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Date: Tue, 21 Aug 2007 00:49:44 +0200
From: Luca <kronos.it@gmail.com>
Subject: Re: [kvm-devel] [Qemu-devel] Re: [PATCH 0/4] Rework alarm timer
	infrastrucure - take2
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To: malc <av1474@comtv.ru>
Cc: kvm-devel@lists.sf.net, qemu-devel@nongnu.org

On 8/20/07, malc <av1474@comtv.ru> wrote:
> On Mon, 20 Aug 2007, Luca Tettamanti wrote:
>
> > Il Sun, Aug 19, 2007 at 10:31:26PM +0300, Avi Kivity ha scritto:
> >> Luca wrote:
> >>> On 8/19/07, Luca Tettamanti <kronos.it@gmail.com> wrote:
> >>>
> >>>> +static uint64_t qemu_next_deadline(void) {
> >>>> +    uint64_t nearest_delta_us = ULLONG_MAX;
> >>>> +    uint64_t vmdelta_us;
> >>>>
> >>>
> >>> Hum, I introduced a bug here... those vars should be signed.
> >>>
> >>> On the overhead introduced: how do you measure it?
> >>>
> >>>
> >>
> >> Run a 100Hz guest, measure cpu usage using something accurate like
> >> cyclesoak, with and without dynticks, with and without kvm.
> >
> > Ok, here I've measured the CPU usage on the host when running an idle
> > guest.
> >
[...]
> The upshot is this - if you have used any standard utility (iostat,
> top - basically anything /proc/stat based) the accounting has a fair
> chance of being inaccurate. If cyclesoak is what you have used then
> the results should be better, but still i would be worried about
> them.

Yes, I've used cyclesoak.

Luca