CITS2002 Systems Programming  
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Characteristics of processes and threads

Processes Threads
An operating system process requires a lot of 'overhead':

  • process-ID, process group-ID, user-ID, and group-ID
  • environment variables
  • current working directory
  • program instructions
  • registers, stack space, heap space,
  • file descriptors
  • asynchronous signal actions
  • libraries shared with other processes
  • inter-process communication channels (message queues, pipes, semaphores, shared memory).

While threads all share their process's resources, they can be scheduled and execute independently because they duplicate only the essential resources:

  • registers
  • stack pointer (to own stack), heap is shared
  • scheduling properties (such as a timeslice or a priority)
  • set of pending and blocked signals
  • thread specific data.





 

CITS2002 Systems Programming, Lecture 20, p5, 9th October 2023.