From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Lougher Subject: Re: [ANN] Squashfs 3.0 released Date: Tue, 21 Mar 2006 19:08:21 +0000 Message-ID: <44204F25.4090403@lougher.org.uk> References: <20060317104023.GA28927@wohnheim.fh-wedel.de> <20060317124310.GB28927@wohnheim.fh-wedel.de> <441ADD28.3090303@garzik.org> <0E3DADA8-1A1C-47C5-A3CF-F6A85FF5AFB8@lougher.org.uk> <441AF118.7000902@garzik.org> <20060319163249.GA3856@ucw.cz> <4420236F.80608@lougher.demon.co.uk> <20060321161452.GG27946@ftp.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Pavel Machek , "unlisted-recipients: no To-header on input <;, Jeff Garzik" , J?rn Engel , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Return-path: Received: from anchor-post-32.mail.demon.net ([194.217.242.90]:16391 "EHLO anchor-post-32.mail.demon.net") by vger.kernel.org with ESMTP id S965044AbWCUTIb (ORCPT ); Tue, 21 Mar 2006 14:08:31 -0500 To: Al Viro In-Reply-To: <20060321161452.GG27946@ftp.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Al Viro wrote: >On Tue, Mar 21, 2006 at 04:01:51PM +0000, Phillip Lougher wrote: > > >>Perhaps, but almost all the byteswap is performed on the metadata side, >>reading directories and inodes, where nearly every byte will need to be >>swapped. As inodes are compacted and compressed in 8 KB blocks, and are >>on average 15 bytes in size, for each 8 KB decompress you're potentially >>doing 8192/15 inode byteswaps. This is probably sufficent to affect >>directory search and lookup on a slow processor. >> >> > >Oh, please... Conversion from known endianness to host-endian is considerably >faster than checking flag + branch + two variants, not to mention being >smaller. > > It's one flag check, and one set of swap code actually. The point that was being made is it is better to avoid byte swapping if possible.