linux-kernel - Re: [PATCH 08/11] perf tool: precise mode requires exclude

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Date:	Tue, 24 Jul 2012 11:28:48 -0600
From:	David Ahern <dsahern@...il.com>
To:	Robert Richter <robert.richter@....com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <peterz@...radead.org>
CC:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Gleb Natapov <gleb@...hat.com>
Subject: Re: [PATCH 08/11] perf tool: precise mode requires exclude_guest

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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