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 C7B7B7CB0 for ; Tue, 2 Feb 2016 20:47:30 -0600 (CST) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay3.corp.sgi.com (Postfix) with ESMTP id 63304AC001 for ; Tue, 2 Feb 2016 18:47:29 -0800 (PST) Received: from sandeen.net (sandeen.net [63.231.237.45]) by cuda.sgi.com with ESMTP id pi7JkXppOrRwOEFX for ; Tue, 02 Feb 2016 18:47:26 -0800 (PST) Received: from liberator.sandeen.net (liberator.sandeen.net [10.0.0.4]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by sandeen.net (Postfix) with ESMTPSA id 9652563C6064 for ; Tue, 2 Feb 2016 20:47:25 -0600 (CST) Subject: Re: Request for information on bloated writes using Swift References: From: Eric Sandeen Message-ID: <56B16A3C.1030207@sandeen.net> Date: Tue, 2 Feb 2016 20:47:24 -0600 MIME-Version: 1.0 In-Reply-To: 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: xfs@oss.sgi.com On 2/2/16 4:32 PM, Dilip Simha wrote: > Hi, > > I have a question regarding speculated preallocation in XFS, w.r.t > kernel version: 3.16.0-46-generic. I am using Swift version: 1.0 and > mkfs.xfs version 3.2.1 > > When I write a 256KiB file to Swift, I see that the underlying XFS > uses 3x the amount of space/blocks to write that data. Upon > performing detailed experiments, I see that when Swift uses fallocate > (default approach), XFS doesn't reclaim the preallocated blocks that > XFS allocated. Swift fallocate doesn't exceed the body size(256 > KiB). > > Interestingly, when either allocsize=4k or when swift doesn't use > fallocate, XFS doesn't consume additional space. > > Can you please let me know if this is a known bug and if its fixed in > the later versions? Can you clarify the exact sequence of events? i.e. - xfs_io -f -c "fallocate 0 256k" -c "pwrite 0 256k" somefile leads to unreaclaimed preallocation, while xfs_io -f -c "pwrite 0 256k" somefile does not? Or is it some other sequence? I don't have a 3.16 handy to test, but if you can describe it in more detail that'd help. Some of this is influenced by fs geometry, too so xfs_info output would be good, along with any mount options you might be using. Are you preallocating with or without KEEP_SIZE? -Eric _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs