From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752367AbcDZQih (ORCPT ); Tue, 26 Apr 2016 12:38:37 -0400 Received: from merlin.infradead.org ([205.233.59.134]:44467 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751704AbcDZQig (ORCPT ); Tue, 26 Apr 2016 12:38:36 -0400 Date: Tue, 26 Apr 2016 18:38:28 +0200 From: Peter Zijlstra To: Arnaldo Carvalho de Melo Cc: Stephane Eranian , David Ahern , Milian Wolff , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Ingo Molnar , Namhyung Kim , Linux Kernel Mailing List Subject: Re: LBR callchains from tracepoints Message-ID: <20160426163828.GA3448@twins.programming.kicks-ass.net> References: <57157965.4020506@gmail.com> <1704384.MQzPvE4Oa5@milian-kdab2> <20160426010358.GD16708@kernel.org> <20160426012431.GE16708@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160426012431.GE16708@kernel.org> 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 Mon, Apr 25, 2016 at 10:24:31PM -0300, Arnaldo Carvalho de Melo wrote: > Em Mon, Apr 25, 2016 at 10:03:58PM -0300, Arnaldo Carvalho de Melo escreveu: > > I now need to continue investigation why this doesn't seem to work from > > tracepoints... > > Bummer, the changeset (at the end of this message) hasn't any > explanation, is this really impossible? I.e. LBR callstacks from > tracepoints? Even if we set perf_event_attr.exclude_callchain_kernel? Could maybe be done, but its tricky to implement as the LBR is managed by the hardware PMU and tracepoints are a software PMU, so we need to then somehow frob with cross-pmu resources, in a very arch specific way. And programmability of the hardware PMU will then depend on events outside of it. All rather icky.