From owner-freebsd-hackers@FreeBSD.ORG  Sat Jun 20 18:20:39 2015
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Message-ID: <CAA3ZYrDXmMXk1ZuP0oGd_6G+vKTXtfA6mPAsx_spgojHMnE81Q@mail.gmail.com>
Subject: Re: Realtime process CPU starvation
From: Dieter BSD <dieterbsd@gmail.com>
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For those who care, I'm running
kern.sched.name: ULE

My (feeble) understanding is that the scheduler mostly looks at cpu
time, and processes doing i/o actually get a bump *up* in priority,
since because of the way hardware worked in the late 1970s-early 1980s
(PDP-11, VAX, ...) the i/o got useful work done while using very little
cpu time.  As a result, jobs that do a lot of i/o can receive more
than their fair share of cpu time.  And nice(1) (even rtprio and idprio)
may not have much effect on jobs that are i/o bound.  Some form of
ionice is sorely needed.