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workingset: memcg: sleep when flushing stats in workingset_refault() 

In workingset_refault(), we call
mem_cgroup_flush_stats_atomic_ratelimited() to read accurate stats within
an RCU read section and with sleeping disallowed.  Move the call above the
RCU read section to make it non-atomic.

Flushing is an expensive operation that scales with the number of cpus and
the number of cgroups in the system, so avoid doing it atomically where
possible.

Since workingset_refault() is the only caller of
mem_cgroup_flush_stats_atomic_ratelimited(), just make it non-atomic, and
rename it to mem_cgroup_flush_stats_ratelimited().

Link: https://lkml.kernel.org/r/20230330191801.1967435-7-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vasily Averin <vasily.averin@linux.dev>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yosry Ahmed 2023-03-30 19:17:59 +00:00 committed by Andrew Morton
parent 9fad9aee1f
commit 4009b2f188
3 changed files with 7 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/memcontrol.h
View File

@ -1039,7 +1039,7 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec,
void mem_cgroup_flush_stats(void);
void mem_cgroup_flush_stats_atomic(void);
void mem_cgroup_flush_stats_atomic_ratelimited(void);
void mem_cgroup_flush_stats_ratelimited(void);
void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,
int val);
@ -1541,7 +1541,7 @@ static inline void mem_cgroup_flush_stats_atomic(void)
{
}
static inline void mem_cgroup_flush_stats_atomic_ratelimited(void)
static inline void mem_cgroup_flush_stats_ratelimited(void)
{
}

4
mm/memcontrol.c
View File

@ -674,10 +674,10 @@ void mem_cgroup_flush_stats_atomic(void)
do_flush_stats(true);
}
void mem_cgroup_flush_stats_atomic_ratelimited(void)
void mem_cgroup_flush_stats_ratelimited(void)
{
if (time_after64(jiffies_64, READ_ONCE(flush_next_time)))
mem_cgroup_flush_stats_atomic();
mem_cgroup_flush_stats();
}
static void flush_memcg_stats_dwork(struct work_struct *w)

5
mm/workingset.c
View File

@ -406,6 +406,9 @@ void workingset_refault(struct folio *folio, void *shadow)
unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset);
eviction <<= bucket_order;
/* Flush stats (and potentially sleep) before holding RCU read lock */
mem_cgroup_flush_stats_ratelimited();
rcu_read_lock();
/*
* Look up the memcg associated with the stored ID. It might
@ -461,8 +464,6 @@ void workingset_refault(struct folio *folio, void *shadow)
lruvec = mem_cgroup_lruvec(memcg, pgdat);
mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr);
mem_cgroup_flush_stats_atomic_ratelimited();
/*
* Compare the distance to the existing workingset size. We
* don't activate pages that couldn't stay resident even if