On Fri, Apr 14, 2023 at 01:29:25PM -0400, Waiman Long wrote: > > On 4/14/23 12:54, Tejun Heo wrote: > > On Thu, Apr 13, 2023 at 09:22:19PM -0400, Waiman Long wrote: > > > I now have a slightly different idea of how to do that. We already have an > > > internal cpumask for partitioning - subparts_cpus. I am thinking about > > > exposing it as cpuset.cpus.reserve. The current way of creating > > > subpartitions will be called automatic reservation and require a direct > > > parent/child partition relationship. But as soon as a user write anything to > > > it, it will break automatic reservation and require manual reservation going > > > forward. > > > > > > In that way, we can keep the old behavior, but also support new use cases. I > > > am going to work on that. > > I'm not sure I fully understand the proposed behavior but it does sound more > > quirky. > > The idea is to use the existing subparts_cpus for cpu reservation instead of > adding a new cpumask for that purpose. The current way of partition creation > does cpus reservation (setting subparts_cpus) automatically with the > constraint that the parent of a partition must be a partition root itself. > One way to relax this constraint is to allow a new manual reservation mode > where users can set reserve cpus manually and distribute them down the > hierarchy before activating a partition to use those cpus. > > Now the question is how to enable this new manual reservation mode. One way > to do it is to enable it whenever the new cpuset.cpus.reserve file is > modified. Alternatively, we may enable it by a cgroupfs mount option or a > boot command line option. It'd probably be best if we can keep the behavior within cgroupfs if possible. Would you mind writing up the documentation section describing the behavior beforehand? I think things would be clearer if we look at it from the interface documentation side. Thanks. -- tejun
