From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id DA9F57F37 for ; Mon, 20 Jan 2014 16:18:52 -0600 (CST) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay3.corp.sgi.com (Postfix) with ESMTP id 6DE90AC001 for ; Mon, 20 Jan 2014 14:18:49 -0800 (PST) Received: from ipmail07.adl2.internode.on.net (ipmail07.adl2.internode.on.net [150.101.137.131]) by cuda.sgi.com with ESMTP id aGKusylJNz7WzhX9 for ; Mon, 20 Jan 2014 14:18:48 -0800 (PST) Date: Tue, 21 Jan 2014 09:18:43 +1100 From: Dave Chinner Subject: Re: Terrible performance of sequential O_DIRECT 4k writes in SAN environment. ~3 times slower then Solars 10 with the same HBA/Storage. Message-ID: <20140120221843.GJ18112@dastard> References: <20140106201032.GA13491@quack.suse.cz> <20140107155830.GA28395@infradead.org> <20140108140307.GA588@infradead.org> <20140115220721.GY3469@dastard> <20140120135855.GA26280@infradead.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20140120135855.GA26280@infradead.org> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Christoph Hellwig Cc: Jan Kara , linux-scsi , Gluk , Linux Kernel Mailing List , xfs@oss.sgi.com, Sergey Meirovich On Mon, Jan 20, 2014 at 05:58:55AM -0800, Christoph Hellwig wrote: > On Thu, Jan 16, 2014 at 09:07:21AM +1100, Dave Chinner wrote: > > Yes, I think it can be done relatively simply. We'd have to change > > the code in xfs_file_aio_write_checks() to check whether EOF zeroing > > was required rather than always taking an exclusive lock (for block > > aligned IO at EOF sub-block zeroing isn't required), > > That's not even required for supporting aio appends, just a further > optimization for it. Oh, right, I got an off-by-one when reading the code - the EOF zeroing only occurs when the offset is beyond EOF, not at or beyond EOF... > > and then we'd > > have to modify the direct IO code to set the is_async flag > > appropriately. We'd probably need a new flag to say tell the DIO > > code that AIO beyond EOF is OK, but that isn't hard to do.... > > Yep, need a flag to allow appending writes and then defer them. > > > Christoph, are you going to get any time to look at doing this in > > the next few days? > > I'll probably need at least another week before I can get to it. If you > wanna pick it up before than feel free. I'm probably not going to get to it before then, either, so check back in a week? Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs