linux-kernel - Re: perf top -g -U --sort=symbol --children == lalalalala?

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Date:	Thu, 11 Sep 2014 10:43:38 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Namhyung Kim <namhyung@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: perf top -g -U --sort=symbol --children == lalalalala?

Em Thu, Sep 11, 2014 at 02:43:12PM +0200, Mike Galbraith escreveu:
> On Thu, 2014-09-11 at 17:09 +0900, Namhyung Kim wrote: 
> > On Tue, Sep 9, 2014 at 10:37 PM, Arnaldo Carvalho de Melo
> > <acme@...stprotocols.net> wrote:
> > > Em Tue, Sep 09, 2014 at 01:54:01PM +0200, Mike Galbraith escreveu:
> > >> Seems the now default on --children thingy doesn't like -U much.
> > >
> > > Namhyung, can you please take a look at this?
> > 
> > So what is the problem here?
> 
> Well, if you don't see anything wrong, I guess nothing at all.

:-)

I think that when we decide that it is so better to change defaults like
we did this time, we should be required to add a big fat warning (a
--tui popup, use the first lines on --stdio, etc) about why the default
was changed and allow quick, easy opt out, restoring previous behaviour
after the user, being warned, knows what to expect, tries it, and then
is in a better position to decide if keeping the new default is what is
desired.

- Arnaldo
 
> > >> Samples: 5K of event 'cycles', Event count (approx.): 2268660922
> > >>   Children      Self  Symbol
> > >> +   46.42%     0.04%  [k] system_call_fastpath
 
> I'll just turn it off until I figure out what cool stuff this is telling
> me. why that symbol becomes the number one hit, and why total% > 100.
 
> To me, it looks like top smoked it's breakfast, went to lala land ;-)

Yeah, its confusing, I'll let Namhyung explain it ;-)

:-)

- Arnaldo
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