One accurate measurement is worth a thousand expert opinions.
—Admiral Grace Murray Hopper
In their groundbreaking book Refactoring,1 Fowler and Beck tell a story of a slow performing system. All the experts gathered around to give their expert opinions on “what might be the cause.” Profiling pointed at something that none of them suspected in the least. This is a familiar problem; we have preconceptions. Tooling doesn’t. The reason for performance and memory problems often differs from our preconceived notions.
Profilers ...
