libobjc/THREADS.MACH

   1 This readme refers to the file thr-mach.c.
   2
   3 Under mach, thread priorities are kinda strange-- any given thread has
   4 a MAXIMUM priority and a BASE priority.  The BASE priority is the
   5 current priority of the thread and the MAXIMUM is the maximum possible
   6 priority the thread can assume.  The developer can lower, but never
   7 raise the maximum priority.
   8
   9 The gcc concept of thread priorities is that they run at one of three
  10 levels;  interactive, background, and low.
  11
  12 Under mach, this is translated to:
  13
  14 interactive -- set priority to maximum
  15 background  -- set priority to 2/3 of maximum
  16 low         -- set priority to 1/3 of maximum
  17
  18 This means that it is possible for a thread with the priority of
  19 interactive to actually run at a lower priority than another thread
  20 with a background, or even low, priority if the developer has modified
  21 the maximum priority.
  22
  23