From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karl Rister Subject: Re: cpu utilization monitoring Date: Mon, 11 Sep 2006 16:48:45 -0500 Message-ID: <200609111648.45756.kmr@us.ibm.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: Xen Devel List-Id: xen-devel@lists.xenproject.org Is there a more appropriate interface for collecting this information then? I would like to be able to sample on an some interval (say 3 or 5 seconds) and be able to see the amount of time a vcpu spent running on the individual physical processors during that time. On Monday 11 September 2006 2:56 pm, Keir Fraser wrote: > The hypercall reports the point-of-view of the timeline of that VCPU. The > fact that its timeline may involve running on various different physical > CPUs should not matter, except for cache-warming and other > context-switching costs. The runstate_info interface absolutely does not > state that the reported run time only includes time spent running on the > currently assigned physical CPU. > > -- Keir > > On 11/9/06 8:44 pm, "Karl Rister" wrote: > > Currently in the vcpu_runstate_info structure we have fields that contain > > the time spent when the vcpu is in one of four states. When trying to > > determine the physical utilization that a vcpu is requiring of the system > > from libxc we make a domctl operation call to the XEN_DOMCTL_getvcpuinfo > > command. When processing this command we pull the value for the > > RUNSTATE_running field and attribute it to the processor that the vcpu is > > currently running on. > > > > I believe that with the new credit scheduler these values are wrong as it > > is possible that the vcpu has time in RUNSTATE_running that was not > > actually spent on the currently running processor. Is there a separate > > path through the libraries and into Xen that retrieves this information > > in a more correct manner? Given that a vcpu can migrate among several > > physical processors in the time between samples it seems that a finer > > grained accounting mechanism is needed to correctly report physical > > utilization of the hardware resources. -- Karl Rister IBM Linux Performance Team kmr@us.ibm.com