[Xen-devel] Pointed questions re Xen memory overcommit

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

With the Xen memory overcommit (Satori and xenpaging) work getting
closer to the real world (and indeed one gating factor for a major
Xen release), I wonder if it is time to ask some very pointed
questions:

1) How is the capability and implementation similar or different
from VMware's?  And specifically I'm asking for hard information
relating to:

http://lwn.net/Articles/309155/ 
http://lwn.net/Articles/330589/ 

I am not a lawyer and my employer forbids me from reading the
related patent claims or speculating on any related issues, but
I will be strongly recommending a thorough legal review before
Oracle ships this code in any form that customers can enable.
(I'm hoping for an answer that would render a review moot.)

2) Assuming no legal issues, how is Xen memory overcommit different
or better than VMware's, which is known to have lots of issues
in the real world, such that few customers (outside of a handful
of domains such as VDI) enable it?  Or is this effort largely to
remove an item from the VMware sales team's differentiation list?
And a comparison vs Hyper-V and KVM would be interesting also.

3) Is there new evidence that a host-based-policy-driven memory
balancer works sufficiently well on one system, or for
multiple hosts, or for a data center?  It would be nice for
all Xen developers/vendors to understand the intended customer
(e.g. is it the desktop user running a handful of VMs running
known workloads?)

Perhaps this would be a better topic for the Xen Hack-a-thon...
sadly I won't be there and, anyway, I don't know if there will
be a quorum present of the Xen developers specifically working
on memory overcommit technology, so I thought it should be
brought up on-list beforehand.

Dan

Thanks... for the memory!
I really could use more / my throughput's on the floor
The balloon is flat / my swap disk's fat / I've OOM's in store
Overcommitted so much
(with apologies to Bob Hope)


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