From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755054Ab1JQUgE (ORCPT ); Mon, 17 Oct 2011 16:36:04 -0400 Received: from terminus.zytor.com ([198.137.202.10]:35678 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753219Ab1JQUgC (ORCPT ); Mon, 17 Oct 2011 16:36:02 -0400 Message-ID: <4E9C917B.2050802@zytor.com> Date: Mon, 17 Oct 2011 13:35:07 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 MIME-Version: 1.0 To: Ingo Molnar CC: Thomas Gleixner , Linus Torvalds , Simon Kirby , Peter Zijlstra , Linux Kernel Mailing List , Dave Jones , Martin Schwidefsky Subject: Re: Linux 3.1-rc9 References: <20111007070842.GA27555@hostway.ca> <20111007174848.GA11011@hostway.ca> <1318010515.398.8.camel@twins> <20111008005035.GC22843@hostway.ca> <1318060551.8395.0.camel@twins> <20111012213555.GC24461@hostway.ca> <20111013232521.GA5654@hostway.ca> <20111017045806.GA11561@elte.hu> <20111017184916.GA5545@elte.hu> In-Reply-To: <20111017184916.GA5545@elte.hu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/17/2011 11:49 AM, Ingo Molnar wrote: > Do we have some hard data on this, which we could put into comments > in include/linux/ktime.h and such? Older versions of GCC used to do a > bad job of long long handling on 32-bit systems - that might be a > factor in the performance figures. > > But i suspect you are right that the cost is still very much there 64/64 division is done bit by bit on most (all?) 32-bit architectures. 64/32 division can be done in hardware on some architectures, e.g. x86. -hpa