Tracing is one of the CPU profiling modes.
When tracing is used, the profiler instruments the bytecode of the profiled application for recording time spent inside each profiled method. Both times and invocation counts are available.
Use profiler toolbar to start CPU tracing as shown on the picture below. There are also alternate methods to start CPU profiling.
Although tracing provides more information, it has its drawbacks. First, it may noticeably slow down the profiled application, because the profiler executes special code on each enter to and exit from the methods being profiled. The greater the number of method invocations in the profiled application, the lower its speed when tracing is turned on.
The second drawback is that, since this mode affects the execution speed of the profiled application, the times recorded in this mode may be less adequate than times recorded with sampling. Please use this mode only if you really need method invocation counts.
Also, the probes for the high-level statistics, if enabled, may impose additional overhead.
See also: Profiling overhead: how to reduce or avoid.
To control profiling overhead and accuracy of the results use CPU tracing settings.