BOUNCE rtl@rtlinux.org: Approval required: (fwd)

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

>From owner-rtl Sun May 20 03:13:00 2001
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Date: Sun, 20 May 2001 13:07:59 +0400
From: Michael Barabanov <baraban@fsmlabs.com>
To: S?bastien GAUME <sgaume@b2i-toulouse.com>
Cc: rtl@rtlinux.org
Subject: Re: [rtl] gethrtime
Message-ID: <20010520130758.A12478@fsmlabs.com>
References: <3B04D002.1CB12216@b2i-toulouse.com>
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In-Reply-To: <3B04D002.1CB12216@b2i-toulouse.com>; from sgaume@b2i-toulouse.com on Fri, May 18, 2001 at 09:32:19AM +0200
Organization: FSMLabs

Internally all calculations are performed in nanoseconds, so there's no
drift.

Michael.

S?bastien GAUME (sgaume@b2i-toulouse.com) wrote:
> 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
> 
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