linux-kernel - Re: [PATCH 1/3] powercap, intel_rapl, implement get_max_time

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Date:	Fri, 22 Jan 2016 11:26:17 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Seiichi Ikarashi <s.ikarashi@...fujitsu.com>,
	linux-kernel@...r.kernel.org
CC:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Radivoje Jovanovic <radivoje.jovanovic@...el.com>,
	Mathias Krause <minipli@...glemail.com>,
	Ajay Thomas <ajay.thomas.david.rajamanickam@...el.com>
Subject: Re: [PATCH 1/3] powercap, intel_rapl, implement get_max_time_window



On 01/21/2016 07:27 PM, Seiichi Ikarashi wrote:
> On 2016-01-22 01:15, Prarit Bhargava wrote:
>> The MSR_PKG_POWER_INFO register (Intel ASDM, section 14.9.3
>> "Package RAPL Domain") provides a maximum time window which the
>> system can support.  This window is read-only and is currently
>> not examined when setting the time windows for the package.
>>
>> This patch implements get_max_time_window_us() and checks the window when
>> a user attempts to set power capping for the package.
>>
>> Before the patch it was possible to set the window to, for example, 10000
>> micro seconds:
>>
>> [root@...el-chiefriver-03 rhel7]# echo 10000 >
>> /sys/devices/virtual/powercap/intel-rapl/intel-rapl\:0/constraint_0_time_window_us;
>> egrep ^ /sys/devices/virtual/powercap/intel-rapl/intel-rapl\:0/constraint_0_time_window_us
>>
>> /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_0_time_window_us:1:9765
>>
>> but from 'turbostat -d', the package is limited to 976us:
>>
>> cpu0: MSR_PKG_POWER_INFO: 0x01200168 (45 W TDP, RAPL 36 - 0 W, 0.000977 sec.)
>>
>> (Note, there appears to be a rounding issue in turbostat which needs to
>> also be fixed.  Looking at the values in the register it is clear the
>> value is 1/1024 = 976us.)
>>
>> After the patch we are limited by the maximum time window:
>>
>> [root@...el-chiefriver-03 rhel7]# echo 10000 >
>> /sys/devices/virtual/powercap/intel-rapl/intel-rapl\:0/constraint_0_time_window_us;
>> egrep ^ /sys/devices/virtual/powercap/intel-rapl/intel-rapl\:0/constraint_0_time_window_us
>>
>> -bash: echo: write error: Invalid argument
>> /sys/devices/virtual/powercap/intel-rapl/intel-rapl:0/constraint_0_time_window_us:1:976
>>
>> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
>> Cc: Prarit Bhargava <prarit@...hat.com>
>> Cc: Radivoje Jovanovic <radivoje.jovanovic@...el.com>
>> Cc: Seiichi Ikarashi <s.ikarashi@...fujitsu.com>
>> Cc: Mathias Krause <minipli@...glemail.com>
>> Cc: Ajay Thomas <ajay.thomas.david.rajamanickam@...el.com>
>> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
>> ---
>>  drivers/powercap/intel_rapl.c   |   31 +++++++++++++++++++++++++++++++
>>  drivers/powercap/powercap_sys.c |    6 ++++--
>>  2 files changed, 35 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/powercap/intel_rapl.c b/drivers/powercap/intel_rapl.c
>> index cc97f08..f765b2c 100644
>> --- a/drivers/powercap/intel_rapl.c
>> +++ b/drivers/powercap/intel_rapl.c
>> @@ -493,13 +493,42 @@ static int get_current_power_limit(struct powercap_zone *power_zone, int id,
>>  	return ret;
>>  }
>>  
>> +static int get_max_time_window(struct powercap_zone *power_zone, int id,
>> +			       u64 *data)
> 
> The 2nd arg "id" is not necessary.

It is required by the powercap_sys code.  If I remove this then I have to create
separate sysfs store and show files and I think it isn't worth it to do so.

P.

> 
> --
> Seiichi
>