Provide cpu_preferred_mask infrastructure. Define get/set macros which could be used to get/set CPU state as preferred.
PREFERRED_CPU config will be selected by the driver which handles steal time values. It is going to set/clear preferred CPU state. This driver will be called steal_governor and it is introduced in subsequent patches. It periodically samples the steal time and decides on preferred CPU state. A CPU is set to preferred when it becomes active. Later it may be marked as non-preferred depending on steal time values with steal_governor being enabled. Always maintain design construct of preferred is subset of active. i.e. preferred ⊆ active ⊆ online ⊆ present ⊆ possible With PREFERRED_CPU=n, ensure set_cpu_preferred is a nop and get method returns the active state in that case. Signed-off-by: Shrikanth Hegde <[email protected]> --- include/linux/cpumask.h | 24 ++++++++++++++++++++++++ kernel/Kconfig.preempt | 4 ++++ kernel/cpu.c | 6 ++++++ kernel/sched/core.c | 5 +++++ 4 files changed, 39 insertions(+) diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index d3cda0544954..34d08a3d80e1 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -122,12 +122,20 @@ extern struct cpumask __cpu_enabled_mask; extern struct cpumask __cpu_present_mask; extern struct cpumask __cpu_active_mask; extern struct cpumask __cpu_dying_mask; + +#ifdef CONFIG_PREFERRED_CPU +extern struct cpumask __cpu_preferred_mask; +#else +#define __cpu_preferred_mask __cpu_active_mask +#endif + #define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask) #define cpu_online_mask ((const struct cpumask *)&__cpu_online_mask) #define cpu_enabled_mask ((const struct cpumask *)&__cpu_enabled_mask) #define cpu_present_mask ((const struct cpumask *)&__cpu_present_mask) #define cpu_active_mask ((const struct cpumask *)&__cpu_active_mask) #define cpu_dying_mask ((const struct cpumask *)&__cpu_dying_mask) +#define cpu_preferred_mask ((const struct cpumask *)&__cpu_preferred_mask) extern atomic_t __num_online_cpus; extern unsigned int __num_possible_cpus; @@ -1164,6 +1172,12 @@ void init_cpu_possible(const struct cpumask *src); #define set_cpu_active(cpu, active) assign_cpu((cpu), &__cpu_active_mask, (active)) #define set_cpu_dying(cpu, dying) assign_cpu((cpu), &__cpu_dying_mask, (dying)) +#ifdef CONFIG_PREFERRED_CPU +#define set_cpu_preferred(cpu, preferred) assign_cpu((cpu), &__cpu_preferred_mask, (preferred)) +#else +#define set_cpu_preferred(cpu, preferred) do { } while (0) +#endif + void set_cpu_online(unsigned int cpu, bool online); void set_cpu_possible(unsigned int cpu, bool possible); @@ -1258,6 +1272,11 @@ static __always_inline bool cpu_dying(unsigned int cpu) return cpumask_test_cpu(cpu, cpu_dying_mask); } +static __always_inline bool cpu_preferred(unsigned int cpu) +{ + return cpumask_test_cpu(cpu, cpu_preferred_mask); +} + #else #define num_online_cpus() 1U @@ -1296,6 +1315,11 @@ static __always_inline bool cpu_dying(unsigned int cpu) return false; } +static __always_inline bool cpu_preferred(unsigned int cpu) +{ + return cpu == 0; +} + #endif /* NR_CPUS > 1 */ #define cpu_is_offline(cpu) unlikely(!cpu_online(cpu)) diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index 88c594c6d7fc..de789b274ba3 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -192,3 +192,7 @@ config SCHED_CLASS_EXT For more information: Documentation/scheduler/sched-ext.rst https://github.com/sched-ext/scx + +config PREFERRED_CPU + bool + depends on SMP && PARAVIRT diff --git a/kernel/cpu.c b/kernel/cpu.c index b3c8553d7bd6..376d297a6292 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -3103,6 +3103,11 @@ EXPORT_SYMBOL(__cpu_dying_mask); atomic_t __num_online_cpus __read_mostly; EXPORT_SYMBOL(__num_online_cpus); +#ifdef CONFIG_PREFERRED_CPU +struct cpumask __cpu_preferred_mask __read_mostly; +EXPORT_SYMBOL_GPL(__cpu_preferred_mask); +#endif + void init_cpu_present(const struct cpumask *src) { cpumask_copy(&__cpu_present_mask, src); @@ -3160,6 +3165,7 @@ void __init boot_cpu_init(void) /* Mark the boot cpu "present", "online" etc for SMP and UP case */ set_cpu_online(cpu, true); set_cpu_active(cpu, true); + set_cpu_preferred(cpu, true); set_cpu_present(cpu, true); set_cpu_possible(cpu, true); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2e7cde033a31..a45f7c308329 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8690,6 +8690,9 @@ int sched_cpu_activate(unsigned int cpu) */ sched_set_rq_online(rq, cpu); + /* preferred is subset of active and follows its state */ + set_cpu_preferred(cpu, true); + return 0; } @@ -8703,6 +8706,8 @@ int sched_cpu_deactivate(unsigned int cpu) if (ret) return ret; + set_cpu_preferred(cpu, false); + /* * Remove CPU from nohz.idle_cpus_mask to prevent participating in * load balancing when not active -- 2.47.3
