README.md

RAPLCap - msr

This implementation of the raplcap interface reads directly from Model-Specific Registers on Linux platforms.

It supports processors described beginning with the Sandy Bridge microarchitecture through the latest documented in the Intel Software Developer's Manual, Volume 4 as of October 2024.

To see if your processor is compatible, first check that the CPU is a GenuineIntel:

cat /proc/cpuinfo | grep vendor | uniq | awk '{print $3}'

Then check if the model is listed in raplcap-cpuid.h:

printf "0x%X\n" $(cat /proc/cpuinfo | grep model | grep -v name | uniq | cut -d: -f2)

Prerequisites

The implementation first checks for the msr-safe kernel module, otherwise it falls back on the msr kernel module.

To load the msr kernel module:

sudo modprobe msr

Configuring msr-safe

If using the msr-safe module, ensure that your user has read/write privileges to the appropriate msr_safe file(s) located at /dev/cpu/*/msr_safe and that the following registers have read/write enabled:

• MSR_RAPL_POWER_UNIT
• MSR_PKG_POWER_LIMIT
• MSR_PKG_ENERGY_STATUS
• MSR_PP0_POWER_LIMIT
• MSR_PP0_ENERGY_STATUS
• MSR_PP1_POWER_LIMIT
• MSR_PP1_ENERGY_STATUS
• MSR_DRAM_POWER_LIMIT
• MSR_DRAM_ENERGY_STATUS
• MSR_PLATFORM_POWER_LIMIT
• MSR_PLATFORM_ENERGY_COUNTER
• MSR_VR_CURRENT_CONFIG

You can add these registers to the allowlist by running from this directory:

sudo sh -c 'cat etc/msr_safe_allowlist >> /dev/cpu/msr_allowlist'