RAM is "cheap". Or is it?
If a million machine data center could cut RAM in half, how much could be saved, in capital equipment cost and power/cooling expense?
Transcendent Memory (or "tmem") is a new approach for flexibly, dynamically, and efficiently managing physical memory. First conceived to facilitate the optimization of physical memory utilization among a set of guests in a virtualization environment (and implemented in Xen 4.0), tmem has now also been applied in the kernel to dynamically compress page cache and swap pages ("zcache"), and to dynamically hot-plug memory among a set of kernels ("RAMster").
And tmem may, in the future, allow more effective utilization of future memory-extension technologies. All this with very minimal changes to the kernel required.