(L3.1) Embedded operating systems and frameworks

The RustIEC team wrote an overview paper: Overview of Embedded Rust Operating Systems and Frameworks. It is published in MDPI's special issue: Architectures, Protocols and Algorithms of Sensor Networks - Second Edition.

The paper is available online at https://www.mdpi.com/1424-8220/24/17/5818 and is designed to be readable by a broad audience.

The paper explores Operating Systems and frameworks implemented using the Rust programming language. We compare four prominent Rust-based solutions: two operating systems (Tock and Hubris) and two frameworks (RTIC and Embassy). We evaluate key features such as task scheduling, memory safety, hardware interaction, and networking capabilities, providing a comparative analysis based on performance metrics like interrupt latency and scheduling behavior on an ARM Cortex-M4 platform. The study highlights Rust's advantages over traditional languages like C, including enhanced memory safety and modern concurrency models.

The performance evaluation of interrupt and scheduling latency reveals that Tock has the highest total latency. This is because Tock interrupts a running task and schedules the Interrupt Service Routine (ISR) rather than directly executing the ISR. Additionally, Tock’s handling of the Memory Protection Unit (MPU) introduces further latency.

In contrast, RTIC and Embassy exhibit lower interrupt and scheduling latency. RTIC achieves the lowest latency by leveraging hardware-accelerated scheduling. Embassy, while slightly slower, incurs additional latency due to the overhead of its asynchronous scheduler.

For memory footprint, Tock consists of two main components: the kernel and the applications. The kernel is relatively large compared to other solutions, as it includes a wide range of features that may not be necessary for all applications. Conversely, RTIC and Embassy have a smaller memory footprint since only the required components are included and compiled. Applications built on Tock have a very small memory footprint as it only contains system calls.

Regarding the feature set, Tock offers a rich array of capabilities, including a network stack, MPU support, and hardware abstraction layers accessible via system calls. RTIC and Embassy, on the other hand, focus on real-time performance and low latency. RTIC provides a minimal task scheduler, while Embassy extends its feature set with a task scheduler, asynchronous I/O, and a network stack. Embassy’s network stack is a wrapper around the smoltcp library.