[gclist] Another request from a Newbie :-)
Fri, 16 May 2003 11:53:27 +0200
> Real-time GC is difficult, but not impossible. Harlequin did a
> real-time Common Lisp, with contractual limits on pause times.
Sure there are such GC's. I list four such techniques in my previous
posting. The problem with most (other) "real-time" garbage collectors is
that they don't guarantee memory availability. It is common to say that you
have a real-time GC if the worst-case interrupt time is below a specified
threshold, but that does not mean much if you have no guarantee that the GC
progresses sufficiently (I'm not sure whether Harlequin's GC guarantees this
or not.) There are even cases of GC techniques that claim to be real-time
since the shortest measured interrupt time is X. This is simply not enough
for hard real-time. And again, to be able to guarantee memory availability,
you must know how much memory your application requires.