Hi, Michal, On Tue, 18 Nov 2025 18:52:24 +0100, Michal Koutný wrote: >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.)
This patch is based on a version after v6.18.0-rc5. Whether or not this patch is applied, modifications to cpuset.partition do not affect the state of sibling partitions. If continue, the result should be as follows: #4> echo "root" > B1/cpuset.partition | root | root invalid | I've updated patch v5 with some new ideas and look forward to your feedback. patch v5 : https://lore.kernel.org/cgroups/[email protected]/ Thanks, Sun Shaojie
