From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: Re: [RFC PATCH]: ACPI: Automatically online hot-added memory Date: Thu, 11 Mar 2010 06:25:07 -0500 Message-ID: <4B98D313.4080509@redhat.com> References: <20100309141203.10037.62453.sendpatchset@prarit.bos.redhat.com> <20100309154243.GA26520@srcf.ucam.org> <4B969305.9070103@redhat.com> <1268186225.3606.25.camel@localhost.localdomain> <4B979E63.1070806@redhat.com> <1268268915.3606.101.camel@localhost.localdomain> <4B985311.8090708@redhat.com> <1268294876.3632.5.camel@localhost.localdomain> <4B98AA89.4060609@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:3733 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751949Ab0CKLZN (ORCPT ); Thu, 11 Mar 2010 06:25:13 -0500 In-Reply-To: <4B98AA89.4060609@linux.intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: chen gong Cc: ykzhao , Matthew Garrett , "linux-acpi@vger.kernel.org" , trenn@novell.com chen gong wrote: > On 2010-3-11 16:07, ykzhao wrote: > >> On Thu, 2010-03-11 at 10:18 +0800, Prarit Bhargava wrote: >> >>>> Yes. The nehalem processor has the integrated memory controller. But it >>>> is not required that the hot-added memory should be onlined before >>>> bringing up CPU. >>>> I do the following memory-hotplug test on one Machine. >>>> a. Before hot plugging memory, four CPUs socket are installed and >>>> all the logical CPU are brought up. (Only one node has the memory) >>>> b. The memory is hot-plugged and then the memory is onlined so that >>>> it can be accessed by the system. >>>> >>>> In the above testing case the CPU is brought up before onlining the >>>> hot-added memory. And the test shows that it can work well. >>>> >>>> >>> That doesn't work when you have multiple nodes AFAICT. The cpus do not >>> come into service because of a lack of memory on the node.... per node >>> allocations will fail. >>> >> In the test the system has multiple nodes. The reason is that the cpu >> without memory can turn to other node and allocate the memory. >> > > I agree with Yakui. The memory and CPU are irrelevant in some way. CPU can > get memory from other nodes if it hasn't local memory, though for now it has some issues. > Andi is working on it now (http://lkml.org/lkml/2010/2/3/343) > Right -- I'm working with Andi on this to get RHEL working. So I have his slab patches, etc.. That's one of the reasons it isn't working right now. > BTW, how about using UDEV rules to do this operation. It looks more smooth. I know some > Novell guy is working on it. > > I was thinking about that, but the CPU comes online automatically, so why not memory? It seems to be a discrepancy between the two. And ... the two of you still aren't considering the obvious performance hit which I would think makes this a must have. P. >