From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 5C34D6B01E3 for ; Sun, 16 May 2010 22:42:24 -0400 (EDT) Message-ID: <4BF0AD09.80404@linux.intel.com> Date: Mon, 17 May 2010 10:42:17 +0800 From: Haicheng Li MIME-Version: 1.0 Subject: Re: [RFC,5/7] NUMA hotplug emulator References: <20100513115625.GF2169@shaohui> <20100507141142.GA8696@ucw.cz> <20100516174502.GI2418@linux.vnet.ibm.com> In-Reply-To: <20100516174502.GI2418@linux.vnet.ibm.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: paulmck@linux.vnet.ibm.com Cc: Pavel Machek , akpm@linux-foundation.org, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Andi Kleen , Hidetoshi Seto , Len Brown , "Rafael J. Wysocki" , Yinghai Lu , Thomas Renninger , David Rientjes , Mel Gorman , Venkatesh Pallipadi , Alex Chiang , Tejun Heo , Christoph Lameter , Greg Kroah-Hartman , Stephen Rothwell , Benjamin Herrenschmidt , Shaohua Li , Hugh Dickins , James Bottomley , linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, linux-acpi@vger.kernel.org, fengguang.wu@intel.com, shaohui.zheng@linux.intel.com List-ID: Paul E. McKenney wrote: > On Fri, May 07, 2010 at 04:11:42PM +0200, Pavel Machek wrote: >> Hi! >> >>> hotplug emulator: Abstract cpu register functions >>> >>> Abstract function arch_register_cpu and register_cpu, move the implementation >>> details to a sub function with prefix "__". >>> >>> each of the sub function has an extra parameter nid, it can be used to register >>> CPU under a fake NUMA node, it is a reserved interface for cpu hotplug emulation >>> (CPU PROBE/RELEASE) in x86. >> I don't get it. CPU hotplug can already be tested using echo 0/1 > >> online, and that works on 386. How is this different? "echo 0/1 > online" is logical cpu online/offline. The emulator intends to emulate physical add/remove of cpus. They cover different code path. You can get details of the terms via $KERN_SRC/Documentation/cpu-hotplug.txt. >> It seems to add some numa magic. Why is it important? In real world, numa affinity info of the cpus is required for physical cpu hotadd/remove , which finally affects related data structures and code path. Emulator need the ability to emulate it. > My guess is that he wants to test the software surrounding NUMA on a > non-NUMA (or different-NUMA) machine, perhaps in order to shake out bugs > before the corresponding hardware is available. This is one of the purposes. Auto tests and debugging all can get benefits from such emulation. -haicheng -- 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