From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dkim2.fusionio.com ([66.114.96.54]:35259 "EHLO dkim2.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753732Ab3CCQgX (ORCPT ); Sun, 3 Mar 2013 11:36:23 -0500 Received: from mx1.fusionio.com (unknown [10.101.1.160]) by dkim2.fusionio.com (Postfix) with ESMTP id 5D2029A0402 for ; Sun, 3 Mar 2013 09:36:23 -0700 (MST) Date: Sun, 3 Mar 2013 11:36:20 -0500 From: Chris Mason To: Brendan Hide CC: Holger Hoffstaette , "linux-btrfs@vger.kernel.org" Subject: Re: User feedback: raise the default leaf size to 16k Message-ID: <20130303163620.GD18135@shiny.masoncoding.com> References: <513326FA.3070607@swiftspirit.co.za> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <513326FA.3070607@swiftspirit.co.za> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Sun, Mar 03, 2013 at 03:33:30AM -0700, Brendan Hide wrote: > On 2013/02/13 12:33 PM, Holger Hoffstaette wrote: > > - raise the leaf size to 16k > > - use single metadata profile > > > > ... > > > > the difference in behaviour on a single disk is *very* noticeable. > Did you try an isolated change of leaf size? I think the devs would be > willing to look into the default size if it makes a dramatic difference > on its own. Personally I think you are seeing an improvement more as a > result of the metadata profile rather than the leafsize. > > I don't think changing the default profile for metadata will be easily > entertained as this is very important for protecting against corruption > due to bitrot. The long term plan is to set the default size to 16K, since this does cut down on metadata fragmentation. But in some benchmarks, it adds lock contention because we have fewer blocks to spread the locks over. The 3.9 merge window has fixes for lock contention, so I need to benchmark things again. -chris