From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p3QLmrSU183970 for ; Tue, 26 Apr 2011 16:48:53 -0500 Received: from mail.1-click.hu (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 5EC1315C9757 for ; Tue, 26 Apr 2011 14:52:24 -0700 (PDT) Received: from mail.1-click.hu (ns2.netcenter.hu [195.228.155.139]) by cuda.sgi.com with ESMTP id NEdvJNYZvuEuMTHl for ; Tue, 26 Apr 2011 14:52:24 -0700 (PDT) Message-ID: <367BBF55D8CD426888E671F8C7422966@myXP> From: "Janos Haar" References: <20110411214238.GE21395@dastard> <20110411233705.GA29358@infradead.org> Subject: Re: 2 question about XFS fragmentation and _fsr: Q2 Date: Tue, 26 Apr 2011 23:49:53 +0200 MIME-Version: 1.0 List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Christoph Hellwig Cc: linux-xfs@oss.sgi.com ----- Original Message ----- From: "Christoph Hellwig" To: "Dave Chinner" Cc: "Janos Haar" ; Sent: Tuesday, April 12, 2011 1:37 AM Subject: Re: 2 question about XFS fragmentation and _fsr > On Tue, Apr 12, 2011 at 07:42:38AM +1000, Dave Chinner wrote: >> Depends on your samba configuration to how it does writes. If it is >> conigured to do sync writes then it will have all sorts of >> fragmentation problems. So without more details about the workload, >> the kernel that is being used, the fragmentation occurring (xfs_bmap >> is your friend) and the samba config, there's little that can be >> suggested here. > > Very few people configure Samba to do sync writes, but even without > that I see files written by Samba heavily fragmented when the systems > operates under intense memory pressure. The CIFS protocol has very > small write sizes, and it seems like they do not always arrive in order. > If the system is under enough memory pressure to write them out already > before the previous fragment arrive it can cause very fragmented > extent maps. Enabling the "strict allocate" option in newer Samba > version fixes that problem by doing fallocates in larger chunks, which > from my observation always happen in order. The downside is that > current fallocate in XFS is not designed to be used in a fastpath, > and thus causes performance degradations during the actual write. Is there anything what i can do in proc/sys/vm configuration to solve the fragment write problem? Thanks, Janos _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs