[TUHS] the guy who brought up SVr4 on Sun machines

[Joerg Schilling]

Larry McVoy <lm at mcvoy.com> wrote:

> > You did not make a backup while you worked at Sun?
>
> Apparently your ethics and my ethics differ.  It was Sun's property, not mine.

You do not understand jokes?


> > Hint: I have been told 
> > from Sun employees that the Sun ZFS group did read my diploma thesis before 
> > they started with ZFS even though it is written in German ;-)
>
> Huh, interesting.  I'll check that out.  Both Jeff Bonwick and Bill Moore
> have worked for me.  Bonwick was one of my students at Stanford and I 
> hired him into the kernel group.  Bill worked for me on BitKeeper.
> I'll let you know what they say.

I had a long discussion about this background in September 2004 with Jeff in 
his office while we discussed how a new secure interface that does not need 
root privileges could be added to support readin hole lists for files. This 
resulted in the design of SEEK_HOLE/SEEK_DATA.

Before (around 1992) I had a really long meeting with Wolfgang Thaler (he is 
the designer and author of DDI/DKI) and after he mentioned that there are many 
people inside Sun that understand German, mentioned that my dimploma thesis

	http://cdrtools.sourceforge.net/private/WoFS.pdf

is used by many Sun kernel engineers as there was no similar paper from Sun.


> > There seems to be a general missunderstandings:
> > 
> > I do not call SunOS-4.x a "BSD based OS" as SunOS-4.0 introduced a new memory 
> > management subsystem in the kernel. 
>
> I think we can stop here.  The rest of the world at the time described
> SunOS as "a bug fixed BSD".  The mmap() interface was designed by Bill
> Joy while at UCB and was documented but not implemented in 4.2 BSD [*]

This is definitely a missunderstanding:

Bill did create a mmap() interface for BSD while in UCB, but this was already 
around 1984 and hard to use as there was no universal address space description
inside the kernel.

What you could do with the old interface that was also available in e.g. 
SunOS-3.5 is to map user space addresses to VME addresses, but you first had to 
valloc() the space before, to get a mmap() target address. After you then 
called mmap(), you did waste all the swap space that was needed to hold the 
address space description. We used this method at H.Berthold AG in 1986 for the 
Berthold image processor to get direct access to the 256 MB of image memory in 
the image proessor. We needed to waste a whole disk for swap to get the 
initial mapping into the address space descriptor for the related userland 
process. 

For SunOS-4.0, Bill did a complete rewrite of the whole virtual memory 
subsystem. This rewrite includes the filesystem and since SunOS-4.0, all file 
access is done via mmap(). Even read() based file I/O basically maps the 
related parts of a file into a transient kernel area from where a copyout() is 
done. With SunOS-4.x, mmap() has been much easier to use as there now was an 
object oriented linked list of address space descriptions.

If you like to know why Sun could not donate the new virtual memory 
implementation to BSD, this is because of the contract signed with AT&T in late 
1987 - even before SunOS-4.0 was send to customers. AT&T did know from the 
memory subsystem from a talk at USENIX in spring 1987.

What I had to do when the Sparcstation came up was to write a segment driver to 
support the MMU in our VME<->S-Bus adaptor in order to come around the 32 MByte 
limitation for the addresses in an S-Bus slot.

BTW: in order to avoid more missunderstandings, could you mention when you have 
been in the Sun kernel group and what kind of things you did with the kernel?

Jörg

-- 
 EMail:joerg at schily.net                  (home) Jörg Schilling D-13353 Berlin
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