linux-kernel - Re: [PATCH v2 1/2] perf tools: add event modifier to request exclusive PMU access

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Message-ID: <CABPqkBTJsZHdvp+Tm3SGJCfJ7eMFaqQR8pd9eoh5KyBo3k6o3Q@mail.gmail.com>
Date:	Mon, 22 Oct 2012 16:55:41 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v2 1/2] perf tools: add event modifier to request
 exclusive PMU access

On Mon, Oct 22, 2012 at 3:53 PM, Andi Kleen <ak@...ux.intel.com> wrote:
> On Mon, Oct 22, 2012 at 03:20:51PM +0200, Stephane Eranian wrote:
>> This patch adds the x modifier for events. It allows users to
>> request exclusive PMU access (attr->exclusive):
>>
>> perf stat -e cycles:x ......
>> or
>> perf stat -e cpu/cycles/x ....
>>
>> Exclusive mode is a feature of perf_events which was not yet
>> supported by the perf tool. Some events may require exclusive
>> PMU access (like on Intel SandyBridge).
>
> You probably should add it also to be readable from sysfs
>
Not sure I understand what you mean here.

x is not a HW property, this is a perf_event feature. It should NOT be
exposed in /sys/device/cpu/format/.

But maybe you're talking about a generic event exports in
/sys/device/cpu/events.
But why would I expose prec_dist there. And under what name?


> (like I did with precise in my haswell patchkit)
>
> Then the SNB version of instructions-p can just force this
> without the user having to do anything special.
>
> -Andi
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