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Date:   Thu, 23 Mar 2023 04:00:35 +0000
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Subject: [RFC PATCH 5/7] 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>
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>
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Precedence: bulk

Memory reclaim should be a sleepable context. Allow sleeping when
flushing memcg stats to avoid unnecessarily performing a lot of work
without sleeping. 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>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 59d1830d08ac..bae35cfb33c8 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(false);
+	mem_cgroup_flush_stats(true);
 
 	/*
 	 * Determine the scan balance between anon and file LRUs.
-- 
2.40.0.rc1.284.g88254d51c5-goog