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

On 07.12.21 18:02, Alexey Makhalov wrote:

quoted

On Dec 7, 2021, at 8:36 AM, Michal Hocko [off-list ref] wrote:

On Tue 07-12-21 17:27:29, Michal Hocko wrote:
[...]

quoted

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