Re: [Xen-devel] [PATCH RFC v1 4/4] libxc for rt scheduler

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On ven, 2014-07-18 at 10:47 +0100, Ian Campbell wrote:

> Lets not repeat that mistake with this new scheduler, if the domctl (or
> a sysctl for that matter) needs per VCPU information then it should IMHO
> take the parameters inline in the struct (like the others), anything
> dynamic like the per-vcpu stuff should then be a GUEST_HANDLE pointer to
> a dynamically sized array (accessed with copy_from_guest_offset et al).
> 
Indeed.

There is one other subtle difference, between the new scheduler Meng is
working on, and the existing ones (even leaving ARINC out).

In fact, SEDF, Credit and Credit2, only allows per domain parameters,
while Meng's scheduler supports per-vcpu parameters, and hence he needs
a guest handle to deal with the array of these per-vcpu parameters.

BTW, while writing this, I saw your
<1405677108.13883.9.camel@xxxxxxxxxxxxxxxxxxxxxx>, which goes straight
to the point I was trying to make, and with which I totally concur. :-)

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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