A hypervisor is just an operating system (arbiter of resource use) relying on legacy operating systems as compatibility shims, because it has a native API nobod

A hypervisor is just an operating system (arbiter of resource use) relying on legacy operating systems as compatibility shims, because it has a native API nobody wants to deal with. It seems strange that we see resource contention problems when applications try to coexist on an operating system, and our response is to give each app its own guest O/S and then try to make those coexist. Why do we expect an improvement? I can't believe the existing O/S schedulers and paging policies were so poor that anything similar written from scratch for a hypervisor will automatically make better decisions despite less visibility into what's going on. That said, I can certainly see a win in virtualization for testing. If your production system will have a large set of discrete machines communicating, you can simulate that with a much smaller pool of QA machines (maybe just one).