Process states / scheduling

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https://wiki.osdev.org/Blocking_Process

Waiting

  • Blocking – state of wait, waiting for event i.e. semaphore released. Not in active scheduling queue.
  • Sleep – Process is set inactive for period of time (i.e. 20ms) while in a sleeping queue.

Busy-waiting – looping indefinitely (undesirable, wastes CPU time).

man ps:

PROCESS STATE CODES         top

       Here are the different values that the s, stat and state output
       specifiers (header "STAT" or "S") will display to describe the state
       of a process:

               D    uninterruptible sleep (usually IO)
               I    Idle kernel thread
               R    running or runnable (on run queue)
               S    interruptible sleep (waiting for an event to complete)
               T    stopped by job control signal
               t    stopped by debugger during the tracing
               W    paging (not valid since the 2.6.xx kernel)
               X    dead (should never be seen)
               Z    defunct ("zombie") process, terminated but not reaped by
                    its parent

 

https://www.tutorialspoint.com/operating_system/os_process_scheduling.htm

http://www.informit.com/articles/article.aspx?p=101760&seqNum=2

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