Workshop2 Section2 Flashcards
What do long, medium and short term scheduling deal with?
Long: let’s new processes in and controls multi-programming. Medium: swaps processes between main memory and disk, short: decides which process taken from ready queue and placed next in cpu.
Long term: 3 characteristics?
Divided which process to admit. Makes coarse grained decisions. Executed infrequently.
Medium term: 3 characteristics?
Decides which jobs compete for processor. Acts as buffer between long and short. Executed in response to system load.
Short term: characteristics?
Decides which job to execute next. Makes fine grained decisions. Executed frequently.
What are four short term scheduling criteria?
Clock interrupts, i/o interrupts, OS calls and traps, signals.
How do i/o bound and cpu bound processes differ?
I/O bound: short time spent in cpu before being blocked, waiting for I/O device.
CPU bound: they gig the CPU. Little I/O.
Give examples of user and system oriented scheduling criteria (short term).
User: turnaround time, response time.
System: CPU utilization, fairness, throughout.
Short term scheduling priorities, 4:
Always choose higher priority over lower, lower priority may suffer starvation, use multiple ready queues to represent each level of priority, allow a process to change priority based on age or execution history.
Name 5 processor scheduling algorithms.
Fcfs(first come first served), spn(shortest process next), srt(shortest remaining time), rr(round robin), mlf(multilevel feedback).
Which processor algorithms are preemptive? Which non preemptive?
Non=fcfs,spn.
Preemptive=srt,rr,mlf.
Pre-emotive means processes can be interrupted and resumed at a later time.
What are the six pbjectives of processor scheduling?
Maximize throughput (execute as many processes as possible), minimize response time, minimize turnaround time, minimize waiting time, maximize cpu, ensure fairness.
