how to measure rms value of a voltage signal taken as input from the ADC of microcontroller?

I am using an STM32F407 microcontroller with Simulink. I have the ADC through which i take my AC signal but i need to measure the RMS value of this signal. I have used the DRMS block but it slowed down the response time of LEDs which i want to blink based on the measured values. This was probably bcz this block uses the sample time which in my case is 0.0001 sec since the frequency of my AC is 2kHz. Is there any other way? Plz help