Re: USB making time drift [was Re: dynamic-hz]

Pavel Machek
2004-12-15T20:17:07Z

Hi!

> >> Which way? I was running quite fast here, several minutes an
> >
> >In the future, if I disable the logic it goes in the past at the
> > same speed it was previously going in the future.
> >
> >> hour, then I discovered the tickadj command, found its default
> >> was 10000, and started reducing it. At 9926, I'm staying within
> >> a sec an hour now. I have no idea when this started, I didn't
> >
> >That seems quite an hack, note I did an hack too and it make the
> > drift much smaller (it gets manageable). But our modifications are
> > wrong.
> >
> >The point is that this didn't happen with HZ=100, so it's not that
> >tickadj is wrong, it's the tick adjustment code that doesn't work.
> >
> The HZ=1000 is the culprit?
>
> >You may want to recompile your kernel with HZ=100 and verify it goes
> >away (I didn't verify myself, but I verified the max irq latency I
> > get is 4msec, and in turn I'm sure HZ=100 would fix it
>
> Humm, that might also reduce the obviousness of the irq activity in
> the audio, there are times when I can hear it very plainly while a
> low level audio src is in use, like the sub-millivolt levels that come
> out of my Hauppauge WinTV-GO+FM card. I keep having to turn the

Try idle=poll. That noise may be commig from cpu switching between
powersave and full speed.
Pavel
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