Message-ID: <274a6562-46c9-4b03-9295-c24e5eb9e6cd@arm.com>
Date:   Thu, 14 Dec 2023 08:31:19 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     catalin.marinas@....com, bristot@...hat.com,
        linux-pm@...r.kernel.org, juri.lelli@...hat.com, agross@...nel.org,
        viresh.kumar@...aro.org, rafael@...nel.org,
        linux-kernel@...r.kernel.org, rui.zhang@...el.com,
        dietmar.eggemann@....com, mgorman@...e.de,
        linux-trace-kernel@...r.kernel.org, mingo@...hat.com,
        peterz@...radead.org, konrad.dybcio@...aro.org,
        andersson@...nel.org, rostedt@...dmis.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, bsegall@...gle.com,
        vschneid@...hat.com, will@...nel.org, sudeep.holla@....com,
        daniel.lezcano@...aro.org, mhiramat@...nel.org,
        amit.kachhap@...il.com
Subject: Re: [PATCH 4/4] sched: Rename arch_update_thermal_pressure into
 arch_update_hw_pressure


On 12/12/23 14:27, Vincent Guittot wrote:
> Now that cpufreq provides a pressure value to the scheduler, rename
> arch_update_thermal_pressure into hw pressure to reflect that it returns
> a pressure applied by HW with a high frequency and which needs filtering.

I would elaborte this meaning 'filtering' here. Something like:
'... high frequency and which needs filtering to smooth the singal and
get an average value. That reflects available capacity of the CPU in
longer period'

> This pressure is not always related to thermal mitigation but can also be
> generated by max current limitation as an example.
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>   arch/arm/include/asm/topology.h               |  6 ++---
>   arch/arm64/include/asm/topology.h             |  6 ++---
>   drivers/base/arch_topology.c                  | 26 +++++++++----------
>   drivers/cpufreq/qcom-cpufreq-hw.c             |  4 +--
>   include/linux/arch_topology.h                 |  8 +++---
>   include/linux/sched/topology.h                |  8 +++---
>   .../{thermal_pressure.h => hw_pressure.h}     | 14 +++++-----
>   include/trace/events/sched.h                  |  2 +-
>   init/Kconfig                                  | 12 ++++-----
>   kernel/sched/core.c                           |  8 +++---
>   kernel/sched/fair.c                           | 12 ++++-----
>   kernel/sched/pelt.c                           | 18 ++++++-------
>   kernel/sched/pelt.h                           | 16 ++++++------
>   kernel/sched/sched.h                          |  4 +--
>   14 files changed, 72 insertions(+), 72 deletions(-)
>   rename include/trace/events/{thermal_pressure.h => hw_pressure.h} (55%)
> 
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index 853c4f81ba4a..e175e8596b5d 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -22,9 +22,9 @@
>   /* Enable topology flag updates */
>   #define arch_update_cpu_topology topology_update_cpu_topology
>   
> -/* Replace task scheduler's default thermal pressure API */
> -#define arch_scale_thermal_pressure topology_get_thermal_pressure
> -#define arch_update_thermal_pressure	topology_update_thermal_pressure
> +/* Replace task scheduler's default hw pressure API */
> +#define arch_scale_hw_pressure topology_get_hw_pressure
> +#define arch_update_hw_pressure	topology_update_hw_pressure
>   
>   #else
>   
> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> index a323b109b9c4..a427650bdfba 100644
> --- a/arch/arm64/include/asm/topology.h
> +++ b/arch/arm64/include/asm/topology.h
> @@ -35,9 +35,9 @@ void update_freq_counters_refs(void);
>   /* Enable topology flag updates */
>   #define arch_update_cpu_topology topology_update_cpu_topology
>   
> -/* Replace task scheduler's default thermal pressure API */
> -#define arch_scale_thermal_pressure topology_get_thermal_pressure
> -#define arch_update_thermal_pressure	topology_update_thermal_pressure
> +/* Replace task scheduler's default hw pressure API */

s/hw/HW/ ?

> +#define arch_scale_hw_pressure topology_get_hw_pressure
> +#define arch_update_hw_pressure	topology_update_hw_pressure
>   
>   #include <asm-generic/topology.h>
>   
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 0906114963ff..3d8dc9d5c3ad 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -22,7 +22,7 @@
>   #include <linux/units.h>
>   
>   #define CREATE_TRACE_POINTS
> -#include <trace/events/thermal_pressure.h>
> +#include <trace/events/hw_pressure.h>
>   
>   static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data);
>   static struct cpumask scale_freq_counters_mask;
> @@ -160,26 +160,26 @@ void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
>   	per_cpu(cpu_scale, cpu) = capacity;
>   }
>   
> -DEFINE_PER_CPU(unsigned long, thermal_pressure);
> +DEFINE_PER_CPU(unsigned long, hw_pressure);
>   
>   /**
> - * topology_update_thermal_pressure() - Update thermal pressure for CPUs
> + * topology_update_hw_pressure() - Update hw pressure for CPUs

same here: HW?

>    * @cpus        : The related CPUs for which capacity has been reduced
>    * @capped_freq : The maximum allowed frequency that CPUs can run at
>    *
> - * Update the value of thermal pressure for all @cpus in the mask. The
> + * Update the value of hw pressure for all @cpus in the mask. The

HW?

>    * cpumask should include all (online+offline) affected CPUs, to avoid
>    * operating on stale data when hot-plug is used for some CPUs. The
>    * @capped_freq reflects the currently allowed max CPUs frequency due to
> - * thermal capping. It might be also a boost frequency value, which is bigger
> + * hw capping. It might be also a boost frequency value, which is bigger

HW?

>    * than the internal 'capacity_freq_ref' max frequency. In such case the
>    * pressure value should simply be removed, since this is an indication that
> - * there is no thermal throttling. The @capped_freq must be provided in kHz.
> + * there is no hw throttling. The @capped_freq must be provided in kHz.

HW?

>    */
> -void topology_update_thermal_pressure(const struct cpumask *cpus,
> +void topology_update_hw_pressure(const struct cpumask *cpus,
>   				      unsigned long capped_freq)
>   {
> -	unsigned long max_capacity, capacity, th_pressure;
> +	unsigned long max_capacity, capacity, hw_pressure;
>   	u32 max_freq;
>   	int cpu;
>   
> @@ -189,21 +189,21 @@ void topology_update_thermal_pressure(const struct cpumask *cpus,
>   
>   	/*
>   	 * Handle properly the boost frequencies, which should simply clean
> -	 * the thermal pressure value.
> +	 * the hw pressure value.

HW?

>   	 */
>   	if (max_freq <= capped_freq)
>   		capacity = max_capacity;
>   	else
>   		capacity = mult_frac(max_capacity, capped_freq, max_freq);
>   
> -	th_pressure = max_capacity - capacity;
> +	hw_pressure = max_capacity - capacity;
>   
> -	trace_thermal_pressure_update(cpu, th_pressure);
> +	trace_hw_pressure_update(cpu, hw_pressure);
>   
>   	for_each_cpu(cpu, cpus)
> -		WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure);
> +		WRITE_ONCE(per_cpu(hw_pressure, cpu), hw_pressure);
>   }
> -EXPORT_SYMBOL_GPL(topology_update_thermal_pressure);
> +EXPORT_SYMBOL_GPL(topology_update_hw_pressure);
>   
>   static ssize_t cpu_capacity_show(struct device *dev,
>   				 struct device_attribute *attr,
> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> index 70b0f21968a0..a619202ba81d 100644
> --- a/drivers/cpufreq/qcom-cpufreq-hw.c
> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
> @@ -347,8 +347,8 @@ static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
>   
>   	throttled_freq = freq_hz / HZ_PER_KHZ;
>   
> -	/* Update thermal pressure (the boost frequencies are accepted) */
> -	arch_update_thermal_pressure(policy->related_cpus, throttled_freq);
> +	/* Update hw pressure (the boost frequencies are accepted) */

HW?

> +	arch_update_hw_pressure(policy->related_cpus, throttled_freq);
>   

[snip]

>   
>   	if (housekeeping_cpu(cpu, HK_TYPE_TICK))
> @@ -5669,8 +5669,8 @@ void scheduler_tick(void)
>   	rq_lock(rq, &rf);
>   
>   	update_rq_clock(rq);
> -	thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
> -	update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
> +	hw_pressure = arch_scale_hw_pressure(cpu_of(rq));
> +	update_hw_load_avg(rq_clock_task(rq), rq, hw_pressure);

We switch to task clock here, could you tell me why?
Don't we have to maintain the boot command parameter for the shift?

>   	curr->sched_class->task_tick(rq, curr, 0);
>   	if (sched_feat(LATENCY_WARN))
>   		resched_latency = cpu_resched_latency(rq);
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 11d3be829302..07050955d6e0 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4936,7 +4936,7 @@ static inline unsigned long get_actual_cpu_capacity(int cpu)
>   {
>   	unsigned long capacity = arch_scale_cpu_capacity(cpu);
>   
> -	capacity -= max(thermal_load_avg(cpu_rq(cpu)), cpufreq_get_pressure(cpu));
> +	capacity -= max(hw_load_avg(cpu_rq(cpu)), cpufreq_get_pressure(cpu));
>   
>   	return capacity;
>   }
> @@ -4968,7 +4968,7 @@ static inline int util_fits_cpu(unsigned long util,
>   	 * Similarly if a task is capped to arch_scale_cpu_capacity(little_cpu), it
>   	 * should fit a little cpu even if there's some pressure.
>   	 *
> -	 * Only exception is for thermal pressure since it has a direct impact
> +	 * Only exception is for hw or cpufreq pressure since it has a direct impact

HW?

>   	 * on available OPP of the system.
>   	 *
>   	 * We honour it for uclamp_min only as a drop in performance level
> @@ -9224,7 +9224,7 @@ static inline bool others_have_blocked(struct rq *rq)
>   	if (READ_ONCE(rq->avg_dl.util_avg))
>   		return true;
>   
> -	if (thermal_load_avg(rq))
> +	if (hw_load_avg(rq))
>   		return true;
>   
>   #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
> @@ -9256,7 +9256,7 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
>   {
>   	const struct sched_class *curr_class;
>   	u64 now = rq_clock_pelt(rq);
> -	unsigned long thermal_pressure;
> +	unsigned long hw_pressure;
>   	bool decayed;
>   
>   	/*
> @@ -9265,11 +9265,11 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
>   	 */
>   	curr_class = rq->curr->sched_class;
>   
> -	thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
> +	hw_pressure = arch_scale_hw_pressure(cpu_of(rq));
>   
>   	decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
>   		  update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
> -		  update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
> +		  update_hw_load_avg(now, rq, hw_pressure) |

Here also the rq_clock_thermal() is not used anymore. Shouldn't we
remove the rq_clock_thermal() if not used anymore (I cannot se this in
the patch)?

>   		  update_irq_load_avg(rq, 0);
>   
>   	if (others_have_blocked(rq))

[snip]

> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index e58a54bda77d..7eaf186d071e 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1078,8 +1078,8 @@ struct rq {
>   #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
>   	struct sched_avg	avg_irq;
>   #endif
> -#ifdef CONFIG_SCHED_THERMAL_PRESSURE
> -	struct sched_avg	avg_thermal;
> +#ifdef CONFIG_SCHED_HW_PRESSURE
> +	struct sched_avg	avg_hw;
>   #endif
>   	u64			idle_stamp;
>   	u64			avg_idle;

I don't see that rq_clock_thermal() removal in this header.
Maybe I miss some patch?

BTW, I like the name 'HW pressure' for this information/signal.

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