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Date:      Thu, 8 Apr 1999 19:04:51 -0500
From:      "Richard Seaman, Jr." <dick@tar.com>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        David Greenman <dg@root.com>, "John S. Dyson" <dyson@iquest.net>, aron@cs.rice.edu, freebsd-hackers@FreeBSD.ORG
Subject:   Re: scheduling queues in FreeBSD
Message-ID:  <19990408190450.L440@tar.com>
In-Reply-To: <199904082341.QAA15598@apollo.backplane.com>; from Matthew Dillon on Thu, Apr 08, 1999 at 04:41:03PM -0700
References:  <199904082248.PAA21483@implode.root.com> <199904082341.QAA15598@apollo.backplane.com>

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On Thu, Apr 08, 1999 at 04:41:03PM -0700, Matthew Dillon wrote:

>     I think it would be useful for 'idle' priority processes, but I agree
>     that it would not be useful for any sort of true 'realtime' ( i.e. 
>     when there is more then one realtime process ).  But the existing
>     realtime scheduler isn't useful for true realtime either since there
>     are no scheduling primitives.
> 
>     If nobody xxxx not to many people have objections, I would be happy to
>     remove the realtime & idle queue junk and replace it with the locked 
>     priority concept. ( Cavet: the priority would only be locked while 
>     running in user mode, I wouldn't mess with the supervisor sleep priority
>     override mechanism ).   This would make idle processes useful again.
>     I would also be happy if someone else did this... but if nobody else
>     wants to, I can :-)

I think Peter Dufault did some work about 3 months ago, that he was about
ready to commit, that was a significant rework of the priority related code,
and which fixed the buggy sched_* functions, and which would have put them
into the kernel by default.  I assume he got sidetracked.  

I think there are some "bugs" even in the normal priority scheduling code.

I think the last version was at:

ftp://ftp.freebsd.org/pub/FreeBSD/development/misc/PATCHES.sched

The linux emulation code, especially the linuxthreads code, really needs
working sched_* functions.  Whether they they implement fully "real time" 
scheduling, whatever that means, is not so important.

-- 
Richard Seaman, Jr.           email: dick@tar.com
5182 N. Maple Lane            phone: 414-367-5450
Chenequa WI 53058             fax:   414-367-5852


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