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

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Date:	Fri, 05 Dec 2014 10:14:00 +0800
From:	ethan zhao <ethan.zhao@...cle.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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.

Rafael,

On 2014/12/5 6:10, Rafael J. Wysocki wrote:
> 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.
  "oracle_force" or "sun_force" doesn't sound bad to me, except it looks 
like a suggestion from
  "Oracle" or "Sun". does it imply user to use it by default on Oracle 
boxes ?
>
>> 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?
  That means we couldn't limit the power consumption of the host to what 
we want, in some cases, it
  possibly burn the fuse if the redundancy of power supply is not 
enough, that would stop service.

  Did I make it clear ?


  Thanks,
  Ethan
>
>>   
>>   	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?
>

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