linux-kernel - Re: [RFC 0/4] perf tool: Adding ratios support

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Message-ID: <CAOPLpQeHTCwr4tuHi0nORCn+LKJRzEGoCWhC-rj30nLe7bY5Nw@mail.gmail.com>
Date:	Wed, 16 Jan 2013 09:00:07 -0500
From:	Ulrich Drepper <drepper@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andi Kleen <andi@...stfloor.org>,
	David Ahern <dsahern@...il.com>
Subject: Re: [RFC 0/4] perf tool: Adding ratios support

On Tue, Jan 15, 2013 at 8:39 AM, Jiri Olsa <jolsa@...hat.com> wrote:
>   $ perf stat -f formula.conf:cpi kill
>   usage: kill [ -s signal | -p ] [ -a ] pid ...
>          kill -l [ signal ]

I do like this proposal.  The only comment I have is that perhaps the
command line syntax isn't ideal.  What you use above is tied to the
ratios be defined in the config file.  I would imagine that at least
over time (for some ratios probably right away) they become available
by default and don't require a config file.  Also, users might want to
put individualized ratio definitions in a config file which is read by
default.

How about the formulas becoming available whenever the config file is
read.  Maybe this means a few more keywords in the config file (ratio,
ratio-set, ...).  E.g.:

ratio-set branch {
          events = {instructions,branch-instructions,branch-misses}:u

          ratio branch-rate {
                  formula = branch-instructions / instructions
                  desc = branch rate
          }

          ratio branch-miss-rate {
                  formula = branch-misses / instructions
                  desc = branch misprediction rate
          }

          ratio branch-miss-ratio{
                  formula = branch-misses / branch-instructions
                  desc = branch misprediction ratio
          }
  }

You get the idea.  Maybe substitute "ratio":with "formula". Then allow
such a ratio/formula to be used just like a normal event, perhaps with
a special suffix/prefix to designate it.  This should then also mark
the events as part of a group so that the underlying counters are
scheduled in together.
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