There are some interesting changes in jemalloc. We should review our PooledByteBufAllocator and see if we can incorporate some stuff as it was written with jemalloc 3 in mind.

See also:
https://www.youtube.com/watch?v=RcWp5vwGlYU
https://github.com/jemalloc/jemalloc/blob/dev/ChangeLog
https://github.com/jemalloc/jemalloc/milestones/4.0.0