On Mon, Jan 22, 2024 at 7:20 AM Michal Koutný [off-list ref] wrote:

Hello.

On Thu, Jan 18, 2024 at 06:42:35PM +0000, Shakeel Butt [off-list ref] wrote:

quoted

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).

Yes, the benchmark and the workload were running in non-root cgroups.

Regarding the Fixes, please note that the regression was still there
with 7d7ef0a4686a ("mm: memcg: restore subtree stats flushing"), so I
would say that our first conversion to rstat infra would most probably
have the issue as well which was 2d146aa3aa84 ("mm: memcontrol: switch
to rstat").

So, the following fixes tag makes sense to me:

Fixes: 2d146aa3aa84 ("mm: memcontrol: switch to rstat")