job scheduling

External storage -> memory (job-oriented)

Select the appropriate job from the backup queue, load it into memory, and create a process for it

memory scheduling

External memory -> memory (process-oriented)

According to certain rules, select the appropriate process from the suspension queue and transfer the data back to the memory

process scheduling

Memory -> CPU (concurrent scheduling)

According to certain rules, select processes from the ready queue to allocate processors

give up voluntarily

passively give up

When process scheduling cannot be performed

non-preemptive scheduling

Preemptive scheduling

busy time/total time

Number of tasks completed/total time

turnaround time

average turnaround time

Rights turnaround time

Average rights turnaround time

The sum of the time the process/job waited to be serviced

The time from when a user submits a request to the first response

Non-preemptive

advantage

shortcoming

Consider waiting time

Does not cause hunger

Default is non-preemptible, preemptible

advantage

shortcoming

Consider running time

can cause hunger

Non-preemptive

advantage

Consider waiting time and running time

Does not cause hunger

Preemptive

advantage

shortcoming

Time slice settings

Does not cause hunger

Both preemptive and non-preemptive

advantage

shortcoming

can cause hunger

Preemptive

advantage

Disadvantages are generally not mentioned

can cause hunger

Multiple queues are divided according to process type, and different queues have different priorities.

Scheduling methods between queues

Different queues can adopt different scheduling strategies