There's also Same OS, operating system level virtualization, like Docker, it's the less expensive default for https://www.ramnode.com/vps.php for example. Not at all familiar with this technology, but scanning Wikipedia if you used Docker would the libcontainer library be shared between container instances?
Likely it would be. But really Docker is more about convenience of deployment and (much) less about security. I would not run seriously untrusted code in merely a (Docker) container; I don't know much about the isolation guarantees of OpenVZ.
In any case, containers share OS kernel, OS page cache, etc. This can be beneficial even for a shared hosting as a way to offer a wide range of preinstalled software as ro-mounted into the container's file tree. Likely code pages of software started this way would also be shared.
