memory_sharing_test.kt

import java.util.concurrent.TimeUnit.MILLISECONDS
import java.util.concurrent.TimeUnit.NANOSECONDS

interface HasData {
    var data: Long
}

class DataImplWithoutPadding : HasData {

    @Volatile
    override var data = 0L

}

class DataImplWithPadding : HasData {

    @Volatile
    override var data = 0L

    val padding = ByteArray(48)
}

fun main(args: Array<String>) {
    arrayOf(DataImplWithoutPadding::class.java, DataImplWithPadding::class.java)
            .forEach { type ->
                val threadCount = 4
                val longs = Array(threadCount) { type.newInstance() }
                val threads = Array(threadCount) { index ->
                    Thread {
                        for (i in 1..100_000_000L) {
                            longs[index].data = i
                        }
                    }
                }

                val start = System.nanoTime()
                threads.forEach { it.start() }
                threads.forEach { it.join() }
                val end = System.nanoTime() - start

                println("${type.simpleName} took ${MILLISECONDS.convert(end, NANOSECONDS)} ms")
            }

}

/*
 * DataImplWithoutPadding took 8107 ms
 * DataImplWithPadding took 818 ms
 */