From: dennison@telepath.com
Subject: Re: delay until and GNAT - expand
Date: 1999/05/12
Date: 1999-05-12T00:00:00+00:00 [thread overview]
Message-ID: <7hc4vu$7k9$1@nnrp1.deja.com> (raw)
In-Reply-To: rracine.14.00 <rracine.17.0007DA28@draper.com
In article <rracine.17.0007DA28@draper.com>,
rracine@draper.com (Roger Racine) wrote:
> In article <7h9nal$9dr$1@nnrp1.deja.com> Robert Dewar
<robert_dewar@my-dejanews.com> writes:
> >In article <7h9j77$61l$1@nnrp1.deja.com>,
> > dennison@telepath.com wrote:
> >> 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
> We are obviously talking about different metrics. The original
message (as
> expanded) asked about the "delay 0.0" case, not a positive value. So
your
> clock interrupt goes away, as does the idle task execution (which is
all of
> your measured time).
>
> All that is needed (not necessarily all that is done) is a check for
positive,
> and, if not, a call to "sched_yield" (POSIX interface), which puts the
task at
> the end of the ready queue and performs a context switch.
Well, it appears that Windview reports the work of a context switch in
the context of the currently running task (yikes, what a sentence!). So
I think it can be reasonably well assumed that the entire period of time
I reported for the "idle" task is being taken up by an attempt to change
the task context from that of the idle task to that of the newly-readied
60hz task. What we *don't* know is how much, if any, task switch
overhead occurrs after Windview reports the context switch. But I think
we can resonably take 11 micros as a lower bound for the amount of time
it takes to perform a context switch in vxWorks (on a PII-400, with the
cache invalidate instruction disabled, etc, etc.).
--
T.E.D.
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next prev parent reply other threads:[~1999-05-12 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
1999-05-10 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
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 ` Tarjei Tj�stheim Jensen
1999-05-11 0:00 ` David Brown
1999-05-11 0:00 ` Robert Dewar
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
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 [this message]
1999-05-12 0:00 ` Roger Racine
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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