performance3JfrConcepts

1package pkg19performance;2 3/*4 * performance3JfrConcepts.java5 * ------------------------------6 * Java Flight Recorder (JFR): low-overhead production profiling built into the JDK.7 *8 * DEFINITION:9 *   JFR records JVM and application events (CPU, locks, GC, I/O, custom) with10 *   minimal overhead. Analyze recordings in JDK Mission Control (JMC) or jfr print.11 *12 * KEY POINTS:13 *   - Start: -XX:StartFlightRecording=... or jcmd <pid> JFR.start14 *   - Events: jdk.CPULoad, jdk.GarbageCollection, jdk.ThreadStart, custom @Name events15 *   - jfr print recording.jfr — CLI summary16 *   - Prefer JFR over ad-hoc logging for performance investigations.17 */18public class performance3JfrConcepts {19 20    public static void main(String[] args) throws InterruptedException {21        System.out.println("JFR is built into the JDK (no extra install).");22        System.out.println("\nStart a 10s recording from CLI:");23        System.out.println("  java -XX:StartFlightRecording=duration=10s,filename=demo.jfr performance3JfrConcepts.java");24        System.out.println("\nOr attach to running process:");25        System.out.println("  jcmd <pid> JFR.start name=demo settings=profile duration=30s filename=demo.jfr");26        System.out.println("  jfr print --events jdk.GarbageCollection demo.jfr");27 28        // Simulate some work while a recording might run29        long sum = 0;30        for (int i = 0; i < 10_000_000; i++) sum += i;31        System.out.println("\nComputed sum (work sample): " + sum);32    }33}