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

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Date:	Thu, 17 Jan 2013 17:05:16 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Ulrich Drepper <drepper@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	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 Thu, Jan 17, 2013 at 10:03:32AM +0900, Namhyung Kim wrote:
> Hi,
> 
> On Wed, 16 Jan 2013 10:12:14 -0500, Ulrich Drepper wrote:
> > On Wed, Jan 16, 2013 at 9:25 AM, Jiri Olsa <jolsa@...hat.com> wrote:
> >> I was thinking having config files (global and arch specific)
> >> comming with perf having predefined formulas.
> >
> > All the more reason to not mention the file name or really any source
> > for the definition of the formula in the name,
> >
> >
> >> 1)  -e 'ratio/branch-rate/'  # special event class
> >> 2)  -e 'ratio-branch-rate'   # 'ratio-' prefix
> >> 3)  -e cpu/branch-rate/      # handled like aliases, ratio name would need to be unique
> >>   ... ?
> >
> > I think 3 is the most extensible.  Perhaps use the syntax used in
> > other places.  We have these :u suffixes etc.  Perhaps have :r or :R
> > or whatever.
> 
> I don't think it's a good idea.  The ':r' syntax is for modifiers to the
> existing events so it doesn't match to this case IMHO.
> 
> I prefer a special event class like 1 since it's possible to include
> non-cpu events to a ratio/formular.  In that case, using 'cpu' in the
> PMU name can be misleading.
> 
> >
> > Given the other comments, we might want to avoid right away "ratio".
> > If the mechanism is generalized it could be used to express "counter1
> > - counter2" for events which cannot be expressed with a single counter
> > but are not really ratios.
> 
> Agreed.  Looks like "formular" is better.

agreed, I think I wouldn't touch modifiers for this
also, 'ratio' is not good choice, formula seems better

jirka
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