[RFC 4/6] sched: powerpc: create a dedicated topology table

[Vincent Guittot]

Create a dedicated topology table for handling asymetric feature.
The current proposal creates a new level which describes which groups of CPUs
take adavantge of SD_ASYM_PACKING. The useless level will be removed during the
build of the sched_domain topology.

Another solution would be to set SD_ASYM_PACKING in the sd_flags of SMT level
during the boot sequence and before the build of the sched_domain topology.

Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 arch/powerpc/kernel/smp.c |   35 +++++++++++++++++++++++++++--------
 kernel/sched/core.c       |    6 ------
 2 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index ac2621a..75da054 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -755,6 +755,32 @@ int setup_profiling_timer(unsigned int multiplier)
 	return 0;
 }
 
+#ifdef CONFIG_SCHED_SMT
+/* cpumask of CPUs with asymetric SMT dependancy */
+static const struct cpumask *cpu_asmt_mask(int cpu)
+{
+	if (cpu_has_feature(CPU_FTR_ASYM_SMT)) {
+		printk_once(KERN_INFO "Enabling Asymmetric SMT scheduling\n");
+		return topology_thread_cpumask(cpu);
+	}
+	return cpumask_of(cpu);
+}
+#endif
+
+static struct sched_domain_topology_level powerpc_topology[] = {
+#ifdef CONFIG_SCHED_SMT
+	{ cpu_asmt_mask, SD_SHARE_CPUPOWER | SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING, SD_INIT_NAME(ASMT) },
+	{ cpu_smt_mask, SD_SHARE_CPUPOWER | SD_SHARE_PKG_RESOURCES, SD_INIT_NAME(SMT) },
+#endif
+	{ cpu_cpu_mask, SD_INIT_NAME(DIE) },
+	{ NULL, },
+};
+
+static void __init set_sched_topology(void)
+{
+	sched_domain_topology = powerpc_topology;
+}
+
 void __init smp_cpus_done(unsigned int max_cpus)
 {
 	cpumask_var_t old_mask;
@@ -779,15 +805,8 @@ void __init smp_cpus_done(unsigned int max_cpus)
 
 	dump_numa_cpu_topology();
 
-}
+	set_sched_topology();
 
-int arch_sd_sibling_asym_packing(void)
-{
-	if (cpu_has_feature(CPU_FTR_ASYM_SMT)) {
-		printk_once(KERN_INFO "Enabling Asymmetric SMT scheduling\n");
-		return SD_ASYM_PACKING;
-	}
-	return 0;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3479467..7606de0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5818,11 +5818,6 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd)
 	atomic_set(&sg->sgp->nr_busy_cpus, sg->group_weight);
 }
 
-int __weak arch_sd_sibling_asym_packing(void)
-{
-       return 0*SD_ASYM_PACKING;
-}
-
 /*
  * Initializers for schedule domains
  * Non-inlined to reduce accumulated stack pressure in build_sched_domains()
@@ -6000,7 +5995,6 @@ sd_init(struct sched_domain_topology_level *tl, int cpu)
 	if (sd->flags & SD_SHARE_CPUPOWER) {
 		sd->imbalance_pct = 110;
 		sd->smt_gain = 1178; /* ~15% */
-		sd->flags |= arch_sd_sibling_asym_packing();
 
 	} else if (sd->flags & SD_SHARE_PKG_RESOURCES) {
 		sd->imbalance_pct = 117;
-- 
1.7.9.5

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