Select "Kernel Blocking Times" in the View menu to display all blocking kernel service calls in a plot. By blocking time, we mean the time between entry and return of blocking calls. Each data point represents a specific kernel service call, where the x-position indicates the point in time and the y-position the blocking time. Clicking a data point (a service call) will highlight it in the trace view. This can be used to identify unintentional blocking, e.g., on a Mutex, which could be a cause behind unusually high response times of tasks.
You can combine this view with other horizontal views by choosing Views -> Add -> (graph type).