On 2/2/06, Bakul Shah <bakul+plan9@bitblocks.com> wrote:
>
> > >> one disadvantage of the library approach in the unix environment is
> that
> > >> you're once again back having to know which `access method' to use,
> > >> to pass the file descriptor or handle to the right library.
> > >> i might easily have misunderstood something though.
> >
> > > [reasonable explanation deleted]
> > > I bet they do something along these lines.
> >
> > yes, i supposed it could be something along those lines but i didn't
> make my
> > point clear.
> > if it is along those lines, it breaks something that even sockets didn't
> brea
> > k.
> > at the moment, i get a file descriptor that i can pass to anything that
> does
> > read and write.
> > now i've got something that i can only mmap, and even the mmap refers to
> a
> > non-trivial data structure shared with the kernel, and the recipient of
> the f
> > ile descriptor
> > must invoke special calls in a special library (ie, the `access
> method').
> > i suppose you could call it TCAM
>
> Once you have mmap (and most versions of Unix do these days)
> you have already bought into the associated complexity.  If
> you pass a file descriptor with an associated mmap to a
> process, what happens is determined by mmap flags used when
> the mapping was created.  So all I am saying is that there
> is nothing "special" about it.  It is no more "broken".  And
> at least this is a useful extension (in that it can make the
> kernel simpler without losing performance if they take out
> any compatibility crap).  If you exclusively used mmap for
> files, even more stuff can potentially be taken out of the
> kernel -- just pass the received data map directly to the
> file server process.
>

And with 64bit Virtual Memory why not mmap everything? [except for the
thrashing on my poor hard disk and lack of terrabytes of physical memory :)]

I jokingly have been saying this to only close personal friends for a while.

Why can't I mmap a remote process's memory?  Some embedded systems [used
to?] let me do this and pass messages with memcpy :).

Throw off the shackles of "read" and "write" calls.... use mmap instead :)

*chuckle*