On Tue, May 02, 2023 at 05:26:17PM -0400, Waiman Long <longman@xxxxxxxxxx> wrote: > In the new scheme, the available cpus are still directly passed down to a > descendant cgroup. However, isolated CPUs (or more generally CPUs dedicated > to a partition) have to be exclusive. So what the cpuset.cpus.reserve does > is to identify those exclusive CPUs that can be excluded from the > effective_cpus of the parent cgroups before they are claimed by a child > partition. Currently this is done automatically when a child partition is > created off a parent partition root. The new scheme will break it into 2 > separate steps without the requirement that the parent of a partition has to > be a partition root itself. new scheme 1st step: echo C >p/cpuset.cpus.reserve # p/cpuset.cpus.effective == A-C (1) 2nd step (claim): echo C' >p/c/cpuset.cpus # C'⊆C echo root >p/c/cpuset.cpus.partition current scheme 1st step (configure): echo C >p/c/cpuset.cpus 2nd step (reserve & claim): echo root >p/c/cpuset.cpus.partition # p/cpuset.cpus.effective == A-C (2) As long as p/c is unpopulated, (1) and (2) are equal situations. Why is the (different) two step procedure needed? Also the relaxation of requirement of a parent being a partition confuses me -- if the parent is not a partition, i.e. it has no exclusive ownership of CPUs but it can still "give" it to children -- is child partition meant to be exclusive? (IOW can parent siblings reserve some same CPUs?) Thanks, Michal
