Re: [PATCH v2] memcg: allow exiting tasks to write back data to swap

[Roman Gushchin]

On Thu, Dec 12, 2024 at 11:57:54AM -0500, Rik van Riel wrote:
> A task already in exit can get stuck trying to allocate pages, if its
> cgroup is at the memory.max limit, the cgroup is using zswap, but
> zswap writeback is enabled, and the remaining memory in the cgroup is
> not compressible.

Is it about a single task or groups of tasks or the entire cgroup?
If former, why it's a problem? A tight memcg limit can slow things down
in general and I don't see why we should treat the exit() path differently.

If it's about the entire cgroup and we have essentially a deadlock,
I feel like we need to look into the oom reaper side.

Alternatively we can allow to go over the limit in this case, but only
assuming all tasks in the cgroup are going to die and no new task can
enter it.

Thanks!