java8中parallelStream性能测试及结果分析

测试1

@benchmarkmode(mode.averagetime)
@outputtimeunit(timeunit.nanoseconds)
@warmup(iterations = 5, time = 3, timeunit = timeunit.seconds)
@measurement(iterations = 20, time = 3, timeunit = timeunit.seconds)
@fork(1)
@state(scope.benchmark)
public class streambenchtest {
  list<string> data = new arraylist<>();
  @setup
  public void init() {
    // prepare
    for(int i=0;i<100;i++){
      data.add(uuid.randomuuid().tostring());
    }
  }
  @teardown
  public void destory() {
    // destory
  }
  @benchmark
  public void benchstream(){
    data.stream().foreach(e -> {
      e.getbytes();
      try {
        thread.sleep(10);
      } catch (interruptedexception e1) {
        e1.printstacktrace();
      }
    });
  }
  @benchmark
  public void benchparallelstream(){
    data.parallelstream().foreach(e -> {
      e.getbytes();
      try {
        thread.sleep(10);
      } catch (interruptedexception e1) {
        e1.printstacktrace();
      }
    });
  }
  public static void main(string[] args) throws runnerexception {
    options opt = new optionsbuilder()
        .include(".*" +streambenchtest.class.getsimplename()+ ".*")
        .forks(1)
        .build();
    new runner(opt).run();
  }
}

parallelstream线程数

默认是runtime.getruntime().availableprocessors() - 1，这里为7

运行结果

# run complete. total time: 00:02:44
benchmark              mode cnt      score     error units
streambenchtest.benchparallelstream avgt  20  155868805.437 ± 1509175.840 ns/op
streambenchtest.benchstream     avgt  20 1147570372.950 ± 6138494.414 ns/op

测试2

将数据data改为30，同时sleep改为100

benchmark              mode cnt      score     error units
streambenchtest.benchparallelstream avgt  20  414230854.631 ± 725294.455 ns/op
streambenchtest.benchstream     avgt  20 3107250608.500 ± 4805037.628 ns/op

可以发现sleep越长，parallelstream优势越明显。

小结

parallelstream在阻塞场景下优势更明显，其线程池个数默认为
runtime.getruntime().availableprocessors() - 1，如果需修改则需设置-djava.util.concurrent.forkjoinpool.common.parallelism=8

以上就是本次讲述知识点的全部内容，感谢你对的支持。