An RTOS (Real-Time Operating System) must align with the application’s requirements. Common
characteristics include:
- Reliability: Embedded systems must operate reliably, often without human intervention.
Reliability varies by application; for instance, a solar-powered calculator can reset without
issue, but a telecom switch must avoid downtime. Highly reliable systems minimize
downtime, often quantified as “number of 9s” indicating availability percentages (e.g.,
99.9999% uptime allows only ~31 seconds of downtime per year). System reliability
depends on the integration of hardware, BSP, RTOS, and application. - Predictability: Critical for real-time systems, predictability ensures tasks meet time
requirements. A deterministic RTOS has predictable behavior, with consistent and known
response times for system calls. Benchmark programs validate this determinism by
measuring response time variances. - Performance: An RTOS must handle tasks swiftly to meet timing requirements,
influenced by both hardware and software. Performance is typically measured in MIPS
(million instructions per second) and throughput, the rate of data processed. System
Compiled by: Deepesh Prakash Guragain
| Unit -3 |
Reference: Real-Time Concepts – Qing Li
9
REAL-TIME OPERATING SYSTEMS
performance can be benchmarked by timing individual system calls, though
comprehensive performance testing assesses the entire system’s functionality. - Compactness: Design constraints, such as those in cell phones, necessitate a small and
efficient RTOS. The RTOS should have a minimal memory footprint, with designers
considering both static and dynamic memory use to meet overall system requirements. - Scalability: An RTOS should adapt to various embedded systems by scaling up or down.
It must support modular additions or deletions, such as file systems or protocol stacks. A
scalable RTOS allows reuse across different projects, saving development time and costs.
