Re: Backport memcg flush improvements into 5.15

[Shakeel Butt <shakeelb@google.com>]

+Andrew & linux-mm

On Thu, Jan 27, 2022 at 7:30 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Jan 19, 2022 at 04:15:34PM -0800, Ivan Babrou wrote:
> > Hello,
> >
> > We've seen a significant perf degradation when reading a tmpfs file
> > swapped into zram between 5.10 and 5.15. The source of the issue is:
> >
> > * aa48e47e3906: memcg: infrastructure to flush memcg stats
> >
> > There's a couple of commits that helps to bridge the gap in 5.16:
> >
> > * 11192d9c124d: memcg: flush stats only if updated
> > * fd25a9e0e23b: memcg: unify memcg stat flushing
> >
> > Both of these apply cleanly and Shakeel (the author) has okayed the
> > backport from his end. He also suggested backporting the following:
> >
> > * 5b3be698a872: memcg: better bounds on the memcg stats updates
> >
> > I personally did not test this one, but it applies cleanly, so there's
> > probably no harm. I cc'd Shakeel in case you want confirmation on
> > that. It's not a part of any tag yet.
> >
> > Please backport all three (or at least the first two) to 5.15 LTS.
>
> All now queued up, thanks!

Thanks Greg.

Adding Andrew (and linux-mm) in CC to let him know the reason for
backporting these patches to 5.15 stable tree.

>
> greg k-h