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Date:   Fri, 24 Jun 2022 14:26:10 +0200
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Vasily Averin <vvs@openvz.org>
Cc:     Shakeel Butt <shakeelb@google.com>, Michal Hocko <mhocko@suse.com>,
        kernel@openvz.org, Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Vlastimil Babka <vbabka@suse.cz>,
        Muchun Song <songmuchun@bytedance.com>,
        Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH mm v5 0/9] memcg: accounting for objects allocated by
 mkdir, cgroup
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On Fri, Jun 24, 2022 at 01:40:14PM +0300, Vasily Averin <vvs@openvz.org> wrote:
> Btw could you please explain why memory cgroups have MEM_CGROUP_ID_MAX limit
> Why it is required at all and why it was set to USHRT_MAX? I believe that
> in the future it may be really reachable:

IIRC, one reason is 2B * nr_swap_pages of memory overhead (in
swap_cgroup_swapon()) that's ~0.05% of swap space occupied additionally
in RAM (fortunately swap needn't cover whole RAM).

HTH,
Michal

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