[H-GEN] Priorities

[Robert Brockway]

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On Fri, 6 Jun 2003, Greg Black wrote:

> The algorithm varies also, but the general feature is that the

Definately, and with some interesting side effects.  Under some unices a
process with a nice value 20 (or whatever maximum nice value happens to
be) is not guaranteed any time on the cpu.  This can lead to an effect
known as "process starvation" where a nice 20 process sits idle forever
because something always has a higher priority and so gets the cpu ahead
of it.  Many unices these days force at least a little time to any process
- even something at nice 20.

Although the idea of starving a process can initially seem attractive (eg,
guaranteeing that seti at home only runs when absolutely nothing else is
occuring) I can see why we would want any process to have at least some
time on the cpu.  Unexpected external events involving the process can
occur (eg, the process may receive a signal), and the process may need
time on the cpu to deal with that.  If a process was starved then it would
never get to deal with the signal, which would be stuck in a kernel data
structure until the end of time :)

Rob

-- 
Robert Brockway B.Sc. email: robert at timetraveller.org  ICQ: 104781119
Linux counter project ID #16440 (http://counter.li.org)
"The earth is but one country and mankind its citizens" -Baha'u'llah

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