[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] CAP and performance problem

On 06/06/2013 04:12 PM, Dario Faggioli wrote:
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

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?


here we go:

[root@csitest ~]# xl vcpu-list; sleep 10; xl vcpu-list
Name                                ID  VCPU   CPU State   Time(s) CPU
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
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

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?


Actually it seems that the problem is related to a BIOS setting. In my HP server, there were a parameter called "HP power regulator" that I set to "HP Static High-performance power" (before it was set to "dynamic performance power") and now I get what it is expected: cap 50% make my application twice longer than when cap is 100%.

Thanks to all of you guys. I think that this should be reported in the doc where the cap mechanism is explained.


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.