From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754857Ab1GEQBj (ORCPT ); Tue, 5 Jul 2011 12:01:39 -0400 Received: from one.firstfloor.org ([213.235.205.2]:54759 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754587Ab1GEQBh (ORCPT ); Tue, 5 Jul 2011 12:01:37 -0400 Message-ID: In-Reply-To: <1309864954.3282.61.camel@twins> References: <1309421396-17438-1-git-send-email-ming.m.lin@intel.com> <1309421396-17438-2-git-send-email-ming.m.lin@intel.com> <20110630165849.GE23059@one.firstfloor.org> <1309761541.18875.40.camel@minggr.sh.intel.com> <20110704215706.GH15637@one.firstfloor.org> <1309864954.3282.61.camel@twins> Date: Tue, 5 Jul 2011 18:01:36 +0200 Subject: Re: [PATCH 1/4] perf, x86: Add Intel Nehalem/Westmere uncore pmu From: "Andi Kleen" To: "Peter Zijlstra" Cc: "Andi Kleen" , "Lin Ming" , "Ingo Molnar" , "Stephane Eranian" , "Arnaldo Carvalho de Melo" , "linux-kernel" User-Agent: SquirrelMail/1.4.21 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > >> But it's not strictly required I would say, >> 44(?) bits are probably enough for near all use cases. > > 44bits is in the hours range for pure cycle counts, which is so-so. I > bet you're going to be very annoyed when you find your counters are > wrecked after your 5 hour test run finishes. For these kinds of long running measurements you usually care about ratios, not absolutes. Some infrequent wrapping should not substantially change. those. -Andi