From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: *
X-Spam-Status: No, score=1.3 required=5.0 tests=BAYES_00,INVALID_MSGID,
	MSGID_RANDY autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,71b19e01eae3a390
X-Google-Attributes: gid103376,public
From: dennison@telepath.com
Subject: Re: delay until and GNAT - expand
Date: 1999/05/11
Message-ID: <7h9f1d$2q3$1@nnrp1.deja.com>#1/1
X-Deja-AN: 476582303
References: <m3_X2.48$6o.1372369@news.siol.net>
 <7gpukr$s82$1@nnrp1.dejanews.com> <7grkbb$cee$1@nnrp1.deja.com>
 <7grvka$lc5$1@nnrp1.deja.com> <k_kY2.71$6o.2036023@news.siol.net>
 <rracine.12.00086B05@draper.com> <7h1e10$drg$1@nnrp1.deja.com>
 <rracine.13.0007AF82@draper.com> <7h82qm$bq$1@nnrp1.deja.com>
X-Http-Proxy: 1.0 x30.deja.com:80 (Squid/1.1.22) for client 204.48.27.130
Organization: Deja.com - Share what you know. Learn what you don't.
X-Article-Creation-Date: Tue May 11 14:32:12 1999 GMT
Newsgroups: comp.lang.ada
X-Http-User-Agent: Mozilla/4.5 [en] (WinNT; I)
Date: 1999-05-11T00:00:00+00:00
List-Id: <comp.lang.ada>

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.


--== Sent via Deja.com http://www.deja.com/ ==--
---Share what you know. Learn what you don't.---