Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753841AbXJ2UTS (ORCPT ); Mon, 29 Oct 2007 16:19:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752528AbXJ2UTI (ORCPT ); Mon, 29 Oct 2007 16:19:08 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:52687 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752085AbXJ2UTH (ORCPT ); Mon, 29 Oct 2007 16:19:07 -0400 Date: Mon, 29 Oct 2007 21:19:11 +0100 From: Pavel Machek To: Lennart Sorensen Cc: Rik van Riel , linux-kernel@vger.kernel.org Subject: Re: WANTED: kernel projects for CS students Message-ID: <20071029201911.GB3537@elf.ucw.cz> References: <20071014190128.6e3cdb44@bree.surriel.com> <20071028180707.GA6111@ucw.cz> <20071029194820.GC27646@csclub.uwaterloo.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071029194820.GC27646@csclub.uwaterloo.ca> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2207 Lines: 49 On Mon 2007-10-29 15:48:20, Lennart Sorensen wrote: > On Sun, Oct 28, 2007 at 06:07:07PM +0000, Pavel Machek wrote: > > Hard stuff: > > > > * network character device -- similar to nbd, but for char devices. > > either figure out how to forward ioctls(), or implement > > usb-over-network, or... > > > > * openMosix -- they seem to have userspace solution, but not GPLed. > > > > * compression for ext4. Its about time someone did it right. Special > > bonus if you can do it in a way that it does not slow down. If cpu > > is free, compress, if it is busy, just write it straight to disk. > > So if I decide that the cpu is busy (because something is asking me to > write the cpu is clearly doing something and hence busy), then I can > skip compression and just write to disk. So by that definition ext4 > already does compression. What a simple project. :) Tell it to your profesor ;-). > Did you mean it ought to come back and do the compression later? Not neccessarily but yes, that would be nice, too. > Is it possible that for some data compressing it and writing will take > less time than not compressing it and writing it to disk? Yes. Typically for all zeros. It will be similar for highly-compressible data (pictures, timetables, ....) root@amd:/data/tmp# time ( cat /dev/zero | head -c 100000000 > delme; sync ) 0.04user 0.48system 6.52 (0m6.521s) elapsed 7.97%CPU root@amd:/data/tmp# time ( cat /dev/zero | head -c 100000000 > delme; sync ) 0.05user 0.61system 6.33 (0m6.333s) elapsed 10.42%CPU root@amd:/data/tmp# time ( cat /dev/zero | head -c 100000000 | gzip - > delme; sync ) 1.57user 0.32system 1.74 (0m1.749s) elapsed 100.00%CPU root@amd:/data/tmp# time ( cat /dev/zero | head -c 100000000 | gzip - > delme; sync ) 1.61user 0.18system 1.65 (0m1.652s) elapsed 100.00%CPU Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/