From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754137AbYEaDTD (ORCPT ); Fri, 30 May 2008 23:19:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750873AbYEaDSy (ORCPT ); Fri, 30 May 2008 23:18:54 -0400 Received: from mx1.redhat.com ([66.187.233.31]:35236 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750801AbYEaDSx (ORCPT ); Fri, 30 May 2008 23:18:53 -0400 Message-ID: <4840C394.2080807@redhat.com> Date: Fri, 30 May 2008 20:18:44 -0700 From: Ulrich Drepper Organization: Red Hat, Inc. User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Linus Torvalds CC: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mtk.manpages@gmail.com Subject: Re: [PATCH 3/3] 64-bit futexes: x86 support References: <200805310127.m4V1RLdP013819@devserv.devel.redhat.com> In-Reply-To: X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Linus Torvalds wrote: > Also, doesn't this mean that effectively you have given up on any CPU > before the Pentium entirely? Yes, but only for the speed-up. Not for the functionality. All programs will work just fine. > Not that I want to take the patches _anyway_, but it seems doubly stupid. > Those things are going to be UP machines, so you could have just emulated > it with no correctness issues by disabling preemption. First, you're thinking too much in kernel terms. At userlevel I cannot disable interrupts etc. I cannot read 64 bits atomically on those processors. Second, the old implementation is not significantly slower in normal programs on UP machines. It's really not a big issue. In any case, robbing 64-bit architectures of the possible performance gain just because there are ancient versions which cannot do it is just plain stupid. I know you cannot suggest that. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkhAw5QACgkQ2ijCOnn/RHTRRwCgv37woIjA5RJji4XamBQVqCyF VMwAoIauSEdAlfK4pBJhMkIKirwEBw0z =rDJc -----END PGP SIGNATURE-----