From: Thara Gopinath <thara.gopinath@linaro.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, ionela.voinescu@arm.com,
vincent.guittot@linaro.org, rui.zhang@intel.com,
edubezval@gmail.com, qperret@google.com,
linux-kernel@vger.kernel.org, amit.kachhap@gmail.com,
javi.merino@kernel.org, daniel.lezcano@linaro.org
Subject: Re: [Patch v4 2/6] sched: Add infrastructure to store and update instantaneous thermal pressure
Date: Wed, 30 Oct 2019 17:37:34 -0400 [thread overview]
Message-ID: <5DBA029E.8020508@linaro.org> (raw)
In-Reply-To: <20191028152135.GC4097@hirez.programming.kicks-ass.net>
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
next prev parent reply other threads:[~2019-10-30 21:37 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-22 20:34 [Patch v4 0/6] Introduce Thermal Pressure Thara Gopinath
2019-10-22 20:34 ` [Patch v4 1/6] sched/pelt.c: Add support to track thermal pressure Thara Gopinath
2019-10-31 9:47 ` Ionela Voinescu
2019-10-22 20:34 ` [Patch v4 2/6] sched: Add infrastructure to store and update instantaneous " Thara Gopinath
2019-10-28 15:21 ` Peter Zijlstra
2019-10-30 21:37 ` Thara Gopinath [this message]
2019-11-01 12:17 ` Dietmar Eggemann
2019-11-01 20:57 ` Thara Gopinath
2019-11-04 17:29 ` Dietmar Eggemann
2019-11-04 17:34 ` Vincent Guittot
2019-11-04 17:41 ` Dietmar Eggemann
2019-11-04 17:48 ` Vincent Guittot
2019-10-22 20:34 ` [Patch v4 3/6] sched/fair: Enable CFS periodic tick to update " Thara Gopinath
2019-10-28 15:24 ` Peter Zijlstra
2019-10-28 15:27 ` Peter Zijlstra
2019-10-30 21:41 ` Thara Gopinath
2019-10-31 16:11 ` Dietmar Eggemann
2019-10-31 16:46 ` Thara Gopinath
2019-10-22 20:34 ` [Patch v4 4/6] sched/fair: update cpu_capcity to reflect " Thara Gopinath
2019-10-23 12:28 ` Qais Yousef
2019-10-28 15:30 ` Peter Zijlstra
2019-10-31 10:53 ` Qais Yousef
2019-10-31 15:38 ` Dietmar Eggemann
2019-10-31 15:48 ` Vincent Guittot
2019-10-31 16:17 ` Dietmar Eggemann
2019-10-31 16:31 ` Vincent Guittot
2019-10-31 16:44 ` Dietmar Eggemann
2019-10-31 16:03 ` Thara Gopinath
2019-10-31 16:56 ` Qais Yousef
2019-10-22 20:34 ` [Patch v4 5/6] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping Thara Gopinath
2019-10-28 15:33 ` Peter Zijlstra
2019-10-31 16:29 ` Dietmar Eggemann
2019-10-31 16:38 ` Vincent Guittot
2019-11-01 15:47 ` Ionela Voinescu
2019-11-01 21:04 ` Thara Gopinath
2019-11-04 14:41 ` Ionela Voinescu
2019-10-31 16:46 ` Thara Gopinath
2019-10-22 20:34 ` [Patch v4 6/6] sched: thermal: Enable tuning of decay period Thara Gopinath
2019-10-28 15:42 ` Peter Zijlstra
2019-11-04 16:12 ` Ionela Voinescu
2019-11-05 20:26 ` Thara Gopinath
2019-11-05 21:29 ` Ionela Voinescu
2019-10-29 15:34 ` [Patch v4 0/6] Introduce Thermal Pressure Daniel Lezcano
2019-10-31 10:07 ` Ionela Voinescu
2019-10-31 11:54 ` Daniel Lezcano
2019-10-31 12:57 ` Ionela Voinescu
2019-10-31 17:48 ` Daniel Lezcano
2019-10-31 9:44 ` Ionela Voinescu
2019-10-31 16:41 ` Thara Gopinath
2019-10-31 16:52 ` Thara Gopinath
2019-11-05 21:04 ` Ionela Voinescu
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