Efficient and Flexible Value Sampling



Mike Burrows, Ulfar Erlingson, Shun-Tak A. Leung, Mark T. Vandevoorde,

Carl A.  Waldspurger, Kevin Walker, William E. Weihl



August 30, 2000





This paper presents novel sampling-based techniques for collecting

statistical profiles of register contents, data values, and other

information associated with instructions, such as memory latencies.

Values of interest are sampled in response to periodic interrupts.

The resulting value profiles can be analyzed by programmers and

optimizers to improve the performance of production uniprocessor and

multiprocessor systems.



Our value sampling system extends the DCPI continuous profiling

infrastructure, and inherits many of its desirable properties: our value

profiler has low overhead (approximately 10\% slowdown); it profiles all the

code in the system, including the operating system kernel; and it operates

transparently, without requiring any modifications to the profiled

code.