Re: realtime scheduling

[Stephan Diestelhorst <sd386@cam.ac.uk>]

Keir Fraser schrieb:

>
> On 8 Aug 2005, at 16:06, Holger Steinhaus wrote:
>
>> 1.) Are there any releases with a working RT-like scheduler?
>> 2.) Do you have any other idea to minimize the scheduling-related
>> latency for domain 0?
>
>
> The SEDF scheduler in the 3.0 tree should allow you to specify RT
> guarantees. Alternatively, if you have a multi-CPU system, or even
> hyperthreading, you can dedicate a cpu (or hyperthread) solely to
> domain0.
>
>  -- keir

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...)
  -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

Could you please try the second one and see how that works? If it works
well, I might change the default behaviour, so that the latency aware
scheduler gets enabled for a domain if it uses the latency parameter!

Cheers,
  Stephan