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Groups > comp.arch.embedded > #12831
| From | Don Y <this@isnotme.com> |
|---|---|
| Newsgroups | comp.arch.embedded, comp.realtime |
| Subject | Re: Resource revocation |
| Date | 2013-07-29 12:07 -0700 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <kt6ei0$2he$1@speranza.aioe.org> (permalink) |
| References | (11 earlier) <_riJt.598075$%p1.483412@en-nntp-02.dc1.easynews.com> <kt4gtl$q0g$1@speranza.aioe.org> <HWlJt.4$nK2.2@en-nntp-11.dc1.easynews.com> <kt559c$6s7$1@speranza.aioe.org> <7xfvuxx02j.fsf@ruckus.brouhaha.com> |
Cross-posted to 2 groups.
Hi Paul,
On 7/29/2013 1:05 AM, Paul Rubin wrote:
> Don Y <this@isnotme.com> writes:
>> And:
>> "It is clear that in the technical sense defined here (as opposed
>> to popular misusage by practitioners),
>
> The author is admitting above to peddling an idiosyncratic concept that
> doesn't match the usage of working practitioners in the real world.
> Therefore I don't feel compelled to treat it as gospel.
You might want to read his entire treatise, carefully (i.e., as
if you were trying to LEARN it) and then examine his pedigree
before dismissing his (well thought out) argument.
>> soft real-time systems are considerably more difficult to create
>> than are hard real-time ones.
>
> That's just plain silly. There are all kinds of random timing
> variations in a conventional computer system, due to cache memory,
> rotating disk drives, input data distributions (think of algorithms like
> hash tables with bad worst-case complexity), background servics
> contending for system resources, etc.
Sure! But many of these the RT developer implements deterministically
instead of relying on some generic implementation NOT suited to RT.
> In an SRT system with some
> specifications on the inputs, you can estimate or measure the
> distribution of those timing variations, run some tests to make sure
> stuff appears to work as expected, and you're done. You don't have to
> worry about rare outliers causing timing misses, since by definition
> occasional misses are acceptable.
You're leaving performance entirely to chance. Making no attempt
to maximize it! "Oh, well... technically this task could be
6 hours late in meeting it's deadline... <shrug>"
> HRT requires sharp bounds on every
> operation and (in practice) normally very short deadlines, which impose
> a lot of constraints on the implementation.
Yeah, but the approach you described is exactly how you tackle
HRT! You figure out what its worst case performance characteristics
are -- then specify hardware/resources that will PROVIDE that level
of service: "The system NEEDS it!". Done.
You end up with more resources than you need because you have been
*forced* to expect everything to go wrong. (as an *informal*
testament of this, look at the maximum utilization for the rate
monotonic algorithm which GUARANTEES schedulabilty -- roughly 50%
excess capacity "just in case")
With SRT, you (assuming your goal is to provide the best possible
performance and not just "hey, it sorta works") have to evaluate
your options at each step. All eligible tasks have to be considered
regardless of the value of their utility functions AT THIS INSTANT
IN TIME. You can't dismiss tasks (HRT) whose deadlines have
passed because there still is tangible value in meeting those
goals. You don't just pick any task and let it run KNOWING
that it may make some other task late ("What the heck, that
task's deadline is soft so it *can* be late -- even if a better
scheduling choice could have caused it to NOT be late!")
Why not just schedule the remaining SRT tasks in ALPHABETICAL
ORDER? What the heck! Some WILL probably end up late but
they shouldn't care, right??
Think about it. It *should* be obvious!
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Resource revocation Don Y <this@isnotme.com> - 2013-07-25 12:23 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-25 12:51 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-25 15:00 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-25 19:38 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-25 22:12 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-25 23:37 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 01:13 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 02:48 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 04:19 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 09:46 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 10:21 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 19:30 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 11:56 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 20:08 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 13:11 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 12:31 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 11:08 -0700
Re: Resource revocation Rob Gaddi <rgaddi@technologyhighland.invalid> - 2013-07-29 09:16 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-29 10:22 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 11:22 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 08:56 -0700
Re: Resource revocation Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-07-26 19:25 +0200
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 10:51 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 19:21 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-26 11:50 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 19:42 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 12:43 -0700
Does the Buddha have a real time nature? ;) (was Resource revocation) Roberto Waltman <usenet@rwaltman.com> - 2013-07-26 17:06 -0400
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Don Y <this@isnotme.com> - 2013-07-26 17:12 -0700
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 09:44 +0100
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 09:45 +0100
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Don Y <this@isnotme.com> - 2013-07-27 12:28 -0700
Re: Does the Buddha have a real time nature? ;) (was Resource revocation) Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-07-27 14:11 +0200
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 12:40 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 21:29 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 13:52 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-26 22:55 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 17:22 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 10:02 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 09:29 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 18:20 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 12:48 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 22:57 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 16:18 -0700
Re: Resource revocation Roberto Waltman <usenet@rwaltman.com> - 2013-07-31 16:33 -0400
Re: Resource revocation upsidedown@downunder.com - 2013-07-27 22:53 +0300
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 22:42 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 16:41 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-27 16:49 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-28 08:39 +0300
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 23:11 -0700
Re: Resource revocation Roberto Waltman <usenet@rwaltman.com> - 2013-07-31 16:15 -0400
Re: Resource revocation upsidedown@downunder.com - 2013-08-01 00:13 +0300
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 15:16 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 23:05 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 15:37 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 23:38 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 16:08 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-28 01:16 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 18:43 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-28 09:01 +0300
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-27 15:21 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-27 23:07 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-26 12:00 -0700
Re: Resource revocation stephenXXX@mpeforth.com (Stephen Pelc) - 2013-07-27 16:49 +0000
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-28 18:31 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-28 15:51 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-28 20:12 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-28 18:35 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-29 00:10 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 00:23 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-29 01:05 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 12:07 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-30 01:11 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 15:20 -0700
Re: Resource revocation Rob Gaddi <rgaddi@technologyhighland.invalid> - 2013-07-29 15:42 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 16:41 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-30 08:51 +0300
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 09:09 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 01:30 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 10:04 +0100
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-30 02:55 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 07:12 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 16:59 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 13:17 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-30 10:12 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-30 18:48 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 20:18 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-31 09:27 +0300
Re: Resource revocation [long] Don Y <this@isnotme.com> - 2013-07-31 00:47 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-30 02:50 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-30 13:22 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 07:24 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 01:17 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-29 19:28 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-07-29 11:40 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 11:44 -0700
Re: Resource revocation Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-07-29 20:56 +0100
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 13:16 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-30 00:08 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-30 23:41 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-31 00:58 -0700
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-31 10:18 -0700
Re: Resource revocation George Neuner <gneuner2@comcast.net> - 2013-08-02 06:19 -0400
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-08-03 02:26 -0400
Re: Resource revocation Paul Rubin <no.email@nospam.invalid> - 2013-07-28 19:31 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-29 00:44 -0700
Re: Resource revocation Richard Damon <Richard@Damon-Family.org> - 2013-07-25 22:42 -0400
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-25 22:12 -0700
Re: Resource revocation "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2013-07-31 13:41 +0200
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-31 07:51 -0700
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-31 08:07 -0700
Re: Resource revocation Anders.Montonen@kapsi.spam.stop.fi.invalid - 2013-07-31 15:55 +0000
Re: Resource revocation Don Y <this@isnotme.com> - 2013-07-31 10:18 -0700
Re: Resource revocation "Boudewijn Dijkstra" <sp4mtr4p.boudewijn@indes.com> - 2013-08-01 14:42 +0200
Re: Resource revocation Don Y <this@isnotme.com> - 2013-08-01 14:34 -0700
Re: Resource revocation upsidedown@downunder.com - 2013-08-02 09:08 +0300
Re: Resource revocation Don Y <this@isnotme.com> - 2013-08-02 07:26 -0700
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