Benchmarking

ELI5 - The Vibe Check

Benchmarking is timing your code to prove it's actually fast, and it is shockingly easy to do wrong. Run something once and you're measuring a cold cache and a confused JIT compiler, not real performance. Real benchmarks warm up first, run many iterations, and report a distribution instead of one lucky number, because a single it ran in 2ms is basically a rumor.

Real Talk

Benchmarking is the disciplined measurement of code performance under controlled, repeatable conditions. Reliable microbenchmarks account for JIT warmup, garbage collection pauses, and CPU frequency scaling, and report statistical distributions like median and percentiles rather than a single run, since a single measurement is dominated by noise and can even be skewed by dead code elimination in the compiler.

Show Me The Code

// A naive benchmark lies: no warmup, one run, result never used
const start = performance.now();
const result = expensiveFn();
console.log(performance.now() - start);
// A real benchmark: warm up, run N times, report percentiles

When You'll Hear This

"That benchmark result is meaningless, you ran it once with a cold JIT." / "We benchmark with a proper warmup phase now after getting burned by fake numbers."