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CPU Settings for an Application Pool <cpu>

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Overview

The <cpu> element of the <add> element in the <applicationPools> collection configures values for CPU usage parameters and CPU actions that will be used in application pools.

NUMA Support

Non-Uniform Memory Access (NUMA) is a hardware-based method of associating processors to their own dedicated memory. NUMA is used to increase processor speed as an alternative to the traditional symmetric multiprocessor (SMP) model for multiprocessor support. You can set up IIS 8 and later to distribute and affinitize its processes on NUMA. The use of NUMA is configured in the CPU element by the numaNodeAssignment attribute that enables IIS to identify the most optimal NUMA node when the IIS worker process is about to start, and the numaNodeAffinityMode attribute that determines how the threads from an IIS worker process are affinitized to a NUMA node. NUMA is also configured using the MaxProcesses attribute of the processModel element, which when set to 0 specifies that IIS automatically runs the same number of worker processes as there are NUMA nodes. For more information, see IIS 8.0 Multicore Scaling on NUMA Hardware.

The NUMA selection logic and affinity type can be set in the Advanced Settings dialog box only if IIS is running on NUMA hardware.

Compatibility

Version Notes
IIS 10.0 The <cpu> element was not modified in IIS 10.0.
IIS 8.5 The <cpu> element was not modified in IIS 8.5.
IIS 8.0 Two enum values were added to the action attribute to define throttling behavior. The processorGroup attribute was added to define the number of processor groups used. The numaNodeAssignment and numaNodeAffinityMode attributes were added to specify the behavior of NUMA nodes.
IIS 7.5 The <cpu> element was not modified in IIS 7.5.
IIS 7.0 The <cpu> element was introduced in IIS 7.0.
IIS 6.0 The <cpu> element replaces portions of the IIS 6.0 IIsApplicationPools metabase property.

Setup

The <applicationPools> collection is included in the default installation of IIS 7 and later.

How To

How to edit CPU configuration settings

  1. Open Internet Information Services (IIS) Manager:

    • If you are using Windows Server 2012 or Windows Server 2012 R2:

      • On the taskbar, click Server Manager, click Tools, and then click Internet Information Services (IIS) Manager.

    • If you are using Windows 8 or Windows 8.1:

      • Hold down the Windows key, press the letter X, and then click Control Panel.
      • Click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.

    • If you are using Windows Server 2008 or Windows Server 2008 R2:

      • On the taskbar, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.

    • If you are using Windows Vista or Windows 7:

      • On the taskbar, click Start, and then click Control Panel.
      • Double-click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.

  2. In the Connections pane, expand the server name, click Application Pools, and then click the application pool that you want to edit.
    Screenshot of the Application Pools screen that populates from the Connections pane.

  3. In the Actions pane, click Advanced Settings...

  4. In the Advanced Settings dialog box, click the CPU property that you want to edit, then edit the value in the property value section of the dialog box, and then click OK. For example, you could change the Limit Action to NoAction, KillW3wp, Throttle, or ThrottleUnderLoad.
    Screenshot of the Advanced Settings dialog box's Throttle Under Load section.

How to configure IIS for use with Non-Uniform Memory Access (NUMA) hardware

  1. On the task bar, click Server Manager, click Tools, and then click Internet Information Services (IIS) Manager.

  2. In the Connections pane, expand the server name, and then click Application Pools.

  3. In the Application Pools pane, select the pool that you want to configure for NUMA.

  4. In the Actions pane, select Advanced Settings.

  5. Under Process Model, set Maximum Worker Processes to 0.

    Screenshot of the Process Model section with the Maximum Worker Processes field set to 0.

  6. Under CPU, set processorGroup, numaNodeAffinityMode, and numaNodeAssignment.

  7. Click OK.

Configuration

Attributes

Attribute Description
action Optional enum attribute. Configures the action that IIS takes when a worker process exceeds its configured CPU limit. The action attribute is configured on a per-application pool basis.

The action attribute can be one of the following possible values. The default value is NoAction.

Value Description
NoAction No action is taken when the CPU limit is exceeded. A warning is written to the event log.

The numeric value is 0.

KillW3wp Application pool worker processes that exceed their CPU limit will be forced to shut down.

The numeric value is 1.

Throttle The CPU consumption is limited to the value set in Limit. The Limit interval is not used and an event log entry is generated.

The numeric value is 2.

ThrottleUnderLoad The CPU consumption is limited only when there is contention on the CPU. The Limit interval is not used and an event log entry is generated.

The numeric value is 3.
limit Optional uint attribute. Configures the maximum percentage of CPU time (in 1/1000ths of one percent) that the worker processes in an application pool are allowed to consume over a period of time as indicated by the resetInterval attribute. If the limit set by the limit attribute is exceeded, an event is written to the event log and an optional set of events can be triggered. These optional events are determined by the action attribute.

Note: In IIS 8.5 and above, set limit in percent in the CPU pane of IIS Manager. In IIS 8.0, set limit in 1/1000ths of one percent in the CPU pane of IIS Manager. For both cases, the limit attribute in applicationHost.config is in 1/1000ths of one percent.

The default value is 0, which disables CPU limiting.
numaNodeAffinityMode Optional enum attribute. Specifies how the threads of a process that is affinitized to a NUMA node will be scheduled on the node's cores.

The numaNodeAffinityMode attribute can be one of the following possible values. The default value is Soft.

Value Description
Soft As long as the cores in a NUMA node to which a process is affinitized are available, all threads of the process will be scheduled on those cores. However, if the scheduler cannot schedule the process on the cores of the node that it is affinitized to, it can schedule the process on cores in another NUMA node.

The numeric value is 0.

Hard Any thread of a process that is affinitized to a NUMA node will be scheduled on the node's cores and only those cores. No threads of that process will be scheduled on cores in another NUMA node.

The numeric value is 1.
numaNodeAssignment Optional enum attribute. Specifies how IIS will determine which NUMA (non-uniform memory access) node to affinitize a process to. A NUMA node contains clusters of cores that share a single memory bank. This attribute is available in the CPU Advanced Settings only if NUMA nodes are available.

The numaNodeAssignment attribute can be one of the following possible values. The default value is Most Available Memory.

Value Description
Most Available Memory The process will be assigned to the NUMA node that has the most memory free.

The numeric value is 0.

Windows Scheduling Windows scheduling will determine which NUMA node the process is assigned to.

The numeric value is 1.
processorGroup Optional int attribute. The number of processor groups used (zero-based). A processor group contains multiple cores. The Processor Group attribute is available in the CPU Advanced Settings only if the server has multiple processor groups.

The default value is 0, which means that a single processor group is used.
resetInterval Optional timeSpan attribute. Specifies the reset period (in minutes) for CPU monitoring and throttling limits on an application pool. When the number of minutes elapsed since the last process accounting reset equals the number specified by this property, IIS resets the CPU timers for both the logging and limit intervals.

Important: The resetInterval value must be greater than the time between logging operations, otherwise IIS will reset counters before logging has occurred, and process accounting will not occur.

Note: Because process accounting in IIS uses Windows job objects to monitor CPU times for the whole process, process accounting will only log and throttle applications that are isolated in a separate process from IIS.

The default value is 00:05:00.
smpAffinitized Optional Boolean attribute. Specifies whether a particular worker process assigned to an application pool should also be assigned to a given CPU. This property is used together with the smpProcessorAffinityMask and smpProcessorAffinityMask2 attributes.

The default value is false.
smpProcessorAffinityMask Optional uint attribute. Specifies the hexadecimal processor mask for multi-processor computers, which indicates to which CPU the worker processes in an application pool should be bound. Before this property takes effect, the smpAffinitized attribute must be set to true for the application pool.

Note: On 64-bit computers, the smpProcessorAffinityMask attribute contains the low-order DWORD for the processor mask, and the smpProcessorAffinityMask2 attribute contains the high-order DWORD for the processor mask. On 32-bit computers, the smpProcessorAffinityMask2 attribute has no effect.

If you set the value to 1 (which corresponds to 00000000000000001 in binary), the worker processes in an application pool run on only the first processor. If you set the value to 2 (which corresponds to 0000000000000010 in binary), the worker processes run on only the second processor. If you set the value to 3 (which corresponds to 0000000000000011 in binary) the worker processes run on both the first and second processors.

Note: Do not set this property to 0. Doing so disables symmetric multiprocessing (SMP) affinity and creates an error condition. This means that processes running on one CPU will not remain affiliated with that CPU throughout their lifetime.

The default value is 4294967295.
smpProcessorAffinityMask2 Optional uint attribute. Specifies the high-order DWORD hexadecimal processor mask for 64-bit multi-processor computers, which indicates to which CPU the worker processes in an application pool should be bound. Before this property takes effect, the smpAffinitized attribute must be set to true for the application pool.

Note: On 64-bit computers, the smpProcessorAffinityMask attribute contains the low-order DWORD for the processor mask, and the smpProcessorAffinityMask2 attribute contains the high-order DWORD for the processor mask. On 32-bit computers, the smpProcessorAffinityMask2 attribute has no effect.

The default value is 4294967295.

Child Elements

None.

Configuration Sample

The following configuration sample configures a single application pool named DefaultAppPool and sets the CPU to 50%, with an action to kill the worker process with a reset interval of 10 minutes.

<applicationPools>
   <add name="DefaultAppPool">
     <cpu limit="50000" action="KillW3wp" resetInterval="00:10:00" />
   </add>
   <applicationPoolDefaults>
     <processModel identityType="NetworkService" />
   </applicationPoolDefaults>
</applicationPools>

Sample Code

The following code samples configure the default application pool to kill the worker process when it exceeds the CPU limit, and configure the reset interval to four minutes.

AppCmd.exe

appcmd.exe set config -section:system.applicationHost/applicationPools /[name='DefaultAppPool'].cpu.action:"KillW3wp" /commit:apphost

appcmd.exe set config -section:system.applicationHost/applicationPools /[name='DefaultAppPool'].cpu.resetInterval:"00:04:00" /commit:apphost

Note

You must be sure to set the commit parameter to apphost when you use AppCmd.exe to configure these settings. This commits the configuration settings to the appropriate location section in the ApplicationHost.config file.

C#

using System;
using System.Text;
using Microsoft.Web.Administration;

internal static class Sample
{
   private static void Main()
   {
      using (ServerManager serverManager = new ServerManager())
      {
         Configuration config = serverManager.GetApplicationHostConfiguration();
         ConfigurationSection applicationPoolsSection = config.GetSection("system.applicationHost/applicationPools");
         ConfigurationElementCollection applicationPoolsCollection = applicationPoolsSection.GetCollection();
         ConfigurationElement addElement = FindElement(applicationPoolsCollection, "add", "name", @"DefaultAppPool");

         if (addElement == null) throw new InvalidOperationException("Element not found!");

         ConfigurationElement cpuElement = addElement.GetChildElement("cpu");
         cpuElement["action"] = @"KillW3wp";
         cpuElement["resetInterval"] = TimeSpan.Parse("00:04:00");

         serverManager.CommitChanges();
      }
   }

   private static ConfigurationElement FindElement(ConfigurationElementCollection collection, string elementTagName, params string[] keyValues)
   {
      foreach (ConfigurationElement element in collection)
      {
         if (String.Equals(element.ElementTagName, elementTagName, StringComparison.OrdinalIgnoreCase))
         {
            bool matches = true;
            for (int i = 0; i < keyValues.Length; i += 2)
            {
               object o = element.GetAttributeValue(keyValues[i]);
               string value = null;
               if (o != null)
               {
                  value = o.ToString();
               }
               if (!String.Equals(value, keyValues[i + 1], StringComparison.OrdinalIgnoreCase))
               {
                  matches = false;
                  break;
               }
            }
            if (matches)
            {
               return element;
            }
         }
      }
      return null;
   }
}

VB.NET

Imports System
Imports System.Text
Imports Microsoft.Web.Administration

Module Sample
   Sub Main()
      Dim serverManager As ServerManager = New ServerManager
      Dim config As Configuration = serverManager.GetApplicationHostConfiguration
      Dim applicationPoolsSection As ConfigurationSection = config.GetSection("system.applicationHost/applicationPools")
      Dim applicationPoolsCollection As ConfigurationElementCollection = applicationPoolsSection.GetCollection
      Dim addElement As ConfigurationElement = FindElement(applicationPoolsCollection, "add", "name", "DefaultAppPool")

      If (addElement Is Nothing) Then
         Throw New InvalidOperationException("Element not found!")
      End If

      Dim cpuElement As ConfigurationElement = addElement.GetChildElement("cpu")
      cpuElement("action") = "KillW3wp"
      cpuElement("resetInterval") = TimeSpan.Parse("00:04:00")

      serverManager.CommitChanges()
   End Sub

   Private Function FindElement(ByVal collection As ConfigurationElementCollection, ByVal elementTagName As String, ByVal ParamArray keyValues() As String) As ConfigurationElement
      For Each element As ConfigurationElement In collection
         If String.Equals(element.ElementTagName, elementTagName, StringComparison.OrdinalIgnoreCase) Then
            Dim matches As Boolean = True
            Dim i As Integer
            For i = 0 To keyValues.Length - 1 Step 2
               Dim o As Object = element.GetAttributeValue(keyValues(i))
               Dim value As String = Nothing
               If (Not (o) Is Nothing) Then
                  value = o.ToString
               End If
               If Not String.Equals(value, keyValues((i + 1)), StringComparison.OrdinalIgnoreCase) Then
                  matches = False
                  Exit For
               End If
            Next
            If matches Then
               Return element
            End If
         End If
      Next
      Return Nothing
   End Function


End Module

JavaScript

var adminManager = new ActiveXObject('Microsoft.ApplicationHost.WritableAdminManager');
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST";
var applicationPoolsSection = adminManager.GetAdminSection("system.applicationHost/applicationPools", "MACHINE/WEBROOT/APPHOST");
var applicationPoolsCollection = applicationPoolsSection.Collection;
var addElementPos = FindElement(applicationPoolsCollection, "add", ["name", "DefaultAppPool"]);

if (addElementPos == -1) throw "Element not found!";

var addElement = applicationPoolsCollection.Item(addElementPos);
var cpuElement = addElement.ChildElements.Item("cpu");
cpuElement.Properties.Item("action").Value = "KillW3wp";
cpuElement.Properties.Item("resetInterval").Value = "00:04:00";

adminManager.CommitChanges();

function FindElement(collection, elementTagName, valuesToMatch) {
   for (var i = 0; i < collection.Count; i++) {
      var element = collection.Item(i);
      if (element.Name == elementTagName) {
         var matches = true;
         for (var iVal = 0; iVal < valuesToMatch.length; iVal += 2) {
            var property = element.GetPropertyByName(valuesToMatch[iVal]);
            var value = property.Value;
            if (value != null) {
               value = value.toString();
            }
            if (value != valuesToMatch[iVal + 1]) {
               matches = false;
               break;
            }
         }
         if (matches) {
            return i;
         }
      }
   }
   return -1;
}

VBScript

Set adminManager = WScript.CreateObject("Microsoft.ApplicationHost.WritableAdminManager")
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST"
Set applicationPoolsSection = adminManager.GetAdminSection("system.applicationHost/applicationPools", "MACHINE/WEBROOT/APPHOST")
Set applicationPoolsCollection = applicationPoolsSection.Collection
addElementPos = FindElement(applicationPoolsCollection, "add", Array("name", "DefaultAppPool"))

If (siteElementPos = -1) Then
   WScript.Echo "Element not found!"
   WScript.Quit
End If

Set addElement = applicationPoolsCollection.Item(addElementPos)
Set cpuElement = addElement.ChildElements.Item("cpu")
cpuElement.Properties.Item("action").Value = "KillW3wp"
cpuElement.Properties.Item("resetInterval").Value = "00:04:00"

adminManager.CommitChanges()

Function FindElement(collection, elementTagName, valuesToMatch)
   For i = 0 To CInt(collection.Count) - 1
      Set element = collection.Item(i)
      If element.Name = elementTagName Then
         matches = True
         For iVal = 0 To UBound(valuesToMatch) Step 2
            Set property = element.GetPropertyByName(valuesToMatch(iVal))
            value = property.Value
            If Not IsNull(value) Then
               value = CStr(value)
            End If
            If Not value = CStr(valuesToMatch(iVal + 1)) Then
               matches = False
               Exit For
            End If
         Next
         If matches Then
            Exit For
         End If
      End If
   Next
   If matches Then
      FindElement = i
   Else
      FindElement = -1
   End If
End Function