Incorrect RSS processor assignment on a Windows 8 or Windows Server 2012-based computer that has multi-core processors

Applies to: Windows 8Windows 8 EnterpriseWindows 8 Pro

Symptoms


Consider the following scenario:
  • You have a Windows 8-based or Windows Server 2012-based computer that has multi-core processors.
  • You have three or more network adapters installed on the computer. 
  • You enable Receive Side Scaling (RSS) and set a RSS profile to use the "Closest" parameter for the network adapters.
  • You run the following PowerShell command to retrieve RSS properties of the network adapters:
    Get-NetAdapterRss 
In this scenario, the first two network adapters are assigned processors correctly. However, other network adapters are not assigned correctly. 

Cause


This issue occurs because RSS incorrectly uses the maximum processor count that is supported by the computer to assign processors. The expected action is that RSS uses the active processor count during the processor assignment.

Resolution


Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must be running Windows 8 or Windows Server 2012.

Registry information

To use the hotfix in this package, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

Workaround


To work around the issue, set the RSS profile to use the "NUMAStatic" parameter. However, computer performance drops 5% to 8% by using this configuration.

Status


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information


For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates