Executing without ahead-of-time compilation.
WHAT AN INTERPRETER DOES
Executes a program directly, translating as it runs.
WHAT A BYTECODE INTERPRETER DOES
Compiles to a compact intermediate form, then executes that.
WHY THAT IS FASTER
The parsing and analysis happen once rather than repeatedly.
WHAT A VIRTUAL MACHINE IS
The environment executing that bytecode.
WHAT JUST-IN-TIME COMPILATION DOES
Compiles frequently executed code to machine code while running.
WHY THAT WORKS WELL
It can optimise using information only available at runtime, such as actual types.
WHAT DEOPTIMISATION IS
Reverting to interpretation when an assumption proves wrong.
WHAT GARBAGE COLLECTION DOES
Reclaims memory no longer reachable.
WHAT APPROACHES EXIST
Tracing from roots to find reachable objects Reference counting Generational approaches, collecting young objects frequently
WHY GENERATIONAL COLLECTION WORKS
Most objects die young, so collecting them is cheap and productive.
WHAT COLLECTION COSTS
Pauses, memory overhead, and less predictable timing.
WHAT TO TUNE
Heap sizing, and collector choice, where the runtime allows.
WHAT TO MEASURE
Pause times, not only throughput.
