On Fri, Nov 14, 2025 at 02:24:48PM +0800, Sun Shaojie <[email protected]> wrote: > The desired outcome is that after step #5, although B1 writes "0-3" to > cpuset.cpus, A1 can still remain as "root", and B1 ends up with effective > CPUs of 2-3. In summary, We want to avoid A1's invalidation when B1 > changes its cpuset.cpus. Because cgroup v2 allows the effective CPU mask > of a cpuset to differ from its requested mask.
So the new list of reasons why configured cpuset's cpus change are: - hotplug, - ancestor's config change, - stealing by a sibling (new). IIUC, the patch proposes this behavior: echo root >A1.cpuset.partition echo 0-1 >A1.cpuset.cpus echo root >B1.cpuset.partition echo 1-2 >B1.cpuset.cpus # invalidates A1 echo 0-1 >A1.cpuset.cpus # invalidates B1 ping-pong over CPU 1 ad libitum I think the right (tm) behavior would be not to depend on the order in which config is applied to siblings, i.e. echo root >A1.cpuset.partition echo 0-1 >A1.cpuset.cpus echo root >B1.cpuset.partition echo 1-2 >B1.cpuset.cpus # invalidates both A1 and B1 echo 0-1 >A1.cpuset.cpus # no change anymore (I hope my example sheds some light on my understanding of the situation and desired behavior.) Thanks, Michal
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