Re: [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root

[Roman Gushchin]

On Tue, Oct 20, 2020 at 02:18:22PM -0400, Johannes Weiner wrote:
> On Tue, Oct 20, 2020 at 10:07:17AM -0700, Roman Gushchin wrote:
> > If we want these counter to function properly, then we should go into the opposite
> > direction and remove the special handling of the root memory cgroup in many places.
> 
> I suspect this is also by far the most robust solution from a code and
> maintenance POV.
> 
> I don't recall the page counter at the root level having been a
> concern in recent years, even though it's widely used in production
> environments. It's lockless and cache compact. It's also per-cpu
> batched, which means it isn't actually part of the memcg hotpath.


I agree.

Here is my first attempt. Comments are welcome!

It doesn't solve the original problem though (use_hierarchy == false and
objcg reparenting), I'll send a separate patch for that.

Thanks!

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