Re: [PATCH] memcg: add support to generate the total count of children from root

[Aaron Tomlin]

On Tue, 24 Nov 2020 at 11:26, Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Tue 24-11-20 10:58:36, Aaron Tomlin wrote:
> > Each memory-controlled cgroup is assigned a unique ID and the total
> > number of memory cgroups is limited to MEM_CGROUP_ID_MAX.
> >
> > This patch provides the ability to determine the number of
> > memory cgroups from the root memory cgroup, only.
> > A value of 1 (i.e. self count) is returned if there are no children.
> > For example, the number of memory cgroups can be established by
> > reading the /sys/fs/cgroup/memory/memory.total_cnt file.
>

Hi Michal,

> Could you add some explanation why is this information useful for
> userspace? Who is going to use it and why a simple scripting on top of
> cgroupfs is insufficient.

Thank you for your feedback.

Indeed, one can use a command/script to manually calculate this.
Having said that, one that creates a significant number of
memory-controlled cgroups may prefer a quick, simple and reliable method
to generate the aforementioned data, for management purposes only.
As such, I thought this patch might be particularly useful.

Kind regards,
-- 
Aaron Tomlin