linux-kernel - Re: [PATCH] posix-timers: RCU conversion

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Message-ID: <4D9AD92D.401@redhat.com>
Date:	Tue, 05 Apr 2011 11:56:13 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	ben@...u.net, Eric Dumazet <eric.dumazet@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	KVM list <kvm@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	John Stultz <johnstul@...ibm.com>,
	Richard Cochran <richard.cochran@...cron.at>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH] posix-timers: RCU conversion

On 04/05/2011 11:48 AM, Peter Zijlstra wrote:
> What I think is happening is that all your 'idle' qemu thingies keep
> waking up frequently and because you've got like twice the number of
> qemu instances as you've got cpus there's a fair chance you'll have a
> cpu with a pending task while another one goes idle.

Those qemus have two threads each (one vcpu thread, one io thread).

> (Why does qemu keep waking if its idle? broken NOHZ?)

Could be waking up due to guest wakeups, or qemu internal wakeups 
(display refresh) or due to guest timer sources which are masked away in 
the guest (if that's the case we should optimize it away).

-- 
error compiling committee.c: too many arguments to function

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