From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753811AbbJUIJ3 (ORCPT ); Wed, 21 Oct 2015 04:09:29 -0400 Received: from mail-pa0-f49.google.com ([209.85.220.49]:35702 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753636AbbJUIJP (ORCPT ); Wed, 21 Oct 2015 04:09:15 -0400 Date: Wed, 21 Oct 2015 17:09:08 +0900 From: Namhyung Kim To: Frederic Weisbecker Cc: Arnaldo Carvalho de Melo , Chandler Carruth , Brendan Gregg , Ingo Molnar , LKML , Adrian Hunter , Borislav Petkov , David Ahern , Jiri Olsa , Stephane Eranian , Wang Nan Subject: Re: [PATCH 13/16] perf callchain: Switch default to 'graph,0.5,caller' Message-ID: <20151021080908.GI628@sejong> References: <1444079018-31421-14-git-send-email-acme@kernel.org> <20151009215626.GM14409@kernel.org> <20151009222504.GN14409@kernel.org> <20151020120033.GB5119@kernel.org> <20151020121948.GA29289@lerouge> <20151020130651.GC5119@kernel.org> <20151020172114.GB29289@lerouge> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20151020172114.GB29289@lerouge> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Frederic, On Tue, Oct 20, 2015 at 07:21:16PM +0200, Frederic Weisbecker wrote: > On Tue, Oct 20, 2015 at 10:06:51AM -0300, Arnaldo Carvalho de Melo wrote: > > Em Tue, Oct 20, 2015 at 02:19:50PM +0200, Frederic Weisbecker escreveu: > > > On Tue, Oct 20, 2015 at 09:00:34AM -0300, Arnaldo Carvalho de Melo wrote: > > > > Em Mon, Oct 19, 2015 at 05:16:53PM -0700, Brendan Gregg escreveu: > > > > So are you advocating different defaults, one for --stdio (callee), > > > > another for --tui, --gtk (caller)? > > > > > > This is all configurable via ~/.perfconfig :-\ > > > > > > Indeed, finding a default that is deemed adequate for most people is, > > > > ho-hum, difficult 8-) > > > > > Most uses I've seen on LKML by the past involved callee because people > > > mostly look at the precise point where a performance issue is. > > > > A good chunk of that was because that was the default? > > I doubt it. When you need to find the culprit of a syscall of IRQ performance issue, > you don't care much to see __libc_start_main() / main() on the top of your callchain. > > > > > > IMHO changing that order is not a good idea. Unless many users complained > > > about it. > > > > Perhaps there are not that many users of callchains because the default > > is not what they're used to see? > > > > Motivation for the change came from a video from Chandler, that > > resurfaced the callchain default issue, Chandler? > > > > Anedoctally, he tweeted about it and people seemed to like it. > > Well, I would prefer to hear from regular users than random twitter followers. > I could be wrong so lets ask some users first. Just a question. Do you often use --children and/or '--g caller' options? I guess that for most kernel developers, --children is not that useful as you said. But I think it can be useful for many userspace developers and with '-g caller' it can be even more useful. :) When '-g caller' is used, the callchains shown in a (self) entry are less important IMHO. However callchains in entries generated by --children will show which functions are called by the entry (since it's reversed!) and will be more important. Thanks, Namhyung