From: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
To: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>,
linuxppc-dev@lists.ozlabs.org,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
Anton Blanchard <anton@samba.org>
Subject: Re: [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map
Date: Thu, 5 Mar 2015 15:15:55 -0800 [thread overview]
Message-ID: <20150305231555.GB30570@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1503051315270.25235@chino.kir.corp.google.com>
Hi David,
On 05.03.2015 [13:16:35 -0800], David Rientjes wrote:
> On Thu, 5 Mar 2015, Nishanth Aravamudan wrote:
>
> > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> > index 0257a7d659ef..24de29b3651b 100644
> > --- a/arch/powerpc/mm/numa.c
> > +++ b/arch/powerpc/mm/numa.c
> > @@ -958,9 +958,17 @@ void __init initmem_init(void)
> >
> > memblock_dump_all();
> >
> > + /*
> > + * zero out the possible nodes after we parse the device-tree,
> > + * so that we lower the maximum NUMA node ID to what is actually
> > + * present.
> > + */
> > + nodes_clear(node_possible_map);
> > +
> > for_each_online_node(nid) {
> > unsigned long start_pfn, end_pfn;
> >
> > + node_set(nid, node_possible_map);
> > get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
> > setup_node_data(nid, start_pfn, end_pfn);
> > sparse_memory_present_with_active_regions(nid);
>
> This seems a bit strange, node_possible_map is supposed to be a superset
> of node_online_map and this loop is iterating over node_online_map to set
> nodes in node_possible_map.
So if we compare to x86:
arch/x86/mm/numa.c::numa_init():
nodes_clear(numa_nodes_parsed);
nodes_clear(node_possible_map);
nodes_clear(node_online_map);
...
numa_register_memblks(...);
arch/x86/mm/numa.c::numa_register_memblks():
node_possible_map = numa_nodes_parsed;
Basically, it looks like x86 NUMA init clears out possible map and
online map, probably for a similar reason to what I gave in the
changelog that by default, the possible map seems to be based off
MAX_NUMNODES, rather than nr_node_ids or anything dynamic.
My patch was an attempt to emulate the same thing on powerpc. You are
right that there is a window in which the node_possible_map and
node_online_map are out of sync with my patch. It seems like it
shouldn't matter given how early in boot we are, but perhaps the
following would have been clearer:
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 0257a7d659ef..1a118b08fad2 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -958,6 +958,13 @@ void __init initmem_init(void)
memblock_dump_all();
+ /*
+ * Reduce the possible NUMA nodes to the online NUMA nodes,
+ * since we do not support node hotplug. This ensures that we
+ * lower the maximum NUMA node ID to what is actually present.
+ */
+ nodes_and(node_possible_map, node_possible_map, node_online_map);
+
for_each_online_node(nid) {
unsigned long start_pfn, end_pfn;
next prev parent reply other threads:[~2015-03-05 23:16 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-05 18:05 [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map Nishanth Aravamudan
2015-03-05 21:16 ` David Rientjes
2015-03-05 21:48 ` Michael Ellerman
2015-03-05 21:58 ` David Rientjes
2015-03-05 22:08 ` Tejun Heo
2015-03-05 22:18 ` Tejun Heo
2015-03-05 23:21 ` Nishanth Aravamudan
2015-03-05 23:24 ` Tejun Heo
2015-03-05 23:20 ` Nishanth Aravamudan
2015-03-05 23:17 ` Nishanth Aravamudan
2015-03-05 23:15 ` Nishanth Aravamudan [this message]
2015-03-05 23:29 ` David Rientjes
2015-03-06 5:27 ` [PATCH v2] powerpc/numa: set node_possible_map to only node_online_map during boot Nishanth Aravamudan
2015-03-06 11:29 ` Raghavendra K T
2015-03-09 23:55 ` Michael Ellerman
2015-03-10 23:50 ` [PATCH v3] " Nishanth Aravamudan
2015-03-05 22:13 ` [RFC PATCH] powerpc/numa: reset node_possible_map to only node_online_map Tejun Heo
2015-03-05 23:27 ` Nishanth Aravamudan
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