linux-kernel - Re: [PATCH] intel_pstate: Update cpu

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Date:	Tue, 19 Jul 2016 15:39:18 -0700
From:	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux PM list <linux-pm@...r.kernel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] intel_pstate: Update cpu_frequency tracepoint every time

On Tue, 2016-07-19 at 15:10 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Currently, intel_pstate only updates the cpu_frequency tracepoint
> if the new P-state to set is different from the current one, but
> that causes powertop to report 100% idle on an 100% loaded system
> sometimes.
> 
> Prevent that from happening by updating the cpu_frequency tracepoint
> every time intel_pstate_update_pstate() is called.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Acked-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>-

> --
>  drivers/cpufreq/intel_pstate.c |   12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> Index: linux-pm/drivers/cpufreq/intel_pstate.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> +++ linux-pm/drivers/cpufreq/intel_pstate.c
> @@ -1134,17 +1134,12 @@ static void intel_pstate_get_min_max(str
>  	*min = clamp_t(int, min_perf, cpu->pstate.min_pstate,
> max_perf);
>  }
>  
> -static inline void intel_pstate_record_pstate(struct cpudata *cpu,
> int pstate)
> -{
> -	trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu);
> -	cpu->pstate.current_pstate = pstate;
> -}
> -
>  static void intel_pstate_set_min_pstate(struct cpudata *cpu)
>  {
>  	int pstate = cpu->pstate.min_pstate;
>  
> -	intel_pstate_record_pstate(cpu, pstate);
> +	trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu);
> +	cpu->pstate.current_pstate = pstate;
>  	/*
>  	 * Generally, there is no guarantee that this code will
> always run on
>  	 * the CPU being updated, so force the register update to
> run on the
> @@ -1304,10 +1299,11 @@ static inline void intel_pstate_update_p
>  
>  	intel_pstate_get_min_max(cpu, &min_perf, &max_perf);
>  	pstate = clamp_t(int, pstate, min_perf, max_perf);
> +	trace_cpu_frequency(pstate * cpu->pstate.scaling, cpu->cpu);
>  	if (pstate == cpu->pstate.current_pstate)
>  		return;
>  
> -	intel_pstate_record_pstate(cpu, pstate);
> +	cpu->pstate.current_pstate = pstate;
>  	wrmsrl(MSR_IA32_PERF_CTL, pstate_funcs.get_val(cpu,
> pstate));
>  }
>  
> 
> --
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