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Date:   Sun, 22 May 2022 14:37:14 +0800
From:   Muchun Song <songmuchun@bytedance.com>
To:     Vasily Averin <vvs@openvz.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>, kernel@openvz.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Shakeel Butt <shakeelb@google.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>, cgroups@vger.kernel.org
Subject: Re: [PATCH mm v2 1/9] memcg: enable accounting for struct cgroup
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 <a76dc143-68d9-41f4-81d1-85ec15135b1e@openvz.org>
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On Sat, May 21, 2022 at 07:37:36PM +0300, Vasily Averin 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.
> 
> Common part of the cgroup creation:
> Allocs  Alloc   $1*$2   Sum     Allocation
> number  size
> --------------------------------------------
> 16  ~   352     5632    5632    KERNFS
> 1   +   4096    4096    9728    (cgroup_mkdir+0xe4)
> 1       584     584     10312   (radix_tree_node_alloc.constprop.0+0x89)
> 1       192     192     10504   (__d_alloc+0x29)
> 2       72      144     10648   (avc_alloc_node+0x27)
> 2       64      128     10776   (percpu_ref_init+0x6a)
> 1       64      64      10840   (memcg_list_lru_alloc+0x21a)
> percpu:
> 1   +   192     192     192     call_site=psi_cgroup_alloc+0x1e
> 1   +   96      96      288     call_site=cgroup_rstat_init+0x5f
> 2       12      24      312     call_site=percpu_ref_init+0x23
> 1       6       6       318     call_site=__percpu_counter_init+0x22
> 
>  '+' -- to be accounted,
>  '~' -- partially accounted
> 
> Accounting of this memory helps to avoid misuse inside memcg-limited
> containers.
> 
> Signed-off-by: Vasily Averin <vvs@openvz.org>

Reviewed-by: Muchun Song <songmuchun@bytedance.com>