Merge branch 'slab/for-6.13/features' into slab/for-next

Merge the slab feature branch for 6.13:

- Add new slab_strict_numa parameter for per-object memory policies
  (Christoph Lameter)

Author: tehcaster

Documentation/admin-guide/kernel-parameters.txt

@@ -6147,6 +6147,16 @@
 			For more information see Documentation/mm/slub.rst.
 			(slub_nomerge legacy name also accepted for now)
 
+	slab_strict_numa	[MM]
+			Support memory policies on a per object level
+			in the slab allocator. The default is for memory
+			policies to be applied at the folio level when
+			a new folio is needed or a partial folio is
+			retrieved from the lists. Increases overhead
+			in the slab fastpaths but gains more accurate
+			NUMA kernel object placement which helps with slow
+			interconnects in NUMA systems.
+
 	slram=		[HW,MTD]
 
 	smart2=		[HW]

Documentation/mm/slub.rst

@@ -175,6 +175,15 @@ can be influenced by kernel parameters:
 	``slab_max_order`` to 0, what cause minimum possible order of
 	slabs allocation.
 
+``slab_strict_numa``
+        Enables the application of memory policies on each
+        allocation. This results in more accurate placement of
+        objects which may result in the reduction of accesses
+        to remote nodes. The default is to only apply memory
+        policies at the folio level when a new folio is acquired
+        or a folio is retrieved from the lists. Enabling this
+        option reduces the fastpath performance of the slab allocator.
+
 SLUB Debug output
 =================
 

mm/slub.c

@@ -218,6 +218,10 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
 #endif
 #endif		/* CONFIG_SLUB_DEBUG */
 
+#ifdef CONFIG_NUMA
+static DEFINE_STATIC_KEY_FALSE(strict_numa);
+#endif
+
 /* Structure holding parameters for get_partial() call chain */
 struct partial_context {
 	gfp_t flags;
@@ -3949,6 +3953,28 @@ static __always_inline void *__slab_alloc_node(struct kmem_cache *s,
 	object = c->freelist;
 	slab = c->slab;
 
+#ifdef CONFIG_NUMA
+	if (static_branch_unlikely(&strict_numa) &&
+			node == NUMA_NO_NODE) {
+
+		struct mempolicy *mpol = current->mempolicy;
+
+		if (mpol) {
+			/*
+			 * Special BIND rule support. If existing slab
+			 * is in permitted set then do not redirect
+			 * to a particular node.
+			 * Otherwise we apply the memory policy to get
+			 * the node we need to allocate on.
+			 */
+			if (mpol->mode != MPOL_BIND || !slab ||
+					!node_isset(slab_nid(slab), mpol->nodes))
+
+				node = mempolicy_slab_node();
+		}
+	}
+#endif
+
 	if (!USE_LOCKLESS_FAST_PATH() ||
 	    unlikely(!object || !slab || !node_match(slab, node))) {
 		object = __slab_alloc(s, gfpflags, node, addr, c, orig_size);
@@ -5715,6 +5741,23 @@ static int __init setup_slub_min_objects(char *str)
 __setup("slab_min_objects=", setup_slub_min_objects);
 __setup_param("slub_min_objects=", slub_min_objects, setup_slub_min_objects, 0);
 
+#ifdef CONFIG_NUMA
+static int __init setup_slab_strict_numa(char *str)
+{
+	if (nr_node_ids > 1) {
+		static_branch_enable(&strict_numa);
+		pr_info("SLUB: Strict NUMA enabled.\n");
+	} else {
+		pr_warn("slab_strict_numa parameter set on non NUMA system.\n");
+	}
+
+	return 1;
+}
+
+__setup("slab_strict_numa", setup_slab_strict_numa);
+#endif
+
+
 #ifdef CONFIG_HARDENED_USERCOPY
 /*
  * Rejects incorrectly sized objects and objects that are to be copied