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  1. JDK
  2. JDK-8273060

Flight Recorder samples too less Event

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    Details

    • Subcomponent:
      jfr
    • CPU:
      generic
    • OS:
      generic

      Description

      ADDITIONAL SYSTEM INFORMATION :
      JDK 11, JDK 175, JDK 17 tested.

      A DESCRIPTION OF THE PROBLEM :
      Math.sin() is only hit ~ 0% with jdk.ExecutionSample
      StrictMath.sin() is only hit <90% with jdk.NativeMethodSample

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Execute a Javawith heave Math.sin() use and sample it with flight recorder. There are always less samples then configured.

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      Produce RunDuration/SamplePeriod Samples. Either as native or java sample.
      ACTUAL -
      Some math is not shown in neither native nor java samples. (0% java, 86% native)

      ---------- BEGIN SOURCE ----------
      package test;

      import java.io.File;
      import java.io.IOException;
      import java.nio.file.Path;
      import java.nio.file.Paths;
      import java.text.ParseException;
      import java.time.Duration;
      import java.util.ArrayList;
      import java.util.List;

      import jdk.jfr.Configuration;
      import jdk.jfr.consumer.RecordedEvent;
      import jdk.jfr.consumer.RecordingFile;

      public class Start {
      private static final Path DESTINATION = Paths.get("mySnapshot.jfr");
      volatile static boolean stop;

      public static void main(String[] args) throws IOException, ParseException, InterruptedException {
      new Thread("calculateJavaNativeExample") {
      @Override
      public void run() {
      while (!stop) {
      if (!calculateJavaNativeExample()) {
      stop = true;
      }
      }
      }

      }.start();
      new Thread("calculateDoubleExample") {
      @Override
      public void run() {
      while (!stop) {
      if (!calculateDoubleExample()) {
      stop = true;
      }
      }
      }

      }.start();

      Configuration configuration = Configuration.getConfiguration("default");
      int millis = 100;
      int samples = 100;
      for (int run = 0; run < 2; run++) { // multiple tries to give the Compiler a chance to compile
      try (jdk.jfr.Recording r = new jdk.jfr.Recording(configuration)) {
      r.setMaxSize(0); // unlimited
      r.setMaxAge(null);// unlimited
      r.setDumpOnExit(false);
      r.setToDisk(false);
      // "Method Profiling Sample":
      r.enable("jdk.ExecutionSample").withPeriod(Duration.ofMillis(millis));
      // "Method Profiling Sample Native":
      r.enable("jdk.NativeMethodSample").withPeriod(Duration.ofMillis(millis));
      r.start();
      Thread.sleep(millis * samples); // => 10sec
      r.stop();
      if (r.getSize() > 0) {
      r.dump(DESTINATION);
      }
      }
      }
      if (stop) {
      System.out.println("ERROR");
      } else {
      stop = true;
      System.out.println("OK");
      }
      List<RecordedEvent> allEvents = new ArrayList<>();
      try (RecordingFile recordingFile = new RecordingFile(DESTINATION)) {
      while (recordingFile.hasMoreEvents()) {
      allEvents.add(recordingFile.readEvent());
      }
      }
      // should be 100 - but ~0:
      long javaSamples = allEvents.stream().filter(t -> t.getEventType().getName().equals("jdk.ExecutionSample")).count();
      System.out.println("#jdk.ExecutionSample:" + javaSamples + " should be " + samples);

      // should be 100 - but <90:
      long nativeSamples = allEvents.stream().filter(t -> t.getEventType().getName().equals("jdk.NativeMethodSample")).count();
      System.out.println("#jdk.NativeMethodSample:" + nativeSamples + " should be " + samples);
      }

      static boolean calculateJavaNativeExample() {
      double x = 0;
      for (long j = 0; j < 10000; j++) {
      x = StrictMath.sin(x); //should result in NativeMethodSample
      }
      return x <= 1.0;
      }

      static boolean calculateSystemNativeExample() {
      File file = new File("does not exit");
      return !file.exists();
      }

      static int i;

      static boolean calculateIntExample() {
      int n = (i & 0xFF) + 1;
      // Collatz Problem
      while (n != 1) {
      if ((n & 1) == 0) {
      n = n / 2;
      } else {
      n = n * 3 + 1;
      }
      }
      i++;
      return n != 0;
      }

      static boolean calculateDoubleExample() {
      double x = 0;
      for (long j = 0; j < 10000; j++) {
      x = Math.sin(x); // @HotSpotIntrinsic //should result in ExecutionSample
      }
      return x <= 1.0;
      }

      }

      ---------- END SOURCE ----------

      FREQUENCY : always


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              Assignee:
              sswsharm swati sharma
              Reporter:
              webbuggrp Webbug Group
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                Dates

                Created:
                Updated:
                Resolved: