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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Muchun Song <muchun.song@linux.dev>,
	Vlastimil Babka <vbabka@suse.cz>, linux-mm@kvack.org,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	Meta kernel team <kernel-team@meta.com>
Subject: Re: [RFC PATCH 05/10] memcg: no refilling stock from
 obj_cgroup_release
Message-ID: <20250314112627.dPKeawXj@linutronix.de>
References: <20250314061511.1308152-1-shakeel.butt@linux.dev>
 <20250314061511.1308152-6-shakeel.butt@linux.dev>
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In-Reply-To: <20250314061511.1308152-6-shakeel.butt@linux.dev>

On 2025-03-13 23:15:06 [-0700], Shakeel Butt wrote:
> obj_cgroup_release is called when all the references to the objcg has

"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 and at the
> moment, in obj_cgroup_release, the kernel call
> obj_cgroup_uncharge_pages() to uncharge last remaining memory.

This sounds somehow funny. I think the point is to uncharge the pages
without tampering memcg_stock because it is unnecessary.

> However obj_cgroup_uncharge_pages() refills the local stock. There is
> no need to refill the local stock with some ancestor memcg and flush the
> local stock. In addition this removes the requirement to only call
> obj_cgroup_put() outside of local_lock.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>

Sebastian