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