Re: [PATCH memcg v3 1/3] mm, oom: pagefault_out_of_memory: don't force global OOM for dying tasks

Michal Hocko
2021-10-25T09:27:29Z

On Sat 23-10-21 16:19:28, Vasily Averin wrote:
> Any allocation failure during the #PF path will return with VM_FAULT_OOM
> which in turn results in pagefault_out_of_memory which in own turn
> executes out_out_memory() and can kill a random task.
>
> An allocation might fail when the current task is the oom victim
> and there are no memory reserves left. The OOM killer is already
> handled at the page allocator level for the global OOM and at the
> charging level for the memcg one. Both have much more information
> about the scope of allocation/charge request. This means that
> either the OOM killer has been invoked properly and didn't lead
> to the allocation success or it has been skipped because it couldn't
> have been invoked. In both cases triggering it from here is pointless
> and even harmful.
>
> It makes much more sense to let the killed task die rather than to
> wake up an eternally hungry oom-killer and send him to choose a fatter
> victim for breakfast.
>
> Suggested-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
> Signed-off-by: Vasily Averin <vvs-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>

Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>

Thanks!

> ---
> mm/oom_kill.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 831340e7ad8b..1deef8c7a71b 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1137,6 +1137,9 @@ void pagefault_out_of_memory(void)
> if (mem_cgroup_oom_synchronize(true))
> return;
>
> + if (fatal_signal_pending(current))
> + return;
> +
> if (!mutex_trylock(&oom_lock))
> return;
> out_of_memory(&oc);
> --
> 2.32.0

--
Michal Hocko
SUSE Labs