FIX: CPU utilization increases and throughput decreases when you run a heavy OLTP workload on an instance of SQL Server 2005 on a computer that has more than 32 processors

You run an instance of Microsoft SQL Server 2005 on a computer that has more than 32 processors. When the OLTP workload is heavy, you may notice that the CPU utilizations for all processors increase. Additionally, the Batch Requests/sec counter of the SQL Server:SQL Statistics performance object indicates that the throughput decreases.

If you run the following statement, you notice that there are many rows that have RESOURCE_SEMAPHORE_MUTEX in the wait_type column:If you run the following statement, you notice the following results:

• There are many sessions that are waiting for memory grants.
• The value of the grant_time column is null.

Note This issue may also occur even when queries only try to obtain the minimum memory that you specify in the min memory per query option.

This issue occurs because of a contention on the memory grant resource semaphore among concurrent queries. The number of concurrent queries depends on the number of available CPUs.

The fix for this issue was first released in Cumulative Update 9. For more information about how to obtain this cumulative update package for SQL Server 2005 Service Pack 2, click the following article number to view the article in the Microsoft Knowledge Base:Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2005 fix release. Microsoft recommends that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:Microsoft SQL Server 2005 hotfixes are created for specific SQL Server service packs. You must apply a SQL Server 2005 Service Pack 2 hotfix to an installation of SQL Server 2005 Service Pack 2. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.

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

To enable this hotfix, you must enable trace flag 2456 for the instance.

For more information about what files are changed, and for information about any prerequisites to apply the cumulative update package that contains the hotfix that is described in this Microsoft Knowledge Base article, click the following article number to view the article in the Microsoft Knowledge Base:

For more information about the list of builds that are available after SQL Server Service Pack 2, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the Incremental Servicing Model for SQL Server, click the following article number to view the article in the Microsoft Knowledge Base:For more information about how to obtain SQL Server 2005 Service Pack 2, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the new features and the improvements in SQL Server 2005 Service Pack 2, visit the following Microsoft Web site: For more information about the naming schema for SQL Server updates, click the following article number to view the article in the Microsoft Knowledge Base:For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: