From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e39.co.us.ibm.com (e39.co.us.ibm.com [32.97.110.160]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id D91CF1A0814 for ; Thu, 22 May 2014 06:05:11 +1000 (EST) Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 21 May 2014 14:05:08 -0600 Received: from b03cxnp08026.gho.boulder.ibm.com (b03cxnp08026.gho.boulder.ibm.com [9.17.130.18]) by d03dlp03.boulder.ibm.com (Postfix) with ESMTP id 742AF19D8042 for ; Wed, 21 May 2014 14:05:00 -0600 (MDT) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by b03cxnp08026.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s4LK4Dw66816094 for ; Wed, 21 May 2014 22:04:13 +0200 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s4LK56BJ026267 for ; Wed, 21 May 2014 14:05:07 -0600 Date: Wed, 21 May 2014 13:04:51 -0700 From: Nishanth Aravamudan To: srivatsa.bhat@linux.vnet.ibm.com Subject: NUMA topology question wrt. d4edc5b6 Message-ID: <20140521200451.GB5755@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Srivatsa, After d4edc5b6 ("powerpc: Fix the setup of CPU-to-Node mappings during CPU online"), cpu_to_node() looks like: static inline int cpu_to_node(int cpu) { int nid; nid = numa_cpu_lookup_table[cpu]; /* * During early boot, the numa-cpu lookup table might not have been * setup for all CPUs yet. In such cases, default to node 0. */ return (nid < 0) ? 0 : nid; } However, I'm curious if this is correct in all cases. I have seen several LPARs that do not have any CPUs on node 0. In fact, because node 0 is statically set online in the initialization of the N_ONLINE nodemask, 0 is always present to Linux, whether it is present on the system. I'm not sure what the best thing to do here is, but I'm curious if you have any ideas? I would like to remove the static initialization of node 0, as it's confusing to users to see an empty node (particularly when it's completely separate in the numbering from other nodes), but we trip a panic (refer to: http://www.spinics.net/lists/linux-mm/msg73321.html). Thanks, Nish