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

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. 

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.

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.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows 8 and Windows Server 2012 file information notes

Important Windows 8 hotfixes and Windows Server 2012 hotfixes are included in the same packages. However, only "Windows 8" is listed on the Hotfix Request page. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 8" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

• The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:
  Collapse this tableExpand this table

  Version	Product	Milestone	Service branch
  6.2.920 0.16 xxx	Windows 8 and Windows Server 2012	RTM	GDR
  6.2.920 0.20 xxx	Windows 8 and Windows Server 2012	RTM	LDR

• GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.
• The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows 8 and Windows Server 2012" section. MUM and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows 8

For all supported x64-based versions of Windows 8 and of Windows Server 2012

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.

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

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

Additional file information

Additional file information for Windows 8 and Windows Server 2012

Additional files for all supported x86-based versions of Windows 8

Additional files for all supported x64-based versions of Windows 8 and of Windows Server 2012