I did not delve into the details as you might have, but whenever I see mmap associated with huge perf I tend to wonder about corruption. I've seen to many bench comparing ondisk stores with in mmap stores flushed to disk one in a while. Then you need extra steps/configs to get good enough reliability that hinder perf.
>whenever I see mmap associated with huge perf I tend to wonder about corruption
If that was the case with lmdb implementation, that works as OpenLDAP backend all over the world, most probably you would have heard about it from the news.
