To Preempt or Not To Preempt, That Is the Question

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Blackham, Bernard; Tang, Vernon; Heiser, Gernot

Blackham, Bernard; Tang, Vernon; Heiser, Gernot


2012-07-23


Conference Material


Asia-Pacific Workshop on Systems (APSys)


Seoul, Korea


7


Real-time operating systems (RTOSes) are traditionally designed to be fully preemptible. This improves the average interrupt response time of the system but increases kernel complexity. An alternative design is to make the kernel mostly non-preemptible and only handle pending interrupts at specific preemption points within the kernel. It is often said that this design leads to poor interrupt response times. However, for hard real-time systems the key requirement is on worst-case interrupt latencies. We claim that for a protected-mode RTOS, as required for multi-criticality systems, non-preemptible kernels can achieve worst-case latencies comparable to those of fully-preemptible kernels. In order to understand the latency limits achievable in both approaches, we analyse and compare the worst-case interrupt latencies of a fully-preemptible commercial RTOS (QNX) and a non-preemptible real-time kernel (seL4). Our results indicate that a non-preemptible kernel can achieve interrupt latencies which are within a factor of two from those exhibited by a fully-preemptible kernel.


ACM


real-time systems, trustworthy systems, microkernels


https://doi.org/10.1145/2349896.2349904


http://apsys2012.kaist.ac.kr/


nicta:5859


Blackham, Bernard; Tang, Vernon; Heiser, Gernot. To Preempt or Not To Preempt, That Is the Question. In: Asia-Pacific Workshop on Systems (APSys); Seoul, Korea. ACM; 2012-07-23. 7. https://doi.org/10.1145/2349896.2349904



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