Re: [Xen-devel] CAP and performance problem

[Massimo Canonico <mex@xxxxxxxxxxxx>]

On 06/06/2013 03:02 PM, Juergen Gross wrote:
> On 06.06.2013 14:52, Massimo Canonico wrote:
> > On 06/06/2013 12:44 PM, George Dunlap wrote:
> > > On 06/06/13 11:39, Juergen Gross wrote:
> > > > On 06.06.2013 10:57, Massimo Canonico wrote:
> > > > > On 06/06/2013 10:37 AM, Dario Faggioli wrote:
> > > > > > On mer, 2013-06-05 at 19:05 +0200, Massimo Canonico wrote:
> > > > > > > Hi Dario,
> > > > > > > and thanks for these test.
> > > > > > >
> > > > > > > I forgot to ask you which xen version has beed used for your 
> > > > > > > experiments.
> > > > > > Yeah, me too! :-)
> > > > > >
> > > > > > I'm using xen-unstable, pulled yesterday (commit id
> > > > > > e430510e5cbbfcdc1077739292def633e70fedea), compiled and installed 
> > > > > > on a
> > > > > > Debian unstable system. Dom0 kernel is a bit old, as it's a 3.6.
> > > > > >
> > > > > > What about you?
> > > > > xen 4.2.2
> > > > > kernel dom0: 3.8.11-200.fc18.x86_64
> > > > Just had an idea: is there any other load on the system during your 
> > > > test (other
> > > > domains, dom0 load)? If not, it could be that the power management 
> > > > is reducing
> > > > the cpu speed during idle (when the cap applies). This could lead 
> > > > to reduced
> > > > performance overall.
> > > >
> > > > You can test this by setting the xen hypervisor boot option
> > > >
> > > > cpufreq=none
> > > >
> > > > and run your test again (with and without cap).
> > > Ah, genius Juergen! That would make total sense.
> > >
> > > -George
> > Unfortunately, this did not change much. I set "cpufreq=none" in the 
> > boot line
> You added the boot parameter for the hypervisor, not dom0? 
Fedora, after few seconds, asks you which kernel do you want to use. You 
can add some parameter in the command line who launches the kernel. So, 
I add "cpufreq=none" in the command line.
> And (please forgive
> my paranoia) you rebooted the complete system after that?
Your paranoia is also mine, I always reboot my machines. Thanks for asking.
> > and restart my experiment.
> > With no cap I got 298.029
> > with cap=50% I got 910.272
> > (average values of 3 experiments for each cap setting)
> >
> > dom0 load during the experiment is less than 1% (that says xentop)
> What was the load reported by xentop for your domu?
My virtual machines is called rubis-web and during "cap=50%" experiment 
I can see this values in xentop for this specific domain.
> Could you try:
>
> xl vcpu-list; sleep 10; xl vcpu-list
>
> when the test is running and post the output?
>
>
> Juergen
here we go:

[root@csitest ~]# xl vcpu-list; sleep 10; xl vcpu-list
Name                                ID  VCPU   CPU State   Time(s) CPU 
Affinity
Domain-0                             0     0    0   ---      23.0  0
Domain-0                             0     1    0   ---      10.5  0
Domain-0                             0     2    0   ---       8.5  0
Domain-0                             0     3    0   r--       6.8  0
rubis-web                            1     0    2   r--    2968.5  2
Name                                ID  VCPU   CPU State   Time(s) CPU 
Affinity
Domain-0                             0     0    0   ---      23.0  0
Domain-0                             0     1    0   r--      10.6  0
Domain-0                             0     2    0   ---       8.5  0
Domain-0                             0     3    0   ---       6.8  0
rubis-web                            1     0    2   r--    2973.5  2

Concerning the George's question:
> Have you checked your BIOS for performance settings?
I'm not sure what you mean for "BIOS perfomance settings". To my best 
knowledge, in the BIOS I have to be sure that the "hw virtualization" is 
enabled.
Thanks for your time,
 M



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