Collectd plugin "intel_cpu_energy"

This collectd plugin measures and reports the power usage of 2nd Generation (or later) Intel® Core™ processors.

It will report up to four values for each physical processor: the accumulated energy usage (in Joules) for the "package", "core", "uncore", and "dram" domains, as reported by the CPU. Not all domains are supported by all CPU models, so some of them might be missing on your system.

The code for these measurements is based on Intel's Power Gadget 2.5 for Linux.

Requirements

To read the CPU's internal energy measurements, the plugin requires write access to the CPU's model-specific registers (MSRs). For this, the msr kernel module has to be loaded. In addition, write access to /dev/cpu/*/msr, along with the SYS_RAWIO capability, is required, but since collectd runs its plugins with root privileges anyway, those permissions should be available by default.

To build the module, you will need to have the collectd-dev package installed (the package name might differ on non-Debian-based distributions).

The module has been successfully tested with version 5.4.0-3ubuntu2 of collectd-dev (on Ubuntu 14.04), but collectd's plugin API can be highly unstable, even between minor versions, so it might not work out of the box with other versions.

Building and installing

Collectd's plugin API was moved to a different directory in commit 216c624 and changed to use a different time representation in commit cce1369. These changes will be included in Collectd versions 5.5.0 and higher.

Collectd version >= 5.5.0

For those new version, simply run the following:

make clean all
sudo make install
service collectd restart

Collectd version < 5.5.0

For all older Collectd versions (within reason), pass a preprocessor definition to the C compiler to substitute the relevant portions of the code:

CFLAGS="-DCOLLECTD_VERSION_LT_5_5" make clean all
sudo make install
service collectd restart

Beware that this will override collectd's TypesDB option (in a separate file, so it's easily reversible), so you might want to install the plugin manually if you are already using a custom data-set definition file (e.g. my_types.db). Take a look at the install target in the Makefile for hints on how to do that.

Usage

The plugin will produce data sets named according to the pattern

${host}/intel_cpu_energy-cpu{0..}/energy-{package,core,uncore,dram}

Each data point will contain the accumulated energy consumption in Joules (= Watt seconds) since the last (re-)start of collectd.

The value is internally processed as a double-precision floating point number, so you shouldn't encounter any problems with overflows. However, the measurement value reported by the CPU can (and will) overflow eventually. The plugin will detect and compensate for this, but it has to make sure it won't "miss" an overflow (= more than one overflow occurring between successive readouts of the CPU registers. To ensure this, the plugin will enforce a 60 second polling interval if the global interval is greater than that. Shorter polling intervals than 60 seconds will be accepted and used unchanged.