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    SubjectRe: [PATCH v4 1/5] arch_topology: Introduce thermal pressure update function
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    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@arm.com>

    Reviewed-by: Thara Gopinath <thara.gopinath@linaro.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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