Messages in this thread | | | Subject | Re: [PATCH RFC/TEST] sched: make sync affine wakeups work | From | Mike Galbraith <> | Date | Fri, 02 May 2014 07:41:29 +0200 |
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On Fri, 2014-05-02 at 07:32 +0200, Mike Galbraith wrote: > On Fri, 2014-05-02 at 00:42 -0400, Rik van Riel wrote: > > Currently sync wakeups from the wake_affine code cannot work as > > designed, because the task doing the sync wakeup from the target > > cpu will block its wakee from selecting that cpu. > > > > This is despite the fact that whether or not the wakeup is sync > > determines whether or not we want to do an affine wakeup... > > If the sync hint really did mean we ARE going to schedule RSN, waking > local would be a good thing. It is all too often a big fat lie.
BTW, we used to have avg_overlap and a sync less heuristic to improve the accuracy of the sync wakeup hint, but I ripped it out because it was dead wrong far too often. You can try reviving it, but preemption among other things break it. You'll have better luck with a simple context switch rate heuristic, but that's less than perfect too.
-Mike
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