Question

如果我将maxConcurrency作为10传递，下面的代码会将最大并行任务限制为10吗？如何验证一次运行的任务数量？

public BlockingCollection<Task> _workTaskQueue;

public void DequeueTask(int maxConcurrency)
{
    var tasks = new List<Task>();
    using (SemaphoreSlim concurrencySemaphore = new SemaphoreSlim(maxConcurrency))
    {
        foreach (var task in _workTaskQueue.GetConsumingEnumerable())
        {
            concurrencySemaphore.Wait();
            if (!(task.IsCanceled) && task.Status == TaskStatus.Created)
            {
                task.ContinueWith((t) => { concurrencySemaphore.Release(); });
                tasks.Add(task);
                task.Start();
            }
        }
    }
    Task.WaitAll(tasks.ToArray());
}

Answer 1

由于您使用my other answer改变了逻辑，我为您准备了一个测试代码。（不需要var tasks = new List<Task>();）

Random rnd = new Random();
int maxConcurrency = 5;
var _workTaskQueue = new System.Collections.Concurrent.BlockingCollection<Task>();
for (int i = 0; i < 250; i++) 
{
    //Tasks running 250=500ms
    _workTaskQueue.Add(new Task(()=> { Task.Delay(250 + rnd.Next(250)).Wait(); }));
} 
_workTaskQueue.CompleteAdding();
int runningTaks = 0;

using (SemaphoreSlim concurrencySemaphore = new SemaphoreSlim(maxConcurrency))
{
    foreach (var task in _workTaskQueue.GetConsumingEnumerable())
    {
        Console.WriteLine("LoopStart: " + runningTaks);

        await concurrencySemaphore.WaitAsync();

        Console.WriteLine("GotASem  : " + runningTaks);

        task.Start(); 
        Interlocked.Increment(ref runningTaks);
        task.ContinueWith(t =>
            {
                Interlocked.Decrement(ref runningTaks);
                concurrencySemaphore.Release();
            });

        if (runningTaks > maxConcurrency) throw new Exception("ERROR");
        Console.WriteLine("LoopEnd  : " + runningTaks + Environment.NewLine);
    }

    Console.WriteLine("Finalizing: " + runningTaks);
    //Make sure all all tasks have ended.
    for (int i = 0; i < maxConcurrency; i++)
    {
        await concurrencySemaphore.WaitAsync();
    }

    Console.WriteLine("Finished: " + runningTaks);
}

Answer 2

没有。缺少呼叫等待（进入互斥区块）。

SemaphoreSlim的用法在下面的代码上下文中是否正确？它会限制最大运行线程吗？

2 个答案: