Re: [RFC] Add static priority into credit scheduler

[NISHIGUCHI Naoki <nisiguti@jp.fujitsu.com>]

Hi Disheng and George,

Disheng, I'm glad to see your work.

George Dunlap wrote:
> I'd be interested to hear others' opinions.

I think that static priority is useful under some conditions.
But, as George said, I also think it is harder to configure properly.
And I'm anxious that it makes credits on non-RT vcpu meaningless.

I tested your patch in following environment.

   CPU: Intel Core2 Quad Q9450
   Chipset: Intel 82Q35
   VM: dom0 (4 vcpus), HVM (4 vcpus)
   Xen: c/s 19426
   HVM:
     RT priority (1)
     pass-through devcies
       PCI graphic board
       Integrated devices(audio, USB controller)
     playing video

With this configuration, HVM does not work well.
When HVM does not have RT priority, HVM works well.

I think we would need to consider the relationship between static 
priority and credit, handling of dom0 and driver domain, and so on.

Best regards,
Naoki Nishiguchi