Messages in this thread | | | Subject | Re: [Patch v4 2/6] sched: Add infrastructure to store and update instantaneous thermal pressure | From | Thara Gopinath <> | Date | Wed, 30 Oct 2019 17:37:34 -0400 |
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Hello Peter, Thanks for the review.
On 10/28/2019 11:21 AM, Peter Zijlstra wrote: > On Tue, Oct 22, 2019 at 04:34:21PM -0400, Thara Gopinath 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 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. > > Please use a blank line at the end of a paragraph.
Will do
> >> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org> >> --- > >> 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 > > These are some tiny files, do these functions really need their own > little files?
I will merge them into fair.c. There will be update_thermal_pressure that will be called from cpu_cooling or other relevant framework. > > >> 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); > > Surely we can do without the pr_debug() here?
Will remove. I had it while developing to check if the thermal pressure is calculated correct. > >> + per_cpu(delta_capacity, cpu) = delta; >> +}
-- Warm Regards Thara
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