whatever " thumb-twiddling" means (no native english speaker) delay is not issue, i put
PORTB |= _BV(PORTB4);
PORTB &= ~_BV(PORTB4);
in vector i see LED deeming and when i looked at my oscilloscope it switches really fast in loop.
PS. At least it seems like that but i guess my old made in USSR oscilloscope dosn't catchup.