From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752100Ab1LKPth (ORCPT ); Sun, 11 Dec 2011 10:49:37 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:45962 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752036Ab1LKPtg (ORCPT ); Sun, 11 Dec 2011 10:49:36 -0500 Date: Sun, 11 Dec 2011 16:47:42 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Stephane Eranian , linux-kernel@vger.kernel.org, acme@infradead.org, robert.richter@amd.com, ming.m.lin@intel.com, andi@firstfloor.org, asharma@fb.com Subject: Re: [PATCH 2/4] perf_event: add PERF_COUNT_HW_REF_CPU_CYCLES generic PMU event Message-ID: <20111211154742.GA1213@elte.hu> References: <1323559734-3488-1-git-send-email-eranian@google.com> <1323559734-3488-3-git-send-email-eranian@google.com> <20111211080138.GB20790@elte.hu> <1323608131.16764.19.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1323608131.16764.19.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=AWL,BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] 0.0 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Sun, 2011-12-11 at 09:01 +0100, Ingo Molnar wrote: > > > + PERF_COUNT_HW_REF_CPU_CYCLES = 9, > > > > Btw., that was what 'bus cycles' tried to do a long time ago: > > the constant, non-variable baseline heartbeat of the system. > > This isn't about that. Its about exposing the third fixed > purpose counter. Intel, in their infinite wisdom, created a > fixed purpose counter for which there is no equivalent in the > general purpose events. > > Our fixed purpose counter support is predicated on the > assumption that there is, and simply maps any event code to > also include the fixed purpose counter if appropriate. > > There not being an event to map from has thus far avoided > exposing this third fixed purpose event. > > The problem with remapping BUS_CYCLES is that BUS_CYCLES (now) > is something you can program on the {2,4,8} general purpose > counters, whereas this new thing can only ever be ran from the > 1 fixed purpose counter. Okay - if we want/need 3 variants then i have no objections. Thanks, Ingo