measureNanoTime

Executes the given block and returns elapsed time in nanoseconds. For a more human-readable and typed output, measureTime can be used instead.

inline fun measureNanoTime(block: () -> Unit): Long(source)

import kotlin.system.measureNanoTime

fun main() {
    val elapsedTime = measureNanoTime {
        // Code you want to time
        val sum = (1..1_000_000).sum()
        println("Sum = $sum")
    }

    println("Elapsed time: $elapsedTime ns")
}

Source