Race-to-sleep (sometimes Race-to-Dark or Race-to-Idle/Halt/Zero) is a common power-saving technique used in most modern high-performance integrated circuits whereby the chip enters its highest operating frequency in order to complete the workload as fast as possible in order to go back to sleep or its lowest operating frequency.
Various highly complex methods for reducing the power consumption of a chip have been developed over the years such as Intel's SpeedStep (EIST) and AMD's Cool'n'Quiet. Those methods make use of various Dynamic Voltage and Frequency Scaling (DVFS) techniques in order to reduce the operating voltage and frequency when the processing power is not needed thereby greatly reducing the dynamic energy consumption.
One problem that remains is the static power leakage that is always present in the system. Race-to-sleep attempts to address this issue by proposing that the highest frequency is used to complete the task as fast as possible, then once finish, drop back to very low power modes - often turning off or power gating the cores. Race-to-sleep attempts to reduce the delay in completing a task as much as possible in order to reduce the static power consumption, thereby consuming significantly less power overall.