Java 线程正在ThreadPoolExecutor中等待
这段代码运行非常慢。我转储了线程,几乎有一个线程同时运行,但是当我将Java 线程正在ThreadPoolExecutor中等待,java,threadpool,Java,Threadpool,这段代码运行非常慢。我转储了线程,几乎有一个线程同时运行,但是当我将ExecutorService更改为ForkJoinPool时,代码运行得非常快。我不知道为什么线程在等待,我的计算机有8个内核 公共类测试{ 公共静态void main(字符串[]args)引发InterruptedException{ int NUM_OF_线程=8; int NUM_OF_增量=100_000_000; //ExecutorService=Executors.newWorkStealingPool();
ExecutorService
更改为ForkJoinPool
时,代码运行得非常快。我不知道为什么线程在等待,我的计算机有8个内核
公共类测试{
公共静态void main(字符串[]args)引发InterruptedException{
int NUM_OF_线程=8;
int NUM_OF_增量=100_000_000;
//ExecutorService=Executors.newWorkStealingPool();
ExecutorService=Executors.newFixedThreadPool(线程数);
最终计数器=新的StupidCounter();
很久以前=System.currentTimeMillis();
对于(int i=0;i
“pool-1-thread-7”#17 prio=5 os_prio=31 tid=0x00007faaa481c000 nid=0x6503等待条件[0x0000700001d6d000]
java.lang.Thread.State:等待(停车)
在sun.misc.Unsafe.park(本机方法)
-停车等待(java.util.concurrent.locks.ReentrantLock$NonfairSync)
位于java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
位于java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
在java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly处(AbstractQueuedSynchronizer.java:897)
位于java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1222)
在java.util.concurrent.locks.ReentrantLock.lockInterruptablely(ReentrantLock.java:335)处
位于java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:439)
位于java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
位于java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
位于java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
运行(617Thread.java:745)
很难从这段代码中得出任何真正的结论,因为它实际上什么都没有做。执行器的内部队列是瓶颈,这就是为什么一次只能看到一个线程“工作”。它实际上不工作,它从队列中获取下一个任务,使所有其他线程(也获取下一个任务)等待。除了LinkedBlockingQueue.take()
的功能外,您并没有在这里真正测试任何东西
increment()
方法不是线程安全的,因此基本上您测试的是错误的代码,结果几乎不相关。如果让反请求
任务执行实际的工作,这需要几毫秒,那么与使用FixedThreadPool时的ForkJoinPool
相比,您会发现性能上的差异要小得多(如果有的话),因为程序消耗了大量的时间,所以大部分时间都用于垃圾收集。我尝试使用VM参数-Xmx3g执行,但当VM试图避免内存耗尽时,仍然陷入垃圾收集
您可能希望使用内存转储来深入了解消耗的根本原因,但我猜这是计数器中的长实例
无论如何,根本原因似乎是使用LinkedBlockingQueue作为工作队列的FixedThreadPool。由于for循环向工作队列中添加了100_000_000个元素,因此很少有其他线程从中获取元素。因此,他们大部分时间都在等待所有的反诉提交
ForkJoinPool使用了一种更无阻塞的方式,据我所知,提交的操作有多个工作队列
public class Tests {
public static void main(String[] args) throws InterruptedException {
int NUM_OF_THREADS = 8;
int NUM_OF_INCREMENTS = 100_000_000;
//ExecutorService service = Executors.newWorkStealingPool();
ExecutorService service = Executors.newFixedThreadPool(NUM_OF_THREADS);
final Counter counter = new StupidCounter();
long before = System.currentTimeMillis();
for (int i = 0; i < NUM_OF_INCREMENTS; i++) {
service.submit(newCounterClient(counter, i));
}
service.shutdown();
service.awaitTermination(1, TimeUnit.MINUTES);
long end = System.currentTimeMillis();
System.out.println(end - before);
System.out.println(counter.getCounter());
}
static class CounterClient implements Runnable {
private Counter counter;
private int num;
public CounterClient(Counter counter, int num) {
this.counter = counter;
this.num = num;
}
@Override
public void run() {
counter.increment();
}
}
static interface Counter {
void increment();
long getCounter();
}
static class StupidCounter implements Counter {
long i = 0;
@Override
public void increment() {
i++;
}
@Override
public long getCounter() {
return i;
}
}
}
"pool-1-thread-7" #17 prio=5 os_prio=31 tid=0x00007faaa481c000 nid=0x6503 waiting on condition [0x0000700001d6d000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0x00000006c006b3d8> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:897)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1222)
at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:335)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:439)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(617Thread.java:745)