About the microkernel and RTOS
What is a kernel and what are some kernel architectures?
Kernel space is a memory area in an operating system where the core components of the OS execute. This space is reserved for running privileged operations and providing essential services to the system.
Monolithic kernel architectures kernel space generally includes device drivers and kernel extensions. Since most services run in the same address space (kernel space), an advantage of a monolithic architecture is that system calls can be executed faster due to the lack of context switching.
Microkernel operating system architecture includes only the minimal necessary components to manage system resources and provide basic services. Unlike monolithic kernels, which include many services within the kernel itself, microkernels run most services in user space. This design aims to improve system reliability and security by isolating critical functions from less critical ones. Microkernel architectures are safer since service failures in user space don’t affect the kernel, making the system more resilient. Since microkernel architectures don’t share the same address space, they rely on inter-process communication (IPC) to communicate with the kernel or other services.
Some examples of services that are outside kernel space in QNX are:
- Networking
- File I/O
- Serial communications
What is an RTOS?
The following table illustrates some differences between RTOS and non-real-time operating systems:
| Area | RTOS | Non-RTOS |
|---|---|---|
| Time Constraints | Ensures tasks are completed within strict time constraints. |
Doesn't guarantee timing constraints and focuses on overall system performance. |
| Scheduling Scheme | Uses priority-based and pre-emptive scheduling to ensure critical tasks are executed on time. | Typically uses time-sharing or round-robin scheduling, which may not prioritize time-critical tasks. |
| Determinism | Provides deterministic behavior, meaning the response time is predictable and consistent. | May have variable response times, leading to unpredictability in task execution. |
| Use Cases | Used in applications where timing is crucial, such as embedded systems, industrial automation, and robotics. | Used in general-purpose computing where timing is less critical, such as desktop operating systems and servers. |
In summary, an RTOS is designed to meet the stringent timing requirements of real-time applications, ensuring tasks are completed within specified deadlines. In contrast, non-real-time operating systems prioritize overall system performance and user interaction, without guaranteeing precise timing.