On 10/17/2019 04:44 AM, Vincent Guittot wrote: > Hi Thara, > > On Wed, 16 Oct 2019 at 23:22, Thara Gopinath <[email protected]> > wrote: >> >> Hi Vincent, >> >> Thanks for the review >> On 10/14/2019 11:50 AM, Vincent Guittot wrote: >>> Hi Thara, >>> >>> On Mon, 14 Oct 2019 at 02:58, Thara Gopinath <[email protected]> >>> wrote: >>>> >>>> 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 <[email protected]> >>>> --- >>>> 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 >>>> <[email protected]> >>>> + */ >>>> + >>>> +#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); >>>> + } >>>> +} >>> >>> everything above seems to be there for the cpu cooling device and >>> should be included in it instead. The scheduler only need the capacity >>> capping >>> The cpu cooling device should just set the delta capacity in the >>> per-cpu variable (see my comment below) >> It can be a firmware updating the thermal pressure instead of cpu >> cooling device. Or may be some other entity .So instead of replicating >> this code, isnt't it better to reside in one place ? > > But you have now idea which kind of metrics will be provided by > firmware. It might not be a capped frequency and a max frequency but > other metrics. hmm. Why ? It is thermal pressure. It is finally applied to the scheduler metric cpu_capacity. It should not be anything other than capacity reduction due to thermal events that should be provided. > Also, __max_cap->max_capacity just save in a new per cpu struct the > return of arch_scale_cpu_capacity but this doesn't give us real > benefit I agree. I will change the struct into a single variable delta and initialize it to 0. populate_max_capacity_info need not be there. I will have update_maxcap_capacity calculate the delta with arch_scale_cpu_capacity and store it into a per cpu variable.
-- Warm Regards Thara
