由于JIT编译，Caliper基准测试失败

Question

我得到了一个卡尺基准，如下所示：

public Course timeCourseCreation( int i ) {

  return createCourse( i );
}

public Course createCourse( int t ) {

  Course course = new Course();

  for ( int i = 0 + t; i < this.students + t; i++ ) {
    Student student = new Student();
    student.setAge( ( int ) ( 100 * Math.random() ) + t );
    student.setName( UUID.randomUUID().toString() );
    course.getStudents().add( student );
  }

  for ( int i = 0 + t; i < this.courses + t; i++ ) {
    Topic topic = new Topic();
    topic.setDescription( UUID.randomUUID().toString() );
    topic.setDifficulty( ( int ) ( 10 * Math.random() ) + t );
    topic.setName( UUID.randomUUID().toString() );
    topic.setRating( ( int ) ( 10 * Math.random() ) + t );
    course.getTopics().add( topic );
  }

  return course;
}

Failed to execute java -cp C:\Users\tuhrig\workspace\XmlVsJson\target\classes;C:\Users\tuhrig\.m2\repository\javax\xml\bind\jaxb-api\2.2.11\jaxb-api-2.2.11.jar;C:\Users\tuhrig\.m2\repository\com\google\code\gson\gson\2.2.4\gson-2.2.4.jar;C:\Users\tuhrig\.m2\repository\com\google\caliper\caliper\0.5-rc1\caliper-0.5-rc1.jar;C:\Users\tuhrig\.m2\repository\com\google\code\findbugs\jsr305\1.3.9\jsr305-1.3.9.jar;C:\Users\tuhrig\.m2\repository\com\google\guava\guava\11.0.1\guava-11.0.1.jar;C:\Users\tuhrig\.m2\repository\com\google\code\java-allocation-instrumenter\java-allocation-instrumenter\2.0\java-allocation-instrumenter-2.0.jar;C:\Users\tuhrig\.m2\repository\asm\asm\3.3.1\asm-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-analysis\3.3.1\asm-analysis-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-commons\3.3.1\asm-commons-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-tree\3.3.1\asm-tree-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-util\3.3.1\asm-util-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-xml\3.3.1\asm-xml-3.3.1.jar com.google.caliper.InProcessRunner --warmupMillis 3000 --runMillis 1000 --measurementType TIME --marker //ZxJ/ -Dbenchmark=CourseCreation de.tuhrig.Benchmark
starting Scenario{vm=java, trial=0, benchmark=CourseCreation}
[caliper] [starting warmup]
[caliper] [starting measured section]
[caliper] [done measured section]
[caliper] [starting measured section]
...
Error: Doing 2x as much work didn't take 2x as much time! Is the JIT optimizing away the body of your benchmark?
...
An exception was thrown from the benchmark code.
com.google.caliper.ConfigurationException: Failed to execute java -cp C:\Users\tuhrig\workspace\XmlVsJson\target\classes;C:\Users\tuhrig\.m2\repository\javax\xml\bind\jaxb-api\2.2.11\jaxb-api-2.2.11.jar;C:\Users\tuhrig\.m2\repository\com\google\code\gson\gson\2.2.4\gson-2.2.4.jar;C:\Users\tuhrig\.m2\repository\com\google\caliper\caliper\0.5-rc1\caliper-0.5-rc1.jar;C:\Users\tuhrig\.m2\repository\com\google\code\findbugs\jsr305\1.3.9\jsr305-1.3.9.jar;C:\Users\tuhrig\.m2\repository\com\google\guava\guava\11.0.1\guava-11.0.1.jar;C:\Users\tuhrig\.m2\repository\com\google\code\java-allocation-instrumenter\java-allocation-instrumenter\2.0\java-allocation-instrumenter-2.0.jar;C:\Users\tuhrig\.m2\repository\asm\asm\3.3.1\asm-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-analysis\3.3.1\asm-analysis-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-commons\3.3.1\asm-commons-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-tree\3.3.1\asm-tree-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-util\3.3.1\asm-util-3.3.1.jar;C:\Users\tuhrig\.m2\repository\asm\asm-xml\3.3.1\asm-xml-3.3.1.jar com.google.caliper.InProcessRunner --warmupMillis 3000 --runMillis 1000 --measurementType TIME --marker //ZxJ/ -Dbenchmark=CourseCreation de.tuhrig.Benchmark
    at com.google.caliper.Runner.measure(Runner.java:309)
    at com.google.caliper.Runner.runScenario(Runner.java:229)
    at com.google.caliper.Runner.runOutOfProcess(Runner.java:378)
    at com.google.caliper.Runner.run(Runner.java:97)
    at com.google.caliper.Runner.main(Runner.java:423)
    at de.tuhrig.CaliperRunner.main(CaliperRunner.java:22)

Answer 1

众所周知，JIT会以可怕的方式扰乱您的代码，使所有的度量都绝对不可靠。人们挣扎了很多，试图让事情至少有点正确，但最终写出了像JMH这样的东西。这是一个很好的工具，可以帮助测量性能，并实际得到有意义的结果。它甚至使您能够避免死代码消除，并有大量的示例，看看这些示例肯定会帮助您解决您的问题...

但这条路走错了。这通常是一个秘密，但既然你自己已经找到了正确的方法，我就告诉你。可以使用-xint选项禁用JIT。在那里。不用谢我。