The idea of this bug is to get a sense of what will happen if we have compartment-per-global and if we allocate slot arrays as GC things (bug 648320). We'll probably have a lot more thingKinds and a lot more compartments. If we continue to have at least one arena per (thingKind, compartment) pair, we're probably going to have a lot of fragmentation of the arena-unused variety. We have ideas about how to rework things to reduce the fragmentation, but they're pretty speculative. dmandelin suggested we create a log of the following: - when a compartment or global is created/destroyed - when a GC thing is created and when it gets GCed - when slots are created/resized Then we could easily model different ideas using a script or something. We wouldn't have to touch SpiderMonkey code at all. I really like this idea.