C#Task多线程限制并发数量Task对象很多⼈知道了(,
)
相对的还有TaskScheduler 这个调度器，可以⾃定义调度器，只要重写TaskScheduler ⽅法就可以了 微软原来⼀早就对他进⾏了扩展
转⼀下⾥的定义和调⽤⽅法
namespace System.Threading.Tasks.Schedulers
{
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
class Program
{
static void Main()
{
LimitedConcurrencyLevelTaskScheduler lcts = new LimitedConcurrencyLevelTaskScheduler(1);
TaskFactory factory = new TaskFactory(lcts);
factory.StartNew(()=>
{
for (int i = 0; i < 500; i++)
{
Console.Write("{0} on thread {1}", i, Thread.CurrentThread.ManagedThreadId);
}
}
);
Console.ReadKey();
}
}
/// <summary>
/// Provides a task scheduler that ensures a maximum concurrency level while
/
// running on top of the ThreadPool.
/// </summary>
public class LimitedConcurrencyLevelTaskScheduler : TaskScheduler
{
/// <summary>Whether the current thread is processing work items.</summary>
[ThreadStatic]
private static bool _currentThreadIsProcessingItems;
/// <summary>The list of tasks to be executed.</summary>
private readonly LinkedList<Task> _tasks = new LinkedList<Task>(); // protected by lock(_tasks)
/// <summary>The maximum concurrency level allowed by this scheduler.</summary>
private readonly int _maxDegreeOfParallelism;
/
// <summary>Whether the scheduler is currently processing work items.</summary>
private int _delegatesQueuedOrRunning = 0; // protected by lock(_tasks)
private int _delegatesQueuedOrRunning = 0; // protected by lock(_tasks)
/// <summary>
/// Initializes an instance of the LimitedConcurrencyLevelTaskScheduler class with the
/// specified degree of parallelism.
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/// <param name="maxDegreeOfParallelism">The maximum degree of parallelism provided by this scheduler.</param> public LimitedConcurrencyLevelTaskScheduler(int maxDegreeOfParallelism)
{
if (maxDegreeOfParallelism < 1) throw new ArgumentOutOfRangeException("maxDegreeOfParalleli
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_maxDegreeOfParallelism = maxDegreeOfParallelism;
}
/// <summary>Queues a task to the scheduler.</summary>
extractall/// <param name="task">The task to be queued.</param>
protected aled override void QueueTask(Task task)
{
// Add the task to the list of tasks to be procesd. If there aren't enough
// delegates currently queued or running to process tasks, schedule another.
containlock (_tasks)
{
_tasks.AddLast(task);
if (_delegatesQueuedOrRunning < _maxDegreeOfParallelism)
{
++_delegatesQueuedOrRunning;
NotifyThreadPoolOfPendingWork();
}
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}
}
/// <summary>
/// Informs the ThreadPool that there's work to be executed for this scheduler.
/// </summary>
private void NotifyThreadPoolOfPendingWork()
{
ThreadPool.UnsafeQueueUrWorkItem(_ =>
{
// Note that the current thread is now processing work items.
// This is necessary to enable inlining of tasks into this thread.
_currentThreadIsProcessingItems = true;
try
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// Process all available items in the queue.
while (true)
{
Task item;
lock (_tasks)
{
// When there are no more items to be procesd,
// note that we're done processing, and get out.
if (_tasks.Count == 0)
{
--_delegatesQueuedOrRunning;
pivotbreak;
}
/
/ Get the next item from the queue
item = _tasks.First.Value;
_tasks.RemoveFirst();
}
// Execute the task we pulled out of the queue
italian怎么读ba.TryExecuteTask(item);
}
}
// We're done processing items on the current thread
// We're done processing items on the current thread
finally { _currentThreadIsProcessingItems = fal; }
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}, null);
}
/// <summary>Attempts to execute the specified task on the current thread.</summary>
/// <param name="task">The task to be executed.</param>
/// <param name="taskWasPreviouslyQueued"></param>
/// <returns>Whether the task could be executed on the current thread.</returns>
protected aled override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued) {
// If this thread isn't already processing a task, we don't support inlining
if (!_currentThreadIsProcessingItems) return fal;
// If the task was previously queued, remove it from the queue
if (taskWasPreviouslyQueued) TryDequeue(task);
// Try to run the task.
return ba.TryExecuteTask(task);
}
/// <summary>Attempts to remove a previously scheduled task from the scheduler.</summary>
/// <param name="task">The task to be removed.</param>
/// <returns>Whether the task could be found and removed.</returns>
protected aled override bool TryDequeue(Task task)
{
lock (_tasks) return _tasks.Remove(task);
}
/// <summary>Gets the maximum concurrency level supported by this scheduler.</summary>
public aled override int MaximumConcurrencyLevel { get { return _maxDegreeOfParallelism; } }
/// <summary>Gets an enumerable of the tasks currently scheduled on this scheduler.</summary> /// <returns>An enumerable of the tasks currently scheduled.</returns>
protected aled override IEnumerable<Task> GetScheduledTasks()
{
bool lockTaken = fal;
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try
{
Monitor.TryEnter(_tasks, ref lockTaken);
if (lockTaken) return _tasks.ToArray();
el throw new NotSupportedException();
}
finally
{
if (lockTaken) Monitor.Exit(_tasks);
}
}
}
}
