多线程运行，cpu使用率过高
1 使用Fork/Join，类似代码如下，运行起来，CPU过高
public class MyTask extends RecursiveTask {
private static final long serialVersionUID = 1103203544619621157L;
int THRESHOLD = 100;int start;int end; int[] arr;
public MyTask(int[] arr,int start,int end){
this.arr = arr;
this.start = start;
this.end = end;
}
@Override
protected Integer compute() {
if(end - start <= THRESHOLD){
int sum = 0;
for(int i= start;i<end;i++){
sum += arr[i];
}
return sum;
}
int mid = (end + start)/2;
MyTask t1 = new MyTask(arr,start,mid);
MyTask t2 = new MyTask(arr,mid,end);
invokeAll(t1, t2);
return t1.join() + t2.join();
}
public static void main(String args){
int[] arr = new int[5000];
random(arr);
ForkJoinPool pool = new ForkJoinPool();
MyTask task = new MyTask(arr,0,arr.length);
pool.invoke(task);
}
}
2 堆栈信息如下
"ForkJoinPool-1-worker-8" daemon prio=10 tid=0x00007fab88001000 nid=0x32d4 waiting on condition [0x00007fac178b7000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.ForkJoinPool)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864)
at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398)
"ForkJoinPool-1-worker-6" daemon prio=10 tid=0x00007fab8c004800 nid=0x32d2 waiting on condition [0x00007fac17ab9000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.ForkJoinPool)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864)
at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398)
"ForkJoinPool-1-worker-5" daemon prio=10 tid=0x00007fab90003000 nid=0x32d1 waiting on condition [0x00007fac17bba000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.ForkJoinPool)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864)
at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398)
"ForkJoinPool-1-worker-4" daemon prio=10 tid=0x00007fab90001000 nid=0x32d0 waiting on condition [0x00007fac17cbb000]
java.lang.Thread.State: TIMED_WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.ForkJoinPool)
at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226)
at java.util.concurrent.ForkJoinPool.idleAwaitWork(ForkJoinPool.java:894)
at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:830)
at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398)
"ForkJoinPool-1-worker-2" daemon prio=10 tid=0x00007fab8c001000 nid=0x32ce waiting on condition [0x00007fac17ebd000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.ForkJoinPool)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.ForkJoinPool.tryAwaitWork(ForkJoinPool.java:864)
at java.util.concurrent.ForkJoinPool.work(ForkJoinPool.java:647)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:398)
"http-bio-3080-exec-10" daemon prio=10 tid=0x00007fabc8007000 nid=0x32b5 waiting on condition [0x00007fac34260000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
"http-bio-3080-exec-9" daemon prio=10 tid=0x00007fabc8005000 nid=0x32b4 waiting on condition [0x00007fac34361000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
"http-bio-3080-exec-8" daemon prio=10 tid=0x00007fabc8003800 nid=0x32b3 waiting on condition [0x00007fac34462000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
"http-bio-3080-exec-7" daemon prio=10 tid=0x00007faba4001000 nid=0x32b2 waiting on condition [0x00007fac34563000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)
- parking to wait for (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104)
at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32)
at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
你在compute里面又开新的task
当然会开很多task，每个task都 join到一起，就很费cpu了。
具体怎么优化要看你程序要做什么
你的cpu使用率是哪个高？ 是中断高还是上下文切换高？