From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 2 Nov 2005 11:41:31 +0100 From: Ingo Molnar 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: Sender: owner-linux-mm@kvack.org Return-Path: 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 List-ID: * 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org