Chapter 2:

1. Performance measurements are needed for two main reasons. First, they are used to define targets and describe the current status; without such measurements, we cannot say whether performance is poor or excellent; neither can we judge whether the performance targets are met. Second, measurements are used to study the effects of various factors on performance, evaluate the results of code changes and other optimizations.
2. There is no single way to measure performance for all situations because there are usually too many contributing factors and causes to analyze using a single approach and because of the sheer volume of data that is needed to characterize the performance fully.
3. Benchmarking done by manual instrumentation of the code has the advantage that it can collect any data you want, and it is easy to put the data in context: for each line of code, you know what function or step of the algorithm it belongs to. The main limitation is in the invasive nature...