Better linked-list traversal in BPF

Correct, so it would be faster on average, and a lot of the time the next location will be loaded whether or not it’s useful, regardless of list design — cache lines can only be loaded as a whole.

This isn’t a new approach, by the way. LISP famously uses lists a lot, and LISP machines needed to process them quickly. Even with memory latency at the time being much lower relative to CPU speeds, laying them out contiguously in memory was a standard trick. One way to do that is to use a copying garbage collector, which if coded correctly will automatically defragment the lists when they’re copied.