Power and Energy Measurements of FPGAs

Owned by Tobias Kenter
Last updated: Dec 02, 2024 by Heinrich Riebler
3 min read

Xilinx Alveo U280, Xilinx Alveo U55C, Xilinx Versal VCK5000

The Xilinx xrt driver provides power measurements via a hwmon interface. It can be queried by simply reading from a corresponding file, which returns the current power consumption in µW:

# Location: /sys/bus/pci/devices/$BDF/hwmon/hwmon*/power1_input, # where BDF is one of 0000:a1:00.1, 0000:81:00.1 or 0000:01:00.1 [tester@n2fpga01 ~]$ cat /sys/bus/pci/devices/0000\:01\:00.1/hwmon/hwmon*/power1_input 58360411

For a more convenient interface, we provide a dedicated tool named xilinx_power which is available on all Xilinx FPGA and Xilinx HACC nodes:

# # Xilinx FPGA Nodes # [tester@n2fpga01 ~]$ xilinx_power 0000:a1:00.1: 41.35W 0000:81:00.1: 39.22W 0000:01:00.1: 58.28W [tester@n2fpga01 ~]$ xilinx_power -c2 0000:01:00.1: 58.22W [tester@n2fpga01 ~]$ xilinx_power -c 0000:01:00.1 0000:01:00.1: 57.95W # # Xilinx HACC Nodes # [tester@n2hacc03 ~]$ xbutil examine # [...] Devices present BDF : Shell Logic UUID Device ID Device Ready* --------------------------------------------------------------------------------------------------------------------------- [0000:81:00.1] : xilinx_u55c_gen3x16_xdma_base_3 97088961-FEAE-DA91-52A2-1D9DFD63CCEF user(inst=134) Yes [0000:a1:00.1] : xilinx_vck5000_gen4x8_qdma_base_2 05DCA096-76CB-730B-8D19-EC1192FBAE3F user(inst=135) Yes [0000:c1:00.1] : xilinx_u55c_gen3x16_xdma_base_3 97088961-FEAE-DA91-52A2-1D9DFD63CCEF user(inst=133) Yes [0000:e1:00.1] : xilinx_vck5000_gen4x8_qdma_base_2 05DCA096-76CB-730B-8D19-EC1192FBAE3F user(inst=132) Yes [tester@n2hacc03 ~]$ xilinx_power 0000:e1:00.1: 34.00W 0000:c1:00.1: 15.04W 0000:a1:00.1: 41.00W 0000:81:00.1: 14.50W

Run with --help to get a list of command line arguments. -c allows specifying a specific card by either index or BDF.

You can also use the XRT API to query electrical information, including the current power consumption, as JSON. The following example uses Boost to parse that JSON data:

#include <boost/property_tree/json_parser.hpp> #include <xrt/xrt_device.h> [...] // Assuming `device` being an instance of or a reference to a valid xrt::device auto json = std::stringstream{}; json << device.get_info<xrt::info::device::electrical>(); // parse JSON into a property tree auto props = boost::property_tree::ptree{}; boost::property_tree::read_json(json, props); auto watts = props.get<float>("power_consumption_watts", 0.0f); std::cout << watts << "W\n";

Lastly, you can also use xbutil to query those electrical information. Usage example and sample output for xrt 2.12, querying the first card. Power consumption is shown in line 17:

 

General notes:

  • We recommend to run kernels for at least ~1s and automatically perform repeated invocations to the command line tool concurrently in order to get reasonably accurate results. Further effects of increased power consumption due to thermal effects can be observed after multiple minutes of load on the cards, but are comparably minor.

  • Power consumption values are only updated once per second. Querying with a higher frequency therefore does not provide any additional data.

Bittware 520N

The Bittware driver allows to measure power using a standalone command line tool that queries the board power via the i2c bus. It's available on all FPGA nodes with Bittware 520N cards (irrespective of the constraint).

  • We recommend to run kernels for at least ~1s and automatically perform repeated invocations to the command line tool concurrently in order to get reasonably accurate results. Further effects of increased power consumption due to thermal effects can be observed after multiple minutes of load on the cards, but are comparably minor.

Usage example and sample output:

Run with --help to get a list of command line arguments. For example, with -c the 520N card of interest can be selected.