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Message-ID: <5de717f7-dd64-5584-540a-e0b86a431dde@linaro.org>
Date: Tue, 16 Nov 2021 18:39:36 -0500
From: Thara Gopinath <thara.gopinath@...aro.org>
To: Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org,
linux-arm-msm@...r.kernel.org, steev@...i.org,
sudeep.holla@....com, will@...nel.org, catalin.marinas@....com,
linux@...linux.org.uk, gregkh@...uxfoundation.org,
rafael@...nel.org, viresh.kumar@...aro.org, amitk@...nel.org,
daniel.lezcano@...aro.org, amit.kachhap@...il.com,
bjorn.andersson@...aro.org, agross@...nel.org
Subject: Re: [PATCH v4 1/5] arch_topology: Introduce thermal pressure update
function
On 11/9/21 2:57 PM, Lukasz Luba wrote:
> The thermal pressure is a mechanism which is used for providing
> information about reduced CPU performance to the scheduler. Usually code
> has to convert the value from frequency units into capacity units,
> which are understandable by the scheduler. Create a common conversion code
> which can be just used via a handy API.
>
> Internally, the topology_update_thermal_pressure() operates on frequency
> in MHz and max CPU frequency is taken from 'freq_factor' (per-cpu).
>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
Reviewed-by: Thara Gopinath <thara.gopinath@...aro.org>
--
Warm Regards
Thara (She/Her/Hers)
> ---
> arch/arm/include/asm/topology.h | 1 +
> arch/arm64/include/asm/topology.h | 1 +
> drivers/base/arch_topology.c | 43 ++++++++++++++++++++++++++++++-
> include/linux/arch_topology.h | 3 +++
> include/linux/sched/topology.h | 7 +++++
> 5 files changed, 54 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index 470299ee2fba..f1eafacc9a30 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -24,6 +24,7 @@
> /* Replace task scheduler's default thermal pressure API */
> #define arch_scale_thermal_pressure topology_get_thermal_pressure
> #define arch_set_thermal_pressure topology_set_thermal_pressure
> +#define arch_update_thermal_pressure topology_update_thermal_pressure
>
> #else
>
> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> index ec2db3419c41..7a421cbc99ed 100644
> --- a/arch/arm64/include/asm/topology.h
> +++ b/arch/arm64/include/asm/topology.h
> @@ -33,6 +33,7 @@ void update_freq_counters_refs(void);
> /* Replace task scheduler's default thermal pressure API */
> #define arch_scale_thermal_pressure topology_get_thermal_pressure
> #define arch_set_thermal_pressure topology_set_thermal_pressure
> +#define arch_update_thermal_pressure topology_update_thermal_pressure
>
> #include <asm-generic/topology.h>
>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index fc0836f460fb..bed7d502c9a1 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -25,6 +25,7 @@
> static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data);
> static struct cpumask scale_freq_counters_mask;
> static bool scale_freq_invariant;
> +static DEFINE_PER_CPU(u32, freq_factor) = 1;
>
> static bool supports_scale_freq_counters(const struct cpumask *cpus)
> {
> @@ -168,6 +169,47 @@ void topology_set_thermal_pressure(const struct cpumask *cpus,
> }
> EXPORT_SYMBOL_GPL(topology_set_thermal_pressure);
>
> +/**
> + * topology_update_thermal_pressure() - Update thermal pressure for CPUs
> + * @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
> + * 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
> + * than the internal 'freq_factor' 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.
> + */
> +void topology_update_thermal_pressure(const struct cpumask *cpus,
> + unsigned long capped_freq)
> +{
> + unsigned long max_capacity, capacity;
> + u32 max_freq;
> + int cpu;
> +
> + cpu = cpumask_first(cpus);
> + max_capacity = arch_scale_cpu_capacity(cpu);
> + max_freq = per_cpu(freq_factor, cpu);
> +
> + /* Convert to MHz scale which is used in 'freq_factor' */
> + capped_freq /= 1000;
> +
> + /*
> + * Handle properly the boost frequencies, which should simply clean
> + * the thermal pressure value.
> + */
> + if (max_freq <= capped_freq)
> + capacity = max_capacity;
> + else
> + capacity = mult_frac(max_capacity, capped_freq, max_freq);
> +
> + arch_set_thermal_pressure(cpus, max_capacity - capacity);
> +}
> +EXPORT_SYMBOL_GPL(topology_update_thermal_pressure);
> +
> static ssize_t cpu_capacity_show(struct device *dev,
> struct device_attribute *attr,
> char *buf)
> @@ -220,7 +262,6 @@ static void update_topology_flags_workfn(struct work_struct *work)
> update_topology = 0;
> }
>
> -static DEFINE_PER_CPU(u32, freq_factor) = 1;
> static u32 *raw_capacity;
>
> static int free_raw_capacity(void)
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index b97cea83b25e..ace1e5dcf773 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -59,6 +59,9 @@ static inline unsigned long topology_get_thermal_pressure(int cpu)
> void topology_set_thermal_pressure(const struct cpumask *cpus,
> unsigned long th_pressure);
>
> +void topology_update_thermal_pressure(const struct cpumask *cpus,
> + unsigned long capped_freq);
> +
> struct cpu_topology {
> int thread_id;
> int core_id;
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index c07bfa2d80f2..6e89a8e43aa7 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -273,6 +273,13 @@ void arch_set_thermal_pressure(const struct cpumask *cpus,
> { }
> #endif
>
> +#ifndef arch_update_thermal_pressure
> +static __always_inline
> +void arch_update_thermal_pressure(const struct cpumask *cpus,
> + unsigned long capped_frequency)
> +{ }
> +#endif
> +
> static inline int task_node(const struct task_struct *p)
> {
> return cpu_to_node(task_cpu(p));
>
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