[linux-dvb] Re: Driver CPU requirements?

[Lauri Pesonen <lauri.pesonen@firsthop.com>]

On Tue, 2002-07-02 at 14:07, Holger Waechtler wrote:
> Lauri Pesonen wrote:
> > Hi,
> > 
> > I was just updating my Gentoo Linux based VDR box and noticed that
> > compiling new software raised the system load to 2.5 and above.
> > Eventually the system over heated, I guess, since the compiler exited
> > with Sig11. 
> 
> Sig11 is a Segmentation Fault, this should never happen and means either 
> a compiler bug or that your system was running out of memory but the 
> compiler did not checked the malloc/calloc return value.

Yes, I know. But you get sigsegvs in situations where the CPU over heats
especially during compiles. Compiling the kernel in a while loop over
the night is a good test for your systems stability ;)

> >  I killed VDR and unloaded the driver and retried. The system load stayed
> > below 1.5 and all compilations were finished ok. 
> > 
> > So I'm wondering is the driver enforcing a lot of context switches,
> > which, I guess, would explain the high load during compiling, or am I
> > just experiencing some weird anomaly?
> 
> For HighEnd-Cards (those with the onboard MPEG decoder) the system load 
> in normal use with a stable RF signal should stay near zero, only the 
> ARM recovery thread and the frontend recovery thread have to check the 
> hardware status sometimes.
> 
> When the signal gets lost the zigzag scan will start and cause some load.
> 
> If you use a NOVA- or Budget then demultiplexing and MPEG-decoding is 
> done in software, so the CPU load will be higher.

VDR was running without any active recordings so the budget card should
be idle. The fullfeatured card would be decoding the stream and
providing it to the TV. 

The signal from my cable provider is not the best one. Tuning to QAM_128
bouquets is very difficult and requires typically a few retries. So that
might be the reason. 

Thanks for your help!
 
> Holger

br, Lauri



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