Performance regressing in Hyper-V guest system in Windows Server 2012 R2 or Windows 8.1

Applies to: Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials

This article describes an issue in which CPU cores cannot be unparked in Windows Server 2012 R2. An update and a hotfix are available to resolve this issue. The hotfix has a prerequisite.

Symptoms


This issue occurs on a common class of CPU intensive operations.

Cause


This issue occurs because parked CPU cores on non-uniform memory access (NUMA) node 0 cannot be unparked even if the Core Parking feature is disabled.

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 update, you must have update 2919355 installed in Windows 8.1 or Windows Server 2012 R2.

Registry information

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

Restart requirement

You may have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

Status


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

References


See the terminology that Microsoft uses to describe software updates.