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[Der Herr Hofrat <der.herr@hofr.at>]

>From owner-rtl Fri May 18 01:34:55 2001
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Date: Fri, 18 May 2001 09:32:19 +0200
From: =?iso-8859-1?Q?S=E9bastien?= GAUME <sgaume@b2i-toulouse.com>
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To: rtl@rtlinux.org, rtl@fsmlabs.com
Subject: gethrtime
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Hello,

I have a question about the "gethrtime" function.

This function, as said in the man pages, returns the time in
nanoseconds. Which means that it converts the clock ticks into
nanoseconds. As the clock period is unfortunately not an integer
multiple of nanoseconds, the conversion will entail a rounding or
truncation on the last digit.

Thus, when you ask a task to be periodic, you give the period in
nanoseconds and I suppose this value is converted into clock ticks,
which entails a rouding. Suppose a task is periodic, running in the
oneshot mode. Periodically, the next wake up date is calculated in clock
units. Because the period in clock unit is not equal to the period in
nanoseconds, a drift should be seen, especially after a large number of
periods.

In fact, after having done this test, I did not see such a drift. Do not
think I am disapointed, I'm not ! I would like to know wether I am wrong
in my assumptions or not, and if not, how the gethrtime function manages
not to create a drift.

Thank you

Sebastien