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SubjectRe: [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1
On Mon, Feb 27, 2012 at 10:30:58AM +0100, Peter Zijlstra wrote:
> On Mon, 2012-02-27 at 17:08 +0800, Yong Zhang wrote:
> > On Mon, Feb 27, 2012 at 09:38:01AM +0100, Peter Zijlstra wrote:
> > > On Fri, 2012-02-24 at 14:13 +0800, Yong Zhang wrote:
> > >
> > > > This remind me that we should have moved the irq_enter()/irq_exit() to
> > > > each arch's related irq handler.
> > > > see: http://marc.info/?l=linux-kernel&m=130709505700821&w=2
> > > >
> > > > So Peter, is there someone alread on it? or it still worth doing now?
> > >
> > > trouble was that some people didn't feel comfortable adding that
> > > overhead to plain resched IPIs that didn't need to do anything.
> >
> > Any ideas on where the plain resched IPIs come from?
>
> remote wakeups that don't queue I guess.
>
> IIRC I looked at it a while back and while not in the majority there
> were still a few (I only added counters, didn't look where they came
> from).
>
> However since 518cd623 there'd be a lot more I guess..
>
> Feel free to investigate. Also, some non-sched users of the resched ipi
> exist, eg. KVM uses it to kick a remote vcpu out from guest mode.

Thanks for the detail.

Will try to find if there is something interesting.

Thanks,
Yong


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