Accessing JMH state

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I'm setting up the JMH benchmarks for my application and I'm wondering is there any difference between passing JMH state via benchmark's and accessing it from benchmark body?

In other words

@Benchmark
public int myBenchmark(MyState state) {
MyObject objFromState= state.objFromState;
return objFromState.benchmarkMe();
}

VS

@Benchmark
public int myBenchmark() {
return objFromState.benchmarkMe();
}
jmh microbenchmark profiling java performance
1 Answers

From official JMH samples:

... Since JMH is heavily used to build concurrent benchmarks, we opted for an explicit notion of state-bearing objects ... Benchmark methods can reference the states, and JMH will inject the appropriate states while calling these methods.

All samples I saw always reference a state the same way as in the snippet:

  @State(Scope.Thread)
  public static class ThreadState {
      volatile double x = Math.PI;
  }

  @Benchmark
  public void measureUnshared(ThreadState state) {
    state.x++;
  }

You have to specify the scope of your state, explicitly declare it using annotation - you "register" it by doing this. The state object further will be injected to a method refers to it (by declaring the dependency as a method parameter). In your second snippet you reference to the state object - yes, but this is not a shared state.

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