Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 31 Oct 2019 17:38:25 +0100 | Subject | Re: [Patch v4 5/6] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping |
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On Thu, 31 Oct 2019 at 17:29, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > On 22.10.19 22:34, Thara Gopinath wrote: > > Thermal governors can request for a cpu's maximum supported frequency > > to be capped in case of an overheat event. This in turn means that the > > maximum capacity available for tasks to run on the particular cpu is > > reduced. Delta between the original maximum capacity and capped > > maximum capacity is known as thermal pressure. Enable cpufreq cooling > > device to update the thermal pressure in event of a capped > > maximum frequency. > > > > Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org> > > --- > > drivers/thermal/cpu_cooling.c | 31 +++++++++++++++++++++++++++++-- > > 1 file changed, 29 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c > > index 391f397..2e6a979 100644 > > --- a/drivers/thermal/cpu_cooling.c > > +++ b/drivers/thermal/cpu_cooling.c > > @@ -218,6 +218,23 @@ static u32 cpu_power_to_freq(struct cpufreq_cooling_device *cpufreq_cdev, > > } > > > > /** > > + * update_sched_max_capacity - update scheduler about change in cpu > > + * max frequency. > > + * @policy - cpufreq policy whose max frequency is capped. > > + */ > > +static void update_sched_max_capacity(struct cpumask *cpus, > > + unsigned int cur_max_freq, > > + unsigned int max_freq) > > +{ > > + int cpu; > > + unsigned long capacity = (cur_max_freq << SCHED_CAPACITY_SHIFT) / > > + max_freq; > > + > > + for_each_cpu(cpu, cpus) > > + update_thermal_pressure(cpu, capacity); > > +} > > + > > +/** > > * get_load() - get load for a cpu since last updated > > * @cpufreq_cdev: &struct cpufreq_cooling_device for this cpu > > * @cpu: cpu number > > @@ -320,6 +337,7 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev, > > unsigned long state) > > { > > struct cpufreq_cooling_device *cpufreq_cdev = cdev->devdata; > > + int ret; > > > > /* Request state should be less than max_level */ > > if (WARN_ON(state > cpufreq_cdev->max_level)) > > @@ -331,8 +349,17 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev, > > > > cpufreq_cdev->cpufreq_state = state; > > > > - return dev_pm_qos_update_request(&cpufreq_cdev->qos_req, > > - cpufreq_cdev->freq_table[state].frequency); > > + ret = dev_pm_qos_update_request > > + (&cpufreq_cdev->qos_req, > > + cpufreq_cdev->freq_table[state].frequency); > > + > > + if (ret > 0) > > + update_sched_max_capacity > > + (cpufreq_cdev->policy->cpus, > > + cpufreq_cdev->freq_table[state].frequency, > > + cpufreq_cdev->policy->cpuinfo.max_freq); > > + > > + return ret; > > } > > > > /** > > > > Why not getting rid of update_sched_max_capacity() entirely and call > update_thermal_pressure() in cpu_cooling.c directly? Saves one level in > the call chain and would mean less code for this feature.
But you add complexity in update_thermal_pressure which now has to deal with a cpumask and to compute some frequency ratio IMHO, it's cleaner to keep update_thermal_pressure simple as it is now
> > Just compile tested on arm64: > > diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c > index 3211b4d3a899..bf36995013b0 100644 > --- a/drivers/thermal/cpu_cooling.c > +++ b/drivers/thermal/cpu_cooling.c > @@ -217,23 +217,6 @@ static u32 cpu_power_to_freq(struct > cpufreq_cooling_device *cpufreq_cdev, > return freq_table[i - 1].frequency; > } > > -/** > - * update_sched_max_capacity - update scheduler about change in cpu > - * max frequency. > - * @policy - cpufreq policy whose max frequency is capped. > - */ > -static void update_sched_max_capacity(struct cpumask *cpus, > - unsigned int cur_max_freq, > - unsigned int max_freq) > -{ > - int cpu; > - unsigned long capacity = (cur_max_freq << SCHED_CAPACITY_SHIFT) / > - max_freq; > - > - for_each_cpu(cpu, cpus) > - update_thermal_pressure(cpu, capacity); > -} > - > /** > * get_load() - get load for a cpu since last updated > * @cpufreq_cdev: &struct cpufreq_cooling_device for this cpu > @@ -353,7 +336,7 @@ static int cpufreq_set_cur_state(struct > thermal_cooling_device *cdev, > cpufreq_cdev->freq_table[state].frequency); > > if (ret > 0) > - update_sched_max_capacity > + update_thermal_pressure > (cpufreq_cdev->policy->cpus, > cpufreq_cdev->freq_table[state].frequency, > cpufreq_cdev->policy->cpuinfo.max_freq); > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 55dfe9634f67..5707813c7621 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1985,9 +1985,9 @@ static inline void rseq_syscall(struct pt_regs *regs) > #endif > > #ifdef CONFIG_SMP > -void update_thermal_pressure(int cpu, u64 capacity); > +void update_thermal_pressure(struct cpumask *cpus, unsigned int cur, > unsigned int max); > #else > -static inline void update_thermal_pressure(int cpu, u64 capacity) > +static inline void update_thermal_pressure(struct cpumask *cpus, > unsigned int cur, unsigned int max); > { > } > #endif > diff --git a/kernel/sched/thermal.c b/kernel/sched/thermal.c > index 0da31e12a5ff..691bdd79597a 100644 > --- a/kernel/sched/thermal.c > +++ b/kernel/sched/thermal.c > @@ -43,17 +43,16 @@ static DEFINE_PER_CPU(unsigned long, delta_capacity); > * 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) > +void update_thermal_pressure(struct cpumask *cpus, unsigned int cur, > unsigned int max) > { > - unsigned long __capacity, delta; > + int cpu; > > - /* 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); > + for_each_cpu(cpu, cpus) { > + unsigned long scale_cap = arch_scale_cpu_capacity(cpu); > + unsigned long cur_cap = cur * scale_cap / max; > > - per_cpu(delta_capacity, cpu) = delta; > + per_cpu(delta_capacity, cpu) = scale_cap - cur_cap; > + } > }
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