It's exactly because the performance depends on the implementation details that when you understand implementation details, it can guide what you test and help find an optimization peak faster - or come up with a theory of another peak more distant, and journey through the performance valley to find it.
Implementation details follow the contours of the fundamental algorithms and data structures. You understand the outline of the implementation details - the bones, if you will - from that. And you can dive into the source (or disassembler - I've done that on Windows) to fine tune knowledge of other specifics, with e.g. gdb stack traces on the database engine when it is abnormally slow to focus attention.
Without having gone to battle together over some performance problems, or me writing significantly longer battle-story posts, we're probably not going to be able to communicate effectively here.
Implementation details follow the contours of the fundamental algorithms and data structures. You understand the outline of the implementation details - the bones, if you will - from that. And you can dive into the source (or disassembler - I've done that on Windows) to fine tune knowledge of other specifics, with e.g. gdb stack traces on the database engine when it is abnormally slow to focus attention.
Without having gone to battle together over some performance problems, or me writing significantly longer battle-story posts, we're probably not going to be able to communicate effectively here.