Subject: [RFC][PATCH 5/5] sched: Rewrite the CONFIG_NUMA sched domain support

From: Peter Zijlstra <[email-masked]>
Date: Tue, 01 May 2012 20:14:35 +0200

The current code groups up to 16 nodes in a level and then puts an
ALLNODES domain spanning the entire tree on top of that. This doesn't
reflect the numa topology and esp for the smaller not-fully-connected
machines out there today this might make a difference.

Therefore, build a proper numa topology based on node_distance().

Since there's no fixed numa layers anymore, the static SD_NODE_INIT
and SD_ALLNODES_INIT aren't usable anymore, the new code tries to
construct something similar and scales some values either on the
number of cpus in the domain and/or the node_distance() ratio.

Anton (IBM)/Dimitri (SGI)/Greg (HP)/Kamezawa-san (Fujitsu)/Oracle,
could I get node_distance() tables for your 'current' line-up of silly
large machines? You can get them by doing:

 $ cat /sys/devices/system/node/node*/distance

If this information is 'sekrit' please consider sending it privately.
If you're not the right person to ask, please redirect me.

Also, testing this code on your favourite large NUMA machine would be
most appreciated.

Cc: Anton Blanchard <[email-masked]>
Cc: Benjamin Herrenschmidt <[email-masked]>
Cc: Chris Metcalf <[email-masked]>
Cc: David Howells <[email-masked]>
Cc: "David S. Miller" <[email-masked]>
Cc: Fenghua Yu <[email-masked]>
Cc: "H. Peter Anvin" <[email-masked]>
Cc: Ingo Molnar <[email-masked]>
Cc: Ivan Kokshaysky <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: [email-masked]
Cc: Matt Turner <[email-masked]>
Cc: Paul Mackerras <[email-masked]>
Cc: Paul Mundt <[email-masked]>
Cc: Ralf Baechle <[email-masked]>
Cc: Richard Henderson <[email-masked]>
Cc: [email-masked]
Cc: Thomas Gleixner <[email-masked]>
Cc: Tony Luck <[email-masked]>
Cc: [email-masked]
Cc: Dimitri Sivanich <[email-masked]>
Cc: Greg Pearson <[email-masked]>
Cc: KAMEZAWA Hiroyuki <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Signed-off-by: Peter Zijlstra <[email-masked]>
---
 arch/ia64/include/asm/topology.h           |   25 --
 arch/mips/include/asm/mach-ip27/topology.h |   17 -
 arch/powerpc/include/asm/topology.h        |   36 ---
 arch/sh/include/asm/topology.h             |   25 --
 arch/sparc/include/asm/topology_64.h       |   19 -
 arch/tile/include/asm/topology.h           |   26 --
 arch/x86/include/asm/topology.h            |   38 ---
 include/linux/topology.h                   |   37 ---
 kernel/sched/core.c                        |  280 +++++++++++++++++++----------
 9 files changed, 185 insertions(+), 318 deletions(-)

--- a/arch/ia64/include/asm/topology.h
+++ b/arch/ia64/include/asm/topology.h
@@ -70,31 +70,6 @@ void build_cpu_to_node_map(void);
 	.nr_balance_failed	= 0,			\
 }
 
-/* sched_domains SD_NODE_INIT for IA64 NUMA machines */
-#define SD_NODE_INIT (struct sched_domain) {		\
-	.parent			= NULL,			\
-	.child			= NULL,			\
-	.groups			= NULL,			\
-	.min_interval		= 8,			\
-	.max_interval		= 8*(min(num_online_cpus(), 32U)), \
-	.busy_factor		= 64,			\
-	.imbalance_pct		= 125,			\
-	.cache_nice_tries	= 2,			\
-	.busy_idx		= 3,			\
-	.idle_idx		= 2,			\
-	.newidle_idx		= 0,			\
-	.wake_idx		= 0,			\
-	.forkexec_idx		= 0,			\
-	.flags			= SD_LOAD_BALANCE	\
-				| SD_BALANCE_NEWIDLE	\
-				| SD_BALANCE_EXEC	\
-				| SD_BALANCE_FORK	\
-				| SD_SERIALIZE,		\
-	.last_balance		= jiffies,		\
-	.balance_interval	= 64,			\
-	.nr_balance_failed	= 0,			\
-}
-
 #endif /* CONFIG_NUMA */
 
 #ifdef CONFIG_SMP
--- a/arch/mips/include/asm/mach-ip27/topology.h
+++ b/arch/mips/include/asm/mach-ip27/topology.h
@@ -36,23 +36,6 @@ extern unsigned char __node_distances[MA
 
 #define node_distance(from, to)	(__node_distances[(from)][(to)])
 
-/* sched_domains SD_NODE_INIT for SGI IP27 machines */
-#define SD_NODE_INIT (struct sched_domain) {		\
-	.parent			= NULL,			\
-	.child			= NULL,			\
-	.groups			= NULL,			\
-	.min_interval		= 8,			\
-	.max_interval		= 32,			\
-	.busy_factor		= 32,			\
-	.imbalance_pct		= 125,			\
-	.cache_nice_tries	= 1,			\
-	.flags			= SD_LOAD_BALANCE |	\
-				  SD_BALANCE_EXEC,	\
-	.last_balance		= jiffies,		\
-	.balance_interval	= 1,			\
-	.nr_balance_failed	= 0,			\
-}
-
 #include <asm-generic/topology.h>
 
 #endif /* _ASM_MACH_TOPOLOGY_H */
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -18,12 +18,6 @@ struct device_node;
  */
 #define RECLAIM_DISTANCE 10
 
-/*
- * Avoid creating an extra level of balancing (SD_ALLNODES) on the largest
- * POWER7 boxes which have a maximum of 32 nodes.
- */
-#define SD_NODES_PER_DOMAIN 32
-
 #include <asm/mmzone.h>
 
 static inline int cpu_to_node(int cpu)
@@ -51,36 +45,6 @@ static inline int pcibus_to_node(struct
 				 cpu_all_mask :				\
 				 cpumask_of_node(pcibus_to_node(bus)))
 
-/* sched_domains SD_NODE_INIT for PPC64 machines */
-#define SD_NODE_INIT (struct sched_domain) {				\
-	.min_interval		= 8,					\
-	.max_interval		= 32,					\
-	.busy_factor		= 32,					\
-	.imbalance_pct		= 125,					\
-	.cache_nice_tries	= 1,					\
-	.busy_idx		= 3,					\
-	.idle_idx		= 1,					\
-	.newidle_idx		= 0,					\
-	.wake_idx		= 0,					\
-	.forkexec_idx		= 0,					\
-									\
-	.flags			= 1*SD_LOAD_BALANCE			\
-				| 0*SD_BALANCE_NEWIDLE			\
-				| 1*SD_BALANCE_EXEC			\
-				| 1*SD_BALANCE_FORK			\
-				| 0*SD_BALANCE_WAKE			\
-				| 1*SD_WAKE_AFFINE			\
-				| 0*SD_PREFER_LOCAL			\
-				| 0*SD_SHARE_CPUPOWER			\
-				| 0*SD_POWERSAVINGS_BALANCE		\
-				| 0*SD_SHARE_PKG_RESOURCES		\
-				| 1*SD_SERIALIZE			\
-				| 0*SD_PREFER_SIBLING			\
-				,					\
-	.last_balance		= jiffies,				\
-	.balance_interval	= 1,					\
-}
-
 extern int __node_distance(int, int);
 #define node_distance(a, b) __node_distance(a, b)
 
--- a/arch/sh/include/asm/topology.h
+++ b/arch/sh/include/asm/topology.h
@@ -3,31 +3,6 @@
 
 #ifdef CONFIG_NUMA
 
-/* sched_domains SD_NODE_INIT for sh machines */
-#define SD_NODE_INIT (struct sched_domain) {		\
-	.parent			= NULL,			\
-	.child			= NULL,			\
-	.groups			= NULL,			\
-	.min_interval		= 8,			\
-	.max_interval		= 32,			\
-	.busy_factor		= 32,			\
-	.imbalance_pct		= 125,			\
-	.cache_nice_tries	= 2,			\
-	.busy_idx		= 3,			\
-	.idle_idx		= 2,			\
-	.newidle_idx		= 0,			\
-	.wake_idx		= 0,			\
-	.forkexec_idx		= 0,			\
-	.flags			= SD_LOAD_BALANCE	\
-				| SD_BALANCE_FORK	\
-				| SD_BALANCE_EXEC	\
-				| SD_BALANCE_NEWIDLE	\
-				| SD_SERIALIZE,		\
-	.last_balance		= jiffies,		\
-	.balance_interval	= 1,			\
-	.nr_balance_failed	= 0,			\
-}
-
 #define cpu_to_node(cpu)	((void)(cpu),0)
 #define parent_node(node)	((void)(node),0)
 
--- a/arch/sparc/include/asm/topology_64.h
+++ b/arch/sparc/include/asm/topology_64.h
@@ -31,25 +31,6 @@ static inline int pcibus_to_node(struct
 	 cpu_all_mask : \
 	 cpumask_of_node(pcibus_to_node(bus)))
 
-#define SD_NODE_INIT (struct sched_domain) {		\
-	.min_interval		= 8,			\
-	.max_interval		= 32,			\
-	.busy_factor		= 32,			\
-	.imbalance_pct		= 125,			\
-	.cache_nice_tries	= 2,			\
-	.busy_idx		= 3,			\
-	.idle_idx		= 2,			\
-	.newidle_idx		= 0, 			\
-	.wake_idx		= 0,			\
-	.forkexec_idx		= 0,			\
-	.flags			= SD_LOAD_BALANCE	\
-				| SD_BALANCE_FORK	\
-				| SD_BALANCE_EXEC	\
-				| SD_SERIALIZE,		\
-	.last_balance		= jiffies,		\
-	.balance_interval	= 1,			\
-}
-
 #else /* CONFIG_NUMA */
 
 #include <asm-generic/topology.h>
--- a/arch/tile/include/asm/topology.h
+++ b/arch/tile/include/asm/topology.h
@@ -78,32 +78,6 @@ static inline const struct cpumask *cpum
 	.balance_interval	= 32,					\
 }
 
-/* sched_domains SD_NODE_INIT for TILE architecture */
-#define SD_NODE_INIT (struct sched_domain) {				\
-	.min_interval		= 16,					\
-	.max_interval		= 512,					\
-	.busy_factor		= 32,					\
-	.imbalance_pct		= 125,					\
-	.cache_nice_tries	= 1,					\
-	.busy_idx		= 3,					\
-	.idle_idx		= 1,					\
-	.newidle_idx		= 2,					\
-	.wake_idx		= 1,					\
-	.flags			= 1*SD_LOAD_BALANCE			\
-				| 1*SD_BALANCE_NEWIDLE			\
-				| 1*SD_BALANCE_EXEC			\
-				| 1*SD_BALANCE_FORK			\
-				| 0*SD_BALANCE_WAKE			\
-				| 0*SD_WAKE_AFFINE			\
-				| 0*SD_PREFER_LOCAL			\
-				| 0*SD_SHARE_CPUPOWER			\
-				| 0*SD_SHARE_PKG_RESOURCES		\
-				| 1*SD_SERIALIZE			\
-				,					\
-	.last_balance		= jiffies,				\
-	.balance_interval	= 128,					\
-}
-
 /* By definition, we create nodes based on online memory. */
 #define node_has_online_mem(nid) 1
 
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -92,44 +92,6 @@ extern void setup_node_to_cpumask_map(vo
 
 #define pcibus_to_node(bus) __pcibus_to_node(bus)
 
-#ifdef CONFIG_X86_32
-# define SD_CACHE_NICE_TRIES	1
-# define SD_IDLE_IDX		1
-#else
-# define SD_CACHE_NICE_TRIES	2
-# define SD_IDLE_IDX		2
-#endif
-
-/* sched_domains SD_NODE_INIT for NUMA machines */
-#define SD_NODE_INIT (struct sched_domain) {				\
-	.min_interval		= 8,					\
-	.max_interval		= 32,					\
-	.busy_factor		= 32,					\
-	.imbalance_pct		= 125,					\
-	.cache_nice_tries	= SD_CACHE_NICE_TRIES,			\
-	.busy_idx		= 3,					\
-	.idle_idx		= SD_IDLE_IDX,				\
-	.newidle_idx		= 0,					\
-	.wake_idx		= 0,					\
-	.forkexec_idx		= 0,					\
-									\
-	.flags			= 1*SD_LOAD_BALANCE			\
-				| 1*SD_BALANCE_NEWIDLE			\
-				| 1*SD_BALANCE_EXEC			\
-				| 1*SD_BALANCE_FORK			\
-				| 0*SD_BALANCE_WAKE			\
-				| 1*SD_WAKE_AFFINE			\
-				| 0*SD_PREFER_LOCAL			\
-				| 0*SD_SHARE_CPUPOWER			\
-				| 0*SD_POWERSAVINGS_BALANCE		\
-				| 0*SD_SHARE_PKG_RESOURCES		\
-				| 1*SD_SERIALIZE			\
-				| 0*SD_PREFER_SIBLING			\
-				,					\
-	.last_balance		= jiffies,				\
-	.balance_interval	= 1,					\
-}
-
 extern int __node_distance(int, int);
 #define node_distance(a, b) __node_distance(a, b)
 
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -70,7 +70,6 @@ int arch_update_cpu_topology(void);
  * Below are the 3 major initializers used in building sched_domains:
  * SD_SIBLING_INIT, for SMT domains
  * SD_CPU_INIT, for SMP domains
- * SD_NODE_INIT, for NUMA domains
  *
  * Any architecture that cares to do any tuning to these values should do so
  * by defining their own arch-specific initializer in include/asm/topology.h.
@@ -176,48 +175,12 @@ int arch_update_cpu_topology(void);
 }
 #endif
 
-/* sched_domains SD_ALLNODES_INIT for NUMA machines */
-#define SD_ALLNODES_INIT (struct sched_domain) {			\
-	.min_interval		= 64,					\
-	.max_interval		= 64*num_online_cpus(),			\
-	.busy_factor		= 128,					\
-	.imbalance_pct		= 133,					\
-	.cache_nice_tries	= 1,					\
-	.busy_idx		= 3,					\
-	.idle_idx		= 3,					\
-	.flags			= 1*SD_LOAD_BALANCE			\
-				| 1*SD_BALANCE_NEWIDLE			\
-				| 0*SD_BALANCE_EXEC			\
-				| 0*SD_BALANCE_FORK			\
-				| 0*SD_BALANCE_WAKE			\
-				| 0*SD_WAKE_AFFINE			\
-				| 0*SD_SHARE_CPUPOWER			\
-				| 0*SD_POWERSAVINGS_BALANCE		\
-				| 0*SD_SHARE_PKG_RESOURCES		\
-				| 1*SD_SERIALIZE			\
-				| 0*SD_PREFER_SIBLING			\
-				,					\
-	.last_balance		= jiffies,				\
-	.balance_interval	= 64,					\
-}
-
-#ifndef SD_NODES_PER_DOMAIN
-#define SD_NODES_PER_DOMAIN 16
-#endif
-
 #ifdef CONFIG_SCHED_BOOK
 #ifndef SD_BOOK_INIT
 #error Please define an appropriate SD_BOOK_INIT in include/asm/topology.h!!!
 #endif
 #endif /* CONFIG_SCHED_BOOK */
 
-#ifdef CONFIG_NUMA
-#ifndef SD_NODE_INIT
-#error Please define an appropriate SD_NODE_INIT in include/asm/topology.h!!!
-#endif
-
-#endif /* CONFIG_NUMA */
-
 #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
 DECLARE_PER_CPU(int, numa_node);
 
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5560,7 +5560,8 @@ static int sched_domain_debug_one(struct
 			break;
 		}
 
-		if (cpumask_intersects(groupmask, sched_group_cpus(group))) {
+		if (!(sd->flags & SD_OVERLAP) &&
+		    cpumask_intersects(groupmask, sched_group_cpus(group))) {
 			printk(KERN_CONT "\n");
 			printk(KERN_ERR "ERROR: repeated CPUs\n");
 			break;
@@ -5898,92 +5899,6 @@ static int __init isolated_cpu_setup(cha
 
 __setup("isolcpus=", isolated_cpu_setup);
 
-#ifdef CONFIG_NUMA
-
-/**
- * find_next_best_node - find the next node to include in a sched_domain
- * @node: node whose sched_domain we're building
- * @used_nodes: nodes already in the sched_domain
- *
- * Find the next node to include in a given scheduling domain. Simply
- * finds the closest node not already in the @used_nodes map.
- *
- * Should use nodemask_t.
- */
-static int find_next_best_node(int node, nodemask_t *used_nodes)
-{
-	int i, n, val, min_val, best_node = -1;
-
-	min_val = INT_MAX;
-
-	for (i = 0; i < nr_node_ids; i++) {
-		/* Start at @node */
-		n = (node + i) % nr_node_ids;
-
-		if (!nr_cpus_node(n))
-			continue;
-
-		/* Skip already used nodes */
-		if (node_isset(n, *used_nodes))
-			continue;
-
-		/* Simple min distance search */
-		val = node_distance(node, n);
-
-		if (val < min_val) {
-			min_val = val;
-			best_node = n;
-		}
-	}
-
-	if (best_node != -1)
-		node_set(best_node, *used_nodes);
-	return best_node;
-}
-
-/**
- * sched_domain_node_span - get a cpumask for a node's sched_domain
- * @node: node whose cpumask we're constructing
- * @span: resulting cpumask
- *
- * Given a node, construct a good cpumask for its sched_domain to span. It
- * should be one that prevents unnecessary balancing, but also spreads tasks
- * out optimally.
- */
-static void sched_domain_node_span(int node, struct cpumask *span)
-{
-	nodemask_t used_nodes;
-	int i;
-
-	cpumask_clear(span);
-	nodes_clear(used_nodes);
-
-	cpumask_or(span, span, cpumask_of_node(node));
-	node_set(node, used_nodes);
-
-	for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
-		int next_node = find_next_best_node(node, &used_nodes);
-		if (next_node < 0)
-			break;
-		cpumask_or(span, span, cpumask_of_node(next_node));
-	}
-}
-
-static const struct cpumask *cpu_node_mask(int cpu)
-{
-	lockdep_assert_held(&sched_domains_mutex);
-
-	sched_domain_node_span(cpu_to_node(cpu), sched_domains_tmpmask);
-
-	return sched_domains_tmpmask;
-}
-
-static const struct cpumask *cpu_allnodes_mask(int cpu)
-{
-	return cpu_possible_mask;
-}
-#endif /* CONFIG_NUMA */
-
 static const struct cpumask *cpu_cpu_mask(int cpu)
 {
 	return cpumask_of_node(cpu_to_node(cpu));
@@ -6020,6 +5935,7 @@ struct sched_domain_topology_level {
 	sched_domain_init_f init;
 	sched_domain_mask_f mask;
 	int		    flags;
+	int		    numa_level;
 	struct sd_data      data;
 };
 
@@ -6213,10 +6129,6 @@ sd_init_##type(struct sched_domain_topol
 }
 
 SD_INIT_FUNC(CPU)
-#ifdef CONFIG_NUMA
- SD_INIT_FUNC(ALLNODES)
- SD_INIT_FUNC(NODE)
-#endif
 #ifdef CONFIG_SCHED_SMT
  SD_INIT_FUNC(SIBLING)
 #endif
@@ -6338,15 +6250,191 @@ static struct sched_domain_topology_leve
 	{ sd_init_BOOK, cpu_book_mask, },
 #endif
 	{ sd_init_CPU, cpu_cpu_mask, },
-#ifdef CONFIG_NUMA
-	{ sd_init_NODE, cpu_node_mask, SDTL_OVERLAP, },
-	{ sd_init_ALLNODES, cpu_allnodes_mask, },
-#endif
 	{ NULL, },
 };
 
 static struct sched_domain_topology_level *sched_domain_topology = default_topology;
 
+#ifdef CONFIG_NUMA
+
+static int sched_domains_numa_levels;
+static int sched_domains_numa_scale;
+static int *sched_domains_numa_distance;
+static struct cpumask ***sched_domains_numa_masks;
+static int sched_domains_curr_level;
+
+static inline unsigned long numa_scale(unsigned long x, int level)
+{
+	return x * sched_domains_numa_distance[level] / sched_domains_numa_scale;
+}
+
+static inline int sd_local_flags(int level)
+{
+	if (sched_domains_numa_distance[level] > REMOTE_DISTANCE)
+		return 0;
+
+	return SD_BALANCE_EXEC | SD_BALANCE_FORK | SD_WAKE_AFFINE;
+}
+
+static struct sched_domain *
+sd_numa_init(struct sched_domain_topology_level *tl, int cpu)
+{
+	struct sched_domain *sd = *per_cpu_ptr(tl->data.sd, cpu);
+	int level = tl->numa_level;
+	int sd_weight = cpumask_weight(
+			sched_domains_numa_masks[level][cpu_to_node(cpu)]);
+
+	*sd = (struct sched_domain){
+		.min_interval		= sd_weight,
+		.max_interval		= 2*sd_weight,
+		.busy_factor		= 32,
+		.imbalance_pct		= 100 + numa_scale(25, level),
+		.cache_nice_tries	= 2,
+		.busy_idx		= 3,
+		.idle_idx		= 2,
+		.newidle_idx		= 0,
+		.wake_idx		= 0,
+		.forkexec_idx		= 0,
+
+		.flags			= 1*SD_LOAD_BALANCE
+					| 1*SD_BALANCE_NEWIDLE
+					| 0*SD_BALANCE_EXEC
+					| 0*SD_BALANCE_FORK
+					| 0*SD_BALANCE_WAKE
+					| 0*SD_WAKE_AFFINE
+					| 0*SD_PREFER_LOCAL
+					| 0*SD_SHARE_CPUPOWER
+					| 0*SD_POWERSAVINGS_BALANCE
+					| 0*SD_SHARE_PKG_RESOURCES
+					| 1*SD_SERIALIZE
+					| 0*SD_PREFER_SIBLING
+					| sd_local_flags(level)
+					,
+		.last_balance		= jiffies,
+		.balance_interval	= sd_weight,
+	};
+	SD_INIT_NAME(sd, NUMA);
+	sd->private = &tl->data;
+
+	/*
+	 * Ugly hack to pass state to sd_numa_mask()...
+	 */
+	sched_domains_curr_level = tl->numa_level;
+
+	return sd;
+}
+
+static const struct cpumask *sd_numa_mask(int cpu)
+{
+	return sched_domains_numa_masks[sched_domains_curr_level][cpu_to_node(cpu)];
+}
+
+static void sched_init_numa(void)
+{
+	int next_distance, curr_distance = node_distance(0, 0);
+	struct sched_domain_topology_level *tl;
+	int level = 0;
+	int i, j, k;
+
+	sched_domains_numa_scale = curr_distance;
+	sched_domains_numa_distance = kzalloc(sizeof(int) * nr_node_ids, GFP_KERNEL);
+	if (!sched_domains_numa_distance)
+		return;
+
+	/*
+	 * O(nr_nodes^2) deduplicating selection sort -- in order to find the
+	 * unique distances in the node_distance() table.
+	 *
+	 * Assumes node_distance(0,j) includes all distances in
+	 * node_distance(i,j) in order to avoid cubic time.
+	 *
+	 * XXX: could be optimized to O(n log n) by using sort()
+	 */
+	next_distance = curr_distance;
+	for (i = 0; i < nr_node_ids; i++) {
+		for (j = 0; j < nr_node_ids; j++) {
+			int distance = node_distance(0, j);
+			if (distance > curr_distance &&
+					(distance < next_distance ||
+					 next_distance == curr_distance))
+				next_distance = distance;
+		}
+		if (next_distance != curr_distance) {
+			sched_domains_numa_distance[level++] = next_distance;
+			sched_domains_numa_levels = level;
+			curr_distance = next_distance;
+		} else break;
+	}
+	/*
+	 * 'level' contains the number of unique distances, excluding the
+	 * identity distance node_distance(i,i).
+	 *
+	 * The sched_domains_nume_distance[] array includes the actual distance
+	 * numbers.
+	 */
+
+	sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL);
+	if (!sched_domains_numa_masks)
+		return;
+
+	/*
+	 * Now for each level, construct a mask per node which contains all
+	 * cpus of nodes that are that many hops away from us.
+	 */
+	for (i = 0; i < level; i++) {
+		sched_domains_numa_masks[i] =
+			kzalloc(nr_node_ids * sizeof(void *), GFP_KERNEL);
+		if (!sched_domains_numa_masks[i])
+			return;
+
+		for (j = 0; j < nr_node_ids; j++) {
+			struct cpumask *mask = kzalloc_node(cpumask_size(), GFP_KERNEL, j);
+			if (!mask)
+				return;
+
+			sched_domains_numa_masks[i][j] = mask;
+
+			for (k = 0; k < nr_node_ids; k++) {
+				if (node_distance(cpu_to_node(j), k) >
+						sched_domains_numa_distance[i])
+					continue;
+
+				cpumask_or(mask, mask, cpumask_of_node(k));
+			}
+		}
+	}
+
+	tl = kzalloc((ARRAY_SIZE(default_topology) + level) *
+			sizeof(struct sched_domain_topology_level), GFP_KERNEL);
+	if (!tl)
+		return;
+
+	/*
+	 * Copy the default topology bits..
+	 */
+	for (i = 0; default_topology[i].init; i++)
+		tl[i] = default_topology[i];
+
+	/*
+	 * .. and append 'j' levels of NUMA goodness.
+	 */
+	for (j = 0; j < level; i++, j++) {
+		tl[i] = (struct sched_domain_topology_level){
+			.init = sd_numa_init,
+			.mask = sd_numa_mask,
+			.flags = SDTL_OVERLAP,
+			.numa_level = j,
+		};
+	}
+
+	sched_domain_topology = tl;
+}
+#else
+static inline void sched_init_numa(void)
+{
+}
+#endif /* CONFIG_NUMA */
+
 static int __sdt_alloc(const struct cpumask *cpu_map)
 {
 	struct sched_domain_topology_level *tl;
@@ -6840,6 +6928,8 @@ void __init sched_init_smp(void)
 	alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
 	alloc_cpumask_var(&fallback_doms, GFP_KERNEL);
 
+	sched_init_numa();
+
 	get_online_cpus();
 	mutex_lock(&sched_domains_mutex);
 	init_sched_domains(cpu_active_mask);