Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757845AbXIRMcS (ORCPT ); Tue, 18 Sep 2007 08:32:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755326AbXIRMcA (ORCPT ); Tue, 18 Sep 2007 08:32:00 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:55192 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756361AbXIRMb7 (ORCPT ); Tue, 18 Sep 2007 08:31:59 -0400 Date: Tue, 18 Sep 2007 22:31:07 +1000 From: David Chinner To: Mel Gorman Cc: Christoph Lameter , Nick Piggin , Goswin von Brederlow , Andrew Morton , Joern Engel , andrea@suse.de, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , William Lee Irwin III , David Chinner , Jens Axboe , Badari Pulavarty , Maxim Levitsky , Fengguang Wu , swin wang , totty.lu@gmail.com, hugh@veritas.com Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support) Message-ID: <20070918123107.GW23367404@sgi.com> References: <20070911060349.993975297@sgi.com> <87ir6c3z2l.fsf@informatik.uni-tuebingen.de> <20070916181313.GA16406@skynet.ie> <200709161903.37295.nickpiggin@yahoo.com.au> <20070918100040.GB2035@skynet.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070918100040.GB2035@skynet.ie> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1368 Lines: 35 On Tue, Sep 18, 2007 at 11:00:40AM +0100, Mel Gorman wrote: > We still lack data on what sort of workloads really benefit from large > blocks (assuming there are any that cannot also be solved by improving > order-0). No we don't. All workloads benefit from larger block sizes when you've got a btree tracking 20 million inodes and a create has to search that tree for a free inode. The tree gets much wider and hence we take fewer disk seeks to traverse the tree. Same for large directories, btree's tracking free space, etc - everything goes faster with a larger filesystem block size because we spent less time doing metadata I/O. And the other advantage is that sequential I/O speeds also tend to increase with larger block sizes. e.g. XFS on an Altix (16k pages) using 16k block size is about 20-25% faster on writes than 4k block size. See the graphs at the top of page 12: http://oss.sgi.com/projects/xfs/papers/ols2006/ols-2006-paper.pdf The benefits are really about scalability and with terabyte sized disks on the market..... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/