[PATCH v6 01/10] mm,slub: Do not special case N_NORMAL nodes for slab_nodes

Oscar Salvador
2025-06-09T09:22:11Z

Currently, slab_mem_going_online_callback() checks whether the node has
N_NORMAL memory in order to be set in slab_nodes.
While it is true that getting rid of that enforcing would mean
ending up with movables nodes in slab_nodes, the memory waste that comes
with that is negligible.

So stop checking for status_change_nid_normal and just use status_change_nid
instead which works for both types of memory.

Also, once we allocate the kmem_cache_node cache for the node in
slab_mem_online_callback(), we never deallocate it in
slab_mem_offline_callback() when the node goes memoryless, so we can just
get rid of it.

The side effects are that we will stop clearing the node from slab_nodes,
and also that newly created kmem caches after node hotremove will now allocate
their kmem_cache_node for the node(s) that was hotremoved, but these
should be negligible.

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
mm/slub.c | 34 +++-------------------------------
1 file changed, 3 insertions(+), 31 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index be8b09e09d30..f92b43d36adc 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -447,7 +447,7 @@ static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)

/*
* Tracks for which NUMA nodes we have kmem_cache_nodes allocated.
- * Corresponds to node_state[N_NORMAL_MEMORY], but can temporarily
+ * Corresponds to node_state[N_MEMORY], but can temporarily
* differ during memory hotplug/hotremove operations.
* Protected by slab_mutex.
*/
@@ -6160,36 +6160,12 @@ static int slab_mem_going_offline_callback(void *arg)
return 0;
}

-static void slab_mem_offline_callback(void *arg)
-{
- struct memory_notify *marg = arg;
- int offline_node;
-
- offline_node = marg->status_change_nid_normal;
-
- /*
- * If the node still has available memory. we need kmem_cache_node
- * for it yet.
- */
- if (offline_node < 0)
- return;
-
- mutex_lock(&slab_mutex);
- node_clear(offline_node, slab_nodes);
- /*
- * We no longer free kmem_cache_node structures here, as it would be
- * racy with all get_node() users, and infeasible to protect them with
- * slab_mutex.
- */
- mutex_unlock(&slab_mutex);
-}
-
static int slab_mem_going_online_callback(void *arg)
{
struct kmem_cache_node *n;
struct kmem_cache *s;
struct memory_notify *marg = arg;
- int nid = marg->status_change_nid_normal;
+ int nid = marg->status_change_nid;
int ret = 0;

/*
@@ -6247,10 +6223,6 @@ static int slab_memory_callback(struct notifier_block *self,
case MEM_GOING_OFFLINE:
ret = slab_mem_going_offline_callback(arg);
break;
- case MEM_OFFLINE:
- case MEM_CANCEL_ONLINE:
- slab_mem_offline_callback(arg);
- break;
case MEM_ONLINE:
case MEM_CANCEL_OFFLINE:
break;
@@ -6321,7 +6293,7 @@ void __init kmem_cache_init(void)
* Initialize the nodemask for which we will allocate per node
* structures. Here we don't need taking slab_mutex yet.
*/
- for_each_node_state(node, N_NORMAL_MEMORY)
+ for_each_node_state(node, N_MEMORY)
node_set(node, slab_nodes);

create_boot_cache(kmem_cache_node, "kmem_cache_node",
--
2.49.0