An Extended GPROF Profiling and Tracing Tool for Enabling Feedback-Directed Optimizations of Multithreaded Applications

This paper presents an approach for profiling and tracing multithreaded applications with two main objectives. First, extend the positive points and overcome the limitations of GPROF tool when used on parallel applications. Second, focus on gathering information that can be useful for extending the existing GCC profile-driven optimizations and to investigate on new ones for parallel applications. In order to perform an insightful profiling of a multithreaded application, our approach proposes to gather intra-thread together with inter-thread information. For the latter, Operating System activity, as well as the usage of programmer-level synchronization mechanisms (e.g., semaphores, mutex), have to be taken into account. The proposed approach exposes various per-thread information like the call-graph, and a number of intra-thread ones like blocking relationship between threads, blocking time, usage patterns of synchronization mechanisms, context switches. The approach introduces a relatively low overhead which makes it widely applicable: less than 9 % on test multithreaded benchmarks and less than 3.9x slowdown for the real MySQL executions. 1 Intro and motivatio