README.md

Jitter meter for Linux hosts

General-purpose Linux distributions require special setup for real-time applications. If installed on general-purpose hardware, some aspects may be also tuned. See Configuring the system for RoboPLC.

Furthermore, the applications can behave differently on different CPU cores due to IRQs or little-big architecture peculiarities.

This tool measures jitters for each CPU core (difference between specified and real loop time) and provides a report.

Usage

Clone the repository to the local machine.

With RoboPLC Manager installed

If RoboPLC Manager is installed on the target machine, the tool can be flashed with the following command (see Flashing):

robo flash

(either edit robo.toml or use proper command-line arguments to specify the destination). After flashing, the report can be viewed at RoboPLC Manager Metrics page.

Without RoboPLC Manager installed

Install Rust and compile:

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
cargo build --release

Copy the binary to the target machine and run it. The report can be obtained with

curl -s http://IP:9000

and optionally connected to any Prometheus-compatible monitoring system.

Loop interval

By default, the program uses 1000us (1ms) loop interval. It can be changed with "INTERVAL" environment variable at compile-time:

INTERVAL=500 cargo build --release # for 500us

If using cross for cross-compilation, the variable must be set as a Docker option:

DOCKER_OPTS="-e INTERVAL=500" cross build --release

(the provided script flash.sh can help with this as well).