Gets the count from the microsecond timer (ust), a hardware timer. This microsecond timer counts the microseconds passed from the time the system is powered on until now. It allows the caller to measure the durations in high precision. To calculate the duration between different timer counts, use vm_time_ust_get_duration(), instead of simply subtract values, because the timer counts may wrap around.
The microseconds from the system power on until now.
start = vm_time_ust_get_count();