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First and foremost, read the Doppio Developer Guide!

Java Information

• SE5 Spec
  • JVM Opcodes
  • .class file spec
• SE7 Spec
• Wikipedia's .class file page
• High-level overview of how the JVM works

Tracing Hotspot Execution

• For (slow) bytecode tracing, download the debug build here and run with -XX:+TraceBytecodes
• For faster method tracing: https://github.com/int3/dsjt
• Of course, a debugger (like jdb) is useful too

Profiling Javascript Engines

• Useful Node flags:
  • --trace-bailout --trace-opt --trace-deopt --code-comments -- inspect JIT behavior
  • --prof (Parse profile dump using nprof) -- find the most heavily-used functions