From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262120AbTEEJZo (ORCPT ); Mon, 5 May 2003 05:25:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262121AbTEEJZo (ORCPT ); Mon, 5 May 2003 05:25:44 -0400 Received: from nat-pool-rdu.redhat.com ([66.187.233.200]:34066 "EHLO devserv.devel.redhat.com") by vger.kernel.org with ESMTP id S262120AbTEEJZn (ORCPT ); Mon, 5 May 2003 05:25:43 -0400 Date: Mon, 5 May 2003 09:38:10 +0000 From: Arjan van de Ven To: Terje Eggestad Cc: Christoph Hellwig , Arjan van de Ven , linux-kernel , D.A.Fedorov@inp.nsk.su Subject: Re: The disappearing sys_call_table export. Message-ID: <20030505093810.A22327@devserv.devel.redhat.com> References: <1052122784.2821.4.camel@pc-16.office.scali.no> <20030505092324.A13336@infradead.org> <1052127216.2821.51.camel@pc-16.office.scali.no> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <1052127216.2821.51.camel@pc-16.office.scali.no>; from terje.eggestad@scali.com on Mon, May 05, 2003 at 11:33:36AM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 05, 2003 at 11:33:36AM +0200, Terje Eggestad wrote: > 1. performance is everything. > 2. We're making a MPI library, and as such we don't have any control > with the application. > 3a. The various hardware for cluster interconnect all work with DMA. > 3b. the performance loss from copying from a receive area to the > userspace buffer is unacceptable. > 3c. It's therefore necessary for HW to access user pages. > 4. In order to to 3, the user pages must be pinned down. see how AIO does this, and O_DIRECT, and rawio. They all have the same requirement and manage to cope.