Chapter 14 Flashcards
What is short term scheduler
It decides and select which process to give to CPU from ready queue
What is life of a process
Life of a process depends upon 2 types of bursts
1. CPU burst (execute CPU instructions)
2. I/O burst (wait stage of process for CPU)
and at last process use CPU and terminate.
What is the example of a process which have less CPU burst and longer I/O burst
Editor
What is dispatcher
Dispatcher gives control of CPU to process selected by short-term scheduler
What is dispatcher latency
Dispatcher latency is the time it takes for the dispatcher to stop one process and start another running (typically a few microseconds)
When CPU scheduler (short term scheduler) invokes
It invokes in following 4 conditions
- Switches from running to waiting state
- Switches from running to ready state
- Switches from waiting to ready state
- Terminates
What is non-preemptive scheduler
Such a scheduler which assign CPU to a process and process does not completely complete its CPU burst and CPU does not granted back from him, called non-preemptive scheduler. Its example is
- Switches from running to waiting state
- Terminates
What is preemptive scheduler
All other schedulers which are not non-preemptive
Why we use scheduler
- CPU utilization : keep CPU busy to maximum
- Throughput : # of processes that complete their execution per time unit
- Turnaround time: amount of time to execute a particular process
- Waiting time: Amount of time a process waits in ready queue
- Response time: amount of time it takes from when a request was submitted until the first response is produced, not output.
Response time is important for which 2 types of systems
- Time sharing system
2. Real time system
What is FCFS scheduling
First come first serve scheduling deals in a way that the process which comes first will be assigned to CPU first. and same treatment is done with other processes. first come first serve basis.
How we calculate wait time
When process come in queue and when It get CPU
What is convoy effect
In first come first serve scheduling, a CPU-prone process takes longer time and I/O prone process wait and when it free CPU all waiting processes goes for CPU quickly in their turn. Then CPU prone process again comes in CPU. This is called convoy effect.
