Main author of Quasar here. Quasar's bytecode instrumentation is really very gentle -- no class fields/methods are added/removed and object state isn't changed in any way. It is far, far less intrusive than, say, JRebel. While Java 9 sadly won't include native JVM fibers or continuations, it will probably make the instrumentation process 100% transparent.
Java 9 will introduce the G1 GC as default. How do the emulation of continuations behave regarding this GC? Is is possible to obtain truly pauseless behavior with Quaser and G1?
