Re: [Xenomai-core] latencys drifting into negative (Xenomai 2.4.2/2.4.3)

[Jan Kiszka <jan.kiszka@domain.hid>]

[-- Attachment #1: Type: text/plain, Size: 1141 bytes --]

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.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 258 bytes --]