1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
7 * Swap reorganised 29.12.95, Stephen Tweedie.
8 * kswapd added: 7.1.96 sct
9 * Removed kswapd_ctl limits, and swap out as many pages as needed
10 * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
11 * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
12 * Multiqueue VM started 5.8.00, Rik van Riel.
15 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 #include <linux/sched/mm.h>
19 #include <linux/module.h>
20 #include <linux/gfp.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/swap.h>
23 #include <linux/pagemap.h>
24 #include <linux/init.h>
25 #include <linux/highmem.h>
26 #include <linux/vmpressure.h>
27 #include <linux/vmstat.h>
28 #include <linux/file.h>
29 #include <linux/writeback.h>
30 #include <linux/blkdev.h>
31 #include <linux/buffer_head.h> /* for try_to_release_page(),
32 buffer_heads_over_limit */
33 #include <linux/mm_inline.h>
34 #include <linux/backing-dev.h>
35 #include <linux/rmap.h>
36 #include <linux/topology.h>
37 #include <linux/cpu.h>
38 #include <linux/cpuset.h>
39 #include <linux/compaction.h>
40 #include <linux/notifier.h>
41 #include <linux/rwsem.h>
42 #include <linux/delay.h>
43 #include <linux/kthread.h>
44 #include <linux/freezer.h>
45 #include <linux/memcontrol.h>
46 #include <linux/delayacct.h>
47 #include <linux/sysctl.h>
48 #include <linux/oom.h>
49 #include <linux/pagevec.h>
50 #include <linux/prefetch.h>
51 #include <linux/printk.h>
52 #include <linux/dax.h>
53 #include <linux/psi.h>
55 #include <asm/tlbflush.h>
56 #include <asm/div64.h>
58 #include <linux/swapops.h>
59 #include <linux/balloon_compaction.h>
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/vmscan.h>
67 /* How many pages shrink_list() should reclaim */
68 unsigned long nr_to_reclaim
;
71 * Nodemask of nodes allowed by the caller. If NULL, all nodes
77 * The memory cgroup that hit its limit and as a result is the
78 * primary target of this reclaim invocation.
80 struct mem_cgroup
*target_mem_cgroup
;
82 /* Writepage batching in laptop mode; RECLAIM_WRITE */
83 unsigned int may_writepage
:1;
85 /* Can mapped pages be reclaimed? */
86 unsigned int may_unmap
:1;
88 /* Can pages be swapped as part of reclaim? */
89 unsigned int may_swap
:1;
91 /* e.g. boosted watermark reclaim leaves slabs alone */
92 unsigned int may_shrinkslab
:1;
95 * Cgroups are not reclaimed below their configured memory.low,
96 * unless we threaten to OOM. If any cgroups are skipped due to
97 * memory.low and nothing was reclaimed, go back for memory.low.
99 unsigned int memcg_low_reclaim
:1;
100 unsigned int memcg_low_skipped
:1;
102 unsigned int hibernation_mode
:1;
104 /* One of the zones is ready for compaction */
105 unsigned int compaction_ready
:1;
107 /* Allocation order */
110 /* Scan (total_size >> priority) pages at once */
113 /* The highest zone to isolate pages for reclaim from */
116 /* This context's GFP mask */
119 /* Incremented by the number of inactive pages that were scanned */
120 unsigned long nr_scanned
;
122 /* Number of pages freed so far during a call to shrink_zones() */
123 unsigned long nr_reclaimed
;
127 unsigned int unqueued_dirty
;
128 unsigned int congested
;
129 unsigned int writeback
;
130 unsigned int immediate
;
131 unsigned int file_taken
;
135 /* for recording the reclaimed slab by now */
136 struct reclaim_state reclaim_state
;
139 #ifdef ARCH_HAS_PREFETCH
140 #define prefetch_prev_lru_page(_page, _base, _field) \
142 if ((_page)->lru.prev != _base) { \
145 prev = lru_to_page(&(_page->lru)); \
146 prefetch(&prev->_field); \
150 #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
153 #ifdef ARCH_HAS_PREFETCHW
154 #define prefetchw_prev_lru_page(_page, _base, _field) \
156 if ((_page)->lru.prev != _base) { \
159 prev = lru_to_page(&(_page->lru)); \
160 prefetchw(&prev->_field); \
164 #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
168 * From 0 .. 100. Higher means more swappy.
170 int vm_swappiness
= 60;
172 * The total number of pages which are beyond the high watermark within all
175 unsigned long vm_total_pages
;
177 static LIST_HEAD(shrinker_list
);
178 static DECLARE_RWSEM(shrinker_rwsem
);
180 #ifdef CONFIG_MEMCG_KMEM
183 * We allow subsystems to populate their shrinker-related
184 * LRU lists before register_shrinker_prepared() is called
185 * for the shrinker, since we don't want to impose
186 * restrictions on their internal registration order.
187 * In this case shrink_slab_memcg() may find corresponding
188 * bit is set in the shrinkers map.
190 * This value is used by the function to detect registering
191 * shrinkers and to skip do_shrink_slab() calls for them.
193 #define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
195 static DEFINE_IDR(shrinker_idr
);
196 static int shrinker_nr_max
;
198 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
200 int id
, ret
= -ENOMEM
;
202 down_write(&shrinker_rwsem
);
203 /* This may call shrinker, so it must use down_read_trylock() */
204 id
= idr_alloc(&shrinker_idr
, SHRINKER_REGISTERING
, 0, 0, GFP_KERNEL
);
208 if (id
>= shrinker_nr_max
) {
209 if (memcg_expand_shrinker_maps(id
)) {
210 idr_remove(&shrinker_idr
, id
);
214 shrinker_nr_max
= id
+ 1;
219 up_write(&shrinker_rwsem
);
223 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
225 int id
= shrinker
->id
;
229 down_write(&shrinker_rwsem
);
230 idr_remove(&shrinker_idr
, id
);
231 up_write(&shrinker_rwsem
);
233 #else /* CONFIG_MEMCG_KMEM */
234 static int prealloc_memcg_shrinker(struct shrinker
*shrinker
)
239 static void unregister_memcg_shrinker(struct shrinker
*shrinker
)
242 #endif /* CONFIG_MEMCG_KMEM */
244 static void set_task_reclaim_state(struct task_struct
*task
,
245 struct reclaim_state
*rs
)
247 /* Check for an overwrite */
248 WARN_ON_ONCE(rs
&& task
->reclaim_state
);
250 /* Check for the nulling of an already-nulled member */
251 WARN_ON_ONCE(!rs
&& !task
->reclaim_state
);
253 task
->reclaim_state
= rs
;
257 static bool global_reclaim(struct scan_control
*sc
)
259 return !sc
->target_mem_cgroup
;
263 * sane_reclaim - is the usual dirty throttling mechanism operational?
264 * @sc: scan_control in question
266 * The normal page dirty throttling mechanism in balance_dirty_pages() is
267 * completely broken with the legacy memcg and direct stalling in
268 * shrink_page_list() is used for throttling instead, which lacks all the
269 * niceties such as fairness, adaptive pausing, bandwidth proportional
270 * allocation and configurability.
272 * This function tests whether the vmscan currently in progress can assume
273 * that the normal dirty throttling mechanism is operational.
275 static bool sane_reclaim(struct scan_control
*sc
)
277 struct mem_cgroup
*memcg
= sc
->target_mem_cgroup
;
281 #ifdef CONFIG_CGROUP_WRITEBACK
282 if (cgroup_subsys_on_dfl(memory_cgrp_subsys
))
288 static void set_memcg_congestion(pg_data_t
*pgdat
,
289 struct mem_cgroup
*memcg
,
292 struct mem_cgroup_per_node
*mn
;
297 mn
= mem_cgroup_nodeinfo(memcg
, pgdat
->node_id
);
298 WRITE_ONCE(mn
->congested
, congested
);
301 static bool memcg_congested(pg_data_t
*pgdat
,
302 struct mem_cgroup
*memcg
)
304 struct mem_cgroup_per_node
*mn
;
306 mn
= mem_cgroup_nodeinfo(memcg
, pgdat
->node_id
);
307 return READ_ONCE(mn
->congested
);
311 static bool global_reclaim(struct scan_control
*sc
)
316 static bool sane_reclaim(struct scan_control
*sc
)
321 static inline void set_memcg_congestion(struct pglist_data
*pgdat
,
322 struct mem_cgroup
*memcg
, bool congested
)
326 static inline bool memcg_congested(struct pglist_data
*pgdat
,
327 struct mem_cgroup
*memcg
)
335 * This misses isolated pages which are not accounted for to save counters.
336 * As the data only determines if reclaim or compaction continues, it is
337 * not expected that isolated pages will be a dominating factor.
339 unsigned long zone_reclaimable_pages(struct zone
*zone
)
343 nr
= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_FILE
) +
344 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_FILE
);
345 if (get_nr_swap_pages() > 0)
346 nr
+= zone_page_state_snapshot(zone
, NR_ZONE_INACTIVE_ANON
) +
347 zone_page_state_snapshot(zone
, NR_ZONE_ACTIVE_ANON
);
353 * lruvec_lru_size - Returns the number of pages on the given LRU list.
354 * @lruvec: lru vector
356 * @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
358 unsigned long lruvec_lru_size(struct lruvec
*lruvec
, enum lru_list lru
, int zone_idx
)
360 unsigned long lru_size
;
363 if (!mem_cgroup_disabled())
364 lru_size
= lruvec_page_state_local(lruvec
, NR_LRU_BASE
+ lru
);
366 lru_size
= node_page_state(lruvec_pgdat(lruvec
), NR_LRU_BASE
+ lru
);
368 for (zid
= zone_idx
+ 1; zid
< MAX_NR_ZONES
; zid
++) {
369 struct zone
*zone
= &lruvec_pgdat(lruvec
)->node_zones
[zid
];
372 if (!managed_zone(zone
))
375 if (!mem_cgroup_disabled())
376 size
= mem_cgroup_get_zone_lru_size(lruvec
, lru
, zid
);
378 size
= zone_page_state(&lruvec_pgdat(lruvec
)->node_zones
[zid
],
379 NR_ZONE_LRU_BASE
+ lru
);
380 lru_size
-= min(size
, lru_size
);
388 * Add a shrinker callback to be called from the vm.
390 int prealloc_shrinker(struct shrinker
*shrinker
)
392 unsigned int size
= sizeof(*shrinker
->nr_deferred
);
394 if (shrinker
->flags
& SHRINKER_NUMA_AWARE
)
397 shrinker
->nr_deferred
= kzalloc(size
, GFP_KERNEL
);
398 if (!shrinker
->nr_deferred
)
401 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
) {
402 if (prealloc_memcg_shrinker(shrinker
))
409 kfree(shrinker
->nr_deferred
);
410 shrinker
->nr_deferred
= NULL
;
414 void free_prealloced_shrinker(struct shrinker
*shrinker
)
416 if (!shrinker
->nr_deferred
)
419 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
420 unregister_memcg_shrinker(shrinker
);
422 kfree(shrinker
->nr_deferred
);
423 shrinker
->nr_deferred
= NULL
;
426 void register_shrinker_prepared(struct shrinker
*shrinker
)
428 down_write(&shrinker_rwsem
);
429 list_add_tail(&shrinker
->list
, &shrinker_list
);
430 #ifdef CONFIG_MEMCG_KMEM
431 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
432 idr_replace(&shrinker_idr
, shrinker
, shrinker
->id
);
434 up_write(&shrinker_rwsem
);
437 int register_shrinker(struct shrinker
*shrinker
)
439 int err
= prealloc_shrinker(shrinker
);
443 register_shrinker_prepared(shrinker
);
446 EXPORT_SYMBOL(register_shrinker
);
451 void unregister_shrinker(struct shrinker
*shrinker
)
453 if (!shrinker
->nr_deferred
)
455 if (shrinker
->flags
& SHRINKER_MEMCG_AWARE
)
456 unregister_memcg_shrinker(shrinker
);
457 down_write(&shrinker_rwsem
);
458 list_del(&shrinker
->list
);
459 up_write(&shrinker_rwsem
);
460 kfree(shrinker
->nr_deferred
);
461 shrinker
->nr_deferred
= NULL
;
463 EXPORT_SYMBOL(unregister_shrinker
);
465 #define SHRINK_BATCH 128
467 static unsigned long do_shrink_slab(struct shrink_control
*shrinkctl
,
468 struct shrinker
*shrinker
, int priority
)
470 unsigned long freed
= 0;
471 unsigned long long delta
;
476 int nid
= shrinkctl
->nid
;
477 long batch_size
= shrinker
->batch
? shrinker
->batch
479 long scanned
= 0, next_deferred
;
481 if (!(shrinker
->flags
& SHRINKER_NUMA_AWARE
))
484 freeable
= shrinker
->count_objects(shrinker
, shrinkctl
);
485 if (freeable
== 0 || freeable
== SHRINK_EMPTY
)
489 * copy the current shrinker scan count into a local variable
490 * and zero it so that other concurrent shrinker invocations
491 * don't also do this scanning work.
493 nr
= atomic_long_xchg(&shrinker
->nr_deferred
[nid
], 0);
496 if (shrinker
->seeks
) {
497 delta
= freeable
>> priority
;
499 do_div(delta
, shrinker
->seeks
);
502 * These objects don't require any IO to create. Trim
503 * them aggressively under memory pressure to keep
504 * them from causing refetches in the IO caches.
506 delta
= freeable
/ 2;
510 if (total_scan
< 0) {
511 pr_err("shrink_slab: %pS negative objects to delete nr=%ld\n",
512 shrinker
->scan_objects
, total_scan
);
513 total_scan
= freeable
;
516 next_deferred
= total_scan
;
519 * We need to avoid excessive windup on filesystem shrinkers
520 * due to large numbers of GFP_NOFS allocations causing the
521 * shrinkers to return -1 all the time. This results in a large
522 * nr being built up so when a shrink that can do some work
523 * comes along it empties the entire cache due to nr >>>
524 * freeable. This is bad for sustaining a working set in
527 * Hence only allow the shrinker to scan the entire cache when
528 * a large delta change is calculated directly.
530 if (delta
< freeable
/ 4)
531 total_scan
= min(total_scan
, freeable
/ 2);
534 * Avoid risking looping forever due to too large nr value:
535 * never try to free more than twice the estimate number of
538 if (total_scan
> freeable
* 2)
539 total_scan
= freeable
* 2;
541 trace_mm_shrink_slab_start(shrinker
, shrinkctl
, nr
,
542 freeable
, delta
, total_scan
, priority
);
545 * Normally, we should not scan less than batch_size objects in one
546 * pass to avoid too frequent shrinker calls, but if the slab has less
547 * than batch_size objects in total and we are really tight on memory,
548 * we will try to reclaim all available objects, otherwise we can end
549 * up failing allocations although there are plenty of reclaimable
550 * objects spread over several slabs with usage less than the
553 * We detect the "tight on memory" situations by looking at the total
554 * number of objects we want to scan (total_scan). If it is greater
555 * than the total number of objects on slab (freeable), we must be
556 * scanning at high prio and therefore should try to reclaim as much as
559 while (total_scan
>= batch_size
||
560 total_scan
>= freeable
) {
562 unsigned long nr_to_scan
= min(batch_size
, total_scan
);
564 shrinkctl
->nr_to_scan
= nr_to_scan
;
565 shrinkctl
->nr_scanned
= nr_to_scan
;
566 ret
= shrinker
->scan_objects(shrinker
, shrinkctl
);
567 if (ret
== SHRINK_STOP
)
571 count_vm_events(SLABS_SCANNED
, shrinkctl
->nr_scanned
);
572 total_scan
-= shrinkctl
->nr_scanned
;
573 scanned
+= shrinkctl
->nr_scanned
;
578 if (next_deferred
>= scanned
)
579 next_deferred
-= scanned
;
583 * move the unused scan count back into the shrinker in a
584 * manner that handles concurrent updates. If we exhausted the
585 * scan, there is no need to do an update.
587 if (next_deferred
> 0)
588 new_nr
= atomic_long_add_return(next_deferred
,
589 &shrinker
->nr_deferred
[nid
]);
591 new_nr
= atomic_long_read(&shrinker
->nr_deferred
[nid
]);
593 trace_mm_shrink_slab_end(shrinker
, nid
, freed
, nr
, new_nr
, total_scan
);
597 #ifdef CONFIG_MEMCG_KMEM
598 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
599 struct mem_cgroup
*memcg
, int priority
)
601 struct memcg_shrinker_map
*map
;
602 unsigned long ret
, freed
= 0;
605 if (!memcg_kmem_enabled() || !mem_cgroup_online(memcg
))
608 if (!down_read_trylock(&shrinker_rwsem
))
611 map
= rcu_dereference_protected(memcg
->nodeinfo
[nid
]->shrinker_map
,
616 for_each_set_bit(i
, map
->map
, shrinker_nr_max
) {
617 struct shrink_control sc
= {
618 .gfp_mask
= gfp_mask
,
622 struct shrinker
*shrinker
;
624 shrinker
= idr_find(&shrinker_idr
, i
);
625 if (unlikely(!shrinker
|| shrinker
== SHRINKER_REGISTERING
)) {
627 clear_bit(i
, map
->map
);
631 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
632 if (ret
== SHRINK_EMPTY
) {
633 clear_bit(i
, map
->map
);
635 * After the shrinker reported that it had no objects to
636 * free, but before we cleared the corresponding bit in
637 * the memcg shrinker map, a new object might have been
638 * added. To make sure, we have the bit set in this
639 * case, we invoke the shrinker one more time and reset
640 * the bit if it reports that it is not empty anymore.
641 * The memory barrier here pairs with the barrier in
642 * memcg_set_shrinker_bit():
644 * list_lru_add() shrink_slab_memcg()
645 * list_add_tail() clear_bit()
647 * set_bit() do_shrink_slab()
649 smp_mb__after_atomic();
650 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
651 if (ret
== SHRINK_EMPTY
)
654 memcg_set_shrinker_bit(memcg
, nid
, i
);
658 if (rwsem_is_contended(&shrinker_rwsem
)) {
664 up_read(&shrinker_rwsem
);
667 #else /* CONFIG_MEMCG_KMEM */
668 static unsigned long shrink_slab_memcg(gfp_t gfp_mask
, int nid
,
669 struct mem_cgroup
*memcg
, int priority
)
673 #endif /* CONFIG_MEMCG_KMEM */
676 * shrink_slab - shrink slab caches
677 * @gfp_mask: allocation context
678 * @nid: node whose slab caches to target
679 * @memcg: memory cgroup whose slab caches to target
680 * @priority: the reclaim priority
682 * Call the shrink functions to age shrinkable caches.
684 * @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
685 * unaware shrinkers will receive a node id of 0 instead.
687 * @memcg specifies the memory cgroup to target. Unaware shrinkers
688 * are called only if it is the root cgroup.
690 * @priority is sc->priority, we take the number of objects and >> by priority
691 * in order to get the scan target.
693 * Returns the number of reclaimed slab objects.
695 static unsigned long shrink_slab(gfp_t gfp_mask
, int nid
,
696 struct mem_cgroup
*memcg
,
699 unsigned long ret
, freed
= 0;
700 struct shrinker
*shrinker
;
703 * The root memcg might be allocated even though memcg is disabled
704 * via "cgroup_disable=memory" boot parameter. This could make
705 * mem_cgroup_is_root() return false, then just run memcg slab
706 * shrink, but skip global shrink. This may result in premature
709 if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg
))
710 return shrink_slab_memcg(gfp_mask
, nid
, memcg
, priority
);
712 if (!down_read_trylock(&shrinker_rwsem
))
715 list_for_each_entry(shrinker
, &shrinker_list
, list
) {
716 struct shrink_control sc
= {
717 .gfp_mask
= gfp_mask
,
722 ret
= do_shrink_slab(&sc
, shrinker
, priority
);
723 if (ret
== SHRINK_EMPTY
)
727 * Bail out if someone want to register a new shrinker to
728 * prevent the regsitration from being stalled for long periods
729 * by parallel ongoing shrinking.
731 if (rwsem_is_contended(&shrinker_rwsem
)) {
737 up_read(&shrinker_rwsem
);
743 void drop_slab_node(int nid
)
748 struct mem_cgroup
*memcg
= NULL
;
751 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
753 freed
+= shrink_slab(GFP_KERNEL
, nid
, memcg
, 0);
754 } while ((memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
)) != NULL
);
755 } while (freed
> 10);
762 for_each_online_node(nid
)
766 static inline int is_page_cache_freeable(struct page
*page
)
769 * A freeable page cache page is referenced only by the caller
770 * that isolated the page, the page cache and optional buffer
771 * heads at page->private.
773 int page_cache_pins
= PageTransHuge(page
) && PageSwapCache(page
) ?
775 return page_count(page
) - page_has_private(page
) == 1 + page_cache_pins
;
778 static int may_write_to_inode(struct inode
*inode
, struct scan_control
*sc
)
780 if (current
->flags
& PF_SWAPWRITE
)
782 if (!inode_write_congested(inode
))
784 if (inode_to_bdi(inode
) == current
->backing_dev_info
)
790 * We detected a synchronous write error writing a page out. Probably
791 * -ENOSPC. We need to propagate that into the address_space for a subsequent
792 * fsync(), msync() or close().
794 * The tricky part is that after writepage we cannot touch the mapping: nothing
795 * prevents it from being freed up. But we have a ref on the page and once
796 * that page is locked, the mapping is pinned.
798 * We're allowed to run sleeping lock_page() here because we know the caller has
801 static void handle_write_error(struct address_space
*mapping
,
802 struct page
*page
, int error
)
805 if (page_mapping(page
) == mapping
)
806 mapping_set_error(mapping
, error
);
810 /* possible outcome of pageout() */
812 /* failed to write page out, page is locked */
814 /* move page to the active list, page is locked */
816 /* page has been sent to the disk successfully, page is unlocked */
818 /* page is clean and locked */
823 * pageout is called by shrink_page_list() for each dirty page.
824 * Calls ->writepage().
826 static pageout_t
pageout(struct page
*page
, struct address_space
*mapping
,
827 struct scan_control
*sc
)
830 * If the page is dirty, only perform writeback if that write
831 * will be non-blocking. To prevent this allocation from being
832 * stalled by pagecache activity. But note that there may be
833 * stalls if we need to run get_block(). We could test
834 * PagePrivate for that.
836 * If this process is currently in __generic_file_write_iter() against
837 * this page's queue, we can perform writeback even if that
840 * If the page is swapcache, write it back even if that would
841 * block, for some throttling. This happens by accident, because
842 * swap_backing_dev_info is bust: it doesn't reflect the
843 * congestion state of the swapdevs. Easy to fix, if needed.
845 if (!is_page_cache_freeable(page
))
849 * Some data journaling orphaned pages can have
850 * page->mapping == NULL while being dirty with clean buffers.
852 if (page_has_private(page
)) {
853 if (try_to_free_buffers(page
)) {
854 ClearPageDirty(page
);
855 pr_info("%s: orphaned page\n", __func__
);
861 if (mapping
->a_ops
->writepage
== NULL
)
862 return PAGE_ACTIVATE
;
863 if (!may_write_to_inode(mapping
->host
, sc
))
866 if (clear_page_dirty_for_io(page
)) {
868 struct writeback_control wbc
= {
869 .sync_mode
= WB_SYNC_NONE
,
870 .nr_to_write
= SWAP_CLUSTER_MAX
,
872 .range_end
= LLONG_MAX
,
876 SetPageReclaim(page
);
877 res
= mapping
->a_ops
->writepage(page
, &wbc
);
879 handle_write_error(mapping
, page
, res
);
880 if (res
== AOP_WRITEPAGE_ACTIVATE
) {
881 ClearPageReclaim(page
);
882 return PAGE_ACTIVATE
;
885 if (!PageWriteback(page
)) {
886 /* synchronous write or broken a_ops? */
887 ClearPageReclaim(page
);
889 trace_mm_vmscan_writepage(page
);
890 inc_node_page_state(page
, NR_VMSCAN_WRITE
);
898 * Same as remove_mapping, but if the page is removed from the mapping, it
899 * gets returned with a refcount of 0.
901 static int __remove_mapping(struct address_space
*mapping
, struct page
*page
,
907 BUG_ON(!PageLocked(page
));
908 BUG_ON(mapping
!= page_mapping(page
));
910 xa_lock_irqsave(&mapping
->i_pages
, flags
);
912 * The non racy check for a busy page.
914 * Must be careful with the order of the tests. When someone has
915 * a ref to the page, it may be possible that they dirty it then
916 * drop the reference. So if PageDirty is tested before page_count
917 * here, then the following race may occur:
919 * get_user_pages(&page);
920 * [user mapping goes away]
922 * !PageDirty(page) [good]
923 * SetPageDirty(page);
925 * !page_count(page) [good, discard it]
927 * [oops, our write_to data is lost]
929 * Reversing the order of the tests ensures such a situation cannot
930 * escape unnoticed. The smp_rmb is needed to ensure the page->flags
931 * load is not satisfied before that of page->_refcount.
933 * Note that if SetPageDirty is always performed via set_page_dirty,
934 * and thus under the i_pages lock, then this ordering is not required.
936 if (unlikely(PageTransHuge(page
)) && PageSwapCache(page
))
937 refcount
= 1 + HPAGE_PMD_NR
;
940 if (!page_ref_freeze(page
, refcount
))
942 /* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
943 if (unlikely(PageDirty(page
))) {
944 page_ref_unfreeze(page
, refcount
);
948 if (PageSwapCache(page
)) {
949 swp_entry_t swap
= { .val
= page_private(page
) };
950 mem_cgroup_swapout(page
, swap
);
951 __delete_from_swap_cache(page
, swap
);
952 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
953 put_swap_page(page
, swap
);
955 void (*freepage
)(struct page
*);
958 freepage
= mapping
->a_ops
->freepage
;
960 * Remember a shadow entry for reclaimed file cache in
961 * order to detect refaults, thus thrashing, later on.
963 * But don't store shadows in an address space that is
964 * already exiting. This is not just an optizimation,
965 * inode reclaim needs to empty out the radix tree or
966 * the nodes are lost. Don't plant shadows behind its
969 * We also don't store shadows for DAX mappings because the
970 * only page cache pages found in these are zero pages
971 * covering holes, and because we don't want to mix DAX
972 * exceptional entries and shadow exceptional entries in the
973 * same address_space.
975 if (reclaimed
&& page_is_file_cache(page
) &&
976 !mapping_exiting(mapping
) && !dax_mapping(mapping
))
977 shadow
= workingset_eviction(page
);
978 __delete_from_page_cache(page
, shadow
);
979 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
981 if (freepage
!= NULL
)
988 xa_unlock_irqrestore(&mapping
->i_pages
, flags
);
993 * Attempt to detach a locked page from its ->mapping. If it is dirty or if
994 * someone else has a ref on the page, abort and return 0. If it was
995 * successfully detached, return 1. Assumes the caller has a single ref on
998 int remove_mapping(struct address_space
*mapping
, struct page
*page
)
1000 if (__remove_mapping(mapping
, page
, false)) {
1002 * Unfreezing the refcount with 1 rather than 2 effectively
1003 * drops the pagecache ref for us without requiring another
1006 page_ref_unfreeze(page
, 1);
1013 * putback_lru_page - put previously isolated page onto appropriate LRU list
1014 * @page: page to be put back to appropriate lru list
1016 * Add previously isolated @page to appropriate LRU list.
1017 * Page may still be unevictable for other reasons.
1019 * lru_lock must not be held, interrupts must be enabled.
1021 void putback_lru_page(struct page
*page
)
1023 lru_cache_add(page
);
1024 put_page(page
); /* drop ref from isolate */
1027 enum page_references
{
1029 PAGEREF_RECLAIM_CLEAN
,
1034 static enum page_references
page_check_references(struct page
*page
,
1035 struct scan_control
*sc
)
1037 int referenced_ptes
, referenced_page
;
1038 unsigned long vm_flags
;
1040 referenced_ptes
= page_referenced(page
, 1, sc
->target_mem_cgroup
,
1042 referenced_page
= TestClearPageReferenced(page
);
1045 * Mlock lost the isolation race with us. Let try_to_unmap()
1046 * move the page to the unevictable list.
1048 if (vm_flags
& VM_LOCKED
)
1049 return PAGEREF_RECLAIM
;
1051 if (referenced_ptes
) {
1052 if (PageSwapBacked(page
))
1053 return PAGEREF_ACTIVATE
;
1055 * All mapped pages start out with page table
1056 * references from the instantiating fault, so we need
1057 * to look twice if a mapped file page is used more
1060 * Mark it and spare it for another trip around the
1061 * inactive list. Another page table reference will
1062 * lead to its activation.
1064 * Note: the mark is set for activated pages as well
1065 * so that recently deactivated but used pages are
1066 * quickly recovered.
1068 SetPageReferenced(page
);
1070 if (referenced_page
|| referenced_ptes
> 1)
1071 return PAGEREF_ACTIVATE
;
1074 * Activate file-backed executable pages after first usage.
1076 if (vm_flags
& VM_EXEC
)
1077 return PAGEREF_ACTIVATE
;
1079 return PAGEREF_KEEP
;
1082 /* Reclaim if clean, defer dirty pages to writeback */
1083 if (referenced_page
&& !PageSwapBacked(page
))
1084 return PAGEREF_RECLAIM_CLEAN
;
1086 return PAGEREF_RECLAIM
;
1089 /* Check if a page is dirty or under writeback */
1090 static void page_check_dirty_writeback(struct page
*page
,
1091 bool *dirty
, bool *writeback
)
1093 struct address_space
*mapping
;
1096 * Anonymous pages are not handled by flushers and must be written
1097 * from reclaim context. Do not stall reclaim based on them
1099 if (!page_is_file_cache(page
) ||
1100 (PageAnon(page
) && !PageSwapBacked(page
))) {
1106 /* By default assume that the page flags are accurate */
1107 *dirty
= PageDirty(page
);
1108 *writeback
= PageWriteback(page
);
1110 /* Verify dirty/writeback state if the filesystem supports it */
1111 if (!page_has_private(page
))
1114 mapping
= page_mapping(page
);
1115 if (mapping
&& mapping
->a_ops
->is_dirty_writeback
)
1116 mapping
->a_ops
->is_dirty_writeback(page
, dirty
, writeback
);
1120 * shrink_page_list() returns the number of reclaimed pages
1122 static unsigned long shrink_page_list(struct list_head
*page_list
,
1123 struct pglist_data
*pgdat
,
1124 struct scan_control
*sc
,
1125 enum ttu_flags ttu_flags
,
1126 struct reclaim_stat
*stat
,
1129 LIST_HEAD(ret_pages
);
1130 LIST_HEAD(free_pages
);
1131 unsigned nr_reclaimed
= 0;
1132 unsigned pgactivate
= 0;
1134 memset(stat
, 0, sizeof(*stat
));
1137 while (!list_empty(page_list
)) {
1138 struct address_space
*mapping
;
1141 enum page_references references
= PAGEREF_RECLAIM_CLEAN
;
1142 bool dirty
, writeback
;
1143 unsigned int nr_pages
;
1147 page
= lru_to_page(page_list
);
1148 list_del(&page
->lru
);
1150 if (!trylock_page(page
))
1153 VM_BUG_ON_PAGE(PageActive(page
), page
);
1155 nr_pages
= 1 << compound_order(page
);
1157 /* Account the number of base pages even though THP */
1158 sc
->nr_scanned
+= nr_pages
;
1160 if (unlikely(!page_evictable(page
)))
1161 goto activate_locked
;
1163 if (!sc
->may_unmap
&& page_mapped(page
))
1166 may_enter_fs
= (sc
->gfp_mask
& __GFP_FS
) ||
1167 (PageSwapCache(page
) && (sc
->gfp_mask
& __GFP_IO
));
1170 * The number of dirty pages determines if a node is marked
1171 * reclaim_congested which affects wait_iff_congested. kswapd
1172 * will stall and start writing pages if the tail of the LRU
1173 * is all dirty unqueued pages.
1175 page_check_dirty_writeback(page
, &dirty
, &writeback
);
1176 if (dirty
|| writeback
)
1179 if (dirty
&& !writeback
)
1180 stat
->nr_unqueued_dirty
++;
1183 * Treat this page as congested if the underlying BDI is or if
1184 * pages are cycling through the LRU so quickly that the
1185 * pages marked for immediate reclaim are making it to the
1186 * end of the LRU a second time.
1188 mapping
= page_mapping(page
);
1189 if (((dirty
|| writeback
) && mapping
&&
1190 inode_write_congested(mapping
->host
)) ||
1191 (writeback
&& PageReclaim(page
)))
1192 stat
->nr_congested
++;
1195 * If a page at the tail of the LRU is under writeback, there
1196 * are three cases to consider.
1198 * 1) If reclaim is encountering an excessive number of pages
1199 * under writeback and this page is both under writeback and
1200 * PageReclaim then it indicates that pages are being queued
1201 * for IO but are being recycled through the LRU before the
1202 * IO can complete. Waiting on the page itself risks an
1203 * indefinite stall if it is impossible to writeback the
1204 * page due to IO error or disconnected storage so instead
1205 * note that the LRU is being scanned too quickly and the
1206 * caller can stall after page list has been processed.
1208 * 2) Global or new memcg reclaim encounters a page that is
1209 * not marked for immediate reclaim, or the caller does not
1210 * have __GFP_FS (or __GFP_IO if it's simply going to swap,
1211 * not to fs). In this case mark the page for immediate
1212 * reclaim and continue scanning.
1214 * Require may_enter_fs because we would wait on fs, which
1215 * may not have submitted IO yet. And the loop driver might
1216 * enter reclaim, and deadlock if it waits on a page for
1217 * which it is needed to do the write (loop masks off
1218 * __GFP_IO|__GFP_FS for this reason); but more thought
1219 * would probably show more reasons.
1221 * 3) Legacy memcg encounters a page that is already marked
1222 * PageReclaim. memcg does not have any dirty pages
1223 * throttling so we could easily OOM just because too many
1224 * pages are in writeback and there is nothing else to
1225 * reclaim. Wait for the writeback to complete.
1227 * In cases 1) and 2) we activate the pages to get them out of
1228 * the way while we continue scanning for clean pages on the
1229 * inactive list and refilling from the active list. The
1230 * observation here is that waiting for disk writes is more
1231 * expensive than potentially causing reloads down the line.
1232 * Since they're marked for immediate reclaim, they won't put
1233 * memory pressure on the cache working set any longer than it
1234 * takes to write them to disk.
1236 if (PageWriteback(page
)) {
1238 if (current_is_kswapd() &&
1239 PageReclaim(page
) &&
1240 test_bit(PGDAT_WRITEBACK
, &pgdat
->flags
)) {
1241 stat
->nr_immediate
++;
1242 goto activate_locked
;
1245 } else if (sane_reclaim(sc
) ||
1246 !PageReclaim(page
) || !may_enter_fs
) {
1248 * This is slightly racy - end_page_writeback()
1249 * might have just cleared PageReclaim, then
1250 * setting PageReclaim here end up interpreted
1251 * as PageReadahead - but that does not matter
1252 * enough to care. What we do want is for this
1253 * page to have PageReclaim set next time memcg
1254 * reclaim reaches the tests above, so it will
1255 * then wait_on_page_writeback() to avoid OOM;
1256 * and it's also appropriate in global reclaim.
1258 SetPageReclaim(page
);
1259 stat
->nr_writeback
++;
1260 goto activate_locked
;
1265 wait_on_page_writeback(page
);
1266 /* then go back and try same page again */
1267 list_add_tail(&page
->lru
, page_list
);
1273 references
= page_check_references(page
, sc
);
1275 switch (references
) {
1276 case PAGEREF_ACTIVATE
:
1277 goto activate_locked
;
1279 stat
->nr_ref_keep
+= nr_pages
;
1281 case PAGEREF_RECLAIM
:
1282 case PAGEREF_RECLAIM_CLEAN
:
1283 ; /* try to reclaim the page below */
1287 * Anonymous process memory has backing store?
1288 * Try to allocate it some swap space here.
1289 * Lazyfree page could be freed directly
1291 if (PageAnon(page
) && PageSwapBacked(page
)) {
1292 if (!PageSwapCache(page
)) {
1293 if (!(sc
->gfp_mask
& __GFP_IO
))
1295 if (PageTransHuge(page
)) {
1296 /* cannot split THP, skip it */
1297 if (!can_split_huge_page(page
, NULL
))
1298 goto activate_locked
;
1300 * Split pages without a PMD map right
1301 * away. Chances are some or all of the
1302 * tail pages can be freed without IO.
1304 if (!compound_mapcount(page
) &&
1305 split_huge_page_to_list(page
,
1307 goto activate_locked
;
1309 if (!add_to_swap(page
)) {
1310 if (!PageTransHuge(page
))
1311 goto activate_locked_split
;
1312 /* Fallback to swap normal pages */
1313 if (split_huge_page_to_list(page
,
1315 goto activate_locked
;
1316 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
1317 count_vm_event(THP_SWPOUT_FALLBACK
);
1319 if (!add_to_swap(page
))
1320 goto activate_locked_split
;
1325 /* Adding to swap updated mapping */
1326 mapping
= page_mapping(page
);
1328 } else if (unlikely(PageTransHuge(page
))) {
1329 /* Split file THP */
1330 if (split_huge_page_to_list(page
, page_list
))
1335 * THP may get split above, need minus tail pages and update
1336 * nr_pages to avoid accounting tail pages twice.
1338 * The tail pages that are added into swap cache successfully
1341 if ((nr_pages
> 1) && !PageTransHuge(page
)) {
1342 sc
->nr_scanned
-= (nr_pages
- 1);
1347 * The page is mapped into the page tables of one or more
1348 * processes. Try to unmap it here.
1350 if (page_mapped(page
)) {
1351 enum ttu_flags flags
= ttu_flags
| TTU_BATCH_FLUSH
;
1353 if (unlikely(PageTransHuge(page
)))
1354 flags
|= TTU_SPLIT_HUGE_PMD
;
1355 if (!try_to_unmap(page
, flags
)) {
1356 stat
->nr_unmap_fail
+= nr_pages
;
1357 goto activate_locked
;
1361 if (PageDirty(page
)) {
1363 * Only kswapd can writeback filesystem pages
1364 * to avoid risk of stack overflow. But avoid
1365 * injecting inefficient single-page IO into
1366 * flusher writeback as much as possible: only
1367 * write pages when we've encountered many
1368 * dirty pages, and when we've already scanned
1369 * the rest of the LRU for clean pages and see
1370 * the same dirty pages again (PageReclaim).
1372 if (page_is_file_cache(page
) &&
1373 (!current_is_kswapd() || !PageReclaim(page
) ||
1374 !test_bit(PGDAT_DIRTY
, &pgdat
->flags
))) {
1376 * Immediately reclaim when written back.
1377 * Similar in principal to deactivate_page()
1378 * except we already have the page isolated
1379 * and know it's dirty
1381 inc_node_page_state(page
, NR_VMSCAN_IMMEDIATE
);
1382 SetPageReclaim(page
);
1384 goto activate_locked
;
1387 if (references
== PAGEREF_RECLAIM_CLEAN
)
1391 if (!sc
->may_writepage
)
1395 * Page is dirty. Flush the TLB if a writable entry
1396 * potentially exists to avoid CPU writes after IO
1397 * starts and then write it out here.
1399 try_to_unmap_flush_dirty();
1400 switch (pageout(page
, mapping
, sc
)) {
1404 goto activate_locked
;
1406 if (PageWriteback(page
))
1408 if (PageDirty(page
))
1412 * A synchronous write - probably a ramdisk. Go
1413 * ahead and try to reclaim the page.
1415 if (!trylock_page(page
))
1417 if (PageDirty(page
) || PageWriteback(page
))
1419 mapping
= page_mapping(page
);
1421 ; /* try to free the page below */
1426 * If the page has buffers, try to free the buffer mappings
1427 * associated with this page. If we succeed we try to free
1430 * We do this even if the page is PageDirty().
1431 * try_to_release_page() does not perform I/O, but it is
1432 * possible for a page to have PageDirty set, but it is actually
1433 * clean (all its buffers are clean). This happens if the
1434 * buffers were written out directly, with submit_bh(). ext3
1435 * will do this, as well as the blockdev mapping.
1436 * try_to_release_page() will discover that cleanness and will
1437 * drop the buffers and mark the page clean - it can be freed.
1439 * Rarely, pages can have buffers and no ->mapping. These are
1440 * the pages which were not successfully invalidated in
1441 * truncate_complete_page(). We try to drop those buffers here
1442 * and if that worked, and the page is no longer mapped into
1443 * process address space (page_count == 1) it can be freed.
1444 * Otherwise, leave the page on the LRU so it is swappable.
1446 if (page_has_private(page
)) {
1447 if (!try_to_release_page(page
, sc
->gfp_mask
))
1448 goto activate_locked
;
1449 if (!mapping
&& page_count(page
) == 1) {
1451 if (put_page_testzero(page
))
1455 * rare race with speculative reference.
1456 * the speculative reference will free
1457 * this page shortly, so we may
1458 * increment nr_reclaimed here (and
1459 * leave it off the LRU).
1467 if (PageAnon(page
) && !PageSwapBacked(page
)) {
1468 /* follow __remove_mapping for reference */
1469 if (!page_ref_freeze(page
, 1))
1471 if (PageDirty(page
)) {
1472 page_ref_unfreeze(page
, 1);
1476 count_vm_event(PGLAZYFREED
);
1477 count_memcg_page_event(page
, PGLAZYFREED
);
1478 } else if (!mapping
|| !__remove_mapping(mapping
, page
, true))
1484 * THP may get swapped out in a whole, need account
1487 nr_reclaimed
+= nr_pages
;
1490 * Is there need to periodically free_page_list? It would
1491 * appear not as the counts should be low
1493 if (unlikely(PageTransHuge(page
))) {
1494 mem_cgroup_uncharge(page
);
1495 (*get_compound_page_dtor(page
))(page
);
1497 list_add(&page
->lru
, &free_pages
);
1500 activate_locked_split
:
1502 * The tail pages that are failed to add into swap cache
1503 * reach here. Fixup nr_scanned and nr_pages.
1506 sc
->nr_scanned
-= (nr_pages
- 1);
1510 /* Not a candidate for swapping, so reclaim swap space. */
1511 if (PageSwapCache(page
) && (mem_cgroup_swap_full(page
) ||
1513 try_to_free_swap(page
);
1514 VM_BUG_ON_PAGE(PageActive(page
), page
);
1515 if (!PageMlocked(page
)) {
1516 int type
= page_is_file_cache(page
);
1517 SetPageActive(page
);
1518 stat
->nr_activate
[type
] += nr_pages
;
1519 count_memcg_page_event(page
, PGACTIVATE
);
1524 list_add(&page
->lru
, &ret_pages
);
1525 VM_BUG_ON_PAGE(PageLRU(page
) || PageUnevictable(page
), page
);
1528 pgactivate
= stat
->nr_activate
[0] + stat
->nr_activate
[1];
1530 mem_cgroup_uncharge_list(&free_pages
);
1531 try_to_unmap_flush();
1532 free_unref_page_list(&free_pages
);
1534 list_splice(&ret_pages
, page_list
);
1535 count_vm_events(PGACTIVATE
, pgactivate
);
1537 return nr_reclaimed
;
1540 unsigned long reclaim_clean_pages_from_list(struct zone
*zone
,
1541 struct list_head
*page_list
)
1543 struct scan_control sc
= {
1544 .gfp_mask
= GFP_KERNEL
,
1545 .priority
= DEF_PRIORITY
,
1548 struct reclaim_stat dummy_stat
;
1550 struct page
*page
, *next
;
1551 LIST_HEAD(clean_pages
);
1553 list_for_each_entry_safe(page
, next
, page_list
, lru
) {
1554 if (page_is_file_cache(page
) && !PageDirty(page
) &&
1555 !__PageMovable(page
) && !PageUnevictable(page
)) {
1556 ClearPageActive(page
);
1557 list_move(&page
->lru
, &clean_pages
);
1561 ret
= shrink_page_list(&clean_pages
, zone
->zone_pgdat
, &sc
,
1562 TTU_IGNORE_ACCESS
, &dummy_stat
, true);
1563 list_splice(&clean_pages
, page_list
);
1564 mod_node_page_state(zone
->zone_pgdat
, NR_ISOLATED_FILE
, -ret
);
1569 * Attempt to remove the specified page from its LRU. Only take this page
1570 * if it is of the appropriate PageActive status. Pages which are being
1571 * freed elsewhere are also ignored.
1573 * page: page to consider
1574 * mode: one of the LRU isolation modes defined above
1576 * returns 0 on success, -ve errno on failure.
1578 int __isolate_lru_page(struct page
*page
, isolate_mode_t mode
)
1582 /* Only take pages on the LRU. */
1586 /* Compaction should not handle unevictable pages but CMA can do so */
1587 if (PageUnevictable(page
) && !(mode
& ISOLATE_UNEVICTABLE
))
1593 * To minimise LRU disruption, the caller can indicate that it only
1594 * wants to isolate pages it will be able to operate on without
1595 * blocking - clean pages for the most part.
1597 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
1598 * that it is possible to migrate without blocking
1600 if (mode
& ISOLATE_ASYNC_MIGRATE
) {
1601 /* All the caller can do on PageWriteback is block */
1602 if (PageWriteback(page
))
1605 if (PageDirty(page
)) {
1606 struct address_space
*mapping
;
1610 * Only pages without mappings or that have a
1611 * ->migratepage callback are possible to migrate
1612 * without blocking. However, we can be racing with
1613 * truncation so it's necessary to lock the page
1614 * to stabilise the mapping as truncation holds
1615 * the page lock until after the page is removed
1616 * from the page cache.
1618 if (!trylock_page(page
))
1621 mapping
= page_mapping(page
);
1622 migrate_dirty
= !mapping
|| mapping
->a_ops
->migratepage
;
1629 if ((mode
& ISOLATE_UNMAPPED
) && page_mapped(page
))
1632 if (likely(get_page_unless_zero(page
))) {
1634 * Be careful not to clear PageLRU until after we're
1635 * sure the page is not being freed elsewhere -- the
1636 * page release code relies on it.
1647 * Update LRU sizes after isolating pages. The LRU size updates must
1648 * be complete before mem_cgroup_update_lru_size due to a santity check.
1650 static __always_inline
void update_lru_sizes(struct lruvec
*lruvec
,
1651 enum lru_list lru
, unsigned long *nr_zone_taken
)
1655 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1656 if (!nr_zone_taken
[zid
])
1659 __update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1661 mem_cgroup_update_lru_size(lruvec
, lru
, zid
, -nr_zone_taken
[zid
]);
1668 * pgdat->lru_lock is heavily contended. Some of the functions that
1669 * shrink the lists perform better by taking out a batch of pages
1670 * and working on them outside the LRU lock.
1672 * For pagecache intensive workloads, this function is the hottest
1673 * spot in the kernel (apart from copy_*_user functions).
1675 * Appropriate locks must be held before calling this function.
1677 * @nr_to_scan: The number of eligible pages to look through on the list.
1678 * @lruvec: The LRU vector to pull pages from.
1679 * @dst: The temp list to put pages on to.
1680 * @nr_scanned: The number of pages that were scanned.
1681 * @sc: The scan_control struct for this reclaim session
1682 * @mode: One of the LRU isolation modes
1683 * @lru: LRU list id for isolating
1685 * returns how many pages were moved onto *@dst.
1687 static unsigned long isolate_lru_pages(unsigned long nr_to_scan
,
1688 struct lruvec
*lruvec
, struct list_head
*dst
,
1689 unsigned long *nr_scanned
, struct scan_control
*sc
,
1692 struct list_head
*src
= &lruvec
->lists
[lru
];
1693 unsigned long nr_taken
= 0;
1694 unsigned long nr_zone_taken
[MAX_NR_ZONES
] = { 0 };
1695 unsigned long nr_skipped
[MAX_NR_ZONES
] = { 0, };
1696 unsigned long skipped
= 0;
1697 unsigned long scan
, total_scan
, nr_pages
;
1698 LIST_HEAD(pages_skipped
);
1699 isolate_mode_t mode
= (sc
->may_unmap
? 0 : ISOLATE_UNMAPPED
);
1703 while (scan
< nr_to_scan
&& !list_empty(src
)) {
1706 page
= lru_to_page(src
);
1707 prefetchw_prev_lru_page(page
, src
, flags
);
1709 VM_BUG_ON_PAGE(!PageLRU(page
), page
);
1711 nr_pages
= 1 << compound_order(page
);
1712 total_scan
+= nr_pages
;
1714 if (page_zonenum(page
) > sc
->reclaim_idx
) {
1715 list_move(&page
->lru
, &pages_skipped
);
1716 nr_skipped
[page_zonenum(page
)] += nr_pages
;
1721 * Do not count skipped pages because that makes the function
1722 * return with no isolated pages if the LRU mostly contains
1723 * ineligible pages. This causes the VM to not reclaim any
1724 * pages, triggering a premature OOM.
1726 * Account all tail pages of THP. This would not cause
1727 * premature OOM since __isolate_lru_page() returns -EBUSY
1728 * only when the page is being freed somewhere else.
1731 switch (__isolate_lru_page(page
, mode
)) {
1733 nr_taken
+= nr_pages
;
1734 nr_zone_taken
[page_zonenum(page
)] += nr_pages
;
1735 list_move(&page
->lru
, dst
);
1739 /* else it is being freed elsewhere */
1740 list_move(&page
->lru
, src
);
1749 * Splice any skipped pages to the start of the LRU list. Note that
1750 * this disrupts the LRU order when reclaiming for lower zones but
1751 * we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
1752 * scanning would soon rescan the same pages to skip and put the
1753 * system at risk of premature OOM.
1755 if (!list_empty(&pages_skipped
)) {
1758 list_splice(&pages_skipped
, src
);
1759 for (zid
= 0; zid
< MAX_NR_ZONES
; zid
++) {
1760 if (!nr_skipped
[zid
])
1763 __count_zid_vm_events(PGSCAN_SKIP
, zid
, nr_skipped
[zid
]);
1764 skipped
+= nr_skipped
[zid
];
1767 *nr_scanned
= total_scan
;
1768 trace_mm_vmscan_lru_isolate(sc
->reclaim_idx
, sc
->order
, nr_to_scan
,
1769 total_scan
, skipped
, nr_taken
, mode
, lru
);
1770 update_lru_sizes(lruvec
, lru
, nr_zone_taken
);
1775 * isolate_lru_page - tries to isolate a page from its LRU list
1776 * @page: page to isolate from its LRU list
1778 * Isolates a @page from an LRU list, clears PageLRU and adjusts the
1779 * vmstat statistic corresponding to whatever LRU list the page was on.
1781 * Returns 0 if the page was removed from an LRU list.
1782 * Returns -EBUSY if the page was not on an LRU list.
1784 * The returned page will have PageLRU() cleared. If it was found on
1785 * the active list, it will have PageActive set. If it was found on
1786 * the unevictable list, it will have the PageUnevictable bit set. That flag
1787 * may need to be cleared by the caller before letting the page go.
1789 * The vmstat statistic corresponding to the list on which the page was
1790 * found will be decremented.
1794 * (1) Must be called with an elevated refcount on the page. This is a
1795 * fundamentnal difference from isolate_lru_pages (which is called
1796 * without a stable reference).
1797 * (2) the lru_lock must not be held.
1798 * (3) interrupts must be enabled.
1800 int isolate_lru_page(struct page
*page
)
1804 VM_BUG_ON_PAGE(!page_count(page
), page
);
1805 WARN_RATELIMIT(PageTail(page
), "trying to isolate tail page");
1807 if (PageLRU(page
)) {
1808 pg_data_t
*pgdat
= page_pgdat(page
);
1809 struct lruvec
*lruvec
;
1811 spin_lock_irq(&pgdat
->lru_lock
);
1812 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
1813 if (PageLRU(page
)) {
1814 int lru
= page_lru(page
);
1817 del_page_from_lru_list(page
, lruvec
, lru
);
1820 spin_unlock_irq(&pgdat
->lru_lock
);
1826 * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
1827 * then get resheduled. When there are massive number of tasks doing page
1828 * allocation, such sleeping direct reclaimers may keep piling up on each CPU,
1829 * the LRU list will go small and be scanned faster than necessary, leading to
1830 * unnecessary swapping, thrashing and OOM.
1832 static int too_many_isolated(struct pglist_data
*pgdat
, int file
,
1833 struct scan_control
*sc
)
1835 unsigned long inactive
, isolated
;
1837 if (current_is_kswapd())
1840 if (!sane_reclaim(sc
))
1844 inactive
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
1845 isolated
= node_page_state(pgdat
, NR_ISOLATED_FILE
);
1847 inactive
= node_page_state(pgdat
, NR_INACTIVE_ANON
);
1848 isolated
= node_page_state(pgdat
, NR_ISOLATED_ANON
);
1852 * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
1853 * won't get blocked by normal direct-reclaimers, forming a circular
1856 if ((sc
->gfp_mask
& (__GFP_IO
| __GFP_FS
)) == (__GFP_IO
| __GFP_FS
))
1859 return isolated
> inactive
;
1863 * This moves pages from @list to corresponding LRU list.
1865 * We move them the other way if the page is referenced by one or more
1866 * processes, from rmap.
1868 * If the pages are mostly unmapped, the processing is fast and it is
1869 * appropriate to hold zone_lru_lock across the whole operation. But if
1870 * the pages are mapped, the processing is slow (page_referenced()) so we
1871 * should drop zone_lru_lock around each page. It's impossible to balance
1872 * this, so instead we remove the pages from the LRU while processing them.
1873 * It is safe to rely on PG_active against the non-LRU pages in here because
1874 * nobody will play with that bit on a non-LRU page.
1876 * The downside is that we have to touch page->_refcount against each page.
1877 * But we had to alter page->flags anyway.
1879 * Returns the number of pages moved to the given lruvec.
1882 static unsigned noinline_for_stack
move_pages_to_lru(struct lruvec
*lruvec
,
1883 struct list_head
*list
)
1885 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1886 int nr_pages
, nr_moved
= 0;
1887 LIST_HEAD(pages_to_free
);
1891 while (!list_empty(list
)) {
1892 page
= lru_to_page(list
);
1893 VM_BUG_ON_PAGE(PageLRU(page
), page
);
1894 if (unlikely(!page_evictable(page
))) {
1895 list_del(&page
->lru
);
1896 spin_unlock_irq(&pgdat
->lru_lock
);
1897 putback_lru_page(page
);
1898 spin_lock_irq(&pgdat
->lru_lock
);
1901 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
1904 lru
= page_lru(page
);
1906 nr_pages
= hpage_nr_pages(page
);
1907 update_lru_size(lruvec
, lru
, page_zonenum(page
), nr_pages
);
1908 list_move(&page
->lru
, &lruvec
->lists
[lru
]);
1910 if (put_page_testzero(page
)) {
1911 __ClearPageLRU(page
);
1912 __ClearPageActive(page
);
1913 del_page_from_lru_list(page
, lruvec
, lru
);
1915 if (unlikely(PageCompound(page
))) {
1916 spin_unlock_irq(&pgdat
->lru_lock
);
1917 mem_cgroup_uncharge(page
);
1918 (*get_compound_page_dtor(page
))(page
);
1919 spin_lock_irq(&pgdat
->lru_lock
);
1921 list_add(&page
->lru
, &pages_to_free
);
1923 nr_moved
+= nr_pages
;
1928 * To save our caller's stack, now use input list for pages to free.
1930 list_splice(&pages_to_free
, list
);
1936 * If a kernel thread (such as nfsd for loop-back mounts) services
1937 * a backing device by writing to the page cache it sets PF_LESS_THROTTLE.
1938 * In that case we should only throttle if the backing device it is
1939 * writing to is congested. In other cases it is safe to throttle.
1941 static int current_may_throttle(void)
1943 return !(current
->flags
& PF_LESS_THROTTLE
) ||
1944 current
->backing_dev_info
== NULL
||
1945 bdi_write_congested(current
->backing_dev_info
);
1949 * shrink_inactive_list() is a helper for shrink_node(). It returns the number
1950 * of reclaimed pages
1952 static noinline_for_stack
unsigned long
1953 shrink_inactive_list(unsigned long nr_to_scan
, struct lruvec
*lruvec
,
1954 struct scan_control
*sc
, enum lru_list lru
)
1956 LIST_HEAD(page_list
);
1957 unsigned long nr_scanned
;
1958 unsigned long nr_reclaimed
= 0;
1959 unsigned long nr_taken
;
1960 struct reclaim_stat stat
;
1961 int file
= is_file_lru(lru
);
1962 enum vm_event_item item
;
1963 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
1964 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
1965 bool stalled
= false;
1967 while (unlikely(too_many_isolated(pgdat
, file
, sc
))) {
1971 /* wait a bit for the reclaimer. */
1975 /* We are about to die and free our memory. Return now. */
1976 if (fatal_signal_pending(current
))
1977 return SWAP_CLUSTER_MAX
;
1982 spin_lock_irq(&pgdat
->lru_lock
);
1984 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &page_list
,
1985 &nr_scanned
, sc
, lru
);
1987 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
1988 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
1990 item
= current_is_kswapd() ? PGSCAN_KSWAPD
: PGSCAN_DIRECT
;
1991 if (global_reclaim(sc
))
1992 __count_vm_events(item
, nr_scanned
);
1993 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_scanned
);
1994 spin_unlock_irq(&pgdat
->lru_lock
);
1999 nr_reclaimed
= shrink_page_list(&page_list
, pgdat
, sc
, 0,
2002 spin_lock_irq(&pgdat
->lru_lock
);
2004 item
= current_is_kswapd() ? PGSTEAL_KSWAPD
: PGSTEAL_DIRECT
;
2005 if (global_reclaim(sc
))
2006 __count_vm_events(item
, nr_reclaimed
);
2007 __count_memcg_events(lruvec_memcg(lruvec
), item
, nr_reclaimed
);
2008 reclaim_stat
->recent_rotated
[0] += stat
.nr_activate
[0];
2009 reclaim_stat
->recent_rotated
[1] += stat
.nr_activate
[1];
2011 move_pages_to_lru(lruvec
, &page_list
);
2013 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2015 spin_unlock_irq(&pgdat
->lru_lock
);
2017 mem_cgroup_uncharge_list(&page_list
);
2018 free_unref_page_list(&page_list
);
2021 * If dirty pages are scanned that are not queued for IO, it
2022 * implies that flushers are not doing their job. This can
2023 * happen when memory pressure pushes dirty pages to the end of
2024 * the LRU before the dirty limits are breached and the dirty
2025 * data has expired. It can also happen when the proportion of
2026 * dirty pages grows not through writes but through memory
2027 * pressure reclaiming all the clean cache. And in some cases,
2028 * the flushers simply cannot keep up with the allocation
2029 * rate. Nudge the flusher threads in case they are asleep.
2031 if (stat
.nr_unqueued_dirty
== nr_taken
)
2032 wakeup_flusher_threads(WB_REASON_VMSCAN
);
2034 sc
->nr
.dirty
+= stat
.nr_dirty
;
2035 sc
->nr
.congested
+= stat
.nr_congested
;
2036 sc
->nr
.unqueued_dirty
+= stat
.nr_unqueued_dirty
;
2037 sc
->nr
.writeback
+= stat
.nr_writeback
;
2038 sc
->nr
.immediate
+= stat
.nr_immediate
;
2039 sc
->nr
.taken
+= nr_taken
;
2041 sc
->nr
.file_taken
+= nr_taken
;
2043 trace_mm_vmscan_lru_shrink_inactive(pgdat
->node_id
,
2044 nr_scanned
, nr_reclaimed
, &stat
, sc
->priority
, file
);
2045 return nr_reclaimed
;
2048 static void shrink_active_list(unsigned long nr_to_scan
,
2049 struct lruvec
*lruvec
,
2050 struct scan_control
*sc
,
2053 unsigned long nr_taken
;
2054 unsigned long nr_scanned
;
2055 unsigned long vm_flags
;
2056 LIST_HEAD(l_hold
); /* The pages which were snipped off */
2057 LIST_HEAD(l_active
);
2058 LIST_HEAD(l_inactive
);
2060 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
2061 unsigned nr_deactivate
, nr_activate
;
2062 unsigned nr_rotated
= 0;
2063 int file
= is_file_lru(lru
);
2064 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2068 spin_lock_irq(&pgdat
->lru_lock
);
2070 nr_taken
= isolate_lru_pages(nr_to_scan
, lruvec
, &l_hold
,
2071 &nr_scanned
, sc
, lru
);
2073 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, nr_taken
);
2074 reclaim_stat
->recent_scanned
[file
] += nr_taken
;
2076 __count_vm_events(PGREFILL
, nr_scanned
);
2077 __count_memcg_events(lruvec_memcg(lruvec
), PGREFILL
, nr_scanned
);
2079 spin_unlock_irq(&pgdat
->lru_lock
);
2081 while (!list_empty(&l_hold
)) {
2083 page
= lru_to_page(&l_hold
);
2084 list_del(&page
->lru
);
2086 if (unlikely(!page_evictable(page
))) {
2087 putback_lru_page(page
);
2091 if (unlikely(buffer_heads_over_limit
)) {
2092 if (page_has_private(page
) && trylock_page(page
)) {
2093 if (page_has_private(page
))
2094 try_to_release_page(page
, 0);
2099 if (page_referenced(page
, 0, sc
->target_mem_cgroup
,
2101 nr_rotated
+= hpage_nr_pages(page
);
2103 * Identify referenced, file-backed active pages and
2104 * give them one more trip around the active list. So
2105 * that executable code get better chances to stay in
2106 * memory under moderate memory pressure. Anon pages
2107 * are not likely to be evicted by use-once streaming
2108 * IO, plus JVM can create lots of anon VM_EXEC pages,
2109 * so we ignore them here.
2111 if ((vm_flags
& VM_EXEC
) && page_is_file_cache(page
)) {
2112 list_add(&page
->lru
, &l_active
);
2117 ClearPageActive(page
); /* we are de-activating */
2118 SetPageWorkingset(page
);
2119 list_add(&page
->lru
, &l_inactive
);
2123 * Move pages back to the lru list.
2125 spin_lock_irq(&pgdat
->lru_lock
);
2127 * Count referenced pages from currently used mappings as rotated,
2128 * even though only some of them are actually re-activated. This
2129 * helps balance scan pressure between file and anonymous pages in
2132 reclaim_stat
->recent_rotated
[file
] += nr_rotated
;
2134 nr_activate
= move_pages_to_lru(lruvec
, &l_active
);
2135 nr_deactivate
= move_pages_to_lru(lruvec
, &l_inactive
);
2136 /* Keep all free pages in l_active list */
2137 list_splice(&l_inactive
, &l_active
);
2139 __count_vm_events(PGDEACTIVATE
, nr_deactivate
);
2140 __count_memcg_events(lruvec_memcg(lruvec
), PGDEACTIVATE
, nr_deactivate
);
2142 __mod_node_page_state(pgdat
, NR_ISOLATED_ANON
+ file
, -nr_taken
);
2143 spin_unlock_irq(&pgdat
->lru_lock
);
2145 mem_cgroup_uncharge_list(&l_active
);
2146 free_unref_page_list(&l_active
);
2147 trace_mm_vmscan_lru_shrink_active(pgdat
->node_id
, nr_taken
, nr_activate
,
2148 nr_deactivate
, nr_rotated
, sc
->priority
, file
);
2152 * The inactive anon list should be small enough that the VM never has
2153 * to do too much work.
2155 * The inactive file list should be small enough to leave most memory
2156 * to the established workingset on the scan-resistant active list,
2157 * but large enough to avoid thrashing the aggregate readahead window.
2159 * Both inactive lists should also be large enough that each inactive
2160 * page has a chance to be referenced again before it is reclaimed.
2162 * If that fails and refaulting is observed, the inactive list grows.
2164 * The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
2165 * on this LRU, maintained by the pageout code. An inactive_ratio
2166 * of 3 means 3:1 or 25% of the pages are kept on the inactive list.
2169 * memory ratio inactive
2170 * -------------------------------------
2179 static bool inactive_list_is_low(struct lruvec
*lruvec
, bool file
,
2180 struct scan_control
*sc
, bool trace
)
2182 enum lru_list active_lru
= file
* LRU_FILE
+ LRU_ACTIVE
;
2183 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2184 enum lru_list inactive_lru
= file
* LRU_FILE
;
2185 unsigned long inactive
, active
;
2186 unsigned long inactive_ratio
;
2187 unsigned long refaults
;
2191 * If we don't have swap space, anonymous page deactivation
2194 if (!file
&& !total_swap_pages
)
2197 inactive
= lruvec_lru_size(lruvec
, inactive_lru
, sc
->reclaim_idx
);
2198 active
= lruvec_lru_size(lruvec
, active_lru
, sc
->reclaim_idx
);
2201 * When refaults are being observed, it means a new workingset
2202 * is being established. Disable active list protection to get
2203 * rid of the stale workingset quickly.
2205 refaults
= lruvec_page_state_local(lruvec
, WORKINGSET_ACTIVATE
);
2206 if (file
&& lruvec
->refaults
!= refaults
) {
2209 gb
= (inactive
+ active
) >> (30 - PAGE_SHIFT
);
2211 inactive_ratio
= int_sqrt(10 * gb
);
2217 trace_mm_vmscan_inactive_list_is_low(pgdat
->node_id
, sc
->reclaim_idx
,
2218 lruvec_lru_size(lruvec
, inactive_lru
, MAX_NR_ZONES
), inactive
,
2219 lruvec_lru_size(lruvec
, active_lru
, MAX_NR_ZONES
), active
,
2220 inactive_ratio
, file
);
2222 return inactive
* inactive_ratio
< active
;
2225 static unsigned long shrink_list(enum lru_list lru
, unsigned long nr_to_scan
,
2226 struct lruvec
*lruvec
, struct scan_control
*sc
)
2228 if (is_active_lru(lru
)) {
2229 if (inactive_list_is_low(lruvec
, is_file_lru(lru
), sc
, true))
2230 shrink_active_list(nr_to_scan
, lruvec
, sc
, lru
);
2234 return shrink_inactive_list(nr_to_scan
, lruvec
, sc
, lru
);
2245 * Determine how aggressively the anon and file LRU lists should be
2246 * scanned. The relative value of each set of LRU lists is determined
2247 * by looking at the fraction of the pages scanned we did rotate back
2248 * onto the active list instead of evict.
2250 * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
2251 * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
2253 static void get_scan_count(struct lruvec
*lruvec
, struct mem_cgroup
*memcg
,
2254 struct scan_control
*sc
, unsigned long *nr
,
2255 unsigned long *lru_pages
)
2257 int swappiness
= mem_cgroup_swappiness(memcg
);
2258 struct zone_reclaim_stat
*reclaim_stat
= &lruvec
->reclaim_stat
;
2260 u64 denominator
= 0; /* gcc */
2261 struct pglist_data
*pgdat
= lruvec_pgdat(lruvec
);
2262 unsigned long anon_prio
, file_prio
;
2263 enum scan_balance scan_balance
;
2264 unsigned long anon
, file
;
2265 unsigned long ap
, fp
;
2268 /* If we have no swap space, do not bother scanning anon pages. */
2269 if (!sc
->may_swap
|| mem_cgroup_get_nr_swap_pages(memcg
) <= 0) {
2270 scan_balance
= SCAN_FILE
;
2275 * Global reclaim will swap to prevent OOM even with no
2276 * swappiness, but memcg users want to use this knob to
2277 * disable swapping for individual groups completely when
2278 * using the memory controller's swap limit feature would be
2281 if (!global_reclaim(sc
) && !swappiness
) {
2282 scan_balance
= SCAN_FILE
;
2287 * Do not apply any pressure balancing cleverness when the
2288 * system is close to OOM, scan both anon and file equally
2289 * (unless the swappiness setting disagrees with swapping).
2291 if (!sc
->priority
&& swappiness
) {
2292 scan_balance
= SCAN_EQUAL
;
2297 * Prevent the reclaimer from falling into the cache trap: as
2298 * cache pages start out inactive, every cache fault will tip
2299 * the scan balance towards the file LRU. And as the file LRU
2300 * shrinks, so does the window for rotation from references.
2301 * This means we have a runaway feedback loop where a tiny
2302 * thrashing file LRU becomes infinitely more attractive than
2303 * anon pages. Try to detect this based on file LRU size.
2305 if (global_reclaim(sc
)) {
2306 unsigned long pgdatfile
;
2307 unsigned long pgdatfree
;
2309 unsigned long total_high_wmark
= 0;
2311 pgdatfree
= sum_zone_node_page_state(pgdat
->node_id
, NR_FREE_PAGES
);
2312 pgdatfile
= node_page_state(pgdat
, NR_ACTIVE_FILE
) +
2313 node_page_state(pgdat
, NR_INACTIVE_FILE
);
2315 for (z
= 0; z
< MAX_NR_ZONES
; z
++) {
2316 struct zone
*zone
= &pgdat
->node_zones
[z
];
2317 if (!managed_zone(zone
))
2320 total_high_wmark
+= high_wmark_pages(zone
);
2323 if (unlikely(pgdatfile
+ pgdatfree
<= total_high_wmark
)) {
2325 * Force SCAN_ANON if there are enough inactive
2326 * anonymous pages on the LRU in eligible zones.
2327 * Otherwise, the small LRU gets thrashed.
2329 if (!inactive_list_is_low(lruvec
, false, sc
, false) &&
2330 lruvec_lru_size(lruvec
, LRU_INACTIVE_ANON
, sc
->reclaim_idx
)
2332 scan_balance
= SCAN_ANON
;
2339 * If there is enough inactive page cache, i.e. if the size of the
2340 * inactive list is greater than that of the active list *and* the
2341 * inactive list actually has some pages to scan on this priority, we
2342 * do not reclaim anything from the anonymous working set right now.
2343 * Without the second condition we could end up never scanning an
2344 * lruvec even if it has plenty of old anonymous pages unless the
2345 * system is under heavy pressure.
2347 if (!inactive_list_is_low(lruvec
, true, sc
, false) &&
2348 lruvec_lru_size(lruvec
, LRU_INACTIVE_FILE
, sc
->reclaim_idx
) >> sc
->priority
) {
2349 scan_balance
= SCAN_FILE
;
2353 scan_balance
= SCAN_FRACT
;
2356 * With swappiness at 100, anonymous and file have the same priority.
2357 * This scanning priority is essentially the inverse of IO cost.
2359 anon_prio
= swappiness
;
2360 file_prio
= 200 - anon_prio
;
2363 * OK, so we have swap space and a fair amount of page cache
2364 * pages. We use the recently rotated / recently scanned
2365 * ratios to determine how valuable each cache is.
2367 * Because workloads change over time (and to avoid overflow)
2368 * we keep these statistics as a floating average, which ends
2369 * up weighing recent references more than old ones.
2371 * anon in [0], file in [1]
2374 anon
= lruvec_lru_size(lruvec
, LRU_ACTIVE_ANON
, MAX_NR_ZONES
) +
2375 lruvec_lru_size(lruvec
, LRU_INACTIVE_ANON
, MAX_NR_ZONES
);
2376 file
= lruvec_lru_size(lruvec
, LRU_ACTIVE_FILE
, MAX_NR_ZONES
) +
2377 lruvec_lru_size(lruvec
, LRU_INACTIVE_FILE
, MAX_NR_ZONES
);
2379 spin_lock_irq(&pgdat
->lru_lock
);
2380 if (unlikely(reclaim_stat
->recent_scanned
[0] > anon
/ 4)) {
2381 reclaim_stat
->recent_scanned
[0] /= 2;
2382 reclaim_stat
->recent_rotated
[0] /= 2;
2385 if (unlikely(reclaim_stat
->recent_scanned
[1] > file
/ 4)) {
2386 reclaim_stat
->recent_scanned
[1] /= 2;
2387 reclaim_stat
->recent_rotated
[1] /= 2;
2391 * The amount of pressure on anon vs file pages is inversely
2392 * proportional to the fraction of recently scanned pages on
2393 * each list that were recently referenced and in active use.
2395 ap
= anon_prio
* (reclaim_stat
->recent_scanned
[0] + 1);
2396 ap
/= reclaim_stat
->recent_rotated
[0] + 1;
2398 fp
= file_prio
* (reclaim_stat
->recent_scanned
[1] + 1);
2399 fp
/= reclaim_stat
->recent_rotated
[1] + 1;
2400 spin_unlock_irq(&pgdat
->lru_lock
);
2404 denominator
= ap
+ fp
+ 1;
2407 for_each_evictable_lru(lru
) {
2408 int file
= is_file_lru(lru
);
2412 size
= lruvec_lru_size(lruvec
, lru
, sc
->reclaim_idx
);
2413 scan
= size
>> sc
->priority
;
2415 * If the cgroup's already been deleted, make sure to
2416 * scrape out the remaining cache.
2418 if (!scan
&& !mem_cgroup_online(memcg
))
2419 scan
= min(size
, SWAP_CLUSTER_MAX
);
2421 switch (scan_balance
) {
2423 /* Scan lists relative to size */
2427 * Scan types proportional to swappiness and
2428 * their relative recent reclaim efficiency.
2429 * Make sure we don't miss the last page
2430 * because of a round-off error.
2432 scan
= DIV64_U64_ROUND_UP(scan
* fraction
[file
],
2437 /* Scan one type exclusively */
2438 if ((scan_balance
== SCAN_FILE
) != file
) {
2444 /* Look ma, no brain */
2454 * This is a basic per-node page freer. Used by both kswapd and direct reclaim.
2456 static void shrink_node_memcg(struct pglist_data
*pgdat
, struct mem_cgroup
*memcg
,
2457 struct scan_control
*sc
, unsigned long *lru_pages
)
2459 struct lruvec
*lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
2460 unsigned long nr
[NR_LRU_LISTS
];
2461 unsigned long targets
[NR_LRU_LISTS
];
2462 unsigned long nr_to_scan
;
2464 unsigned long nr_reclaimed
= 0;
2465 unsigned long nr_to_reclaim
= sc
->nr_to_reclaim
;
2466 struct blk_plug plug
;
2469 get_scan_count(lruvec
, memcg
, sc
, nr
, lru_pages
);
2471 /* Record the original scan target for proportional adjustments later */
2472 memcpy(targets
, nr
, sizeof(nr
));
2475 * Global reclaiming within direct reclaim at DEF_PRIORITY is a normal
2476 * event that can occur when there is little memory pressure e.g.
2477 * multiple streaming readers/writers. Hence, we do not abort scanning
2478 * when the requested number of pages are reclaimed when scanning at
2479 * DEF_PRIORITY on the assumption that the fact we are direct
2480 * reclaiming implies that kswapd is not keeping up and it is best to
2481 * do a batch of work at once. For memcg reclaim one check is made to
2482 * abort proportional reclaim if either the file or anon lru has already
2483 * dropped to zero at the first pass.
2485 scan_adjusted
= (global_reclaim(sc
) && !current_is_kswapd() &&
2486 sc
->priority
== DEF_PRIORITY
);
2488 blk_start_plug(&plug
);
2489 while (nr
[LRU_INACTIVE_ANON
] || nr
[LRU_ACTIVE_FILE
] ||
2490 nr
[LRU_INACTIVE_FILE
]) {
2491 unsigned long nr_anon
, nr_file
, percentage
;
2492 unsigned long nr_scanned
;
2494 for_each_evictable_lru(lru
) {
2496 nr_to_scan
= min(nr
[lru
], SWAP_CLUSTER_MAX
);
2497 nr
[lru
] -= nr_to_scan
;
2499 nr_reclaimed
+= shrink_list(lru
, nr_to_scan
,
2506 if (nr_reclaimed
< nr_to_reclaim
|| scan_adjusted
)
2510 * For kswapd and memcg, reclaim at least the number of pages
2511 * requested. Ensure that the anon and file LRUs are scanned
2512 * proportionally what was requested by get_scan_count(). We
2513 * stop reclaiming one LRU and reduce the amount scanning
2514 * proportional to the original scan target.
2516 nr_file
= nr
[LRU_INACTIVE_FILE
] + nr
[LRU_ACTIVE_FILE
];
2517 nr_anon
= nr
[LRU_INACTIVE_ANON
] + nr
[LRU_ACTIVE_ANON
];
2520 * It's just vindictive to attack the larger once the smaller
2521 * has gone to zero. And given the way we stop scanning the
2522 * smaller below, this makes sure that we only make one nudge
2523 * towards proportionality once we've got nr_to_reclaim.
2525 if (!nr_file
|| !nr_anon
)
2528 if (nr_file
> nr_anon
) {
2529 unsigned long scan_target
= targets
[LRU_INACTIVE_ANON
] +
2530 targets
[LRU_ACTIVE_ANON
] + 1;
2532 percentage
= nr_anon
* 100 / scan_target
;
2534 unsigned long scan_target
= targets
[LRU_INACTIVE_FILE
] +
2535 targets
[LRU_ACTIVE_FILE
] + 1;
2537 percentage
= nr_file
* 100 / scan_target
;
2540 /* Stop scanning the smaller of the LRU */
2542 nr
[lru
+ LRU_ACTIVE
] = 0;
2545 * Recalculate the other LRU scan count based on its original
2546 * scan target and the percentage scanning already complete
2548 lru
= (lru
== LRU_FILE
) ? LRU_BASE
: LRU_FILE
;
2549 nr_scanned
= targets
[lru
] - nr
[lru
];
2550 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2551 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2554 nr_scanned
= targets
[lru
] - nr
[lru
];
2555 nr
[lru
] = targets
[lru
] * (100 - percentage
) / 100;
2556 nr
[lru
] -= min(nr
[lru
], nr_scanned
);
2558 scan_adjusted
= true;
2560 blk_finish_plug(&plug
);
2561 sc
->nr_reclaimed
+= nr_reclaimed
;
2564 * Even if we did not try to evict anon pages at all, we want to
2565 * rebalance the anon lru active/inactive ratio.
2567 if (inactive_list_is_low(lruvec
, false, sc
, true))
2568 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
2569 sc
, LRU_ACTIVE_ANON
);
2572 /* Use reclaim/compaction for costly allocs or under memory pressure */
2573 static bool in_reclaim_compaction(struct scan_control
*sc
)
2575 if (IS_ENABLED(CONFIG_COMPACTION
) && sc
->order
&&
2576 (sc
->order
> PAGE_ALLOC_COSTLY_ORDER
||
2577 sc
->priority
< DEF_PRIORITY
- 2))
2584 * Reclaim/compaction is used for high-order allocation requests. It reclaims
2585 * order-0 pages before compacting the zone. should_continue_reclaim() returns
2586 * true if more pages should be reclaimed such that when the page allocator
2587 * calls try_to_compact_zone() that it will have enough free pages to succeed.
2588 * It will give up earlier than that if there is difficulty reclaiming pages.
2590 static inline bool should_continue_reclaim(struct pglist_data
*pgdat
,
2591 unsigned long nr_reclaimed
,
2592 unsigned long nr_scanned
,
2593 struct scan_control
*sc
)
2595 unsigned long pages_for_compaction
;
2596 unsigned long inactive_lru_pages
;
2599 /* If not in reclaim/compaction mode, stop */
2600 if (!in_reclaim_compaction(sc
))
2603 /* Consider stopping depending on scan and reclaim activity */
2604 if (sc
->gfp_mask
& __GFP_RETRY_MAYFAIL
) {
2606 * For __GFP_RETRY_MAYFAIL allocations, stop reclaiming if the
2607 * full LRU list has been scanned and we are still failing
2608 * to reclaim pages. This full LRU scan is potentially
2609 * expensive but a __GFP_RETRY_MAYFAIL caller really wants to succeed
2611 if (!nr_reclaimed
&& !nr_scanned
)
2615 * For non-__GFP_RETRY_MAYFAIL allocations which can presumably
2616 * fail without consequence, stop if we failed to reclaim
2617 * any pages from the last SWAP_CLUSTER_MAX number of
2618 * pages that were scanned. This will return to the
2619 * caller faster at the risk reclaim/compaction and
2620 * the resulting allocation attempt fails
2627 * If we have not reclaimed enough pages for compaction and the
2628 * inactive lists are large enough, continue reclaiming
2630 pages_for_compaction
= compact_gap(sc
->order
);
2631 inactive_lru_pages
= node_page_state(pgdat
, NR_INACTIVE_FILE
);
2632 if (get_nr_swap_pages() > 0)
2633 inactive_lru_pages
+= node_page_state(pgdat
, NR_INACTIVE_ANON
);
2634 if (sc
->nr_reclaimed
< pages_for_compaction
&&
2635 inactive_lru_pages
> pages_for_compaction
)
2638 /* If compaction would go ahead or the allocation would succeed, stop */
2639 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
2640 struct zone
*zone
= &pgdat
->node_zones
[z
];
2641 if (!managed_zone(zone
))
2644 switch (compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
)) {
2645 case COMPACT_SUCCESS
:
2646 case COMPACT_CONTINUE
:
2649 /* check next zone */
2656 static bool pgdat_memcg_congested(pg_data_t
*pgdat
, struct mem_cgroup
*memcg
)
2658 return test_bit(PGDAT_CONGESTED
, &pgdat
->flags
) ||
2659 (memcg
&& memcg_congested(pgdat
, memcg
));
2662 static bool shrink_node(pg_data_t
*pgdat
, struct scan_control
*sc
)
2664 struct reclaim_state
*reclaim_state
= current
->reclaim_state
;
2665 unsigned long nr_reclaimed
, nr_scanned
;
2666 bool reclaimable
= false;
2669 struct mem_cgroup
*root
= sc
->target_mem_cgroup
;
2670 struct mem_cgroup_reclaim_cookie reclaim
= {
2672 .priority
= sc
->priority
,
2674 unsigned long node_lru_pages
= 0;
2675 struct mem_cgroup
*memcg
;
2677 memset(&sc
->nr
, 0, sizeof(sc
->nr
));
2679 nr_reclaimed
= sc
->nr_reclaimed
;
2680 nr_scanned
= sc
->nr_scanned
;
2682 memcg
= mem_cgroup_iter(root
, NULL
, &reclaim
);
2684 unsigned long lru_pages
;
2685 unsigned long reclaimed
;
2686 unsigned long scanned
;
2688 switch (mem_cgroup_protected(root
, memcg
)) {
2689 case MEMCG_PROT_MIN
:
2692 * If there is no reclaimable memory, OOM.
2695 case MEMCG_PROT_LOW
:
2698 * Respect the protection only as long as
2699 * there is an unprotected supply
2700 * of reclaimable memory from other cgroups.
2702 if (!sc
->memcg_low_reclaim
) {
2703 sc
->memcg_low_skipped
= 1;
2706 memcg_memory_event(memcg
, MEMCG_LOW
);
2708 case MEMCG_PROT_NONE
:
2712 reclaimed
= sc
->nr_reclaimed
;
2713 scanned
= sc
->nr_scanned
;
2714 shrink_node_memcg(pgdat
, memcg
, sc
, &lru_pages
);
2715 node_lru_pages
+= lru_pages
;
2717 if (sc
->may_shrinkslab
) {
2718 shrink_slab(sc
->gfp_mask
, pgdat
->node_id
,
2719 memcg
, sc
->priority
);
2722 /* Record the group's reclaim efficiency */
2723 vmpressure(sc
->gfp_mask
, memcg
, false,
2724 sc
->nr_scanned
- scanned
,
2725 sc
->nr_reclaimed
- reclaimed
);
2728 * Kswapd have to scan all memory cgroups to fulfill
2729 * the overall scan target for the node.
2731 * Limit reclaim, on the other hand, only cares about
2732 * nr_to_reclaim pages to be reclaimed and it will
2733 * retry with decreasing priority if one round over the
2734 * whole hierarchy is not sufficient.
2736 if (!current_is_kswapd() &&
2737 sc
->nr_reclaimed
>= sc
->nr_to_reclaim
) {
2738 mem_cgroup_iter_break(root
, memcg
);
2741 } while ((memcg
= mem_cgroup_iter(root
, memcg
, &reclaim
)));
2743 if (reclaim_state
) {
2744 sc
->nr_reclaimed
+= reclaim_state
->reclaimed_slab
;
2745 reclaim_state
->reclaimed_slab
= 0;
2748 /* Record the subtree's reclaim efficiency */
2749 vmpressure(sc
->gfp_mask
, sc
->target_mem_cgroup
, true,
2750 sc
->nr_scanned
- nr_scanned
,
2751 sc
->nr_reclaimed
- nr_reclaimed
);
2753 if (sc
->nr_reclaimed
- nr_reclaimed
)
2756 if (current_is_kswapd()) {
2758 * If reclaim is isolating dirty pages under writeback,
2759 * it implies that the long-lived page allocation rate
2760 * is exceeding the page laundering rate. Either the
2761 * global limits are not being effective at throttling
2762 * processes due to the page distribution throughout
2763 * zones or there is heavy usage of a slow backing
2764 * device. The only option is to throttle from reclaim
2765 * context which is not ideal as there is no guarantee
2766 * the dirtying process is throttled in the same way
2767 * balance_dirty_pages() manages.
2769 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
2770 * count the number of pages under pages flagged for
2771 * immediate reclaim and stall if any are encountered
2772 * in the nr_immediate check below.
2774 if (sc
->nr
.writeback
&& sc
->nr
.writeback
== sc
->nr
.taken
)
2775 set_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
2778 * Tag a node as congested if all the dirty pages
2779 * scanned were backed by a congested BDI and
2780 * wait_iff_congested will stall.
2782 if (sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
2783 set_bit(PGDAT_CONGESTED
, &pgdat
->flags
);
2785 /* Allow kswapd to start writing pages during reclaim.*/
2786 if (sc
->nr
.unqueued_dirty
== sc
->nr
.file_taken
)
2787 set_bit(PGDAT_DIRTY
, &pgdat
->flags
);
2790 * If kswapd scans pages marked marked for immediate
2791 * reclaim and under writeback (nr_immediate), it
2792 * implies that pages are cycling through the LRU
2793 * faster than they are written so also forcibly stall.
2795 if (sc
->nr
.immediate
)
2796 congestion_wait(BLK_RW_ASYNC
, HZ
/10);
2800 * Legacy memcg will stall in page writeback so avoid forcibly
2801 * stalling in wait_iff_congested().
2803 if (!global_reclaim(sc
) && sane_reclaim(sc
) &&
2804 sc
->nr
.dirty
&& sc
->nr
.dirty
== sc
->nr
.congested
)
2805 set_memcg_congestion(pgdat
, root
, true);
2808 * Stall direct reclaim for IO completions if underlying BDIs
2809 * and node is congested. Allow kswapd to continue until it
2810 * starts encountering unqueued dirty pages or cycling through
2811 * the LRU too quickly.
2813 if (!sc
->hibernation_mode
&& !current_is_kswapd() &&
2814 current_may_throttle() && pgdat_memcg_congested(pgdat
, root
))
2815 wait_iff_congested(BLK_RW_ASYNC
, HZ
/10);
2817 } while (should_continue_reclaim(pgdat
, sc
->nr_reclaimed
- nr_reclaimed
,
2818 sc
->nr_scanned
- nr_scanned
, sc
));
2821 * Kswapd gives up on balancing particular nodes after too
2822 * many failures to reclaim anything from them and goes to
2823 * sleep. On reclaim progress, reset the failure counter. A
2824 * successful direct reclaim run will revive a dormant kswapd.
2827 pgdat
->kswapd_failures
= 0;
2833 * Returns true if compaction should go ahead for a costly-order request, or
2834 * the allocation would already succeed without compaction. Return false if we
2835 * should reclaim first.
2837 static inline bool compaction_ready(struct zone
*zone
, struct scan_control
*sc
)
2839 unsigned long watermark
;
2840 enum compact_result suitable
;
2842 suitable
= compaction_suitable(zone
, sc
->order
, 0, sc
->reclaim_idx
);
2843 if (suitable
== COMPACT_SUCCESS
)
2844 /* Allocation should succeed already. Don't reclaim. */
2846 if (suitable
== COMPACT_SKIPPED
)
2847 /* Compaction cannot yet proceed. Do reclaim. */
2851 * Compaction is already possible, but it takes time to run and there
2852 * are potentially other callers using the pages just freed. So proceed
2853 * with reclaim to make a buffer of free pages available to give
2854 * compaction a reasonable chance of completing and allocating the page.
2855 * Note that we won't actually reclaim the whole buffer in one attempt
2856 * as the target watermark in should_continue_reclaim() is lower. But if
2857 * we are already above the high+gap watermark, don't reclaim at all.
2859 watermark
= high_wmark_pages(zone
) + compact_gap(sc
->order
);
2861 return zone_watermark_ok_safe(zone
, 0, watermark
, sc
->reclaim_idx
);
2865 * This is the direct reclaim path, for page-allocating processes. We only
2866 * try to reclaim pages from zones which will satisfy the caller's allocation
2869 * If a zone is deemed to be full of pinned pages then just give it a light
2870 * scan then give up on it.
2872 static void shrink_zones(struct zonelist
*zonelist
, struct scan_control
*sc
)
2876 unsigned long nr_soft_reclaimed
;
2877 unsigned long nr_soft_scanned
;
2879 pg_data_t
*last_pgdat
= NULL
;
2882 * If the number of buffer_heads in the machine exceeds the maximum
2883 * allowed level, force direct reclaim to scan the highmem zone as
2884 * highmem pages could be pinning lowmem pages storing buffer_heads
2886 orig_mask
= sc
->gfp_mask
;
2887 if (buffer_heads_over_limit
) {
2888 sc
->gfp_mask
|= __GFP_HIGHMEM
;
2889 sc
->reclaim_idx
= gfp_zone(sc
->gfp_mask
);
2892 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
2893 sc
->reclaim_idx
, sc
->nodemask
) {
2895 * Take care memory controller reclaiming has small influence
2898 if (global_reclaim(sc
)) {
2899 if (!cpuset_zone_allowed(zone
,
2900 GFP_KERNEL
| __GFP_HARDWALL
))
2904 * If we already have plenty of memory free for
2905 * compaction in this zone, don't free any more.
2906 * Even though compaction is invoked for any
2907 * non-zero order, only frequent costly order
2908 * reclamation is disruptive enough to become a
2909 * noticeable problem, like transparent huge
2912 if (IS_ENABLED(CONFIG_COMPACTION
) &&
2913 sc
->order
> PAGE_ALLOC_COSTLY_ORDER
&&
2914 compaction_ready(zone
, sc
)) {
2915 sc
->compaction_ready
= true;
2920 * Shrink each node in the zonelist once. If the
2921 * zonelist is ordered by zone (not the default) then a
2922 * node may be shrunk multiple times but in that case
2923 * the user prefers lower zones being preserved.
2925 if (zone
->zone_pgdat
== last_pgdat
)
2929 * This steals pages from memory cgroups over softlimit
2930 * and returns the number of reclaimed pages and
2931 * scanned pages. This works for global memory pressure
2932 * and balancing, not for a memcg's limit.
2934 nr_soft_scanned
= 0;
2935 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(zone
->zone_pgdat
,
2936 sc
->order
, sc
->gfp_mask
,
2938 sc
->nr_reclaimed
+= nr_soft_reclaimed
;
2939 sc
->nr_scanned
+= nr_soft_scanned
;
2940 /* need some check for avoid more shrink_zone() */
2943 /* See comment about same check for global reclaim above */
2944 if (zone
->zone_pgdat
== last_pgdat
)
2946 last_pgdat
= zone
->zone_pgdat
;
2947 shrink_node(zone
->zone_pgdat
, sc
);
2951 * Restore to original mask to avoid the impact on the caller if we
2952 * promoted it to __GFP_HIGHMEM.
2954 sc
->gfp_mask
= orig_mask
;
2957 static void snapshot_refaults(struct mem_cgroup
*root_memcg
, pg_data_t
*pgdat
)
2959 struct mem_cgroup
*memcg
;
2961 memcg
= mem_cgroup_iter(root_memcg
, NULL
, NULL
);
2963 unsigned long refaults
;
2964 struct lruvec
*lruvec
;
2966 lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
2967 refaults
= lruvec_page_state_local(lruvec
, WORKINGSET_ACTIVATE
);
2968 lruvec
->refaults
= refaults
;
2969 } while ((memcg
= mem_cgroup_iter(root_memcg
, memcg
, NULL
)));
2973 * This is the main entry point to direct page reclaim.
2975 * If a full scan of the inactive list fails to free enough memory then we
2976 * are "out of memory" and something needs to be killed.
2978 * If the caller is !__GFP_FS then the probability of a failure is reasonably
2979 * high - the zone may be full of dirty or under-writeback pages, which this
2980 * caller can't do much about. We kick the writeback threads and take explicit
2981 * naps in the hope that some of these pages can be written. But if the
2982 * allocating task holds filesystem locks which prevent writeout this might not
2983 * work, and the allocation attempt will fail.
2985 * returns: 0, if no pages reclaimed
2986 * else, the number of pages reclaimed
2988 static unsigned long do_try_to_free_pages(struct zonelist
*zonelist
,
2989 struct scan_control
*sc
)
2991 int initial_priority
= sc
->priority
;
2992 pg_data_t
*last_pgdat
;
2996 delayacct_freepages_start();
2998 if (global_reclaim(sc
))
2999 __count_zid_vm_events(ALLOCSTALL
, sc
->reclaim_idx
, 1);
3002 vmpressure_prio(sc
->gfp_mask
, sc
->target_mem_cgroup
,
3005 shrink_zones(zonelist
, sc
);
3007 if (sc
->nr_reclaimed
>= sc
->nr_to_reclaim
)
3010 if (sc
->compaction_ready
)
3014 * If we're getting trouble reclaiming, start doing
3015 * writepage even in laptop mode.
3017 if (sc
->priority
< DEF_PRIORITY
- 2)
3018 sc
->may_writepage
= 1;
3019 } while (--sc
->priority
>= 0);
3022 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
, sc
->reclaim_idx
,
3024 if (zone
->zone_pgdat
== last_pgdat
)
3026 last_pgdat
= zone
->zone_pgdat
;
3027 snapshot_refaults(sc
->target_mem_cgroup
, zone
->zone_pgdat
);
3028 set_memcg_congestion(last_pgdat
, sc
->target_mem_cgroup
, false);
3031 delayacct_freepages_end();
3033 if (sc
->nr_reclaimed
)
3034 return sc
->nr_reclaimed
;
3036 /* Aborted reclaim to try compaction? don't OOM, then */
3037 if (sc
->compaction_ready
)
3040 /* Untapped cgroup reserves? Don't OOM, retry. */
3041 if (sc
->memcg_low_skipped
) {
3042 sc
->priority
= initial_priority
;
3043 sc
->memcg_low_reclaim
= 1;
3044 sc
->memcg_low_skipped
= 0;
3051 static bool allow_direct_reclaim(pg_data_t
*pgdat
)
3054 unsigned long pfmemalloc_reserve
= 0;
3055 unsigned long free_pages
= 0;
3059 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3062 for (i
= 0; i
<= ZONE_NORMAL
; i
++) {
3063 zone
= &pgdat
->node_zones
[i
];
3064 if (!managed_zone(zone
))
3067 if (!zone_reclaimable_pages(zone
))
3070 pfmemalloc_reserve
+= min_wmark_pages(zone
);
3071 free_pages
+= zone_page_state(zone
, NR_FREE_PAGES
);
3074 /* If there are no reserves (unexpected config) then do not throttle */
3075 if (!pfmemalloc_reserve
)
3078 wmark_ok
= free_pages
> pfmemalloc_reserve
/ 2;
3080 /* kswapd must be awake if processes are being throttled */
3081 if (!wmark_ok
&& waitqueue_active(&pgdat
->kswapd_wait
)) {
3082 pgdat
->kswapd_classzone_idx
= min(pgdat
->kswapd_classzone_idx
,
3083 (enum zone_type
)ZONE_NORMAL
);
3084 wake_up_interruptible(&pgdat
->kswapd_wait
);
3091 * Throttle direct reclaimers if backing storage is backed by the network
3092 * and the PFMEMALLOC reserve for the preferred node is getting dangerously
3093 * depleted. kswapd will continue to make progress and wake the processes
3094 * when the low watermark is reached.
3096 * Returns true if a fatal signal was delivered during throttling. If this
3097 * happens, the page allocator should not consider triggering the OOM killer.
3099 static bool throttle_direct_reclaim(gfp_t gfp_mask
, struct zonelist
*zonelist
,
3100 nodemask_t
*nodemask
)
3104 pg_data_t
*pgdat
= NULL
;
3107 * Kernel threads should not be throttled as they may be indirectly
3108 * responsible for cleaning pages necessary for reclaim to make forward
3109 * progress. kjournald for example may enter direct reclaim while
3110 * committing a transaction where throttling it could forcing other
3111 * processes to block on log_wait_commit().
3113 if (current
->flags
& PF_KTHREAD
)
3117 * If a fatal signal is pending, this process should not throttle.
3118 * It should return quickly so it can exit and free its memory
3120 if (fatal_signal_pending(current
))
3124 * Check if the pfmemalloc reserves are ok by finding the first node
3125 * with a usable ZONE_NORMAL or lower zone. The expectation is that
3126 * GFP_KERNEL will be required for allocating network buffers when
3127 * swapping over the network so ZONE_HIGHMEM is unusable.
3129 * Throttling is based on the first usable node and throttled processes
3130 * wait on a queue until kswapd makes progress and wakes them. There
3131 * is an affinity then between processes waking up and where reclaim
3132 * progress has been made assuming the process wakes on the same node.
3133 * More importantly, processes running on remote nodes will not compete
3134 * for remote pfmemalloc reserves and processes on different nodes
3135 * should make reasonable progress.
3137 for_each_zone_zonelist_nodemask(zone
, z
, zonelist
,
3138 gfp_zone(gfp_mask
), nodemask
) {
3139 if (zone_idx(zone
) > ZONE_NORMAL
)
3142 /* Throttle based on the first usable node */
3143 pgdat
= zone
->zone_pgdat
;
3144 if (allow_direct_reclaim(pgdat
))
3149 /* If no zone was usable by the allocation flags then do not throttle */
3153 /* Account for the throttling */
3154 count_vm_event(PGSCAN_DIRECT_THROTTLE
);
3157 * If the caller cannot enter the filesystem, it's possible that it
3158 * is due to the caller holding an FS lock or performing a journal
3159 * transaction in the case of a filesystem like ext[3|4]. In this case,
3160 * it is not safe to block on pfmemalloc_wait as kswapd could be
3161 * blocked waiting on the same lock. Instead, throttle for up to a
3162 * second before continuing.
3164 if (!(gfp_mask
& __GFP_FS
)) {
3165 wait_event_interruptible_timeout(pgdat
->pfmemalloc_wait
,
3166 allow_direct_reclaim(pgdat
), HZ
);
3171 /* Throttle until kswapd wakes the process */
3172 wait_event_killable(zone
->zone_pgdat
->pfmemalloc_wait
,
3173 allow_direct_reclaim(pgdat
));
3176 if (fatal_signal_pending(current
))
3183 unsigned long try_to_free_pages(struct zonelist
*zonelist
, int order
,
3184 gfp_t gfp_mask
, nodemask_t
*nodemask
)
3186 unsigned long nr_reclaimed
;
3187 struct scan_control sc
= {
3188 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3189 .gfp_mask
= current_gfp_context(gfp_mask
),
3190 .reclaim_idx
= gfp_zone(gfp_mask
),
3192 .nodemask
= nodemask
,
3193 .priority
= DEF_PRIORITY
,
3194 .may_writepage
= !laptop_mode
,
3197 .may_shrinkslab
= 1,
3201 * scan_control uses s8 fields for order, priority, and reclaim_idx.
3202 * Confirm they are large enough for max values.
3204 BUILD_BUG_ON(MAX_ORDER
> S8_MAX
);
3205 BUILD_BUG_ON(DEF_PRIORITY
> S8_MAX
);
3206 BUILD_BUG_ON(MAX_NR_ZONES
> S8_MAX
);
3209 * Do not enter reclaim if fatal signal was delivered while throttled.
3210 * 1 is returned so that the page allocator does not OOM kill at this
3213 if (throttle_direct_reclaim(sc
.gfp_mask
, zonelist
, nodemask
))
3216 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3217 trace_mm_vmscan_direct_reclaim_begin(order
, sc
.gfp_mask
);
3219 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3221 trace_mm_vmscan_direct_reclaim_end(nr_reclaimed
);
3222 set_task_reclaim_state(current
, NULL
);
3224 return nr_reclaimed
;
3229 unsigned long mem_cgroup_shrink_node(struct mem_cgroup
*memcg
,
3230 gfp_t gfp_mask
, bool noswap
,
3232 unsigned long *nr_scanned
)
3234 struct scan_control sc
= {
3235 .nr_to_reclaim
= SWAP_CLUSTER_MAX
,
3236 .target_mem_cgroup
= memcg
,
3237 .may_writepage
= !laptop_mode
,
3239 .reclaim_idx
= MAX_NR_ZONES
- 1,
3240 .may_swap
= !noswap
,
3241 .may_shrinkslab
= 1,
3243 unsigned long lru_pages
;
3245 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3246 sc
.gfp_mask
= (gfp_mask
& GFP_RECLAIM_MASK
) |
3247 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
);
3249 trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc
.order
,
3253 * NOTE: Although we can get the priority field, using it
3254 * here is not a good idea, since it limits the pages we can scan.
3255 * if we don't reclaim here, the shrink_node from balance_pgdat
3256 * will pick up pages from other mem cgroup's as well. We hack
3257 * the priority and make it zero.
3259 shrink_node_memcg(pgdat
, memcg
, &sc
, &lru_pages
);
3261 trace_mm_vmscan_memcg_softlimit_reclaim_end(sc
.nr_reclaimed
);
3263 set_task_reclaim_state(current
, NULL
);
3264 *nr_scanned
= sc
.nr_scanned
;
3266 return sc
.nr_reclaimed
;
3269 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup
*memcg
,
3270 unsigned long nr_pages
,
3274 struct zonelist
*zonelist
;
3275 unsigned long nr_reclaimed
;
3276 unsigned long pflags
;
3278 unsigned int noreclaim_flag
;
3279 struct scan_control sc
= {
3280 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
3281 .gfp_mask
= (current_gfp_context(gfp_mask
) & GFP_RECLAIM_MASK
) |
3282 (GFP_HIGHUSER_MOVABLE
& ~GFP_RECLAIM_MASK
),
3283 .reclaim_idx
= MAX_NR_ZONES
- 1,
3284 .target_mem_cgroup
= memcg
,
3285 .priority
= DEF_PRIORITY
,
3286 .may_writepage
= !laptop_mode
,
3288 .may_swap
= may_swap
,
3289 .may_shrinkslab
= 1,
3292 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3294 * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
3295 * take care of from where we get pages. So the node where we start the
3296 * scan does not need to be the current node.
3298 nid
= mem_cgroup_select_victim_node(memcg
);
3300 zonelist
= &NODE_DATA(nid
)->node_zonelists
[ZONELIST_FALLBACK
];
3302 trace_mm_vmscan_memcg_reclaim_begin(0, sc
.gfp_mask
);
3304 psi_memstall_enter(&pflags
);
3305 noreclaim_flag
= memalloc_noreclaim_save();
3307 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3309 memalloc_noreclaim_restore(noreclaim_flag
);
3310 psi_memstall_leave(&pflags
);
3312 trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed
);
3313 set_task_reclaim_state(current
, NULL
);
3315 return nr_reclaimed
;
3319 static void age_active_anon(struct pglist_data
*pgdat
,
3320 struct scan_control
*sc
)
3322 struct mem_cgroup
*memcg
;
3324 if (!total_swap_pages
)
3327 memcg
= mem_cgroup_iter(NULL
, NULL
, NULL
);
3329 struct lruvec
*lruvec
= mem_cgroup_lruvec(pgdat
, memcg
);
3331 if (inactive_list_is_low(lruvec
, false, sc
, true))
3332 shrink_active_list(SWAP_CLUSTER_MAX
, lruvec
,
3333 sc
, LRU_ACTIVE_ANON
);
3335 memcg
= mem_cgroup_iter(NULL
, memcg
, NULL
);
3339 static bool pgdat_watermark_boosted(pg_data_t
*pgdat
, int classzone_idx
)
3345 * Check for watermark boosts top-down as the higher zones
3346 * are more likely to be boosted. Both watermarks and boosts
3347 * should not be checked at the time time as reclaim would
3348 * start prematurely when there is no boosting and a lower
3351 for (i
= classzone_idx
; i
>= 0; i
--) {
3352 zone
= pgdat
->node_zones
+ i
;
3353 if (!managed_zone(zone
))
3356 if (zone
->watermark_boost
)
3364 * Returns true if there is an eligible zone balanced for the request order
3367 static bool pgdat_balanced(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3370 unsigned long mark
= -1;
3374 * Check watermarks bottom-up as lower zones are more likely to
3377 for (i
= 0; i
<= classzone_idx
; i
++) {
3378 zone
= pgdat
->node_zones
+ i
;
3380 if (!managed_zone(zone
))
3383 mark
= high_wmark_pages(zone
);
3384 if (zone_watermark_ok_safe(zone
, order
, mark
, classzone_idx
))
3389 * If a node has no populated zone within classzone_idx, it does not
3390 * need balancing by definition. This can happen if a zone-restricted
3391 * allocation tries to wake a remote kswapd.
3399 /* Clear pgdat state for congested, dirty or under writeback. */
3400 static void clear_pgdat_congested(pg_data_t
*pgdat
)
3402 clear_bit(PGDAT_CONGESTED
, &pgdat
->flags
);
3403 clear_bit(PGDAT_DIRTY
, &pgdat
->flags
);
3404 clear_bit(PGDAT_WRITEBACK
, &pgdat
->flags
);
3408 * Prepare kswapd for sleeping. This verifies that there are no processes
3409 * waiting in throttle_direct_reclaim() and that watermarks have been met.
3411 * Returns true if kswapd is ready to sleep
3413 static bool prepare_kswapd_sleep(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3416 * The throttled processes are normally woken up in balance_pgdat() as
3417 * soon as allow_direct_reclaim() is true. But there is a potential
3418 * race between when kswapd checks the watermarks and a process gets
3419 * throttled. There is also a potential race if processes get
3420 * throttled, kswapd wakes, a large process exits thereby balancing the
3421 * zones, which causes kswapd to exit balance_pgdat() before reaching
3422 * the wake up checks. If kswapd is going to sleep, no process should
3423 * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
3424 * the wake up is premature, processes will wake kswapd and get
3425 * throttled again. The difference from wake ups in balance_pgdat() is
3426 * that here we are under prepare_to_wait().
3428 if (waitqueue_active(&pgdat
->pfmemalloc_wait
))
3429 wake_up_all(&pgdat
->pfmemalloc_wait
);
3431 /* Hopeless node, leave it to direct reclaim */
3432 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
)
3435 if (pgdat_balanced(pgdat
, order
, classzone_idx
)) {
3436 clear_pgdat_congested(pgdat
);
3444 * kswapd shrinks a node of pages that are at or below the highest usable
3445 * zone that is currently unbalanced.
3447 * Returns true if kswapd scanned at least the requested number of pages to
3448 * reclaim or if the lack of progress was due to pages under writeback.
3449 * This is used to determine if the scanning priority needs to be raised.
3451 static bool kswapd_shrink_node(pg_data_t
*pgdat
,
3452 struct scan_control
*sc
)
3457 /* Reclaim a number of pages proportional to the number of zones */
3458 sc
->nr_to_reclaim
= 0;
3459 for (z
= 0; z
<= sc
->reclaim_idx
; z
++) {
3460 zone
= pgdat
->node_zones
+ z
;
3461 if (!managed_zone(zone
))
3464 sc
->nr_to_reclaim
+= max(high_wmark_pages(zone
), SWAP_CLUSTER_MAX
);
3468 * Historically care was taken to put equal pressure on all zones but
3469 * now pressure is applied based on node LRU order.
3471 shrink_node(pgdat
, sc
);
3474 * Fragmentation may mean that the system cannot be rebalanced for
3475 * high-order allocations. If twice the allocation size has been
3476 * reclaimed then recheck watermarks only at order-0 to prevent
3477 * excessive reclaim. Assume that a process requested a high-order
3478 * can direct reclaim/compact.
3480 if (sc
->order
&& sc
->nr_reclaimed
>= compact_gap(sc
->order
))
3483 return sc
->nr_scanned
>= sc
->nr_to_reclaim
;
3487 * For kswapd, balance_pgdat() will reclaim pages across a node from zones
3488 * that are eligible for use by the caller until at least one zone is
3491 * Returns the order kswapd finished reclaiming at.
3493 * kswapd scans the zones in the highmem->normal->dma direction. It skips
3494 * zones which have free_pages > high_wmark_pages(zone), but once a zone is
3495 * found to have free_pages <= high_wmark_pages(zone), any page in that zone
3496 * or lower is eligible for reclaim until at least one usable zone is
3499 static int balance_pgdat(pg_data_t
*pgdat
, int order
, int classzone_idx
)
3502 unsigned long nr_soft_reclaimed
;
3503 unsigned long nr_soft_scanned
;
3504 unsigned long pflags
;
3505 unsigned long nr_boost_reclaim
;
3506 unsigned long zone_boosts
[MAX_NR_ZONES
] = { 0, };
3509 struct scan_control sc
= {
3510 .gfp_mask
= GFP_KERNEL
,
3515 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3516 psi_memstall_enter(&pflags
);
3517 __fs_reclaim_acquire();
3519 count_vm_event(PAGEOUTRUN
);
3522 * Account for the reclaim boost. Note that the zone boost is left in
3523 * place so that parallel allocations that are near the watermark will
3524 * stall or direct reclaim until kswapd is finished.
3526 nr_boost_reclaim
= 0;
3527 for (i
= 0; i
<= classzone_idx
; i
++) {
3528 zone
= pgdat
->node_zones
+ i
;
3529 if (!managed_zone(zone
))
3532 nr_boost_reclaim
+= zone
->watermark_boost
;
3533 zone_boosts
[i
] = zone
->watermark_boost
;
3535 boosted
= nr_boost_reclaim
;
3538 sc
.priority
= DEF_PRIORITY
;
3540 unsigned long nr_reclaimed
= sc
.nr_reclaimed
;
3541 bool raise_priority
= true;
3545 sc
.reclaim_idx
= classzone_idx
;
3548 * If the number of buffer_heads exceeds the maximum allowed
3549 * then consider reclaiming from all zones. This has a dual
3550 * purpose -- on 64-bit systems it is expected that
3551 * buffer_heads are stripped during active rotation. On 32-bit
3552 * systems, highmem pages can pin lowmem memory and shrinking
3553 * buffers can relieve lowmem pressure. Reclaim may still not
3554 * go ahead if all eligible zones for the original allocation
3555 * request are balanced to avoid excessive reclaim from kswapd.
3557 if (buffer_heads_over_limit
) {
3558 for (i
= MAX_NR_ZONES
- 1; i
>= 0; i
--) {
3559 zone
= pgdat
->node_zones
+ i
;
3560 if (!managed_zone(zone
))
3569 * If the pgdat is imbalanced then ignore boosting and preserve
3570 * the watermarks for a later time and restart. Note that the
3571 * zone watermarks will be still reset at the end of balancing
3572 * on the grounds that the normal reclaim should be enough to
3573 * re-evaluate if boosting is required when kswapd next wakes.
3575 balanced
= pgdat_balanced(pgdat
, sc
.order
, classzone_idx
);
3576 if (!balanced
&& nr_boost_reclaim
) {
3577 nr_boost_reclaim
= 0;
3582 * If boosting is not active then only reclaim if there are no
3583 * eligible zones. Note that sc.reclaim_idx is not used as
3584 * buffer_heads_over_limit may have adjusted it.
3586 if (!nr_boost_reclaim
&& balanced
)
3589 /* Limit the priority of boosting to avoid reclaim writeback */
3590 if (nr_boost_reclaim
&& sc
.priority
== DEF_PRIORITY
- 2)
3591 raise_priority
= false;
3594 * Do not writeback or swap pages for boosted reclaim. The
3595 * intent is to relieve pressure not issue sub-optimal IO
3596 * from reclaim context. If no pages are reclaimed, the
3597 * reclaim will be aborted.
3599 sc
.may_writepage
= !laptop_mode
&& !nr_boost_reclaim
;
3600 sc
.may_swap
= !nr_boost_reclaim
;
3601 sc
.may_shrinkslab
= !nr_boost_reclaim
;
3604 * Do some background aging of the anon list, to give
3605 * pages a chance to be referenced before reclaiming. All
3606 * pages are rotated regardless of classzone as this is
3607 * about consistent aging.
3609 age_active_anon(pgdat
, &sc
);
3612 * If we're getting trouble reclaiming, start doing writepage
3613 * even in laptop mode.
3615 if (sc
.priority
< DEF_PRIORITY
- 2)
3616 sc
.may_writepage
= 1;
3618 /* Call soft limit reclaim before calling shrink_node. */
3620 nr_soft_scanned
= 0;
3621 nr_soft_reclaimed
= mem_cgroup_soft_limit_reclaim(pgdat
, sc
.order
,
3622 sc
.gfp_mask
, &nr_soft_scanned
);
3623 sc
.nr_reclaimed
+= nr_soft_reclaimed
;
3626 * There should be no need to raise the scanning priority if
3627 * enough pages are already being scanned that that high
3628 * watermark would be met at 100% efficiency.
3630 if (kswapd_shrink_node(pgdat
, &sc
))
3631 raise_priority
= false;
3634 * If the low watermark is met there is no need for processes
3635 * to be throttled on pfmemalloc_wait as they should not be
3636 * able to safely make forward progress. Wake them
3638 if (waitqueue_active(&pgdat
->pfmemalloc_wait
) &&
3639 allow_direct_reclaim(pgdat
))
3640 wake_up_all(&pgdat
->pfmemalloc_wait
);
3642 /* Check if kswapd should be suspending */
3643 __fs_reclaim_release();
3644 ret
= try_to_freeze();
3645 __fs_reclaim_acquire();
3646 if (ret
|| kthread_should_stop())
3650 * Raise priority if scanning rate is too low or there was no
3651 * progress in reclaiming pages
3653 nr_reclaimed
= sc
.nr_reclaimed
- nr_reclaimed
;
3654 nr_boost_reclaim
-= min(nr_boost_reclaim
, nr_reclaimed
);
3657 * If reclaim made no progress for a boost, stop reclaim as
3658 * IO cannot be queued and it could be an infinite loop in
3659 * extreme circumstances.
3661 if (nr_boost_reclaim
&& !nr_reclaimed
)
3664 if (raise_priority
|| !nr_reclaimed
)
3666 } while (sc
.priority
>= 1);
3668 if (!sc
.nr_reclaimed
)
3669 pgdat
->kswapd_failures
++;
3672 /* If reclaim was boosted, account for the reclaim done in this pass */
3674 unsigned long flags
;
3676 for (i
= 0; i
<= classzone_idx
; i
++) {
3677 if (!zone_boosts
[i
])
3680 /* Increments are under the zone lock */
3681 zone
= pgdat
->node_zones
+ i
;
3682 spin_lock_irqsave(&zone
->lock
, flags
);
3683 zone
->watermark_boost
-= min(zone
->watermark_boost
, zone_boosts
[i
]);
3684 spin_unlock_irqrestore(&zone
->lock
, flags
);
3688 * As there is now likely space, wakeup kcompact to defragment
3691 wakeup_kcompactd(pgdat
, pageblock_order
, classzone_idx
);
3694 snapshot_refaults(NULL
, pgdat
);
3695 __fs_reclaim_release();
3696 psi_memstall_leave(&pflags
);
3697 set_task_reclaim_state(current
, NULL
);
3700 * Return the order kswapd stopped reclaiming at as
3701 * prepare_kswapd_sleep() takes it into account. If another caller
3702 * entered the allocator slow path while kswapd was awake, order will
3703 * remain at the higher level.
3709 * The pgdat->kswapd_classzone_idx is used to pass the highest zone index to be
3710 * reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is not
3711 * a valid index then either kswapd runs for first time or kswapd couldn't sleep
3712 * after previous reclaim attempt (node is still unbalanced). In that case
3713 * return the zone index of the previous kswapd reclaim cycle.
3715 static enum zone_type
kswapd_classzone_idx(pg_data_t
*pgdat
,
3716 enum zone_type prev_classzone_idx
)
3718 if (pgdat
->kswapd_classzone_idx
== MAX_NR_ZONES
)
3719 return prev_classzone_idx
;
3720 return pgdat
->kswapd_classzone_idx
;
3723 static void kswapd_try_to_sleep(pg_data_t
*pgdat
, int alloc_order
, int reclaim_order
,
3724 unsigned int classzone_idx
)
3729 if (freezing(current
) || kthread_should_stop())
3732 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3735 * Try to sleep for a short interval. Note that kcompactd will only be
3736 * woken if it is possible to sleep for a short interval. This is
3737 * deliberate on the assumption that if reclaim cannot keep an
3738 * eligible zone balanced that it's also unlikely that compaction will
3741 if (prepare_kswapd_sleep(pgdat
, reclaim_order
, classzone_idx
)) {
3743 * Compaction records what page blocks it recently failed to
3744 * isolate pages from and skips them in the future scanning.
3745 * When kswapd is going to sleep, it is reasonable to assume
3746 * that pages and compaction may succeed so reset the cache.
3748 reset_isolation_suitable(pgdat
);
3751 * We have freed the memory, now we should compact it to make
3752 * allocation of the requested order possible.
3754 wakeup_kcompactd(pgdat
, alloc_order
, classzone_idx
);
3756 remaining
= schedule_timeout(HZ
/10);
3759 * If woken prematurely then reset kswapd_classzone_idx and
3760 * order. The values will either be from a wakeup request or
3761 * the previous request that slept prematurely.
3764 pgdat
->kswapd_classzone_idx
= kswapd_classzone_idx(pgdat
, classzone_idx
);
3765 pgdat
->kswapd_order
= max(pgdat
->kswapd_order
, reclaim_order
);
3768 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3769 prepare_to_wait(&pgdat
->kswapd_wait
, &wait
, TASK_INTERRUPTIBLE
);
3773 * After a short sleep, check if it was a premature sleep. If not, then
3774 * go fully to sleep until explicitly woken up.
3777 prepare_kswapd_sleep(pgdat
, reclaim_order
, classzone_idx
)) {
3778 trace_mm_vmscan_kswapd_sleep(pgdat
->node_id
);
3781 * vmstat counters are not perfectly accurate and the estimated
3782 * value for counters such as NR_FREE_PAGES can deviate from the
3783 * true value by nr_online_cpus * threshold. To avoid the zone
3784 * watermarks being breached while under pressure, we reduce the
3785 * per-cpu vmstat threshold while kswapd is awake and restore
3786 * them before going back to sleep.
3788 set_pgdat_percpu_threshold(pgdat
, calculate_normal_threshold
);
3790 if (!kthread_should_stop())
3793 set_pgdat_percpu_threshold(pgdat
, calculate_pressure_threshold
);
3796 count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY
);
3798 count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY
);
3800 finish_wait(&pgdat
->kswapd_wait
, &wait
);
3804 * The background pageout daemon, started as a kernel thread
3805 * from the init process.
3807 * This basically trickles out pages so that we have _some_
3808 * free memory available even if there is no other activity
3809 * that frees anything up. This is needed for things like routing
3810 * etc, where we otherwise might have all activity going on in
3811 * asynchronous contexts that cannot page things out.
3813 * If there are applications that are active memory-allocators
3814 * (most normal use), this basically shouldn't matter.
3816 static int kswapd(void *p
)
3818 unsigned int alloc_order
, reclaim_order
;
3819 unsigned int classzone_idx
= MAX_NR_ZONES
- 1;
3820 pg_data_t
*pgdat
= (pg_data_t
*)p
;
3821 struct task_struct
*tsk
= current
;
3822 const struct cpumask
*cpumask
= cpumask_of_node(pgdat
->node_id
);
3824 if (!cpumask_empty(cpumask
))
3825 set_cpus_allowed_ptr(tsk
, cpumask
);
3828 * Tell the memory management that we're a "memory allocator",
3829 * and that if we need more memory we should get access to it
3830 * regardless (see "__alloc_pages()"). "kswapd" should
3831 * never get caught in the normal page freeing logic.
3833 * (Kswapd normally doesn't need memory anyway, but sometimes
3834 * you need a small amount of memory in order to be able to
3835 * page out something else, and this flag essentially protects
3836 * us from recursively trying to free more memory as we're
3837 * trying to free the first piece of memory in the first place).
3839 tsk
->flags
|= PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
;
3842 pgdat
->kswapd_order
= 0;
3843 pgdat
->kswapd_classzone_idx
= MAX_NR_ZONES
;
3847 alloc_order
= reclaim_order
= pgdat
->kswapd_order
;
3848 classzone_idx
= kswapd_classzone_idx(pgdat
, classzone_idx
);
3851 kswapd_try_to_sleep(pgdat
, alloc_order
, reclaim_order
,
3854 /* Read the new order and classzone_idx */
3855 alloc_order
= reclaim_order
= pgdat
->kswapd_order
;
3856 classzone_idx
= kswapd_classzone_idx(pgdat
, classzone_idx
);
3857 pgdat
->kswapd_order
= 0;
3858 pgdat
->kswapd_classzone_idx
= MAX_NR_ZONES
;
3860 ret
= try_to_freeze();
3861 if (kthread_should_stop())
3865 * We can speed up thawing tasks if we don't call balance_pgdat
3866 * after returning from the refrigerator
3872 * Reclaim begins at the requested order but if a high-order
3873 * reclaim fails then kswapd falls back to reclaiming for
3874 * order-0. If that happens, kswapd will consider sleeping
3875 * for the order it finished reclaiming at (reclaim_order)
3876 * but kcompactd is woken to compact for the original
3877 * request (alloc_order).
3879 trace_mm_vmscan_kswapd_wake(pgdat
->node_id
, classzone_idx
,
3881 reclaim_order
= balance_pgdat(pgdat
, alloc_order
, classzone_idx
);
3882 if (reclaim_order
< alloc_order
)
3883 goto kswapd_try_sleep
;
3886 tsk
->flags
&= ~(PF_MEMALLOC
| PF_SWAPWRITE
| PF_KSWAPD
);
3892 * A zone is low on free memory or too fragmented for high-order memory. If
3893 * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
3894 * pgdat. It will wake up kcompactd after reclaiming memory. If kswapd reclaim
3895 * has failed or is not needed, still wake up kcompactd if only compaction is
3898 void wakeup_kswapd(struct zone
*zone
, gfp_t gfp_flags
, int order
,
3899 enum zone_type classzone_idx
)
3903 if (!managed_zone(zone
))
3906 if (!cpuset_zone_allowed(zone
, gfp_flags
))
3908 pgdat
= zone
->zone_pgdat
;
3910 if (pgdat
->kswapd_classzone_idx
== MAX_NR_ZONES
)
3911 pgdat
->kswapd_classzone_idx
= classzone_idx
;
3913 pgdat
->kswapd_classzone_idx
= max(pgdat
->kswapd_classzone_idx
,
3915 pgdat
->kswapd_order
= max(pgdat
->kswapd_order
, order
);
3916 if (!waitqueue_active(&pgdat
->kswapd_wait
))
3919 /* Hopeless node, leave it to direct reclaim if possible */
3920 if (pgdat
->kswapd_failures
>= MAX_RECLAIM_RETRIES
||
3921 (pgdat_balanced(pgdat
, order
, classzone_idx
) &&
3922 !pgdat_watermark_boosted(pgdat
, classzone_idx
))) {
3924 * There may be plenty of free memory available, but it's too
3925 * fragmented for high-order allocations. Wake up kcompactd
3926 * and rely on compaction_suitable() to determine if it's
3927 * needed. If it fails, it will defer subsequent attempts to
3928 * ratelimit its work.
3930 if (!(gfp_flags
& __GFP_DIRECT_RECLAIM
))
3931 wakeup_kcompactd(pgdat
, order
, classzone_idx
);
3935 trace_mm_vmscan_wakeup_kswapd(pgdat
->node_id
, classzone_idx
, order
,
3937 wake_up_interruptible(&pgdat
->kswapd_wait
);
3940 #ifdef CONFIG_HIBERNATION
3942 * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
3945 * Rather than trying to age LRUs the aim is to preserve the overall
3946 * LRU order by reclaiming preferentially
3947 * inactive > active > active referenced > active mapped
3949 unsigned long shrink_all_memory(unsigned long nr_to_reclaim
)
3951 struct scan_control sc
= {
3952 .nr_to_reclaim
= nr_to_reclaim
,
3953 .gfp_mask
= GFP_HIGHUSER_MOVABLE
,
3954 .reclaim_idx
= MAX_NR_ZONES
- 1,
3955 .priority
= DEF_PRIORITY
,
3959 .hibernation_mode
= 1,
3961 struct zonelist
*zonelist
= node_zonelist(numa_node_id(), sc
.gfp_mask
);
3962 unsigned long nr_reclaimed
;
3963 unsigned int noreclaim_flag
;
3965 fs_reclaim_acquire(sc
.gfp_mask
);
3966 noreclaim_flag
= memalloc_noreclaim_save();
3967 set_task_reclaim_state(current
, &sc
.reclaim_state
);
3969 nr_reclaimed
= do_try_to_free_pages(zonelist
, &sc
);
3971 set_task_reclaim_state(current
, NULL
);
3972 memalloc_noreclaim_restore(noreclaim_flag
);
3973 fs_reclaim_release(sc
.gfp_mask
);
3975 return nr_reclaimed
;
3977 #endif /* CONFIG_HIBERNATION */
3979 /* It's optimal to keep kswapds on the same CPUs as their memory, but
3980 not required for correctness. So if the last cpu in a node goes
3981 away, we get changed to run anywhere: as the first one comes back,
3982 restore their cpu bindings. */
3983 static int kswapd_cpu_online(unsigned int cpu
)
3987 for_each_node_state(nid
, N_MEMORY
) {
3988 pg_data_t
*pgdat
= NODE_DATA(nid
);
3989 const struct cpumask
*mask
;
3991 mask
= cpumask_of_node(pgdat
->node_id
);
3993 if (cpumask_any_and(cpu_online_mask
, mask
) < nr_cpu_ids
)
3994 /* One of our CPUs online: restore mask */
3995 set_cpus_allowed_ptr(pgdat
->kswapd
, mask
);
4001 * This kswapd start function will be called by init and node-hot-add.
4002 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
4004 int kswapd_run(int nid
)
4006 pg_data_t
*pgdat
= NODE_DATA(nid
);
4012 pgdat
->kswapd
= kthread_run(kswapd
, pgdat
, "kswapd%d", nid
);
4013 if (IS_ERR(pgdat
->kswapd
)) {
4014 /* failure at boot is fatal */
4015 BUG_ON(system_state
< SYSTEM_RUNNING
);
4016 pr_err("Failed to start kswapd on node %d\n", nid
);
4017 ret
= PTR_ERR(pgdat
->kswapd
);
4018 pgdat
->kswapd
= NULL
;
4024 * Called by memory hotplug when all memory in a node is offlined. Caller must
4025 * hold mem_hotplug_begin/end().
4027 void kswapd_stop(int nid
)
4029 struct task_struct
*kswapd
= NODE_DATA(nid
)->kswapd
;
4032 kthread_stop(kswapd
);
4033 NODE_DATA(nid
)->kswapd
= NULL
;
4037 static int __init
kswapd_init(void)
4042 for_each_node_state(nid
, N_MEMORY
)
4044 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
,
4045 "mm/vmscan:online", kswapd_cpu_online
,
4051 module_init(kswapd_init
)
4057 * If non-zero call node_reclaim when the number of free pages falls below
4060 int node_reclaim_mode __read_mostly
;
4062 #define RECLAIM_OFF 0
4063 #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
4064 #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
4065 #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */
4068 * Priority for NODE_RECLAIM. This determines the fraction of pages
4069 * of a node considered for each zone_reclaim. 4 scans 1/16th of
4072 #define NODE_RECLAIM_PRIORITY 4
4075 * Percentage of pages in a zone that must be unmapped for node_reclaim to
4078 int sysctl_min_unmapped_ratio
= 1;
4081 * If the number of slab pages in a zone grows beyond this percentage then
4082 * slab reclaim needs to occur.
4084 int sysctl_min_slab_ratio
= 5;
4086 static inline unsigned long node_unmapped_file_pages(struct pglist_data
*pgdat
)
4088 unsigned long file_mapped
= node_page_state(pgdat
, NR_FILE_MAPPED
);
4089 unsigned long file_lru
= node_page_state(pgdat
, NR_INACTIVE_FILE
) +
4090 node_page_state(pgdat
, NR_ACTIVE_FILE
);
4093 * It's possible for there to be more file mapped pages than
4094 * accounted for by the pages on the file LRU lists because
4095 * tmpfs pages accounted for as ANON can also be FILE_MAPPED
4097 return (file_lru
> file_mapped
) ? (file_lru
- file_mapped
) : 0;
4100 /* Work out how many page cache pages we can reclaim in this reclaim_mode */
4101 static unsigned long node_pagecache_reclaimable(struct pglist_data
*pgdat
)
4103 unsigned long nr_pagecache_reclaimable
;
4104 unsigned long delta
= 0;
4107 * If RECLAIM_UNMAP is set, then all file pages are considered
4108 * potentially reclaimable. Otherwise, we have to worry about
4109 * pages like swapcache and node_unmapped_file_pages() provides
4112 if (node_reclaim_mode
& RECLAIM_UNMAP
)
4113 nr_pagecache_reclaimable
= node_page_state(pgdat
, NR_FILE_PAGES
);
4115 nr_pagecache_reclaimable
= node_unmapped_file_pages(pgdat
);
4117 /* If we can't clean pages, remove dirty pages from consideration */
4118 if (!(node_reclaim_mode
& RECLAIM_WRITE
))
4119 delta
+= node_page_state(pgdat
, NR_FILE_DIRTY
);
4121 /* Watch for any possible underflows due to delta */
4122 if (unlikely(delta
> nr_pagecache_reclaimable
))
4123 delta
= nr_pagecache_reclaimable
;
4125 return nr_pagecache_reclaimable
- delta
;
4129 * Try to free up some pages from this node through reclaim.
4131 static int __node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4133 /* Minimum pages needed in order to stay on node */
4134 const unsigned long nr_pages
= 1 << order
;
4135 struct task_struct
*p
= current
;
4136 unsigned int noreclaim_flag
;
4137 struct scan_control sc
= {
4138 .nr_to_reclaim
= max(nr_pages
, SWAP_CLUSTER_MAX
),
4139 .gfp_mask
= current_gfp_context(gfp_mask
),
4141 .priority
= NODE_RECLAIM_PRIORITY
,
4142 .may_writepage
= !!(node_reclaim_mode
& RECLAIM_WRITE
),
4143 .may_unmap
= !!(node_reclaim_mode
& RECLAIM_UNMAP
),
4145 .reclaim_idx
= gfp_zone(gfp_mask
),
4148 trace_mm_vmscan_node_reclaim_begin(pgdat
->node_id
, order
,
4152 fs_reclaim_acquire(sc
.gfp_mask
);
4154 * We need to be able to allocate from the reserves for RECLAIM_UNMAP
4155 * and we also need to be able to write out pages for RECLAIM_WRITE
4156 * and RECLAIM_UNMAP.
4158 noreclaim_flag
= memalloc_noreclaim_save();
4159 p
->flags
|= PF_SWAPWRITE
;
4160 set_task_reclaim_state(p
, &sc
.reclaim_state
);
4162 if (node_pagecache_reclaimable(pgdat
) > pgdat
->min_unmapped_pages
) {
4164 * Free memory by calling shrink node with increasing
4165 * priorities until we have enough memory freed.
4168 shrink_node(pgdat
, &sc
);
4169 } while (sc
.nr_reclaimed
< nr_pages
&& --sc
.priority
>= 0);
4172 set_task_reclaim_state(p
, NULL
);
4173 current
->flags
&= ~PF_SWAPWRITE
;
4174 memalloc_noreclaim_restore(noreclaim_flag
);
4175 fs_reclaim_release(sc
.gfp_mask
);
4177 trace_mm_vmscan_node_reclaim_end(sc
.nr_reclaimed
);
4179 return sc
.nr_reclaimed
>= nr_pages
;
4182 int node_reclaim(struct pglist_data
*pgdat
, gfp_t gfp_mask
, unsigned int order
)
4187 * Node reclaim reclaims unmapped file backed pages and
4188 * slab pages if we are over the defined limits.
4190 * A small portion of unmapped file backed pages is needed for
4191 * file I/O otherwise pages read by file I/O will be immediately
4192 * thrown out if the node is overallocated. So we do not reclaim
4193 * if less than a specified percentage of the node is used by
4194 * unmapped file backed pages.
4196 if (node_pagecache_reclaimable(pgdat
) <= pgdat
->min_unmapped_pages
&&
4197 node_page_state(pgdat
, NR_SLAB_RECLAIMABLE
) <= pgdat
->min_slab_pages
)
4198 return NODE_RECLAIM_FULL
;
4201 * Do not scan if the allocation should not be delayed.
4203 if (!gfpflags_allow_blocking(gfp_mask
) || (current
->flags
& PF_MEMALLOC
))
4204 return NODE_RECLAIM_NOSCAN
;
4207 * Only run node reclaim on the local node or on nodes that do not
4208 * have associated processors. This will favor the local processor
4209 * over remote processors and spread off node memory allocations
4210 * as wide as possible.
4212 if (node_state(pgdat
->node_id
, N_CPU
) && pgdat
->node_id
!= numa_node_id())
4213 return NODE_RECLAIM_NOSCAN
;
4215 if (test_and_set_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
))
4216 return NODE_RECLAIM_NOSCAN
;
4218 ret
= __node_reclaim(pgdat
, gfp_mask
, order
);
4219 clear_bit(PGDAT_RECLAIM_LOCKED
, &pgdat
->flags
);
4222 count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED
);
4229 * page_evictable - test whether a page is evictable
4230 * @page: the page to test
4232 * Test whether page is evictable--i.e., should be placed on active/inactive
4233 * lists vs unevictable list.
4235 * Reasons page might not be evictable:
4236 * (1) page's mapping marked unevictable
4237 * (2) page is part of an mlocked VMA
4240 int page_evictable(struct page
*page
)
4244 /* Prevent address_space of inode and swap cache from being freed */
4246 ret
= !mapping_unevictable(page_mapping(page
)) && !PageMlocked(page
);
4252 * check_move_unevictable_pages - check pages for evictability and move to
4253 * appropriate zone lru list
4254 * @pvec: pagevec with lru pages to check
4256 * Checks pages for evictability, if an evictable page is in the unevictable
4257 * lru list, moves it to the appropriate evictable lru list. This function
4258 * should be only used for lru pages.
4260 void check_move_unevictable_pages(struct pagevec
*pvec
)
4262 struct lruvec
*lruvec
;
4263 struct pglist_data
*pgdat
= NULL
;
4268 for (i
= 0; i
< pvec
->nr
; i
++) {
4269 struct page
*page
= pvec
->pages
[i
];
4270 struct pglist_data
*pagepgdat
= page_pgdat(page
);
4273 if (pagepgdat
!= pgdat
) {
4275 spin_unlock_irq(&pgdat
->lru_lock
);
4277 spin_lock_irq(&pgdat
->lru_lock
);
4279 lruvec
= mem_cgroup_page_lruvec(page
, pgdat
);
4281 if (!PageLRU(page
) || !PageUnevictable(page
))
4284 if (page_evictable(page
)) {
4285 enum lru_list lru
= page_lru_base_type(page
);
4287 VM_BUG_ON_PAGE(PageActive(page
), page
);
4288 ClearPageUnevictable(page
);
4289 del_page_from_lru_list(page
, lruvec
, LRU_UNEVICTABLE
);
4290 add_page_to_lru_list(page
, lruvec
, lru
);
4296 __count_vm_events(UNEVICTABLE_PGRESCUED
, pgrescued
);
4297 __count_vm_events(UNEVICTABLE_PGSCANNED
, pgscanned
);
4298 spin_unlock_irq(&pgdat
->lru_lock
);
4301 EXPORT_SYMBOL_GPL(check_move_unevictable_pages
);