From: Daniel Phillips Subject: Re: [CALL FOR TESTING] Make Ext3 fsck way faster [2.6.24-rc6 -mm patch] Date: Sat, 19 Jan 2008 20:10:20 -0800 Message-ID: <200801192010.20699.phillips@phunq.net> References: <200801140839.01986.abhishekrai@google.com> <20080115152801.GA7292@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: "Theodore Tso" , "Christoph Hellwig" , "Andrew Morton" , linux-kernel@vger.kernel.org, rohitseth@google.com, linux-ext4@vger.kernel.org To: "Abhishek Rai" Return-path: In-Reply-To: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thursday 17 January 2008 04:47, Abhishek Rai wrote: > > if Abhishek wants to pursue it, would be to pull in all of the > > indirect blocks when the file is opened, and create an in-memory > > extent tree that would speed up access to the file. It's rarely > > worth doing this without metaclustering, since it doesn't help for > > sequential I/O, only random I/O, but with metaclustering it would > > also be a win for sequential I/O. (This would also remove the > > minor performance degradation for sequential I/O imposed by > > metaclustering, and in fact improve it slightly for really big > > files.) > > Also, since the in memory extent tree will now occupy much less > space, we can keep them cached for a much longer time which will > improve performance of random reads. The new metaclustering patch is > more amenable to this trick since it reduces fragmentation thereby > reducing the number of extents. I can see value in preemptively loading indirect blocks into the buffer cache, but is building a second-order extent tree really worth the effort? Probing the buffer cache is very fast. Regards, Daniel