HHVM or Hip Hop Virtual Machine has been ported over to the WordPress development crowd down to the core. HHVM was originally developed by Facebook as a way to curb expenses of more hardware for improved speed and reliability of server side php execution though a process know as JIT or Just In Time.
Through Varying Vagrant Vagrants or VVV, HMVM is ported into an Apache web development environment which allows for near production environment on WordPress functionality down to the core. VVV is a replacement sandbox for MAMP/XAMPP development tools and environments.
This interesting and useful news if you happen to be running your WordPress development server as a VM and on Apache. This allows for near production environment to exist in a development environment as a Virtual Machine to be configured and stressed just like a hardware web server in the actual OS, Linux, that the web server will actually use. This eliminates the step of development on a separate platform such as MAMP or XAMPP then transcribing configurations into usable configurations on your Linux/Apache web server. This speeds up the development to production cycle.
In addition to the development to production cycle speed up for WP users of VVV, the benefit which Facebook counted on is the ability to run PHP code more efficiently through the HHVM process/machine in production. The process utilizes JIT compilation based on server load and processing needs. This allows for more effective use of resources especially in the VM environment as compilers can be spun up based on need then spun back down once the peak load is over.
Hat Tip WP Tavern