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Date:      Tue, 26 Mar 2002 09:16:21 -0800
From:      Lars Eggert <larse@ISI.EDU>
To:        Andrew <andrew@ugh.net.au>
Cc:        Volker Stolz <stolz@hyperion.informatik.rwth-aachen.de>, Ian <freebsd@damnhippie.dyndns.org>, hackers@freebsd.org
Subject:   Re: idprio
Message-ID:  <3CA0ACE5.5000906@isi.edu>
References:  <20020326232510.A21338-100000@starbug.ugh.net.au>

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Andrew wrote:
 >> Under FreeBSD system calls are currently never preempted, therefore
 >> non- realtime processes can starve realtime processes, or idletime
 >> processes can starve normal priority processes.
 >
 > Even so an idprio process can't be worse than a normal process.

Practically this means "you will still see a drop in your
foreground performance." Theoretically, however, you can construct
scenarios where your foreground stuff is starved ad infinitum due to
priority inversion. (Since some/most non-CPU resources don't support 
priorities and preemption.)

Lars
-- 
Lars Eggert <larse@isi.edu>               Information Sciences Institute
http://www.isi.edu/larse/              University of Southern California

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