For Performance of Code

“During development sometimes developers argue that they are just adding a very small feature and it will take no time at all (especially if the feature

isn’t used). And then other developers on the same project make the same claim, and

suddenly the performance has regressed by a few percent. The cycle is repeated in the

next release, and now program performance has regressed by 10%. A couple of times

during the process, performance testing may hit some resource threshold—a critical

point in memory use, or a code cache overflow, or something like that. In those cases,

regular performance tests will catch that particular condition and the performance team

can fix what appears to be a major regression. But over time, as the small regressions

creep in, it will be harder and harder to fix them.”
- By Scott Oaks (Java Perfomrnace: The Definitive Guide )