Impact of Intrinsics and inlining on Lambda's performance?

Question

I have used this benchmark java8-lambda-performance-test and when running it I have done the followings:

1.Disabled Intrinsic usage

2.Disabled Inlining

3.Disabled Compiling mode

I have found out that disabling the two first optimizations has no effect on results.

Which is strange, and also when running the benchmark with and print intrinsic, I did not find any call to the intrinsic compiledLambdaForm

Since maths intrinsics are heavily used there _min,_pow... I was expecting that disabling intrinsics would have slown the performance

Answer 1

The reason why you haven't noticed an expected performance effect is poorly written benchmark.
I rewrote the benchmark using JMH and the things finally got right.

package lambdademo;

import org.openjdk.jmh.annotations.*;

import java.util.List;

@State(Scope.Benchmark)
public class LambdaBenchmark {
    @Param("100")
    private static int loopCount;

    private static double identity(double val) {
        double result = 0;
        for (int i=0; i < loopCount; i++) {
            result += Math.sqrt(Math.abs(Math.pow(val, 2)));    
        }
        return result / loopCount;
    }

    private List<EmployeeRec> employeeList = new EmployeeFile().loadEmployeeList();

    @Benchmark
    public double streamAverage() {
        return streamAverageNoInline();
    }

    @Benchmark
    @Fork(jvmArgs = "-XX:-Inline")
    public double streamAverageNoInline() {
        return employeeList.stream()
                .filter(s -> s.getGender().equals("M"))
                .mapToDouble(s -> s.getAge())
                .average()
                .getAsDouble();
    }

    @Benchmark
    public double streamMath() {
        return streamMathNoIntrinsic();
    }

    @Benchmark
    @Fork(jvmArgs = {"-XX:+UnlockDiagnosticVMOptions", "-XX:DisableIntrinsic=_dpow,_dabs,_dsqrt"})
    public double streamMathNoIntrinsic() {
        return employeeList.stream()
                .filter(s -> s.getGender().equals("M"))
                .mapToDouble(s -> identity(s.getAge()))
                .average()
                .getAsDouble();
    }
}

Here are the results:

Benchmark                              Mode  Cnt     Score    Error  Units
LambdaBenchmark.streamAverage          avgt    5    71,490 ±  0,770  ms/op
LambdaBenchmark.streamAverageNoInline  avgt    5   122,740 ±  0,576  ms/op
LambdaBenchmark.streamMath             avgt    5    92,672 ±  1,538  ms/op
LambdaBenchmark.streamMathNoIntrinsic  avgt    5  5747,007 ± 20,387  ms/op

As expected, the benchmark with -XX:-Inline works 70% longer, and the version with Math intrinsics disabled appears to be 60 times slower!