Choosing a profiling mode in ANTS Performance Profiler 6 and 7

ANTS Performance Profiler offers up to five profiling modes. This technical paper discusses their uses and the differences between them.

The five profiling modes are:

Sample method-level timings (fastest, least detail, no hit counts)
Method-level timings; only methods with source (very fast, most accurate)*
Line-level and method-level timings; only methods with source (detailed)*
Method-level timings; all methods (faster)*
Line-level and method-level timings; all methods (most detailed)

(The profiling modes marked with an asterisk (*) in the list above are only available in ANTS Performance Profiler Professional.)

Each profiling mode involves a different amount of trade-off between the performance overhead introduced into your application (speed), the accuracy of the results provided and the amount of detail in the results.

The table below provides an overview of each profiling mode:

Profiling mode	Profiling type	Profiles individual lines of code?	Includes methods without source code?	Performance overhead added	SQL/ HTTP profiling (Pro only)	Accuracy	Detail
Line-level and method-level timings; all methods	Instrumented	Yes	Yes		Yes
Method-level timings; all methods	Instrumented	No	Yes		Yes
Line-level and method-level timings; only methods with source	Instrumented	Yes	No		Yes
Method-level timings; only methods with source	Instrumented	No	No		Yes
Sample method-level timings	Sampled	No	No		No

Sample method-level timings

In this mode, the profiler samples only the performance of your application. It introduces the least overhead but the results are not detailed. Because the mode uses sampling, ANTS Performance Profiler cannot count the number of times each method is hit.

Use sample method-level timings first if you have a complex application (a lot of different methods) which you need to run for a long time so that you can find out where the performance problem is. After you have identified the particular behavior which causes the problem, use one of the other modes to obtain detailed results.

Method-level timings; only methods with source

In this mode, the profiler profiles only methods that you have source code for, or methods from code decompiled using Red Gate's .NET Reflector VSPro edition. It records how many times each of these methods is hit but not how long it takes to execute each line within the methods. For this reason, it is faster than most other modes. This mode does not add much performance overhead to your application, and so the method-level timings are the most accurate.

Use method-level timings if you are certain that the performance problem is in one of your methods (or another method you have source code for) and if obtaining accurate timings is important to help you find the problem.

Line-level and method-level timings; only methods with source

This mode is the same as method-level timings; only methods with source, except that the profiler also records how long it takes each line of code within each method to execute. The advantage is that this mode can help you to identify exactly which line of code is causing the performance problem.

The disadvantage is that this mode reduces the performance of your application, causing it to run slower. This also means that the timings collected will be less accurate because by default the profiler estimates the overhead which it is adding to your application, and subtracts this from the recorded timings. For some very simple functions, this might mean that you see negative timings. (The estimate is most accurate for functions taking at least 1000 clock cycles.)

Method-level timings; all methods

This mode is the same as method-level timings; only methods with source except that all methods are included, even if you do not have source code for them. This mode is faster than the modes which include line-level timings but it is slightly slower than only profiling methods for which you have source code.

Use this mode if you are not sure whether the performance problem is caused by your code or some third-party code which you do not have source code for. This mode will also record timings for the .NET Framework's own methods.

Line-level and method-level timings; all methods

This mode records profiling results for every line of code in your application, even if you do not have source code for them. It gives you the most detail but it introduces a lot of overhead into your application and so the timings will not be accurate for the reasons described under line-level and method-level timings; only methods with source).

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