SRC Technical Note 1997-016
Continuous Profiling: Where Have All the Cycles Gone?
Jennifer M. Anderson, Lance M. Berc, Jeffrey Dean, Sanjay Ghemawat, Monika R.
Henzinger, Shun-Tak A. Leung, Richard L. Sites, Mark T. Vandevoorde, Carle A. Waldspurger,
William E. Weihl
Note #1997-016. July 28, 1997
This paper describes the DIGITAL Continuous Profiling Infrastructure, a sampling-based
profiling system designed to run continuously on production systems. The system supports
multiprocessors, works on unmodified executables, and collects profiles for entire
systems, including user programs, shared libraries, and the operating system kernel.
Samples are collected at a high rate (over 5200 samples/sec per 333-MHz processor), yet
with low overhead (1-3% slowdown for most workloads).
Analysis tools supplied with the profiling system use the sample data to produce an
accurate accounting, down to the level of pipeline stalls incurred by individual
instructions, of where time is being spent. When instructions incur stalls, the tools
identify possible reasons, such as cache misses, branch mispredictions, and functional
unit contention. The fine-grained instruction-level analysis guides users and automated
optimizers to the causes of performance problems and provides important insights for
fixing them.
Download note as:
|
