From: dewar@gnat.com
Subject: Re: delay until and GNAT - expand
Date: 1999/05/08
Date: 1999-05-08T00:00:00+00:00 [thread overview]
Message-ID: <7h1e10$drg$1@nnrp1.deja.com> (raw)
In-Reply-To: rracine.12.00086B05@draper.com
In article <rracine.12.00086B05@draper.com>,
rracine@draper.com (Roger Racine) wrote:
> The implementation of "delay", given today's processor speeds, is pretty good.
> I have recently single stepped my way (in assembly) through it, and while I
> did not count the instructions, it had to be on the order of 100 instructions.
>
> So, given a good real-time operating system and a reasonably fast processor, a
> reasonable upper limit would probably be close to 1 microsecond (conservative
> estimate).
>
> I am surprised GNAT documentation does not have this, except that the number
> will be different for every underlying OS.
>
> Roger Racine
This is a highly misleading figure. The completion of a delay, in the sense
that we are talking about, requires a preemptive context switch. To expect
this to happen in 1 microsecond when running over an operating system like
Unix, or even over a light real time executive is wildly optimistic.
I am not sure what you are measuring, but it is quite wrong. We don't document
upper limits for such things in the GNAT manual, because it is impractical to
do so in almost all operating systems contexts, since we depend on the
underlying OS, and this information is not available for the OS.
Robert Dewar
Ada Core Technologies
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
next prev parent reply other threads:[~1999-05-08 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 [this message]
1999-05-10 0:00 ` Roger Racine
1999-05-10 0:00 ` Joel Sherrill
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison
1999-05-11 0:00 ` isaac buchwald
1999-05-11 0:00 ` dennison
1999-05-12 0:00 ` Robert Dewar
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
1999-05-10 0:00 ` delay until and GNAT - expand 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
[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
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox