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

Alexey Makhalov
2021-12-07T17:02:40Z

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> 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.

Thanks,
—-Alexey

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