Re: [PATCH v3] mm: fix panic in __alloc_pages

David Hildenbrand
2021-12-07T17:14:03Z

On 07.12.21 18:02, Alexey Makhalov wrote:
>
>
>> On Dec 7, 2021, at 8:36 AM, Michal Hocko <mhocko@suse.com> wrote:
>>
>> On Tue 07-12-21 17:27:29, Michal Hocko wrote:
>> [...]
>>> So your proposal is to drop set_node_online from the patch and add it as
>>> a separate one which handles
>>> - sysfs part (i.e. do not register a node which doesn't span a
>>> physical address space)
>>> - hotplug side of (drop the pgd allocation, register node lazily
>>> when a first memblocks are registered)
>>
>> In other words, the first stage
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index c5952749ad40..f9024ba09c53 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -6382,7 +6382,11 @@ static void __build_all_zonelists(void *data)
>> if (self && !node_online(self->node_id)) {
>> build_zonelists(self);
>> } else {
>> - for_each_online_node(nid) {
>> + /*
>> + * All possible nodes have pgdat preallocated
>> + * free_area_init
>> + */
>> + for_each_node(nid) {
>> pg_data_t *pgdat = NODE_DATA(nid);
>>
>> build_zonelists(pgdat);
>
> Will it blow up memory usage for the nodes which might never be onlined?
> I prefer the idea of init on demand.
>
> Even now there is an existing problem.
> In my experiments, I observed _huge_ memory consumption increase by increasing number
> of possible numa nodes. I’m going to report it in separate mail thread.

I already raised that PPC might be problematic in that regard. Which
architecture / setup do you have in mind that can have a lot of possible
nodes?

--
Thanks,

David / dhildenb