How to measure elapse time in Cortex-M4 - cortex-m

Question

I am using Cortex-M4 on SOC and I want to measure the time a certain function take.
Googling it I saw two methods
Method 1 - using DWT_CYCCNT
REGISTER(DEMCR_ADDR) |= 1 << 24 ; //TRCENA_OFFSET
REGISTER(DWT_CTRL) |= 1; //on
startTime = REGISTER(DWT_CYCCNT);
//doing work
elapsedTime = REGISTER(DWT_CYCCNT) -startTime
REGISTER(DWT_CTRL) &= ~1; //of
Method 2: - using SysTick
//init
SysTick->LOAD = SysTick_LOAD_RELOAD_Msk; /* set reload register = MAX COUNT*/
SysTick->VAL = 0UL; /* Load the SysTick Counter Value */
SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk |
SysTick_CTRL_ENABLE_Msk; /* Enable SysTick IRQ and SysTick Timer */
startTime = SysTick->VAL;
//do some work
elapsedTime = SysTick->VAL - start time;
SysTick->LOAD = SysTick_LOAD_RELOAD_Msk; /* set reload register = MAX COUNT*/
SysTick->VAL = 0UL; /* Load the SysTick Counter Value */
SysTick->CTRL = 0UL;
I wonder what are the advantages / disadvantages of these two methods

Answer 1

I have used both these methods in different projects.
In either case, you might use one of these because the other was already used for something else. If your RTOS wants the systick, use the debug counter. If your debugger wants the debug counter, use the systick.
The main disadvantage of the systick is that it only has 24 bits, whereas the debug counter has 32.
The main disadvantage is the debug counter is it is not available on every part (the systick is optional too, but hardly any silicon vendors take it out).
Enabling the whole debug block just for a counter also wastes a little bit of power, which you might care about if you are running from batteries.