Arrays

Investigation finds G1GC card-marking barrier makes Arrays.fill 265x slower than ParallelGC

A JMH benchmark filling two reference arrays showed drastically different results depending on garbage collector: about 0.5ms on ParallelGC versus 139ms on G1GC, despite no garbage collection occurring during the measured operations. The author traces this gap through JIT compilation and JVM flags down to a specific machine instruction responsible for the slowdown.