Hi, I think that 4753ef37e0ed undid the work caf626b2c did to support sub-millisecond delays for vacuum and autovacuum.
After 4753ef37e0ed, vacuum_delay_point()'s local variable msec is a double which, after being passed to WaitLatch() as timeout, which is a long, ends up being 0, so we don't end up waiting AFAICT. When I set [autovacuum_]vacuum_delay_point to 0.5, SHOW will report that it is 500us, but WaitLatch() is still getting 0 as timeout. - Melanie
