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Date:   Fri, 20 May 2022 10:24:06 +0300
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Subject: Re: [PATCH 3/4] memcg: enable accounting for struct cgroup
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To:     =?UTF-8?Q?Michal_Koutn=c3=bd?= <mkoutny@suse.com>
Cc:     Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>, kernel@openvz.org,
        linux-kernel@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>, cgroups@vger.kernel.org
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 <20220519165325.GA2434@blackbody.suse.cz>
From:   Vasily Averin <vvs@openvz.org>
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On 5/19/22 19:53, Michal Koutný wrote:
> On Fri, May 13, 2022 at 06:52:12PM +0300, Vasily Averin <vvs@openvz.org> wrote:
>> Creating each new cgroup allocates 4Kb for struct cgroup. This is the
>> largest memory allocation in this scenario and is epecially important
>> for small VMs with 1-2 CPUs.
> 
> What do you mean by this argument?
> 
> (On bigger irons, the percpu components becomes dominant, e.g. struct
> cgroup_rstat_cpu.)

Michal, Shakeel,
thank you very much for your feedback, it helps me understand how to improve
the methodology of my accounting analyze.
I considered the general case and looked for places of maximum memory allocations.
Now I think it would be better to split all called allocations into:
- common part, called for any cgroup type (i.e. cgroup_mkdir and cgroup_create),
- per-cgroup parts,
and focus on 2 corner cases: for single CPU VMs and for "big irons".
It helps to clarify which allocations are accounting-important and which ones
can be safely ignored.

So right now I'm going to redo the calculations and hope it doesn't take long.

Thank you,
	Vasily Averin