Re: [PATCH 3/3] mm/memcg: add next_mz back if not reclaimed yet

[Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Thu, Mar 10, 2022 at 09:59:30AM +0100, Michal Hocko wrote:
>On Wed 09-03-22 14:48:46, Michal Hocko wrote:
>> [Cc Tim - the patch is http://lkml.kernel.org/r/20220308012047.26638-3-richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org]
>> 
>> On Wed 09-03-22 00:46:20, Wei Yang wrote:
>> > On Tue, Mar 08, 2022 at 09:17:58AM +0100, Michal Hocko wrote:
>> > >On Tue 08-03-22 01:20:47, Wei Yang wrote:
>> > >> next_mz is removed from rb_tree, let's add it back if no reclaim has
>> > >> been tried.
>> > >
>> > >Could you elaborate more why we need/want this?
>> > >
>> > 
>> > Per my understanding, we add back the right most node even reclaim makes no
>> > progress, so it is reasonable to add back a node if we didn't get a chance to
>> > do reclaim on it.
>> 
>> Your patch sounded familiar and I can remember now. The same fix has
>> been posted by Tim last year
>> https://lore.kernel.org/linux-mm/8d35206601ccf0e1fe021d24405b2a0c2f4e052f.1613584277.git.tim.c.chen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org/
>
>Btw. I forgot to mention yesterday. Whatever was the reason this has
>slipped through cracks it would great if you could reuse the changelog
>of the original patch which was more verbose and explicit about the
>underlying problem. The only remaining part I would add is a description
>of how serious the problem is. The removed memcg would be out of the
>excess tree until further memory charges would get it back. But that can
>take arbitrary amount of time. Whether that is a real problem would
>depend on the workload of course but considering how coarse of a tool
>the soft limit is it is possible that this is not something most users
>would even notice.

Got it, would send a v2.

>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me