Re: WAY WAY OFFTOPIC: Message passing vs. shared memory (WAS: Re: 3.0 wishlist Was: Overview of 2.2.

Stephen Williams (
Sun, 25 Jan 1998 10:31:38 -0800

To throw fuel on the fire... :-) said:
> Which is better or worse of message passing or shared memory is a
> matter of religion: the professors usually beat eachother up with
> arguments for which is of preference.

A simple existence proof can show that message passing is computationally
equivalent to shared memory w/ semaphores. algorithms tuned for each can
be implemented with the other.

I've done very large distributed systems and find that message passing
better reflects the distributed reality of large systems. When you start
getting into error handling and faults, that memory doesn't normally have,
you start to realize why communication protocols are described with messages.

DSHM is a neat idea, and should be provided by Linux, especially for the
smaller problems, but the real nasty systems are going to be using some
sort of message passing protocol.

Steve Williams                "The woods are lovely, dark and deep.              But I have promises to keep,            and lines to code before I sleep,       And lines to code before I sleep."