svtrace

svtrace is a tool used to evaluate the performance of IEC61850 Sample Values kernel processing on a machine.

Table of Contents

• Introduction
• Features
• Installation
• Configuration
• Usage

Introduction

The svtrace project is a tool focused on measuring the latency of IEC61850 Sample Values. Powered by bpftrace, it achieves to computes the transit latency of IEC61850 Sample Values from their arrival on the interface IRQ process, to their processing by the virtualization agent (currently vhost driver, hosted by qemu).

svtrace is designed to work either on a physical machine (hypervisor) or Virtual Machine. Currently, only qemu using vhost-net drivers virtualization on the host side and virtio drivers on the VM side is supported.

svtrace uses the power of bpftrace and Linux kprobes to achieve the measurement of Sample Values latency. Currently, on both physical and virtual machines, the following kprobes are used:

• tpacket_rcv on SV arrival, in SV interface IRQ process
• consume_skb on SV proceed, in vhost driver QEMU thread

The following kprobes have been selected as they represent well the lifetime of an SV on a specific machine. But note that it represents only a small part of the lifetime; For more scalable tests we recommend using the seapath performance tool project.

Features

• Python-based implementation for ease of use and flexibility
• Utilizes bpftrace for high-precision kernel latency measurements
• Designed specifically for IEC61850 SV packets
• Live feature for direct in terminal latency measurements
• record feature for recording latencies measurements in a file, which can be used later for post-processing

Installation

bpftrace is required on version > v0.20.0. For some Linux distros as Ubuntu 22.04 the bpftrace package is pretty old, and you would need to install it directly from the repository:

wget https://github.com/bpftrace/bpftrace/releases/download/v0.21.2/bpftrace .
chmod +x bpftrace

Make sure you satisfy the following dependencies:

python3
python3-setuptools
tshark

Then, follow these steps to install svtrace:

git clone https://github.com/seapath/svtrace.git
cd svtrace
python3 setup.py install

Usage

The svtrace.cfg configuration file must be provided to svtrace. The network interface used to receive the IEC61850 Sample Values must be set in the SV_INTERFACE field.

For example:

[DEFAULT]
SV_INTERFACE=enp7s0

To start a measurement and print it directly in terminal, on a hypervisor use the following command:

python3 svtrace.py --live --conf svtrace.cfg --machine hypervisor

To exit svtrace, hit CTRL+C.

In the same way, to start a measurement and record it in a file, use the following command:

python3 svtrace.py --record --conf svtrace.cfg --machine hypervisor

Note: By default:

• results are saved in the /tmp/ directory.
• svtrace is running in live mode.

Release notes

Version v0.1

• Live measurement in terminal
• Record measurement in a file