From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754735AbYIESvr (ORCPT ); Fri, 5 Sep 2008 14:51:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751863AbYIESvg (ORCPT ); Fri, 5 Sep 2008 14:51:36 -0400 Received: from one.firstfloor.org ([213.235.205.2]:41647 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751640AbYIESvg (ORCPT ); Fri, 5 Sep 2008 14:51:36 -0400 Date: Fri, 5 Sep 2008 20:54:55 +0200 From: Andi Kleen To: Badari Pulavarty Cc: Andi Kleen , Gary Hade , linux-mm@kvack.org, Andrew Morton , Yasunori Goto , Mel Gorman , Chris McDermott , linux-kernel@vger.kernel.org, x86@kernel.org, Ingo Molnar Subject: Re: [PATCH] [RESEND] x86_64: add memory hotremove config option Message-ID: <20080905185455.GY18288@one.firstfloor.org> References: <20080905172132.GA11692@us.ibm.com> <87ej3yv588.fsf@basil.nowhere.org> <1220639514.25932.28.camel@badari-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1220639514.25932.28.camel@badari-desktop> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > At this time we are interested on node remove (on x86_64). > It doesn't really work well at this time - That's a quite euphemistic way to put it. > due to some of the structures That means you can never put any slab data on specific nodes. And all the kernel subsystems on that node will not ever get local memory. How are you going to solve that? And if you disallow kernel allocations in so large memory areas you get many of the highmem issues that plagued 32bit back in the 64bit kernel. There are lots of other issues. It's quite questionable if this whole exercise makes sense at all. > (BTW, on ppc64 this works fine - since we are interested mostly in > removing *some* sections of memory to give it back to hypervisor - > not entire node removal). Ok for hypervisors you can do it reasonably easy on x86 too, but it's likely that some hypercall interface is better than going through sysfs. -Andi