On Mon, Nov 17, 2025 at 09:57:08AM +0800, Sun Shaojie <[email protected]> wrote: > This patch ensures that for sibling cpusets A1 (exclusive) and B1 > (non-exclusive), change B1 cannot affect A1's exclusivity. > > for example. Assume a machine has 4 CPUs (0-3). > > root cgroup > / \ > A1 B1 > > Case 1: > Table 1.1: Before applying the patch > Step | A1's prstate | B1'sprstate | > #1> echo "0-1" > A1/cpuset.cpus | member | member | > #2> echo "root" > A1/cpuset.cpus.partition | root | member | > #3> echo "0" > B1/cpuset.cpus | root invalid | member | > > After step #3, 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(from B1's parent), so it would be more reasonable for A1 to > remain as "root." > > Table 1.2: After applying the patch > Step | A1's prstate | B1'sprstate | > #1> echo "0-1" > A1/cpuset.cpus | member | member | > #2> echo "root" > A1/cpuset.cpus.partition | root | member | > #3> echo "0" > B1/cpuset.cpus | root | member |
OK, this looks fine to me, based on this statement from the docs about cpuset.cpus.effective: > subset of "cpuset.cpus" unless none of the CPUs listed in "cpuset.cpus" > can be granted. In this case, it will be treated just like an empty > "cpuset.cpus". I was likely confused by the eventual switch of B1 to root in your previous example. (Because if you continue, it should result in (after patch too): #4> echo "root" > B1/cpuset.partition | root invalid | root invalid | and end state should be invariant wrt A1,B1 or B1,A1 config order.) > All other cases remain unaffected. For example, cgroup-v1, both A1 and B1 > are exclusive or non-exlusive. (Note, I'm only commenting the concept here, I haven't checked the code change actually achieves that and doesn't break anythine else ;-) Thanks, Michal
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