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

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Message-ID: <1895125.rrirNAUR4a@agathebauer>
Date:   Thu, 19 Oct 2017 13:42:18 +0200
From:   Milian Wolff <milian.wolff@...b.com>
To:     acme@...nel.org
Cc:     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

On Donnerstag, 19. Oktober 2017 13:38:32 CEST Milian Wolff wrote:
> Some of the code paths I introduced before returned too early
> without running the code to handle a node's branch count.
> By refactoring match_chain to only have one exit point, this
> can be remedied.

Note: I tested this with some of the code I have available, but I'm unsure I'm 
doing it right. On my system, I never get avg_cycles != 0. I tried:

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.

Cheers

-- 
Milian Wolff | milian.wolff@...b.com | Senior Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts