From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Subject: Re: Ada.Execution_Time
Date: Thu, 30 Dec 2010 21:23:25 +0200
Date: 2010-12-30T21:23:25+02:00 [thread overview]
Message-ID: <8o44hfFsarU1@mid.individual.net> (raw)
In-Reply-To: <aooml6t0ezs4.4srxtfm9z00r.dlg@40tude.net>
Dmitry A. Kazakov wrote:
> On Wed, 29 Dec 2010 14:48:20 +0200, Niklas Holsti wrote:
>
>> Dmitry has agreed with some of my statements on this point, for example:
>>
>> - A task cannot accumulate execution time at a higher rate than real
>> time. For example, in one real-time second the CPU_Time of a task cannot
>> increase by more than one second.
>
> Hold on, that is only true if a certain model of CPU_Time measurement used.
> There are many potential models. The one we discussed was the model A:
>
> Model A. Get an RTC reading upon activation. Each time CPU_Time is
> requested by Clock get another RTC reading, build the difference, add the
> accumulator to the result. Upon task deactivation, get the difference and
> update the accumulator.
[ cut ]
> Note that in either model the counter readings are rounded. Windows rounds
> toward zero, which why you never get more load than 100%. But it is
> thinkable and expectable that some systems would round away from zero or to
> the nearest bound.
The RTEMS CPU Usage Statistics function in fact rounds up: "RTEMS keeps
track of how many clock ticks have occurred which [should be "while"]
the task being switched out has been executing. If the task has been
running less than 1 clock tick, then for the purposes of the statistics,
it is assumed to have executed 1 clock tick. This results in some
inaccuracy but the alternative is for the task to have appeared to
execute 0 clock ticks." (Quoted from
http://www.rtems.org/onlinedocs/releases/rtemsdocs-4.9.4/share/rtems/pdf/c_user.pdf,
page 285).
I think that rounding up may indeed be better (safer) for real-time
scheduling and monitoring purposes. But of course this is just changing
the direction of the inaccuracy, the principle stands.
--
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
. @ .
next prev parent reply other threads:[~2010-12-30 19:23 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-12 4:19 Ada.Execution_Time BrianG
2010-12-12 5:27 ` Ada.Execution_Time Jeffrey Carter
2010-12-12 16:56 ` Ada.Execution_Time Jeffrey Carter
2010-12-12 21:59 ` Ada.Execution_Time BrianG
2010-12-12 22:08 ` Ada.Execution_Time BrianG
2010-12-13 9:28 ` Ada.Execution_Time Georg Bauhaus
2010-12-13 22:25 ` Ada.Execution_Time Randy Brukardt
2010-12-13 22:42 ` Ada.Execution_Time J-P. Rosen
2010-12-14 3:31 ` Ada.Execution_Time Jeffrey Carter
2010-12-14 15:42 ` Ada.Execution_Time Robert A Duff
2010-12-14 16:17 ` Ada.Execution_Time Jeffrey Carter
2010-12-14 19:10 ` Ada.Execution_Time Warren
2010-12-14 20:36 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-14 20:48 ` Ada.Execution_Time Jeffrey Carter
2010-12-14 8:17 ` Ada.Execution_Time Vinzent Hoefler
2010-12-14 15:51 ` Ada.Execution_Time Adam Beneschan
2010-12-14 15:53 ` Ada.Execution_Time Robert A Duff
2010-12-14 17:17 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-14 17:45 ` Ada.Execution_Time Robert A Duff
2010-12-14 18:23 ` Ada.Execution_Time Adam Beneschan
2010-12-14 21:02 ` Ada.Execution_Time Randy Brukardt
2010-12-15 22:52 ` Ada.Execution_Time Keith Thompson
2010-12-15 23:14 ` Ada.Execution_Time Adam Beneschan
2010-12-17 0:44 ` Ada.Execution_Time Randy Brukardt
2010-12-17 17:54 ` Ada.Execution_Time Warren
2010-12-20 21:28 ` Ada.Execution_Time Keith Thompson
2010-12-21 3:23 ` Ada.Execution_Time Robert A Duff
2010-12-21 8:04 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-21 17:19 ` Ada.Execution_Time Robert A Duff
2010-12-21 17:43 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-14 19:43 ` Ada.Execution_Time anon
2010-12-14 20:09 ` Ada.Execution_Time Adam Beneschan
2010-12-15 0:16 ` Ada.Execution_Time BrianG
2010-12-15 19:17 ` Ada.Execution_Time jpwoodruff
2010-12-15 21:42 ` Ada.Execution_Time Pascal Obry
2010-12-16 3:54 ` Ada.Execution_Time jpwoodruff
2010-12-17 7:11 ` Ada.Execution_Time Stephen Leake
2010-12-15 21:40 ` Ada.Execution_Time Simon Wright
2010-12-15 23:40 ` Ada.Execution_Time BrianG
2010-12-15 22:05 ` Ada.Execution_Time Randy Brukardt
2010-12-16 1:14 ` Ada.Execution_Time BrianG
2010-12-16 5:46 ` Ada.Execution_Time Jeffrey Carter
2010-12-16 16:13 ` Ada.Execution_Time BrianG
2010-12-16 11:37 ` Ada.Execution_Time Simon Wright
2010-12-16 17:24 ` Ada.Execution_Time BrianG
2010-12-16 17:45 ` Ada.Execution_Time Adam Beneschan
2010-12-16 21:13 ` Ada.Execution_Time Jeffrey Carter
2010-12-17 0:35 ` New AdaIC site (was: Ada.Execution_Time) Randy Brukardt
2010-12-16 13:08 ` Ada.Execution_Time Peter C. Chapin
2010-12-16 17:32 ` Ada.Execution_Time BrianG
2010-12-16 18:17 ` Ada.Execution_Time Jeffrey Carter
2010-12-16 8:45 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-16 16:49 ` Ada.Execution_Time BrianG
2010-12-16 17:52 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-17 8:49 ` Ada.Execution_Time Niklas Holsti
2010-12-17 9:32 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-17 11:50 ` Ada.Execution_Time Niklas Holsti
2010-12-17 13:10 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-18 21:20 ` Ada.Execution_Time Niklas Holsti
2010-12-19 9:57 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-25 11:31 ` Ada.Execution_Time Niklas Holsti
2010-12-26 10:25 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-27 12:44 ` Ada.Execution_Time Niklas Holsti
2010-12-27 15:28 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-27 20:11 ` Ada.Execution_Time Niklas Holsti
2010-12-27 21:34 ` Ada.Execution_Time Simon Wright
2010-12-28 10:01 ` Ada.Execution_Time Niklas Holsti
2010-12-28 14:17 ` Ada.Execution_Time Simon Wright
2010-12-27 21:53 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-28 14:14 ` Ada.Execution_Time Simon Wright
2010-12-28 15:08 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-28 16:18 ` Ada.Execution_Time Simon Wright
2010-12-28 16:34 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-31 0:40 ` Ada.Execution_Time BrianG
2010-12-31 9:09 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-28 14:46 ` Ada.Execution_Time Niklas Holsti
2010-12-28 15:42 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-28 16:27 ` Ada.Execution_Time (see below)
2010-12-28 16:55 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-28 19:41 ` Ada.Execution_Time (see below)
2010-12-28 20:03 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-28 22:39 ` Ada.Execution_Time Simon Wright
2010-12-29 9:07 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-27 17:24 ` Ada.Execution_Time Robert A Duff
2010-12-27 22:02 ` Ada.Execution_Time Randy Brukardt
2010-12-27 22:43 ` Ada.Execution_Time Robert A Duff
2010-12-27 22:11 ` Ada.Execution_Time Randy Brukardt
2010-12-29 12:48 ` Ada.Execution_Time Niklas Holsti
2010-12-29 14:30 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-29 16:19 ` Ada.Execution_Time (see below)
2010-12-29 16:51 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-29 19:57 ` Ada.Execution_Time (see below)
2010-12-29 21:20 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-30 5:13 ` Ada.Execution_Time Randy Brukardt
2010-12-30 13:37 ` Ada.Execution_Time Niklas Holsti
2010-12-29 20:32 ` Ada.Execution_Time Niklas Holsti
2010-12-29 21:21 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-30 13:34 ` Ada.Execution_Time Niklas Holsti
2010-12-30 19:23 ` Niklas Holsti [this message]
2010-12-30 5:06 ` Ada.Execution_Time Randy Brukardt
2010-12-30 23:49 ` Ada.Execution_Time Niklas Holsti
2010-12-31 23:34 ` Ada.Execution_Time Randy Brukardt
2011-01-01 13:52 ` Ada.Execution_Time Niklas Holsti
2011-01-01 14:42 ` Ada.Execution_Time Simon Wright
2011-01-01 16:01 ` Ada.Execution_Time Simon Wright
2011-01-01 19:18 ` Ada.Execution_Time Niklas Holsti
2011-01-03 21:27 ` Ada.Execution_Time Randy Brukardt
2011-01-06 22:55 ` Ada.Execution_Time Niklas Holsti
2011-01-07 6:25 ` Ada.Execution_Time Randy Brukardt
2011-01-01 15:54 ` Ada.Execution_Time Simon Wright
2011-01-03 21:33 ` Ada.Execution_Time Randy Brukardt
2011-01-05 15:55 ` Ada.Execution_Time Brad Moore
2010-12-17 8:59 ` Ada.Execution_Time anon
2010-12-19 3:07 ` Ada.Execution_Time BrianG
2010-12-19 4:01 ` Ada.Execution_Time Vinzent Hoefler
2010-12-19 11:00 ` Ada.Execution_Time Niklas Holsti
2010-12-21 0:37 ` Ada.Execution_Time Randy Brukardt
2010-12-21 1:20 ` Ada.Execution_Time Jeffrey Carter
2010-12-19 12:27 ` Ada.Execution_Time Dmitry A. Kazakov
2010-12-21 0:32 ` Ada.Execution_Time Randy Brukardt
2010-12-19 22:54 ` Ada.Execution_Time anon
2010-12-20 3:14 ` Ada.Execution_Time BrianG
2010-12-22 14:30 ` Ada.Execution_Time anon
2010-12-22 20:09 ` Ada.Execution_Time BrianG
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox