> Well, this is a fundamental space vs time tradeoff — reclaiming memory takes time, usually on the very same thread that would be doing useful work we care abo

> Well, this is a fundamental space vs time tradeoff — reclaiming memory takes time, usually on the very same thread that would be doing useful work we care about. Precisely. Which is fine if you don't have to share that space with anyone else; the example which started this sub-thread ("running ~200 JVMs on the same machine") is one in which that tradeoff goes badly. But it wouldn't be as much of an issue if the JVMs could coordinate between themselves (and with other processes on the same machine), so that whenever one JVM (or other things like the kernel itself) felt too much memory pressure, the other JVMs could clean some garbage and release it back to the common pool of the operating system.