In computer programming, instrumentation is the act of modifying software so that analysis can be performed on it.
Instrumentation enables profiling: [1] measuring dynamic behavior during a test run.
This is useful for properties of a program that cannot be analyzed statically with sufficient precision, such as performance and alias analysis.
For instance, if a word processor application is instrumented, but the user never activates the print feature, then the instrumentation can say nothing about the routines which are used exclusively by the printing feature.
Some types of instrumentation may cause a dramatic increase in execution time.