[CentOS] Virtualisation, guests cached memory and density

Hello,

We all know linux distros will use most of the free memory available 
for caching stuff, I/O buffers etc (hence sites like linuxatemyram.com).
In many virt scenarios we have some sort of memory deduplication 
mechanisms, such as KSM on KVM (don't know how it's called in Vmware).

My situation is one where I need to cram up as many virtual machines as 
I can on a single hypervisor and I believe KSM does not work for the 
memory used as cache/buffers.
How could I work around this? Any other pointers for achieving higher 
density welcome (don't suggest container technology please).

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