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);