On 13 June 2012 10:50, Jean Pihet <jean.pi...@newoldbits.com> wrote:
> Hi Vincent,
>
> On Tue, Jun 12, 2012 at 2:02 PM, Vincent Guittot
> <vincent.guit...@linaro.org> wrote:
>> Add infrastructure to be able to modify the cpu_power of each core
>>
>> Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
>> ---
>> arch/arm/include/asm/topology.h | 2 ++
>> arch/arm/kernel/topology.c | 36 +++++++++++++++++++++++++++++++++++-
>> 2 files changed, 37 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/include/asm/topology.h
>> b/arch/arm/include/asm/topology.h
>> index 58b8b84..78e4c85 100644
>> --- a/arch/arm/include/asm/topology.h
>> +++ b/arch/arm/include/asm/topology.h
>> @@ -27,11 +27,13 @@ void init_cpu_topology(void);
>> void store_cpu_topology(unsigned int cpuid);
>> const struct cpumask *cpu_coregroup_mask(int cpu);
>>
>> +void set_power_scale(unsigned int cpu, unsigned long power);
>> #else
>>
>> static inline void init_cpu_topology(void) { }
>> static inline void store_cpu_topology(unsigned int cpuid) { }
>>
>> +static inline void set_power_scale(unsigned int cpu, unsigned long power) {
>> }
>> #endif
>>
>> #include <asm-generic/topology.h>
>> diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
>> index 8200dea..00301a7 100644
>> --- a/arch/arm/kernel/topology.c
>> +++ b/arch/arm/kernel/topology.c
>> @@ -22,6 +22,35 @@
>> #include <asm/cputype.h>
>> #include <asm/topology.h>
>>
>> +/*
>> + * cpu power scale management
>> + */
>> +
>> +/*
>> + * cpu power table
>> + * This per cpu data structure describes the relative capacity of each core.
>> + * On a heteregenous system, cores don't have the same computation capacity
>> + * and we reflect that difference in the cpu_power field so the scheduler
>> can
>> + * take this difference into account for load balance. A per cpu structure
>> is
>> + * preferred because each cpu is mainly using its own cpu_power even it's
>> not
>> + * always true because of nohz_idle_balance
> The end of the comment is unclear IMO; Can you give more details on
> the relation between cpu_power and nohz_idle_balance?
When several cores are idle, one core runs the load balance for all
idle cores. The update of the cpu_power can be done during rebalance
and arch_scale_freq_power can be called by CPU0 for updating the
cpu_power of CPU1.
I was probably not clear enough in my first explanation. I will reword
the comment
Regards,
Vincent
>
> Regards,
> Jean
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