linux-kernel - Re: [PATCH 2/7] cpufreq: intel_pstate: Avoid duplicate call of intel_pstate_get_scaled

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Date:	Tue, 10 Jun 2014 09:05:53 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	Stratos Karafotis <stratosk@...aphore.gr>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
CC:	dirk.brandewie@...il.com,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] cpufreq: intel_pstate: Avoid duplicate call of intel_pstate_get_scaled_busy

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.

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()


> Also, rename the function to intel_pstate_calc_scaled_busy.
>
> Signed-off-by: Stratos Karafotis <stratosk@...aphore.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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