregister_node(struct node
*node
)
3684 device_remove_file(&node
->dev
, &dev_attr_scan_unevictable_pages
);