linux-kernel - Re: Add top down metrics to perf stat v2

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Date:	Thu, 17 Dec 2015 15:01:23 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: Add top down metrics to perf stat v2

On Thu, Dec 17, 2015 at 02:27:58AM -0800, Stephane Eranian wrote:
> > S0-C1           2      4175583320.00      topdown-slots-retired                                         (100.00%)
> > S0-C1           2         1743329246      topdown-recovery-bubbles  #    22.22% bad speculation         (100.00%)
> > S0-C1           2      6138901193.50      topdown-slots-issued      #    46.99% backend bound
> >
> I don't see how this output could be very useful. What matters is the
> percentage in the comments
> and not so much the raw counts because what is the unit? Same remark
> holds for the percentage.
> I think you need to explain or show that this is % of issue slots and
> not cycles.

The events already say slots, not cycles. Except for recovery-bubbles. Could add
-slots there too if you think it's helpful, although it would make the
name very long and may not fit into the column anymore.

> 
> >        1.535832673 seconds time elapsed
> >
> > $ perf stat --topdown --topdown --metric-only -I 100 ./BC1s
> 
> When I tried from your git tree the --metric-only option was not recognized.

See below.
> 
> >      0.100576098 frontend bound           retiring                 bad speculation          backend bound
> >      0.100576098     8.83%                  48.93%                  35.24%                   7.00%
> >      0.200800845     8.84%                  48.49%                  35.53%                   7.13%
> >      0.300905983     8.73%                  48.64%                  35.58%                   7.05%
> > ...
> >
> This kind of output is more meaningful and clearer for end-users based
> on my experience
> and you'd like it per-core possibly.

Yes --metric-only is a lot clearer.

per-core is supported and automatically enabled with SMT on.

> > Full tree available in
> > git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc perf/top-down-11
> 
> That is in the top-down-2 branch instead, I think.

Sorry, typo

The correct branch is perf/top-down-10

I also updated it now with the latest review feedback changes.

top-down-2 is an really old branch that indeed didn't have metric-only.

-Andi

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