free page zeroing and ksm

[Peter Lieven]

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
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