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 structure max_capacity_info is introduced to keep track of instantaneous per cpu thermal pressure. Thermal pressure is the delta between max_capacity and cap_capacity. API update_periodic_maxcap is called for periodic accumulate and decay of the thermal pressure. It is to to be called from a periodic tick function. This API calculates the delta between max_capacity and cap_capacity and passes on the delta to update_thermal_avg to do the necessary accumulate, decay and average. API update_maxcap_capacity is for the system to update the thermal pressure by updating cap_capacity. Considering, update_periodic_maxcap reads cap_capacity and update_maxcap_capacity writes into cap_capacity, one can argue for some sort of locking mechanism to avoid a stale value. But considering update_periodic_maxcap 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 value used to calculate average thermal pressure for a cpu can be stale for upto 1 tick period.
Signed-off-by: Thara Gopinath <thara.gopin...@linaro.org> --- include/linux/sched.h | 14 +++++++++++ kernel/sched/Makefile | 2 +- kernel/sched/thermal.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++ kernel/sched/thermal.h | 13 ++++++++++ 4 files changed, 94 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..875ce2b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1983,6 +1983,20 @@ static inline void rseq_syscall(struct pt_regs *regs) #endif +#ifdef CONFIG_SMP +void update_maxcap_capacity(int cpu, u64 capacity); + +void populate_max_capacity_info(void); +#else +static inline void update_maxcap_capacity(int cpu, u64 capacity) +{ +} + +static inline void populate_max_capacity_info(void) +{ +} +#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..5f0b2d4 --- /dev/null +++ b/kernel/sched/thermal.c @@ -0,0 +1,66 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Sceduler Thermal Interactions + * + * Copyright (C) 2018 Linaro, Inc., Thara Gopinath <thara.gopin...@linaro.org> + */ + +#include <linux/sched.h> +#include "sched.h" +#include "pelt.h" +#include "thermal.h" + +struct max_capacity_info { + unsigned long max_capacity; + unsigned long cap_capacity; +}; + +static DEFINE_PER_CPU(struct max_capacity_info, max_cap); + +void update_maxcap_capacity(int cpu, u64 capacity) +{ + struct max_capacity_info *__max_cap; + unsigned long __capacity; + + __max_cap = (&per_cpu(max_cap, cpu)); + if (!__max_cap) { + pr_err("no max_capacity_info structure for cpu %d\n", cpu); + return; + } + + /* Normalize the capacity */ + __capacity = (capacity * arch_scale_cpu_capacity(cpu)) >> + SCHED_CAPACITY_SHIFT; + pr_debug("updating cpu%d capped capacity from %lu to %lu\n", cpu, __max_cap->cap_capacity, __capacity); + + __max_cap->cap_capacity = __capacity; +} + +void populate_max_capacity_info(void) +{ + struct max_capacity_info *__max_cap; + u64 capacity; + int cpu; + + for_each_possible_cpu(cpu) { + __max_cap = (&per_cpu(max_cap, cpu)); + if (!__max_cap) + continue; + capacity = arch_scale_cpu_capacity(cpu); + __max_cap->max_capacity = capacity; + __max_cap->cap_capacity = capacity; + pr_debug("cpu %d max capacity set to %ld\n", cpu, __max_cap->max_capacity); + } +} + +void update_periodic_maxcap(struct rq *rq) +{ + struct max_capacity_info *__max_cap = (&per_cpu(max_cap, cpu_of(rq))); + unsigned long delta; + + if (!__max_cap) + return; + + delta = __max_cap->max_capacity - __max_cap->cap_capacity; + update_thermal_avg(rq_clock_task(rq), rq, delta); +} diff --git a/kernel/sched/thermal.h b/kernel/sched/thermal.h new file mode 100644 index 0000000..5657cb4 --- /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 update_periodic_maxcap(struct rq *rq); + +#else +static inline void update_periodic_maxcap(struct rq *rq) +{ +} +#endif -- 2.1.4