[skywhopper]

There's some some waste involved in not pre-allocating the map to begin with. Check the output of this variation (https://go.dev/play/p/vQwg3GajzXx -- n shrunk to 1,000 to stay within the playground's memory constraints) which fills the map again after the GC. You'll see the map doesn't grow back to the max size.

And if you specify the size of the map up front in the `make()` function, it never grows or shrinks (or not significantly): https://go.dev/play/p/AGW35kMMOc5

IIRC, what's happening is that whenever the map hits what was pre-allocated, it expands by a certain growth factor of the current size. So at some point between 1 and 1,000,000 a big chunk was allocated that went over what was necessary for 1,000,000 entries. In my testing it happened around i == 851_500:

   i == 851000: 258507 KB
   i == 852000: 479212 KB

[SeanLuke]

Hashtables often treble when they reach 50% utilization. I think I'm already factoring that in. It's still 100 bytes overhead!