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From:   Roman Gushchin <roman.gushchin@linux.dev>
To:     Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
Cc:     Muchun Song <songmuchun@bytedance.com>, hannes@cmpxchg.org,
        mhocko@kernel.org, shakeelb@google.com, akpm@linux-foundation.org,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, duanxiongchun@bytedance.com,
        longman@redhat.com
Subject: Re: [PATCH v5 03/11] mm: memcontrol: prepare objcg API for non-kmem
 usage
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References: <20220530074919.46352-1-songmuchun@bytedance.com>
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 <20220601173434.GB16134@blackbody.suse.cz>
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On Wed, Jun 01, 2022 at 07:34:34PM +0200, Michal Koutny wrote:
> Hello.
> 
> On Mon, May 30, 2022 at 03:49:11PM +0800, Muchun Song <songmuchun@bytedance.com> wrote:
> > So we also allocate an object cgroup for the root_mem_cgroup.
> 
> This change made me wary that this patch also kmem charging in the
> root_mem_cgroup. Fortunately, get_obj_cgroup_from_current won't return
> this objcg so all is fine.

Yes, I had the same experience here :)

Overall I feel like the handling of the root memcg and objcg are begging
for a cleanup, but it's really far from being trivial.

Maybe starting with documenting how it works now is a good idea...