Quick review of TPS: Transparent Page Sharing allows pages that are identical to be stored in same place. When there is idle CPU time, vSphere looks for pages located across virtual machines that can be matched with one another and shared in physical RAM. This is basically a deduplication method applied to RAM rather than storage. It allows vSphere to use just a single copy of these shared bits even though the bits are shared across two virtual machines. This may provide may provide substantial memory savings.
Historically this has been enabled by default. But this is about to change.
Transparent Page Sharing will be disabled by default at the next major version release as well as the future updates to vSphere 5.x.