Hello. On Thu, Nov 13, 2025 at 09:14:34PM +0800, Sun Shaojie <[email protected]> wrote: > In cgroup v2, a mutual overlap check is required when at least one of two > cpusets is exclusive. However, this check should be relaxed and limited to > cases where both cpusets are exclusive. > > The table 1 shows the partition states of A1 and B1 after each step before > applying this patch. > > Table 1: Before applying the patch > Step | A1's prstate | B1's prstate | > #1> mkdir -p A1 | member | | > #2> echo "0-1" > A1/cpuset.cpus | member | | > #3> echo "root" > A1/cpuset.cpus.partition | root | | > #4> mkdir -p B1 | root | member | > #5> echo "0-3" > B1/cpuset.cpus | root invalid | member | > #6> echo "root" > B1/cpuset.cpus.partition | root invalid | root invalid | > > After step #5, A1 changes from "root" to "root invalid" because its CPUs > (0-1) overlap with those requested by B1 (0-3). However, B1 can actually > use CPUs 2-3, so it would be more reasonable for A1 to remain as "root."
I remember there was the addition of cgroup_file_notify() for the cpuset.cpus.partition so that such changes can be watched for. I may not be seeing whole picture, so I ask -- why would it be "more reasonable" for A1 to remain root. From this description it looks like you'd silently convert B1's effective cpus to 2-3 but IIUC the code change that won't happen but you'd reject the write of "0-3" instead. Isn't here missing Table 2: After applying the patch? I'm asking because of the number 1 but also because it'd make the intention clearer ;-), perhaps with a column for cpuset.cpus.effective. Thanks, Michal
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