Messages in this thread | | | From | Amit Kucheria <> | Date | Thu, 13 Feb 2020 17:55:47 +0530 | Subject | Re: [Patch v9 3/8] arm,arm64,drivers:Add infrastructure to store and update instantaneous thermal pressure |
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On Wed, Jan 29, 2020 at 4:06 AM Thara Gopinath <thara.gopinath@linaro.org> wrote: > > 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.
s/capped/decreased to have consistent use throughout the series e.g. in patch 1.
Though personally, I like "capped capacity" in which case s/decreased/capped in patch 1 and elsewhere.
> > topology_get_thermal_pressure can be hooked into the scheduler specified > arch_cpu_thermal_capacity to retrieve instantaneous thermal pressure of a > cpu. > > arch_set_thermal_pressure can be used to update the thermal pressure. > > 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 can be called from a system critical 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> > --- > > v6->v7: > - Changed the input argument in arch_set_thermal_pressure from > capped capacity to delta capacity(thermal pressure) as per > Ionela's review comments. > > arch/arm/include/asm/topology.h | 3 +++ > arch/arm64/include/asm/topology.h | 3 +++
Any particular reason to enable this for arm/arm64 in this patch itself? I'd have enabled them in two separate patches after this one.
> drivers/base/arch_topology.c | 11 +++++++++++ > include/linux/arch_topology.h | 10 ++++++++++ > 4 files changed, 27 insertions(+) > > diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h > index 8a0fae9..3a50a19 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 default thermal pressure retrieve API */ > +#define arch_cpu_thermal_pressure 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..a70896f 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 default thermal pressure retrieve API */ > +#define arch_cpu_thermal_pressure 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 6119e11..68dfa49 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -42,6 +42,17 @@ 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 th_pressure) > +{ > + int cpu;
<snip>
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