Re: [offtopic] Re: 2.2.2: 2 thumbs up from lm

Neil Conway (nconway.list@ukaea.org.uk)
Fri, 26 Feb 1999 11:56:14 +0000


Albert D. Cahalan wrote:
>
> Neil Conway writes:
> > Richard B. Johnson wrote:
>
> >> Now, where does it say anything about "bounded latencies". By what
> >> authority? Since I defined realtime, I would like to know how
> >> an additional definition got appended to destroy the concept.
> >
> > I think we're on different wavelengths: "realtime" does have a meaning
> > outside any definition you choose for it. I'm used to a particular
> > definition for "realtime", and of course if we use yours then my
> > comments are meaningless.
>
> We must use his if you won't post yours.

I thought I did - "bounded latency" is the heart of it. Maybe I'm the
one that's out of step with the rest of the world ;-))

This is now rather a long way off topic, so I think I'll be dropping it.

>
> > But how can you promise the customer that your system will respond to
> > events while they are current if you DON'T control the latency?
>
> You must be building your own motherboards, right? You can not make
> honest promises with hardware that might frequently retry to hide
> error conditions from the OS. The BIOS could even use a system management
> mode to steal cycles.
>
> I think this whole argument is silly. The goal should be "improve".
> There is no perfection. Think in terms of histograms with infinitely
> long tails that need to be squished as flat as possible. Every bit
> of improvement is useful -- maybe Linux goes from 5000 ruined CDs/year
> to 4352 ruined CDs/year. Good.

Lest I mislead anyone about my meaning: I personally would not attempt
"real" aka "hard" aka "realtime" realtime on a vanilla Linux box (at
least not if I cared about the outcome ;-)). I was addressing a generic
RT point, and that's why I'm going to drop it...

Neil

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