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

Wei Yang
2022-03-10T23:55:15Z

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@gmail.com]
>>
>> 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@linux.intel.com/
>
>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