Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755387AbaKEQ3n (ORCPT ); Wed, 5 Nov 2014 11:29:43 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:42781 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755329AbaKEQ3l (ORCPT ); Wed, 5 Nov 2014 11:29:41 -0500 Date: Wed, 5 Nov 2014 17:29:32 +0100 From: Peter Zijlstra To: "Liang, Kan" Cc: Stephane Eranian , LKML , "mingo@redhat.com" , Paul Mackerras , Arnaldo Carvalho de Melo , Jiri Olsa , "ak@linux.intel.com" Subject: Re: [PATCH V7 13/17] perf, x86: enable LBR callstack when recording callchain Message-ID: <20141105162932.GX3337@twins.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077016540B7@SHSMSX103.ccr.corp.intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- 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/