From mboxrd@z Thu Jan 1 00:00:00 1970 From: Werner Almesberger Subject: Re: barriers vs. reads - O_DIRECT Date: Thu, 24 Jun 2004 23:42:55 -0300 Sender: linux-fsdevel-owner@vger.kernel.org Message-ID: <20040624234255.X1325@almesberger.net> References: <20040624144638.V1325@almesberger.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org Return-path: Received: from almesberger.net ([63.105.73.238]:50438 "EHLO host.almesberger.net") by vger.kernel.org with ESMTP id S266167AbUFYCnH (ORCPT ); Thu, 24 Jun 2004 22:43:07 -0400 To: Bryan Henderson Content-Disposition: inline In-Reply-To: ; from hbryan@us.ibm.com on Thu, Jun 24, 2004 at 05:11:20PM -0700 List-Id: linux-fsdevel.vger.kernel.org Bryan Henderson wrote: > There's also (kernel) aio to consider. I suppose this would be the main scenario. AIO+O_DIRECT also gives the closest approximation to directly talking to the elevator. > But I can't see how barriers figure into ordinary O_DIRECT file I/O. Hmm, I've never looked at non-AIO write semantics with O_DIRECT. For reasonable semantics, I guess it would either have to block until the operation has completed, or be "atomic" (*). (*) Defining atomic can be tricky, too. E.g. see http://www.uwsg.iu.edu/hypermail/linux/kernel/0402.0/1361.html - Werner -- _________________________________________________________________________ / Werner Almesberger, Buenos Aires, Argentina wa@almesberger.net / /_http://www.almesberger.net/____________________________________________/