sched/numa: Rewrite the CONFIG_NUMA sched domain support

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.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Anton Blanchard <anton@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: linux-alpha@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-sh@vger.kernel.org
Cc: Matt Turner <mattst88@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: sparclinux@vger.kernel.org
Cc: Tony Luck <tony.luck@intel.com>
Cc: x86@kernel.org
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Greg Pearson <greg.pearson@hp.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: bob.picco@oracle.com
Cc: chris.mason@oracle.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-r74n3n8hhuc2ynbrnp3vt954@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 185 insertions, 95 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6001e5c3b4e4..b4f2096980a3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5560,7 +5560,8 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
 			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(char *str)
 
 __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_topology_level *tl, int cpu) 	\
 }
 
 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_level default_topology[] = {
 	{ 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);