Thread

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Overview

Thread

A thread is an independent sequence of execution within the program

• a thread is similar to a process
  • both have single sequential flow of control with a start and end
  • at any time a thread has a single point of execution
  • a thread has its execution stack and program counter
  • sometimes a thread is called a lightweight process
• a thread differs from a process
  • threads cannot exist independently
    • they exist within a process
  • usually created and/or controlled by a process
  • threads can share a process' resources, including memory and open files
• some languages support thread programming
  • e.g. Java

Thread Application Example

• Threads typically used in the server side
  • e.g. database servers
• conventional database system uses one process per request
• OS may be overwhelmed by too many active processes

Therefore:

• Server provides come real processes
  • they act as virtual processors
• each virtual processor runs multiple threads
• thread based database system uses 1 thread per request