Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753455AbbDHKw1 (ORCPT ); Wed, 8 Apr 2015 06:52:27 -0400 Received: from casper.infradead.org ([85.118.1.10]:46127 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717AbbDHKwY (ORCPT ); Wed, 8 Apr 2015 06:52:24 -0400 Date: Wed, 8 Apr 2015 12:52:12 +0200 From: Peter Zijlstra To: Brice Goglin Cc: Nishanth Aravamudan , Ingo Molnar , linux-kernel@vger.kernel.org, Srikar Dronamraju , Boqun Feng , Anshuman Khandual , linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt , Anton Blanchard Subject: Re: Topology updates and NUMA-level sched domains Message-ID: <20150408105212.GP21418@twins.programming.kicks-ass.net> References: <20150406214558.GA38501@linux.vnet.ibm.com> <20150407102147.GJ23123@twins.programming.kicks-ass.net> <20150407171410.GA62529@linux.vnet.ibm.com> <20150407194129.GT23123@twins.programming.kicks-ass.net> <552503A1.3050502@inria.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <552503A1.3050502@inria.fr> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1149 Lines: 30 On Wed, Apr 08, 2015 at 12:32:01PM +0200, Brice Goglin wrote: > Le 07/04/2015 21:41, Peter Zijlstra a ?crit : > > No, that's very much not the same. Even if it were dealing with hotplug > > it would still assume the cpu to return to the same node. > > > > But mostly people do not even bother to handle hotplug. > > > > You said userspace assumes the cpu<->node relation is a boot-time fixed > one, and hotplug breaks this. I said no such thing. Regular hotplug actually respects that relation. > How do you expect userspace to handle hotplug? Mostly not. Why would they? CPU hotplug is rare and mostly a case of: don't do that then. Its just that some of the virt wankers are using it for resource management which is entirely misguided. Then again, most of virt is. > Is there a convenient way to be notified when a CPU (or memory) > is unplugged? I think you can poll some sysfs file or other. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/