From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752917AbaKRFyw (ORCPT ); Tue, 18 Nov 2014 00:54:52 -0500 Received: from lgeamrelo01.lge.com ([156.147.1.125]:34707 "EHLO lgeamrelo01.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752419AbaKRFyu (ORCPT ); Tue, 18 Nov 2014 00:54:50 -0500 X-Original-SENDERIP: 10.177.222.235 X-Original-MAILFROM: namhyung@gmail.com From: Namhyung Kim To: kan.liang@intel.com Cc: acme@kernel.org, jolsa@redhat.com, a.p.zijlstra@chello.nl, eranian@google.com, linux-kernel@vger.kernel.org, mingo@redhat.com, paulus@samba.org, ak@linux.intel.com Subject: Re: [PATCH V3 1/3] perf tools: enable LBR call stack support References: <1415972652-17310-1-git-send-email-kan.liang@intel.com> <1415972652-17310-2-git-send-email-kan.liang@intel.com> Date: Tue, 18 Nov 2014 14:54:48 +0900 In-Reply-To: <1415972652-17310-2-git-send-email-kan.liang@intel.com> (kan liang's message of "Fri, 14 Nov 2014 08:44:10 -0500") Message-ID: <87ppclqcif.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 14 Nov 2014 08:44:10 -0500, kan liang wrote: > From: Kan Liang > > Currently, there are two call chain recording options, fp and dwarf. > Haswell has a new feature that utilizes the existing LBR facility to > record call chains. So it provides the third options to record call > chain. This patch enables the lbr call stack support. > > LBR call stack has some limitations. It reuses current LBR facility, so > LBR call stack and branch record can not be enabled at the same time. It > is only available for user callchain. > However, LBR call stack can work on the user app which doesn't have > frame-pointer or dwarf debug info compiled. It is a good alternative > when nothing else works. So this is only for Haswell or later, right? What if user gives it to the other CPUs - is it fail or ignore silently? I think we need to warn user about it more kindly.. Thanks, Namhyung