From: Pascal Obry <pascal@obry.net>
To: mailbox@dmitry-kazakov.de
Subject: Re: accuracy
Date: Sun, 11 Mar 2007 18:38:58 +0100
Date: 2007-03-11T18:39:00+01:00 [thread overview]
Message-ID: <45F43EB2.2000008@obry.net> (raw)
In-Reply-To: <s65hfcfotme5$.2sbaf7cqlc45.dlg@40tude.net>
Dmitry,
> I.e. it does this only once. The potential problems with this is that:
No it is not does once but each time a clock is requested for adjustment
if needed.
> 1. The accuracy of GetSystemTimeAsFileTime is very low.
Yes but it is not used for final clock returned value.
> 2. All system calls have non-zero latencies.
>
> 3. There is a chance that the thread will be preempted between querying the
> counter and calling to a system time query, which would additionally
> increase the experienced latency up to milliseconds.
During initialization of the runtime the performance counter and the
system time are read until this is done during a minimal amount of time.
This gives the base reference for the performance counter and the os time.
> 4. It is unclear if the time source of the system time is derived from the
> performance counter. If not, they will divergent.
No it is no.
If this is still unclear have a look at the corresponding implementation
in the GNAT sources.
Pascal.
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next prev parent reply other threads:[~2007-03-11 17:38 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-29 11:57 Does Ada tasking profit from multi-core cpus? Gerd
2007-01-29 12:04 ` Georg Bauhaus
2007-01-30 13:55 ` Gerd
2007-02-09 10:18 ` karl
2007-02-09 11:03 ` Stefan Lucks
2007-02-09 11:35 ` Ludovic Brenta
2007-03-04 17:54 ` jpluto
2007-03-05 10:08 ` Ludovic Brenta
2007-03-05 13:12 ` Dmitry A. Kazakov
2007-03-06 5:33 ` tmoran
2007-03-06 8:44 ` Dmitry A. Kazakov
2007-03-07 7:52 ` tmoran
2007-03-07 9:31 ` tmoran
2007-03-06 9:40 ` Colin Paul Gloster
2007-03-06 12:47 ` Jeffrey Creem
2007-03-06 14:44 ` Georg Bauhaus
2007-03-06 16:53 ` Dr. Adrian Wrigley
2007-03-06 18:58 ` tmoran
2007-03-07 10:11 ` Colin Paul Gloster
2007-03-07 18:47 ` tmoran
2007-03-06 18:51 ` Jeffrey R. Carter
2007-03-16 14:29 ` Arguments for single-mutex-exclusion on protected types (Was: Does Ada tasking profit from multi-core cpus?) Jacob Sparre Andersen
2007-03-17 5:26 ` Jeffrey R. Carter
2007-03-17 17:22 ` Robert A Duff
2007-03-17 17:52 ` Jeffrey R. Carter
2007-03-17 23:06 ` Randy Brukardt
2007-03-18 17:57 ` Robert A Duff
2007-03-19 21:49 ` Randy Brukardt
2007-03-20 0:55 ` Jeffrey R. Carter
2007-03-20 1:36 ` Randy Brukardt
2007-03-20 16:32 ` Jeffrey R. Carter
2007-03-20 17:51 ` Randy Brukardt
2007-03-21 0:10 ` Jeffrey R. Carter
2007-03-26 23:38 ` Robert A Duff
2007-03-26 23:24 ` Robert A Duff
2007-03-17 10:25 ` Dmitry A. Kazakov
2007-03-18 17:15 ` Arguments for single-mutex-exclusion on protected types Jacob Sparre Andersen
2007-03-18 18:50 ` Dmitry A. Kazakov
2007-03-20 12:38 ` Florian Weimer
2007-03-07 3:58 ` Does Ada tasking profit from multi-core cpus? Steve
2007-03-07 8:39 ` Dmitry A. Kazakov
2007-03-08 5:21 ` Randy Brukardt
2007-03-08 10:15 ` Dmitry A. Kazakov
2007-03-08 21:18 ` accuracy (was: Does Ada tasking profit from multi-core cpus?) Björn Persson
2007-03-09 8:33 ` accuracy Dmitry A. Kazakov
2007-03-10 1:39 ` accuracy Randy Brukardt
2007-03-10 9:11 ` accuracy Dmitry A. Kazakov
2007-03-11 3:03 ` accuracy Randy Brukardt
2007-03-11 5:21 ` accuracy tmoran
2007-03-11 8:52 ` accuracy Dmitry A. Kazakov
2007-03-11 13:57 ` accuracy Pascal Obry
2007-03-11 14:16 ` accuracy Dmitry A. Kazakov
2007-03-11 14:37 ` accuracy Pascal Obry
2007-03-11 15:50 ` accuracy Dmitry A. Kazakov
2007-03-11 17:38 ` Pascal Obry [this message]
2007-03-11 18:48 ` accuracy Dmitry A. Kazakov
2007-03-12 20:20 ` accuracy Randy Brukardt
2007-03-13 9:33 ` accuracy Dmitry A. Kazakov
2007-03-10 14:53 ` accuracy Stephen Leake
2007-03-10 18:36 ` accuracy Cesar Rabak
2007-03-05 18:46 ` Does Ada tasking profit from multi-core cpus? Jeffrey R. Carter
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