From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933327Ab1LFLE1 (ORCPT ); Tue, 6 Dec 2011 06:04:27 -0500 Received: from merlin.infradead.org ([205.233.59.134]:43982 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933153Ab1LFLEZ convert rfc822-to-8bit (ORCPT ); Tue, 6 Dec 2011 06:04:25 -0500 Message-ID: <1323169412.32012.69.camel@twins> Subject: Re: [PATCH 00/12] perf_events: add support for sampling taken branches (v2) From: Peter Zijlstra To: Will Deacon Cc: Stephane Eranian , "linux-kernel@vger.kernel.org" , "mingo@elte.hu" , "acme@redhat.com" , "ming.m.lin@intel.com" , "andi@firstfloor.org" , "robert.richter@amd.com" , "ravitillo@lbl.gov" , "paulus@samba.org" , "benh@kernel.crashing.org" , "rth@twiddle.net" , "ralf@linux-mips.org" , "davem@davemloft.net" , "lethal@linux-sh.org" Date: Tue, 06 Dec 2011 12:03:32 +0100 In-Reply-To: <20111206094927.GA25782@mudshark.cambridge.arm.com> References: <1318595833-29984-1-git-send-email-eranian@google.com> <1323124766.32012.49.camel@twins> <20111206094927.GA25782@mudshark.cambridge.arm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.2.1- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-12-06 at 09:49 +0000, Will Deacon wrote: > On Mon, Dec 05, 2011 at 10:39:26PM +0000, Peter Zijlstra wrote: > > On Fri, 2011-10-14 at 14:37 +0200, Stephane Eranian wrote: > > > This patchset adds an important and useful new feature to > > > perf_events: branch stack sampling. In other words, the > > > ability to capture taken branches into each sample. > > > > > Other than the few comments given it all looks good. My main worry is > > the Intel only aspect, I'd really love for there to be another platform > > that could implement at least part of this. > > I discussed this with Stephane in Prague and, although it would be lovely to > have this on ARM, we simply don't have the hardware to do it. So the nature > of series does seem to be x86-centric unless there's way to do a watered > down version in software. The only way to do this in software would be like CONFIG_PROFILE_ALL_BRANCHES and that's horrid (and kernel only). But there's more than Intel & ARM, but it looks like PPC doesn't have this either and I suspect MIPS and SPARC don't either, which doesn't leave us with much else. So I guess we should just go ahead and merge this and hope more hardware grows this feature in a compatible enough manner.