From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755136AbaCCS60 (ORCPT ); Mon, 3 Mar 2014 13:58:26 -0500 Received: from one.firstfloor.org ([193.170.194.197]:53741 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755038AbaCCS6V (ORCPT ); Mon, 3 Mar 2014 13:58:21 -0500 Date: Mon, 3 Mar 2014 19:58:19 +0100 From: Andi Kleen To: Peter Zijlstra Cc: Joe Mario , Andi Kleen , Don Zickus , Davidlohr Bueso , acme@ghostprotocols.net, LKML , jolsa@redhat.com, fowles@inreach.com, eranian@google.com, Arnaldo Carvalho de Melo , David Ahern , Frederic Weisbecker , Mike Galbraith , Paul Mackerras , Richard Fowles Subject: Re: [PATCH 08/19] perf c2c: Shared data analyser Message-ID: <20140303185819.GB22728@two.firstfloor.org> References: <1393609388-40489-1-git-send-email-dzickus@redhat.com> <1393609388-40489-9-git-send-email-dzickus@redhat.com> <87lhwvawc4.fsf@tassilo.jf.intel.com> <20140228194642.GM25953@redhat.com> <1393621411.2899.39.camel@buesod1.americas.hpqcorp.net> <20140303150531.GZ25953@redhat.com> <20140303172316.GA22728@two.firstfloor.org> <5314C4C4.1020304@redhat.com> <20140303184117.GL9987@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140303184117.GL9987@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 03, 2014 at 07:41:17PM +0100, Peter Zijlstra wrote: > On Mon, Mar 03, 2014 at 01:07:00PM -0500, Joe Mario wrote: > > If you only sample on the HITMs then you don't get the store misses. > > That means you'll not be able to detect who is simultaneously tugging > > on the same cache lines. That gives up much of the value of "perf > > c2c". > > As long as you know which lines are hurting bringing in (loads) you can > often figure out who is doing the stores on them. Yes, especially since every store is a load too (unless you're talking WC) The method c2c uses is more exact, but keep in mind it's a sampling heuristic in any cases, with some potential bias. load-latency tags the loads randomly and there's no guarantee that tagging is fully uniform. Also you only see a subset in any case. > > > As we developed this, we ended up settling on Ivy Bridge to get the > > behavior we wanted. > > Wouldn't SNB also work? Yes. Haswell is best however because it can report addresses on far more events. -Andi -- ak@linux.intel.com -- Speaking for myself only.