From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mason Subject: Re: ext2 large block size > page size Date: Fri, 01 Apr 2011 17:53:16 +0200 Message-ID: <4D95F4EC.5080400@free.fr> References: <4D91C806.10601@free.fr> <20110401144912.GF21075@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, cl@linux.com To: Ted Ts'o Return-path: Received: from smtp24.services.sfr.fr ([93.17.128.81]:24251 "EHLO smtp24.services.sfr.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755091Ab1DAPxL (ORCPT ); Fri, 1 Apr 2011 11:53:11 -0400 In-Reply-To: <20110401144912.GF21075@thunk.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: [ Adding Christoph Lameter to the CC list ] Hello Ted, Ted Ts'o wrote: > On Tue, Mar 29, 2011 at 01:52:38PM +0200, Mason wrote: > >> As far as I can tell from a quick Google search, >> there was a push in 2007 to add support for large >> blocks in some file-systems, in particular ext2. >> >> e.g. cf. http://lwn.net/Articles/239090/ >> >> Was this ever accepted into the main line? >> (It seems to have lived within -mm for a while) > > Nope, it never was (as you've by now figured out). > >> I'm working with a ST Microelectronics set-top box. >> Here are a few performance results for a 2TB USB HDD: >> block size 4k : format = 151 s / mount = 242 s >> block size 8k : format = 52 s / mount = 71 s >> block size 16k : format = 30 s / mount = 36 s >> block size 32k : format = 18 s / mount = 19 s >> >> Using 4kB blocks makes mount too slow on the STB, which >> is why I'd like to use larger blocks. It would be nice >> if the movies recorded on the STB could also be read on >> a Linux PC. > > My guess is the mount time slowness is caused an ancient kernel > running on the ST Microelectronics box which is doing mount-time > sanity checks. You can disable this with the mount option -o nocheck. Unfortunately, the operating system of the set-top box is not Linux (ST has only very recently started migrating to Linux). Their "legacy" OS (OS+ running on top of OS21) provides (proprietary, I suppose) implementations of FAT32 and ext2. I used to create FAT32 partitions, until I plugged a 2-TB USB HDD in the STB: format = 123 s mount = 62 s fsck = 517 s (!!) I switched to ext2, hoping to avoid the need to fsck, thanks to the soft updates mode. Problem is, I can't read the files on a Linux PC if I use large blocks, and performance takes a dive if I use "normal" blocks. > A lot of the rationale for larger block sizes was obviated by the use > of more advanced file systems, such as ext4, which have other methods > of dealing with the inefficiencies caused by smaller block sizes. If > your main complaint with using a 4k block size on the set-top box was > the mount-time slowness, that can be fixed with the nocheck mount > option. Unfortunately, the mount function in this OS accepts only two flags: RDONLY and RDWR :-( If I understand correctly, I'm screwed, right? :-) -- Regards.