It's not 'your' code....

In many cases over 90% of the code running in a modern corporate Java application is not actually written by the principal developers but is rather "included" as part of containers vendor products, and OSS libraries.

This fact is directly related to the inability of many developers to understand and resolve poor performance.

Nobody can cold read this volume of code, it's impact with real data volumes at production transactions rates in a certain "(ab)use case" cannot be predicted theoretically.

The implicit trust we give to this code is quite amazing, if I ever get time I recount my .circumventBug2650 story.

Popular performance and profiling tools do a very bad job of exposing this behavior and promoting the understanding of this silent 90% majority. The traditional "plus.. plus... plus..." tree view cannot cope with the depth or the scale.

So when it comes to poor application performance it may not actually be our fault but rather a cumulative problem of layering other peoples code.