Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!pt.cs.cmu.edu!wb1.cs.cmu.edu!avie
From: avie@wb1.cs.cmu.edu (Avadis Tevanian)
Newsgroups: comp.os.mach
Subject: Re: Combining UNIX-style and MACH-style messaging
Message-ID: <8604@pt.cs.cmu.edu>
Date: 26 Mar 90 22:56:36 GMT
References: <39068@cornell.UUCP>
Distribution: comp
Organization: NeXT, Inc.
Lines: 22

In article <39068@cornell.UUCP> ken@cs.cornell.edu (Ken Birman) writes:
>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...

Well, if you were to do this you'd end up throwing away most of the performance
gains you are after.  One advantages of the Mach interface is that you
can effectively combine the UNIX select/recv into just one call, msg_receive.

Besides, the code is actually not that difficult.  The way we do this in
NextStep is to assume that the majority of communication occurs using
Mach IPC (it does).  All of the main pathways are IPC based, if someone also
wants to wait on a fd, a separate thread does the select and sends a message
to the main thread with data is available.  The common case is super fast,
the less common case is not a lot slower than it was before (the additional
context switch is negligible when compared to the costs of the write/select/
read).
-- 
Avadis Tevanian, Jr.    (Avie)
Manager, System Software
NeXT, Inc.
avie@NeXT.COM