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Re: [Xen-devel] branch counts

To: jaikumar Ganesh <jaikumarg@xxxxxxxxx>
Subject: Re: [Xen-devel] branch counts
From: George Dunlap <dunlapg@xxxxxxxxx>
Date: Wed, 16 Nov 2005 09:36:43 -0500
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As far as I know (my most recent pull from xen-unstable being back in
early July), Xen does not export an interface to the hardware
performance counters yet.  Each platform is so different, a consistent
interface would be a little hard to define.  Furthermore, each of the
branch counters has their own little quirks -- the Athlon counters
count interrupts and some subset of exceptions for instance, and so
are not precise without some extra instrumentation; and the P4
counters don't count far calls.

However, the project I'm working on uses the branch counter for P4 in
Xen.  If you're up for some hacking, I can send you the code we use,
and you can adapt it to your own purposes.
It keeps track of the branch counters per domain, but if you can get
that information to the guest kernel, it can keep track of branch
counters for processes.

What are you looking to use them for?

On 11/15/05, jaikumar Ganesh <jaikumarg@xxxxxxxxx> wrote:
> Hello all
>    Is there any way to get the branch count for the entire VM or a single
> process running on a guest. x86 provides the facility of getting the branch
> count. Does Xen provide anything that we directly use to get the branch
> counts?
> -Thanks
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

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