Messages in this thread |  | | Subject | Re: [Patch v6 3/7] Add infrastructure to store and update instantaneous thermal pressure | From | Dietmar Eggemann <> | Date | Tue, 17 Dec 2019 13:54:28 +0100 |
| |
On 12/12/2019 05:11, Thara Gopinath wrote:
Shouldn't the subject contain something like 'arm,arm64,drivers:' ?
> Add architecture specific APIs to update and track thermal pressure on a > per cpu basis. A per cpu variable thermal_pressure 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. > capacity and capped capacity due to a thermal event. > > topology_get_thermal_pressure can be hooked into the scheduler specified > arch_scale_thermal_capacity to retrieve instantaneius thermal pressure of
s/instantaneius/instantaneous
> a cpu. > > arch_set_thermal_presure can be used to update the thermal pressure by
s/presure/pressure
> providing a capped maximum capacity. > > Considering topology_get_thermal_pressure reads thermal_pressure and > arch_set_thermal_pressure writes into thermal_pressure, one can argue for > some sort of locking mechanism to avoid a stale value. But considering > topology_get_thermal_pressure_average can be called from a system critical
s/topology_get_thermal_pressure_average/topology_get_thermal_pressure ?
> path like scheduler tick function, a locking mechanism is not ideal. This > means that it is possible the thermal_pressure value used to calculate > average thermal pressure for a cpu can be stale for upto 1 tick period. > > Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org> > --- > > v3->v4: > - Dropped per cpu max_capacity_info struct and instead added a per > delta_capacity variable to store the delta between maximum > capacity and capped capacity. The delta is now calculated when > thermal pressure is updated and not every tick. > - Dropped populate_max_capacity_info api as only per cpu delta > capacity is stored. > - Renamed update_periodic_maxcap to > trigger_thermal_pressure_average and update_maxcap_capacity to > update_thermal_pressure. > v4->v5: > - As per Peter's review comments folded thermal.c into fair.c. > - As per Ionela's review comments revamped update_thermal_pressure > to take maximum available capacity as input instead of maximum > capped frequency ration. > v5->v6: > - As per review comments moved all the infrastructure to track > and retrieve instantaneous thermal pressure out of scheduler > to topology files. > > arch/arm/include/asm/topology.h | 3 +++ > arch/arm64/include/asm/topology.h | 3 +++ > drivers/base/arch_topology.c | 13 +++++++++++++ > include/linux/arch_topology.h | 11 +++++++++++ > 4 files changed, 30 insertions(+) > > diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h > index 8a0fae9..90b18c3 100644 > --- a/arch/arm/include/asm/topology.h > +++ b/arch/arm/include/asm/topology.h > @@ -16,6 +16,9 @@ > /* Enable topology flag updates */ > #define arch_update_cpu_topology topology_update_cpu_topology > > +/* Replace task scheduler's defalut thermal pressure retrieve API */ > +#define arch_scale_thermal_capacity topology_get_thermal_pressure > + > #else > > static inline void init_cpu_topology(void) { } > diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h > index a4d945d..ccb277b 100644 > --- a/arch/arm64/include/asm/topology.h > +++ b/arch/arm64/include/asm/topology.h > @@ -25,6 +25,9 @@ int pcibus_to_node(struct pci_bus *bus); > /* Enable topology flag updates */ > #define arch_update_cpu_topology topology_update_cpu_topology > > +/* Replace task scheduler's defalut thermal pressure retrieve API */ > +#define arch_scale_thermal_capacity topology_get_thermal_pressure > + > #include <asm-generic/topology.h> > > #endif /* _ASM_ARM_TOPOLOGY_H */ > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 1eb81f11..3a91379 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -42,6 +42,19 @@ void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity) > per_cpu(cpu_scale, cpu) = capacity; > } > > +DEFINE_PER_CPU(unsigned long, thermal_pressure); > + > +void arch_set_thermal_pressure(struct cpumask *cpus, > + unsigned long capped_capacity) > +{ > + int cpu; > + unsigned long delta = arch_scale_cpu_capacity(cpumask_first(cpus)) - > + capped_capacity;
unsigned long delta; int cpu;
delta = arch_scale_cpu_capacity(cpumask_first(cpus)) - capped_capacity;
Easier to read plus order local variable declarations from longest to shortest line.
https://lore.kernel.org/r/20181107171149.165693799@linutronix.de
> + > + for_each_cpu(cpu, cpus) > + WRITE_ONCE(per_cpu(thermal_pressure, cpu), delta); > +} > + > static ssize_t cpu_capacity_show(struct device *dev, > struct device_attribute *attr, > char *buf) > diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h > index 3015ecb..7a04364 100644 > --- a/include/linux/arch_topology.h > +++ b/include/linux/arch_topology.h > @@ -33,6 +33,17 @@ unsigned long topology_get_freq_scale(int cpu) > return per_cpu(freq_scale, cpu); > } > > +DECLARE_PER_CPU(unsigned long, thermal_pressure); > + > +static inline > +unsigned long topology_get_thermal_pressure(int cpu)
Save one line:
static inline unsigned long topology_get_thermal_pressure(int cpu)
> +{ > + return per_cpu(thermal_pressure, cpu); > +} > + > +void arch_set_thermal_pressure(struct cpumask *cpus, > + unsigned long capped_capacity); > + > struct cpu_topology { > int thread_id; > int core_id; >
|  |