From mboxrd@z Thu Jan 1 00:00:00 1970 From: Massimo Canonico Subject: Re: CAP and performance problem Date: Tue, 21 May 2013 16:28:04 +0200 Message-ID: <519B8474.40501@di.unipmn.it> References: <519B3832.30608@di.unipmn.it> <519B6089.9050909@di.unipmn.it> <1369141576.12423.73.camel@Solace> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1369141576.12423.73.camel@Solace> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Dario Faggioli Cc: George Dunlap , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org Hi Dario, inline my answers On 05/21/2013 03:06 PM, Dario Faggioli wrote: > On mar, 2013-05-21 at 13:54 +0200, Massimo Canonico wrote: >> Hi George, >> thanks for your answer. >> >> Our physical machine has two processors and two cores for each processors. >> >> The virtual machine where our application run has just one VCPU that is >> pinned to a single core. >> Instead, dom0 was not pinned to any particular core. >> > Ok, and what are you doing in Dom0? I guess almost nothing, is that the > case? yes > > Also, when inspecting the vCPU utilization, do you see the VM vCPU busy > up to 100% without cap (or with cap set to 100) and, OTOH, up to 50% > with cap set to 50? I have monitored the CPU usage with xentop during the experiment and I got what you said: my application always use the total amonut of CPU available. > Well, looks like a scheduling issue, or, in any case, one where > something is interacting with the scheduling. Can you perhaps boot Dom0 > so that it uses only 2 or 3 cores (or arrange for that later, e.g., with > cpupools) and pin the vCPU of the VM on the 4th one? In my experiments, I pin the vCPU of the VM on one core and other cores are pinned to Dom0. [root@csitest ~]# xl vcpu-list Name ID VCPU CPU State Time(s) CPU Affinity Domain-0 0 0 0 --- 383.3 0 Domain-0 0 1 0 -b- 358.1 0 Domain-0 0 2 0 -b- 224.3 0 Domain-0 0 3 0 r-- 256.8 0 rubis-web 1 0 2 -b- 9250.9 2 (rubis-web is, of course, the VM where my application run) Is this configuration what you meant? Thanks, Massimo > > I'm not sure what could be going on, but that sounds a reasonable way to > rule out as much room for interference as possible... > > Dario >