Messages in this thread Patch in this message | | | From | Thara Gopinath <> | Subject | [Patch v4 2/6] sched: Add infrastructure to store and update instantaneous thermal pressure | Date | Tue, 22 Oct 2019 16:34:21 -0400 |
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Add thermal.c and thermal.h files that provides interface APIs to initialize, update/average, track, accumulate and decay thermal pressure per cpu basis. A per cpu variable delta_capacity 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. API trigger_thermal_pressure_average is called for periodic accumulate and decay of the thermal pressure. It is to to be called from a periodic tick function. This API passes on the instantaneous delta capacity of a cpu to update_thermal_load_avg to do the necessary accumulate, decay and average. API update_thermal_pressure is for the system to update the thermal pressure by providing a capped frequency ratio. Considering, trigger_thermal_pressure_average reads delta_capacity and update_thermal_pressure writes into delta_capacity, one can argue for some sort of locking mechanism to avoid a stale value. But considering trigger_thermal_pressure_average 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 delta_capacity 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> --- v3->v4: - Dropped per cpu max_capacity_info struct and instead added a per delta_capacity variable to store the delta between maximum capacity and capped capacity. The delta is now calculated when thermal pressure is updated and not every tick. - Dropped populate_max_capacity_info api as only per cpu delta capacity is stored. - Renamed update_periodic_maxcap to trigger_thermal_pressure_average and update_maxcap_capacity to update_thermal_pressure.
include/linux/sched.h | 8 ++++++++ kernel/sched/Makefile | 2 +- kernel/sched/thermal.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ kernel/sched/thermal.h | 13 +++++++++++++ 4 files changed, 67 insertions(+), 1 deletion(-) create mode 100644 kernel/sched/thermal.c create mode 100644 kernel/sched/thermal.h
diff --git a/include/linux/sched.h b/include/linux/sched.h index 2c2e56b..d7ef543 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1983,6 +1983,14 @@ static inline void rseq_syscall(struct pt_regs *regs) #endif +#ifdef CONFIG_SMP +void update_thermal_pressure(int cpu, u64 capacity); +#else +static inline void update_thermal_pressure(int cpu, u64 capacity) +{ +} +#endif + const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq); char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len); int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq); diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile index 21fb5a5..4d3b820 100644 --- a/kernel/sched/Makefile +++ b/kernel/sched/Makefile @@ -20,7 +20,7 @@ obj-y += core.o loadavg.o clock.o cputime.o obj-y += idle.o fair.o rt.o deadline.o obj-y += wait.o wait_bit.o swait.o completion.o -obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o pelt.o +obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o pelt.o thermal.o obj-$(CONFIG_SCHED_AUTOGROUP) += autogroup.o obj-$(CONFIG_SCHEDSTATS) += stats.o obj-$(CONFIG_SCHED_DEBUG) += debug.o diff --git a/kernel/sched/thermal.c b/kernel/sched/thermal.c new file mode 100644 index 0000000..0c84960 --- /dev/null +++ b/kernel/sched/thermal.c @@ -0,0 +1,45 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Scheduler Thermal Interactions + * + * Copyright (C) 2018 Linaro, Inc., Thara Gopinath <thara.gopinath@linaro.org> + */ + +#include <linux/sched.h> +#include "sched.h" +#include "pelt.h" +#include "thermal.h" + +static DEFINE_PER_CPU(unsigned long, delta_capacity); + +/** + * update_thermal_pressure: Update thermal pressure + * @cpu: the cpu for which thermal pressure is to be updated for + * @capped_freq_ratio: capped max frequency << SCHED_CAPACITY_SHIFT / max freq + * + * capped_freq_ratio is normalized into capped capacity and the delta between + * the arch_scale_cpu_capacity and capped capacity is stored in per cpu + * delta_capacity. + */ +void update_thermal_pressure(int cpu, u64 capped_freq_ratio) +{ + unsigned long __capacity, delta; + + /* Normalize the capped freq ratio */ + __capacity = (capped_freq_ratio * arch_scale_cpu_capacity(cpu)) >> + SCHED_CAPACITY_SHIFT; + delta = arch_scale_cpu_capacity(cpu) - __capacity; + pr_debug("updating cpu%d thermal pressure to %lu\n", cpu, delta); + + per_cpu(delta_capacity, cpu) = delta; +} + +/** + * trigger_thermal_pressure_average: Trigger the thermal pressure accumulate + * and average algorithm + */ +void trigger_thermal_pressure_average(struct rq *rq) +{ + update_thermal_load_avg(rq_clock_task(rq), rq, + per_cpu(delta_capacity, cpu_of(rq))); +} diff --git a/kernel/sched/thermal.h b/kernel/sched/thermal.h new file mode 100644 index 0000000..26e5b07 --- /dev/null +++ b/kernel/sched/thermal.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Scheduler thermal interaction internal methods. + */ + +#ifdef CONFIG_SMP +void trigger_thermal_pressure_average(struct rq *rq); + +#else +static inline void trigger_thermal_pressure_average(struct rq *rq) +{ +} +#endif -- 2.1.4
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