[TUHS] Memory management in Dennis Ritchie's C Compiler

Dan Halbert halbert at halwitz.org
Tue Aug 18 05:44:09 AEST 2020

On 8/17/20 3:30 PM, Larry McVoy wrote:
> On Mon, Aug 17, 2020 at 03:27:15PM -0400, Noel Chiappa wrote:
>>      > From: Jim Geist
>>      > When did mmap(2) come about?
>> Pretty sure it's a Berserkleyism. I think it came in with the VM stuff that
>> DARPA mandated for VAX Unix (for the research project they funded).
> Bill Joy imagined it, the prototype is in one the 4.x BSD releases.
> Sun (Joe Moran) actually implemented it first in any Unix variant.
> It's possible the concept existed in some other OS but I'm not aware
> of it.
I have a clear memory of having a discussion with Bill Joy about the 
idea of vread(2) and vwrite(2) when we were both grad students at 
Berkeley. I remember we were eating sausages from Top Dog and sitting 
outside Etcheverry Hall on or near the grassy plaza. I think vfork may 
have already existed, and we were talking about adding some kind of 
memory-mapped file I/O. I think I suggested the actual names, as a 
parallel to vfork. Some of my thinking might have come from my 
experience with TENEX while working summers at BBN. I was just a 
sounding board; I wasn't implementing any of this. vread and vwrite were 
in BSD4.1, but dropped in 4.2 (so my Googling says). I think it became 
clear later that mmap was an easier concept than the initial vread and 
vwrite ideas.

Dan H.

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