linux-kernel - Re: [PATCH 2/2] perf: Add a new sort order: SORT

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Date:	Tue, 13 Mar 2012 14:44:00 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arun Sharma <asharma@...com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Tom Zanussi <tzanussi@...il.com>,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 2/2] perf: Add a new sort order: SORT_INCLUSIVE

On Thu, Mar 08, 2012 at 10:22:26AM -0800, Arun Sharma wrote:
> On Thu, Mar 08, 2012 at 04:39:36PM +0100, Frederic Weisbecker wrote:
> > 
> > I don't yet understand the point of this.
> > 
> > Imagine those three hists:
> > 
> > a -> b -> c
> > a -> b -> d
> > a-> e -> f
> > 
> > The fractal inverted mode (-G) will report this:
> > 
> > a--
> >   |
> >   ----- b
> >   |     |
> >   |     -----c
> >   |     |
> >   |     -----d
> >   |
> >   ----- e
> >         |
> >         -----f
> > 
> 
> Please see the test program attached. It has only two paths from main()
> to c(). But for this discussion, imagine a callgraph with 10 different
> paths.

Ok that makes sense.

Thanks.

> 
> With -G, c() appears 10 times in the callgraph and the user is required
> to manually sum up the samples to realize that the callgraph under c()
> is very expensive.
> 
> With -s inclusive, c() will show up at the very top after main().
> 
>  -Arun
> 
> #include <stdio.h>
> 
> int sum = 0;
> 
> #define LOOP(n)                                         \
>         {                                               \
>                 int j;                                  \
>                 for (j = 0; j < 10000; j++) {           \
>                         sum += j;                       \
>                 }                                       \
>         }
> 
> int f()
> {
>         LOOP(100);
> }
> 
> int d()
> {
>         LOOP(100);
>         f();
> }
> 
> int e()
> {
> 	LOOP(100);
> 	f();
> }
> 
> int c()
> {
> 	LOOP(100);
> 	d();
> 	LOOP(100);
> 	e();
> }
> 
> int b() 
> {
> 	LOOP(70);
> 	c();
> }
> 
> int a() 
> {
> 	LOOP(30);
> 	c();
> }
> 
> int main()
> {
> 	int i;
> 	for (i = 0; i < 10000; i++) {
> 		a();
> 		b();
> 	}
> }
> 
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