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/[email protected]
Fixes: 2d146aa ("mm: memcontrol: switch to rstat")
Signed-off-by: Shakeel Butt <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Tejun Heo <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: shakeelb

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);