On Fri, Nov 19, 2021 at 08:50:08PM -0800, Mina Almasry wrote:

On remote ooms (OOMs due to remote charging), the oom-killer will attempt
to find a task to kill in the memcg under oom. The oom-killer may be
unable to find a process to kill if there are no killable processes in
the remote memcg. In this case, the oom-killer (out_of_memory()) will return
false, and depending on the gfp, that will generally get bubbled up to
mem_cgroup_charge_mapping() as an ENOMEM.

Why doesn't it try to run the shrinkers to get back some page cache /
slab cache memory from this memcg?  I understand it might not be able
to (eg if the memory is mlocked), but surely that's rare.