Spotlight on Oracle 11.0 - Getting Started Guide

The Processes Page And Process Affinity

In Windows systems where there are multiple processors, an activity (thread) in a process can migrate from processor to processor – and every migration reloads the processor cache.

Process affinity, which you can set on the target Windows machine via the Windows Task Manager, allows you to establish an association that permits specified processes to run ONLY on nominated processors. This limits the number of cache reloads, which may be desirable on systems operating under heavy load.

You CANNOT set process affinity via Spotlight on Windows.

What you CAN do is:

Use the Processes drilldown to indicate the CPUs where the specified process is permitted to run. This enables Spotlight to report the CPU usage for that process with accuracy.

Example: Running a process on an eight-CPU system

Spotlight uses the Windows Performance Monitor (PerfMon) to retrieve important data from target Windows systems, including the total percentage of CPU usage by specified processes.

On a single-CPU system, PerfMon can report a maximum CPU usage of 100%.

On a multiple-CPU system, that maximum value is multiplied by the number of CPUs. For an eight-CPU system, PerfMon can report a maximum CPU usage of 800%. Spotlight on Windows compensates by dividing the reported PerfMon value by the number of CPUs on the system.

However, when the affinity for a process is set so that it can run only on two nominated CPUs of the eight available, the default Spotlight calculation fails. For example, if PerfMon reports a CPU usage of 120% for the process (corresponding to a 60% usage on each permitted CPU), Spotlight initially calculates a value of 15%. Use Spotlight's Configure Affinity function to adjust the Spotlight calculation. Processes Page

How to set process affinity

Process affinity can be set via the Windows Task Manager on Windows machines that have multiple CPUs.

1. Log in to the monitored Windows machine.
2. Press CTRL+ALT+DEL.
3. Click Task Manager | Processes.

4. Right-click the name of the process whose affinity you want to set and select Set Affinity.

   Note: This option is unavailable when the system has one CPU.

5. Select which of the available CPUs you want to use for the process.

Note: You can also set process affinity for Microsoft SQL Server through the SQL Server Enterprise Manager.

Related Topics

Processes Page

Troubleshooting Spotlight on Windows