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SubjectRe: [PATCH 2/7] cpufreq: intel_pstate: Avoid duplicate call of intel_pstate_get_scaled_busy
On 10/06/2014 07:05 μμ, Dirk Brandewie wrote:
> On 06/09/2014 02:00 PM, Stratos Karafotis wrote:
>> Store busy_scaled value to avoid to duplicate call of
>> intel_pstate_get_scaled_busy on every sampling interval.
>>
>
> The second call *only* happens if the tracepoint is being used otherwise
> the whole function call to trace_pstate_sample() is a noop.

Yes, I'm sorry, I forgot to add this in my changelog. I have written this
in cover letter.
I made this change mostly to support patch 3/7.

> This makes the code less readable IMHO the reader is left wondering
> how cpu->sample.busy_scaled was set in intel_pstate_adjust_busy_pstate()
>

I agree that the the original code is more readable. If we don't care
about the small overhead when tracing is on and forget patch 3/7,
of course the original code is by far better.


>> Also, rename the function to intel_pstate_calc_scaled_busy.
>>
>> Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
>> ---
>> drivers/cpufreq/intel_pstate.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
>> index 4e7f492..31e2ae5 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -55,6 +55,7 @@ static inline int32_t div_fp(int32_t x, int32_t y)
>>
>> struct sample {
>> int32_t core_pct_busy;
>> + int32_t busy_scaled;
>> u64 aperf;
>> u64 mperf;
>> int freq;
>> @@ -604,7 +605,7 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
>> mod_timer_pinned(&cpu->timer, jiffies + delay);
>> }
>>
>> -static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu)
>> +static inline void intel_pstate_calc_scaled_busy(struct cpudata *cpu)
>> {
>> int32_t core_busy, max_pstate, current_pstate, sample_ratio;
>> u32 duration_us;
>> @@ -624,20 +625,19 @@ static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu)
>> core_busy = mul_fp(core_busy, sample_ratio);
>> }
>>
>> - return core_busy;
>> + cpu->sample.busy_scaled = core_busy;
>> }
>>
>> static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
>> {
>> - int32_t busy_scaled;
>> struct _pid *pid;
>> signed int ctl = 0;
>> int steps;
>>
>> pid = &cpu->pid;
>> - busy_scaled = intel_pstate_get_scaled_busy(cpu);
>> + intel_pstate_calc_scaled_busy(cpu);
>>
>> - ctl = pid_calc(pid, busy_scaled);
>> + ctl = pid_calc(pid, cpu->sample.busy_scaled);
>>
>> steps = abs(ctl);
>>
>> @@ -659,7 +659,7 @@ static void intel_pstate_timer_func(unsigned long __data)
>> intel_pstate_adjust_busy_pstate(cpu);
>>
>> trace_pstate_sample(fp_toint(sample->core_pct_busy),
>> - fp_toint(intel_pstate_get_scaled_busy(cpu)),
>> + fp_toint(sample->busy_scaled),
>> cpu->pstate.current_pstate,
>> sample->mperf,
>> sample->aperf,
>>
>
>

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