mm: writeback: ratelimit stat flush from mem_cgroup_wb_stats

One of our workloads (Postgres 14) has regressed when migrated from 5.10
to 6.1 upstream kernel.  The regression can be reproduced by sysbench's
oltp_write_only benchmark.  It seems like the always on rstat flush in
mem_cgroup_wb_stats() is causing the regression.  So, rate limit that
specific rstat flush.  One potential consequence would be the dirty
throttling might be decided on stale memcg stats.  However from our
benchmarks and production traffic we have not observed any change in the
dirty throttling behavior of the application.

Link: https://lkml.kernel.org/r/20240118184235.618164-1-shakeelb@google.com
Fixes: 2d146aa3aa84 ("mm: memcontrol: switch to rstat")
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index db92401257f7d00c4b862016cd7f7e49986f1f0e..df11d6d19ee38f97ee96062207cb5956b9ca2f39 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4800,7 +4800,7 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,
        struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);
        struct mem_cgroup *parent;
 
-       mem_cgroup_flush_stats(memcg);
+       mem_cgroup_flush_stats_ratelimited(memcg);
 
        *pdirty = memcg_page_state(memcg, NR_FILE_DIRTY);
        *pwriteback = memcg_page_state(memcg, NR_WRITEBACK);