On Fri, Mar 10, 2023 at 10:26 AM Melanie Plageman <melanieplage...@gmail.com> wrote: > 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.
Given that some of the clunkier underlying kernel primitives have milliseconds in their interface, I don't think it would be possible to make a usec-based variant of WaitEventSetWait() that works everywhere. Could it possibly make sense to do something that accumulates the error, so if you're using 0.5 then every second vacuum_delay_point() waits for 1ms?
