Re: [PATCH] cgroup: wait for css offline when rmdir

[Hongchen Zhang]

On 2022/5/31 上午9:01, Tejun Heo wrote:
> Hello,
>
> On Mon, May 30, 2022 at 09:53:51AM +0800, Hongchen Zhang wrote:
> >    When I test the LTP's memcg_test_3 testcase at 8 Node server,I get the
> > -ENOMEM error,which caused by no avaliable idr found in mem_cgroup_idr.
> > the reason is the use of idr in mem_cgroup_idr is too fast than the free.In
> > the specific case,the idr is used and freed cyclically,so when we rmdir one
> > cgroup dir, we can synchronize the idr free through wating for the memcg css
> > offlined,and then we can use it the next cycle.
>
> This is a micro benchmark specific problem and it doesn't make sense to
> change the overall behavior for this as the suggested change is neither
> desirable or logical. Maybe you can just incur the delay only after idr
> allocation fails and then retry?
>
> Thanks.
Hi Tejun,

Yes, the problem would disappear when add some reasonable delay. But I 
think if we can increase the MEM_CGROUP_ID_MAX to INT_MAX.Thus the 
-ENOMEM error would be never occured,even if the system is out of memory.

Thanks.