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Date: Mon, 07 Feb 2011 14:34:07 +0200
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] Re: [RFC: 0/2] patch for QEMU HPET periodic timer
	emulation to alleviate time drift
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: kvm <kvm@vger.kernel.org>, Glauber Costa <glommer@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Ulrich Obergfell <uobergfe@redhat.com>

On 02/04/2011 10:56 AM, Jan Kiszka wrote:
> >
> >  This should be a rare event.  If you are missing 50% of your
> >  notifications, not amount of gradual catchup is going to help you out.
>
> But that's the only thing this patch is after: lost ticks at QEMU level.

Most lost ticks will happen at the vcpu level.  The iothread has low 
utilization and will therefore be scheduled promptly, whereas the vcpu 
thread may have high utilization and will thus be preempted.  When it is 
preempted for longer than the timer tick, we will see vcpu-level 
coalescing.  All it takes is 2:1 overcommit to see time go half as fast; 
I don't think you'll ever see that on bare metal.

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