This shows the combined rate at which all processors on the computer are switched from one thread to another.
Context switches occur when a thread is “bumped” or voluntarily relinquishes control of a processor - that is, the context of a processor switches to another process.
High context switching can be bad for the following reasons:
- Switching a thread off one processor may mean it starts rerunning on another processor (on a multiprocessor system). This can mean that data held in L2 cache (or L3 cache) may be defunct, forcing the application thread to go to standard RAM to retrieve data.
- High context switching may indicate that threads are being blocked (and therefore relinquishing control of a processor). The ideal on a multiprocessor system is to have as each processor busy running separate threads at all times; context switching can add overhead and indicate an inefficient use of the multiprocessor system by an application.