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 10:23:07 +0800
From:	ethan zhao <ethan.zhao@...cle.com>
To:	Kristen Carlson Accardi <kristen@...ux.intel.com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	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
Subject: Re: [PATCH 2/2 V7] intel_pstate: add kernel parameter to force loading
 on Sun X86 servers.

Kristen,

On 2014/12/5 6:38, Kristen Carlson Accardi wrote:
> On Thu, 04 Dec 2014 23:10:58 +0100
> "Rafael J. Wysocki" <rjw@...ysocki.net> 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.
>>
>>> 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?
>>
> That was my suggestion as well (i.e. a parameter to bypass the vendor
> checks), but Linda didn't like it.  My personal opinion is that unless
> it's generic, I don't really feel like having a force option solely for
> oracle.  I'm not convinced you want this for production machines, and I
> think for debug purposes I don't want a vendor specific param.
   I am OK with a generic parameter.
   Anyway I hope there is a parameter to allow us load intel_pstate on 
Oracle boxes, specific to Oracle or generic.

   Thanks,
   Ethan

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