From: Philippe Gerum <rpm@xenomai.org>
To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: Xenomai core <Xenomai-core@domain.hid>
Subject: Re: [Xenomai-core] Clock drift.
Date: Wed, 14 Jan 2009 15:06:08 +0100 [thread overview]
Message-ID: <496DF150.8050606@domain.hid> (raw)
In-Reply-To: <496DEFEA.5000709@domain.hid>
Gilles Chanteperdrix wrote:
> 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.
>
Yes it does. But this value is used by Xenomai code.
>> - 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?
>
Time to involve printk() in this battle.
--
Philippe.
next prev parent reply other threads:[~2009-01-14 14:06 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-14 13:39 [Xenomai-core] Clock drift Gilles Chanteperdrix
2009-01-14 13:50 ` Jan Kiszka
2009-01-14 13:55 ` Gilles Chanteperdrix
2009-01-14 13:53 ` Philippe Gerum
2009-01-14 14:00 ` Gilles Chanteperdrix
2009-01-14 14:06 ` Philippe Gerum [this message]
2009-01-15 13:15 ` Gilles Chanteperdrix
2009-01-15 13:30 ` Gilles Chanteperdrix
2009-01-15 13:50 ` Gilles Chanteperdrix
2009-01-15 13:32 ` Philippe Gerum
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