Re: [PATCH] mm, memcg: skip killing processes under memcg protection at first scan

[Yafang Shao <laoar.shao@gmail.com>]

On Mon, Aug 19, 2019 at 3:31 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Sun 18-08-19 00:24:54, Yafang Shao wrote:
> > In the current memory.min design, the system is going to do OOM instead
> > of reclaiming the reclaimable pages protected by memory.min if the
> > system is lack of free memory. While under this condition, the OOM
> > killer may kill the processes in the memcg protected by memory.min.
>
> Could you be more specific about the configuration that leads to this
> situation?

When I did memory pressure test to verify memory.min I found that issue.
This issue can be produced as bellow,
    memcg setting,
        memory.max: 1G
        memory.min: 512M
        some processes are running is this memcg, with both serveral
hundreds MB  file mapping and serveral hundreds MB anon mapping.
    system setting,
         swap: off.
         some memory pressure test are running on the system.

When the memory usage of this memcg is bellow the memory.min, the
global reclaimers stop reclaiming pages in this memcg, and when
there's no available memory, the OOM killer will be invoked.
Unfortunately the OOM killer can chose the process running in the
protected memcg.

In order to produce it easy, you can incease the memroy.min and set
-1000 to the oom_socre_adj of the processes outside of the protected
memcg.

Is this setting proper ?

Thanks
Yafang