Re: [Xen-devel] Why have an idle domain? (Was: IDLE domain is scheduled more than dom0)

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 12 Jul 2005, at 20:08, Magenheimer, Dan (HP Labs Fort Collins) wrote:

> So is there any good reason to have an idle domain other than
> because that's the way OS schedulers have always done it?
You can do whatever tricks you like in context_switch() when switching 
to/from the idle domain. arch/x86 already avoids switching most cpu 
state, so latency for short-blocking i/o domains is very small.
An idle domain is a convenient abstraction for thinking about the 
current scheduling state of a cpu -- it allows us to treat things more 
uniformly in the common code. Of course we can treat the idle domains 
very specially during state switch for performance.
I guess this will be even more important for arch/ia64, with the 
monstrous amount of architectural state to be switched.
 -- Keir


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