JDK has been instrumented for performance measurement and typically output the data to the console or a log file. HotSpot has the jvmstat perf buffer that currently collects a list of perf counters output from HotSpot. The jvmstat perf buffer is created by default. Adding perf counters from the JDK will make the metrics always available and also make the data correlation much easier from a single source instead of data from multiple source (perfdata, log file, stdout, etc).