linux-kernel - Re: [PATCH v3 3/3] perf, tools, script: Allow computing metrics in perf script

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Date:   Mon, 20 Nov 2017 16:53:45 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Andi Kleen <andi@...stfloor.org>
Cc:     acme@...nel.org, jolsa@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v3 3/3] perf, tools, script: Allow computing metrics in
 perf script

On Mon, Nov 20, 2017 at 07:35:05AM -0800, Andi Kleen wrote:
> On Mon, Nov 20, 2017 at 10:04:19AM +0100, Jiri Olsa wrote:
> > On Fri, Nov 17, 2017 at 01:43:00PM -0800, Andi Kleen wrote:
> > 
> > SNIP
> > 
> > > ---
> > >  tools/perf/Documentation/perf-script.txt | 10 +++-
> > >  tools/perf/builtin-script.c              | 97 +++++++++++++++++++++++++++++++-
> > >  tools/perf/util/metricgroup.c            |  4 ++
> > >  3 files changed, 108 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
> > > index 2811fcf684cb..974ceb12c7f3 100644
> > > --- a/tools/perf/Documentation/perf-script.txt
> > > +++ b/tools/perf/Documentation/perf-script.txt
> > > @@ -117,7 +117,7 @@ OPTIONS
> > >          Comma separated list of fields to print. Options are:
> > >          comm, tid, pid, time, cpu, event, trace, ip, sym, dso, addr, symoff,
> > >          srcline, period, iregs, uregs, brstack, brstacksym, flags, bpf-output, brstackinsn,
> > > -        brstackoff, callindent, insn, insnlen, synth, phys_addr.
> > > +	brstackoff, callindent, insn, insnlen, synth, phys_addr, metric.
> > >          Field list can be prepended with the type, trace, sw or hw,
> > >          to indicate to which event type the field list applies.
> > >          e.g., -F sw:comm,tid,time,ip,sym  and -F trace:time,cpu,trace
> > > @@ -217,6 +217,14 @@ OPTIONS
> > >  
> > >  	The brstackoff field will print an offset into a specific dso/binary.
> > >  
> > > +	With the metric option perf script can compute metrics for
> > > +	sampling periods, similar to perf stat. This requires
> > > +	specifying a group with multiple metrics with the :S option
> > > +	for perf record. perf will sample on the first event, and
> > > +	compute metrics for all the events in the group. Please note
> > > +	that the metric computed is averaged over the whole sampling
> > > +	period, not just for the sample point.
> > 
> > hum, is it? I see you call perf_stat__reset_shadow_stats for every
> > group start.. which I'd think means you see metric for current
> > leader sample point
> 
> Yes it is.
> 
> It's for the complete sampling period because it is computed
> over the delta from the last sample to the previous sample.
> 
> There isn't really a metric at a point, it is always over a interval.

agreed, it's the count we meassured from the last sample.. but the
'averaged' word above implies to me we compute some average over the
'sampling' period, which we dont do

jirka