From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762609AbXGYOjS (ORCPT ); Wed, 25 Jul 2007 10:39:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752889AbXGYOjJ (ORCPT ); Wed, 25 Jul 2007 10:39:09 -0400 Received: from ns.suse.de ([195.135.220.2]:32896 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752059AbXGYOjI (ORCPT ); Wed, 25 Jul 2007 10:39:08 -0400 Date: Wed, 25 Jul 2007 16:39:04 +0200 From: Andrea Arcangeli To: William Lee Irwin III Cc: Dave Hansen , linux-kernel@vger.kernel.org Subject: Re: RFC: CONFIG_PAGE_SHIFT (aka software PAGE_SIZE) Message-ID: <20070725143904.GI19559@v2.random> References: <20070706222651.GG5777@v2.random> <1183764801.10287.233.camel@localhost> <20070706235228.GL5777@v2.random> <20070717174737.GM6909@holomorphy.com> <20070717193308.GD25301@v2.random> <20070718133222.GM11781@holomorphy.com> <20070724194418.GH19559@v2.random> <20070725032011.GN6909@holomorphy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070725032011.GN6909@holomorphy.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 24, 2007 at 08:20:11PM -0700, William Lee Irwin III wrote: > In any event, I've never been involved in a research project, though I didn't mean it was supposed to be research project in some University. But IIRC it was founded by what is defined as R&D in the income statement of a public company. That's why I called so, given it wasn't incorporated in mainline or forked trees, and it eventually bitrotten. I didn't mean to de-qualify the effort by calling it that way. Infact I'm just saying it is valid now more than ever before, given the current directions that are being pushed for mainline. > In both instances, insurmountable nontechnical obstacles were present, > which remain in place and effectively limit the scale and scope of any > sort of project I can personally lead with any sort of likelihood of > mainline acceptance. > > Where I am limited, you are not. Good luck to you. Not so sure as you are, I'm not even invited to KS this year, but I guess that's fair enough punishment for me, given I also wasted some time with other activities that in the long run I hope will become profitable (this remains to be seen though, there's an Italian saying that "who wants too much will get nothing" ;). But I'll be at the VM summit which to me is probably more important than KS and I hope to have some discussion about this stuff there, hope you're there too. Anyway there's no reason why you shouldn't contribute to CONFIG_PAGE_SHIFT if you want. I don't really care if it's me doing it, or you or Hugh, I stepped in first because of the great idea of the Hack Week and second because I care that Linux goes in directions that benefit everyone, not just a single filesystem running on top of some scatter gather crippled storage that slowdowns like a crawl if the sg entries are small (which is something CONFIG_PAGE_SHIFT will address too just fine but while giving other advantages at the same time). I'm also not against the defrag efforts, but I simply want to reduce the maximum the code that require order > 0 allocations for strict performance reasons. defrag is by far not a free operation, it even requires memcopies of the bulk data payload or swapouts. For the kernel stack btw, when alloc_pages(order=1) fails vmalloc should be used and 4k stacks can be dropped. Nobody does dma from the stack anymore these days IIRC (it doesn't work in all archs anyway).