RAPL power limits

[SPann1]

Is there a way to disable power limits enforced through RAPL registers? I tried using the power governor (https://software.intel.com/en-us/articles/intel-power-governor Intel® Power Governor | Intel® Developer Zone) to disable the power limit settings but it doesn't seem to work.

I am running few workloads that stresses CPU and iGPU on the processor and the total power consumed could exceed the power limit of 15W. The TDP for the processor (i3-5010U) is 15W and the default setting for the RAPL power limit is set to 15W at a time window of 20 seconds. While running the workloads, the limit is enforced and I could notice the package power is reduced to stay within 15W limit. I should note that RAPL lock bit is not set. I tried the following:

1) I tried bumping this limit to 25W using power governor tool but I could observe the same throttling effect after 20 seconds and the power of the package is brought down to 15W.

2) I tried disabling the power limit altogether using the governor tool but that doesn't seem to work - the power limit stays enabled.

I would like to understand if there are other power limit setting supported in the processors or if power limit setting is enforced through BIOS. Any pointers would be very helpful.

[Cesar_B_Intel]

Hello Sankar

Please refer to https://software.intel.com/en-us/articles/intel-power-governor Intel® Power Governor | Intel® Developer Zone

Regards,

Caesar B

[SPann1]

Hi -

Thanks for the response. I did try the power governor tool with my original experiments but disabling the power limit didn't work.

Regards

Sankar

[Cesar_B_Intel]

HelloSankar,

Could you please let us know how did you try to disable the power limit, what is the operating System you currently have installed on your computer?

Additionally, you could try making sure after setting the Power limit you use "-i" option in order to make sure your changes took effect.

You can get more information here https://software.intel.com/en-us/articles/intel-power-gadget-20 Intel® Power Gadget | Intel® Developer Zone and/or here https://software.intel.com/en-us/forums/software-tuning-performance-optimization-platform-monitoring/topic/348993 set power limit to DRAM with RAPL

Regards,

Caesar B

[SPann1]

I perform these experiments on a Lenovo laptop with Intel i3-5010U and the machine has got ubuntu linux installed on it. I used the power governor tool to modify the power limit settings for the processor. By default, 15W power limit is enforced on the chip. I tried the following:

1) I tried disabling the power limit altogether using the governor tool. But when I read the power limit settings again, the power limit stays enabled.

2) I tried increasing this limit to 25W using power governor tool. Re-reading the power limit setting showed tat 25W was set as the limit. But when I ran some workloads, I could observe the processor power being throttled to 15 W after 20 seconds.