From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765200AbXHFRUA (ORCPT ); Mon, 6 Aug 2007 13:20:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758197AbXHFRTw (ORCPT ); Mon, 6 Aug 2007 13:19:52 -0400 Received: from waste.org ([66.93.16.53]:56111 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757291AbXHFRTv (ORCPT ); Mon, 6 Aug 2007 13:19:51 -0400 Date: Mon, 6 Aug 2007 12:20:03 -0500 From: Matt Mackall To: Lindsay Roberts Cc: Pavel Machek , Andrew Morton , LKML , celinux-dev@tree.celinuxforum.org Subject: Re: [PATCH] fs: Add romfs version 2 Message-ID: <20070806172002.GW11115@waste.org> References: <8734b7880707122301m400294d4nf12072f949c95fa4@mail.gmail.com> <20070717013635.d6d0b124.akpm@linux-foundation.org> <20070717192100.GE11166@waste.org> <8734b7880707172016v530ce775p108910f7baf9de8e@mail.gmail.com> <20070725184005.GD8225@ucw.cz> <8734b7880708060043i125419e0w3db5d4431496985f@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8734b7880708060043i125419e0w3db5d4431496985f@mail.gmail.com> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 06, 2007 at 05:43:54PM +1000, Lindsay Roberts wrote: > On 7/26/07, Pavel Machek wrote: > > If the fs is read-only.. can we do some tail packing and get _both_ > > speed and space efficiency? > > You mean don't block align files of size less than 1k, and > intelligently pack them into the gaps left by files that are aligned? > Does seem that most noticeable performance issues occur on sequential > reads of large files, this sounds like a good idea, but I would > welcome comments on this. > > Also I assume romfs currently has a small hidden benefit as a result > of it storing its file data serially after the inode: the initial read > of the inode reads and therefore caches the block containing the > (initial) file data. Obviously with block aligned file data this only > applies if sequential prefetching is performed. I'd be interested to > know if this is an issue worth regarding. It seems to me that the initial design goals of romfs were: a) space efficiency b) simplicity ..with performance basically ignored. On an actual ROM-backed filesystem, alignment doesn't help you until it becomes large enough that you can execute pages in place. And I don't think your reproduceability concern was even on the radar. So naming a new filesystem romfs which has the priorities: a) performance b) reproduceability seems like it's going to disappoint and confuse people who were aligned with the original goals. -- Mathematics is the supreme nostalgia of our time.