I think we need to backport r58874 to 2.4. Can you file a
backport ticket? (too tired to open browser, even w3m :P)
Increased TSD (aka TLS/thread-local-storage/thread-specific-data)
usage in jemalloc will be a problem with tiny stack size used by
timer thread. I made 58874 to 2.5 as a workaround for high TSD
use in libkqueue.
Also, I may have an idea to remove timer-thread completely, even
under contention...