And logrus is one of the slowest loggers by far, in part because of its heavy map usage.

It's also the reflect on the value part which slows down things. It could be improved but it's hard to do that without breaking interface. It's so widely used that a major bump wouldn't that useful.

I'd expect it to be mostly called on map literals, at least a compile time constant set of keys. That should be amenable to a targeted compiler optimisation.