Re: [Patch v2 3/3] mm/memcg: add next_mz back to soft limit tree if not reclaimed yet

[Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>]

On Mon 14-03-22 23:05:48, Wei Yang wrote:
> On Mon, Mar 14, 2022 at 10:41:13AM +0100, Michal Hocko wrote:
> >On Sat 12-03-22 07:16:23, Wei Yang wrote:
> >> When memory reclaim failed for a maximum number of attempts and we bail
> >> out of the reclaim loop, we forgot to put the target mem_cgroup chosen
> >> for next reclaim back to the soft limit tree. This prevented pages in
> >> the mem_cgroup from being reclaimed in the future even though the
> >> mem_cgroup exceeded its soft limit.
> >> 
> >> Let's say there are two mem_cgroup and both of them exceed the soft
> >> limit, while the first one is more active then the second. Since we add
> >> a mem_cgroup to soft limit tree every 1024 event, the second one just
> >> get a rare chance to be put on soft limit tree even it exceeds the
> >> limit.
> >
> >yes, 1024 could be just 4MB of memory or 2GB if all the charged pages
> >are THPs. So the excess can build up considerably.
> >
> >> As time goes on, the first mem_cgroup was kept close to its soft limit
> >> due to reclaim activities, while the memory usage of the second
> >> mem_cgroup keeps growing over the soft limit for a long time due to its
> >> relatively rare occurrence.
> >> 
> >> This patch adds next_mz back to prevent this sceanrio.
> >> 
> >> Signed-off-by: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> >
> >Even though your changelog is different the change itself is identical to
> >https://lore.kernel.org/linux-mm/8d35206601ccf0e1fe021d24405b2a0c2f4e052f.1613584277.git.tim.c.chen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org/
> >In those cases I would preserve the the original authorship by
> >From: Tim Chen <tim.c.chen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> >and add his s-o-b before yours.
> 
> TBH I don't think this is fair.
> 
> I didn't see his original change before I sent this patch. This is a
> coincidence we found the same point for improvement.
> 
> It hurts me if you want to change authorship. Well, if you really thinks this
> is what it should be, please remove my s-o-b.

OK, fair enough.
-- 
Michal Hocko
SUSE Labs