Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752010AbaKERz0 (ORCPT ); Wed, 5 Nov 2014 12:55:26 -0500 Received: from mga09.intel.com ([134.134.136.24]:55118 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751110AbaKERzW (ORCPT ); Wed, 5 Nov 2014 12:55:22 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,321,1413270000"; d="scan'208";a="632070357" Date: Wed, 5 Nov 2014 09:52:05 -0800 From: Andi Kleen To: Peter Zijlstra Cc: "Liang, Kan" , Stephane Eranian , LKML , "mingo@redhat.com" , Paul Mackerras , Arnaldo Carvalho de Melo , Jiri Olsa Subject: Re: [PATCH V7 13/17] perf, x86: enable LBR callstack when recording callchain Message-ID: <20141105175205.GP3274@tassilo.jf.intel.com> References: <1415156173-10035-1-git-send-email-kan.liang@intel.com> <1415156173-10035-14-git-send-email-kan.liang@intel.com> <20141105092145.GP10501@worktop.programming.kicks-ass.net> <20141105104359.GP3337@twins.programming.kicks-ass.net> <20141105124926.GS3337@twins.programming.kicks-ass.net> <37D7C6CF3E00A74B8858931C1DB2F077016540B7@SHSMSX103.ccr.corp.intel.com> <20141105162932.GX3337@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141105162932.GX3337@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 05, 2014 at 05:29:32PM +0100, Peter Zijlstra wrote: > On Wed, Nov 05, 2014 at 03:53:34PM +0000, Liang, Kan wrote: > > > I don't think it would be very hard to modify the patch set to make that 3rd > > > mode visible. Just need to make that new PERF_RECORD_* type visible to > > > user and modify the compatibility checks. > > > > It's not hard. But LBR is not an independent callchain options. It's better to be > > a supplement of FP. Otherwise, it may confuse the user. He enables the > > BRANCH_CALL_STACK, but the data is partly or even not at all from hardware. > > What the user sees is up to userspace. It should not be forced by the > kernel/user interface. The original idea was to abstract it inside the kernel. Unlike dwarf the LBR callstack is simple enough that it can be easily abstracted. If you don't want to do that yes then handling it in the user tools is the right way. -Andi -- ak@linux.intel.com -- Speaking for myself only -- 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/