From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932166AbVHRKGa (ORCPT ); Thu, 18 Aug 2005 06:06:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932169AbVHRKGa (ORCPT ); Thu, 18 Aug 2005 06:06:30 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:25318 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S932166AbVHRKG3 (ORCPT ); Thu, 18 Aug 2005 06:06:29 -0400 Date: Thu, 18 Aug 2005 11:06:28 +0100 From: Christoph Hellwig To: Folkert van Heusden Cc: linux-kernel@vger.kernel.org Subject: Re: zero-copy read() interface Message-ID: <20050818100628.GA5629@infradead.org> Mail-Followup-To: Christoph Hellwig , Folkert van Heusden , linux-kernel@vger.kernel.org References: <20050818100151.GF12313@vanheusden.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050818100151.GF12313@vanheusden.com> User-Agent: Mutt/1.4.2.1i X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 18, 2005 at 12:01:52PM +0200, Folkert van Heusden wrote: > What about a zero-copy read-interface? > An ioctl (or something) which enables the kernel to do dma directly to > the userspace. Of course this should be limited to the root-user or a > user with special capabilities (rights) since if a drive screws up, data > from a different sector (or so) might end up in the proces' memory. Of > course copying a sector from kernel- to userspace can be done pretty > fast but i.m.h.o. all possible speedimprovements should be made unless > unclean. It's called O_DIRECT, and doesn't need root, just some alignment-constraints.