Re: [Xen-devel] CAP and performance problem

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On gio, 2013-06-06 at 15:55 +0200, Massimo Canonico wrote:
> On 06/06/2013 03:02 PM, Juergen Gross wrote:
> > 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.
>
IIRC, that won't do, as you're most likely modifying Dom0 command line,
you need to be sure you're adding that bit to the Xen boot command
line. 

I think you can do that dynamically, by editing the grub2 parameters
on-line, as you're saying you did, but you have to make sure you affect
Xen and not Linux. IIRC

Otherwise, you should go to /etc/default/grub (I think), look for
something like GRUB_CMDLINE_XEN (I think) add the "cpufreq=none" string
there and regenerate grub.cfg by running:

# grub2-mkconfig -o /boot/grub2/grub.cfg

After that, I recommend double checking that /boot/grub2/grub.cfg has
it, and has it in the right place.

Feel free to post it here, if you're not sure about that...

> > 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
> 
So, rubis-web's vcpu ran for 5 secs, which sounds right. I see why
Jurgen asked you to do that, but not how he plans to squeeze anything
more than that from these numbers... Waiting for him to enlighten us
again! ;-P

> 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.
> 
I think he was referring to something related to poerformance vs. power
management, i.e., cpufreq/speedstep tweaks, and stuff like that, if ou
have any in the BIOS... Do you?

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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