How about running some slave lisp virtual machines in emacs to do background work?

[Zhang Haijun]

The slave lisp machine knows nothing in the master lisp machine 
(buffers, windows, frames ...), and it can't interact with the user. 
They are just background workers, and can only run lisp code in it's own 
environment.

Every slave machine is standalone, and doesn't share data with other 
machines(maybe can share copy-on-write data). So it can be fully 
multi-threading and can do heavy computing work.

Lisp programs in the main machine can send tasks(or lisp codes) to slave 
machines, and wait for results. And programs in the slave machine can 
send notifications to the master machine. Here they need a IPC framework 
to work better with each other.

The slave lisp machines may be limited to be a sandbox to run only safe 
codes.

Lisp programs in the master machine can create slave machines to use.

Something like async.el, but can share data more efficiently.