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Date: Fri, 7 Apr 2006 15:18:50 -0700
To: Ingo Molnar <mingo@elte.hu>
Cc: Darren Hart <darren@dvhart.com>, linux-kernel@vger.kernel.org,
       Thomas Gleixner <tglx@linutronix.de>,
       "Stultz, John" <johnstul@us.ibm.com>,
       Peter Williams <pwil3058@bigpond.net.au>,
       "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>,
       "Bill Huey (hui)" <billh@gnuppy.monkey.org>
Subject: Re: RT task scheduling
Message-ID: <20060407221850.GA17303@gnuppy.monkey.org>
References: <200604052025.05679.darren@dvhart.com> <20060406073753.GA18349@elte.hu> <20060407030713.GA9623@gnuppy.monkey.org> <20060407071125.GA2563@elte.hu> <20060407083931.GA11393@gnuppy.monkey.org> <20060407091946.GA28421@elte.hu> <20060407103926.GC11706@gnuppy.monkey.org> <20060407105141.GA9972@elte.hu> <20060407111444.GA12458@gnuppy.monkey.org> <20060407112956.GA17277@elte.hu>
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From: Bill Huey (hui) <billh@gnuppy.monkey.org>
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On Fri, Apr 07, 2006 at 01:29:56PM +0200, Ingo Molnar wrote:
> * Bill Huey <billh@gnuppy.monkey.org> wrote:
> > First thing's first, SCHED_FIFO_GLOBAL for what you want in the main 
> > line is the same thing as SCHED_FIFO in -rt, right ?
> 
> yes.

Ok, good, we're getting some where. IMO, SCHED_FIFO_GLOBAL doesn't add
anything to existing Linux scheduling policies for it to be really
distinct than SCHED_FIFO. I'd much see that feature collapsed into a
into SCHED_FIFO intrinsically. In fact, that's the way it should be in
a solid RTOS. Creation of run categories that are so similar doesn't
really add to the "meaning" of the system, since SCHED_FIFO was kind
of hammered in the first place, just make SCHED_FIFO do that strict
priority stuff across all processors as a default property.

Whether this belongs in the main line or not is questionable. My guess
is probably not. But I definitely think it should go into -rt and it
would be much more warmly received by folks developing on that kernel
patch to know that SCHED_FIFO has this strict behavior. It's actually
needed in that patch IMO. Following ?

bill