Re: realtime scheduling

[Holger Steinhaus <hsteinhaus@gmx.de>]

>The default compile of the sedf scheduler is not optimised for latency
>(but the standard setting might work well...).
>You can do a couple of things:
>  -set the period of dom0 to roughly your latency (better half of it)
>and scale your slice accordingly
>   (e.g. 2ms period, 0.3ms slice...)
>  
>
Ok, done. I installed a fresh devel version of Xen (from Aug 7), 
including kernel 2.6.12.3 and SEDF scheduling (in my original post: Xen 
2.0.7, kernel 2.6.11.12, original scheduler). The major change: now the 
buffer problems even occur without any user domain.

I tried to play around with the period/slice parameters, and found some 
values that really boost the problems. As the HFC driver generates 8000 
interupts per second (I assume for timing purposes), the desired period 
of 62500 ns is not possible on my machine. I think, I'll take a closer 
look on the driver first...


>  -or edit xen/common/schedule_sedf.c and change
>     #define UNBLOCK UNBLOCK_EXTRA_SUPPORT
>     to
>     #define UNBLOCK UNBLOCK_ATROPOS
>     and then set the appropriate latancy value in xm sedf (this does
>exactly the same thing internaly
>  
>
Makes no recognizable difference, in my opinion.

Thanks,
  Holger