Processor Affinity

1. Processor Affinity

2. Excerpts from: Change the Processor Affinity setting in Windows 7 to gain a performance edge By Greg Shultz http://www.techrepublic.com /blog/window-on-windows/change-the-processor-affinity-setting-in-windows-7-to-gain-a-performance-edge/5322

3. Most applications you run these days have been designed with multi-core processors in mind and will work with the operating system to distribute their operations as evenly as possible across all the available cores. Older applications that were designed for single-core processors can behave irrationally — they may all of a sudden begin maxing out the CPU usage at 100 percent and appear to be locked up. In other circumstances, you might be able to achieve better overall performance from certain applications by configuring each of them to run on different processor cores.

4. From Task Manager Changing the Processor Affinity setting from within Task Manager is a pretty straightforward operation once you know how to do it. To launch Task Manger, you can use the keystroke combination [Ctrl] + [Shift] + [Esc] or you can simply right-click on the taskbar and select Task Manager from the context menu. Once Task Manager is up and running, select the Applications tab, right-click on the application that you want to work with, and select the Go to Process command, as shown. When you get to the Processes tab, right-click on the process and from that context menu, select the Set Affinity command. (If the processes are jumping around, it may be hard to select the correct process, so you might just want to press the Application key or [Shift]+[F10].)

5. After you select the Set Affinity command, you’ll see the Processor Affinity dialog box shown. As you can see, the default setting is All Processors, which in the case of my example system are CPU 0 and CPU 1. At this point, you can clear the All Processors check box and then select the CPU on which you want the process to run.

6. An example To take a look at the effects of using the Set Affinity command, I launched two applications: Microsoft Security Essentials and Disk Defragmenter. Next I used the Set Affinity command to assign Microsoft Security Essentials to CPU 0 and Disk Defragmenter to CPU 1. I then started each application running — Microsoft Security Essentials performing a full scan and Disk Defragmenter de-fragging a 500GB disk. Once each application began working, they started sucking up CPU time, so I went to the Performance tab in Windows Task Manager to look at the CPU Usage History graphs. When I did, I could see that each graph was showing different measurements, as shown .

7. To specifically see how each CPU core was faring, I launched Resource Monitor and selected the CPU tab. Again, I could see that each CPU core was showing different usage measurements, as shown.