I've noticed a few places calling __wt_random in a loop with repeated probabilites, to produce a logrithmic distribution. But that can be done more efficiently by taking the 32 bits returned and running them through count leading/trailing zeros/ones (doesn't matter which of the 4 combinations), which has an equivalent probability function to flipping a coin up to 32 times and counting the number of heads in a row (stopping at the first tails).

For example, the code to choose a skiplist depth with probablity 1/4 of going deeper, could be just tmp = count_leading_zeros(_wt_random()); depth = min((tmp / 2) +1, 10);. And this code to pick a random sleep bucket could just be i = min(count_leading_zeros(_wt_random()), max);.