ThreadPool.GetMaxThreads(Int32, Int32) 方法

參考

定義

命名空間:: System.Threading

組件:: System.Threading.ThreadPool.dll

組件:: mscorlib.dll

組件:: netstandard.dll

來源:: ThreadPool.CoreCLR.cs

來源:: ThreadPool.Unix.cs

來源:: ThreadPool.Unix.cs

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

擷取可並行使用之執行緒集區的要求數目。超過該數目的所有要求會繼續佇列，直到可以使用執行緒集區執行緒為止。

public:
 static void GetMaxThreads([Runtime::InteropServices::Out] int % workerThreads, [Runtime::InteropServices::Out] int % completionPortThreads);

public static void GetMaxThreads (out int workerThreads, out int completionPortThreads);

static member GetMaxThreads : int * int -> unit

Public Shared Sub GetMaxThreads (ByRef workerThreads As Integer, ByRef completionPortThreads As Integer)

參數

workerThreads: Int32

執行緒集區中的背景工作執行緒最大數目。

completionPortThreads: Int32

執行緒集區中的非同步 I/O 執行緒最大數目。

範例

下列程式碼範例示範如何擷取執行緒集區中線程數目上限和可用數目的計數。工作專案會排入佇列，用來 FileStream 以非同步方式寫入兩個檔案。回呼方法會計時重迭。背景工作執行緒會處理工作專案，並根據電腦上的處理器速度和數目而定，一或兩個完成埠執行緒會處理寫入作業。

using namespace System;
using namespace System::IO;
using namespace System::Security::Permissions;
using namespace System::Threading;

ref class ThreadPoolTest
{
private:

   // Maintains state information to be passed to EndWriteCallback.
   // This information allows the callback to end the asynchronous
   // write operation and signal when it is finished.
   ref class State
   {
   public:
      FileStream^ fStream;
      AutoResetEvent^ autoEvent;
      State( FileStream^ fStream, AutoResetEvent^ autoEvent )
      {
         this->fStream = fStream;
         this->autoEvent = autoEvent;
      }

   };


public:
   ThreadPoolTest(){}

   static void EndWriteCallback( IAsyncResult^ asyncResult )
   {
      Console::WriteLine( "Starting EndWriteCallback." );
      State^ stateInfo = dynamic_cast<State^>(asyncResult->AsyncState);
      int workerThreads;
      int portThreads;
      try
      {
         ThreadPool::GetAvailableThreads( workerThreads, portThreads );
         Console::WriteLine( "\nAvailable worker threads: \t{0}"
         "\nAvailable completion port threads: {1}\n", workerThreads.ToString(), portThreads.ToString() );
         stateInfo->fStream->EndWrite( asyncResult );
         
         // Sleep so the other thread has a chance to run
         // before the current thread ends.
         Thread::Sleep( 1500 );
      }
      catch ( Exception^ e ) 
      {
      }
      finally
      {
         
         // Signal that the current thread is finished.
         stateInfo->autoEvent->Set();
         Console::WriteLine( "Ending EndWriteCallback." );
      }

   }

   static void WorkItemMethod( Object^ mainEvent )
   {
      Console::WriteLine( "\nStarting WorkItem.\n" );
      AutoResetEvent^ autoEvent = gcnew AutoResetEvent( false );
      
      // Create some data.
      const int ArraySize = 10000;
      const int BufferSize = 1000;
      array<Byte>^byteArray = gcnew array<Byte>(ArraySize);
      (gcnew Random)->NextBytes( byteArray );
      
      // Create two files and two State objects. 
      FileStream^ fileWriter1 = gcnew FileStream(  "C:\\Test1@##.dat",FileMode::Create,FileAccess::ReadWrite,FileShare::ReadWrite,BufferSize,true );
      FileStream^ fileWriter2 = gcnew FileStream(  "C:\\Test2@##.dat",FileMode::Create,FileAccess::ReadWrite,FileShare::ReadWrite,BufferSize,true );
      State^ stateInfo1 = gcnew State( fileWriter1,autoEvent );
      State^ stateInfo2 = gcnew State( fileWriter2,autoEvent );
      
      // Asynchronously write to the files.
      fileWriter1->BeginWrite( byteArray, 0, byteArray->Length, gcnew AsyncCallback( &ThreadPoolTest::EndWriteCallback ), stateInfo1 );
      fileWriter2->BeginWrite( byteArray, 0, byteArray->Length, gcnew AsyncCallback( &ThreadPoolTest::EndWriteCallback ), stateInfo2 );
      
      // Wait for each callback to finish.
      autoEvent->WaitOne();
      autoEvent->WaitOne();
      fileWriter1->Close();
      fileWriter2->Close();
      Console::WriteLine( "\nEnding WorkItem.\n" );
      
      // Signal Main that the work item is finished.
      dynamic_cast<AutoResetEvent^>(mainEvent)->Set();
   }

};

int main()
{
   AutoResetEvent^ mainEvent = gcnew AutoResetEvent( false );
   int workerThreads;
   int portThreads;
   ThreadPool::GetMaxThreads( workerThreads, portThreads );
   Console::WriteLine( "\nMaximum worker threads: \t{0}"
   "\nMaximum completion port threads: {1}", workerThreads.ToString(), portThreads.ToString() );
   ThreadPool::GetAvailableThreads( workerThreads, portThreads );
   Console::WriteLine( "\nAvailable worker threads: \t{0}"
   "\nAvailable completion port threads: {1}\n", workerThreads.ToString(), portThreads.ToString() );
   ThreadPool::QueueUserWorkItem( gcnew WaitCallback( &ThreadPoolTest::WorkItemMethod ), mainEvent );
   
   // Since ThreadPool threads are background threads, 
   // wait for the work item to signal before ending main().
   mainEvent->WaitOne( 5000, false );
}

using System;
using System.IO;
using System.Security.Permissions;
using System.Threading;

class Test
{
    static void Main()
    {
        AutoResetEvent mainEvent = new AutoResetEvent(false);
        int workerThreads;
        int portThreads;

        ThreadPool.GetMaxThreads(out workerThreads, out portThreads);
        Console.WriteLine("\nMaximum worker threads: \t{0}" +
            "\nMaximum completion port threads: {1}",
            workerThreads, portThreads);

        ThreadPool.GetAvailableThreads(out workerThreads, 
            out portThreads);
        Console.WriteLine("\nAvailable worker threads: \t{0}" +
            "\nAvailable completion port threads: {1}\n",
            workerThreads, portThreads);

        ThreadPool.QueueUserWorkItem(new 
            WaitCallback(ThreadPoolTest.WorkItemMethod), mainEvent);
           
        // Since ThreadPool threads are background threads, 
        // wait for the work item to signal before ending Main.
        mainEvent.WaitOne(5000, false);
    }
}

class ThreadPoolTest
{
    // Maintains state information to be passed to EndWriteCallback.
    // This information allows the callback to end the asynchronous
    // write operation and signal when it is finished.
    class State
    {
        public FileStream     fStream;
        public AutoResetEvent autoEvent;

        public State(FileStream fStream, AutoResetEvent autoEvent)
        {
            this.fStream   = fStream;
            this.autoEvent = autoEvent;
        }
    }

    ThreadPoolTest() {}

    public static void WorkItemMethod(object mainEvent)
    {
        Console.WriteLine("\nStarting WorkItem.\n");
        AutoResetEvent autoEvent = new AutoResetEvent(false);

        // Create some data.
        const int ArraySize  = 10000;
        const int BufferSize =  1000;
        byte[] byteArray = new Byte[ArraySize];
        new Random().NextBytes(byteArray);

        // Create two files and two State objects. 
        FileStream fileWriter1 = 
            new FileStream(@"C:\Test1@##.dat", FileMode.Create, 
            FileAccess.ReadWrite, FileShare.ReadWrite, 
            BufferSize, true);
        FileStream fileWriter2 = 
            new FileStream(@"C:\Test2@##.dat", FileMode.Create, 
            FileAccess.ReadWrite, FileShare.ReadWrite, 
            BufferSize, true);
        State stateInfo1 = new State(fileWriter1, autoEvent);
        State stateInfo2 = new State(fileWriter2, autoEvent);

        // Asynchronously write to the files.
        fileWriter1.BeginWrite(byteArray, 0, byteArray.Length, 
            new AsyncCallback(EndWriteCallback), stateInfo1);
        fileWriter2.BeginWrite(byteArray, 0, byteArray.Length, 
            new AsyncCallback(EndWriteCallback), stateInfo2);

        // Wait for the callbacks to signal.
        autoEvent.WaitOne();
        autoEvent.WaitOne();

        fileWriter1.Close();
        fileWriter2.Close();
        Console.WriteLine("\nEnding WorkItem.\n");

        // Signal Main that the work item is finished.
        ((AutoResetEvent)mainEvent).Set();
    }

    static void EndWriteCallback(IAsyncResult asyncResult)
    {
        Console.WriteLine("Starting EndWriteCallback.");

        State stateInfo = (State)asyncResult.AsyncState;
        int workerThreads;
        int portThreads;
        try
        {
            ThreadPool.GetAvailableThreads(out workerThreads, 
                out portThreads);
            Console.WriteLine("\nAvailable worker threads: \t{0}" +
                "\nAvailable completion port threads: {1}\n",
                workerThreads, portThreads);

            stateInfo.fStream.EndWrite(asyncResult);

            // Sleep so the other thread has a chance to run
            // before the current thread ends.
            Thread.Sleep(1500);
        }
        finally
        {
            // Signal that the current thread is finished.
            stateInfo.autoEvent.Set();
            Console.WriteLine("Ending EndWriteCallback.");
        }
    }
}

Imports System.IO
Imports System.Security.Permissions
Imports System.Threading

Public Class Example
    Shared Sub Main()
        Dim mainEvent As New AutoResetEvent(False)
        Dim workerThreads As Integer 
        Dim portThreads As Integer 

        ThreadPool.GetMaxThreads(workerThreads, portThreads)
        Console.WriteLine(vbCrLf & "Maximum worker threads: " & _
            vbTab & "{0}" & vbCrLf & "Maximum completion port " & _
            "threads: {1}", workerThreads, portThreads)

        ThreadPool.GetAvailableThreads(workerThreads, portThreads)
        Console.WriteLine(vbCrLf & "Available worker threads: " & _
            vbTab & "{0}" & vbCrLf & "Available completion port " & _
            "threads: {1}" & vbCrLf, workerThreads, portThreads)

        ThreadPool.QueueUserWorkItem(AddressOf _
            ThreadPoolTest.WorkItemMethod, mainEvent)
           
        ' Since ThreadPool threads are background threads, 
        ' wait for the work item to signal before ending Main.
        mainEvent.WaitOne(5000, False)
    End Sub

End Class

Public Class ThreadPoolTest

    ' Maintains state information to be passed to EndWriteCallback.
    ' This information allows the callback to end the asynchronous
    ' write operation and signal when it is finished.
    Class State
        Public fStream As FileStream
        Public autoEvent As AutoResetEvent

        Public Sub New(aFileStream As FileStream, anEvent As AutoResetEvent)
            fStream   = aFileStream
            autoEvent = anEvent
        End Sub
    End Class   
    
    Private Sub New
    End Sub

    Shared Sub WorkItemMethod(mainEvent As Object)
    
        Console.WriteLine(vbCrLf & "Starting WorkItem." & vbCrLf)
        Dim autoEvent As New AutoResetEvent(False)

        ' Create some data.
        Const ArraySize As Integer  = 10000
        Const BufferSize As Integer =  1000
        Dim byteArray As Byte() = New Byte(ArraySize){}
        Dim randomGenerator As New Random()
        randomGenerator.NextBytes(byteArray)

        ' Create two files and two State objects. 
        Dim fileWriter1 As FileStream = _
            New FileStream("C:\Test1111.dat", FileMode.Create, _
            FileAccess.ReadWrite, FileShare.ReadWrite, _
            BufferSize, True)
        Dim fileWriter2 As FileStream = _
            New FileStream("C:\Test2222.dat", FileMode.Create, _
            FileAccess.ReadWrite, FileShare.ReadWrite, _
            BufferSize, True)
        Dim stateInfo1 As New State(fileWriter1, autoEvent)
        Dim stateInfo2 As New State(fileWriter2, autoEvent)

        ' Asynchronously write to the files.
        fileWriter1.BeginWrite(byteArray, 0, byteArray.Length, _
            AddressOf EndWriteCallback, stateInfo1)
        fileWriter2.BeginWrite(byteArray, 0, byteArray.Length, _
            AddressOf EndWriteCallback, stateInfo2)

        ' Wait for the callbacks to signal.
        autoEvent.WaitOne()
        autoEvent.WaitOne()

        fileWriter1.Close()
        fileWriter2.Close()
        Console.WriteLine(vbCrLf & "Ending WorkItem." & vbCrLf)

        ' Signal Main that the work item is finished.
        DirectCast(mainEvent, AutoResetEvent).Set()
    
    End Sub

    Shared Sub EndWriteCallback(asyncResult As IAsyncResult)
        Console.WriteLine("Starting EndWriteCallback.")

        Dim stateInfo As State = _
            DirectCast(asyncResult.AsyncState, State)
        Dim workerThreads As Integer 
        Dim portThreads As Integer 
        Try
            ThreadPool.GetAvailableThreads(workerThreads, portThreads)
            Console.WriteLine(vbCrLf & "Available worker " & _
                "threads:" & vbTab & "{0}" & vbCrLf & "Available " & _
                "completion port threads: {1}" & vbCrLf, _
                workerThreads, portThreads)

            stateInfo.fStream.EndWrite(asyncResult)

            ' Sleep so the other thread has a chance to run
            ' before the current thread ends.
            Thread.Sleep(1500)
        Finally
        
            ' Signal that the current thread is finished.
            stateInfo.autoEvent.Set()
            Console.WriteLine("Ending EndWriteCallback.")
        End Try
    
    End Sub
End Class

備註

傳回時 GetMaxThreads ，所 workerThreads 指定的變數包含執行緒集區中允許的背景工作執行緒數目上限，而所 completionPortThreads 指定的變數則包含執行緒集區中允許的非同步 I/O 執行緒數目上限。

您可以使用 GetAvailableThreads 方法來判斷線程集區中任何指定時間的實際執行緒數目。

您可以使用 SetMaxThreads 來設定執行緒集區中背景工作執行緒和非同步 I/O 執行緒的最大數目。

您可以將系統記憶體允許的執行緒集區要求排入佇列。如果要求數目超過執行緒集區執行緒，則其他要求會保持佇列，直到執行緒集區執行緒變成可用為止。

適用於

共用方式為

ThreadPool.GetMaxThreads(Int32, Int32) 方法

定義

參數

範例

備註

適用於

另請參閱

其他資源