Copyright © 2005 Rick Kufrin
Originally published in Linux Journal (issue #135, July 2005).
At some point, all developers of software applications, whether targeted to Linux or not, are likely to spend at least a small amount of time focusing on the performance of their applications. The reason is simple: many potential benefits can be gained from tuning software for improved performance. For example, in the scientific and engineering arenas, performance gains can make the difference between running smaller scale simulations rather than larger and potentially more accurate models that would improve the scientific quality of the results. Applications that are more user-oriented also stand to benefit from improvements that result in faster responsiveness to the user and an improved overall user experience.
Although microprocessor improvements over the past decade or so have made clock speeds well in excess of the gigahertz range commonplace, most developers are aware that a tenfold increase in processor frequency does not guarantee a tenfold reduction in the run time of your application. Additionally, for those developing software for distribution to others, attention to performance and responsiveness can pay big dividends when you consider that your end user may be running your application on a mid-1990s era 100MHz Pentium processor.
This article is an introduction to a set of open-source software tools called PerfSuite that can help you to understand and possibly improve the performance of your application under Linux. PerfSuite consists of several related tools and libraries targeted at several different activities useful in performance-oriented analysis.
The development of PerfSuite was motivated by my own experiences in working with not only applications that I had developed, but a number of large supercomputer-class applications in both academic and corporate settings. After having worked with several research groups, I realized that developers often take advantage of a only limited set of tools that may be available to them. They typically rely on traditional time-based statistical profiling techniques such as gprof.
Of course, gprof-style profiles are invaluable and should be the mainstay of any developer's performance toolbox. However, the microprocessors of today, such as those on which you probably are using Linux, offer advanced features that can provide alternative insights into characteristics that directly affect the performance of your software. In particular, nearly all microprocessors in common use today incorporate hardware-based performance measurement support in their designs. This support can provide an alternative viewpoint of your software's performance. While time-based profiles tell you where your software spends its time, hardware performance measurements can help you understand what the processor is doing and how effectively the processor is being utilized. Hardware measurements also pinpoint particular reasons why the CPU is stalling rather than accomplishing useful work.
|Hardware Performance Counter Basics|