Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932598AbVKBMBA (ORCPT ); Wed, 2 Nov 2005 07:01:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932650AbVKBMBA (ORCPT ); Wed, 2 Nov 2005 07:01:00 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:31891 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S932598AbVKBMA7 (ORCPT ); Wed, 2 Nov 2005 07:00:59 -0500 Date: Wed, 2 Nov 2005 13:00:48 +0100 From: Ingo Molnar To: Gerrit Huizenga Cc: Kamezawa Hiroyuki , Dave Hansen , Mel Gorman , Nick Piggin , "Martin J. Bligh" , Andrew Morton , kravetz@us.ibm.com, linux-mm , Linux Kernel Mailing List , lhms Subject: Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19 Message-ID: <20051102120048.GA10081@elte.hu> References: <20051102104131.GA7780@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=disabled SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1857 Lines: 44 * Gerrit Huizenga wrote: > > On Wed, 02 Nov 2005 11:41:31 +0100, Ingo Molnar wrote: > > > > * Gerrit Huizenga wrote: > > > > > > generic unpluggable kernel RAM _will not work_. > > > > > > Actually, it will. Well, depending on terminology. > > > > 'generic unpluggable kernel RAM' means what it says: any RAM seen by the > > kernel can be unplugged, always. (as long as the unplug request is > > reasonable and there is enough free space to migrate in-use pages to). > > Okay, I understand your terminology. Yes, I can not point to any > particular piece of memory and say "I want *that* one" and have that > request succeed. However, I can say "find me 50 chunks of memory > of your choosing" and have a very good chance of finding enough > memory to satisfy my request. but that's obviously not 'generic unpluggable kernel RAM'. It's very special RAM: RAM that is free or easily freeable. I never argued that such RAM is not returnable to the hypervisor. > > reliable unmapping of "generic kernel RAM" is not possible even in a > > virtualized environment. Think of the 'live pointers' problem i outlined > > in an earlier mail in this thread today. > > Yeah - and that isn't what is being proposed here. The goal is to > ask the kernel to identify some memory which can be legitimately > freed and hasten the freeing of that memory. but that's very easy to identify: check the free list or the clean list(s). No defragmentation necessary. [unless the unit of RAM mapping between hypervisor and guest is too coarse (i.e. not 4K pages).] Ingo - 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/