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Date:      Mon, 18 Sep 2000 00:52:41 +1100 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        Alexander Leidinger <Alexander@leidinger.net>
Cc:        current@FreeBSD.ORG, jhb@FreeBSD.ORG
Subject:   Re: 100% system time? (SMPng on UP system)
Message-ID:  <Pine.BSF.4.21.0009180034230.11515-100000@besplex.bde.org>
In-Reply-To: <200009170957.e8H9van02062@Magelan.Leidinger.net>

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On Sun, 17 Sep 2000, Alexander Leidinger wrote:

> On 17 Sep, Bruce Evans wrote:
> 
> >> dnetc runns with idprio 31, system cvsupped around Sep 16, 11 CEST from
> >> a german mirror (it contains the idle fixes: src/sys/kern/kern_idle.c,v
> >> 1.4), complete build{world,kernel}.
> >> 
> >> ---snip---
> >> last pid:  1666;  load averages:  1.10,  1.11,  1.03    up 0+00:51:21  16:54:14
> > 
> > Perhaps it really is a system process :-[.  idprio on a pure cpu hog prevents
> > other user processes from running like a system process might do:
> > 
> > 	idprio 31 sh -c "while :; do :; done"
> > 
> > System processes actually hang the entire system until they complete:
> 
> Are you mixing idprio with rtprio or did I not understand what you
> explain?

You didn't understand :-).  Try the example.  It only uses idprio.

rtprio certainly causes system hangs, and the supergiant lock may
increase the problem.  Before SMPng, rtprio processes prevented all
non-rtprio processes including important daemons (and I think even
kernel processes) from running.  Starting an infinite loop at rtprio
while remotely logged in was fatal because a ^C (character, not signal)
to kill the process couldn't be delivered.

Bruce



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