Re: [PATCH v2 8/8] mm: Centralize & improve oom reporting in show_mem.c

Kent Overstreet
2022-04-23T00:46:16Z

On Fri, Apr 22, 2022 at 05:27:41PM -0700, Roman Gushchin wrote:
> You're scanning over a small portion of all shrinker lists (on a machine with
> cgroups), so the top-10 list has little value.
> Global ->count_objects() return the number of objects on the system/root_mem_cgroup
> level, not the shrinker's total.

Not quite following what you're saying here...?

If you're complaining that my current top-10-shrinker report isn't memcg aware,
that's valid - I can fix that.

> > In my experience, it's rare to be _so_ out of memory that small kmalloc
> > allocations are failing - we'll be triggering the show_mem() report before that
> > happens.
>
> I agree. However the OOM killer _has_ to make the progress even in such rare
> circumstances.

Oh, and the concern is allocator recursion? Yeah, that's a good point.

Do you know if using memalloc_noreclaim_(save|restore) is sufficient for that,
or do we want GFP_ATOMIC? I'm already using GFP_ATOMIC for allocations when we
generate the report on slabs, since we're taking the slab mutex there.