An apparatus can include a choke with a flow restrictor having at least two positions, a flow coefficient Cv of the choke with the flow restrictor in one position being less than with the flow restrictor in the other position, and an operational device that displaces the flow restrictor at a variable actuation rate, the actuation rate with the flow restrictor in one position being less than with the flow restrictor in the other position. A method can include displacing a flow restrictor, thereby decreasing a flow coefficient Cv of a choke, and decreasing a rate of change of the flow coefficient Cv in response to decreasing the flow coefficient Cv. A drilling system can include a choke with a flow restrictor, and a continuously variable transmission which causes an actuation rate to vary based on a position of the flow restrictor.