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

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Date:	Tue, 11 Aug 2015 15:54:37 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Andi Kleen <ak@...ux.intel.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 06:38:05AM -0700, Andi Kleen wrote:
> 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.

how about existing scale attributes, like in rapl code

jirka
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