Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758045AbZDSCIg (ORCPT ); Sat, 18 Apr 2009 22:08:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753772AbZDSCIZ (ORCPT ); Sat, 18 Apr 2009 22:08:25 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57701 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752516AbZDSCIY (ORCPT ); Sat, 18 Apr 2009 22:08:24 -0400 Message-ID: <49EA8766.9070605@zytor.com> Date: Sat, 18 Apr 2009 19:07:34 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Matti Aarnio CC: Jesper Juhl , Prakash Punnoor , Michael Tokarev , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, neilb@suse.de Subject: Re: Proposal: make RAID6 code optional References: <200904180946.27722.prakash@punnoor.de> <49E98AD2.8060601@msgid.tls.msk.ru> <200904181117.03418.prakash@punnoor.de> <20090418145850.GD28512@mea-ext.zmailer.org> In-Reply-To: <20090418145850.GD28512@mea-ext.zmailer.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1411 Lines: 38 Matti Aarnio wrote: > > I did quick "sum of symbol sizes" lookup of the raid.ko, and got > it like this: > > nm -t d -n -S /lib/modules/2.6.27.21-170.2.56.fc10.x86_64/kernel/drivers/md/raid456.ko | grep raid4|awk '{print $2}'|sed -e 's/^0*//g'|awk '{sum+=$1}END{print sum}' > ... > > raid4: 152 > raid5: 7165 > raid6: 75558 > > Entire 64kB of that raid6 is single pre-initialized r/o datablock: raid6_gfmul > > So yes, having RAID6 personality as separate module would be appropriate for > systems that are only interested in RAID4 or RAID5. Separating the RAID4 > personality wastes space, separating RAID5 ... barely 2 of 4k memory pages. > RAID 4 is really just another layout scheme for RAID 5. But yes, moving RAID 6 to a separate module makes sense. The amount of RAID 5 code not used by RAID 6 is fairly trivial, so the right way to do this is to have the raid6 module depend on the raid5 module. There used to be a raid6 module which was forked from raid5, with a lot of duplicate code. That really made really no sense. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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/