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Date: Wed, 14 Jan 2009 14:00:10 +0000
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-core] Clock drift.
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Philippe Gerum wrote:
> Gilles Chanteperdrix wrote:
>> Hi,
>>
>> I run clocktest on a system here, not running NTP, using
>> CONFIG_GENERIC_CLOCKEVENT, with a systematic drift of 3us/s. How can
>> this happen? Does it come from the error due to the multiply and shift
>> used for tsc to/from ns conversions ?
>>
> 
> - ipipe_request_tickdev() returning a timer freq we don't like?

Well, I would expect ipipe_request_tickdev() to return the same
frequency as the one used by Linux.

> - does using your generic arith ops instead of the arch-dependent fast ops help?

Linux itself uses a multiply and shift strategy, so maybe the
computation of the multiply and shift factors done by Xenomai does not
find the same result as the one used by Linux?

-- 
                                                 Gilles.