vNUMA: A Virtual Shared-Memory Multiprocessor

vNUMA, for virtual NUMA, is a virtual machine that presents a cluster as a virtual shared-memory multiprocessor. It is designed to make the computational power of clusters available to legacy applications and operating systems. A characteristic aspect of vNUMA is that it incorporates distributed shared memory (DSM) inside the hypervisor, in contrast to the more traditional approach of providing it in middleware. We present the design of vNUMA, as well as an implementation on Itaniumbased workstations. We discuss in detail the enhancements to standard protocols that were required or enabled when implementing DSM inside a hypervisor, and discuss some of the tradeoffs we encountered. We examine the scalability of vNUMA on a small cluster, and analyse some of the design choices.