[$] Persistent memory for transient data

Arguably, the most notable characteristic of persistent memory is that it
is persistent: it retains its contents over power cycles. One other
important aspect of these persistent-memory arrays that, we are told, will
soon be everywhere, is their sheer size and low cost; persistent memory is
a relatively
inexpensive way to attach large amounts of memory to a system. Large,
cheap memory arrays seem likely to be attractive to users who may not care
about persistence and who can live with slower access speeds. Supporting
such users is the objective of a pair of
patch sets that have been circulating in recent months.