Re: [Qemu-devel] Re: [PATCH 0/4] Rework alarm timer infrastrucure - take2

Luca
2007-08-20T22:49:44Z

On 8/20/07, malc <av1474-3kx9bbwexCU@public.gmane.org> 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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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