Nicer than nice!

[Jaap Akkerhuis]

Excerpts from netnews.comp.unix.questions: 5-Feb-90 Re: Nicer than nice!
Jean-Francois Lamy at cs.ut (1522)

> someone wrote:
> >> Is there a possibility to change the priority of a process more than a
> >> 'nice -19' would do? I would like be able to start programs in background

> to which Randal Schwartz replied:
> >>the scheduler.  There isn't anything in off-the-shelf UNIX that tags the
> >>process as "don't run this unless nobody else is doing much of anything."

> and Uday Hegde confuses matters by saying:
> >process with that nice value [-19] runs only when nothing else in the system 
> >wants to.
> >Correct me if I wrong.

> Indeed.  The scheduler uses niceness as one of many factors in determining
> priority.  In *practice*, several maximally niced jobs can still impact
> significantly the system performance.  Recent SunOS releases seem especially
> prone to this behaviour (I will dispense you from my pet theories on the topic
> because I'd like to check them with the source first, should we *ever* receive
> it).

UNIX Edition 7 had the same problem. If I remember correctly, it was
caused by the fact that the swapper swapped anything in which hadn't be
in for a while and then the scheduler deciced it was a real nice
process, so it was swapped out again before being run. So processes
which were supposed to soak up only idle time still had an impact on the
system.

	jaap