From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Date: Fri, 11 Jul 2014 23:51:01 +0000 Subject: Re: [RFC Patch V1 00/30] Enable memoryless node on x86 platforms Message-Id: <53C07865.2040103@zytor.com> List-Id: References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com> <20140711082956.GC20603@laptop.programming.kicks-ass.net> <20140711153314.GA6155@kroah.com> <8761j3ve8s.fsf@tassilo.jf.intel.com> In-Reply-To: <8761j3ve8s.fsf@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andi Kleen , Greg KH Cc: Jiang Liu , Peter Zijlstra , Andrew Morton , Mel Gorman , David Rientjes , Mike Galbraith , "Rafael J . Wysocki" , Tony Luck , linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org On 07/11/2014 01:20 PM, Andi Kleen wrote: > Greg KH writes: > >> On Fri, Jul 11, 2014 at 10:29:56AM +0200, Peter Zijlstra wrote: >>> On Fri, Jul 11, 2014 at 03:37:17PM +0800, Jiang Liu wrote: >>>> Any comments are welcomed! >>> >>> Why would anybody _ever_ have a memoryless node? That's ridiculous. >> >> I'm with Peter here, why would this be a situation that we should even >> support? Are there machines out there shipping like this? > > We've always had memory nodes. > > A classic case in the old days was a two socket system where someone > didn't populate any DIMMs on the second socket. > > There are other cases too. > Yes, like a node controller-based system where the system can be populated with either memory cards or CPU cards, for example. Now you can have both memoryless nodes and memory-only nodes... Memory-only nodes also happen in real life. In some cases they are done by permanently putting low-frequency CPUs to sleep for their memory controllers. -hpa From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f172.google.com (mail-yk0-f172.google.com [209.85.160.172]) by kanga.kvack.org (Postfix) with ESMTP id 731536B0035 for ; Fri, 11 Jul 2014 19:52:05 -0400 (EDT) Received: by mail-yk0-f172.google.com with SMTP id 10so376918ykt.31 for ; Fri, 11 Jul 2014 16:52:05 -0700 (PDT) Received: from mail.zytor.com (terminus.zytor.com. [2001:1868:205::10]) by mx.google.com with ESMTPS id a4si7542339yhd.129.2014.07.11.16.52.03 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 11 Jul 2014 16:52:04 -0700 (PDT) Message-ID: <53C07865.2040103@zytor.com> Date: Fri, 11 Jul 2014 16:51:01 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [RFC Patch V1 00/30] Enable memoryless node on x86 platforms References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com> <20140711082956.GC20603@laptop.programming.kicks-ass.net> <20140711153314.GA6155@kroah.com> <8761j3ve8s.fsf@tassilo.jf.intel.com> In-Reply-To: <8761j3ve8s.fsf@tassilo.jf.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andi Kleen , Greg KH Cc: Jiang Liu , Peter Zijlstra , Andrew Morton , Mel Gorman , David Rientjes , Mike Galbraith , "Rafael J . Wysocki" , Tony Luck , linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org On 07/11/2014 01:20 PM, Andi Kleen wrote: > Greg KH writes: > >> On Fri, Jul 11, 2014 at 10:29:56AM +0200, Peter Zijlstra wrote: >>> On Fri, Jul 11, 2014 at 03:37:17PM +0800, Jiang Liu wrote: >>>> Any comments are welcomed! >>> >>> Why would anybody _ever_ have a memoryless node? That's ridiculous. >> >> I'm with Peter here, why would this be a situation that we should even >> support? Are there machines out there shipping like this? > > We've always had memory nodes. > > A classic case in the old days was a two socket system where someone > didn't populate any DIMMs on the second socket. > > There are other cases too. > Yes, like a node controller-based system where the system can be populated with either memory cards or CPU cards, for example. Now you can have both memoryless nodes and memory-only nodes... Memory-only nodes also happen in real life. In some cases they are done by permanently putting low-frequency CPUs to sleep for their memory controllers. -hpa -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754580AbaGKXwN (ORCPT ); Fri, 11 Jul 2014 19:52:13 -0400 Received: from terminus.zytor.com ([198.137.202.10]:40473 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751056AbaGKXwL (ORCPT ); Fri, 11 Jul 2014 19:52:11 -0400 Message-ID: <53C07865.2040103@zytor.com> Date: Fri, 11 Jul 2014 16:51:01 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Andi Kleen , Greg KH CC: Jiang Liu , Peter Zijlstra , Andrew Morton , Mel Gorman , David Rientjes , Mike Galbraith , "Rafael J . Wysocki" , Tony Luck , linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC Patch V1 00/30] Enable memoryless node on x86 platforms References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com> <20140711082956.GC20603@laptop.programming.kicks-ass.net> <20140711153314.GA6155@kroah.com> <8761j3ve8s.fsf@tassilo.jf.intel.com> In-Reply-To: <8761j3ve8s.fsf@tassilo.jf.intel.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/11/2014 01:20 PM, Andi Kleen wrote: > Greg KH writes: > >> On Fri, Jul 11, 2014 at 10:29:56AM +0200, Peter Zijlstra wrote: >>> On Fri, Jul 11, 2014 at 03:37:17PM +0800, Jiang Liu wrote: >>>> Any comments are welcomed! >>> >>> Why would anybody _ever_ have a memoryless node? That's ridiculous. >> >> I'm with Peter here, why would this be a situation that we should even >> support? Are there machines out there shipping like this? > > We've always had memory nodes. > > A classic case in the old days was a two socket system where someone > didn't populate any DIMMs on the second socket. > > There are other cases too. > Yes, like a node controller-based system where the system can be populated with either memory cards or CPU cards, for example. Now you can have both memoryless nodes and memory-only nodes... Memory-only nodes also happen in real life. In some cases they are done by permanently putting low-frequency CPUs to sleep for their memory controllers. -hpa