linux-kernel - Re: [PATCH v3] cpuset: Enable cpuset controller in default hierarchy

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Message-ID: <db119820-84d4-7ccb-e65a-966d2d7aaf02@redhat.com>
Date:   Wed, 25 Oct 2017 11:50:34 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-doc@...r.kernel.org, Mike Galbraith <efault@....de>,
        Christian Brauner <christian.brauner@...onical.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        Serge Hallyn <serge@...lyn.com>
Subject: Re: [PATCH v3] cpuset: Enable cpuset controller in default hierarchy

On 10/06/2017 05:10 PM, Waiman Long wrote:
> Given the fact that thread mode had been merged into 4.14, it is now
> time to enable cpuset to be used in the default hierarchy (cgroup v2)
> as it is clearly threaded.
>
> The cpuset controller had experienced feature creep since its
> introduction more than a decade ago. Besides the core cpus and mems
> control files to limit cpus and memory nodes, there are a bunch of
> additional features that can be controlled from the userspace. Some of
> the features are of doubtful usefulness and may not be actively used.
>
> After examining the source code of some sample users like systemd,
> libvirt and lxc for their use of those additional features, only
> memory_migrate is used by libvirt.
>
> This patch enables cpuset controller in the default hierarchy with a
> minimal set of features. Currently, only memory_migrate is supported.
> We can certainly add more features to the default hierarchy if there
> is a real user need for them later on.
>
> For features that are actually flags which are set internally, they are
> being combined into a single "cpuset.flags" control file. That includes
> the memory_migrate feature which is the only flag that is currently
> supported. When the "cpuset.flags" file is read, it contains either
> "+mem_migrate" (enabled) or "-mem_migrate" (disabled).
>
> To enable it, use
>
>   # echo +mem_migrate > cpuset.flags
>
> To disable it, use
>
>   # echo -mem_migrate > cpuset.flags
>
> Note that the flag name is changed to "mem_migrate" for better naming
> consistency.
>
> v3:
>  - Further trim the additional features down to just memory_migrate.
>  - Update Documentation/cgroup-v2.txt.
>
> Signed-off-by: Waiman Long <longman@...hat.com>

Ping! Any comment on this patch?

Cheers,
Longman