linux-kernel - Re: [PATCH 2/9] perf, tools, stat: Support up-scaling of events

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Date:	Tue, 11 Aug 2015 06:38:05 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, acme@...nel.org,
	jolsa@...nel.org, linux-kernel@...r.kernel.org, eranian@...gle.com,
	namhyung@...nel.org, peterz@...radead.org, mingo@...nel.org
Subject: Re: [PATCH 2/9] perf, tools, stat: Support up-scaling of events

On Tue, Aug 11, 2015 at 03:25:32PM +0200, Jiri Olsa wrote:
> On Fri, Aug 07, 2015 at 06:06:18PM -0700, Andi Kleen wrote:
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > TopDown needs to multiply events by constants (for example
> > the CPU Pipeline Width) to get the correct results.
> > The kernel needs to export this factor.
> > 
> > Today *.scale is only used to scale down metrics (divide), for example
> > to scale bytes to MB.
> > 
> > Repurpose negative scale to mean scaling up, that is multiplying.
> > Implement the code for this in perf stat.
> > 
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > ---
> >  tools/perf/builtin-stat.c | 27 +++++++++++++++++++--------
> >  1 file changed, 19 insertions(+), 8 deletions(-)
> > 
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index ea5298a..2590c75 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -179,6 +179,17 @@ static inline int nsec_counter(struct perf_evsel *evsel)
> >  	return 0;
> >  }
> >  
> > +static double scale_val(struct perf_evsel *counter, u64 val)
> > +{
> > +	double uval = val;
> > +
> > +	if (counter->scale < 0)
> > +		uval = val * (-counter->scale);
> > +	else if (counter->scale)
> > +		uval = val / counter->scale;
> 
> hum, do you change the scale logic? the current scale > 0 works like:
> 
> 	uval = val * counter->scale;

Yes I define negative scales to mean "multiply by" See the description of the kernel
patch for more details.

-Andi


-- 
ak@...ux.intel.com -- Speaking for myself only
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