@Group和@GroupThreads在jmh中指的是什么？

Question

I have been looking at the way jmh implements the "multithreaded" benchmarks. From my understanding, the annotations @Group("Identifier") and @GroupThreads(thread_number) enable running in parallel the benchmarks that are within the same Group.

@Benchmark
@Group("parallel")
@GroupThreads(1)
public void benchmark_1() {
    while(true) {}
}

@Benchmark
@Group("parallel")
@GroupThreads(1)
public void benchmark_2() {
    while(true) {}
}

Using the CPU monitor, I get that two CPU's are fully used. I would like to know how does the runner interpret those annotations.

Answer 1

Have you tried reading Javadocs? Are those not answering the question?

Eg @Group says:

 * <p>Multiple {@link Benchmark} methods can be bound in the execution group
 * to produce the asymmetric benchmark. Each execution group contains of one
 * or more threads. Each thread within a particular execution group executes
 * one of {@link Group}-annotated {@link Benchmark} methods. The number of
 * threads executing a particular {@link Benchmark} defaults to a single thread,
 * and can be overridden by {@link GroupThreads}.</p>
 *
 * <p>Multiple copies of an execution group may participate in the run, and
 * the number of groups depends on the number of worker threads requested.
 * JMH will take the requested number of worker threads, round it up to execution
 * group size, and then distribute the threads among the (multiple) groups.
 * Among other things, this guarantees fully-populated execution groups.</p>

 * <p>For example, running {@link Group} with two {@link Benchmark} methods,
 * each having {@link GroupThreads}(4), will run 8*N threads, where N is an
 * integer.</p>

So, @Group produces an asymmetric benchmark, @GroupThreads controls the distribution of threads within the group ( -tg ... in CLI dubs it). @Threads say how many threads to run in total ( -t ... in CLI dubs it).