使用Task.Factory.FromAsync時泄漏

Question

我一直在使用Task.Factory.FromAsync（）方法，並且一直在經歷嚴重的內存泄漏。我用探查它表明，大量的對象似乎只是使用後遊逛：

Heap shot 140 at 98.591 secs: size: 220177584, object count: 2803125, class count: 98, roots: 666 
     Bytes  Count Average Class name 
     25049168  142325  175 System.Threading.Tasks.Task<System.Int32> (bytes: +398816, count: +2266) 
      1 root references (1 pinning) 
      142324 references from: System.Threading.Tasks.Task 
      142305 references from: System.Threading.Tasks.TaskCompletionSource<System.Int32> 
      98309 references from: task_test.Task3Test.<Run>c__AnonStorey1 
     25049024  142324  176 System.Threading.Tasks.Task (bytes: +398816, count: +2266) 
      142304 references from: System.Threading.Tasks.TaskContinuation 
     17078880  142324  120 System.Action<System.Threading.Tasks.Task<System.Int32>> (bytes: +271920, count: +2266) 
      142324 references from: System.Threading.Tasks.TaskActionInvoker.ActionTaskInvoke<System.Int32> 
     17076600  142305  120 System.Runtime.Remoting.Messaging.MonoMethodMessage (bytes: +271680, count: +2264) 
      1 root references (1 pinning) 
      142304 references from: System.MonoAsyncCall 
     17076584  142305  119 System.AsyncCallback (bytes: +271920, count: +2266) 
      1 root references (1 pinning) 
      142304 references from: System.MonoAsyncCall 
     17076584  142305  119 System.Func<System.Int32> (bytes: +271920, count: +2266) 
      1 root references (1 pinning) 
      142305 references from: System.Func<System.IAsyncResult,System.Int32> 
      142304 references from: System.Runtime.Remoting.Messaging.AsyncResult 
      1 references from: System.Func<System.AsyncCallback,System.Object,System.IAsyncResult> 
     17076584  142305  119 System.Func<System.IAsyncResult,System.Int32> (bytes: +271920, count: +2266) 
      1 root references (1 pinning) 
      142305 references from: System.Threading.Tasks.TaskFactory.<FromAsyncBeginEnd>c__AnonStorey3A<System.Int32> 
     17076480  142304  120 System.Runtime.Remoting.Messaging.AsyncResult (bytes: +271800, count: +2265) 
      98461 references from: System.Object[] 

我試圖找出什麼類型的東西可能/可能不會出現阻止了從識別物體的gc不再被使用。 FromAsync返回一個從TaskCompletionSource獲得的Task對象，該對象具有一個類變量「source」，該變量包含Task從任務調用中獲取的值。

這裏是測試用例。它還包括使用StartNew（）的情況，其中內存使用沒有爆炸。下面的初始Test3Task沒有使用ContinueWith，但是看看它是不是我們沒有清理的東西，我們把它放在了（沒有效果）。 [不，下面使用的聆聽變量是多餘的 - 有計劃，使測試更加聰明，但一做永遠是一樣好。]

using System; 
using System.Threading; 
using System.Threading.Tasks; 

namespace task_test 
{ 
    class MainClass 
    { 
      public static void Main (string[] args) 
      { 
        // Test3 - Leaky 
        var t = new Task3Test(); 

        // Test4 - Doesn't leak 
        // var t = new Task4Test(); 

        t.Run(); 

      } 
    } 

    public class BaseTask 
    { 
      public int GetRandomInt(int top) 
      { 
        Random random = new Random(); 

        return random.Next(1,top); 
      } 
    } 

    public class FibArgs 
    { 
      public byte[] data; 
      public int n; 
    } 

    public class Fib 
    { 
      public int Calculate(FibArgs args) 
      { 
        int n = args.n; 

        int a = 0; 
        int b = 1; 
        // In N steps compute Fibonacci sequence iteratively. 
        for (int i = 0; i < n; i++) 
        { 
          int temp = a; 
          a = b; 
          b = temp + b; 
        } 
        Console.WriteLine("ThreadId: {2}, fib({0}) = {1}", n, a, Thread.CurrentThread.GetHashCode()); 
        return a; 
      } 
    } 

    public class Task3Test : BaseTask 
    { 
      public void Run() 
      { 
        bool listening = true; 
        long i = 0; 
        while (listening) 
        { 
          i++; 

          Func<int> fun =() => { 
            int n = GetRandomInt(100); 
            Fib f = new Fib(); 
            FibArgs args = new FibArgs(); 
            args.n = n; 

            return f.Calculate(args); 
          }; 

          var t = Task<int>.Factory.FromAsync(fun.BeginInvoke, fun.EndInvoke, null); 
          t.ContinueWith(x => { 
                if (x.IsCompleted) { 
                  x.Dispose(); 
                  x = null; 
                } 
              } 
            ); 
        } 
      } 
    } 

    public class Task4Test : BaseTask 
    { 
      public void Run() 
      { 
        bool listening = true; 
        long i = 0; 
        while (listening) 
        { 
          int n = GetRandomInt(100); 
          Fib f = new Fib(); 
          FibArgs args = new FibArgs(); 
          args.n = n; 

          Task.Factory.StartNew(() => f.Calculate(args), TaskCreationOptions.LongRunning) 
            .ContinueWith(x => { 
              if(x.IsFaulted) 
              { 
                Console.WriteLine("OOPS, error!!!"); 
                x.Exception.Handle(_ => true); //just an example, you'll want to handle properly 

              } 
              else if(x.IsCompleted) 
              { 
                Console.WriteLine("Cleaning up task {0}", x.Id); 
                x.Dispose(); 
              } 
            } 
          ); 
        } 
      } 

    } 
} 

Answer 1

我敢肯定，問題是你創建任務比完成更快，所以他們排隊。