Hmm... maybe some specs of your system would help. In general, having an overall memory load higher than 90%, I would expect a slow-down of any application in the system.
An incremental GC seems to be a somewhat more practical approach to not buy into any platform-specific virtual-memory manager but remain cross-platform comparable?
- http://source.squeak.org/VMMaker/VMMaker.oscog.seperateMarking-eem.3341.mcz