Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261153AbTEEKND (ORCPT ); Mon, 5 May 2003 06:13:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261213AbTEEKND (ORCPT ); Mon, 5 May 2003 06:13:03 -0400 Received: from phoenix.infradead.org ([195.224.96.167]:61961 "EHLO phoenix.infradead.org") by vger.kernel.org with ESMTP id S261153AbTEEKNC (ORCPT ); Mon, 5 May 2003 06:13:02 -0400 Date: Mon, 5 May 2003 11:25:31 +0100 From: Christoph Hellwig To: Terje Eggestad Cc: Arjan van de Ven , linux-kernel , D.A.Fedorov@inp.nsk.su Subject: Re: The disappearing sys_call_table export. Message-ID: <20030505112531.B16914@infradead.org> Mail-Followup-To: Christoph Hellwig , Terje Eggestad , Arjan van de Ven , linux-kernel , D.A.Fedorov@inp.nsk.su 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 Content-Length: 1574 Lines: 41 On Mon, May 05, 2003 at 11:33:36AM +0200, Terje Eggestad wrote: > 1. performance is everything. then Linux is the wrong OS for you :) > 2. We're making a MPI library, and as such we don't have any control > with the application. I can't remember that the MPI spec tells anything about intercepting syscalls.. > 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. > 5. the way MPI is written, it's not using a special malloc() to allocate > the send receive buffers. It can't since it would break language binding > to fortran. Thus ANY writeable user page may be used. so use get_user_pages. > 6. point 4: pinning is VERY expensive (point 1), so I can't pin the > buffers every time they're used. Umm, pinning memory all the time means you get a bunch of nice DoS attachs due to the huge amount of memory. > 7. The only way to cache buffers (to see if they're used before and > hence pinned) is the user space virtual address. A syscall, thus ioctl > to a device file is prohibitive expensive under point 1. That's a horribly b0rked approach.. Again, where's your driver source so we can help you to find a better approach out of that mess? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/