From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prarit Bhargava Subject: Re: [RFC PATCH]: ACPI: Automatically online hot-added memory Date: Wed, 10 Mar 2010 08:28:03 -0500 Message-ID: <4B979E63.1070806@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:20820 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756464Ab0CJN2E (ORCPT ); Wed, 10 Mar 2010 08:28:04 -0500 In-Reply-To: <1268186225.3606.25.camel@localhost.localdomain> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: ykzhao Cc: Matthew Garrett , "linux-acpi@vger.kernel.org" > > Why do we need to see whether the memory is onlined before bringing cpu > to online state? It seems that there is no dependency between cpu online > and memory online. > > Yakui, Here's a deeper look into the issue. New Intel processors have an on-die memory controller and this means that as the socket comes and goes, so does the memory "behind" the socket. ie) with new processors it is possible that an entire node which consists of memory and cpus comes and goes with the socket enable and disable. The cpu bringup code does local node allocations for the cpu. If the memory connected to the node (which is "behind" the socket) isn't online, then these allocations fail, and then the cpu bringup fails. P.