Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754508AbaKRN51 (ORCPT ); Tue, 18 Nov 2014 08:57:27 -0500 Received: from mga14.intel.com ([192.55.52.115]:22851 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752212AbaKRN5Z convert rfc822-to-8bit (ORCPT ); Tue, 18 Nov 2014 08:57:25 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,410,1413270000"; d="scan'208";a="624236433" From: "Liang, Kan" To: Namhyung Kim 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 Thread-Topic: [PATCH V3 1/3] perf tools: enable LBR call stack support Thread-Index: AQHQAvQ+8txQ4tAb5U2YHX9AXb/4V5xmZw8g Date: Tue, 18 Nov 2014 13:57:12 +0000 Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077016711E8@SHSMSX103.ccr.corp.intel.com> References: <1415972652-17310-1-git-send-email-kan.liang@intel.com> <1415972652-17310-2-git-send-email-kan.liang@intel.com> <87ppclqcif.fsf@sejong.aot.lge.com> In-Reply-To: <87ppclqcif.fsf@sejong.aot.lge.com> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 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? 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.. The kernel will handle it. EOPNOTSUPP will be return if there is no LBR Call stack support. Thanks, Kan > > Thanks, > Namhyung -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/