[gclist] GC triggering strategies

[Charles Fiterman]

> > Anybody know of others?
> 
> Well, you can give the user a procedure to call, which means "Now is a
> good time."  Perhaps with a parameter saying *how* good.  Seems like a
> better approach than totally automatic systems with fancy heuristics.

The best time to collect is when the mutator is idle and waiting.

We have a 
  gcAttemptCollection(gcIdleFunction funptr);

This is meant to be called when the calling program is waiting for
an event. If there was a reasonable amount of allocation since the
last collection a collection is started. It various points the
passed function is called. It should return a 1 if the calling
program has no work and a 1 if something like a key press or a
mouse click has happened. The caller determines what that is.

We find this usually completes in the real world.