From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933052AbXCOThW (ORCPT ); Thu, 15 Mar 2007 15:37:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933180AbXCOThV (ORCPT ); Thu, 15 Mar 2007 15:37:21 -0400 Received: from mx1.redhat.com ([66.187.233.31]:45261 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933052AbXCOThU (ORCPT ); Thu, 15 Mar 2007 15:37:20 -0400 Message-ID: <45F9A063.9040205@redhat.com> Date: Thu, 15 Mar 2007 12:37:07 -0700 From: Ulrich Drepper Organization: Red Hat, Inc. User-Agent: Thunderbird 1.5.0.10 (X11/20070302) MIME-Version: 1.0 To: Andrew Morton CC: Pierre.Peiffer@bull.net, mingo@elte.hu, linux-kernel@vger.kernel.org, jean-pierre.dion@bull.net Subject: Re: [PATCH 2.6.21-rc3-mm2 4/4] sys_futex64 : allows 64bit futexes References: <20070313095203.154246923@bull.net> <20070313095549.813330645@bull.net> <20070315110752.f1df4509.akpm@linux-foundation.org> <45F99A8B.4050003@redhat.com> <20070315113136.b04ce342.akpm@linux-foundation.org> In-Reply-To: <20070315113136.b04ce342.akpm@linux-foundation.org> X-Enigmail-Version: 0.94.3.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig912616C16651E99560706343" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig912616C16651E99560706343 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Andrew Morton wrote: > Well OK. But that doesn't actually explain why 64-bit mutexes are need= ed. > It just says they are required. I can show you the code but it's not easy to understand. For complicated syn objects like rwlocks the state information is more than just locked or not. Currently we have to use internal locks, modify the state information, and then release it. This is terribly inefficient when many threads are used. With 64bit futexes the state information can be kept in the futex object and we don't need an internal lock, hence the speed-up. --=20 =E2=9E=A7 Ulrich Drepper =E2=9E=A7 Red Hat, Inc. =E2=9E=A7 444 Castro St = =E2=9E=A7 Mountain View, CA =E2=9D=96 --------------enig912616C16651E99560706343 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFF+aBj2ijCOnn/RHQRAsgcAJ42y3dHmB3L5aq6/fOH1WHNKRFUegCgqY76 QMotmx7LbC9jTngCk2+Vw9E= =y1AV -----END PGP SIGNATURE----- --------------enig912616C16651E99560706343--