Compiler

We were using Scala in a few non-critical components at the trading firm — utility code, configuration, some tooling. Then someone proposed moving a market data normalisation component to Scala. The component processed 800,000 messages/second and had a 500µs latency budget per message at p99. The discussion that followed taught me more about the JVM than a year of reading. ...

Java’s “write once, run anywhere” promise is kept by the JVM. Its performance is kept by the JIT compiler. The gap between “Java is slow” (the 1998 opinion) and “Java is competitive with C++ for many workloads” (the 2013 reality, and more so now) is almost entirely the C2 compiler. Understanding what C2 does — and when it stops doing it — matters if you’re writing performance-sensitive Java. ...