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Date: Fri, 04 Apr 2008 10:23:24 +0200
From: Sebastian Smolorz <smolorz@domain.hid>
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Subject: Re: [Xenomai-core] latencys drifting into negative (Xenomai
	2.4.2/2.4.3)
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai-core <xenomai@xenomai.org>, =?ISO-8859-1?Q?Cornelius_K=F6pp?= <Cornelius.Koepp@domain.hid>

Jan Kiszka wrote:
> Sebastian Smolorz wrote:
>> Jan Kiszka wrote:
>>> This patch may do the trick: it uses the inverted tsc-to-ns function 
>>> instead of the frequency-based one. Be warned, it is totally untested 
>>> inside Xenomai, I just ran it in a user space test program. But it 
>>> may give an idea.
>>
>> Your patch needed two minor corrections (ns instead of ts in functions 
>> xnarch_ns_to_tsc()) in order to compile. A short run (30 minutes) of 
>> latency -t1 seems to prove your bug-fix: There seems to be no drift.
> 
> That's good to hear.
> 
>> If I got your patch correctly, it doesn't make xnarch_tsc_to_ns more 
>> precise but introduces a new function xnarch_ns_to_tsc() which is also 
>> less precise than the generic xnarch_ns_to_tsc(), right?
> 
> Yes. It is now precisely the inverse imprecision, so to say. :)
> 
>> So isn't there still the danger of getting wrong values when calling 
>> xnarch_tsc_to_ns()  not in combination with xnarch_ns_to_tsc()?
> 
> Only if the user decides to implement his own conversion. Xenomai with 
> all its skins and both in kernel and user space should always run 
> through the xnarch_* path.

OK, would you commit the patch?

-- 
Sebastian