From: dennison@telepath.com
Subject: Re: delay until and GNAT - expand
Date: 1999/05/11
Date: 1999-05-11T00:00:00+00:00 [thread overview]
Message-ID: <7h9f1d$2q3$1@nnrp1.deja.com> (raw)
In-Reply-To: 7h82qm$bq$1@nnrp1.deja.com
In article <7h82qm$bq$1@nnrp1.deja.com>,
Robert Dewar <robert_dewar@my-dejanews.com> wrote:
> In article <rracine.13.0007AF82@draper.com>,
> rracine@draper.com (Roger Racine) wrote:
>
> > Note that I said, "given a good real-time operating system".
> > That does not include any form of Unix (with the possible
> > exception of LynxOS and any other real-time versions; I have
> > not looked at their documentation recently).
>
> I do not believe that the estimate of one microsecond latency
> for a delay is anywhere near achievable for any of the typical
> operating systems or executives that are used today for typical
> real time systems. Roger, do some measurements if you want to
> challenge this. Most certainly Lynx, which I know well cannot
> begin to achieve this performance. Modern RISC machines have
> a lot of state to save and restore, and of course context
> switches typically involve cache switch overs which waste
> even more time.
>
> Certainly in all measurements we have done on GNAT, the time
> spent in pthreads calls completely overwhelms all the time
> in the GNAT runtime itself.
>
> Probably the best case is to run VxWorks on a really fast
> machine, I will see if I can get some measurements for this.
If your "really fast machine" is a PII PC, beware. There's a bug in
vxWorks that actually causes it to take much *longer* to switch tasks on
a PII than on a Pentium. We have a patch for it here, which supposedly
is in Tornado II.
I'll see if I can't get some rough numbers from Windview...
--
T.E.D.
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next prev parent reply other threads:[~1999-05-11 0:00 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-05-05 0:00 delay until and GNAT isaac buchwald
1999-05-05 0:00 ` dennison
1999-05-06 0:00 ` Buz Cory
1999-05-06 0:00 ` Robert Dewar
1999-05-06 0:00 ` delay until and GNAT - expand isaac buchwald
1999-05-07 0:00 ` Roger Racine
1999-05-08 0:00 ` dewar
1999-05-10 0:00 ` Roger Racine
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison
1999-05-11 0:00 ` Robert Dewar
1999-05-12 0:00 ` delay until and GNAT - where to get the info isaac buchwald
1999-05-12 0:00 ` Robert Dewar
1999-05-10 0:00 ` delay until and GNAT - expand Roger Racine
1999-05-10 0:00 ` Joel Sherrill
1999-05-11 0:00 ` isaac buchwald
1999-05-11 0:00 ` dennison
1999-05-12 0:00 ` Robert Dewar
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison [this message]
1999-05-10 0:00 ` Context switching (was: delay until and GNAT) Nick Roberts
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` Tarjei Tj�stheim Jensen
1999-05-11 0:00 ` David Brown
1999-05-11 0:00 ` Robert Dewar
[not found] ` <rracine.14.00 <rracine.15.000968A0@draper.com>
1999-05-11 0:00 ` delay until and GNAT - expand Robert Dewar
1999-05-11 0:00 ` Roger Racine
1999-05-12 0:00 ` Roger Racine
[not found] ` <rracine.14.00 <rracine.17.0007DA28@draper.com>
1999-05-12 0:00 ` dennison
1999-05-05 0:00 ` delay until and GNAT David C. Hoos, Sr.
1999-05-06 0:00 ` Roger Racine
1999-05-10 0:00 ` Nick Roberts
1999-05-11 0:00 ` Context Switching Nick Roberts
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` Robert I. Eachus
1999-05-12 0:00 ` dennison
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