linux-kernel - Re: [PATCH v7 1/5] perf report: properly handle branch count in match

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Date:   Mon, 23 Oct 2017 08:15:11 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Milian Wolff <milian.wolff@...b.com>
Cc:     acme@...nel.org, jolsa@...nel.org, namhyung@...nel.org,
        Linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Yao Jin <yao.jin@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH v7 1/5] perf report: properly handle branch count in match_chain

Milian Wolff <milian.wolff@...b.com> writes:
>
> perf record -b --call-graph dwarf <some binary>
> perf report --branch-history --no-children --stdio
>
> I see predicted and iter values as before, so I think nothing is breaking. But 
> I'm somewhat unsure. Can someone paste an example source code and the perf 
> commands to get some meaningful avg_cycles? Or does this depend on a newer 
> Intel CPU? I have currently only a Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz 
> available.

Branch cycles requires at least a Skylake or Goldmont CPU, so yes.

For testing on other systems you can fake them however with some variant
of this patch

http://lkml.iu.edu/hypermail//linux/kernel/1505.1/01135.html

-Andi