Messages in this thread | | | Subject | Re: sched: tweak select_idle_sibling to look for idle threads | From | Mike Galbraith <> | Date | Mon, 09 May 2016 11:39:05 +0200 |
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On Mon, 2016-05-09 at 09:13 +0800, Yuyang Du wrote: > On Mon, May 09, 2016 at 09:44:13AM +0200, Mike Galbraith wrote:
> > In a perfect world, running only Chris' benchmark on an otherwise idle > > box, there would never _be_ any work to steal. > > What is the perfect world like? I don't get what you mean.
In a perfect world from this benchmark's perspective, when you fork or wake while box is underutilized, wakee/child lands on an idle CPU. To this benchmark, anything else is broken.
> > In the real world, we > > smooth utilization, optimistically peek at this/that, and intentionally > > throttle idle balancing (etc etc), which adds up to an imperfect world > > for this (based on real world load) benchmark. > > So, is this a shout-out: these parts should be coordinated better?
Switching to instantaneous load along with the cpu reservation hackery made Chris's benchmark a happy camper. Is that the answer? Nope, just verification of the where the problem lives.
> > > En... should we try remove recording last_wakee? > > > > The more the merrier, go for it! :) > > Nuh, really, this heuristic is too heuristic, :) > The totality of all possible cases is scary.
Well, make it better. The author provided evidence when it was born.
-Mike
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