RE: yanked share, round 2

[Rusty Russell <rusty@rustcorp.com.au>]

On Fri, 2006-01-13 at 15:02 -0800, King, Steven R wrote:
> How about combining both ideas:  In order to map N pages from Xen's
> share pool, a DomU must provide N pages back to the pool.  When a DomU
> unmaps (or crashes), it gets N pages back.

OK, early last year I hacked up a prototype implementation, which I'm
now bringing up-to-date with the modern Xen code, and some new
simplifications I'm toying with.

It's certainly a simple model to never have domains share their own
pages, and the hypervisor provide a DMA-like mechanism between domains
to allow bulk transfer.  This would then page-swap if appropriate.

It makes drivers nice and simple, and avoids problems with starvation
et. al.  Earlier results suggested it is competitive on benchmarks, too,
but it needs real testing under various loads.

Noone here should be surprised though, that I regard the simplicity of
the scheme as the most important factor.

Cheers!
Rusty.
-- 
 ccontrol: http://ozlabs.org/~rusty/ccontrol