Examine CPU migration information
The CPU Migration pane provides a display that draws attention to some
of the potential performance problems associated with multiple CPU
systems. This is principally concerned with CPU migration activities.
The System Profiler's CPU Migration pane.
There are two migration details that are currently charted over the
period of the log file:
- The first chart 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 chart 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 second chart provides a display showing 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, and 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 where there are multiple CPUs.