Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758227AbZF2XzT (ORCPT ); Mon, 29 Jun 2009 19:55:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754446AbZF2XzI (ORCPT ); Mon, 29 Jun 2009 19:55:08 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:59955 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752761AbZF2XzH (ORCPT ); Mon, 29 Jun 2009 19:55:07 -0400 Date: Tue, 30 Jun 2009 01:55:00 +0200 From: Ingo Molnar To: Vince Weaver Cc: Peter Zijlstra , Paul Mackerras , linux-kernel@vger.kernel.org, Mike Galbraith Subject: Re: [numbers] perfmon/pfmon overhead of 17%-94% Message-ID: <20090629235500.GB5869@elte.hu> References: <20090624151010.GA12799@elte.hu> <20090627060432.GB16200@elte.hu> <20090627064404.GA19368@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1252 Lines: 34 * Vince Weaver wrote: >> Besides, you compare perfcounters to perfmon > > what else shoud I be comparing it to? > >> (which you seem to be a contributor of) > > is that not allowed? Here's the full, uncropped sentence i wrote: " Besides, you compare perfcounters to perfmon (which you seem to be a contributor of), while in reality perfmon has much, much worse (and unfixable, because designed-in) measurement overhead. " Where i question the blatant hypocracy of bringing up perfmon as a good example while in reality perfmon has far worse measurement overhead than perfcounters, for a wide range of workloads. As far as i can see you didnt answer my questions: why are you dismissing perfcounters for a minor, once per startup measurement offset (which is entirely fixable - see the patch i sent), while you generously allow perfmon to have serious, 90% measurement overhead amounting to billions of instructions overhead per second, for certain workloads? Ingo -- 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/