Analyze multiprocessor systems: CPU Migration pane

The CPU Migration pane provides a display that draws attention to some of the potential performance problems that are associated with multiple-CPU systems.

There are two migration details that are currently charted over the period of the log file:

• The upper part of the pane provides a display 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 areas where there's a high level of contention for particular CPUs. This type of cross-CPU migration can reduce performance because the instruction code cache is flushed, invalidated, and then reloaded on the new CPU.
• The lower part of the pane shows the count of cross-CPU 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 since the data that is associated with the message-pass can't be maintained in the processor data cache. The caches must be invalidated, as the data transfer is moved to the new CPU.