linux-kernel - Re: [PATCH 09/10] perf, tools: Support DividedBy header in JSON event list

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Date:   Mon, 17 Oct 2016 19:43:12 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     acme@...nel.org, jolsa@...nel.org, sukadev@...ux.vnet.ibm.com,
        eranian@...gle.com, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 09/10] perf, tools: Support DividedBy header in JSON
 event list

On Mon, Oct 17, 2016 at 09:27:54AM -0700, Andi Kleen wrote:
> On Mon, Oct 17, 2016 at 01:44:43PM +0200, Jiri Olsa wrote:
> > On Thu, Oct 13, 2016 at 02:15:31PM -0700, Andi Kleen wrote:
> > > From: Andi Kleen <ak@...ux.intel.com>
> > > 
> > > Add support for parsing the DividedBy header in the JSON event lists and
> > > storing them in the alias structure.
> > 
> > I wish you'd add JSON tags always one by one as you did in here ;-)
> > 
> > however Ithink we'll need more info here:
> >   - what's the value?
> >   - what's it going to be used for?
> 
> That's all described in the next patch. But I can copy the description.
> 
> >   - looks like formula stuff, why post processing via python/perl can't be used in this case?
> 
> It would be fairly complicated to interface that with event lists, and
> also still wouldn't work with standard perf stat. 
> 
> DividedBy already covers the majority of interesting cases and fits
> nicely with the existing frame work. If we wanted more complex
> formulas something with python would be probably needed, but I don't see
> the need yet.

so..

- you put 'DividedBy' into JSON event's defition any further
  explanation how or why the format we use for event defs will
  be used now used to describe ratios

- then you force perf stat to merge together all 'same' uncore events
  to get just one number..

- then you display that ratio (just the number) in perf stat metrics output
  without any explanation or description

I dont see that as a nicely fit, more like hack

please let's go first to discuss the DividedBy being included
in JSON defs, which is fragile topic to begin with

thanks,
jirka