what are all the .cold symbols in system.map?

Ive been seeing these in my backtraces they seem to come in both .cold and not cold flavors are they related to unlikely() code blocks ? ffffffff81001820 t calibrate_delay_direct ffffffff81001a90 t calibrate_delay_converge ffffffff81001bb0 W calibration_delay_done ffffffff81001bc0 T calibrate_delay ffffffff81001cc3 t calibrate_delay_direct.cold ffffffff81001df7 t calibrate_delay.cold