Re: [PATCH 08/11] perf tool: precise mode requires exclude_guest

[David Ahern]

On 7/24/12 10:15 AM, Robert Richter wrote:
> David,
>
> On 24.07.12 08:20:19, David Ahern wrote:
> > On 7/23/12 12:13 PM, Arnaldo Carvalho de Melo wrote:
> > > Em Fri, Jul 20, 2012 at 05:25:53PM -0600, David Ahern escreveu:
> > > > PEBS cannot be used with guest mode. If user adds :p modifier set
> > > > exclude_guest as well.
> > >
> > > Is this something Intel specific? Or can someone think of an arch where
> > > this limitation wouldn't exist?
> >
> > Good point. So far precise_ip is used by arch/x86 only. I don't have an
> > AMD based server so I don't know if there is a conflict between
> > virtualization and IBS. Added Robert for advice.
>
> thanks for this hint.
>
> On AMD cpus precise_ip maps to IBS, which does not support hardware
> options as perfctrs do. Thus, following attr flags are not supported:
>
>   exclude_user, exclude_kernel, exclude_host, exclude_guest
>
> Counting in guest mode is possible with IBS, but not the exclusion of
> a certain mode. If precise_ip counting is enabled on AMD we may not
> set the exclude_guest flag.

Ok, so with AMD precise_ip requires exclude_guest to be unset; for Intel 
we need it set.

So then we look at vendor_id in /proc/cpuinfo?

David
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