Messages in this thread | | | Date | Tue, 27 May 2014 20:55:20 +0800 | From | Libo Chen <> | Subject | Re: balance storm |
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On 2014/5/27 17:48, Peter Zijlstra wrote: > So: > > 1) what kind of weird ass workload is that? Why are you waking up so > often to do no work?
it's just a testcase, I agree it doesn`t exist in real world.
> > 2) turning on/off share_pkg_resource is a horrid hack whichever way > aruond you turn it. > > So I suppose this is due to the select_idle_sibling() nonsense again, > where we assumes L3 is a fair compromise between cheap enough and > effective enough. > > Of course, Intel keeps growing the cpu count covered by L3 to ridiculous > sizes, 8 cores isn't nowhere near their top silly, which shifts the > balance, and there's always going to be pathological cases (like the > proposed workload) where its just always going to suck eggs. > > Also, when running 50 such things on a 16 cpu machine, you get roughly 3 > per cpu, since their runtime is stupid low, I would expect it to pretty > much always hit an idle cpu, which in turn should inhibit the migration. > > Then again, maybe the timer slack is causing you grief, resulting in all > 3 being woken at the same time, instead of having them staggered. > > In any case, I'm not sure what the 'regression' report is against, as > there's only a single kernel version mentioned: 3.4, and that's almost a upstream has the same problem, I have mentioned before.
> dinosaur.
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