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RE: [Xen-ia64-devel] [PATCH] [Resend]Enable hash vtlb


  • To: "Xu, Anthony" <anthony.xu@xxxxxxxxx>, "Williamson, Alex (Linux Kernel Dev)" <alex.williamson@xxxxxx>
  • From: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
  • Date: Mon, 10 Apr 2006 16:20:55 -0700
  • Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 10 Apr 2006 16:22:49 -0700
  • List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
  • Thread-index: AcZcq7LX/2eAEZLZRf2UEjafNqjGygAARoawAAMdXuAADsSJMA==
  • Thread-topic: [Xen-ia64-devel] [PATCH] [Resend]Enable hash vtlb

> I wonder if the time command is appropriate for measuring
> performance in a domU?  Are we sure the "real" component
> is measuring elapsed wall clock time?  If not, perhaps
> "time" is not accounting for time spent in the hypervisor
> and time spent in dom0 (e.g. backend drivers).
> 
> In all my past measurements, I've used "date +%s" before
> and after and subtracted the difference.

FYI, I did a preliminary test and found that "time" and
"date +%s" are yielding essentially the same result for dom0,
even with dom0 also doing Linux builds.  So ignore that
question.

However, I did see widely varying time results for domU,
varying in some cases by more than 10% (yes, I ignored
the builds that ended with "gcc segmentation fault" and
the first build). Are others seeing a wide variance also?

Dan

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