From 5795558d8600f37464d649c7c553d43d96fc1fd2 Mon Sep 17 00:00:00 2001
From: Yosry Ahmed <yosryahmed@google.com>
Date: Thu, 30 Mar 2023 19:18:00 +0000
Subject: [PATCH] UPSTREAM: vmscan: memcg: sleep when flushing stats during
 reclaim
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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.

Link: https://lkml.kernel.org/r/20230330191801.1967435-8-yosryahmed@google.com
Change-Id: Ia0f0d42131e67a060dc7c9b868ef5247d78e05c8
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>
(cherry picked from commit 0d856cfedd6bc0cb8e19c1e70d400e79b655cfdd)
Bug: 322544714
Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0861ef42b049..5e92c1061fe9 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2904,7 +2904,7 @@ 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.