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

Wei Yang
2022-03-10T23:57:33Z

On Thu, Mar 10, 2022 at 09:53:59AM +0100, Michal Hocko wrote:
>On Thu 10-03-22 01:13:50, Wei Yang wrote:
>> On Wed, Mar 09, 2022 at 02:48:45PM +0100, 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/
>> >It was posted with other changes to the soft limit code which I didn't
>> >like but I have acked this particular one. Not sure what has happened
>> >with it afterwards.
>>
>> Because of this ?
>> 4f09feb8bf: vm-scalability.throughput -4.3% regression
>> https://lore.kernel.org/linux-mm/20210302062521.GB23892@xsang-OptiPlex-9020/
>
>That was a regression for a different patch in the series AFAICS:
>: FYI, we noticed a -4.3% regression of vm-scalability.throughput due to commit:
>:
>: commit: 4f09feb8bf083be3834080ddf3782aee12a7c3f7 ("mm: Force update of mem cgroup soft limit tree on usage excess")
>
>That patch has played with how often memcg_check_events is called and
>that can lead to a visible performance difference.

Yes, I mean maybe because of this regression, the whole patch set is removed.

>--
>Michal Hocko
>SUSE Labs

--
Wei Yang
Help you, Help me