With my own MaraDNS, I aggressively optimized the memory usage of blacklist entries by having a single really big malloc() to allocate the memory for the entries, then traversing that memory block for potentially blacklisted entries.

When I was using one malloc() per entry, a large blacklist took up 237 megabytes of memory. The same blacklist, once optimized to be loaded with a single malloc() call, only took up 9.5 megabytes of memory.

https://samboy.github.io/blog/entries/MaraDNS.html#BlogEntry...