linux-kernel - Re: [PATCH RESEND v4 3/4] cpufreq: powernv: Add a trace print for the throttle event

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Date:	Tue, 12 Jan 2016 16:25:38 +0530
From:	Gautham R Shenoy <ego@...ux.vnet.ibm.com>
To:	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	rjw@...ysocki.net, viresh.kumar@...aro.org,
	linux-pm@...r.kernel.org, pc@...ibm.com, anton@...ba.org,
	ego@...ux.vnet.ibm.com, shreyas@...ux.vnet.ibm.com
Subject: Re: [PATCH RESEND v4 3/4] cpufreq: powernv: Add a trace print for
 the throttle event

Hi Shilpa,

Just saw this resend!

On Tue, Jan 12, 2016 at 04:24:26AM -0600, Shilpasri G Bhat wrote:
> Record the throttle event with a trace print replacing the printk,
> except for events like throttling below nominal and occ reset
> event which print a warning message.
> 
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
> ---

[..snip..]

> 
> -static void powernv_cpufreq_throttle_check(void *data)
> +static void powernv_cpufreq_check_pmax(void)
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This function only contains code moved from
powernv_cpufreq_throttle_check with pr_crit/pr_warns replaced by
trace_powernv_throttle. Furthermore, it is not called from any other
place. Given that the original function was ~60 lines do we really
need to split it into two separate functions ? If yes, could it be an
inline function ?

>  {
>  	unsigned int cpu = smp_processor_id();
>  	unsigned int chip_id = pir_to_chip_id(hard_smp_processor_id());
> -	unsigned long pmsr;
>  	int pmsr_pmax, i;
> 
> -	pmsr = get_pmspr(SPRN_PMSR);
> +	pmsr_pmax = (s8)PMSR_MAX(get_pmspr(SPRN_PMSR));
> 
>  	for (i = 0; i < nr_chips; i++)
>  		if (chips[i].id == chip_id)
>  			break;
> 
> -	/* Check for Pmax Capping */
> -	pmsr_pmax = (s8)PMSR_MAX(pmsr);
>  	if (pmsr_pmax != powernv_pstate_info.max) {
>  		if (chips[i].throttled)
> -			goto next;
> +			return;
> +
>  		chips[i].throttled = true;
>  		if (pmsr_pmax < powernv_pstate_info.nominal)
> -			pr_crit("CPU %d on Chip %u has Pmax reduced below nominal frequency (%d < %d)\n",
> -				cpu, chips[i].id, pmsr_pmax,
> -				powernv_pstate_info.nominal);
> -		else
> -			pr_info("CPU %d on Chip %u has Pmax reduced below turbo frequency (%d < %d)\n",
> -				cpu, chips[i].id, pmsr_pmax,
> -				powernv_pstate_info.max);
> +			pr_warn_once("CPU %d on Chip %u has Pmax reduced below nominal frequency (%d < %d)\n",
> +				     cpu, chips[i].id, pmsr_pmax,
> +				     powernv_pstate_info.nominal);
> +
> +		trace_powernv_throttle(chips[i].id,
> +				       throttle_reason[chips[i].throt_reason],
> +				       pmsr_pmax);
>  	} else if (chips[i].throttled) {
>  		chips[i].throttled = false;
> -		pr_info("CPU %d on Chip %u has Pmax restored to %d\n", cpu,
> -			chips[i].id, pmsr_pmax);
> +		trace_powernv_throttle(chips[i].id,
> +				       throttle_reason[chips[i].throt_reason],
> +				       pmsr_pmax);
>  }
> +}
> +
> +static void powernv_cpufreq_throttle_check(void *data)
> +{
> +	unsigned long pmsr;
> +
> +	pmsr = get_pmspr(SPRN_PMSR);
> +
> +	/* Check for Pmax Capping */
> +	powernv_cpufreq_check_pmax();
  
If you want to retain this function, you could pass pmsr as an
argument instead of computing it afresh in
powernv_cpufreq_check_pmax()

>  	/* Check if Psafe_mode_active is set in PMSR. */
> -next:
>  	if (pmsr & PMSR_PSAFE_ENABLE) {
>  		throttled = true;
>  		pr_info("Pstate set to safe frequency\n");

--
Thanks and Regards
gautham.