Re: [RFC][PATCH 1/2] ARM64: add cpu topology definition

Hanjun Guo
2013-07-30T07:52:43Z

On 2013-7-29 17:46, Vincent Guittot wrote:
> On 27 July 2013 12:42, Hanjun Guo <hanjun.guo@linaro.org> wrote:
>> Power aware scheduling needs the cpu topology information to improve the
>> cpu scheduler decision making.
>
> It's not only power aware scheduling. The scheduler already uses
> topology and cache sharing when CONFIG_SCHED_MC and/or
> CONFIG_SCHED_SMT are enable. So you should also add these configs for
> arm64 so the scheduler can use it

Yes, you are right, thanks for the advice.

>
> Vincent
>
>>
>> For ARM64, we can get the topology from the MPIDR register which defines the
>> the affinity of processors.
>>
>> This patch is mainly based on arch/arm/kernel/topology.c written by
>> Vincent Guittot, and replaced the topology array with per cpu variable.
>>
>> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
>> ---
>> arch/arm64/Kconfig | 9 +++
>> arch/arm64/include/asm/cputype.h | 11 ++++
>> arch/arm64/include/asm/topology.h | 41 ++++++++++++
>> arch/arm64/kernel/Makefile | 1 +
>> arch/arm64/kernel/smp.c | 6 ++
>> arch/arm64/kernel/topology.c | 128 +++++++++++++++++++++++++++++++++++++
>> 6 files changed, 196 insertions(+)
>> create mode 100644 arch/arm64/include/asm/topology.h
>> create mode 100644 arch/arm64/kernel/topology.c
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 9737e97..f0ce91b 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -150,6 +150,15 @@ config SMP
>>
>> If you don't know what to do here, say N.
>>
>> +config ARM64_CPU_TOPOLOGY
>> + bool "Support cpu topology definition"
>> + depends on SMP && ARM64
>> + default y
>> + help
>> + Support ARM64 cpu topology definition. The MPIDR register defines
>> + affinity between processors which is then used to describe the cpu
>> + topology of an ARM64 System.
>> +
>> config NR_CPUS
>> int "Maximum number of CPUs (2-32)"
>> range 2 32
>> diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
>> index 5fe138e..68b55af 100644
>> --- a/arch/arm64/include/asm/cputype.h
>> +++ b/arch/arm64/include/asm/cputype.h
>> @@ -30,6 +30,17 @@
>>
>> #define MPIDR_HWID_BITMASK 0xff00ffffff
>>
>> +#define MPIDR_SMP_BITMASK (0x1 << 30)
>> +#define MPIDR_MT_BITMASK (0x1 << 24)
>> +
>> +#define MPIDR_LEVEL_BITS 8
>> +#define MPIDR_LEVEL_MASK ((1 << MPIDR_LEVEL_BITS) - 1)
>> +
>> +#define MPIDR_AFFINITY_LEVEL_0(mpidr) ((mpidr) & MPIDR_LEVEL_MASK)
>> +#define MPIDR_AFFINITY_LEVEL_1(mpidr) ((mpidr >> 8) & MPIDR_LEVEL_MASK)
>> +#define MPIDR_AFFINITY_LEVEL_2(mpidr) ((mpidr >> 16) & MPIDR_LEVEL_MASK)
>> +#define MPIDR_AFFINITY_LEVEL_3(mpidr) ((mpidr >> 32) & MPIDR_LEVEL_MASK)
>> +
>> #define read_cpuid(reg) ({ \
>> u64 __val; \
>> asm("mrs %0, " reg : "=r" (__val)); \
>> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
>> new file mode 100644
>> index 0000000..8631808
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/topology.h
>> @@ -0,0 +1,41 @@
>> +#ifndef _ASM_ARM64_TOPOLOGY_H
>> +#define _ASM_ARM64_TOPOLOGY_H
>> +
>> +#ifdef CONFIG_ARM64_CPU_TOPOLOGY
>> +
>> +#include <linux/cpumask.h>
>> +
>> +struct cputopo_arm64 {
>> + int thread_id;
>> + int core_id;
>> + int socket_id;
>> + cpumask_t thread_sibling;
>> + cpumask_t core_sibling;
>> +};
>> +
>> +DECLARE_PER_CPU(struct cputopo_arm64, cpu_topology);
>> +
>> +#define cpu_topo(cpu) per_cpu(cpu_topology, cpu)
>> +
>> +#define topology_physical_package_id(cpu) (cpu_topo(cpu).socket_id)
>> +#define topology_core_id(cpu) (cpu_topo(cpu).core_id)
>> +#define topology_core_cpumask(cpu) (&cpu_topo(cpu).core_sibling)
>> +#define topology_thread_cpumask(cpu) (&cpu_topo(cpu).thread_sibling)
>> +
>> +#define mc_capable() (cpu_topo(0).socket_id != -1)
>> +#define smt_capable() (cpu_topo(0).thread_id != -1)
>> +
>> +void init_cpu_topology(void);
>> +void store_cpu_topology(unsigned int cpuid);
>> +const struct cpumask *cpu_coregroup_mask(int cpu);
>> +
>> +#else
>> +
>> +static inline void init_cpu_topology(void) { }
>> +static inline void store_cpu_topology(unsigned int cpuid) { }
>> +
>> +#endif
>> +
>> +#include <asm-generic/topology.h>
>> +
>> +#endif /* _ASM_ARM64_TOPOLOGY_H */
>> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
>> index 7b4b564..a47c359 100644
>> --- a/arch/arm64/kernel/Makefile
>> +++ b/arch/arm64/kernel/Makefile
>> @@ -18,6 +18,7 @@ arm64-obj-$(CONFIG_SMP) += smp.o smp_spin_table.o smp_psci.o
>> arm64-obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o
>> arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)+= hw_breakpoint.o
>> arm64-obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
>> +arm64-obj-$(CONFIG_ARM64_CPU_TOPOLOGY) += topology.o
>>
>> obj-y += $(arm64-obj-y) vdso/
>> obj-m += $(arm64-obj-m)
>> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
>> index fee5cce..197b1da 100644
>> --- a/arch/arm64/kernel/smp.c
>> +++ b/arch/arm64/kernel/smp.c
>> @@ -39,6 +39,7 @@
>> #include <asm/atomic.h>
>> #include <asm/cacheflush.h>
>> #include <asm/cputype.h>
>> +#include <asm/topology.h>
>> #include <asm/mmu_context.h>
>> #include <asm/pgtable.h>
>> #include <asm/pgalloc.h>
>> @@ -215,6 +216,8 @@ asmlinkage void secondary_start_kernel(void)
>> local_irq_enable();
>> local_fiq_enable();
>>
>> + store_cpu_topology(cpu);
>> +
>> /*
>> * OK, it's off to the idle thread for us
>> */
>> @@ -387,6 +390,9 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
>> int cpu, err;
>> unsigned int ncores = num_possible_cpus();
>>
>> + init_cpu_topology();
>> + store_cpu_topology(smp_processor_id());
>> +
>> /*
>> * are we trying to boot more cores than exist?
>> */
>> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
>> new file mode 100644
>> index 0000000..1eb0435
>> --- /dev/null
>> +++ b/arch/arm64/kernel/topology.c
>> @@ -0,0 +1,128 @@
>> +/*
>> + * arch/arm64/kernel/topology.c
>> + *
>> + * Copyright (C) 2013 Linaro Limited.
>> + * Written by: Hanjun Guo
>> + *
>> + * based on arch/arm/kernel/topology.c
>> + *
>> + * This file is subject to the terms and conditions of the GNU General Public
>> + * License. See the file "COPYING" in the main directory of this archive
>> + * for more details.
>> + */
>> +
>> +#include <linux/cpu.h>
>> +#include <linux/cpumask.h>
>> +#include <linux/init.h>
>> +#include <linux/percpu.h>
>> +#include <linux/sched.h>
>> +
>> +#include <asm/cputype.h>
>> +#include <asm/topology.h>
>> +
>> +DEFINE_PER_CPU(struct cputopo_arm64, cpu_topology);
>> +
>> +const struct cpumask *cpu_coregroup_mask(int cpu)
>> +{
>> + return &cpu_topo(cpu).core_sibling;
>> +}
>> +
>> +void update_siblings_masks(unsigned int cpuid)
>> +{
>> + struct cputopo_arm64 *topo, *cpuid_topo = &cpu_topo(cpuid);
>> + int cpu;
>> +
>> + /* update core and thread sibling masks */
>> + for_each_possible_cpu(cpu) {
>> + topo = &cpu_topo(cpu);
>> +
>> + if (cpuid_topo->socket_id != topo->socket_id)
>> + continue;
>> +
>> + cpumask_set_cpu(cpuid, &topo->core_sibling);
>> + if (cpu != cpuid)
>> + cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
>> +
>> + if (cpuid_topo->core_id != topo->core_id)
>> + continue;
>> +
>> + cpumask_set_cpu(cpuid, &topo->thread_sibling);
>> + if (cpu != cpuid)
>> + cpumask_set_cpu(cpu, &cpuid_topo->thread_sibling);
>> + }
>> + smp_wmb();
>> +}
>> +
>> +/*
>> + * store_cpu_topology is called at boot when only one cpu is running
>> + * and with the mutex cpu_hotplug.lock locked, when several cpus have booted,
>> + * which prevents simultaneous write access to cpu_topology array
>> + */
>> +void store_cpu_topology(unsigned int cpuid)
>> +{
>> + struct cputopo_arm64 *cpuid_topo = &cpu_topo(cpuid);
>> + u64 mpidr;
>> +
>> + /* If the cpu topology has been already set, just return */
>> + if (cpuid_topo->core_id != -1)
>> + return;
>> +
>> + mpidr = read_cpuid_mpidr();
>> +
>> + /* create cpu topology mapping */
>> + if (!(mpidr & MPIDR_SMP_BITMASK)) {
>> + /*
>> + * This is a multiprocessor system
>> + * multiprocessor format & multiprocessor mode field are set
>> + */
>> +
>> + if (mpidr & MPIDR_MT_BITMASK) {
>> + /* core performance interdependency */
>> + cpuid_topo->thread_id = MPIDR_AFFINITY_LEVEL_0(mpidr);
>> + cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL_1(mpidr);
>> + cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL_2(mpidr);
>> + } else {
>> + /* largely independent cores */
>> + cpuid_topo->thread_id = -1;
>> + cpuid_topo->core_id = MPIDR_AFFINITY_LEVEL_0(mpidr);
>> + cpuid_topo->socket_id = MPIDR_AFFINITY_LEVEL_1(mpidr);
>> + }
>> + } else {
>> + /*
>> + * This is an uniprocessor system
>> + * we are in multiprocessor format but uniprocessor system
>> + * or in the old uniprocessor format
>> + */
>> + cpuid_topo->thread_id = -1;
>> + cpuid_topo->core_id = 0;
>> + cpuid_topo->socket_id = -1;
>> + }
>> +
>> + update_siblings_masks(cpuid);
>> +
>> + printk(KERN_INFO "CPU%u: thread %d, cpu %d, socket %d, mpidr 0x%llx\n",
>> + cpuid, cpu_topo(cpuid).thread_id,
>> + cpu_topo(cpuid).core_id,
>> + cpu_topo(cpuid).socket_id, mpidr);
>> +}
>> +
>> +/*
>> + * init_cpu_topology is called at boot when only one cpu is running
>> + * which prevent simultaneous write access to cpu_topology array
>> + */
>> +void __init init_cpu_topology(void)
>> +{
>> + unsigned int cpu;
>> +
>> + /* init core mask */
>> + for_each_possible_cpu(cpu) {
>> + struct cputopo_arm64 *topo = &cpu_topo(cpu);
>> +
>> + topo->thread_id = -1;
>> + topo->core_id = -1;
>> + topo->socket_id = -1;
>> + cpumask_clear(&topo->core_sibling);
>> + cpumask_clear(&topo->thread_sibling);
>> + }
>> + smp_wmb();
>> +}
>> --
>> 1.7.9.5
>>