I think performance is just a top priority as security, I remember how in their first whitepaper they already talked about how they batch up packets and stuff like that. Also the whole approach of kernelspace instead of userspace is just for performance.

Actually, I think in the beginning there was even a "marketing chart" with throughput numbers in addition to the chart with lines-of-code numbers?

Edit: performance being a top priority also makes sense strategically: if you want people to use secure software en-masse, then the experience needs to be stellar in UX and performance as well.