Re: [PATCH v11 7/8] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst

Waiman Long
2022-06-13T19:11:14Z

On 6/13/22 09:18, Waiman Long wrote:
> On 6/12/22 23:12, Tejun Heo wrote:
>> Hello,
>>
>> On Sun, Jun 12, 2022 at 11:02:38PM -0400, Waiman Long wrote:
>>> That is the behavior enforced by setting the CPU_EXCLUSIVE bit in
>>> cgroup v1.
>>> I haven't explicitly change it to make it different in cgroup v2.
>>> The major
>>> reason is that I don't want change to one cpuset to affect a sibling
>>> partition as it may make the code more complicate to validate if a
>>> partition
>>> is valid.
>> If at all possible, I'd really like to avoid situations where a
>> parent can't
>> withdraw resources due to something that a descendant does.
>
> No, it doesn't affect parent at all. It just limit whats the siblings
> can do due to their mutual constraint. If this is what the confusion
> is about, I will try to reword the doc text.

I am planning to make the following change to the documentation patch.
Please let me know if that can clarify the confusion, if any.

Thanks,
Longman

diff --git a/Documentation/admin-guide/cgroup-v2.rst
b/Documentation/admin-guid>
index 9184a09e0fc9..9cbfa25dab97 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2176,7 +2175,8 @@ Cpuset Interface Files

For a valid partition root or an invalid partition root with
the exclusivity rule enabled, changes made to "cpuset.cpus"
-       that violate the exclusivity rule will not be allowed.
+       that violate the exclusivity rule with its siblings will not
+       be allowed.

A valid non-root parent partition may distribute out all its CPUs
to its child partitions when there is no task associated with it.