From: Ben Greear Subject: Re: Reading NFS file without copying to user-space? Date: Fri, 04 Sep 2009 14:57:06 -0700 Message-ID: <4AA18D32.50507@candelatech.com> References: <4AA16F25.6050700@candelatech.com> <1252096543.2402.4.camel@heimdal.trondhjem.org> <4AA17D62.9020404@candelatech.com> <74C14419-4D21-4EC2-B01A-EAC04B354F06@fys.uio.no> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: "linux-nfs@vger.kernel.org" To: Trond Myklebust Return-path: Received: from mail.candelatech.com ([208.74.158.172]:43330 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934318AbZIDV5M (ORCPT ); Fri, 4 Sep 2009 17:57:12 -0400 In-Reply-To: <74C14419-4D21-4EC2-B01A-EAC04B354F06@fys.uio.no> Sender: linux-nfs-owner@vger.kernel.org List-ID: On 09/04/2009 01:58 PM, Trond Myklebust wrote: > You're missing the point. O_DIRECT does not copy data from the kernel > into userspace. The data is placed directly into the user buffer from > the socket. > > The only faster alternative would be to directly discard the data in the > socket, and we offer no option to do that. I was thinking I might be clever and use sendfile to send an nfs file to /dev/zero, but unfortunately it seems sendfile can only send to a destination that is a socket.... Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com