What I end up with is a 4 GB index, whose contents are byte offsets into an 8 GB file containing the properties of the edges. When I mmap these, an in-memory l

What I end up with is a 4 GB index, whose contents are byte offsets into an 8 GB file containing the properties of the edges. When I mmap these, an in-memory lookup takes about 1 ms, but I can have unfortunate delays of like 100 ms per lookup if I'm starting cold or hitting things that are swapped out of memory.