From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751998AbdCAOaS (ORCPT ); Wed, 1 Mar 2017 09:30:18 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:44716 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751150AbdCAOaQ (ORCPT ); Wed, 1 Mar 2017 09:30:16 -0500 Date: Wed, 1 Mar 2017 15:30:11 +0100 From: Peter Zijlstra To: Namhyung Kim Cc: Taeung Song , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, Jiri Olsa , Ingo Molnar , Wang Nan , Masami Hiramatsu , Jiri Olsa Subject: Re: [PATCH v2 2/3] perf annotate: Introduce the new source code view Message-ID: <20170301143011.GI6515@twins.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170301142133.GC2690@danjae.aot.lge.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 01, 2017 at 11:21:33PM +0900, Namhyung Kim wrote: > > What's the point of source-only? You can't even see what it is that is > > expensive. > > ??? >>From a line like: a = b ? ptr->c : 0; How do you tell what it is that causes the problem, the branch miss or the pointer deref? Typically looking at the asm this is fairly clear; even without recording with more specific events. > This is to show source code + overhead (for each line). People can > see which line of their source is expensive. I think it's way more > intuitive for most developers.. And how pray are you going to write better code if you have no clue what the problem is? I'm really wondering how you can even think about performance if you're scared of asm.