From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [patch] Performance Counters for Linux, v2 Date: Mon, 08 Dec 2008 04:02:04 -0800 (PST) Message-ID: <20081208.040204.139217002.davem@davemloft.net> References: <20081208012211.GA23106@elte.hu> <18748.37739.383961.318233@drongo.ozlabs.ibm.com> <20081208113318.GA14723@elte.hu> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:59298 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751781AbYLHMCF (ORCPT ); Mon, 8 Dec 2008 07:02:05 -0500 In-Reply-To: <20081208113318.GA14723@elte.hu> Sender: linux-arch-owner@vger.kernel.org List-ID: To: mingo@elte.hu Cc: paulus@samba.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, linux-arch@vger.kernel.org, akpm@linux-foundation.org, eranian@googlemail.com, dada1@cosmosbay.com, robert.richter@amd.com, arjan@infradead.org, hpa@zytor.com, a.p.zijlstra@chello.nl, rostedt@goodmis.org From: Ingo Molnar Date: Mon, 8 Dec 2008 12:33:18 +0100 > Your whole statistical argument that group readout is a must-have for > precision is fundamentally flawed as well: counters _themselves_, as used > by most applications, by their nature, are a statistical sample to begin > with. There's way too many hardware events to track each of them > unintrusively - so this type of instrumentation is _all_ sampling based, > and fundamentally so. (with a few narrow exceptions such as single-event > interrupts for certain rare event types) There are a lot of people who are going to fundamentally disagree with this, myself included. A lot of things are being stated about what people do with this stuff, but I think there are people working longer in this area who quite possibly know a lot better. But they were blindsided by this new work instead of being consulted, which was pretty unnice.