Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756522AbZFVMAU (ORCPT ); Mon, 22 Jun 2009 08:00:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753057AbZFVMAH (ORCPT ); Mon, 22 Jun 2009 08:00:07 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:43266 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752040AbZFVMAG (ORCPT ); Mon, 22 Jun 2009 08:00:06 -0400 Date: Mon, 22 Jun 2009 13:59:28 +0200 From: Ingo Molnar To: eranian@gmail.com Cc: LKML , Andrew Morton , Thomas Gleixner , Robert Richter , Peter Zijlstra , Paul Mackerras , Andi Kleen , Maynard Johnson , Carl Love , Corey J Ashford , Philip Mucci , Dan Terpstra , perfmon2-devel Subject: Re: IV.2 - Features impacting all counters Message-ID: <20090622115928.GQ24366@elte.hu> References: <7c86c4470906161042p7fefdb59y10f8ef4275793f0e@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7c86c4470906161042p7fefdb59y10f8ef4275793f0e@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1357 Lines: 31 > 2/ Features impacting all counters > > On some PMU models, e.g., Itanium, they are certain features which > have an influence on all counters that are active. For instance, > there is a way to restrict monitoring to a range of continuous > code or data addresses using both some PMU registers and the debug > registers. > > Given that the API exposes events (counters) as independent of > each other, I wonder how range restriction could be implemented. A solution is to make it a per-counter attribute and fail to schedule multiple counters at the same time when these constraints differ. > Similarly, on Itanium, there are global behaviors. For instance, > on counter overflow the entire PMU freezes all at once. That seems > to be contradictory with the design of the API which creates the > illusion of independence. > > What solutions do you propose? We propose the same solution as last time: live with the small imprecisions caused by such hardware limitations. We submit that natural workload noise is probably far bigger than any such effect. We could certainly list it as a platform limitation. -- 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/