When did paging get into System V

[guy at gorodish.UUCP]

> So?  Performance tests showed no significant performance advantage of
> demand paging over the then-current UNIX System V scheme of partial
> swapping.

Umm, I don't even think System V had been *released* when the original paging
BSD releases came out.  I believe one of the papers on the BSD paging code
indicated that there *was* a performance benefit over the 32V partial swapping
scheme for large jobs.

  It was not until the additional advantages of an organized
> scheme like the UNIX System V region-oriented approach became apparent
> (e.g. shared libraries) that there was reason enough to implement it.

The first paging S5 releases didn't have shared libraries; that arrived later.
Are you certain that the organizational advantages of a less *ad hoc* scheme
were the *only* reasons they went to paging?  I doubt that.

> Conversations I've had with kernel implementors indicate that, modulo
> a few glitches that can be readily corrected, the UNIX System V scheme
> (which resembles VMS's) is on the right track, and that Babaoglu's
> scheme embedded in 4BSD often has to be totally replaced.  (Sun
> designed their original memory management hardware to look virtually
> the same as the VAX's, to avoid this.  Not everyone has had that option.)

This is, as somebody pointed out, complete nonsense.  The Sun MMU looks nothing
like the VAX MMU; the pre-4.0 VM implementation has code to sort of emulate the
VAX MMU on a Sun.  The 4.0 VM implementation (which is not region-oriented, but
page-oriented, although shared libraries were implemented atop it) was also
designed to be portable.  (So far, implementations exist for the Sun MMU, the
80386 on-chip MMU, and the IBM 370-style MMU.)