Sampling
Sampling is a profiling technique that works without any modifications to your application. Rather than adding instrumentation calls to your code, the sampling profiler periodically suspends your application’s threads, reads their call stacks, and maps the captured addresses back to function names using the debug symbols your compiler already produces. The resulting data is fed into Qumulus the same way instrumentation data is, so the timeline and all other views work exactly as described in the Qumulus section.
Because sampling is statistical rather than exact, functions that execute very quickly and infrequently may not always show up. It is most effective for finding where the bulk of CPU time is being spent across a longer window of execution.