SVR4 vs BSD (was AIX (is it unix)?)

[Guy Harris]

 >Oh.  This I do not really understand, since the RFS mechanisms are pretty
 >much equivalent to the VFS mechanisms, except that instead of
 >
 >	vnode->vn_op(vnode, arg1, arg2)
 >
 >one writes
 >
 >	(*fsswitch[inode.fstype])(inode, arg1, arg2)

OK.  You used "RFS" instead of "FSS" ("File System Switch"), just as some
people refer to "NFS" when they really want to refer to VFS (the
"Virtual File System" mechanism).  Actually, in S5R3, RFS doesn't fully
*use* the FSS mechanism - it still does a lot of things by capturing
system calls directly.  I think the intent is to put it mostly, if not
entirely, under VFS for S5R4.

 >I.e., other than the vnode/inode/gnode/foonode differences found between
 >all the different `virtual remote generic network filesystem interface
 >definition specification ...' er, well, whatever, systems.  I had supposed
 >that VR4 was going to stick with RFS-style mechanisms.

Nope.  S5R4 is switching to a VFS mechanism.

 >>Are you saying that the SunOS 4.0 VM design was done at Berkeley, and
 >>just "modified a bit" at Sun?
 >
 >Well, actually, there was a fair bit of interaction (and not just from
 >Sun), but the basic design (mmap+mummap, protection, mapped files) comes
 >almost straight from 4.2BSD (where it came almost straight from Multics).
 >There are areas where Sun and Berkeley might not agree (e.g., mmap
 >for semaphored memory),

"Semaphored memory"?

 >but the user/system interface will at least be very similar.   (The
 >implementations are likely to be quite different.)

OK, you were referring to the *interface* design, not the
*implementation* design; the latter was done at Sun, while the former is
derived from the stuff described in the 4.2BSD paper, but not
implemented in 4.xBSD (except perhaps trivially for some device drivers,
just as was the case in SunOS prior to 4.0.)