is the hypervisor another domain?

[Diwaker Gupta <diwakergupta@gmail.com>]

Hi everyone,

I was just investigating scheduling of VMs on Xen, and so I was
logging the following data from inside __enter_scheduler (in
xen/common/schedule.c):

id: prev->id
duration: now - prev->lastschd

Now, suppose I have domain0 and another VM (the first created after
dom0, thus gets a domain ID of 1) running. And to simplify matters I'm
using the round robin scheduler with default params (i.e. 10ms slice).
Now I would have expected to see dom0 (id=0) and the lone VM (id=1)
scheduled alternately.

However, I see a lot of instances where the id as recorded above
reports a value of 32767. I'm guessing this is the hypervisor? It'll
be great if someone can shed some light on this -- does the scheduler
treat the hypervisor as just another domain?

It'll be great if someone can shed more light on whats going on here.

Thanks,
Diwaker
-- 
Diwaker Gupta
http://resolute.ucsd.edu/diwaker


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