From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: DIF/DIX updates for 2.6.32 Date: Thu, 27 Aug 2009 16:05:01 -0400 Message-ID: <20090827200501.GA4940@think> References: <1251267481-24135-1-git-send-email-martin.petersen@oracle.com> <4A95226E.8030504@panasas.com> <4A9656B6.5060100@panasas.com> <1251380803.6426.16.camel@mulgrave.site> <4A969AD4.7070309@panasas.com> <1251384706.6426.29.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from acsinet11.oracle.com ([141.146.126.233]:62248 "EHLO acsinet11.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752378AbZH0UGB (ORCPT ); Thu, 27 Aug 2009 16:06:01 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Martin K. Petersen" Cc: James Bottomley , Boaz Harrosh , Andrew Morton , Jeff Moyer , Ric Wheeler , linux-scsi@vger.kernel.org On Thu, Aug 27, 2009 at 04:02:41PM -0400, Martin K. Petersen wrote: > >>>>> "James" == James Bottomley writes: > > >> This is not an option on a mirror system, and the performance > >> gain/lose is dependent on the round trip speed. If for every digest > >> error I have an error recovery cycle, delays, and stalls. Then no it > >> is not better. Not to mention some iscsi-targets that reset and the > >> all session must be re-established. > > James> Your suggestion of putting processes to sleep while I/O is > James> pending will degrade performance for everyone; that's not really > James> an acceptable tradeoff for improving one corner case. > [ changing pages in flight ] > > In my opinion ext[234] should simply be fixed. If there's a significant > performance hit on those filesystems we could make the wait conditional > on a block_device flag. I agree here. It is pretty trivial in the filesystem to wait for pages in flight, and it shouldn't be the job of the lower layers to double buffer 100% of the time. -chris