free page zeroing and ksm

Hi all,

working a lot with KVM and KSM I came across the question if Linux (like e.g. Windows) zeroes out free pages after usage. I came across some patches for page sanitization which where submitted in 2009 and have not been merged for various reasons.

Working with memory deduplication the primary goal is not sanitization of the pages, but have them not contain any garbage after they are freed.

My question is if there is any mechanism in Linux to zero out unused pages? I found some people claiming that there is such a mechanism, but I found no reference.

If there is not would it be possible to implement a kernel process that scans for unused pages and zeroes them out during idle time?

Thanks,
Peter