From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hollis Blanchard Date: Thu, 02 Dec 2010 18:38:11 +0000 Subject: Re: kvm ppc timing stats Message-Id: <4CF7E793.3060803@mentor.com> List-Id: References: <9696D7A991D0824DBA8DFAC74A9C5FA306995614@az33exm25.fsl.freescale.net> In-Reply-To: <9696D7A991D0824DBA8DFAC74A9C5FA306995614@az33exm25.fsl.freescale.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-ppc@vger.kernel.org I don't think the numbers added up like that for us either. We treated them as relative data, not absolute. I don't remember how early/late the timestamps were recorded, but obviously they cannot cover 100% of the handler. As the number of exits increases, those unaccounted-for instructions would add up... but I wouldn't expect that to cause errors of the magnitude you're seeing. Perhaps there is a more obvious problem with the way certain exit types are recorded (or not recorded). Hollis Blanchard Mentor Graphics, Embedded Systems Division On 12/01/2010 08:18 PM, Yoder Stuart-B08248 wrote: > Well, in the example I'm looking at, which runs for 30 > seconds, the "sum" column of the stats adds up to > about 10 seconds total. So, there is 20 seconds > unaccounted for. > > Interestingly enough, if I let the guest just sit > idle for 30 seconds, the stats do sum up to about > 30 seconds. > > Will get to the bottom of it, but wanted to make > sure I was not missing something obvious. > > Stuart > > >> -----Original Message----- >> From: Hollis Blanchard [mailto:hollis_blanchard@mentor.com] >> Sent: Wednesday, December 01, 2010 6:27 PM >> To: Yoder Stuart-B08248 >> Cc: kvm-ppc@vger.kernel.org >> Subject: Re: kvm ppc timing stats >> >> Yes, your understanding is correct (barring any bugs, of course). Why > do >> you think "time is missing"? >> >> Hollis Blanchard >> Mentor Graphics, Embedded Systems Division >> >> >> On 12/01/2010 12:02 PM, Yoder Stuart-B08248 wrote: >>> Hollis, >>> >>> Am looking at some performance data and want to make sure that >>> >>> I'm understanding things correctly with your CONFIG_KVM_EXIT_TIMING >>> >>> stuff. If I reset the timing counters, run a workload >>> >>> under for a fixed duration (e.g. 30 seconds), and then look >>> >>> at the exit stats, I should see 30 seconds worth of time accounted >>> >>> for, correct? >>> >>> Right now I'm seeing a substantial amount of time "missing" and >>> >>> want to make sure I'm not missing something. >>> >>> Stuart >>> >