From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: accuracy
Date: Sun, 11 Mar 2007 16:50:14 +0100
Date: 2007-03-11T16:49:55+01:00 [thread overview]
Message-ID: <s65hfcfotme5$.2sbaf7cqlc45.dlg@40tude.net> (raw)
In-Reply-To: 45F4140F.5000405@obry.net
On Sun, 11 Mar 2007 15:37:03 +0100, Pascal Obry wrote:
> By checking a base time against GetSystemTimeAsFileTime to avoid using
> another thread. This way you have the accuracy of the performance
> counter and can adjust the current time if needed (DST, manual changes...).
I.e. it does this only once. The potential problems with this is that:
1. The accuracy of GetSystemTimeAsFileTime is very low.
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.
4. It is unclear if the time source of the system time is derived from the
performance counter. If not, they will divergent.
A thread is used to accumulate measurements of performance counters and
system time readings to get a best possible estimation out of it.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2007-03-11 15:50 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 ` Dmitry A. Kazakov [this message]
2007-03-11 17:38 ` accuracy Pascal Obry
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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