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

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Message-ID: <87pq14lixn.fsf@sejong.aot.lge.com>
Date:	Thu, 17 Jan 2013 10:03:32 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Ulrich Drepper <drepper@...il.com>
Cc:	Jiri Olsa <jolsa@...hat.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

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.

Thanks,
Namhyung
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