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Date: Thu, 3 Apr 2003 16:15:51 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: "Daniel O'Connor" <doconnor@gsoft.com.au>
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cc: Jeff Roberson <jroberson@chesapeake.net>
cc: current@freebsd.org
Subject: Re: ULE nice behavior fixed.
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On Thu, 3 Apr 2003, Daniel O'Connor wrote:

> On Wed, 2 Apr 2003 16:24, Jeff Roberson wrote:
> > It probably still needs some tweaking but it seems to be MUCH better now.
> > New algorithm entirely.
> >
> > nice +20 processes will not run if anything else wants to.
> >
> > idleprio is still not working correctly.  bde reports that this causes a
> > 3% perf degradation for buildworld.
>
> Isn't nice +20 == idle prio then?
>
> My understanding was that idle prio didn't run unless nothing else wanted the
> CPU which is what you describe nice +20 as doing :)

Not quite:
- there are 32 different idle priority classes.  All of them give infinitely
  lower (numerically, non-infinitely higher) priority than each other and
  nice +20.
- nice +20 should only only gives infinitely lower priority relative to nice
  +0 or +1.  I hope SCHED_ULE implements this and not what the above says.
  Otherwise, nice +20 would just be a 33rd idle priority class.  Actually,
  I plan to deprecate rtprio(2) and make nice +31 through +52 correspond to
  the 32 idle priority classes.

Bruce