From: Christoph Hellwig Subject: Re: Performance testing of various barrier reduction patches [was: Re: [RFC v4] ext4: Coordinate fsync requests] Date: Sat, 16 Oct 2010 01:40:41 +0200 Message-ID: <20101015234041.GB1035@lst.de> References: <20100819021441.GM2109@tux1.beaverton.ibm.com> <20100823183119.GA28105@tux1.beaverton.ibm.com> <20100923232527.GB25624@tux1.beaverton.ibm.com> <20100927230111.GV25555@tux1.beaverton.ibm.com> <20101008212606.GE25624@tux1.beaverton.ibm.com> <4CAF937C.4020500@redhat.com> <20101011202020.GF25624@tux1.beaverton.ibm.com> <20101012141455.GA27572@lst.de> <20101015233904.GG25624@tux1.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Ric Wheeler , Andreas Dilger , "Ted Ts'o" , Mingming Cao , linux-ext4 , linux-kernel , Keith Mannthey , Mingming Cao , Tejun Heo , Josef Bacik , Mike Snitzer To: "Darrick J. Wong" Return-path: Content-Disposition: inline In-Reply-To: <20101015233904.GG25624@tux1.beaverton.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Fri, Oct 15, 2010 at 04:39:04PM -0700, Darrick J. Wong wrote: > On Tue, Oct 12, 2010 at 04:14:55PM +0200, Christoph Hellwig wrote: > > I still think adding code to every filesystem to optimize for a rather > > stupid use case is not a good idea. I dropped out a bit from the > > thread in the middle, but what was the real use case for lots of > > concurrent fsyncs on the same inode again? > > The use case I'm looking at is concurrent fsyncs on /different/ inodes, > actually. We have _n_ different processes, each writing (and fsyncing) its own > separate file on the same filesystem. > > iirc, ext4_sync_file is called with the inode mutex held, which prevents > concurrent fsyncs on the same inode. Indeed. Although we could drop it at least for the cache flush call. We already do this for block devices.