Xen 4.4 Released
Here are the highlights from Xen.org's blog: *"Although the development part of the release cycle was shorter than the previous one, we still have far too many exciting improvements than we can mention in this blog post; I’ll call out just a few.
Probably one of the most important is solid libvirt support for libxl. Jim Fehlig from SuSE and Ian Jackson from Citrix worked together to test and improve the interface between libvirt and libxl, making it fast and reliable. This lays the foundation for solid integration into any tools that can use libvirt, from GUI VM managers to cloud orchestration layers like CloudStack or OpenStack.
Another big one is a new scalable event channel interface, designed and implemented by David Vrabel from Citrix. The original Xen event channel interface was limited to the number of bits on the platform squared — 1024 for 32-bit guests and 4096 for 64-bit guests. With many VMs requiring 4 event channels each, that means a theoretical maximum of 256 guests on a 32-bit dom0 — more than enough back when a large machine had 8 cores, and every VM was a full OS; but a major limitation on systems with 128 cores, or those using cloud OSes like Mirage or OSv. The new “FIFO” event channel interface by default scales up to over 200,000 event channels, and in the future can be extended even further if necessary in a backwards-compatible manner. This should be enough for many years to come.
The ARM port is maturing quickly. As of 4.4, the hypervisor ABI for ARM has been declared stable, meaning that any guest which uses the 4.4 ARM ABI can rely on being able to boot on all future versions of Xen. There are a number of improvements making Xen on ARM more flexible, easier to set up and use, and easier to extend to new platforms. More details can be found in the Xen 4.4 feature list.
One other feature worth a note is Nested Virtualization on Intel hardware. It’s not ready for production use yet, but it has improved to the point where we feel comfortable moving it from “experimental” to “tech preview”. Please feel free to take it for a spin and report any issues you find.
There are many more improvements and changes under the hood. For a more complete list, see the Xen 4.4 feature list."*
And here is a write up from "The VAR Guy": http://thevarguy.com/virtualization-applications-and-technologies/031014/embargo-monday-march-10-8-am-est-xen-44-open-source-vir