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: <7h9j77$61l$1@nnrp1.deja.com> (raw)
In-Reply-To: 7h830a$e4$1@nnrp1.deja.com
In article <7h830a$e4$1@nnrp1.deja.com>,
Robert Dewar <robert_dewar@my-dejanews.com> wrote:
> In article <rracine.14.0008C889@draper.com>,
> rracine@draper.com (Roger Racine) wrote:
>
> > I just did a little checking on Wind Rivers' web site, and I
> > found, for the "MV167C" Motorola 68K board (they do not
> > specify which chip or speed in the web page), "context
> > switching requires only 3.8 microseconds". Not exactly 1
> > microsecond, but I got the order of magnitude correct.
>
> I would say this shows you likely got the order of magnitude
> one off. Implementation of a delay involves more than a simple
> context switch. As I say, we will measure the WR VXW speed
> on a fast machine and see what we get. I am willing to bet
> you are way off in the one microsecond estimate. Yes, it would
> be nice if it were only one microsecond, but I am afraid we will
> not see it. Anyway, let's wait till we can get some data here.
I'm not sure *exactly* what you were hoping to measure. However, I
happen to have an old Windview log here of a program that uses "delay
until" for scheduling. It was taken on a PII-400 PC.
What I am seeing is that "interrupt 0", the clock interrupt, takes about
11 micro seconds. Then the slighly misnamed "idle" task continues to
execute for about 11 micros. Then my Ada task begins. Where in there my
Ada code starts executing again rather than vxWorks system calls, I
cannot tell with Windview. But all totaled that is about 22 microseconds
from the clock tick at which the delay expired to the time my Ada task's
context was switched to.
Note that this is with the Pentium II fix that is in Tornado II (The
fix prevents a rather bogous and very time consuming cache
invalidation, as I understand it). Before the fix we were seeing times
of 19 and 50 micros for a total of about 70 respectively.
--
T.E.D.
--== Sent via Deja.com http://www.deja.com/ ==--
---Share what you know. Learn what you don't.---
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 ` David C. Hoos, Sr.
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 ` 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 ` Robert Dewar
1999-05-11 0:00 ` David Brown
1999-05-10 0:00 ` delay until and GNAT - expand 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 ` Roger Racine
1999-05-11 0:00 ` Robert Dewar
1999-05-11 0:00 ` dennison [this message]
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
1999-05-11 0:00 ` delay until and GNAT - expand Roger Racine
[not found] ` <rracine.14.00 <rracine.15.000968A0@draper.com>
1999-05-11 0:00 ` Robert Dewar
[not found] ` <rracine.14.00 <rracine.17.0007DA28@draper.com>
1999-05-12 0:00 ` dennison
1999-05-12 0:00 ` Roger Racine
1999-05-06 0:00 ` delay until and GNAT 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