Date: Thu, 20 Jan 2005 09:05:45 +0100
From: Ingo Molnar <mingo@elte.hu>
To: "Jack O'Quin" <joq@io.com>
Cc: Chris Wright <chrisw@osdl.org>, Matt Mackall <mpm@selenic.com>,
       Paul Davis <paul@linuxaudiosystems.com>,
       Christoph Hellwig <hch@infradead.org>, Andrew Morton <akpm@osdl.org>,
       Lee Revell <rlrevell@joe-job.com>, arjanv@redhat.com,
       alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [request for inclusion] Realtime LSM
Message-ID: <20050120080545.GA12665@elte.hu>
References: <871xcmuuu4.fsf@sulphur.joq.us> <20050116231307.GC24610@elte.hu> <87vf9xdj18.fsf@sulphur.joq.us> <20050117100633.GA3311@elte.hu> <87llaruy6m.fsf@sulphur.joq.us> <20050118080218.GB615@elte.hu> <87pt02pt0r.fsf@sulphur.joq.us> <20050119082433.GE29037@elte.hu> <20050119143927.GA11950@elte.hu> <87651tmhwv.fsf@sulphur.joq.us>
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* Jack O'Quin <joq@io.com> wrote:

> JACK actually uses three different priorities, the defaults are 9, 10
> and 20.  How about if I change this test?
> 
> 	if (prio <= 20 && policy != SCHED_NORMAL) {

yeah, this is OK. 20 is used for the watchdog thread, right? (so it has
minimal latency impact). What's the difference between prio 9 and 10
threads? You might want to map prio 9 ones to nice--15 and prio 10 ones
to nice--20, if there's a real difference between them. But for the
first test i'd suggest to use nice--20 for both. (to make sure
SCHED_OTHER tasks interfere as rarely as possible.)

> Or, should that be?
> 
> 	if (prio > 0 && prio <= 20 && policy != SCHED_NORMAL) {

'prio' cannot get negative here, so the first test is just as fine.

	Ingo
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