[linux-dvb] Re: Fwd: Re: DEBI irq oops, crashes: kernel 2.6 &Hyperthreading unusable with DVB

[Udo Wolter <uwp@dicke-aersche.de>]

On Sat, 8 May 2004, Michael Hunold wrote:

> > Are there any kernel changes which could make my situation better ? The
> > preemptive kernel parameter or the MSI vector based IRQs ? Or even
> > vice versa, is it better to switch something off ? Or any other
> > kernel parameter ?
>
> Not really. Call it a race condition or something else -- it's a logical
> programming error that needs to be fixed when it comes to SMP or
> hyperthreading.

Oh, that's bad. Ok, I'll wait...

> > I'd stand a lot if it just costs only 5% performance
> > but I want to stay in hyperthreading. Switching off hyperthreading costs
> > 30-40% performance. :(
>
> In the meantime, you need to turn off hyperthreading and kernel
> preemption unless Johannes, me or someone else has fixed this problem
> thorougly.

It seems to be more stable without preemption AND no irq balancing.
In this case it seems that almost all interrupts are running on
CPU0 and just the running programs are changing CPUs. With this
configuration the messages are only flooding when recording and watching
at once. Recording of 3 channels at once only lead to some messages.
The system only crashed once the last 12 hours (because of cutting and
recording) which is better than before (before it crashed every 3 hours).
It's not what I would call a stable situation but it's kind of a
workaround. The system itself is more under pressure than before, load
is 50% higher than before but on a 3 GHz you hardly notice that.
BTW, watching at the same time is possible without having any DEBI-
messages when I'm accessing the data via network from another
machine. But not everyone has two machines at home. Nevertheless,
the preemtive stuff was a very good hint. The behaviour of 2.4 and
2.6 are equal now and so I can run the 2.6 tree with hyperthreading
enabled. I just take the risk. Thanx !

Mermgfurt,
		Udo
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