Unexplained slowness in SQL 2008 on Windows 2008 R2

A customer called today about an unexplained slowness in SQL Server 2008 on Windows 2008 R2.  All SQL data looked great, no blocking, no obvious IO bottlenecks, just overall slow performance.

976700  An application stops responding, experiences low performance, or experiences high privileged CPU usage if many large I/O operations are performed in Windows 7 or Windows Server 2008 R2
http://support.microsoft.com/default.aspx?scid=kb;EN-US;976700

As you can see in the Windows Performance Monitor graph, Processor(13)\% Privileged Time bouncing from 40%-100%.

We applied the latest Windows 2008 R2 Kernel (KB 2297652) and the customer’s SQL test script went from 10 minutes to 14 seconds!!!

We used the link below to download the most recent Windows 2008 R2 Kernel.  As with all hotfixes, you should 1) confirm you’re having these same symptoms, 2) verify the build matches your operating system version and 3) when possible, test before moving fix into production.

The Hyper-V-related services cannot start on a Windows Server 2008 R2-based computer that has many processor cores and many PCI MSI-X devices
http://support.microsoft.com/default.aspx?scid=kb;en-US;2297652