linux-kernel - Re: [PATCH v2 2/3] perf annotate: Introduce the new source code view

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Date:   Wed, 1 Mar 2017 16:07:46 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Taeung Song <treeze.taeung@...il.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Wang Nan <wangnan0@...wei.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, kernel-team@....com
Subject: Re: [PATCH v2 2/3] perf annotate: Introduce the new source code view

On Wed, Mar 01, 2017 at 11:56:39PM +0900, Namhyung Kim wrote:

> It's a kind of user experience issue.  We provide the asm-only and
> asm+source annotation, and I think it'd be nice to add source-only
> option.  And I remember that it was requested some time ago..

Thing is, an optimizing compiler -- that same beast that ensures your
objdump -S output is such a garbled mess -- can generate code that
becomes very hard to relate to the original source code.

I'm really sceptical the source line only view is very useful; maybe if
you build with -O0, but then, if you do that you're not bothered with
performance.