blob: 43ddaabef2f7146055f1c18c1587dc2878229bef [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*
* Swap reorganised 29.12.95, Stephen Tweedie.
* kswapd added: 7.1.96 sct
* Removed kswapd_ctl limits, and swap out as many pages as needed
* to bring the system back to freepages.high: 2.4.97, Rik van Riel.
* Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
* Multiqueue VM started 5.8.00, Rik van Riel.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/vmpressure.h>
#include <linux/vmstat.h>
#include <linux/file.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h> /* for try_to_release_page(),
buffer_heads_over_limit */
#include <linux/mm_inline.h>
#include <linux/backing-dev.h>
#include <linux/rmap.h>
#include <linux/topology.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/compaction.h>
#include <linux/notifier.h>
#include <linux/rwsem.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/memcontrol.h>
#include <linux/migrate.h>
#include <linux/delayacct.h>
#include <linux/sysctl.h>
#include <linux/oom.h>
#include <linux/pagevec.h>
#include <linux/prefetch.h>
#include <linux/printk.h>
#include <linux/dax.h>
#include <linux/psi.h>
#include <linux/pagewalk.h>
#include <linux/shmem_fs.h>
#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
#include <linux/swapops.h>
#include <linux/balloon_compaction.h>
#include "internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/vmscan.h>
#undef CREATE_TRACE_POINTS
#include <trace/hooks/vmscan.h>
struct scan_control {
/* How many pages shrink_list() should reclaim */
unsigned long nr_to_reclaim;
/*
* Nodemask of nodes allowed by the caller. If NULL, all nodes
* are scanned.
*/
nodemask_t *nodemask;
/*
* The memory cgroup that hit its limit and as a result is the
* primary target of this reclaim invocation.
*/
struct mem_cgroup *target_mem_cgroup;
/*
* Scan pressure balancing between anon and file LRUs
*/
unsigned long anon_cost;
unsigned long file_cost;
/* Can active pages be deactivated as part of reclaim? */
#define DEACTIVATE_ANON 1
#define DEACTIVATE_FILE 2
unsigned int may_deactivate:2;
unsigned int force_deactivate:1;
unsigned int skipped_deactivate:1;
/* Writepage batching in laptop mode; RECLAIM_WRITE */
unsigned int may_writepage:1;
/* Can mapped pages be reclaimed? */
unsigned int may_unmap:1;
/* Can pages be swapped as part of reclaim? */
unsigned int may_swap:1;
/*
* Cgroup memory below memory.low is protected as long as we
* don't threaten to OOM. If any cgroup is reclaimed at
* reduced force or passed over entirely due to its memory.low
* setting (memcg_low_skipped), and nothing is reclaimed as a
* result, then go back for one more cycle that reclaims the protected
* memory (memcg_low_reclaim) to avert OOM.
*/
unsigned int memcg_low_reclaim:1;
unsigned int memcg_low_skipped:1;
unsigned int hibernation_mode:1;
/* One of the zones is ready for compaction */
unsigned int compaction_ready:1;
/* There is easily reclaimable cold cache in the current node */
unsigned int cache_trim_mode:1;
/* The file pages on the current node are dangerously low */
unsigned int file_is_tiny:1;
/* Always discard instead of demoting to lower tier memory */
unsigned int no_demotion:1;
#ifdef CONFIG_LRU_GEN
/* help make better choices when multiple memcgs are available */
unsigned int memcgs_need_aging:1;
unsigned int memcgs_need_swapping:1;
unsigned int memcgs_avoid_swapping:1;
#endif
/* Allocation order */
s8 order;
/* Scan (total_size >> priority) pages at once */
s8 priority;
/* The highest zone to isolate pages for reclaim from */
s8 reclaim_idx;
/* This context's GFP mask */
gfp_t gfp_mask;
/* Incremented by the number of inactive pages that were scanned */
unsigned long nr_scanned;
/* Number of pages freed so far during a call to shrink_zones() */
unsigned long nr_reclaimed;
struct {
unsigned int dirty;
unsigned int unqueued_dirty;
unsigned int congested;
unsigned int writeback;
unsigned int immediate;
unsigned int file_taken;
unsigned int taken;
} nr;
/* for recording the reclaimed slab by now */
struct reclaim_state reclaim_state;
};
#ifdef ARCH_HAS_PREFETCHW
#define prefetchw_prev_lru_page(_page, _base, _field) \
do { \
if ((_page)->lru.prev != _base) { \
struct page *prev; \
\
prev = lru_to_page(&(_page->lru)); \
prefetchw(&prev->_field); \
} \
} while (0)
#else
#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
#endif
/*
* From 0 .. 200. Higher means more swappy.
*/
int vm_swappiness = 60;
static void set_task_reclaim_state(struct task_struct *task,
struct reclaim_state *rs)
{
/* Check for an overwrite */
WARN_ON_ONCE(rs && task->reclaim_state);
/* Check for the nulling of an already-nulled member */
WARN_ON_ONCE(!rs && !task->reclaim_state);
task->reclaim_state = rs;
}
static LIST_HEAD(shrinker_list);
static DECLARE_RWSEM(shrinker_rwsem);
#ifdef CONFIG_MEMCG
static int shrinker_nr_max;
/* The shrinker_info is expanded in a batch of BITS_PER_LONG */
static inline int shrinker_map_size(int nr_items)
{
return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long));
}
static inline int shrinker_defer_size(int nr_items)
{
return (round_up(nr_items, BITS_PER_LONG) * sizeof(atomic_long_t));
}
static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
int nid)
{
return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
lockdep_is_held(&shrinker_rwsem));
}
static int expand_one_shrinker_info(struct mem_cgroup *memcg,
int map_size, int defer_size,
int old_map_size, int old_defer_size)
{
struct shrinker_info *new, *old;
struct mem_cgroup_per_node *pn;
int nid;
int size = map_size + defer_size;
for_each_node(nid) {
pn = memcg->nodeinfo[nid];
old = shrinker_info_protected(memcg, nid);
/* Not yet online memcg */
if (!old)
return 0;
new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
if (!new)
return -ENOMEM;
new->nr_deferred = (atomic_long_t *)(new + 1);
new->map = (void *)new->nr_deferred + defer_size;
/* map: set all old bits, clear all new bits */
memset(new->map, (int)0xff, old_map_size);
memset((void *)new->map + old_map_size, 0, map_size - old_map_size);
/* nr_deferred: copy old values, clear all new values */
memcpy(new->nr_deferred, old->nr_deferred, old_defer_size);
memset((void *)new->nr_deferred + old_defer_size, 0,
defer_size - old_defer_size);
rcu_assign_pointer(pn->shrinker_info, new);
kvfree_rcu(old, rcu);
}
return 0;
}
void free_shrinker_info(struct mem_cgroup *memcg)
{
struct mem_cgroup_per_node *pn;
struct shrinker_info *info;
int nid;
for_each_node(nid) {
pn = memcg->nodeinfo[nid];
info = rcu_dereference_protected(pn->shrinker_info, true);
kvfree(info);
rcu_assign_pointer(pn->shrinker_info, NULL);
}
}
int alloc_shrinker_info(struct mem_cgroup *memcg)
{
struct shrinker_info *info;
int nid, size, ret = 0;
int map_size, defer_size = 0;
down_write(&shrinker_rwsem);
map_size = shrinker_map_size(shrinker_nr_max);
defer_size = shrinker_defer_size(shrinker_nr_max);
size = map_size + defer_size;
for_each_node(nid) {
info = kvzalloc_node(sizeof(*info) + size, GFP_KERNEL, nid);
if (!info) {
free_shrinker_info(memcg);
ret = -ENOMEM;
break;
}
info->nr_deferred = (atomic_long_t *)(info + 1);
info->map = (void *)info->nr_deferred + defer_size;
rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
}
up_write(&shrinker_rwsem);
return ret;
}
static inline bool need_expand(int nr_max)
{
return round_up(nr_max, BITS_PER_LONG) >
round_up(shrinker_nr_max, BITS_PER_LONG);
}
static int expand_shrinker_info(int new_id)
{
int ret = 0;
int new_nr_max = new_id + 1;
int map_size, defer_size = 0;
int old_map_size, old_defer_size = 0;
struct mem_cgroup *memcg;
if (!need_expand(new_nr_max))
goto out;
if (!root_mem_cgroup)
goto out;
lockdep_assert_held(&shrinker_rwsem);
map_size = shrinker_map_size(new_nr_max);
defer_size = shrinker_defer_size(new_nr_max);
old_map_size = shrinker_map_size(shrinker_nr_max);
old_defer_size = shrinker_defer_size(shrinker_nr_max);
memcg = mem_cgroup_iter(NULL, NULL, NULL);
do {
ret = expand_one_shrinker_info(memcg, map_size, defer_size,
old_map_size, old_defer_size);
if (ret) {
mem_cgroup_iter_break(NULL, memcg);
goto out;
}
} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
out:
if (!ret)
shrinker_nr_max = new_nr_max;
return ret;
}
void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
{
if (shrinker_id >= 0 && memcg && !mem_cgroup_is_root(memcg)) {
struct shrinker_info *info;
rcu_read_lock();
info = rcu_dereference(memcg->nodeinfo[nid]->shrinker_info);
/* Pairs with smp mb in shrink_slab() */
smp_mb__before_atomic();
set_bit(shrinker_id, info->map);
rcu_read_unlock();
}
}
static DEFINE_IDR(shrinker_idr);
static int prealloc_memcg_shrinker(struct shrinker *shrinker)
{
int id, ret = -ENOMEM;
if (mem_cgroup_disabled())
return -ENOSYS;
down_write(&shrinker_rwsem);
/* This may call shrinker, so it must use down_read_trylock() */
id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
if (id < 0)
goto unlock;
if (id >= shrinker_nr_max) {
if (expand_shrinker_info(id)) {
idr_remove(&shrinker_idr, id);
goto unlock;
}
}
shrinker->id = id;
ret = 0;
unlock:
up_write(&shrinker_rwsem);
return ret;
}
static void unregister_memcg_shrinker(struct shrinker *shrinker)
{
int id = shrinker->id;
BUG_ON(id < 0);
lockdep_assert_held(&shrinker_rwsem);
idr_remove(&shrinker_idr, id);
}
static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
struct mem_cgroup *memcg)
{
struct shrinker_info *info;
info = shrinker_info_protected(memcg, nid);
return atomic_long_xchg(&info->nr_deferred[shrinker->id], 0);
}
static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
struct mem_cgroup *memcg)
{
struct shrinker_info *info;
info = shrinker_info_protected(memcg, nid);
return atomic_long_add_return(nr, &info->nr_deferred[shrinker->id]);
}
void reparent_shrinker_deferred(struct mem_cgroup *memcg)
{
int i, nid;
long nr;
struct mem_cgroup *parent;
struct shrinker_info *child_info, *parent_info;
parent = parent_mem_cgroup(memcg);
if (!parent)
parent = root_mem_cgroup;
/* Prevent from concurrent shrinker_info expand */
down_read(&shrinker_rwsem);
for_each_node(nid) {
child_info = shrinker_info_protected(memcg, nid);
parent_info = shrinker_info_protected(parent, nid);
for (i = 0; i < shrinker_nr_max; i++) {
nr = atomic_long_read(&child_info->nr_deferred[i]);
atomic_long_add(nr, &parent_info->nr_deferred[i]);
}
}
up_read(&shrinker_rwsem);
}
static bool cgroup_reclaim(struct scan_control *sc)
{
return sc->target_mem_cgroup;
}
/**
* writeback_throttling_sane - is the usual dirty throttling mechanism available?
* @sc: scan_control in question
*
* The normal page dirty throttling mechanism in balance_dirty_pages() is
* completely broken with the legacy memcg and direct stalling in
* shrink_page_list() is used for throttling instead, which lacks all the
* niceties such as fairness, adaptive pausing, bandwidth proportional
* allocation and configurability.
*
* This function tests whether the vmscan currently in progress can assume
* that the normal dirty throttling mechanism is operational.
*/
static bool writeback_throttling_sane(struct scan_control *sc)
{
if (!cgroup_reclaim(sc))
return true;
#ifdef CONFIG_CGROUP_WRITEBACK
if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
return true;
#endif
return false;
}
#else
static int prealloc_memcg_shrinker(struct shrinker *shrinker)
{
return -ENOSYS;
}
static void unregister_memcg_shrinker(struct shrinker *shrinker)
{
}
static long xchg_nr_deferred_memcg(int nid, struct shrinker *shrinker,
struct mem_cgroup *memcg)
{
return 0;
}
static long add_nr_deferred_memcg(long nr, int nid, struct shrinker *shrinker,
struct mem_cgroup *memcg)
{
return 0;
}
static bool cgroup_reclaim(struct scan_control *sc)
{
return false;
}
static bool writeback_throttling_sane(struct scan_control *sc)
{
return true;
}
#endif
static long xchg_nr_deferred(struct shrinker *shrinker,
struct shrink_control *sc)
{
int nid = sc->nid;
if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
nid = 0;
if (sc->memcg &&
(shrinker->flags & SHRINKER_MEMCG_AWARE))
return xchg_nr_deferred_memcg(nid, shrinker,
sc->memcg);
return atomic_long_xchg(&shrinker->nr_deferred[nid], 0);
}
static long add_nr_deferred(long nr, struct shrinker *shrinker,
struct shrink_control *sc)
{
int nid = sc->nid;
if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
nid = 0;
if (sc->memcg &&
(shrinker->flags & SHRINKER_MEMCG_AWARE))
return add_nr_deferred_memcg(nr, nid, shrinker,
sc->memcg);
return atomic_long_add_return(nr, &shrinker->nr_deferred[nid]);
}
static bool can_demote(int nid, struct scan_control *sc)
{
if (!numa_demotion_enabled)
return false;
if (sc) {
if (sc->no_demotion)
return false;
/* It is pointless to do demotion in memcg reclaim */
if (cgroup_reclaim(sc))
return false;
}
if (next_demotion_node(nid) == NUMA_NO_NODE)
return false;
return true;
}
static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,
int nid,
struct scan_control *sc)
{
if (memcg == NULL) {
/*
* For non-memcg reclaim, is there
* space in any swap device?
*/
if (get_nr_swap_pages() > 0)
return true;
} else {
/* Is the memcg below its swap limit? */
if (mem_cgroup_get_nr_swap_pages(memcg) > 0)
return true;
}
/*
* The page can not be swapped.
*
* Can it be reclaimed from this node via demotion?
*/
return can_demote(nid, sc);
}
/*
* This misses isolated pages which are not accounted for to save counters.
* As the data only determines if reclaim or compaction continues, it is
* not expected that isolated pages will be a dominating factor.
*/
unsigned long zone_reclaimable_pages(struct zone *zone)
{
unsigned long nr;
nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
if (can_reclaim_anon_pages(NULL, zone_to_nid(zone), NULL))
nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
return nr;
}
/**
* lruvec_lru_size - Returns the number of pages on the given LRU list.
* @lruvec: lru vector
* @lru: lru to use
* @zone_idx: zones to consider (use MAX_NR_ZONES for the whole LRU list)
*/
static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
int zone_idx)
{
unsigned long size = 0;
int zid;
for (zid = 0; zid <= zone_idx && zid < MAX_NR_ZONES; zid++) {
struct zone *zone = &lruvec_pgdat(lruvec)->node_zones[zid];
if (!managed_zone(zone))
continue;
if (!mem_cgroup_disabled())
size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
else
size += zone_page_state(zone, NR_ZONE_LRU_BASE + lru);
}
return size;
}
/*
* Add a shrinker callback to be called from the vm.
*/
int prealloc_shrinker(struct shrinker *shrinker)
{
unsigned int size;
int err;
if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
err = prealloc_memcg_shrinker(shrinker);
if (err != -ENOSYS)
return err;
shrinker->flags &= ~SHRINKER_MEMCG_AWARE;
}
size = sizeof(*shrinker->nr_deferred);
if (shrinker->flags & SHRINKER_NUMA_AWARE)
size *= nr_node_ids;
shrinker->nr_deferred = kzalloc(size, GFP_KERNEL);
if (!shrinker->nr_deferred)
return -ENOMEM;
return 0;
}
void free_prealloced_shrinker(struct shrinker *shrinker)
{
if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
down_write(&shrinker_rwsem);
unregister_memcg_shrinker(shrinker);
up_write(&shrinker_rwsem);
return;
}
kfree(shrinker->nr_deferred);
shrinker->nr_deferred = NULL;
}
void register_shrinker_prepared(struct shrinker *shrinker)
{
down_write(&shrinker_rwsem);
list_add_tail(&shrinker->list, &shrinker_list);
shrinker->flags |= SHRINKER_REGISTERED;
up_write(&shrinker_rwsem);
}
int register_shrinker(struct shrinker *shrinker)
{
int err = prealloc_shrinker(shrinker);
if (err)
return err;
register_shrinker_prepared(shrinker);
return 0;
}
EXPORT_SYMBOL(register_shrinker);
/*
* Remove one
*/
void unregister_shrinker(struct shrinker *shrinker)
{
if (!(shrinker->flags & SHRINKER_REGISTERED))
return;
down_write(&shrinker_rwsem);
list_del(&shrinker->list);
shrinker->flags &= ~SHRINKER_REGISTERED;
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
unregister_memcg_shrinker(shrinker);
up_write(&shrinker_rwsem);
kfree(shrinker->nr_deferred);
shrinker->nr_deferred = NULL;
}
EXPORT_SYMBOL(unregister_shrinker);
#define SHRINK_BATCH 128
static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
struct shrinker *shrinker, int priority)
{
unsigned long freed = 0;
unsigned long long delta;
long total_scan;
long freeable;
long nr;
long new_nr;
long batch_size = shrinker->batch ? shrinker->batch
: SHRINK_BATCH;
long scanned = 0, next_deferred;
trace_android_vh_do_shrink_slab(shrinker, shrinkctl, priority);
freeable = shrinker->count_objects(shrinker, shrinkctl);
if (freeable == 0 || freeable == SHRINK_EMPTY)
return freeable;
/*
* copy the current shrinker scan count into a local variable
* and zero it so that other concurrent shrinker invocations
* don't also do this scanning work.
*/
nr = xchg_nr_deferred(shrinker, shrinkctl);
if (shrinker->seeks) {
delta = freeable >> priority;
delta *= 4;
do_div(delta, shrinker->seeks);
} else {
/*
* These objects don't require any IO to create. Trim
* them aggressively under memory pressure to keep
* them from causing refetches in the IO caches.
*/
delta = freeable / 2;
}
total_scan = nr >> priority;
total_scan += delta;
total_scan = min(total_scan, (2 * freeable));
trace_mm_shrink_slab_start(shrinker, shrinkctl, nr,
freeable, delta, total_scan, priority);
/*
* Normally, we should not scan less than batch_size objects in one
* pass to avoid too frequent shrinker calls, but if the slab has less
* than batch_size objects in total and we are really tight on memory,
* we will try to reclaim all available objects, otherwise we can end
* up failing allocations although there are plenty of reclaimable
* objects spread over several slabs with usage less than the
* batch_size.
*
* We detect the "tight on memory" situations by looking at the total
* number of objects we want to scan (total_scan). If it is greater
* than the total number of objects on slab (freeable), we must be
* scanning at high prio and therefore should try to reclaim as much as
* possible.
*/
while (total_scan >= batch_size ||
total_scan >= freeable) {
unsigned long ret;
unsigned long nr_to_scan = min(batch_size, total_scan);
shrinkctl->nr_to_scan = nr_to_scan;
shrinkctl->nr_scanned = nr_to_scan;
ret = shrinker->scan_objects(shrinker, shrinkctl);
if (ret == SHRINK_STOP)
break;
freed += ret;
count_vm_events(SLABS_SCANNED, shrinkctl->nr_scanned);
total_scan -= shrinkctl->nr_scanned;
scanned += shrinkctl->nr_scanned;
cond_resched();
}
/*
* The deferred work is increased by any new work (delta) that wasn't
* done, decreased by old deferred work that was done now.
*
* And it is capped to two times of the freeable items.
*/
next_deferred = max_t(long, (nr + delta - scanned), 0);
next_deferred = min(next_deferred, (2 * freeable));
/*
* move the unused scan count back into the shrinker in a
* manner that handles concurrent updates.
*/
new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
return freed;
}
#ifdef CONFIG_MEMCG
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
struct mem_cgroup *memcg, int priority)
{
struct shrinker_info *info;
unsigned long ret, freed = 0;
int i;
if (!mem_cgroup_online(memcg))
return 0;
if (!down_read_trylock(&shrinker_rwsem))
return 0;
info = shrinker_info_protected(memcg, nid);
if (unlikely(!info))
goto unlock;
for_each_set_bit(i, info->map, shrinker_nr_max) {
struct shrink_control sc = {
.gfp_mask = gfp_mask,
.nid = nid,
.memcg = memcg,
};
struct shrinker *shrinker;
shrinker = idr_find(&shrinker_idr, i);
if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
if (!shrinker)
clear_bit(i, info->map);
continue;
}
/* Call non-slab shrinkers even though kmem is disabled */
if (!memcg_kmem_enabled() &&
!(shrinker->flags & SHRINKER_NONSLAB))
continue;
ret = do_shrink_slab(&sc, shrinker, priority);
if (ret == SHRINK_EMPTY) {
clear_bit(i, info->map);
/*
* After the shrinker reported that it had no objects to
* free, but before we cleared the corresponding bit in
* the memcg shrinker map, a new object might have been
* added. To make sure, we have the bit set in this
* case, we invoke the shrinker one more time and reset
* the bit if it reports that it is not empty anymore.
* The memory barrier here pairs with the barrier in
* set_shrinker_bit():
*
* list_lru_add() shrink_slab_memcg()
* list_add_tail() clear_bit()
* <MB> <MB>
* set_bit() do_shrink_slab()
*/
smp_mb__after_atomic();
ret = do_shrink_slab(&sc, shrinker, priority);
if (ret == SHRINK_EMPTY)
ret = 0;
else
set_shrinker_bit(memcg, nid, i);
}
freed += ret;
if (rwsem_is_contended(&shrinker_rwsem)) {
freed = freed ? : 1;
break;
}
}
unlock:
up_read(&shrinker_rwsem);
return freed;
}
#else /* CONFIG_MEMCG */
static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
struct mem_cgroup *memcg, int priority)
{
return 0;
}
#endif /* CONFIG_MEMCG */
/**
* shrink_slab - shrink slab caches
* @gfp_mask: allocation context
* @nid: node whose slab caches to target
* @memcg: memory cgroup whose slab caches to target
* @priority: the reclaim priority
*
* Call the shrink functions to age shrinkable caches.
*
* @nid is passed along to shrinkers with SHRINKER_NUMA_AWARE set,
* unaware shrinkers will receive a node id of 0 instead.
*
* @memcg specifies the memory cgroup to target. Unaware shrinkers
* are called only if it is the root cgroup.
*
* @priority is sc->priority, we take the number of objects and >> by priority
* in order to get the scan target.
*
* Returns the number of reclaimed slab objects.
*/
unsigned long shrink_slab(gfp_t gfp_mask, int nid,
struct mem_cgroup *memcg,
int priority)
{
unsigned long ret, freed = 0;
struct shrinker *shrinker;
bool bypass = false;
trace_android_vh_shrink_slab_bypass(gfp_mask, nid, memcg, priority, &bypass);
if (bypass)
return 0;
/*
* The root memcg might be allocated even though memcg is disabled
* via "cgroup_disable=memory" boot parameter. This could make
* mem_cgroup_is_root() return false, then just run memcg slab
* shrink, but skip global shrink. This may result in premature
* oom.
*/
if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
if (!down_read_trylock(&shrinker_rwsem))
goto out;
list_for_each_entry(shrinker, &shrinker_list, list) {
struct shrink_control sc = {
.gfp_mask = gfp_mask,
.nid = nid,
.memcg = memcg,
};
ret = do_shrink_slab(&sc, shrinker, priority);
if (ret == SHRINK_EMPTY)
ret = 0;
freed += ret;
/*
* Bail out if someone want to register a new shrinker to
* prevent the registration from being stalled for long periods
* by parallel ongoing shrinking.
*/
if (rwsem_is_contended(&shrinker_rwsem)) {
freed = freed ? : 1;
break;
}
}
up_read(&shrinker_rwsem);
out:
cond_resched();
return freed;
}
EXPORT_SYMBOL_GPL(shrink_slab);
void drop_slab_node(int nid)
{
unsigned long freed;
int shift = 0;
do {
struct mem_cgroup *memcg = NULL;
if (fatal_signal_pending(current))
return;
freed = 0;
memcg = mem_cgroup_iter(NULL, NULL, NULL);
do {
freed += shrink_slab(GFP_KERNEL, nid, memcg, 0);
} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
} while ((freed >> shift++) > 1);
}
void drop_slab(void)
{
int nid;
for_each_online_node(nid)
drop_slab_node(nid);
}
static inline int is_page_cache_freeable(struct page *page)
{
/*
* A freeable page cache page is referenced only by the caller
* that isolated the page, the page cache and optional buffer
* heads at page->private.
*/
int page_cache_pins = thp_nr_pages(page);
return page_count(page) - page_has_private(page) == 1 + page_cache_pins;
}
static int may_write_to_inode(struct inode *inode)
{
if (current->flags & PF_SWAPWRITE)
return 1;
if (!inode_write_congested(inode))
return 1;
if (inode_to_bdi(inode) == current->backing_dev_info)
return 1;
return 0;
}
/*
* We detected a synchronous write error writing a page out. Probably
* -ENOSPC. We need to propagate that into the address_space for a subsequent
* fsync(), msync() or close().
*
* The tricky part is that after writepage we cannot touch the mapping: nothing
* prevents it from being freed up. But we have a ref on the page and once
* that page is locked, the mapping is pinned.
*
* We're allowed to run sleeping lock_page() here because we know the caller has
* __GFP_FS.
*/
static void handle_write_error(struct address_space *mapping,
struct page *page, int error)
{
lock_page(page);
if (page_mapping(page) == mapping)
mapping_set_error(mapping, error);
unlock_page(page);
}
/* possible outcome of pageout() */
typedef enum {
/* failed to write page out, page is locked */
PAGE_KEEP,
/* move page to the active list, page is locked */
PAGE_ACTIVATE,
/* page has been sent to the disk successfully, page is unlocked */
PAGE_SUCCESS,
/* page is clean and locked */
PAGE_CLEAN,
} pageout_t;
/*
* pageout is called by shrink_page_list() for each dirty page.
* Calls ->writepage().
*/
static pageout_t pageout(struct page *page, struct address_space *mapping)
{
/*
* If the page is dirty, only perform writeback if that write
* will be non-blocking. To prevent this allocation from being
* stalled by pagecache activity. But note that there may be
* stalls if we need to run get_block(). We could test
* PagePrivate for that.
*
* If this process is currently in __generic_file_write_iter() against
* this page's queue, we can perform writeback even if that
* will block.
*
* If the page is swapcache, write it back even if that would
* block, for some throttling. This happens by accident, because
* swap_backing_dev_info is bust: it doesn't reflect the
* congestion state of the swapdevs. Easy to fix, if needed.
*/
if (!is_page_cache_freeable(page))
return PAGE_KEEP;
if (!mapping) {
/*
* Some data journaling orphaned pages can have
* page->mapping == NULL while being dirty with clean buffers.
*/
if (page_has_private(page)) {
if (try_to_free_buffers(page)) {
ClearPageDirty(page);
pr_info("%s: orphaned page\n", __func__);
return PAGE_CLEAN;
}
}
return PAGE_KEEP;
}
if (mapping->a_ops->writepage == NULL)
return PAGE_ACTIVATE;
if (!may_write_to_inode(mapping->host))
return PAGE_KEEP;
if (clear_page_dirty_for_io(page)) {
int res;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.nr_to_write = SWAP_CLUSTER_MAX,
.range_start = 0,
.range_end = LLONG_MAX,
.for_reclaim = 1,
};
SetPageReclaim(page);
res = mapping->a_ops->writepage(page, &wbc);
if (res < 0)
handle_write_error(mapping, page, res);
if (res == AOP_WRITEPAGE_ACTIVATE) {
ClearPageReclaim(page);
return PAGE_ACTIVATE;
}
if (!PageWriteback(page)) {
/* synchronous write or broken a_ops? */
ClearPageReclaim(page);
}
trace_mm_vmscan_writepage(page);
inc_node_page_state(page, NR_VMSCAN_WRITE);
return PAGE_SUCCESS;
}
return PAGE_CLEAN;
}
/*
* Same as remove_mapping, but if the page is removed from the mapping, it
* gets returned with a refcount of 0.
*/
static int __remove_mapping(struct address_space *mapping, struct page *page,
bool reclaimed, struct mem_cgroup *target_memcg)
{
int refcount;
void *shadow = NULL;
BUG_ON(!PageLocked(page));
BUG_ON(mapping != page_mapping(page));
xa_lock_irq(&mapping->i_pages);
/*
* The non racy check for a busy page.
*
* Must be careful with the order of the tests. When someone has
* a ref to the page, it may be possible that they dirty it then
* drop the reference. So if PageDirty is tested before page_count
* here, then the following race may occur:
*
* get_user_pages(&page);
* [user mapping goes away]
* write_to(page);
* !PageDirty(page) [good]
* SetPageDirty(page);
* put_page(page);
* !page_count(page) [good, discard it]
*
* [oops, our write_to data is lost]
*
* Reversing the order of the tests ensures such a situation cannot
* escape unnoticed. The smp_rmb is needed to ensure the page->flags
* load is not satisfied before that of page->_refcount.
*
* Note that if SetPageDirty is always performed via set_page_dirty,
* and thus under the i_pages lock, then this ordering is not required.
*/
refcount = 1 + compound_nr(page);
if (!page_ref_freeze(page, refcount))
goto cannot_free;
/* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
if (unlikely(PageDirty(page))) {
page_ref_unfreeze(page, refcount);
goto cannot_free;
}
if (PageSwapCache(page)) {
swp_entry_t swap = { .val = page_private(page) };
/* get a shadow entry before mem_cgroup_swapout() clears page_memcg() */
if (reclaimed && !mapping_exiting(mapping))
shadow = workingset_eviction(page, target_memcg);
mem_cgroup_swapout(page, swap);
__delete_from_swap_cache(page, swap, shadow);
xa_unlock_irq(&mapping->i_pages);
put_swap_page(page, swap);
} else {
void (*freepage)(struct page *);
freepage = mapping->a_ops->freepage;
/*
* Remember a shadow entry for reclaimed file cache in
* order to detect refaults, thus thrashing, later on.
*
* But don't store shadows in an address space that is
* already exiting. This is not just an optimization,
* inode reclaim needs to empty out the radix tree or
* the nodes are lost. Don't plant shadows behind its
* back.
*
* We also don't store shadows for DAX mappings because the
* only page cache pages found in these are zero pages
* covering holes, and because we don't want to mix DAX
* exceptional entries and shadow exceptional entries in the
* same address_space.
*/
if (reclaimed && page_is_file_lru(page) &&
!mapping_exiting(mapping) && !dax_mapping(mapping))
shadow = workingset_eviction(page, target_memcg);
__delete_from_page_cache(page, shadow);
xa_unlock_irq(&mapping->i_pages);
if (freepage != NULL)
freepage(page);
}
return 1;
cannot_free:
xa_unlock_irq(&mapping->i_pages);
return 0;
}
/*
* Attempt to detach a locked page from its ->mapping. If it is dirty or if
* someone else has a ref on the page, abort and return 0. If it was
* successfully detached, return 1. Assumes the caller has a single ref on
* this page.
*/
int remove_mapping(struct address_space *mapping, struct page *page)
{
if (__remove_mapping(mapping, page, false, NULL)) {
/*
* Unfreezing the refcount with 1 rather than 2 effectively
* drops the pagecache ref for us without requiring another
* atomic operation.
*/
page_ref_unfreeze(page, 1);
return 1;
}
return 0;
}
/**
* putback_lru_page - put previously isolated page onto appropriate LRU list
* @page: page to be put back to appropriate lru list
*
* Add previously isolated @page to appropriate LRU list.
* Page may still be unevictable for other reasons.
*
* lru_lock must not be held, interrupts must be enabled.
*/
void putback_lru_page(struct page *page)
{
lru_cache_add(page);
put_page(page); /* drop ref from isolate */
}
enum page_references {
PAGEREF_RECLAIM,
PAGEREF_RECLAIM_CLEAN,
PAGEREF_KEEP,
PAGEREF_ACTIVATE,
};
static enum page_references page_check_references(struct page *page,
struct scan_control *sc)
{
int referenced_ptes, referenced_page;
unsigned long vm_flags;
referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup,
&vm_flags);
referenced_page = TestClearPageReferenced(page);
/*
* Mlock lost the isolation race with us. Let try_to_unmap()
* move the page to the unevictable list.
*/
if (vm_flags & VM_LOCKED)
return PAGEREF_RECLAIM;
if (referenced_ptes) {
/*
* All mapped pages start out with page table
* references from the instantiating fault, so we need
* to look twice if a mapped file page is used more
* than once.
*
* Mark it and spare it for another trip around the
* inactive list. Another page table reference will
* lead to its activation.
*
* Note: the mark is set for activated pages as well
* so that recently deactivated but used pages are
* quickly recovered.
*/
SetPageReferenced(page);
if (referenced_page || referenced_ptes > 1)
return PAGEREF_ACTIVATE;
/*
* Activate file-backed executable pages after first usage.
*/
if ((vm_flags & VM_EXEC) && !PageSwapBacked(page))
return PAGEREF_ACTIVATE;
return PAGEREF_KEEP;
}
/* Reclaim if clean, defer dirty pages to writeback */
if (referenced_page && !PageSwapBacked(page))
return PAGEREF_RECLAIM_CLEAN;
return PAGEREF_RECLAIM;
}
/* Check if a page is dirty or under writeback */
static void page_check_dirty_writeback(struct page *page,
bool *dirty, bool *writeback)
{
struct address_space *mapping;
/*
* Anonymous pages are not handled by flushers and must be written
* from reclaim context. Do not stall reclaim based on them
*/
if (!page_is_file_lru(page) ||
(PageAnon(page) && !PageSwapBacked(page))) {
*dirty = false;
*writeback = false;
return;
}
/* By default assume that the page flags are accurate */
*dirty = PageDirty(page);
*writeback = PageWriteback(page);
/* Verify dirty/writeback state if the filesystem supports it */
if (!page_has_private(page))
return;
mapping = page_mapping(page);
if (mapping && mapping->a_ops->is_dirty_writeback)
mapping->a_ops->is_dirty_writeback(page, dirty, writeback);
}
static struct page *alloc_demote_page(struct page *page, unsigned long node)
{
struct migration_target_control mtc = {
/*
* Allocate from 'node', or fail quickly and quietly.
* When this happens, 'page' will likely just be discarded
* instead of migrated.
*/
.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) |
__GFP_THISNODE | __GFP_NOWARN |
__GFP_NOMEMALLOC | GFP_NOWAIT,
.nid = node
};
return alloc_migration_target(page, (unsigned long)&mtc);
}
/*
* Take pages on @demote_list and attempt to demote them to
* another node. Pages which are not demoted are left on
* @demote_pages.
*/
static unsigned int demote_page_list(struct list_head *demote_pages,
struct pglist_data *pgdat)
{
int target_nid = next_demotion_node(pgdat->node_id);
unsigned int nr_succeeded;
int err;
if (list_empty(demote_pages))
return 0;
if (target_nid == NUMA_NO_NODE)
return 0;
/* Demotion ignores all cpuset and mempolicy settings */
err = migrate_pages(demote_pages, alloc_demote_page, NULL,
target_nid, MIGRATE_ASYNC, MR_DEMOTION,
&nr_succeeded);
if (current_is_kswapd())
__count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
else
__count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
return nr_succeeded;
}
/*
* shrink_page_list() returns the number of reclaimed pages
*/
static unsigned int shrink_page_list(struct list_head *page_list,
struct pglist_data *pgdat,
struct scan_control *sc,
struct reclaim_stat *stat,
bool ignore_references)
{
LIST_HEAD(ret_pages);
LIST_HEAD(free_pages);
LIST_HEAD(demote_pages);
unsigned int nr_reclaimed = 0;
unsigned int pgactivate = 0;
bool do_demote_pass;
memset(stat, 0, sizeof(*stat));
cond_resched();
do_demote_pass = can_demote(pgdat->node_id, sc);
retry:
while (!list_empty(page_list)) {
struct address_space *mapping;
struct page *page;
enum page_references references = PAGEREF_RECLAIM;
bool dirty, writeback, may_enter_fs;
unsigned int nr_pages;
cond_resched();
page = lru_to_page(page_list);
list_del(&page->lru);
if (!trylock_page(page))
goto keep;
VM_BUG_ON_PAGE(PageActive(page), page);
nr_pages = compound_nr(page);
/* Account the number of base pages even though THP */
sc->nr_scanned += nr_pages;
if (unlikely(!page_evictable(page)))
goto activate_locked;
if (!sc->may_unmap && page_mapped(page))
goto keep_locked;
/* page_update_gen() tried to promote this page? */
if (lru_gen_enabled() && !ignore_references &&
page_mapped(page) && PageReferenced(page))
goto keep_locked;
may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
(PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
/*
* The number of dirty pages determines if a node is marked
* reclaim_congested which affects wait_iff_congested. kswapd
* will stall and start writing pages if the tail of the LRU
* is all dirty unqueued pages.
*/
page_check_dirty_writeback(page, &dirty, &writeback);
if (dirty || writeback)
stat->nr_dirty++;
if (dirty && !writeback)
stat->nr_unqueued_dirty++;
/*
* Treat this page as congested if the underlying BDI is or if
* pages are cycling through the LRU so quickly that the
* pages marked for immediate reclaim are making it to the
* end of the LRU a second time.
*/
mapping = page_mapping(page);
if (((dirty || writeback) && mapping &&
inode_write_congested(mapping->host)) ||
(writeback && PageReclaim(page)))
stat->nr_congested++;
/*
* If a page at the tail of the LRU is under writeback, there
* are three cases to consider.
*
* 1) If reclaim is encountering an excessive number of pages
* under writeback and this page is both under writeback and
* PageReclaim then it indicates that pages are being queued
* for IO but are being recycled through the LRU before the
* IO can complete. Waiting on the page itself risks an
* indefinite stall if it is impossible to writeback the
* page due to IO error or disconnected storage so instead
* note that the LRU is being scanned too quickly and the
* caller can stall after page list has been processed.
*
* 2) Global or new memcg reclaim encounters a page that is
* not marked for immediate reclaim, or the caller does not
* have __GFP_FS (or __GFP_IO if it's simply going to swap,
* not to fs). In this case mark the page for immediate
* reclaim and continue scanning.
*
* Require may_enter_fs because we would wait on fs, which
* may not have submitted IO yet. And the loop driver might
* enter reclaim, and deadlock if it waits on a page for
* which it is needed to do the write (loop masks off
* __GFP_IO|__GFP_FS for this reason); but more thought
* would probably show more reasons.
*
* 3) Legacy memcg encounters a page that is already marked
* PageReclaim. memcg does not have any dirty pages
* throttling so we could easily OOM just because too many
* pages are in writeback and there is nothing else to
* reclaim. Wait for the writeback to complete.
*
* In cases 1) and 2) we activate the pages to get them out of
* the way while we continue scanning for clean pages on the
* inactive list and refilling from the active list. The
* observation here is that waiting for disk writes is more
* expensive than potentially causing reloads down the line.
* Since they're marked for immediate reclaim, they won't put
* memory pressure on the cache working set any longer than it
* takes to write them to disk.
*/
if (PageWriteback(page)) {
/* Case 1 above */
if (current_is_kswapd() &&
PageReclaim(page) &&
test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
stat->nr_immediate++;
goto activate_locked;
/* Case 2 above */
} else if (writeback_throttling_sane(sc) ||
!PageReclaim(page) || !may_enter_fs) {
/*
* This is slightly racy - end_page_writeback()
* might have just cleared PageReclaim, then
* setting PageReclaim here end up interpreted
* as PageReadahead - but that does not matter
* enough to care. What we do want is for this
* page to have PageReclaim set next time memcg
* reclaim reaches the tests above, so it will
* then wait_on_page_writeback() to avoid OOM;
* and it's also appropriate in global reclaim.
*/
SetPageReclaim(page);
stat->nr_writeback++;
goto activate_locked;
/* Case 3 above */
} else {
unlock_page(page);
wait_on_page_writeback(page);
/* then go back and try same page again */
list_add_tail(&page->lru, page_list);
continue;
}
}
if (!ignore_references)
references = page_check_references(page, sc);
switch (references) {
case PAGEREF_ACTIVATE:
goto activate_locked;
case PAGEREF_KEEP:
stat->nr_ref_keep += nr_pages;
goto keep_locked;
case PAGEREF_RECLAIM:
case PAGEREF_RECLAIM_CLEAN:
; /* try to reclaim the page below */
}
/*
* Before reclaiming the page, try to relocate
* its contents to another node.
*/
if (do_demote_pass &&
(thp_migration_supported() || !PageTransHuge(page))) {
list_add(&page->lru, &demote_pages);
unlock_page(page);
continue;
}
/*
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
* Lazyfree page could be freed directly
*/
if (PageAnon(page) && PageSwapBacked(page)) {
if (!PageSwapCache(page)) {
if (!(sc->gfp_mask & __GFP_IO))
goto keep_locked;
if (page_maybe_dma_pinned(page))
goto keep_locked;
if (PageTransHuge(page)) {
/* cannot split THP, skip it */
if (!can_split_huge_page(page, NULL))
goto activate_locked;
/*
* Split pages without a PMD map right
* away. Chances are some or all of the
* tail pages can be freed without IO.
*/
if (!compound_mapcount(page) &&
split_huge_page_to_list(page,
page_list))
goto activate_locked;
}
if (!add_to_swap(page)) {
if (!PageTransHuge(page))
goto activate_locked_split;
/* Fallback to swap normal pages */
if (split_huge_page_to_list(page,
page_list))
goto activate_locked;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
count_vm_event(THP_SWPOUT_FALLBACK);
#endif
if (!add_to_swap(page))
goto activate_locked_split;
}
may_enter_fs = true;
/* Adding to swap updated mapping */
mapping = page_mapping(page);
}
} else if (unlikely(PageTransHuge(page))) {
/* Split file THP */
if (split_huge_page_to_list(page, page_list))
goto keep_locked;
}
/*
* THP may get split above, need minus tail pages and update
* nr_pages to avoid accounting tail pages twice.
*
* The tail pages that are added into swap cache successfully
* reach here.
*/
if ((nr_pages > 1) && !PageTransHuge(page)) {
sc->nr_scanned -= (nr_pages - 1);
nr_pages = 1;
}
/*
* The page is mapped into the page tables of one or more
* processes. Try to unmap it here.
*/
if (page_mapped(page)) {
enum ttu_flags flags = TTU_BATCH_FLUSH;
bool was_swapbacked = PageSwapBacked(page);
if (unlikely(PageTransHuge(page)))
flags |= TTU_SPLIT_HUGE_PMD;
try_to_unmap(page, flags);
if (page_mapped(page)) {
stat->nr_unmap_fail += nr_pages;
if (!was_swapbacked && PageSwapBacked(page))
stat->nr_lazyfree_fail += nr_pages;
goto activate_locked;
}
}
if (PageDirty(page)) {
/*
* Only kswapd can writeback filesystem pages
* to avoid risk of stack overflow. But avoid
* injecting inefficient single-page IO into
* flusher writeback as much as possible: only
* write pages when we've encountered many
* dirty pages, and when we've already scanned
* the rest of the LRU for clean pages and see
* the same dirty pages again (PageReclaim).
*/
if (page_is_file_lru(page) &&
(!current_is_kswapd() || !PageReclaim(page) ||
!test_bit(PGDAT_DIRTY, &pgdat->flags))) {
/*
* Immediately reclaim when written back.
* Similar in principal to deactivate_page()
* except we already have the page isolated
* and know it's dirty
*/
inc_node_page_state(page, NR_VMSCAN_IMMEDIATE);
SetPageReclaim(page);
goto activate_locked;
}
if (references == PAGEREF_RECLAIM_CLEAN)
goto keep_locked;
if (!may_enter_fs)
goto keep_locked;
if (!sc->may_writepage)
goto keep_locked;
/*
* Page is dirty. Flush the TLB if a writable entry
* potentially exists to avoid CPU writes after IO
* starts and then write it out here.
*/
try_to_unmap_flush_dirty();
switch (pageout(page, mapping)) {
case PAGE_KEEP:
goto keep_locked;
case PAGE_ACTIVATE:
goto activate_locked;
case PAGE_SUCCESS:
stat->nr_pageout += thp_nr_pages(page);
if (PageWriteback(page))
goto keep;
if (PageDirty(page))
goto keep;
/*
* A synchronous write - probably a ramdisk. Go
* ahead and try to reclaim the page.
*/
if (!trylock_page(page))
goto keep;
if (PageDirty(page) || PageWriteback(page))
goto keep_locked;
mapping = page_mapping(page);
fallthrough;
case PAGE_CLEAN:
; /* try to free the page below */
}
}
/*
* If the page has buffers, try to free the buffer mappings
* associated with this page. If we succeed we try to free
* the page as well.
*
* We do this even if the page is PageDirty().
* try_to_release_page() does not perform I/O, but it is
* possible for a page to have PageDirty set, but it is actually
* clean (all its buffers are clean). This happens if the
* buffers were written out directly, with submit_bh(). ext3
* will do this, as well as the blockdev mapping.
* try_to_release_page() will discover that cleanness and will
* drop the buffers and mark the page clean - it can be freed.
*
* Rarely, pages can have buffers and no ->mapping. These are
* the pages which were not successfully invalidated in
* truncate_cleanup_page(). We try to drop those buffers here
* and if that worked, and the page is no longer mapped into
* process address space (page_count == 1) it can be freed.
* Otherwise, leave the page on the LRU so it is swappable.
*/
if (page_has_private(page)) {
if (!try_to_release_page(page, sc->gfp_mask))
goto activate_locked;
if (!mapping && page_count(page) == 1) {
unlock_page(page);
if (put_page_testzero(page))
goto free_it;
else {
/*
* rare race with speculative reference.
* the speculative reference will free
* this page shortly, so we may
* increment nr_reclaimed here (and
* leave it off the LRU).
*/
nr_reclaimed++;
continue;
}
}
}
if (PageAnon(page) && !PageSwapBacked(page)) {
/* follow __remove_mapping for reference */
if (!page_ref_freeze(page, 1))
goto keep_locked;
/*
* The page has only one reference left, which is
* from the isolation. After the caller puts the
* page back on lru and drops the reference, the
* page will be freed anyway. It doesn't matter
* which lru it goes. So we don't bother checking
* PageDirty here.
*/
count_vm_event(PGLAZYFREED);
count_memcg_page_event(page, PGLAZYFREED);
} else if (!mapping || !__remove_mapping(mapping, page, true,
sc->target_mem_cgroup))
goto keep_locked;
unlock_page(page);
free_it:
/*
* THP may get swapped out in a whole, need account
* all base pages.
*/
nr_reclaimed += nr_pages;
/*
* Is there need to periodically free_page_list? It would
* appear not as the counts should be low
*/
if (unlikely(PageTransHuge(page)))
destroy_compound_page(page);
else
list_add(&page->lru, &free_pages);
continue;
activate_locked_split:
/*
* The tail pages that are failed to add into swap cache
* reach here. Fixup nr_scanned and nr_pages.
*/
if (nr_pages > 1) {
sc->nr_scanned -= (nr_pages - 1);
nr_pages = 1;
}
activate_locked:
/* Not a candidate for swapping, so reclaim swap space. */
if (PageSwapCache(page) && (mem_cgroup_swap_full(page) ||
PageMlocked(page)))
try_to_free_swap(page);
VM_BUG_ON_PAGE(PageActive(page), page);
if (!PageMlocked(page)) {
int type = page_is_file_lru(page);
SetPageActive(page);
stat->nr_activate[type] += nr_pages;
count_memcg_page_event(page, PGACTIVATE);
}
keep_locked:
unlock_page(page);
keep:
list_add(&page->lru, &ret_pages);
VM_BUG_ON_PAGE(PageLRU(page) || PageUnevictable(page), page);
}
/* 'page_list' is always empty here */
/* Migrate pages selected for demotion */
nr_reclaimed += demote_page_list(&demote_pages, pgdat);
/* Pages that could not be demoted are still in @demote_pages */
if (!list_empty(&demote_pages)) {
/* Pages which failed to demoted go back on @page_list for retry: */
list_splice_init(&demote_pages, page_list);
do_demote_pass = false;
goto retry;
}
pgactivate = stat->nr_activate[0] + stat->nr_activate[1];
mem_cgroup_uncharge_list(&free_pages);
try_to_unmap_flush();
free_unref_page_list(&free_pages);
list_splice(&ret_pages, page_list);
count_vm_events(PGACTIVATE, pgactivate);
return nr_reclaimed;
}
unsigned int reclaim_clean_pages_from_list(struct zone *zone,
struct list_head *page_list)
{
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_unmap = 1,
};
struct reclaim_stat stat;
unsigned int nr_reclaimed;
struct page *page, *next;
LIST_HEAD(clean_pages);
unsigned int noreclaim_flag;
list_for_each_entry_safe(page, next, page_list, lru) {
if (!PageHuge(page) && page_is_file_lru(page) &&
!PageDirty(page) && !__PageMovable(page) &&
!PageUnevictable(page)) {
ClearPageActive(page);
list_move(&page->lru, &clean_pages);
}
}
/*
* We should be safe here since we are only dealing with file pages and
* we are not kswapd and therefore cannot write dirty file pages. But
* call memalloc_noreclaim_save() anyway, just in case these conditions
* change in the future.
*/
noreclaim_flag = memalloc_noreclaim_save();
nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc,
&stat, true);
memalloc_noreclaim_restore(noreclaim_flag);
list_splice(&clean_pages, page_list);
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
-(long)nr_reclaimed);
/*
* Since lazyfree pages are isolated from file LRU from the beginning,
* they will rotate back to anonymous LRU in the end if it failed to
* discard so isolated count will be mismatched.
* Compensate the isolated count for both LRU lists.
*/
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON,
stat.nr_lazyfree_fail);
mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE,
-(long)stat.nr_lazyfree_fail);
return nr_reclaimed;
}
/*
* Attempt to remove the specified page from its LRU. Only take this page
* if it is of the appropriate PageActive status. Pages which are being
* freed elsewhere are also ignored.
*
* page: page to consider
* mode: one of the LRU isolation modes defined above
*
* returns true on success, false on failure.
*/
bool __isolate_lru_page_prepare(struct page *page, isolate_mode_t mode)
{
/* Only take pages on the LRU. */
if (!PageLRU(page))
return false;
/* Compaction should not handle unevictable pages but CMA can do so */
if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE))
return false;
/*
* To minimise LRU disruption, the caller can indicate that it only
* wants to isolate pages it will be able to operate on without
* blocking - clean pages for the most part.
*
* ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
* that it is possible to migrate without blocking
*/
if (mode & ISOLATE_ASYNC_MIGRATE) {
/* All the caller can do on PageWriteback is block */
if (PageWriteback(page))
return false;
if (PageDirty(page)) {
struct address_space *mapping;
bool migrate_dirty;
/*
* Only pages without mappings or that have a
* ->migratepage callback are possible to migrate
* without blocking. However, we can be racing with
* truncation so it's necessary to lock the page
* to stabilise the mapping as truncation holds
* the page lock until after the page is removed
* from the page cache.
*/
if (!trylock_page(page))
return false;
mapping = page_mapping(page);
migrate_dirty = !mapping || mapping->a_ops->migratepage;
unlock_page(page);
if (!migrate_dirty)
return false;
}
}
if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
return false;
return true;
}
/*
* Update LRU sizes after isolating pages. The LRU size updates must
* be complete before mem_cgroup_update_lru_size due to a sanity check.
*/
static __always_inline void update_lru_sizes(struct lruvec *lruvec,
enum lru_list lru, unsigned long *nr_zone_taken)
{
int zid;
for (zid = 0; zid < MAX_NR_ZONES; zid++) {
if (!nr_zone_taken[zid])
continue;
update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
}
}
/*
* Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
*
* lruvec->lru_lock is heavily contended. Some of the functions that
* shrink the lists perform better by taking out a batch of pages
* and working on them outside the LRU lock.
*
* For pagecache intensive workloads, this function is the hottest
* spot in the kernel (apart from copy_*_user functions).
*
* Lru_lock must be held before calling this function.
*
* @nr_to_scan: The number of eligible pages to look through on the list.
* @lruvec: The LRU vector to pull pages from.
* @dst: The temp list to put pages on to.
* @nr_scanned: The number of pages that were scanned.
* @sc: The scan_control struct for this reclaim session
* @lru: LRU list id for isolating
*
* returns how many pages were moved onto *@dst.
*/
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
struct lruvec *lruvec, struct list_head *dst,
unsigned long *nr_scanned, struct scan_control *sc,
enum lru_list lru)
{
struct list_head *src = &lruvec->lists[lru];
unsigned long nr_taken = 0;
unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
unsigned long skipped = 0;
unsigned long scan, total_scan, nr_pages;
LIST_HEAD(pages_skipped);
isolate_mode_t mode = (sc->may_unmap ? 0 : ISOLATE_UNMAPPED);
total_scan = 0;
scan = 0;
while (scan < nr_to_scan && !list_empty(src)) {
struct page *page;
page = lru_to_page(src);
prefetchw_prev_lru_page(page, src, flags);
nr_pages = compound_nr(page);
total_scan += nr_pages;
if (page_zonenum(page) > sc->reclaim_idx) {
list_move(&page->lru, &pages_skipped);
nr_skipped[page_zonenum(page)] += nr_pages;
continue;
}
/*
* Do not count skipped pages because that makes the function
* return with no isolated pages if the LRU mostly contains
* ineligible pages. This causes the VM to not reclaim any
* pages, triggering a premature OOM.
*
* Account all tail pages of THP. This would not cause
* premature OOM since __isolate_lru_page() returns -EBUSY
* only when the page is being freed somewhere else.
*/
scan += nr_pages;
if (!__isolate_lru_page_prepare(page, mode)) {
/* It is being freed elsewhere */
list_move(&page->lru, src);
continue;
}
/*
* Be careful not to clear PageLRU until after we're
* sure the page is not being freed elsewhere -- the
* page release code relies on it.
*/
if (unlikely(!get_page_unless_zero(page))) {
list_move(&page->lru, src);
continue;
}
if (!TestClearPageLRU(page)) {
/* Another thread is already isolating this page */
put_page(page);
list_move(&page->lru, src);
continue;
}
nr_taken += nr_pages;
nr_zone_taken[page_zonenum(page)] += nr_pages;
list_move(&page->lru, dst);
}
/*
* Splice any skipped pages to the start of the LRU list. Note that
* this disrupts the LRU order when reclaiming for lower zones but
* we cannot splice to the tail. If we did then the SWAP_CLUSTER_MAX
* scanning would soon rescan the same pages to skip and put the
* system at risk of premature OOM.
*/
if (!list_empty(&pages_skipped)) {
int zid;
list_splice(&pages_skipped, src);
for (zid = 0; zid < MAX_NR_ZONES; zid++) {
if (!nr_skipped[zid])
continue;
__count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]);
skipped += nr_skipped[zid];
}
}
*nr_scanned = total_scan;
trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
total_scan, skipped, nr_taken, mode, lru);
update_lru_sizes(lruvec, lru, nr_zone_taken);
return nr_taken;
}
/**
* isolate_lru_page - tries to isolate a page from its LRU list
* @page: page to isolate from its LRU list
*
* Isolates a @page from an LRU list, clears PageLRU and adjusts the
* vmstat statistic corresponding to whatever LRU list the page was on.
*
* Returns 0 if the page was removed from an LRU list.
* Returns -EBUSY if the page was not on an LRU list.
*
* The returned page will have PageLRU() cleared. If it was found on
* the active list, it will have PageActive set. If it was found on
* the unevictable list, it will have the PageUnevictable bit set. That flag
* may need to be cleared by the caller before letting the page go.
*
* The vmstat statistic corresponding to the list on which the page was
* found will be decremented.
*
* Restrictions:
*
* (1) Must be called with an elevated refcount on the page. This is a
* fundamental difference from isolate_lru_pages (which is called
* without a stable reference).
* (2) the lru_lock must not be held.
* (3) interrupts must be enabled.
*/
int isolate_lru_page(struct page *page)
{
int ret = -EBUSY;
VM_BUG_ON_PAGE(!page_count(page), page);
WARN_RATELIMIT(PageTail(page), "trying to isolate tail page");
if (TestClearPageLRU(page)) {
struct lruvec *lruvec;
get_page(page);
lruvec = lock_page_lruvec_irq(page);
del_page_from_lru_list(page, lruvec);
unlock_page_lruvec_irq(lruvec);
ret = 0;
}
return ret;
}
/*
* A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and
* then get rescheduled. When there are massive number of tasks doing page
* allocation, such sleeping direct reclaimers may keep piling up on each CPU,
* the LRU list will go small and be scanned faster than necessary, leading to
* unnecessary swapping, thrashing and OOM.
*/
static int too_many_isolated(struct pglist_data *pgdat, int file,
struct scan_control *sc)
{
unsigned long inactive, isolated;
if (current_is_kswapd())
return 0;
if (!writeback_throttling_sane(sc))
return 0;
if (file) {
inactive = node_page_state(pgdat, NR_INACTIVE_FILE);
isolated = node_page_state(pgdat, NR_ISOLATED_FILE);
} else {
inactive = node_page_state(pgdat, NR_INACTIVE_ANON);
isolated = node_page_state(pgdat, NR_ISOLATED_ANON);
}
/*
* GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they
* won't get blocked by normal direct-reclaimers, forming a circular
* deadlock.
*/
if ((sc->gfp_mask & (__GFP_IO | __GFP_FS)) == (__GFP_IO | __GFP_FS))
inactive >>= 3;
return isolated > inactive;
}
/*
* move_pages_to_lru() moves pages from private @list to appropriate LRU list.
* On return, @list is reused as a list of pages to be freed by the caller.
*
* Returns the number of pages moved to the given lruvec.
*/
static unsigned int move_pages_to_lru(struct lruvec *lruvec,
struct list_head *list)
{
int nr_pages, nr_moved = 0;
LIST_HEAD(pages_to_free);
struct page *page;
while (!list_empty(list)) {
page = lru_to_page(list);
VM_BUG_ON_PAGE(PageLRU(page), page);
list_del(&page->lru);
if (unlikely(!page_evictable(page))) {
spin_unlock_irq(&lruvec->lru_lock);
putback_lru_page(page);
spin_lock_irq(&lruvec->lru_lock);
continue;
}
/*
* The SetPageLRU needs to be kept here for list integrity.
* Otherwise:
* #0 move_pages_to_lru #1 release_pages
* if !put_page_testzero
* if (put_page_testzero())
* !PageLRU //skip lru_lock
* SetPageLRU()
* list_add(&page->lru,)
* list_add(&page->lru,)
*/
SetPageLRU(page);
if (unlikely(put_page_testzero(page))) {
__clear_page_lru_flags(page);
if (unlikely(PageCompound(page))) {
spin_unlock_irq(&lruvec->lru_lock);
destroy_compound_page(page);
spin_lock_irq(&lruvec->lru_lock);
} else
list_add(&page->lru, &pages_to_free);
continue;
}
/*
* All pages were isolated from the same lruvec (and isolation
* inhibits memcg migration).
*/
VM_BUG_ON_PAGE(!page_matches_lruvec(page, lruvec), page);
add_page_to_lru_list(page, lruvec);
nr_pages = thp_nr_pages(page);
nr_moved += nr_pages;
if (PageActive(page))
workingset_age_nonresident(lruvec, nr_pages);
}
/*
* To save our caller's stack, now use input list for pages to free.
*/
list_splice(&pages_to_free, list);
return nr_moved;
}
/*
* If a kernel thread (such as nfsd for loop-back mounts) services
* a backing device by writing to the page cache it sets PF_LOCAL_THROTTLE.
* In that case we should only throttle if the backing device it is
* writing to is congested. In other cases it is safe to throttle.
*/
static int current_may_throttle(void)
{
return !(current->flags & PF_LOCAL_THROTTLE) ||
current->backing_dev_info == NULL ||
bdi_write_congested(current->backing_dev_info);
}
/*
* shrink_inactive_list() is a helper for shrink_node(). It returns the number
* of reclaimed pages
*/
static unsigned long
shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
struct scan_control *sc, enum lru_list lru)
{
LIST_HEAD(page_list);
unsigned long nr_scanned;
unsigned int nr_reclaimed = 0;
unsigned long nr_taken;
struct reclaim_stat stat;
bool file = is_file_lru(lru);
enum vm_event_item item;
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
bool stalled = false;
while (unlikely(too_many_isolated(pgdat, file, sc))) {
if (stalled)
return 0;
/* wait a bit for the reclaimer. */
msleep(100);
stalled = true;
/* We are about to die and free our memory. Return now. */
if (fatal_signal_pending(current))
return SWAP_CLUSTER_MAX;
}
lru_add_drain();
spin_lock_irq(&lruvec->lru_lock);
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list,
&nr_scanned, sc, lru);
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT;
if (!cgroup_reclaim(sc))
__count_vm_events(item, nr_scanned);
__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
__count_vm_events(PGSCAN_ANON + file, nr_scanned);
spin_unlock_irq(&lruvec->lru_lock);
if (nr_taken == 0)
return 0;
nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, &stat, false);
spin_lock_irq(&lruvec->lru_lock);
move_pages_to_lru(lruvec, &page_list);
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
if (!cgroup_reclaim(sc))
__count_vm_events(item, nr_reclaimed);
__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
spin_unlock_irq(&lruvec->lru_lock);
lru_note_cost(lruvec, file, stat.nr_pageout);
mem_cgroup_uncharge_list(&page_list);
free_unref_page_list(&page_list);
/*
* If dirty pages are scanned that are not queued for IO, it
* implies that flushers are not doing their job. This can
* happen when memory pressure pushes dirty pages to the end of
* the LRU before the dirty limits are breached and the dirty
* data has expired. It can also happen when the proportion of
* dirty pages grows not through writes but through memory
* pressure reclaiming all the clean cache. And in some cases,
* the flushers simply cannot keep up with the allocation
* rate. Nudge the flusher threads in case they are asleep.
*/
if (stat.nr_unqueued_dirty == nr_taken)
wakeup_flusher_threads(WB_REASON_VMSCAN);
sc->nr.dirty += stat.nr_dirty;
sc->nr.congested += stat.nr_congested;
sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
sc->nr.writeback += stat.nr_writeback;
sc->nr.immediate += stat.nr_immediate;
sc->nr.taken += nr_taken;
if (file)
sc->nr.file_taken += nr_taken;
trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
nr_scanned, nr_reclaimed, &stat, sc->priority, file);
return nr_reclaimed;
}
/*
* shrink_active_list() moves pages from the active LRU to the inactive LRU.
*
* We move them the other way if the page is referenced by one or more
* processes.
*
* If the pages are mostly unmapped, the processing is fast and it is
* appropriate to hold lru_lock across the whole operation. But if
* the pages are mapped, the processing is slow (page_referenced()), so
* we should drop lru_lock around each page. It's impossible to balance
* this, so instead we remove the pages from the LRU while processing them.
* It is safe to rely on PG_active against the non-LRU pages in here because
* nobody will play with that bit on a non-LRU page.
*
* The downside is that we have to touch page->_refcount against each page.
* But we had to alter page->flags anyway.
*/
static void shrink_active_list(unsigned long nr_to_scan,
struct lruvec *lruvec,
struct scan_control *sc,
enum lru_list lru)
{
unsigned long nr_taken;
unsigned long nr_scanned;
unsigned long vm_flags;
LIST_HEAD(l_hold); /* The pages which were snipped off */
LIST_HEAD(l_active);
LIST_HEAD(l_inactive);
struct page *page;
unsigned nr_deactivate, nr_activate;
unsigned nr_rotated = 0;
int file = is_file_lru(lru);
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
bool bypass = false;
lru_add_drain();
spin_lock_irq(&lruvec->lru_lock);
nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold,
&nr_scanned, sc, lru);
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
if (!cgroup_reclaim(sc))
__count_vm_events(PGREFILL, nr_scanned);
__count_memcg_events(lruvec_memcg(lruvec), PGREFILL, nr_scanned);
spin_unlock_irq(&lruvec->lru_lock);
while (!list_empty(&l_hold)) {
cond_resched();
page = lru_to_page(&l_hold);
list_del(&page->lru);
if (unlikely(!page_evictable(page))) {
putback_lru_page(page);
continue;
}
if (unlikely(buffer_heads_over_limit)) {
if (page_has_private(page) && trylock_page(page)) {
if (page_has_private(page))
try_to_release_page(page, 0);
unlock_page(page);
}
}
trace_android_vh_page_referenced_check_bypass(page, nr_to_scan, lru, &bypass);
if (bypass)
goto skip_page_referenced;
if (page_referenced(page, 0, sc->target_mem_cgroup,
&vm_flags)) {
/*
* Identify referenced, file-backed active pages and
* give them one more trip around the active list. So
* that executable code get better chances to stay in
* memory under moderate memory pressure. Anon pages
* are not likely to be evicted by use-once streaming
* IO, plus JVM can create lots of anon VM_EXEC pages,
* so we ignore them here.
*/
if ((vm_flags & VM_EXEC) && page_is_file_lru(page)) {
nr_rotated += thp_nr_pages(page);
list_add(&page->lru, &l_active);
continue;
}
}
skip_page_referenced:
ClearPageActive(page); /* we are de-activating */
SetPageWorkingset(page);
list_add(&page->lru, &l_inactive);
}
/*
* Move pages back to the lru list.
*/
spin_lock_irq(&lruvec->lru_lock);
nr_activate = move_pages_to_lru(lruvec, &l_active);
nr_deactivate = move_pages_to_lru(lruvec, &l_inactive);
/* Keep all free pages in l_active list */
list_splice(&l_inactive, &l_active);
__count_vm_events(PGDEACTIVATE, nr_deactivate);
__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
spin_unlock_irq(&lruvec->lru_lock);
mem_cgroup_uncharge_list(&l_active);
free_unref_page_list(&l_active);
trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
nr_deactivate, nr_rotated, sc->priority, file);
}
unsigned long reclaim_pages(struct list_head *page_list)
{
int nid = NUMA_NO_NODE;
unsigned int nr_reclaimed = 0;
LIST_HEAD(node_page_list);
struct reclaim_stat dummy_stat;
struct page *page;
unsigned int noreclaim_flag;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
.may_writepage = 1,
.may_unmap = 1,
.may_swap = 1,
.no_demotion = 1,
};
noreclaim_flag = memalloc_noreclaim_save();
while (!list_empty(page_list)) {
page = lru_to_page(page_list);
if (nid == NUMA_NO_NODE) {
nid = page_to_nid(page);
INIT_LIST_HEAD(&node_page_list);
}
if (nid == page_to_nid(page)) {
ClearPageActive(page);
list_move(&page->lru, &node_page_list);
continue;
}
nr_reclaimed += shrink_page_list(&node_page_list,
NODE_DATA(nid),
&sc, &dummy_stat, false);
while (!list_empty(&node_page_list)) {
page = lru_to_page(&node_page_list);
list_del(&page->lru);
putback_lru_page(page);
}
nid = NUMA_NO_NODE;
}
if (!list_empty(&node_page_list)) {
nr_reclaimed += shrink_page_list(&node_page_list,
NODE_DATA(nid),
&sc, &dummy_stat, false);
while (!list_empty(&node_page_list)) {
page = lru_to_page(&node_page_list);
list_del(&page->lru);
putback_lru_page(page);
}
}
memalloc_noreclaim_restore(noreclaim_flag);
return nr_reclaimed;
}
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
struct lruvec *lruvec, struct scan_control *sc)
{
if (is_active_lru(lru)) {
if (sc->may_deactivate & (1 << is_file_lru(lru)))
shrink_active_list(nr_to_scan, lruvec, sc, lru);
else
sc->skipped_deactivate = 1;
return 0;
}
return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
}
/*
* The inactive anon list should be small enough that the VM never has
* to do too much work.
*
* The inactive file list should be small enough to leave most memory
* to the established workingset on the scan-resistant active list,
* but large enough to avoid thrashing the aggregate readahead window.
*
* Both inactive lists should also be large enough that each inactive
* page has a chance to be referenced again before it is reclaimed.
*
* If that fails and refaulting is observed, the inactive list grows.
*
* The inactive_ratio is the target ratio of ACTIVE to INACTIVE pages
* on this LRU, maintained by the pageout code. An inactive_ratio
* of 3 means 3:1 or 25% of the pages are kept on the inactive list.
*
* total target max
* memory ratio inactive
* -------------------------------------
* 10MB 1 5MB
* 100MB 1 50MB
* 1GB 3 250MB
* 10GB 10 0.9GB
* 100GB 31 3GB
* 1TB 101 10GB
* 10TB 320 32GB
*/
static bool inactive_is_low(struct lruvec *lruvec, enum lru_list inactive_lru)
{
enum lru_list active_lru = inactive_lru + LRU_ACTIVE;
unsigned long inactive, active;
unsigned long inactive_ratio;
unsigned long gb;
inactive = lruvec_page_state(lruvec, NR_LRU_BASE + inactive_lru);
active = lruvec_page_state(lruvec, NR_LRU_BASE + active_lru);
gb = (inactive + active) >> (30 - PAGE_SHIFT);
if (gb)
inactive_ratio = int_sqrt(10 * gb);
else
inactive_ratio = 1;
return inactive * inactive_ratio < active;
}
enum scan_balance {
SCAN_EQUAL,
SCAN_FRACT,
SCAN_ANON,
SCAN_FILE,
};
static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc)
{
unsigned long file;
struct lruvec *target_lruvec;
if (lru_gen_enabled())
return;
target_lruvec = mem_cgroup_lruvec(sc->target_mem_cgroup, pgdat);
/*
* Flush the memory cgroup stats, so that we read accurate per-memcg
* lruvec stats for heuristics.
*/
mem_cgroup_flush_stats();
/*
* Determine the scan balance between anon and file LRUs.
*/
spin_lock_irq(&target_lruvec->lru_lock);
sc->anon_cost = target_lruvec->anon_cost;
sc->file_cost = target_lruvec->file_cost;
spin_unlock_irq(&target_lruvec->lru_lock);
/*
* Target desirable inactive:active list ratios for the anon
* and file LRU lists.
*/
if (!sc->force_deactivate) {
unsigned long refaults;
refaults = lruvec_page_state(target_lruvec,
WORKINGSET_ACTIVATE_ANON);
if (refaults != target_lruvec->refaults[0] ||
inactive_is_low(target_lruvec, LRU_INACTIVE_ANON))
sc->may_deactivate |= DEACTIVATE_ANON;
else
sc->may_deactivate &= ~DEACTIVATE_ANON;
/*
* When refaults are being observed, it means a new
* workingset is being established. Deactivate to get
* rid of any stale active pages quickly.
*/
refaults = lruvec_page_state(target_lruvec,
WORKINGSET_ACTIVATE_FILE);
if (refaults != target_lruvec->refaults[1] ||
inactive_is_low(target_lruvec, LRU_INACTIVE_FILE))
sc->may_deactivate |= DEACTIVATE_FILE;
else
sc->may_deactivate &= ~DEACTIVATE_FILE;
} else
sc->may_deactivate = DEACTIVATE_ANON | DEACTIVATE_FILE;
/*
* If we have plenty of inactive file pages that aren't
* thrashing, try to reclaim those first before touching
* anonymous pages.
*/
file = lruvec_page_state(target_lruvec, NR_INACTIVE_FILE);
if (file >> sc->priority && !(sc->may_deactivate & DEACTIVATE_FILE))
sc->cache_trim_mode = 1;
else
sc->cache_trim_mode = 0;
/*
* Prevent the reclaimer from falling into the cache trap: as
* cache pages start out inactive, every cache fault will tip
* the scan balance towards the file LRU. And as the file LRU
* shrinks, so does the window for rotation from references.
* This means we have a runaway feedback loop where a tiny
* thrashing file LRU becomes infinitely more attractive than
* anon pages. Try to detect this based on file LRU size.
*/
if (!cgroup_reclaim(sc)) {
unsigned long total_high_wmark = 0;
unsigned long free, anon;
int z;
free = sum_zone_node_page_state(pgdat->node_id, NR_FREE_PAGES);
file = node_page_state(pgdat, NR_ACTIVE_FILE) +
node_page_state(pgdat, NR_INACTIVE_FILE);
for (z = 0; z < MAX_NR_ZONES; z++) {
struct zone *zone = &pgdat->node_zones[z];
if (!managed_zone(zone))
continue;
total_high_wmark += high_wmark_pages(zone);
}
/*
* Consider anon: if that's low too, this isn't a
* runaway file reclaim problem, but rather just
* extreme pressure. Reclaim as per usual then.
*/
anon = node_page_state(pgdat, NR_INACTIVE_ANON);
sc->file_is_tiny =
file + free <= total_high_wmark &&
!(sc->may_deactivate & DEACTIVATE_ANON) &&
anon >> sc->priority;
}
}
/*
* Determine how aggressively the anon and file LRU lists should be
* scanned. The relative value of each set of LRU lists is determined
* by looking at the fraction of the pages scanned we did rotate back
* onto the active list instead of evict.
*
* nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan
* nr[2] = file inactive pages to scan; nr[3] = file active pages to scan
*/
static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
unsigned long *nr)
{
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
unsigned long anon_cost, file_cost, total_cost;
int swappiness = mem_cgroup_swappiness(memcg);
u64 fraction[ANON_AND_FILE];
u64 denominator = 0; /* gcc */
enum scan_balance scan_balance;
unsigned long ap, fp;
enum lru_list lru;
bool balance_anon_file_reclaim = false;
/* If we have no swap space, do not bother scanning anon pages. */
if (!sc->may_swap || !can_reclaim_anon_pages(memcg, pgdat->node_id, sc)) {
scan_balance = SCAN_FILE;
goto out;
}
trace_android_vh_tune_swappiness(&swappiness);
/*
* Global reclaim will swap to prevent OOM even with no
* swappiness, but memcg users want to use this knob to
* disable swapping for individual groups completely when
* using the memory controller's swap limit feature would be
* too expensive.
*/
if (cgroup_reclaim(sc) && !swappiness) {
scan_balance = SCAN_FILE;
goto out;
}
/*
* Do not apply any pressure balancing cleverness when the
* system is close to OOM, scan both anon and file equally
* (unless the swappiness setting disagrees with swapping).
*/
if (!sc->priority && swappiness) {
scan_balance = SCAN_EQUAL;
goto out;
}
/*
* If the system is almost out of file pages, force-scan anon.
*/
if (sc->file_is_tiny) {
scan_balance = SCAN_ANON;
goto out;
}
trace_android_rvh_set_balance_anon_file_reclaim(&balance_anon_file_reclaim);
/*
* If there is enough inactive page cache, we do not reclaim
* anything from the anonymous working right now. But when balancing
* anon and page cache files for reclaim, allow swapping of anon pages
* even if there are a number of inactive file cache pages.
*/
if (!balance_anon_file_reclaim && sc->cache_trim_mode) {
scan_balance = SCAN_FILE;
goto out;
}
scan_balance = SCAN_FRACT;
/*
* Calculate the pressure balance between anon and file pages.
*
* The amount of pressure we put on each LRU is inversely
* proportional to the cost of reclaiming each list, as
* determined by the share of pages that are refaulting, times
* the relative IO cost of bringing back a swapped out
* anonymous page vs reloading a filesystem page (swappiness).
*
* Although we limit that influence to ensure no list gets
* left behind completely: at least a third of the pressure is
* applied, before swappiness.
*
* With swappiness at 100, anon and file have equal IO cost.
*/
total_cost = sc->anon_cost + sc->file_cost;
anon_cost = total_cost + sc->anon_cost;
file_cost = total_cost + sc->file_cost;
total_cost = anon_cost + file_cost;
ap = swappiness * (total_cost + 1);
ap /= anon_cost + 1;
fp = (200 - swappiness) * (total_cost + 1);
fp /= file_cost + 1;
fraction[0] = ap;
fraction[1] = fp;
denominator = ap + fp;
out:
trace_android_vh_tune_scan_type((char *)(&scan_balance));
trace_android_vh_tune_memcg_scan_type(memcg, (char *)(&scan_balance));
for_each_evictable_lru(lru) {
int file = is_file_lru(lru);
unsigned long lruvec_size;
unsigned long low, min;
unsigned long scan;
lruvec_size = lruvec_lru_size(lruvec, lru, sc->reclaim_idx);
mem_cgroup_protection(sc->target_mem_cgroup, memcg,
&min, &low);
if (min || low) {
/*
* Scale a cgroup's reclaim pressure by proportioning
* its current usage to its memory.low or memory.min
* setting.
*
* This is important, as otherwise scanning aggression
* becomes extremely binary -- from nothing as we
* approach the memory protection threshold, to totally
* nominal as we exceed it. This results in requiring
* setting extremely liberal protection thresholds. It
* also means we simply get no protection at all if we
* set it too low, which is not ideal.
*
* If there is any protection in place, we reduce scan
* pressure by how much of the total memory used is
* within protection thresholds.
*
* There is one special case: in the first reclaim pass,
* we skip over all groups that are within their low
* protection. If that fails to reclaim enough pages to
* satisfy the reclaim goal, we come back and override
* the best-effort low protection. However, we still
* ideally want to honor how well-behaved groups are in
* that case instead of simply punishing them all
* equally. As such, we reclaim them based on how much
* memory they are using, reducing the scan pressure
* again by how much of the total memory used is under
* hard protection.
*/
unsigned long cgroup_size = mem_cgroup_size(memcg);
unsigned long protection;
/* memory.low scaling, make sure we retry before OOM */
if (!sc->memcg_low_reclaim && low > min) {
protection = low;
sc->memcg_low_skipped = 1;
} else {
protection = min;
}
/* Avoid TOCTOU with earlier protection check */
cgroup_size = max(cgroup_size, protection);
scan = lruvec_size - lruvec_size * protection /
(cgroup_size + 1);
/*
* Minimally target SWAP_CLUSTER_MAX pages to keep
* reclaim moving forwards, avoiding decrementing
* sc->priority further than desirable.
*/
scan = max(scan, SWAP_CLUSTER_MAX);
} else {
scan = lruvec_size;
}
scan >>= sc->priority;
/*
* If the cgroup's already been deleted, make sure to
* scrape out the remaining cache.
*/
if (!scan && !mem_cgroup_online(memcg))
scan = min(lruvec_size, SWAP_CLUSTER_MAX);
switch (scan_balance) {
case SCAN_EQUAL:
/* Scan lists relative to size */
break;
case SCAN_FRACT:
/*
* Scan types proportional to swappiness and
* their relative recent reclaim efficiency.
* Make sure we don't miss the last page on
* the offlined memory cgroups because of a
* round-off error.
*/
scan = mem_cgroup_online(memcg) ?
div64_u64(scan * fraction[file], denominator) :
DIV64_U64_ROUND_UP(scan * fraction[file],
denominator);
break;
case SCAN_FILE:
case SCAN_ANON:
/* Scan one type exclusively */
if ((scan_balance == SCAN_FILE) != file)
scan = 0;
break;
default:
/* Look ma, no brain */
BUG();
}
nr[lru] = scan;
}
}
/*
* Anonymous LRU management is a waste if there is
* ultimately no way to reclaim the memory.
*/
static bool can_age_anon_pages(struct pglist_data *pgdat,
struct scan_control *sc)
{
/* Aging the anon LRU is valuable if swap is present: */
if (total_swap_pages > 0)
return true;
/* Also valuable if anon pages can be demoted: */
return can_demote(pgdat->node_id, sc);
}
#ifdef CONFIG_LRU_GEN
#ifdef CONFIG_LRU_GEN_ENABLED
DEFINE_STATIC_KEY_ARRAY_TRUE(lru_gen_caps, NR_LRU_GEN_CAPS);
#else
DEFINE_STATIC_KEY_ARRAY_FALSE(lru_gen_caps, NR_LRU_GEN_CAPS);
#endif
/******************************************************************************
* shorthand helpers
******************************************************************************/
#define DEFINE_MAX_SEQ(lruvec) \
unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq)
#define DEFINE_MIN_SEQ(lruvec) \
unsigned long min_seq[ANON_AND_FILE] = { \
READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_ANON]), \
READ_ONCE((lruvec)->lrugen.min_seq[LRU_GEN_FILE]), \
}
#define for_each_gen_type_zone(gen, type, zone) \
for ((gen) = 0; (gen) < MAX_NR_GENS; (gen)++) \
for ((type) = 0; (type) < ANON_AND_FILE; (type)++) \
for ((zone) = 0; (zone) < MAX_NR_ZONES; (zone)++)
static int page_lru_gen(struct page *page)
{
unsigned long flags = READ_ONCE(page->flags);
return ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
}
static int page_lru_tier(struct page *page)
{
int refs;
unsigned long flags = READ_ONCE(page->flags);
refs = (flags & LRU_REFS_FLAGS) == LRU_REFS_FLAGS ?
((flags & LRU_REFS_MASK) >> LRU_REFS_PGOFF) + 1 : 0;
return lru_tier_from_refs(refs);
}
static bool get_cap(int cap)
{
#ifdef CONFIG_LRU_GEN_ENABLED
return static_branch_likely(&lru_gen_caps[cap]);
#else
return static_branch_unlikely(&lru_gen_caps[cap]);
#endif
}
static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
{
struct pglist_data *pgdat = NODE_DATA(nid);
#ifdef CONFIG_MEMCG
if (memcg) {
struct lruvec *lruvec = &memcg->nodeinfo[nid]->lruvec;
/* for hotadd_new_pgdat() */
if (!lruvec->pgdat)
lruvec->pgdat = pgdat;
return lruvec;
}
#endif
VM_BUG_ON(!mem_cgroup_disabled());
return pgdat ? &pgdat->__lruvec : NULL;
}
static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
{
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
if (!can_demote(pgdat->node_id, sc) &&
mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
return 0;
return mem_cgroup_swappiness(memcg);
}
static int get_nr_gens(struct lruvec *lruvec, int type)
{
return lruvec->lrugen.max_seq - lruvec->lrugen.min_seq[type] + 1;
}
static bool __maybe_unused seq_is_valid(struct lruvec *lruvec)
{
/* see the comment on lru_gen_struct */
return get_nr_gens(lruvec, LRU_GEN_FILE) >= MIN_NR_GENS &&
get_nr_gens(lruvec, LRU_GEN_FILE) <= get_nr_gens(lruvec, LRU_GEN_ANON) &&
get_nr_gens(lruvec, LRU_GEN_ANON) <= MAX_NR_GENS;
}
/******************************************************************************
* mm_struct list
******************************************************************************/
static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
{
static struct lru_gen_mm_list mm_list = {
.fifo = LIST_HEAD_INIT(mm_list.fifo),
.lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
};
#ifdef CONFIG_MEMCG
if (memcg)
return &memcg->mm_list;
#endif
VM_BUG_ON(!mem_cgroup_disabled());
return &mm_list;
}
void lru_gen_add_mm(struct mm_struct *mm)
{
int nid;
struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
VM_BUG_ON_MM(!list_empty(&mm->lru_gen.list), mm);
#ifdef CONFIG_MEMCG
VM_BUG_ON_MM(mm->lru_gen.memcg, mm);
mm->lru_gen.memcg = memcg;
#endif
spin_lock(&mm_list->lock);
for_each_node_state(nid, N_MEMORY) {
struct lruvec *lruvec = get_lruvec(memcg, nid);
if (!lruvec)
continue;
if (lruvec->mm_state.tail == &mm_list->fifo)
lruvec->mm_state.tail = &mm->lru_gen.list;
}
list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
spin_unlock(&mm_list->lock);
}
void lru_gen_del_mm(struct mm_struct *mm)
{
int nid;
struct lru_gen_mm_list *mm_list;
struct mem_cgroup *memcg = NULL;
if (list_empty(&mm->lru_gen.list))
return;
#ifdef CONFIG_MEMCG
memcg = mm->lru_gen.memcg;
#endif
mm_list = get_mm_list(memcg);
spin_lock(&mm_list->lock);
for_each_node(nid) {
struct lruvec *lruvec = get_lruvec(memcg, nid);
if (!lruvec)
continue;
if (lruvec->mm_state.tail == &mm->lru_gen.list)
lruvec->mm_state.tail = lruvec->mm_state.tail->next;
if (lruvec->mm_state.head != &mm->lru_gen.list)
continue;
lruvec->mm_state.head = lruvec->mm_state.head->next;
if (lruvec->mm_state.head == &mm_list->fifo)
WRITE_ONCE(lruvec->mm_state.seq, lruvec->mm_state.seq + 1);
}
list_del_init(&mm->lru_gen.list);
spin_unlock(&mm_list->lock);
#ifdef CONFIG_MEMCG
mem_cgroup_put(mm->lru_gen.memcg);
mm->lru_gen.memcg = NULL;
#endif
}
#ifdef CONFIG_MEMCG
void lru_gen_migrate_mm(struct mm_struct *mm)
{
struct mem_cgroup *memcg;
lockdep_assert_held(&mm->owner->alloc_lock);
/* for mm_update_next_owner() */
if (mem_cgroup_disabled())
return;
rcu_read_lock();
memcg = mem_cgroup_from_task(mm->owner);
rcu_read_unlock();
if (memcg == mm->lru_gen.memcg)
return;
VM_BUG_ON_MM(!mm->lru_gen.memcg, mm);
VM_BUG_ON_MM(list_empty(&mm->lru_gen.list), mm);
lru_gen_del_mm(mm);
lru_gen_add_mm(mm);
}
#endif
/*
* Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
* n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
* bits in a bitmap, k is the number of hash functions and n is the number of
* inserted items.
*
* Page table walkers use one of the two filters to reduce their search space.
* To get rid of non-leaf entries that no longer have enough leaf entries, the
* aging uses the double-buffering technique to flip to the other filter each
* time it produces a new generation. For non-leaf entries that have enough
* leaf entries, the aging carries them over to the next generation in
* walk_pmd_range(); the eviction also report them when walking the rmap
* in lru_gen_look_around().
*
* For future optimizations:
* 1. It's not necessary to keep both filters all the time. The spare one can be
* freed after the RCU grace period and reallocated if needed again.
* 2. And when reallocating, it's worth scaling its size according to the number
* of inserted entries in the other filter, to reduce the memory overhead on
* small systems and false positives on large systems.
* 3. Jenkins' hash function is an alternative to Knuth's.
*/
#define BLOOM_FILTER_SHIFT 15
static inline int filter_gen_from_seq(unsigned long seq)
{
return seq % NR_BLOOM_FILTERS;
}
static void get_item_key(void *item, int *key)
{
u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
key[1] = hash >> BLOOM_FILTER_SHIFT;
}
static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq)
{
unsigned long *filter;
int gen = filter_gen_from_seq(seq);
lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
filter = lruvec->mm_state.filters[gen];
if (filter) {
bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
return;
}
filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT), GFP_ATOMIC);
WRITE_ONCE(lruvec->mm_state.filters[gen], filter);
}
static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
{
int key[2];
unsigned long *filter;
int gen = filter_gen_from_seq(seq);
filter = READ_ONCE(lruvec->mm_state.filters[gen]);
if (!filter)
return;
get_item_key(item, key);
if (!test_bit(key[0], filter))
set_bit(key[0], filter);
if (!test_bit(key[1], filter))
set_bit(key[1], filter);
}
static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
{
int key[2];
unsigned long *filter;
int gen = filter_gen_from_seq(seq);
filter = READ_ONCE(lruvec->mm_state.filters[gen]);
if (!filter)
return true;
get_item_key(item, key);
return test_bit(key[0], filter) && test_bit(key[1], filter);
}
static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
{
int i;
int hist;
lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
if (walk) {
hist = lru_hist_from_seq(walk->max_seq);
for (i = 0; i < NR_MM_STATS; i++) {
WRITE_ONCE(lruvec->mm_state.stats[hist][i],
lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]);
walk->mm_stats[i] = 0;
}
}
if (NR_HIST_GENS > 1 && last) {
hist = lru_hist_from_seq(lruvec->mm_state.seq + 1);
for (i = 0; i < NR_MM_STATS; i++)
WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0);
}
}
static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
{
int type;
unsigned long size = 0;
struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
if (!walk->full_scan && cpumask_empty(mm_cpumask(mm)) &&
!node_isset(pgdat->node_id, mm->lru_gen.nodes))
return true;
node_clear(pgdat->node_id, mm->lru_gen.nodes);
for (type = !walk->can_swap; type < ANON_AND_FILE; type++) {
size += type ? get_mm_counter(mm, MM_FILEPAGES) :
get_mm_counter(mm, MM_ANONPAGES) +
get_mm_counter(mm, MM_SHMEMPAGES);
}
if (size < MIN_LRU_BATCH)
return true;
if (mm_is_oom_victim(mm))
return true;
return !mmget_not_zero(mm);
}