Re: memory-mapped I/O (was: Re: Removing ARCNET stuffs)

["James K. Lowden" <jklowden%schemamania.org@localhost>]

On Wed, 03 Jun 2015 15:28:49 -0700
"Greg A. Woods" <woods%planix.ca@localhost> wrote:

> You just ask the filesystem what region of memory is represented by
> some name you know it as and if you can have access to it, and the
> filesystem and memory manager arrange it so that your process won't
> get a SIGSEGV when you access that memory.  That file is (and always
> was and always will be) just an array in memory.  (of course there
> are some slightly messier details if you're using segmented
> addressing architecture, which is what the real Multics was designed
> for at the time, but those are implementation details, not
> necessarily pre-requisites to the design)

Thanks for your post, Greg.  Could you explain a bit how writing
worked for sequential files?  Was there some kind of "automatically
growing memory" object that would accomodate something like a log
file?  The cursor supplied by a file descriptor, especially one
supporting  O_APPEND, isn't easy to emulate with mmap.  

--jkl