From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753166AbbJUBVp (ORCPT ); Tue, 20 Oct 2015 21:21:45 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:34733 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753083AbbJUBVo (ORCPT ); Tue, 20 Oct 2015 21:21:44 -0400 Date: Wed, 21 Oct 2015 10:21:36 +0900 From: Namhyung Kim To: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker , Chandler Carruth , Brendan Gregg , Ingo Molnar , LKML , Adrian Hunter , Borislav Petkov , David Ahern , Jiri Olsa , Stephane Eranian , Wang Nan , Taeung Song Subject: Re: [PATCH 13/16] perf callchain: Switch default to 'graph,0.5,caller' Message-ID: <20151021012136.GA628@sejong> References: <20151009215626.GM14409@kernel.org> <20151009222504.GN14409@kernel.org> <20151020120033.GB5119@kernel.org> <20151020121948.GA29289@lerouge> <20151020130651.GC5119@kernel.org> <20151020172114.GB29289@lerouge> <20151020184404.GK5119@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20151020184404.GK5119@kernel.org> 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 Arnaldo, On Tue, Oct 20, 2015 at 03:44:04PM -0300, Arnaldo Carvalho de Melo wrote: > Em Tue, Oct 20, 2015 at 07:21:16PM +0200, Frederic Weisbecker escreveu: > > 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. > > And I noticed some other shortcoming of this ordering (caller) the stack > closer to userspace in a typical perf.data with callchains (perf record > -g) can have bogus addresses (-fomit-frame-pointer) :-\ Maybe we need to add an option to ignore unresolved callchains? > > > > > 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. > > That is why I put the "anedoctaly" :-) > > > > > > Ingo, what do you think? > > > > > > What about providing a hotkey, in the tui, to toggle caller/callee > > > views, and another hotkey to save that in ~/.perfconfig so that becomes > > > the new default? > > > That means rebuilding the whole tree, it might be costly and events need to > > be processed again. > > I never tried to reimplement that with going to/from caller/caller in > mind, should do at some point, but yeah, reprocessing all entries can be > way costly. Right. Anyway it seems useful to update config dynamically. I really need to take a look at Taeung's config patchset.. > > > > In the --stdio mode we need to add a warning in the first lines, > > > something like: > > > > > > # This is caller (or callee) based, please use --callchain ... to change it > > > > > > One way or the other people will disagree, so making it easy to switch > > > to the preferred way would be nice to have? > > > > Agreed. > > I'll probably revert this change in default and provide some way to > change it dynamically, just waiting a some more time for more comments. Agreed. Thanks, Namhyung