linux-kernel - Re: [RFC/PATCHSET 00/15] perf report: Add support to accumulate hist periods

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Date:	Mon, 29 Oct 2012 14:36:01 -0700
From:	Arun Sharma <asharma@...com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [RFC/PATCHSET 00/15] perf report: Add support to accumulate hist
 periods

On 10/29/12 12:08 PM, Peter Zijlstra wrote:

> Right, so I tried this and I would expect the callchains to be inverted
> too, so that when I expand say 'c' I would see that 'c' calls 'b' for
> 100% which calls 'a' for 100%.
>
> Instead I get the regular callchains, expanding 'c' gives me main calls
> it for 100%.
>
> Adding -G (invert callchains) doesn't make it better, in that case, when
> I expand 'c' we start at '__libc_start_main' instead of 'c'.
>
> Is there anything I'm missing?
>

Sounds like a reasonable expectation.

I tested mainly:

perf report --cumulate  -g graph,100,callee

to find the functions with a large amount of CPU time underneath. Then 
examined the callgraph without --cumulate. But yeah - it'd be nice to be 
able to do both in a single invocation.

Also, when callgraphs are displayed, the percentages are off (> 100%). 
Namhyung probably needs to use he->stat_acc->period in a few places as 
the denominator instead of he->period.

  -Arun
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