epoll_pwait2 (Linux 5.11) takes the timeout in nanoseconds; epoll_wait rounds it up to a
whole millisecond, which delays a timer 100 us away by up to 1 ms. The raw system call: libc
before 2.35 has no wrapper. The number is the same on x86-64 and arm64.
SYS_epoll_pwait2 :: 441