On Fri 30-08-24 01:06:44, Liu Jing wrote:
> hello，linux boss
>
> I found a problem in the process of using linux memcg，When I turned swap off, the memcg memory I created with the following script could not be deleted with echo 0 > memory.force_empty, as explained below。
>
> ----------------------------------------------------------------------------------------------------------
> step1：swapoff -a
>
>
> step2：use this script to create memcg
>
> #!/bin/bash
> mkdir -p /tmp/test
> for i in 'seq 2000'
> do
> sudo mkdir -p /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}
> sudo echo $$ > /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}/tasks
> sudo echo 'data' > /tmp/test/test$ {i}
> sudo echo $$ > /sys/fs/cgroup/memory/user.slice/user-0.slice/tasks
> sudo rmdir /sys/fs/cgroup/memory/user.slice/user-0.slice/test$ {i}
> done
[...]
I assume you /tmp is tmpfs backed.
> Therefore, I want to know why swap affects memcg memory reclamation,
> echo 0 > memory.force_empty this interface should force the memory
> used by the cgroup to be reclaimed.
If the above is true then you simply do not have any backing storage to
reclaim to. You need swap to reclaim tmpfs/shmem memory.
--
Michal Hocko
SUSE Labs
