500 Worker Threads, what kind of thread pool?

Question

I am wondering if this is the best way to do this. I have about 500 threads that run indefinitely, but Thread.sleep for a minute when done one cycle of processing. ``` ExecutorService es = Executors.newFixedThreadPool(list.size()+1); for (int i = 0; i < list.size(); i++) { es.execute(coreAppVector.elementAt(i)); //coreAppVector is a vector of extends thread objects } ``` The code that is executing is really simple and basically just this ``` class aThread extends Thread { public void run(){ while(true){ Thread.sleep(ONE_MINUTE); //Lots of computation every minute } } } ``` I do need a separate threads for each running task, so changing the architecture isn't an option. I tried making my threadPool size equal to Runtime.getRuntime().availableProcessors() which attempted to run all 500 threads, but only let 8 (4xhyperthreading) of them execute. The other threads wouldn't surrender and let other threads have their turn. I tried putting in a wait() and notify(), but still no luck. If anyo…

Accepted Answer

Why not used a `ScheduledExecutorService` to schedule each task to run once per minute, instead of leaving all these threads idle for a full minute?

```
ScheduledExecutorService workers = 
  Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors());
for (Runnable task : list) { 
  workers.scheduleWithFixedDelay(task, 0, 1, TimeUnit.MINUTES);
}
```

What do you mean by, "changing the architecture isn't an option"? If you mean that you can't modify your task at all (specifically, the tasks have to loop, instead of running once, and the call to `Thread.sleep()` can't be removed), then "good performance isn't an option," either.

500 Worker Threads, what kind of thread pool?

Solution

Problem