From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268711AbUJPMLj (ORCPT ); Sat, 16 Oct 2004 08:11:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268713AbUJPMLj (ORCPT ); Sat, 16 Oct 2004 08:11:39 -0400 Received: from holomorphy.com ([207.189.100.168]:9873 "EHLO holomorphy.com") by vger.kernel.org with ESMTP id S268711AbUJPMLg (ORCPT ); Sat, 16 Oct 2004 08:11:36 -0400 Date: Sat, 16 Oct 2004 05:05:04 -0700 From: William Lee Irwin III To: Joel Becker Cc: Avi Kivity , Yasushi Saito , linux-aio@kvack.org, linux-kernel@vger.kernel.org, suparna@in.ibm.com, Janet Morgan Subject: Re: [PATCH 1/2] aio: add vectored I/O support Message-ID: <20041016120504.GV5607@holomorphy.com> References: <416EDD19.3010200@hpl.hp.com> <20041016031301.GC17142@parcelfarce.linux.theplanet.co.uk> <4170AF35.7030806@exanet.com> <20041016053721.GD17142@parcelfarce.linux.theplanet.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041016053721.GD17142@parcelfarce.linux.theplanet.co.uk> User-Agent: Mutt/1.5.6+20040722i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 16, 2004 at 07:18:45AM +0200, Avi Kivity wrote: >> It is a huge performance win, at least on the 2.4-based RHEL kernel. >> Large reads (~256K) using 4K iocbs are very slow on a large RAID, while >> after I coded a similar patch I got a substantial speedup. On Sat, Oct 16, 2004 at 06:37:21AM +0100, Joel Becker wrote: > I'd think we should fix the submission path instead. Why create > iovs _and_ iocbs when we only need to create one? And even if we > decided aio_readv() was still nice to keep, we'd want to fix this > inefficiency in io_submit(). Disk I/O can vector across iocb's; however, network I/O requires temporal ordering not imposed by sequential iocb submission, barring unusual extensions to the semantics. -- wli