Messages in this thread | | | Subject | Re: [git pull] scheduler fixes | From | Mike Galbraith <> | Date | Sat, 17 Jan 2009 17:37:12 +0100 |
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On Sat, 2009-01-17 at 17:25 +0100, Ingo Molnar wrote: > * Mike Galbraith <efault@gmx.de> wrote: > > > On Sat, 2009-01-17 at 17:01 +0100, Ingo Molnar wrote: > > > * Mike Galbraith <efault@gmx.de> wrote: > > > > > > > On Sat, 2009-01-17 at 04:43 -0800, Andrew Morton wrote: > > > > > http://bugzilla.kernel.org/show_bug.cgi?id=12465 just popped up - another > > > > > scheduler regression. It has been bisected. > > > > > > > > Seems pretty clear. I'd suggest reverting it. > > > > > > We can revert it (and will revert it if no solution is found), but i'd > > > also like to understand why it happens, because that kind of > > > regression from this change is unexpected - we might be hiding some > > > bug that could pop up under less debuggable circumstances, so we need > > > to understand it while we have a chance. > > > > Agree. However, with the sched_mc stuff, mysql+oltp now does better > > with NEWIDLE on than off as well, as does an nfs kbuild. > > Didnt you come up with the verdict that sched_mc=2 is not a win - or has > that changed? If we should change the defaults then please send a > re-tuning patch against the latest code.
sched_mc=2 was better than sched_mc=1. The other balancing changes put a dent in mysql+oltp peak and immediately after peak. Setting sched_mc=2 brought back the loss that was otherwise there all the way through the curve back to 28 level, so with sched_mc=2, there was only the slight loss of peak, and larger loss of post-peak.
> Still, the ping delays of multiple seconds are completely unacceptable and > need to be understood, or these will come back and might bite us in a lot > less fortunate place. NEWIDLE and WAKE_BALANCE has micro-effects on > latencies - anything in the user-visible range is highly anomalous at > these low load levels. > > Ingo
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