Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.unix.questions
Subject: Re: Nicer than nice!
Keywords: nice,speed,unix,sysv,priority
Message-ID: <2904@auspex.auspex.com>
Date: 6 Feb 90 21:59:58 GMT
References: <9400@cat.UUCP> <1990Feb5.052345.2120@iwarp.intel.com> <707@umvlsi.ecs.umass.edu>
Organization: Auspex Systems, Santa Clara
Lines: 16

>Nice value of 19 does achieve this. 19 is a special process "priority" and the
>process with that nice value runs only when nothing else in the system 
>wants to.
>Correct me if I wrong.

OK: you're wrong.

There is nothing "magic" about 19, it's just the maximum allowed
"niceness" value on S5 systems (I think it's 20 in 4.xBSD, at least for
x >= 2); in some systems, at least, the priority of a process with a
niceness of 0 can rise above the priority of a process with a niceness
of 19 if the fraction of the CPU that the first priority has been
getting gets high enough.

(BTW, there isn't necessarily one and only one process on the system
with a niceness of 19.)