Minimizing Latency Scheduling of Soft Real Time Systems

Q1. Explain Minimizing Latency Scheduling of Soft Real Time Systems.

Ans. When an event occurs, the system must respond to and service it as quickly as possible. We refer to event latency as the amount of time that elapses from when an event occurs to when it is serviced.

Two types of latencies affect the performance of real time systems, they are as follow:

  1. Interrupt Latency
  2. Dispatch Latency

Interrupt Latency refers to the period of time from the arrival of an interrupt at the CPU to the start of the routine that services the interrupt. When an interrupt occurs, the operating system must first complete the instruction it is executing and determine the type of interrupt that occurred. It must then save the state of the current process before servicing the interrupt using the specific Interrupt Service Routine (ISR). The total time required to perform these tasks is the interrupt latency.

The amount of time required for the scheduling dispatcher to stop one process and start another is known as dispatch latency. Providing real time tasks with immediate access to the CPU mandates that real time operating system minimize this latency. The most effective technique for keeping dispatch latency low is to provide preemptive kernels.

 

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