From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751665AbdCCGY0 (ORCPT ); Fri, 3 Mar 2017 01:24:26 -0500 Received: from LGEAMRELO13.lge.com ([156.147.23.53]:53103 "EHLO lgeamrelo13.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751610AbdCCGYY (ORCPT ); Fri, 3 Mar 2017 01:24:24 -0500 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: namhyung@kernel.org X-Original-SENDERIP: 10.177.227.17 X-Original-MAILFROM: namhyung@kernel.org Date: Fri, 3 Mar 2017 14:09:20 +0900 From: Namhyung Kim To: Peter Zijlstra Cc: Taeung Song , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Jiri Olsa , Ingo Molnar , Wang Nan , Masami Hiramatsu , Jiri Olsa , kernel-team@lge.com Subject: Re: [PATCH v2 2/3] perf annotate: Introduce the new source code view Message-ID: <20170303050920.GK30710@sejong> References: <1488311993-15124-1-git-send-email-treeze.taeung@gmail.com> <1488311993-15124-3-git-send-email-treeze.taeung@gmail.com> <20170301135805.GB2690@danjae.aot.lge.com> <20170301140833.GG6515@twins.programming.kicks-ass.net> <20170301142133.GC2690@danjae.aot.lge.com> <20170301143011.GI6515@twins.programming.kicks-ass.net> <20170301145639.GA3370@danjae.aot.lge.com> <20170301150746.GJ6515@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170301150746.GJ6515@twins.programming.kicks-ass.net> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On Wed, Mar 01, 2017 at 04:07:46PM +0100, Peter Zijlstra wrote: > On Wed, Mar 01, 2017 at 11:56:39PM +0900, Namhyung Kim wrote: > > > It's a kind of user experience issue. We provide the asm-only and > > asm+source annotation, and I think it'd be nice to add source-only > > option. And I remember that it was requested some time ago.. > > Thing is, an optimizing compiler -- that same beast that ensures your > objdump -S output is such a garbled mess -- can generate code that > becomes very hard to relate to the original source code. I understand that. Maybe it's not 100% accurate, but it still has valuable information. And I think the source-only view can give more readable outputs using the info. Also I guess many developers already aware of the effect of optimizing compilers. > > I'm really sceptical the source line only view is very useful; maybe if > you build with -O0, but then, if you do that you're not bothered with > performance. Even with an optimizing compiler, it can be helpful to overview which parts of the code are bottlenecks IMHO. After that, one can see the asm to identify the problem deeply, if needed. Thanks, Namhyung