On Thu, May 24, 2018 at 02:55:25PM -0400, Waiman Long wrote: > On 05/24/2018 11:43 AM, Peter Zijlstra wrote: > > I'm confused... why exactly do we have both domain and load_balance ? > > The domain is for partitioning the CPUs only. It doesn't change the load > balancing state. So the load_balance flag is still need to turn on and > off load balancing. OK, so we have to two boolean flags, giving 4 possible states. Lets just go through them one by on: A) domain:0 load_balance:0 -- we have no exclusive domain, but have load-balancing disabled across them. AFAICT this should be an invalid state. B) domain:0 load_balance:1 -- we have no exclusive domain, but have load-balancing enabled. AFAICT this is the default state and is a no-op. C) domain:1 load_balance:0 -- we have an exclusive domain, and have load-balancing disabled across it. This is, AFAICT, identical to having a bunch of sub/sibling groups each with a single CPU domain. D) domain:1 load_balance:1 -- we have an exclusive domain, and have load-balancing enabled. This is a partition. Now, I think I've overlooked the fact that load_balance==1 only really means something when the parent's load_balance==0, but I'm not sure that really changes anything. So, afaict, the above only have two useful states: B and D. Which again raises the question, why two knobs? What useful configurations does it allow? -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
