Messages in this thread |  | | | Date | Sun, 18 Jan 2009 10:29:20 +0200 | | From | Avi Kivity <> | | Subject | Re: [git pull] scheduler fixes |
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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. > > 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
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