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SubjectRe: [PATCH v3] cpuset: Enable cpuset controller in default hierarchy
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On 11/27/2017 04:04 PM, Tejun Heo wrote:
> 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..?

Sure.
>> + cpuset.effective_mems
> Ditto.

Sure.

>> + 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 + no longer valid to be migrated over to the newly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.

That is added because the mem_migrate feature is used in libvirt, I
think. I am thinking of add a "[EXPERIMENTAL]" tag to the flags to
indicate that it is subject to change.

Cheers,
Longman

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