Re: [PATCH] memcg: add tracing for memcg stat updates

Shakeel Butt
2024-10-10T17:27:29Z

On Thu, Oct 10, 2024 at 12:46:29AM GMT, Roman Gushchin wrote:
> On Wed, Oct 09, 2024 at 05:35:50PM -0700, Shakeel Butt wrote:
> > The memcg stats are maintained in rstat infrastructure which provides
> > very fast updates side and reasonable read side. However memcg added
> > plethora of stats and made the read side, which is cgroup rstat flush,
> > very slow. To solve that, threshold was added in the memcg stats read
> > side i.e. no need to flush the stats if updates are within the
> > threshold.
> >
> > This threshold based improvement worked for sometime but more stats were
> > added to memcg and also the read codepath was getting triggered in the
> > performance sensitive paths which made threshold based ratelimiting
> > ineffective. We need more visibility into the hot and cold stats i.e.
> > stats with a lot of updates. Let's add trace to get that visibility.
> >
> > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
>
> Acked-by: Roman Gushchin <roman.gushchin@linux.dev>

Thanks for the review.