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Date: Sun, 18 Jan 2009 10:29:20 +0200 From: Avi Kivity <avi@...hat.com> To: Ingo Molnar <mingo@...e.hu> CC: Mike Galbraith <efault@....de>, Kevin Shanahan <kmshanah@...b.org.au>, Andrew Morton <akpm@...ux-foundation.org>, a.p.zijlstra@...llo.nl, torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [git pull] scheduler fixes Ingo Molnar wrote: > * Mike Galbraith <efault@....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. > > Below is the commit in question. Avi, any ideas what makes KVM special > here? Perhaps its use of "preempt notifiers" is causing a problem somehow? > preempt notifiers use should cause additional context switch costs of a few thousand cycles and possible an IPI (if a vcpu was migrated). So I'd suspect scheduling latency here. Is it possible to trace this (the time between a wake up and actual scheduling of a task)? -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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