On 03/20/2018 04:22 PM, Tejun Heo wrote: > Hello, Waiman. > > On Tue, Mar 20, 2018 at 04:12:25PM -0400, Waiman Long wrote: >> After some thought, I am planning to impose the following additional >> constraints on how sched_load_balance works in v2. >> >> 1) sched_load_balance will be made hierarchical, the child will inherit >> the flag from its parent. >> 2) cpu_exclusive will be implicitly associated with sched_load_balance. >> IOW, sched_load_balance => !cpu_exclusive, and !sched_load_balance => >> cpu_exclusive. >> 3) sched_load_balance cannot be 1 on a child if it is 0 on the parent. >> >> With these changes, sched_load_balance will have to be set by the parent >> and so will not be delegatable. Please let me know your thought on that. > So, for configurations, we usually don't let them interact across > hierarchy because that can lead to configurations surprise-changing > and delegated children locking the parent into the current config. > > This case could be different and as long as we always guarantee that > an ancestor isn't limited by its descendants in what it can configure, > it should be okay (e.g. an ancestor should always be able to turn on > sched_load_balance regardless of how the descendants are configured). Yes, I will do some testing to make sure that a descendant won't be able to affect how the ancestors can behave. > Hmmm... can you explain why sched_load_balance needs to behave this > way? It boils down to the fact that it doesn't make sense to have a CPU in an isolated cpuset to participate in load balancing in another cpuset as Mike has said before. It is especially true in a parent-child relationship where a delegatee can escape CPU isolation by re-enabling sched_load_balance in a child cpuset. Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
