How to Make Things Faster

Chapter 78. The Evil Genie

One of the most insidious problems you can have is when something’s wrong, but your tools tell you everything’s fine. “My users must be happy, because my CPU utilization is in the green zone!” Well, that statement might sound sensible, but the “because” part just isn’t true. This problem is an example of a more general problem of surrogacy—it’s asking for something (green-zone CPU utilization) that’s not really the same as what you want (happy users).

To help me teach this lesson, I like to introduce my friend, the evil genie. Think of Elizabeth Hurley in Bedazzled, or just about any episode of The Twilight Zone. The formula is that you make a wish, and then the genie grants it—but it doesn’t turn out the way you want. For example, “I just want people to leave me alone,” makes you the sole survivor of a nuclear holocaust. That kind of thing.

The tools you use can trick you the same way, even when they’re not lying to you. They can do it simply by measuring the wrong things. The solution is straightforward: just be careful what you wish for. The test is to imagine “Could an evil genie grant my wish without giving me what I really want?” What you’re really asking is, “Could this measurement tool trick me into having false beliefs about my system?”

There are many ways a genie—or a well-intended measurement tool—can make an activity appear beneficial without actually accomplishing anything useful. Progress can be especially illusory when you’re working with ...