Bill Holler wrote: > Madhavan Venkataraman wrote: > >> Bill Holler wrote: >> >>> How often will callouts cause a cross-call to another cpu? >>> Will this be eliminated with the new per-cpu callout infrastructure? >>> >>> >>> >> Callouts, by themselves, don't use X-calls. However, normal callouts are >> handled via taskq threads. So, waking up a taskq thread will involve >> the customary preemption actions which will involve X-calls. >> Also, realtime callouts are typically used to wake up threads. >> This wake up can involve the same kind of X-calls. >> There isn't a whole lot we can do about it. >> > > Thinking out loud: Callouts will often cause threads to be > dispatched on cpus other then the one the callout/cyclic > occurred on. We do not currently know how to account > for this in idle cpu sleep time prediction.... > Sounds like a job for the Power Aware Dispatcher. :-b > Yes, the dispatcher can potentially help here....for example, perhaps some FIFO behavior where the most recently busy CPUs tend to be used sooner...in which case those CPUs could know that they are in the "bullpen" or not.
-Eric
