Hello. The previous thread arrived incomplete to me, so I respond to the last message only. Point me to a message URL if it was covered. On Fri, Apr 14, 2023 at 03:06:27PM -0400, Waiman Long <longman@xxxxxxxxxx> wrote: > Below is a draft of the new cpuset.cpus.reserve cgroupfs file: > > cpuset.cpus.reserve > A read-write multiple values file which exists on all > cpuset-enabled cgroups. > > It lists the reserved CPUs to be used for the creation of > child partitions. See the section on "cpuset.cpus.partition" > below for more information on cpuset partition. These reserved > CPUs should be a subset of "cpuset.cpus" and will be mutually > exclusive of "cpuset.cpus.effective" when used since these > reserved CPUs cannot be used by tasks in the current cgroup. > > There are two modes for partition CPUs reservation - > auto or manual. The system starts up in auto mode where > "cpuset.cpus.reserve" will be set automatically when valid > child partitions are created and users don't need to touch the > file at all. This mode has the limitation that the parent of a > partition must be a partition root itself. So child partition > has to be created one-by-one from the cgroup root down. > > To enable the creation of a partition down in the hierarchy > without the intermediate cgroups to be partition roots, Why would be this needed? Owning a CPU (a resource) must logically be passed all the way from root to the target cgroup, i.e. this is expressed by valid partitioning down to given level. > one > has to turn on the manual reservation mode by writing directly > to "cpuset.cpus.reserve" with a value different from its > current value. By distributing the reserve CPUs down the cgroup > hierarchy to the parent of the target cgroup, this target cgroup > can be switched to become a partition root if its "cpuset.cpus" > is a subset of the set of valid reserve CPUs in its parent. level n `- level n+1 cpuset.cpus // these are actually configured by "owner" of level n cpuset.cpus.partition // similrly here, level n decides if child is a partition I.e. what would be level n/cpuset.cpus.reserve good for when it can directly control level n+1/cpuset.cpus? Thanks, Michal
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