The Sampling profiler takes samples at regular time intervals and determines which routines (lines) are being executed in the application. This profiler is less accurate, but it's very fast compared to the Performance profiler. Since the Sampling profiler does not significantly reduce the application performance, it can be used with the All Project Modules option enabled to quickly isolate problematic areas in large applications. Once poorly performing areas are found, further optimization can be initiated and performed via the Performance profiler.
This tutorial demonstrates how you can use the Sampling profiler to estimate the performance of your applications.