Introducing preemptive scheduling in abstract RTOS models using result oriented modeling

ABSTRACT

With the increasing SW content of modern SoC designs, modeling and development of Hardware Dependent Software (HDS) become critical. Previous work addressed this by introducing abstract RTOS modeling [6], which exposes dynamic scheduling effects early in the system design flow. However, such models insufficiently capture preemption. In particular, the accuracy of preemption depends on the granularity of the timing annotation. For an accurately modeled interrupt response time, very fine-grained timing annotation is necessary, which contradicts the RTOS abstraction idea and is detrimental to simulation performance.

In this paper, we eliminate the granularity dependency by applying the Result Oriented Modeling (ROM) technique previously used only for communication modeling. Our ROM approach allows precise preemptive scheduling, while retaining all the benefits of abstract RTOS modeling. Our experimental results demonstrate tremendous improvements. While the traditional model simulated an interrupt response time with a severe inaccuracy (12x longer in average and 40x longer for 96^th percentile), our ROM-based model was accurate within 8% (average and 50^th percentile) using identical timing annotations.

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INDEX TERMS

Primary Classification:
  D. Software
  D.4 OPERATING SYSTEMS
      D.4.1 Process Management
          Subjects: Scheduling

Additional Classification:
  D. Software
  D.4 OPERATING SYSTEMS
      D.4.7 Organization and Design
          Subjects: Real-time systems and embedded systems
      D.4.8 Performance
          Subjects: Modeling and prediction; Operational analysis; Simulation

General Terms:
Algorithms, Design, Performance