There's a new tweak in 4.3 concerning *global-gc-behavior* that
_might_ be useful to some people.  See p.15-20 of the 4.3 ACL User
Guide.  You can cause global gc to happen only when either:

 - a certain amount of tenuring has occurred and the system has been
completely idle for some time period; or
 - a certain (presumably larger) amount of tenuring has occurred.

This doesn't help all applications, but for ones that are used
intermittently it can increase the likelihood it will happen at some
harmless time.

BTW, this mechanism works only if the multiprocessing scheduler has
been started.