ProcessThread.ProcessorAffinity Property

Definition

Sets the processors on which the associated thread can run.

public:
 property IntPtr ProcessorAffinity {  void set(IntPtr value); };
[System.ComponentModel.Browsable(false)]
public IntPtr ProcessorAffinity { set; }
member this.ProcessorAffinity : nativeint
Public Property ProcessorAffinity As IntPtr

Property Value

An IntPtr that points to a set of bits, each of which represents a processor that the thread can run on.

Attributes

Exceptions

The processor affinity could not be set.

The process is on a remote computer.

Examples

The following example shows how to set the ProcessorAffinity property for an instance of Notepad to the first processor.

using System;
using System.Diagnostics;

namespace ProcessThreadIdealProcessor
{
    class Program
    {
        static void Main(string[] args)
        {
            // Make sure there is an instance of notepad running.
            Process[] notepads = Process.GetProcessesByName("notepad");
            if (notepads.Length == 0)
                Process.Start("notepad");
            ProcessThreadCollection threads;
            //Process[] notepads;
            // Retrieve the Notepad processes.
            notepads = Process.GetProcessesByName("Notepad");
            // Get the ProcessThread collection for the first instance
            threads = notepads[0].Threads;
            // Set the properties on the first ProcessThread in the collection
            threads[0].IdealProcessor = 0;
            threads[0].ProcessorAffinity = (IntPtr)1;
        }
    }
}
Imports System.Diagnostics



Class Program
    
    Shared Sub Main(ByVal args() As String) 
        ' Make sure there is an instance of notepad running.
        Dim notepads As Process() = Process.GetProcessesByName("notepad")
        If notepads.Length = 0 Then
            Process.Start("notepad")
        End If
        Dim threads As ProcessThreadCollection
        'Process[] notepads;
        ' Retrieve the Notepad processes.
        notepads = Process.GetProcessesByName("Notepad")
        ' Get the ProcessThread collection for the first instance
        threads = notepads(0).Threads
        ' Set the properties on the first ProcessThread in the collection
        threads(0).IdealProcessor = 0
        threads(0).ProcessorAffinity = CType(1, IntPtr)
    End Sub
End Class

Remarks

The processor affinity of a thread is the set of processors it has a relationship to. In other words, those it can be scheduled to run on.

ProcessorAffinity represents each processor as a bit. Bit 0 represents processor one, bit 1 represents processor two, and so on. The following table shows a subset of the possible ProcessorAffinity for a four-processor system.

Property value (in hexadecimal) Valid processors
0x0001 1
0x0002 2
0x0003 1 or 2
0x0004 3
0x0005 1 or 3
0x0007 1, 2, or 3
0x000F 1, 2, 3, or 4

You can also specify the single, preferred processor for a thread by setting the IdealProcessor property. A process thread can migrate from processor to processor, with each migration reloading the processor cache. Specifying a processor for a thread can improve performance under heavy system loads by reducing the number of times the processor cache is reloaded.

Applies to

See also