linux-kernel - Re: [PATCH 2/2 V7] intel_pstate: add kernel parameter to force loading on Sun X86 servers.

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Date:	Thu, 04 Dec 2014 23:10:58 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Ethan Zhao <ethan.zhao@...cle.com>
Cc:	dirk.j.brandewie@...el.com, linda.knippers@...com,
	viresh.kumar@...aro.org, corbet@....net, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	ethan.kernel@...il.com,
	Kristen Carlson Accardi <kristen@...ux.intel.com>
Subject: Re: [PATCH 2/2 V7] intel_pstate: add kernel parameter to force loading on Sun X86 servers.

On Thursday, December 04, 2014 11:07:31 AM Ethan Zhao wrote:
> To force loading on Oracle Sun X86 servers, provide one kernel command line
> parameter
> 
>   intel_pstate = ora_force

I would suggest to change the name of the option to "oracle_force" or "sun_force"
for clarity.

Anyway, I need an ACK from Kristen if this patch is to be applied.

> For those who be aware of the risk of no power capping capabily working and
> try to get better performance with this driver.
> 
> Signed-off-by: Ethan Zhao <ethan.zhao@...cle.com>
> ---
>  v2: change to hardware vendor specific naming parameter.
>  v4: refine code and doc.
>  v5&v6: fix a typo in doc.
>  v7: change enum PCC to PPC.
> 
>  Documentation/kernel-parameters.txt | 5 +++++
>  drivers/cpufreq/intel_pstate.c      | 6 +++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 479f332..7d0983e 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1446,6 +1446,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>  		       disable
>  		         Do not enable intel_pstate as the default
>  		         scaling driver for the supported processors
> +		       ora_force
> +			 Force loading intel_pstate on Oracle Sun Servers(X86).
> +			 only for those who be aware of the risk of no power capping
> +			 capability working and try to get better performance with this
> +			 driver.

That is not sufficiently clear.  What does "risk of no power capping capability
working" mean, in particular?

>  
>  	intremap=	[X86-64, Intel-IOMMU]
>  			on	enable Interrupt Remapping (default)
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 1bb62ca..2654e13 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -866,6 +866,7 @@ static struct cpufreq_driver intel_pstate_driver = {
>  };
>  
>  static int __initdata no_load;
> +static unsigned int  ora_force;
>  
>  static int intel_pstate_msrs_not_valid(void)
>  {
> @@ -1003,7 +1004,8 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
>  			case PSS:
>  				return intel_pstate_no_acpi_pss();
>  			case PPC:
> -				return intel_pstate_has_acpi_ppc();
> +				return intel_pstate_has_acpi_ppc() &&
> +					(!ora_force);
>  			}
>  	}
>  
> @@ -1078,6 +1080,8 @@ static int __init intel_pstate_setup(char *str)
>  
>  	if (!strcmp(str, "disable"))
>  		no_load = 1;
> +	if (!strcmp(str, "ora_force"))
> +		ora_force = 1;
>  	return 0;
>  }
>  early_param("intel_pstate", intel_pstate_setup);

And can anyone please remind me what was wrong with a "force" option that would
work for everyone, not just Oracle/Sun?

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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