From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay1.corp.sgi.com [137.38.102.111]) by oss.sgi.com (Postfix) with ESMTP id 93F947F9B for ; Thu, 23 Jul 2015 18:10:10 -0500 (CDT) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay1.corp.sgi.com (Postfix) with ESMTP id 6D2578F8035 for ; Thu, 23 Jul 2015 16:10:07 -0700 (PDT) Received: from ipmail04.adl6.internode.on.net (ipmail04.adl6.internode.on.net [150.101.137.141]) by cuda.sgi.com with ESMTP id Yz4jlsFzvy4q4f3S for ; Thu, 23 Jul 2015 16:10:05 -0700 (PDT) Date: Fri, 24 Jul 2015 09:09:12 +1000 From: Dave Chinner Subject: Re: xfs_iext_realloc_indirect and "XFS: possible memory allocation deadlock" Message-ID: <20150723230912.GE3902@dastard> References: <20150629222651.GG7943@dastard> <20150707000911.GT7943@dastard> <20150707090511.GA21863@infradead.org> <7792DA2A464640B1BC7220973CED41AE@alyakaslap> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7792DA2A464640B1BC7220973CED41AE@alyakaslap> 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: Alex Lyakas Cc: Danny Shavit , Shyam Kaushik , bfoster@redhat.com, Yair Hershko , xfs@oss.sgi.com, Christoph Hellwig On Thu, Jul 23, 2015 at 05:39:28PM +0200, Alex Lyakas wrote: > Hi Dave, > Just for completeness, XFS speculative preallocation (that is based > now upon the size of the last extent) can still grow up to 4Gb-8Gb > (depending on which patches we are pulling). As a result, xfs_iozero > can still sometimes trigger 1-2GB writes of zeros in one shot. This > turns out to be a bit unfriendly to the drives in some > configurations. So we have applied a custom patch to limit the > speculative preallocation to 32Mb. It would be much better to change xfs_zero_eof() to convert extents beyond EOF to unwritten extents rather than zero them. That way you still get the benefits of the large speculative prealloc but without the zeroing overhead that wierd sparse write patterns can trigger. I just haven't got around to doing this because it hasn't been reported as a significant problem for anyone until now. Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs