Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758584AbZGCXk2 (ORCPT ); Fri, 3 Jul 2009 19:40:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751943AbZGCXkV (ORCPT ); Fri, 3 Jul 2009 19:40:21 -0400 Received: from one.firstfloor.org ([213.235.205.2]:52114 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751716AbZGCXkU (ORCPT ); Fri, 3 Jul 2009 19:40:20 -0400 Date: Sat, 4 Jul 2009 01:40:23 +0200 From: Andi Kleen To: Vince Weaver Cc: Andi Kleen , Ingo Molnar , Peter Zijlstra , Paul Mackerras , linux-kernel@vger.kernel.org, Mike Galbraith Subject: Re: [numbers] perfmon/pfmon overhead of 17%-94% Message-ID: <20090703234023.GM2041@one.firstfloor.org> References: <20090624151010.GA12799@elte.hu> <20090627060432.GB16200@elte.hu> <20090627064404.GA19368@elte.hu> <20090629210206.GB13125@elte.hu> <87bpo1aaaf.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1579 Lines: 38 On Fri, Jul 03, 2009 at 05:25:32PM -0400, Vince Weaver wrote: > >Vince Weaver writes: > >> > >>as I said in a previous post, on most x86 chips the instructions_retired > >>counter also includes any hardware interrupts that occur during the > >>process runtime. > > > >On the other hand afaik near all chips have interrupt performance counter > >events. > > I guess by "near all" you mean "only AMD"? The AMD event also has some Intel CPUs typically have HW_INT.RX event. AMD has a similar event. > well, it's basically at least HZ extra instructions per however many > seconds your benchmark runs, and unfortunately it's non-deterministic > because it depends on keyboard/network/usb/etc interrupts too that may by > chance happen while your program is running. > > For me, it's the determinism that matters. Not overhead, not runtime not To be honest I don't think you'll ever be full deterministic. Modern computers and operating systems are just too complex with too many (often unpredictable) things going on in the background. In my own experience even simulators (which are much more stable than real hardware) are not fully deterministic. You'll always run into problems. If you need 100% deterministic use a simple micro controller. -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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/