Tag: scheduler

Deterministic Scheduling

Posted on by lechuck park

With Claude
Definition: Deterministic Scheduling is a real-time systems approach that ensures tasks are completed within predictable and predefined timeframes.

Key Components:

  1. Time Predictability
  • Tasks are guaranteed to start and finish at defined times
  1. Task Deadlines
  • Hard Real-Time: Missing a deadline leads to system failure
  • Soft Real-Time: Missing a deadline causes performance degradation but not failure
  1. Priority Scheduling
  • Tasks are prioritized based on their criticality
  • High-priority tasks are executed first
  1. Resource Allocation
  • Efficient management of resources like CPU and memory to avoid conflicts
  • Uses Rate-Monotonic Scheduling (RMS) and Earliest Deadline First (EDF)

Advantages (Pros):

  • Guarantees timing constraints for tasks
  • Improves reliability and safety of systems
  • Optimizes task prioritization and resources

Disadvantages (Cons):

  • Complex to implement and manage
  • Priority inversion can occur in some cases
  • Limited flexibility; tasks must be predefined

The system is particularly important in real-time applications where timing and predictability are crucial for system operation. It provides a structured approach to managing tasks while ensuring they meet their specified time constraints and resource requirements.

Interrupt

Posted on by lechuck park

From Claude with some prompting
The image illustrates the process of handling interrupts in a computer system. When an urgent job (Urgent Job Occurred) arises while another job (One Job is Working) is executing, an interrupt (Job Switching = Interrupt) occurs. This triggers the Interrupt Service Routine (ISR) to handle the interrupt.
The interrupt handling process is divided into two halves: the Top Half and the Bottom Half. The Top Half performs a “Very Short Work to avoid another job delay” and notifies the system of the interrupt occurrence. The Bottom Half handles the remaining work, also performing “Short Work to avoid another job delay.”

Process scheduler

Posted on by lechuck park

From DALL-E with some prompting
The image highlights the essential mechanisms of process scheduling to share a single CPU core resource among multiple processes. The scheduler determines the order of processes to be executed based on priority and changes the current running process through context switching. Additionally, it promptly addresses exceptions requiring urgent processing through interrupts and real-time handling. This scheduling approach ensures efficient allocation of CPU resources and stable operation of the system.