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=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: a07f3367d7,cae92f92d6a1d4b1
X-Google-Attributes: gida07f3367d7,public,usenet
X-Google-NewGroupId: yes
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!news4.google.com!feeder.news-service.com!texta.sil.at!newsfeed01.chello.at!newsfeed.arcor.de!newsspool4.arcor-online.net!news.arcor.de.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Ada.Execution_Time
Newsgroups: comp.lang.ada
User-Agent: 40tude_Dialog/2.0.15.1
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Reply-To: mailbox@dmitry-kazakov.de
Organization: cbb software GmbH
References: <ie1ih9$d02$1@news.eternal-september.org>
 <ie2v2k$aps$1@tornado.tornevall.net> <ie3gjn$oj$1@news.eternal-september.org>
 <4d05e737$0$6980$9b4e6d93@newsspool4.arcor-online.net>
 <ie91co$cko$1@news.eternal-september.org> <iebe2t$eua$1@munin.nbi.dk>
 <1wmsukf0wglz3$.odnzonrpayly.dlg@40tude.net>
 <iedfud$ul1$1@news.eternal-september.org>
 <6n1c5myuf2uz$.10jl3ln7il3aq.dlg@40tude.net>
 <8n0mgnFv2sU1@mid.individual.net>
 <1n3o55xjdjr9t.1u33kb75y2jfl$.dlg@40tude.net>
 <8n1142Fto2U1@mid.individual.net>
 <1o5cbm4b1l20d$.19winbma6k5qw.dlg@40tude.net>
 <8n4mskF7mmU1@mid.individual.net>
 <bboyk178uyce.1jx52xgjoblk1$.dlg@40tude.net>
 <8nm30fF7r9U1@mid.individual.net> <ifb2ts$l0m$1@munin.nbi.dk>
 <8o0p0lF94rU1@mid.individual.net> <aooml6t0ezs4.4srxtfm9z00r.dlg@40tude.net>
 <8o1k6vFbd7U1@mid.individual.net>
Date: Wed, 29 Dec 2010 22:21:07 +0100
Message-ID: <1k7xzi2uradva$.atlfxh9h94qb$.dlg@40tude.net>
NNTP-Posting-Date: 29 Dec 2010 22:21:07 CET
NNTP-Posting-Host: e9f01959.newsspool2.arcor-online.net
X-Trace: 
 DXC=_2N23ooO27eeoCI^f\Y]EaA9EHlD;3Ycb4Fo<]lROoRa8kF<OcfhCOk2D1f2XPQoT`[6LHn;2LCVn[<mhadbfdUkQXHj<G9fk;c:k\BL^>jQjh
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news2.google.com comp.lang.ada:17210
Date: 2010-12-29T22:21:07+01:00
List-Id: <comp.lang.ada>

On Wed, 29 Dec 2010 22:32:30 +0200, Niklas Holsti wrote:

> Dmitry A. Kazakov wrote:
>> 
>> Model C. Asynchronous task monitoring process
> 
> That sounds weird. Please clarify.

For example, in the kernel you have a timer interrupt each n us. Within the
handler you get the current TCB and increment the CPU usage counter there
by 1. CPU_Time returned by Clock yields Counter * n us. This is a quite
lightweight schema, which can be used for small and real-time systems. The
overhead is constant.

> Again, it holds within the accuracy of the measurement method and the 
> time source, which is all that one can expect.

The error is not bound. Only its deviation is bound, e.g. x seconds per
second of measurement.

>> Time as physical concept is not absolute. There is no *the* real time, but
>> many real times and even more unreal ones.
> 
> When RM D.14(11/2) defines "the execution time of a given task" as "the 
> time spent by the system executing that task", the only reasonable 
> reading of the second "time" is as the common-sense physical time, as 
> measured by your wrist-watch or by some more precise clock.

Which physical experiment could prove or disprove that a given
implementation is in agreement with this definition? Execution time is not
observable.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de