From: Michal Hocko <mhocko@suse.com>
To: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <guro@fb.com>, Yang Shi <shy828301@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: memcg: add swapcache stat for memcg v2
Date: Wed, 6 Jan 2021 15:53:49 +0100 [thread overview]
Message-ID: <20210106145349.GN13207@dhcp22.suse.cz> (raw)
In-Reply-To: <20210101023955.250965-1-shakeelb@google.com>
On Thu 31-12-20 18:39:55, Shakeel Butt wrote:
> This patch adds swapcache stat for the cgroup v2. The swapcache
> represents the memory that is accounted against both the memory and the
> swap limit of the cgroup. The main motivation behind exposing the
> swapcache stat is for enabling users to gracefully migrate from cgroup
> v1's memsw counter to cgroup v2's memory and swap counters.
>
> Cgroup v1's memsw limit allows users to limit the memory+swap usage of a
> workload but without control on the exact proportion of memory and swap.
> Cgroup v2 provides separate limits for memory and swap which enables
> more control on the exact usage of memory and swap individually for the
> workload.
>
> With some little subtleties, the v1's memsw limit can be switched with
> the sum of the v2's memory and swap limits. However the alternative for
> memsw usage is not yet available in cgroup v2. Exposing per-cgroup
> swapcache stat enables that alternative. Adding the memory usage and
> swap usage and subtracting the swapcache will approximate the memsw
> usage. This will help in the transparent migration of the workloads
> depending on memsw usage and limit to v2' memory and swap counters.
Could you expand a bit more on why memsw usage is important even in
cgroup v2 land? How are you going to use the approximated value?
I am not really objecting to adding this counter. We do export it for
the global case and having a memcg view sounds useful for analysis.
--
Michal Hocko
SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
To: Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>,
Yang Shi <shy828301-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] mm: memcg: add swapcache stat for memcg v2
Date: Wed, 6 Jan 2021 15:53:49 +0100 [thread overview]
Message-ID: <20210106145349.GN13207@dhcp22.suse.cz> (raw)
In-Reply-To: <20210101023955.250965-1-shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
On Thu 31-12-20 18:39:55, Shakeel Butt wrote:
> This patch adds swapcache stat for the cgroup v2. The swapcache
> represents the memory that is accounted against both the memory and the
> swap limit of the cgroup. The main motivation behind exposing the
> swapcache stat is for enabling users to gracefully migrate from cgroup
> v1's memsw counter to cgroup v2's memory and swap counters.
>
> Cgroup v1's memsw limit allows users to limit the memory+swap usage of a
> workload but without control on the exact proportion of memory and swap.
> Cgroup v2 provides separate limits for memory and swap which enables
> more control on the exact usage of memory and swap individually for the
> workload.
>
> With some little subtleties, the v1's memsw limit can be switched with
> the sum of the v2's memory and swap limits. However the alternative for
> memsw usage is not yet available in cgroup v2. Exposing per-cgroup
> swapcache stat enables that alternative. Adding the memory usage and
> swap usage and subtracting the swapcache will approximate the memsw
> usage. This will help in the transparent migration of the workloads
> depending on memsw usage and limit to v2' memory and swap counters.
Could you expand a bit more on why memsw usage is important even in
cgroup v2 land? How are you going to use the approximated value?
I am not really objecting to adding this counter. We do export it for
the global case and having a memcg view sounds useful for analysis.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-01-06 14:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-01 2:39 [PATCH] mm: memcg: add swapcache stat for memcg v2 Shakeel Butt
2021-01-01 2:39 ` Shakeel Butt
2021-01-01 2:39 ` Shakeel Butt
2021-01-06 14:53 ` Michal Hocko [this message]
2021-01-06 14:53 ` Michal Hocko
2021-01-06 16:42 ` Shakeel Butt
2021-01-06 16:42 ` Shakeel Butt
2021-01-06 16:42 ` Shakeel Butt
2021-01-08 13:24 ` Michal Hocko
2021-01-08 13:24 ` Michal Hocko
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