linux-kernel - Re: [PATCH 5/9] memcg: no refilling stock from obj_cgroup

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Message-ID: <Z9jHCaydxKBnOKEQ@google.com>
Date: Tue, 18 Mar 2025 01:06:17 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-mm@...ck.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH 5/9] memcg: no refilling stock from obj_cgroup_release

On Sat, Mar 15, 2025 at 10:49:26AM -0700, Shakeel Butt wrote:
> obj_cgroup_release is called when all the references to the objcg have
> been released i.e. no more memory objects are pointing to it. Most
> probably objcg->memcg will be pointing to some ancestor memcg. In
> obj_cgroup_release(), the kernel calls obj_cgroup_uncharge_pages() which
> refills the local stock.
> 
> There is no need to refill the local stock with some ancestor memcg and
> flush the local stock. Let's decouple obj_cgroup_release() from the
> local stock by uncharging instead of refilling. One additional benefit
> of this change is that it removes the requirement to only call
> obj_cgroup_put() outside of local_lock.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>