Processes, Threads and Scheduling

1
Processes, Threads and Scheduling

• OS Lecture 4

2
Processes

• Unit of resource allocation in the OS
• Allocation of space
• Clock time
• The abstraction of a process provides fault
  isolation between different programs (read
  processes)
• Each process lives in its own world
• OS gives each process the illusion that it is the
  king of all resources, including processor time

3
Threads

• Unit of execution
• Assign a thread to a process to make it
  runnable
• Can have multiple threads in a process
• Threads share state -- no fault isolation
• Typically, threads also share the time-quantum
  allocated to their process
• Creating more threads typically does not mean
  your process will get more time on the processor

4
So why use threads?
Concurrency to mask blocking I/O
Operating System
Zzzzzz
file.read
5
(No Transcript)