Messages in this thread Patch in this message | | | From | Thara Gopinath <> | Subject | [Patch v7 3/7] arm,arm64,drivers:Add infrastructure to store and update instantaneous thermal pressure | Date | Sat, 11 Jan 2020 10:59:02 -0500 |
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Add architecture specific APIs to update and track thermal pressure on a per cpu basis. A per cpu variable thermal_pressure is introduced to keep track of instantaneous per cpu thermal pressure. Thermal pressure is the delta between maximum capacity and capped capacity due to a thermal event.
topology_get_thermal_pressure can be hooked into the scheduler specified arch_cpu_thermal_capacity to retrieve instantaneous thermal pressure of a cpu.
arch_set_thermal_pressure can be used to update the thermal pressure.
Considering topology_get_thermal_pressure reads thermal_pressure and arch_set_thermal_pressure writes into thermal_pressure, one can argue for some sort of locking mechanism to avoid a stale value. But considering topology_get_thermal_pressure can be called from a system critical path like scheduler tick function, a locking mechanism is not ideal. This means that it is possible the thermal_pressure value used to calculate average thermal pressure for a cpu can be stale for upto 1 tick period.
Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org> ---
v6->v7: - Changed the input argument in arch_set_thermal_pressure from capped capacity to delta capacity(thermal pressure) as per Ionela's review comments.
arch/arm/include/asm/topology.h | 3 +++ arch/arm64/include/asm/topology.h | 3 +++ drivers/base/arch_topology.c | 11 +++++++++++ include/linux/arch_topology.h | 10 ++++++++++ 4 files changed, 27 insertions(+)
diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h index 8a0fae9..3a50a19 100644 --- a/arch/arm/include/asm/topology.h +++ b/arch/arm/include/asm/topology.h @@ -16,6 +16,9 @@ /* Enable topology flag updates */ #define arch_update_cpu_topology topology_update_cpu_topology +/* Replace task scheduler's default thermal pressure retrieve API */ +#define arch_cpu_thermal_pressure topology_get_thermal_pressure + #else static inline void init_cpu_topology(void) { } diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h index a4d945d..a70896f 100644 --- a/arch/arm64/include/asm/topology.h +++ b/arch/arm64/include/asm/topology.h @@ -25,6 +25,9 @@ int pcibus_to_node(struct pci_bus *bus); /* Enable topology flag updates */ #define arch_update_cpu_topology topology_update_cpu_topology +/* Replace task scheduler's default thermal pressure retrieve API */ +#define arch_cpu_thermal_pressure topology_get_thermal_pressure + #include <asm-generic/topology.h> #endif /* _ASM_ARM_TOPOLOGY_H */ diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 1eb81f11..c2c5f1d 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -42,6 +42,17 @@ void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity) per_cpu(cpu_scale, cpu) = capacity; } +DEFINE_PER_CPU(unsigned long, thermal_pressure); + +void arch_set_thermal_pressure(struct cpumask *cpus, + unsigned long th_pressure) +{ + int cpu; + + for_each_cpu(cpu, cpus) + WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure); +} + static ssize_t cpu_capacity_show(struct device *dev, struct device_attribute *attr, char *buf) diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h index 3015ecb..88a115e 100644 --- a/include/linux/arch_topology.h +++ b/include/linux/arch_topology.h @@ -33,6 +33,16 @@ unsigned long topology_get_freq_scale(int cpu) return per_cpu(freq_scale, cpu); } +DECLARE_PER_CPU(unsigned long, thermal_pressure); + +static inline unsigned long topology_get_thermal_pressure(int cpu) +{ + return per_cpu(thermal_pressure, cpu); +} + +void arch_set_thermal_pressure(struct cpumask *cpus, + unsigned long th_pressure); + struct cpu_topology { int thread_id; int core_id; -- 2.1.4
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