memory pages nulling when releasing

[Peter Jeremy]

On Sun, 2006-Jun-18 13:39:03 -0700, R. B. Riddick wrote: Instead of
>zero'ing pages immediately after the process does not need them
>anymore, it would be much better, to keep the system safe
>(especially: security relevant software patches; and (even more)
>physical safety)

The Unix model provides security as long as you don't bypass the
access controls by (eg) reading /dev/mem.

The OS only needs to explicitly zero a page if it is handing it back
to a process without otherwise initialising it.  There's no need to
zero a page if it's going to be used to satisfy a pagein request.
FreeBSD tries to reduce the effective overhead of page zeroing by
zeroing them in the idle loop and keeping a cache of pre-zeroed pages
for handing out to processes.

-- 
Peter Jeremy
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