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Subject: Re: [RFC PATCHv3] perf tools: add event grouping capability to
 "perf stat"
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Stephane Eranian <eranian@google.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, Julia Lawall <julia@diku.dk>,
        Tom Zanussi <tzanussi@gmail.com>, linux-kernel@vger.kernel.org,
        Matt Fleming <matt@console-pimps.org>
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Date: Thu, 25 Nov 2010 07:32:40 +0100
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On Wed, 2010-11-24 at 17:54 -0800, Corey Ashford wrote:
> Add the ability to create multiple event groups, each with their own leader
> using the existing "-e <event>[,<event> ...] [-e <event>[,<event>]]"
> syntax.  Each additional -e switch creates a new group, and each event
> listed within a -e switch is within that group.
> 
> Changes since v1:
> - Because of a flub, v2 did not contain the changes I had intended to make,
> and instead, v2 had the same patch contents as v1.
> - When perf stat is not supplied any events on the command line, put
> each default event in its own group.

I like this, but could you also extend this to perf-record? its a bit
odd to diverge between the two.

Using Stephane's latest syntax changes you could actually do something
like:

perf record -e task-clock:freq=1000,cycles:period=0

Which would create a group with 1 sampling counter and a counting
counter (at which point we should probably start flipping
PERF_SAMPLE_READ).

Matt was working on supporting that (although not through cmdline
syntax) and teaching perf-report to cope with such output.