From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754605AbaILMHp (ORCPT ); Fri, 12 Sep 2014 08:07:45 -0400 Received: from mail.kernel.org ([198.145.19.201]:42189 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754199AbaILMHn (ORCPT ); Fri, 12 Sep 2014 08:07:43 -0400 Date: Fri, 12 Sep 2014 09:07:27 -0300 From: Arnaldo Carvalho de Melo To: Namhyung Kim Cc: Mike Galbraith , LKML Subject: Re: perf top -g -U --sort=symbol --children == lalalalala? Message-ID: <20140912120727.GD1801@kernel.org> References: <1410263641.15383.8.camel@marge.simpson.net> <20140909133737.GK2773@kernel.org> <1410439392.20184.17.camel@marge.simpson.net> <20140911134338.GE10158@kernel.org> <878ulpmhbt.fsf@sejong.aot.lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <878ulpmhbt.fsf@sejong.aot.lge.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Sep 12, 2014 at 04:24:54PM +0900, Namhyung Kim escreveu: > Hi Arnaldo and Mike, > > On Thu, 11 Sep 2014 10:43:38 -0300, Arnaldo Carvalho de Melo wrote: > > 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 > >> > 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. > > So the problem is that why it turned on --children option by default, > right? I thought you mentioned there's a problem with -U option and I > couldn't figure out what it is. Yeah, at that point I thought the problem was that -U wasn't honoured in --children mode, but after I looked again at the output, it was all [k], so I thought that it was something else but didn't got back to the thread :-) > >> > >> 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 ;-) > > Now I have three persion yell at me for this change. :) Hey, its not "yell" or something, I just think that it is under documented, and hey, perf is world renowned for being under developed, we don't need any further efforts in that area :-P > When this change was developping, Ingo said it'd be better if it looks > like output of sysprof as it's more popular for most (userland?) guys. > You can see the discussion in the following links: > > https://lkml.org/lkml/2013/10/31/97 > https://lkml.org/lkml/2013/11/1/85 > > The children field is a cumulative total overhead (for its all > children/callee) so sum of them would be more than 100%. And as Ingo > requested it sorts the output entries using children overhead so that > one can easily see higher level view of performance bottle-neck. yeah, yeah, but please have all this in the documentation :-) - Arnaldo