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Binding of device interrupts to particular processors on multiprocessor computers is a useful technique to maximize performance, scaling, and partitioning of large computers. Interrupt-Affinity Filter (IntFiltr) is an interrupt-binding tool that permits you to establish affinity for device processors on multiprocessor computers. IntFiltr uses Plug and Play features of Windows 2000 and provides a Graphical User Interface (GUI) to permit interrupt binding. This article describes how to install and use IntFiltr to permit a user to change the Central Processing Unit (CPU) on a single computer.
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
IntFiltr improves performance and scaling of large computers that contain multiple processors with partitioning and affinity for tasks to particular processors. When properly configured, the technique of partitioning permits caches on the processors to be used more effectively, thereby improving performance and scaling.
Windows 2000 contains many features that permit threads and processes to have affinity to particular processors. IntFiltr uses Plug and Play features of Windows 2000 that permits affinity for device interrupts to particular processors. You may configure IntFiltr to connect the filter driver to devices with interrupts and to set the affinity mask for the devices that have the filter driver associated with them.
IntFiltr permits an administrator to direct a device interrupt to a specific set of processors. On a Windows 2000-based multiprocessor computer, the interrupt controller directs the processor services a device interrupt to any available processor, which means an interrupt with the lowest interrupt request priority. By using IntFiltr, an administrator can choose to override the default behavior when they configure any set of processors as the target for the device interrupt. Typically, this would involve choosing a single processor to be the target.
Interrupt filtering can affect the overall performance of your computer. However, no single algorithm produces the best performance under all possible workloads. This is why Windows 2000, by default, directs interrupts to any available processor. An administrator, however, may be interested in partitioning interrupts for certain devices to particular processors or experimenting with various configurations to find out the optimal configuration. Note that this tool permits any configuration, even ones that are not optimal.
Because IntFiltr uses Plug and Play features of Windows 2000, IntFiltr cannot be used on Microsoft Windows NT, and it can only be used on devices that support Plug and Play. Also, IntFiltr should not be used on any device that shares interrupts with another device.
How to Install IntFiltr
How to Configure and Use IntFiltr
Even though all the computer devices appear in the Devices list, it only makes sense to install IntFiltr on devices that have interrupt resources. To see which devices have interrupt resources, use Device Manager, and then view resources by type.
Once configured, IntFiltr runs in the background with no interaction until it is reconfigured. Interrupt affinity settings made with IntFiltr are persistent between reboots, meaning that once an interrupt affinity mask is defined for a device, it remains associated with the device until the administrator changes it. If a device is associated with a processor that is being removed from the computer, the system administrator must update the affinity mask for the device before the processor is removed from the computer. Also, IntFiltr generally should not be used on any device that is sharing interrupts with another device.
Processor enumeration on computers that use hyperthreading first assign processor numbers to the primary logical processor for each processor and then assign numbers to the secondary. For example, for dual physical processor computers with hyperthreading, the first processor has logical processor 0 and 2, and the second processor has logical processor 1 and 3. The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.
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