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

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Date:   Mon, 27 Nov 2017 13:04:11 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jonathan Corbet <corbet@....net>, 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

Hello, Waiman.

Sorry about the long delay.

On Fri, Oct 06, 2017 at 05:10:30PM -0400, Waiman Long wrote:
> +Cpuset Interface Files
> +~~~~~~~~~~~~~~~~~~~~~~
> +
> +  cpuset.cpus
> +	A read-write multiple values file which exists on non-root
> +	cgroups.
> +
> +	It lists the CPUs allowed to be used by tasks within this
> +	cgroup.  The CPU numbers are comma-separated numbers or
> +	ranges.  For example:
> +
> +	  # cat cpuset.cpus
> +	  0-4,6,8-10
> +
> +	An empty value indicates that the cgroup is using the same
> +	setting as the nearest cgroup ancestor with a non-empty
> +	"cpuset.cpus" or all the available CPUs if none is found.
> +
> +	The value of "cpuset.cpus" stays constant until the next update
> +	and won't be affected by any CPU hotplug events.
> +
> +  cpuset.effective_cpus

Can we do cpuset.ecpus in the fashion of euid, egid..?

> +  cpuset.effective_mems

Ditto.

> +  cpuset.flags
> +	A read-write multiple values file which exists on non-root
> +	cgroups.
> +
> +	It lists the flags that are set (with a '+' prefix) and those
> +	that are not set (with a '-' prefix).	The currently supported
> +	flag is:
> +
> +	  mem_migrate
> +		When it is not set, an allocated memory page will
> +		stay in whatever node it was allocated independent
> +		of changes in "cpuset.mems".
> +
> +		When it is set, tasks with memory pages not in
> +		"cpuset.mems" will have those pages migrated over to
> +		memory nodes specified in "cpuset.mems".  Any changes
> +		to "cpuset.mems" will cause pages in nodes that are
> +		no longer valid to be migrated over to the newly
> +		valid nodes.

Let's start just with [e]cpus and [e]mems.  The flags interface looks
fine but the implementations of these features are really bad and
cgroup2 doesn't migrate resources for other controllers either anyway.

Thanks.

-- 
tejun