The Xen 4.1 release contains a number of important new features and updates including:

• A re-architected XL toolstack that is functionally nearly equivalent to XM/XEND
• Prototype credit2 scheduler designed for latency-sensitive workloads and very large systems
• CPU Pools for advanced partitioning
• Support for large systems (>255 processors and 1GB/2MB super page support)
• Support for x86 Advanced Vector eXtension (AVX)
• New Memory Access API enabling integration of 3rd party security solutions into Xen virtualized environments
• Even better stability through our new automated regression tests
• Xen 4.1 Release Notes
• Xen 4.1 Datasheet