Re: [Engine-devel] what does engine with cpuIdle?
On Tue, Sep 11, 2012 at 07:38:11AM -0400, Laszlo Hornyak wrote:
----- Original Message -----
> From: "Dan Kenigsberg" <danken(a)redhat.com>
> To: "Omer Frenkel" <ofrenkel(a)redhat.com>
> Cc: "Laszlo Hornyak" <lhornyak(a)redhat.com>, "engine-devel"
<engine-devel(a)ovirt.org>
> Sent: Tuesday, September 11, 2012 9:22:15 AM
> Subject: Re: [Engine-devel] what does engine with cpuIdle?
>
> On Tue, Sep 11, 2012 at 01:55:01AM -0400, Omer Frenkel wrote:
> >
> >
> > ----- Original Message -----
> > > From: "Laszlo Hornyak" <lhornyak(a)redhat.com>
> > > To: "engine-devel" <engine-devel(a)ovirt.org>
> > > Sent: Monday, September 10, 2012 3:51:59 PM
> > > Subject: [Engine-devel] what does engine with cpuIdle?
> > >
> > > hi,
> > >
> > > I am trying to change a behavior in vdsm. When you pass 100% load
> > > on
> > > a VM, it will stop reporting further load and will keep telling
> > > 100%
> > > until the load drops under 100% again in it's cpuIdle
> > > information.
> > > This is totally correct if you have only single-cpu VM's, but it
> > > is
> > > false when you have multiple vcpu's, I think the cpuIdle
> > > information
> > > should not be on a 0-100 scale, but on a 0-100*vcpus scale.
> > >
> > > So I submitted this patch to vdsm:
> > > http://gerrit.ovirt.org/#/c/7892/2
> > > and Dan pointed out that some functionality may depend on the
> > > value
> > > in the 0-100 interval. For me it seems it is ignored and the load
> > > is
> > > calculated only from sysCpu + userCpu. Does anyone build on the
> > > cpuIdle value?
> > >
> > > Thanks,
> > > Laszlo
> > >
> >
> > you are right, engine doesn't save cpuIdle for vm,
> > so it's not in use in the engine.
>
> Laszlo, in this case, I think it would be best to drop this bogus
> piece
> of information.
Ok.
However, before I abandon this patch:
Why abandon? I've suggested you to keep it, just make it even simpler.
we have a requirement to report cpuSys and cpuUser separately. Afaik
in libvirt cpuUser and cpuSys does not include the actual guest time
(at least not with KVM), and in this way if we only report cpuSys and
cpuUser, the sum does not give the actual load, only a relatively
little percentage of it.
I am not sure I understand what you are saying, but afaik, libvirt's
relatively-new
http://libvirt.org/html/libvirt-libvirt.html#virDomainGetCPUStats
reports the cpu time spent by the entire qemu process - in guest and
host modes.
If we have the cpuIdle information in engine,
we can calculate the guest time. Therefore, should I - include the
guest time in cpuSys or cpuUser?
- add another exported field?
And in both case, we will still have to calculate from cpuIdle because
libvirt does not tell the guest cpu time :-(
Now I'm completely at loss. Why should we calculate cpuIdle per VM?
Haven't we agreed that it is useless?
Dan.