Context Switches

A Context Switch stores the state of a process or a thread, so it can be restored and resume execution at a later point. When attempting to profile Context Switches with a Launcher Build, You will want to ensure that you enable "Editor Symbols for Debugging" from the Options for your Engine Version.

1. You can enable the ContextSwitch trace channel in the command line:

   -trace=default,ContextSwitch

   On Windows, depending on your user permission settings your project runtime should be "run as administrator".

2. Open your trace file in Unreal Insights, If a session has the ContextSwitch trace event enabled, then the following information will be displayed in the Timing Insights view:

a) Additional CPU Core tracks. One for each CPU core in the recorded trace; shows timing events indicating what thread does execute on the respective CPU core. "Unknown" timing events indicate execution of threads from other applications / processes or from the OS.

b) Each CPU Thread has a header lane with core number events indicating on which core the respective thread is executing. The time range when a thread is executing and when it is preempted it is highlighted.

c) CPU/GPU drop down menu shows additional options re Context Switches:

d). The context menu of a "Core" timing event in a Cpu Thread track shows additional options:

e). The context menu of a "Thread" timing event in a CPU Core track shows additional options: