From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Fri, 31 Aug 2007 06:51:19 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with SMTP id l7VDpD4p022771 for ; Fri, 31 Aug 2007 06:51:15 -0700 Date: Fri, 31 Aug 2007 23:50:42 +1000 From: David Chinner Subject: Re: [PATCH] Increase lockdep MAX_LOCK_DEPTH Message-ID: <20070831135042.GD422459@sgi.com> References: <46D79C62.1010304@sandeen.net> <1188542389.6112.44.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1188542389.6112.44.camel@twins> Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Peter Zijlstra Cc: Eric Sandeen , linux-kernel Mailing List , xfs-oss , Dave Chinner , Ingo Molnar On Fri, Aug 31, 2007 at 08:39:49AM +0200, Peter Zijlstra wrote: > On Thu, 2007-08-30 at 23:43 -0500, Eric Sandeen wrote: > > The xfs filesystem can exceed the current lockdep > > MAX_LOCK_DEPTH, because when deleting an entire cluster of inodes, > > they all get locked in xfs_ifree_cluster(). The normal cluster > > size is 8192 bytes, and with the default (and minimum) inode size > > of 256 bytes, that's up to 32 inodes that get locked. Throw in a > > few other locks along the way, and 40 seems enough to get me through > > all the tests in the xfsqa suite on 4k blocks. (block sizes > > above 8K will still exceed this though, I think) > > As 40 will still not be enough for people with larger block sizes, this > does not seems like a solid solution. Could XFS possibly batch in > smaller (fixed sized) chunks, or does that have significant down sides? The problem is not filesystem block size, it's the xfs inode cluster buffer size / the size of the inodes that determines the lock depth. the common case is 8k/256 = 32 inodes in a buffer, and they all get looked during inode cluster writeback. This inode writeback clustering is one of the reasons XFS doesn't suffer from atime issues as much as other filesystems - it doesn't need to do as much I/O to write back dirty inodes to disk. IOWs, we are not going to make the inode clusters smallers - if anything they are going to get *larger* in future so we do less I/O during inode writeback than we do now..... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group