Date: Sun, 24 Oct 2004 23:23:59 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Jon Masters <jonathan@jonmasters.org>
Cc: paulmck@us.ibm.com, Thomas Gleixner <tglx@linutronix.de>,
       LKML <linux-kernel@vger.kernel.org>, karim@opersys.com
Subject: Re: [RFC][PATCH] Restricted hard realtime
Message-ID: <20041024212359.GA7328@elte.hu>
References: <20041023194721.GB1268@us.ibm.com> <1098562921.3306.182.camel@thomas> <20041023212421.GF1267@us.ibm.com> <35fb2e5904102315066c6892aa@mail.gmail.com> <20041024153204.GA1262@us.ibm.com> <417C19D5.7050802@jonmasters.org>
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* Jon Masters <jonathan@jonmasters.org> wrote:

> I guess it would. But then we've just had a slew of RT implementations
> crawl out of the woodwork and wave at us over the past few weeks and
> there are three other major RT implementations which combine Linux
> with a Microkernel or other external support (RTLinux, RTAI, KURT,
> etc.). Perhaps it's worth working on one of the Linux patch projects
> (Monta/Ingo/etc.) rather than going all out to implement it all again.

also note that (as i mentioned it in an earlier reply to Paul) the
'CPU[s] isolated for hard-RT use' scheduler feature has already been
implemented by Dimitri Sivanich and was accepted and integrated into the
2.6.9 kernel a couple of weeks ago.

Isolated CPUs can be set up via the "isolcpus=" boot parameter, and can
be entered via the affinity syscall. The feature came with related fixes
to the scheduler and other kernel code to eliminate cross-effects
between domains. (such as the scheduler balancing code, or the swap
tick)

So this all is banging on open doors, this particular mode of hard-RT
scheduling is there and available in vanilla Linux. If anyone wants to
try it, just download 2.6.9 and use it.

	Ingo
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