Real-time Linux

RT preemption

The Linux Foundation's Real-Time Linux (RTL) collaborative project is focused on improving the real-time capabilities of Linux and advancing the adoption of real-time Linux in various industries, including aerospace, automotive, robotics, and telecommunications.

Parameter CONFIG_PREEMPT_RT_id enables real-time preemption.

RT scheduling policies

Scheduling policies for RT:

SCHED_FIFO_id, SCHED_RR_id

implemented in kernel/sched/rt.c_src

SCHED_DEADLINE

implemented in kernel/sched/deadline.c_src

API:

man 1 chrt – manipulate the real-time attributes of a process

man 2 sched_rr_get_interval – get the SCHED_RR interval for the named process

man 2 sched_setscheduler, sched_getscheduler – set and get scheduling policy/parameters

man 2 sched_get_priority_min, sched_get_priority_max – get static priority range

Testing RT capabilities

The testing process for Real-Time Linux typically involves several key aspects. First and foremost, it is crucial to verify the accuracy and stability of the system's timekeeping mechanisms. Precise time management is fundamental to real-time applications, and any inaccuracies can lead to timing errors and compromise the system's real-time capabilities.

Another essential aspect of testing is evaluating the system's scheduling algorithms. Real-Time Linux employs advanced scheduling policies to prioritize critical tasks and ensure their timely execution. Testing the scheduler involves assessing its ability to allocate resources efficiently, handle task prioritization correctly, and prevent resource contention or priority inversion scenarios.

Furthermore, latency measurement is a critical part of Real-Time Linux testing. Latency refers to the time delay between the occurrence of an event and the system's response to it. In real-time applications, minimizing latency is crucial to achieving timely and predictable behavior. Testing latency involves measuring the time it takes for the system to respond to various stimuli and identifying any sources of delay or unpredictability.

Additionally, stress testing plays a significant role in assessing the system's robustness under heavy workloads. It involves subjecting the Real-Time Linux system to high levels of concurrent activities, intense computational loads, and input/output operations to evaluate its performance, responsiveness, and stability. Stress testing helps identify potential bottlenecks, resource limitations, or issues that might degrade the real-time behavior of the system.

RTLA – The realtime Linux analysis tool:

rtla timerlat_doc – CLI for the kernel's timerlat tracer_doc