linux-kernel - Re: [PATCH 1/4] perf, tools: Add support for prepending LBRs to the callstack

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Message-ID: <20140111153614.GC1131@krava.brq.redhat.com>
Date:	Sat, 11 Jan 2014 16:36:14 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	acme@...radead.org, linux-kernel@...r.kernel.org,
	namhyung@...nel.org, eranian@...gle.com, fweisbec@...il.com,
	mingo@...nel.org, adrian.hunter@...el.com, dsahern@...il.com,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/4] perf, tools: Add support for prepending LBRs to the
 callstack

On Fri, Jan 10, 2014 at 04:32:03AM -0800, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> I never found the default LBR display mode which generates histograms
> of individual branches particularly useful.
> 
> This implements an alternative mode that creates histograms over complete
> branch traces, instead of individual branches, similar to how normal
> callgraphs are handled. This is done by putting it in
> front of the normal callgraph and then using the normal callgraph
> histogram infrastructure to unify them.
> 
> This way in complex functions we can understand the control flow
> that lead to a particular sample.
> 
> The default output is unchanged.
> 
> This is only implemented in perf report, no change to record
> or anywhere else.
> 
> This adds the basic code to report:
> - add a new "branch" option to the -g option parser to enable this mode
> - when the flag is set include the LBR into the callstack in machine.c.
> The rest of the history code is unchanged and doesn't know the difference
> between LBR entry and normal call entry.

sounds like nice idea, but I could not get the patchset applied
on acme's perf/core

jirka
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