[LTP] [PATCH v3] mm: memcg/slab: Stop reparented obj_cgroups from charging root

[Michal Koutný]

Hi.

On Tue, Oct 20, 2020 at 06:52:08AM +0100, Richard Palethorpe <rpalethorpe@suse.de> wrote:
> I don't think that is relevant as we get the memcg from objcg->memcg
> which is set during reparenting. I suppose however, we can determine if
> the objcg was reparented by inspecting memcg->objcg.
+1

> If we just check use_hierarchy then objects directly charged to the
> memcg where use_hierarchy=0 will not be uncharged. However, maybe it is
> better to check if it was reparented and if use_hierarchy=0.
I think (I had to make a table) the yielded condition would be:

if ((memcg->use_hierarchy && reparented) || (!mem_cgroup_is_root(memcg) && !reparented))
	 __memcg_kmem_uncharge(memcg, nr_pages);

(I admit it's not very readable.)


Michal
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