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

Hi Vincent,

On 03/05/2014 12:48 PM, Vincent Guittot wrote:

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.

Is the below what you mean as the other solution? If it is so, I would strongly recommend this approach rather than adding another level to the topology level to represent the asymmetric behaviour.

+static struct sched_domain_topology_level powerpc_topology[] = { +#ifdef CONFIG_SCHED_SMT + { cpu_smt_mask, SD_SHARE_CPUPOWER | SD_SHARE_PKG_RESOURCES, SD_INIT_NAME(SMT) | arch_sd_sibling_asym_packing() }, +#endif + { cpu_cpu_mask, SD_INIT_NAME(DIE) }, + { NULL, }, +};

Regards Preeti U Murthy

Signed-off-by: Vincent Guittot vincent.guittot@linaro.org

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;