On 05/23/2017 04:49 PM, Reza Arbab wrote:
> On Tue, May 23, 2017 at 03:05:08PM -0500, Michael Bringmann wrote:
>> On 05/23/2017 10:52 AM, Reza Arbab wrote:
>>> On Tue, May 23, 2017 at 10:15:44AM -0500, Michael Bringmann wrote:
>>>> +static void setup_nodes(void)
>>>> +{
>>>> + int i, l = 32 /* MAX_NUMNODES */;
>>>> +
>>>> + for (i = 0; i < l; i++) {
>>>> + if (!node_possible(i)) {
>>>> + setup_node_data(i, 0, 0);
>>>> + node_set(i, node_possible_map);
>>>> + }
>>>> + }
>>>> +}
>>>
>>> This seems to be a workaround for 3af229f2071f ("powerpc/numa: Reset
>>> node_possible_map to only node_online_map").
>>
>> They may be related, but that commit is not a replacement. The above patch
>> ensures that
>> there are enough of the nodes initialized at startup to allow for memory
>> hot-add into a
>> node that was not used at boot. (See 'setup_node_data' function in
>> 'numa.c'.) That and
>> recording that the node was initialized.
>
> Is it really necessary to preinitialize these empty nodes using
> setup_node_data()? When you do memory hotadd into a node that was not used at
> boot, the node data already gets set up by
>
> add_memory
> add_memory_resource
> hotadd_new_pgdat
> arch_alloc_nodedata <-- allocs the pg_data_t
> ...
> free_area_init_node <-- sets NODE_DATA(nid)->node_id, etc.
>
> Removing setup_node_data() from that loop leaves only the call to node_set().
> If 3af229f2071f (which reduces node_possible_map) was reverted, you wouldn't
> need to do that either.
With or without 3af229f2071f, we would still need to add something, somewhere
to add new
bits to the 'node_possible_map'. That is not being done.
>
>> I didn't see where any part of commit 3af229f2071f would touch the
>> 'node_possible_map'
>> which is needed by 'numa.c' and 'workqueue.c'. The nodemask created and
>> updated by
>> 'mem_cgroup_may_update_nodemask()' does not appear to be the same mask.
>
> Are you sure you're looking at 3af229f2071f? It only adds one line of code;
> the reduction of node_possible_map.
>
--
Michael W. Bringmann
Linux Technology Center
IBM Corporation
Tie-Line 363-5196
External: (512) 286-5196
Cell: (512) 466-0650
[email protected]
