Multi-threaded CPU bound applications is lower. The main benefit is that there is no safe-point bias with this sampling method and the overhead for highly The profiling agent then inspects the native stack and extracts the Java stack frames. With async sampling, a profiling signal handler is called on the running To help with getting accurate numbers for highly CPU bound code, JProfiler also offers async On the other hand, if code also performs significant I/O, this bias will generally not be a problem. Multi-threaded CPU bound code, the profiled distribution of hotspots may be skewed significantly. The JVM only pauses threads at certain "safe points" thereby introducing a bias. With a separate thread that pauses all threads in the JVM periodically and inspects their stack traces. JProfiler offers two different technical solutions for sampling: "Full sampling" is done Method A X: 3.5 ms Y: 4.5 ms time in ms Profiling agent entry entry entry exit exit exit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Method B: 11 ms calls calls calls Full sampling versus async sampling This does not matter if you are looking for performance bottlenecks,īut can be inconvenient if you are trying to understand the detailed runtime characteristics of your code. Additionally, short running methods that areĬalled only a few times might not show up at all. The downside is that you cannot determine any method invocation counts. No bytecode has to be modified and the sampling period is much larger than the typical duration of a method call. The advantage of sampling is that it hasĪ very low overhead because it happens infrequently. With a large number of samples, a statistically correct picture emerges. When processing sampling data, the full sampling period (typically 5 ms) is attributed to the sampled call stack. Produce invocation counts for all methods. Instrumentation measures all invocations and can With instrumentation, the bytecode of selectedĬlasses is modified to trace method entry and exit. "sampling" and "instrumentation", each of which has advantages and drawbacks: With sampling, the currentĬall stacks of threads are inspected periodically. Measuring method calls can be done with two fundamentally different techniques called To make a decision on which method to use. Measurement that fulfills all these requirements for all types of applications. Unfortunately, there is no single type of Recording method calls is is one of the most difficult tasks for a profiler, because it operates underĬonflicting constraints: Results should to be accurate, complete and produce such a small overhead that theĬonclusions you draw from the measured data do not become incorrect.
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