diff mbox series

mm: writeback: ratelimit stat flush from mem_cgroup_wb_stats

Message ID 20240118184235.618164-1-shakeelb@google.com
State New
Headers
Series mm: writeback: ratelimit stat flush from mem_cgroup_wb_stats |

Commit Message

Shakeel Butt Jan. 18, 2024, 6:42 p.m. UTC 
  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.

Signed-off-by: Shakeel Butt <shakeelb@google.com>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Michal Koutný Jan. 22, 2024, 3:20 p.m. UTC | #1 
Hello.

On Thu, Jan 18, 2024 at 06:42:35PM +0000, Shakeel Butt <shakeelb@google.com> wrote:
> 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.

Is the affected benchmark running in a non-root cgroup?

I'm asking whether this would warrant a 
  Fixes: fd25a9e0e23b ("memcg: unify memcg stat flushing") 
that introduced the global flush (in v6.1) but it was removed later in 
  7d7ef0a4686a ("mm: memcg: restore subtree stats flushing") 
(so v6.8 could be possibly unaffected).

Thanks,
Michal
diff mbox series

Patch

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 935f48c4d399..2474c8382e6f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4776,7 +4776,7 @@  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);