From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: CAP and performance problem Date: Thu, 6 Jun 2013 15:12:07 +0100 Message-ID: <51B098B7.6070601@eu.citrix.com> References: <519B3832.30608@di.unipmn.it> <1370451024.18519.190.camel@Solace> <1370452319.18519.197.camel@Solace> <51AF6FBD.9090007@di.unipmn.it> <1370507870.18519.224.camel@Solace> <51B04F0E.5040506@di.unipmn.it> <51B066CC.4060900@ts.fujitsu.com> <51B067F1.1010008@eu.citrix.com> <51B08606.9090105@di.unipmn.it> <51B08883.50003@ts.fujitsu.com> <51B094D1.9010806@di.unipmn.it> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51B094D1.9010806@di.unipmn.it> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Massimo Canonico Cc: Juergen Gross , Dario Faggioli , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 06/06/13 14:55, Massimo Canonico wrote: > > 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. Some BIOSes have settings that will automatically mess around with the performance settings of the processor. This could be automatically slowing the core down because it's only 50% busy. This would be different on each BIOS. Just take a quick look for anything that seems to say something about performance, and set it to "max" or "performance" mode (as opposed to say, power-saving or balanced mode). You might also try playing around with the "turbo" mode if it's available -- maybe the "turbo" mode takes a bit of time to get going, and running at 50% never kicks it in. If you disable "turbo" mode, you may find that with no cap you get 450s instead of 300s. -George