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

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

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Gilles Chanteperdrix wrote:
> Right. We are approximating a fraction with another fraction. But my
> first impression remains: I do not like the idea of making
> xnarch_ns_to_tsc wrong because xnarch_tsc_to_ns is wrong.

Well, my first impression was originally the same: If we still need 
llimd in the ns-to-tsc patch, then we should keep the precise way. But 
that was wrong as this thread demonstrated. We have to ensure that 
ns_to_tsc(tsc_to_ns(x)) remains x with only minor last-digit errors. So 
either use scaled math parameters in both ways or fall back to the 
original calculation.

However the final decision for 2.5 is (pro or contra scaled math), at 
least for 2.4.x we have to fix things now without turning the upside 
down. That means apply my patch or revert scaled-math optimizations for 
all archs.

Jan


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