Miscellaneous Topics
The CPU can be in any of these two modes.
What are kernel and user modes?
It selects among available processes for the next execution on the CPU.
What is the process scheduler?
It is not invoked relatively often and selects which processes should be brought into the ready queue.
What is the long-term scheduler?
This scheduling algorithm allocates processor time in order of arrival.
What is FCFS?
These conditions are necessary for deadlocks to occur.
What are mutual exclusion, no preemption, hold-and-wait, and circular waiting?
This is the fastest memory available in a computer.
What are CPU registers?
This allows a process to transition from user mode to kernel mode voluntarily.
What is system call?
An integer that can be atomically incremented and decremented and is not allowed to have a negative value.
What is a semaphore?
This scheduling algorithm runs each process in a small fixed unit of CPU time.
What is Round Robin?
A cycle in that graph is a necessary condition of a deadlock.
What is resource allocation graph?
In Project 1, you used that technique to draw pixels in a fluid manner.
What is double buffering?
This type of process has exit()'ed and its parent has not terminated yet but is not wait()'ing for it.
What is a zombie process?
This type of locks is inefficient in single-core systems.
What are spinlocks?
The most important parameter to optimize in an operating system for interactive applications.
What is response time?
In these approaches, deadlocks never occur.
What are deadlock prevention and deadlock avoidance?
Linux is that type of kernel.
What is monolithic kernel?
In that type of threading, when a thread performs a blocking I/O system call, all threads in the same process are blocked.
What is user-level threading?
This property is violated when a process can immediately and unconditionally renter a critical section while other processes are waiting to enter the same critical section.
What is bounded waiting?
The default scheduling policy in Xv6.
What is Round-Robin?
Suppose there are two semaphores, A and B. If process 1 does: down(A); down(B), while process 2 does: down(B); down(A), then we have that type of synchronization bug.
What is deadlock?
Because of that overhead, spinlocks are more efficient than sleeplocks in multi-core systems when the critical section is short.
What is context switching overhead?
Consider a highly-interactive I/O-bound process that is in the WAITING state. This is the state into which the process transitions after being unblocked.
What is READY?
Suppose there are two semaphores, A and B. If process 1 does: down(A); down(B), while process 2 does: down(A); down(B), then we may have that type of synchronization bug.
What is order violation?
Let (x, y, z) mean that process x arrives at time y and needs z time units of processing time:
(A, 0, 15), (B, 0.1, 3), (C, 2, 2), (D, 5, 1)
Calculate the average wait time when using Round robin with a quota of 2 units assuming C gets into the ready queue ahead of A at time = 2.
What is 4 + 0.475?
Given the following system with four processes 1, .., 4 and four resources A, .., D, for what values of x is the system in a safe state? Hint: Use the Banker’s algorithm.
Allocation Maximum Available
A B C D A B C D A B C D
Process 1 3 2 3 5 3 3 x 5 0 1 0 0
Process 2 1 1 2 2 1 2 4 2
Process 3 1 0 0 3 2 1 0 3
Process 4 0 1 0 0 2 2 2 1
What is 2+1?