[linux-dvb] Re: full featured card without signal and required video memory investigation

[Johannes Stezenbach <js@convergence.de>]

Oliver Endriss wrote:
> On Monday 14 July 2003 14:48, Johannes Stezenbach wrote:
> >
> > There are two things that cause the high load:
> > - the I2C driver
> > - the frontend thread that uses I2C to talk to the frontend
> >
> > If you can improve the I2C driver, great. But the load won't go
> > unless we change the frontend thread. Which isn't difficult, but it
> > is a policy decision.
> 
> According to oprofile the load is caused by the busy-waiting stuff in 
> the i2c code. The zig-zag scan isn't a problem, because the fe thread 
> *sleeps* for 200ms after each tuning attempt.

Hm.

> BTW, I had a look into dvb-kernel and noticed that the i2c code is 
> interrupt-driven. A quick test showed that the fe thread caused 
> virtually no cpu load, even if the sat signal is missing!
> 
> Maybe the guys who use the DVB-S without a dish should simply switch to 
> dvb-kernel...

Last time I checked the dvb-kernel I2C was noticably slower because the
mdelay()s were replaced by schedule_timeout()s. But with your patch
applied it could be just as fast?


Johannes


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