From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f172.google.com (mail-pd0-f172.google.com [209.85.192.172]) by kanga.kvack.org (Postfix) with ESMTP id 5DBE56B0073 for ; Tue, 11 Mar 2014 22:02:20 -0400 (EDT) Received: by mail-pd0-f172.google.com with SMTP id p10so379776pdj.3 for ; Tue, 11 Mar 2014 19:02:20 -0700 (PDT) Received: from mail-pd0-x230.google.com (mail-pd0-x230.google.com [2607:f8b0:400e:c02::230]) by mx.google.com with ESMTPS id nv9si702444pbb.335.2014.03.11.19.02.19 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 11 Mar 2014 19:02:19 -0700 (PDT) Received: by mail-pd0-f176.google.com with SMTP id r10so378158pdi.7 for ; Tue, 11 Mar 2014 19:02:19 -0700 (PDT) Date: Tue, 11 Mar 2014 19:02:17 -0700 (PDT) From: David Rientjes Subject: Re: Node 0 not necessary for powerpc? In-Reply-To: <20140311195632.GA946@linux.vnet.ibm.com> Message-ID: References: <20140311195632.GA946@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Nishanth Aravamudan Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, anton@samba.org, cl@linux.com, benh@kernel.crashing.org On Tue, 11 Mar 2014, Nishanth Aravamudan wrote: > I have a P7 system that has no node0, but a node0 shows up in numactl > --hardware, which has no cpus and no memory (and no PCI devices): > > numactl --hardware > available: 4 nodes (0-3) > node 0 cpus: > node 0 size: 0 MB > node 0 free: 0 MB > node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 > node 1 size: 0 MB > node 1 free: 0 MB > node 2 cpus: > node 2 size: 7935 MB > node 2 free: 7716 MB > node 3 cpus: > node 3 size: 8395 MB > node 3 free: 8015 MB > node distances: > node 0 1 2 3 > 0: 10 20 10 20 > 1: 20 10 20 20 > 2: 10 20 10 20 > 3: 20 20 20 10 > > This is because we statically initialize N_ONLINE to be [0] in > mm/page_alloc.c: > > [N_ONLINE] = { { [0] = 1UL } }, > > I'm not sure what the architectural requirements are here, but at least > on this test system, removing this initialization, it boots fine and is > running. I've not yet tried stress tests, but it's survived the > beginnings of kernbench so far. > > numactl --hardware > available: 3 nodes (1-3) > node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 > node 1 size: 0 MB > node 1 free: 0 MB > node 2 cpus: > node 2 size: 7935 MB > node 2 free: 7479 MB > node 3 cpus: > node 3 size: 8396 MB > node 3 free: 8375 MB > node distances: > node 1 2 3 > 1: 10 20 20 > 2: 20 10 20 > 3: 20 20 10 > > Perhaps we could put in a ARCH_DOES_NOT_NEED_NODE0 and only define it on > powerpc for now, conditionalizing the above initialization on that? > I don't know if anything has recently changed in the past year or so, but I've booted x86 machines with a hacked BIOS so that all memory on node 0 is hotpluggable and offline, so I believe this is possible on x86 as well. -- 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