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

Alexey Makhalov
2021-12-07T17:17:36Z

> On Dec 7, 2021, at 9:13 AM, David Hildenbrand <david@redhat.com> wrote:
>
> 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?
>
It is x86_64 VMware VM, not the regular one, but specially configured (1 vCPU per node,
with hot-plug support, 128 possible nodes)

Thanks,
—-Alexey