Re: [PATCH] mm, memcg: Report number of memcg caches in slabinfo

[Waiman Long]

On 6/17/19 10:38 AM, Michal Hocko wrote:
> [Cc linux-api]
>
> On Mon 17-06-19 10:21:49, Waiman Long wrote:
>> There are concerns about memory leaks from extensive use of memory
>> cgroups as each memory cgroup creates its own set of kmem caches. There
>> is a possiblity that the memcg kmem caches may remain even after the
>> memory cgroup removal.
>>
>> Therefore, it will be useful to show how many memcg caches are present
>> for each of the kmem caches.
> How is a user going to use that information?  Btw. Don't we have an
> interface to display the number of (dead) cgroups?

The interface to report dead cgroups is for cgroup v2 (cgroup.stat)
only. I don't think there is a way to find that for cgroup v1. Also the
number of memcg kmem caches may not be the same as the number of
memcg's. It can range from 0 to above the number of memcg's. So it is
an interesting number by itself.

>From the user perspective, if the numbers is way above the number of
memcg's, there is probably something wrong there.

Cheers,
Longman