We should let the user specify, perhaps using a well known configuration attribute, what rules should be optimizing for. Sometimes it can be hard to evaluate a rule without, for example, knowing if the user desires lower latency over throughput.

I think it is not as easy as specifying a single target, rather an ordering of the characteristics that the user values the most.

For example, a user may find that latency is more important than throughput which he finds more important than memory usage (latency > throughput > memory usage).

For now, I think one way we could implement this is by providing a well known configuration attribute, and let the user set a global ordering. Each rule that supports the attribute, and which has not been overridden in preferences, would use the global ordering.

In the end we're probably going to enter machine learning territory.