Lecture 7: Multiprogramming

Question 1

Define: Multiprogramming

Answer 1

Allows for the execution of multiple processes but only one process active at any time.

Question 2

Define: Interleaved Execution

Answer 2

A single-core processor runs only 1 process at a time - however, one process’s instructions may be executed before the completion of the instructions from another process.

Question 3

What is the objective of Interleaved Execution?

Answer 3

To have some process running at all times in order to maximize CPU utilization.

Question 4

Define: Process Control Block

Answer 4

PCB characterizes each process. The block contains all info on a process’s/program’s state that is in execution.

Question 5

What specific information does a PCB store for each process / program in execution?

Answer 5

1) Pointer to all Process Info (Text, Data, Stack, Heap)
2) Program Counter
3) Current values inside General-purpose registers
4) A set of operating system resources
5) PID
6) Process Priority for scheduling
7) Process State
8) A pointer to the next PCB in the Ready queue linked-list

Question 6

What is the C Structure used to store the PCB?

Answer 6

A Struct called task_struct

Question 7

How are all active process stored / represented in Linux?

Answer 7

• Double-Linked List of task_structs

- Kernel maintains a pointer, “current”, that points to the process currently executing on the system

Question 8

How are Queues, used for the “ready” processes, implemented?

Answer 8

As a linked-list. A ready queue header contains pointers to the first and last final process control blocks in the list.

Question 9

Define: Device Queue

Answer 9

List of processes waiting for a particular I/O device