In the System Profiler editor, the CPU Migration pane displays data that helps you find
potential performance problems in multiple-CPU systems.
There are two migration details that are charted throughout the log file period:
- The upper part of the pane displays a graph showing the number of CPU-scheduling migrations over time. The count is incremented each time a thread switches CPUs. The peaks in this graph indicate times with a high level of contention for particular CPUs. This type of cross-CPU migration can reduce performance because the instruction cache is flushed, invalidated, and then reloaded on the new CPU.
- The lower part of the pane shows the count of cross-CPU message communication, where the sending client thread and the receiving server thread are running on different CPUs. This type of cross-CPU communication on the initial message-sends is a potential performance problem because the data associated with the message-pass can't be maintained in the data cache. The caches must be invalidated, as the data transfer is moved to the new CPU.
This pane contains valid data only when the log file contains events from a system with multiple CPUs.