Path: utzoo!attcan!uunet!snorkelwacker!usc!brutus.cs.uiuc.edu!rpi!batcomputer!cornell!ken
From: ken@gvax.cs.cornell.edu (Ken Birman)
Newsgroups: comp.os.mach
Subject: Re: Combining UNIX-style and MACH-style messaging
Message-ID: <39068@cornell.UUCP>
Date: 26 Mar 90 18:52:50 GMT
Sender: nobody@cornell.UUCP
Reply-To: ken@cs.cornell.edu (Ken Birman)
Distribution: comp
Organization: Cornell Univ. CS Dept, Ithaca NY
Lines: 46

Joe Boykin at Encore answered my questions as follows:
  1) I can't get "select" to run on a Mach port; have to fork off a thread
     for each port-set on which I want to do a read (or perhaps for each
     port) and structure my code to interrupt the select if a message comes
     in this way.
  2) I need to use the environment manager to pass the receive rights,
     or build some equivalent mechanism into ISIS to map from ISIS addresses
     to mach ports.
My guess is that (1) translates to a lot of code for me, (2) seems pretty
straightforward.

Probably, I will do this, but as an aside to the Mach group let me make
the following points.  For a project like mine, there is no major advantage
to Mach except speed: it is a more elegant operating system, granted, but
my code already was working just fine, and portability is very important to
me.  So, to the extent that I specialize I am going to have to combine UNIX
and Mach features, and will do it mostly for some overwhelming performance
advantage.

The scheme Joe outlined actually implies a fairly substantial amount of 
code in ISIS: I would estimate 1-2 weeks full time for someone without
much Mach experience.

On the other hand, if Mach offered me an AF_MACH socket type from UNIX,
I could benefit from Mach performance without adding a zillion ifdef's
to use the various special Mach facilities that I seem unable to avoid.

As I see it, there seems to be some inconsistency between Rick (who 
recently explained that he views Mach as a core system, with interfaces
like UNIX, VMS, and even OS/2 layered around it for those who want them)
and Joe, who seems to be more of a purist (if you want the speed, do it
our way).  Personally, I want do minimize the amount of work I do and
maximize portability for my UNIX code, while also benefiting from Mach
performance...  And, the bottom line is that this will only benefit
ISIS users who run ISIS over Mach: a small minority of our community.

So how about it, Rick?  Why not give me an AF_MACH socket type and
a make_unix_fdes(port-no) system call, so that I can do select and
just hack my recvfrom/sendto code... I bet that there are more people
like me than you realize.  Sure, I like your system, but I'm just too
busy to do everything differently to make use of it.  And, unless a lot
of people do redo things, it looks to me as if the major Mach advantages
are very hard to "experience" without a big investment.   That is, if
you are doing UNIX over Mach, why not do it right?

Ken