Hi Thara, On Thu, 17 Oct 2019 at 18:40, Thara Gopinath <[email protected]> wrote: > > 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.
What I mean is that you don't know how the value will be provided and if you will need a cap and a max value. It might easily provide directly the delta, or a percent or even something else > > 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. Also could you rename this function. You use thermal for the pelt function so could you align the function names ? either to use thermal everywhere or another name but could you not mix the naming If you want to use thermal why not using update_thermal_pressure ? at least it's easy to understand what it does > > > -- > Warm Regards > Thara
