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Date:   Thu, 30 Mar 2023 19:18:00 +0000
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Subject: [PATCH v3 7/8] vmscan: memcg: sleep when flushing stats during reclaim
From:   Yosry Ahmed <yosryahmed@google.com>
To:     Tejun Heo <tj@kernel.org>, Josef Bacik <josef@toxicpanda.com>,
        Jens Axboe <axboe@kernel.dk>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>,
        "=?UTF-8?q?Michal=20Koutn=C3=BD?=" <mkoutny@suse.com>
Cc:     Vasily Averin <vasily.averin@linux.dev>, cgroups@vger.kernel.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, bpf@vger.kernel.org,
        Yosry Ahmed <yosryahmed@google.com>,
        Michal Hocko <mhocko@suse.com>
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Precedence: bulk

Memory reclaim is a sleepable context. Flushing is an expensive
operaiton that scales with the number of cpus and the number of cgroups
in the system, so avoid doing it atomically unnecessarily.
This can slow down reclaim code if flushing stats is taking too long,
but there is already multiple cond_resched()'s in reclaim code.

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>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a9511ccb936f..9c1c5e8b24b8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, struct scan_control *sc)
 	 * Flush the memory cgroup stats, so that we read accurate per-memcg
 	 * lruvec stats for heuristics.
 	 */
-	mem_cgroup_flush_stats_atomic();
+	mem_cgroup_flush_stats();
 
 	/*
 	 * Determine the scan balance between anon and file LRUs.
-- 
2.40.0.348.gf938b09366-goog