Shared memory

[Guy Harris]

>Does anyone know if non-swappable shared memory is supported by
>System V? I need to know because some of our applications developers
>want it. Our sister division in California supports it, but I cannot
>find documentation for it in the SVID.

It's not in the SVID, but some versions of System V have (privileged!)
SHM_LOCK and SHM_UNLOCK "shmctl" operations that lock shared memory
segments into memory.  There is otherwise no guarantee that shared
memory segments are non-swappable; some older implementations happen to
lock them in memory, but other ones (more recent ones, generally) do
not.