Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751563AbVKBKls (ORCPT ); Wed, 2 Nov 2005 05:41:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751564AbVKBKls (ORCPT ); Wed, 2 Nov 2005 05:41:48 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:18063 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S1751562AbVKBKls (ORCPT ); Wed, 2 Nov 2005 05:41:48 -0500 Date: Wed, 2 Nov 2005 11:41:31 +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: <20051102104131.GA7780@elte.hu> References: <20051102071943.GA1574@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: 1398 Lines: 31 * 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). > There are two usage models here - those which intend to remove > physical elements and those where the kernel returnss management of > its virtualized "physical" memory to a hypervisor. In the latter > case, a hypervisor already maintains a virtual map of the memory and > the OS needs to release virtualized "physical" memory. I think you > are referring to RAM here as the physical component; however these > same defrag patches help where a hypervisor is maintaining the real > physical memory below the operating system and the OS is managing a > virtualized "physical" memory. 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. 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/