For VMM implementations of over 150 hosts, Microsoft advises you to enable Server Optimized Garbage Collection (GC). Workstation GC is the default and is only available on single processor systems. Server GC is available for multiprocessor computers. This method, according to Microsoft, starts to provide benefits of computers with 4 or more processors. Below are the instructions to implement Server Optimized GC from Microsoft.
To accomplish this, simply create a new filed named vmmservice.exe.config and place this file in the same location as vmmservice.exe (VMMservice.exe is located in the bin directory of the VMM server role installation)
This link: http://go.microsoft.com/fwlink/?LinkId=102219, will show you what the contents of this file need to be.