PKSM is developed as an improvement over KSM (Kernel Samepage Merging) and UKSM (Ultra Kernel Samepage Merging) for memory-saving data de-duplication by merging matching anonymous pages between programs. Ultra KSM provides transparent full system memory de-duplication on Linux, but PKSM seeks to take data de-duplication one step further for the Linux kernel. (Ultra KSM was previously covered on Phoronix last summer.)
PKSM seeks to be fully transparent for the user in terms of memory data de-duplication, highly effectively for anonymous page detection through the use of a new algorithm, provides full zero page consideration, and checks the page content periodically.
PKSM 0.1 was released in late March as a patch against the Linux 3.6 kernel. There's also Arch Linux package. At the moment it doesn't appear the project is attempting mainline inclusion anytime soon.
For those wanting to find more about this Linux kernel feature for memory de-duplication of pages, visit the Google Code page.