Hi Rob, thanks much for your report and questions!
You are correct that knotc is waiting for knotd to perform the zone addition/removal during conf-commit.
This operation (performed by knotd) is single-threaded, therefore the measured load on your multi-CPU-core machine might not seem utilized. Could you please confirm that one CPU core is running on 100% during the commit?
It is true that some operations modifying the set of configure zones lead to complete re-build of the zone tree, therefore the time needed depends of the total number of zones, even when they are otherwise unaffected. Daniel already told that he will check if/why this is also the case.
Anyway, are 2 seconds really that bad? It seems nice to me :) If many zones are casually added/removed in your setup every minute, it would be wise to group them into batches -- not only for performance/timing reasons. Could you please confirm that adding/removing for example 100 zones takes roughly the same time?
By the way, we would love to hear about any other challenges/bottlenecks in your setup.
Libor --
