All you need to know about Citrix CPU Utilization Management


Citrix CPU Utilization is a cool technology but there are a lot of confusion around it on how to successfully use and implement it.  Here is a summary on how to enable it in  Citrix environments.

Citrix CPU Management

cannot operate correctly when Microsoft’s Fair Share Scheduling (DFSS) is enabled. Citrix CPU Management services therefore check the status of DFSS before starting. If DFSS is found to be enabled, then the Citrix CPU Management services will not start and will instead write the following error event to the Windows Application Log
Source: CTXCPUUtilMgmt
Description: The Dynamic Fair Share Scheduling (DFSS) aspect of the Remote Desktop Services role is currently enabled. CPU Utilization Management does not operate correctly when DFSS is enabled, so CPU Utilization Management has stopped. Before using CPU Utilization Management, disable DFSS. For instructions on how to disable DFSS, see help for Microsoft Remote Desktop Services or Citrix XenApp.DFSS may be configured via Group Policy or via a dedicated registry key. When DFSS is configured via Group Policy, the dedicated DFSS registry key has no effect.The DFSS Group Policy setting is “Turn off Fair Share CPU Scheduling” and this setting is under the following GP node:
Computer Configuration
-> Administrative Templates
-> Windows Components
-> Remote Desktop Services
-> Remote Desktop Session Host
->ConnectionsThe dedicated DFSS registry key is:
Key name: HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Quota System
Value name: EnableCpuQuota
Value meaning: A value of 0, is used to disable DFSS. A value of 1 is used to enable DFSS.

If the “Turn off Fair Share CPU Scheduling” GP setting is not configured then Citrix CPU Utilization Management determines the status of DFSS via the dedicated DFSS registry key.

If the “Turn off Fair Share CPU Scheduling” GP setting is enabled then Citrix CPU Utilization Management assumes the DFSS is disabled, the dedicated DFSS registy key is ignored and the Citrix CPU Utilization Management services will start.

If the “Turn off Fair Share CPU Scheduling” GP setting is disabled then Citrix CPU Utilization Management assumes the DFSS is enabled, the dedicated DFSS registy key is ignored and the Citrix CPU Utilization Management services will not start.

Unfortunately there is one complication in all the the above, see Microsoft TechNet articale “Group Policy to disable DFSS is not functional” found at “http://technet.microsoft.com/en-us/library/ee808941(WS.10).aspx”. DFSS should therefore not be configured via Group Policy, and should instead be configured by the dedicated DFSS registry key. This is also discussed in Citrix Knowledge Base article CTX127135 “http://support.citrix.com/article/ctx127135”.

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