Low delayed original concurrent queue technology in the application principle of the Java library
Low latency original concurrent queue technology is a concurrent programming technology widely used in the Java class library.It achieves excellent performance and low latency in high concurrency scenes by using computer's multi -core processing capabilities and memory barriers.
The core idea of low latency primitive concurrent queue technology is to improve performance by reducing competition between multi -threaded.In the traditional queue implementation, when multiple threads compete at the same time, the head or tail of the queue can cause a large number of lock conflict and context switching, resulting in decline and delay in performance.The low -delayed primitive concurrent queue technology avoids the lock competition between multi -threaded locks by storing data in shared memory, thereby increasing the speed and response time.
In the Java class library, the implementation of low -delayed primitive concurrent queue technology mainly depends on two key classes: UNSAFE and ConcurrentLinkedQueue.
The UNSAFE class is a very powerful tool class provided in Java for direct operation of memory.It provides a series of local methods that can be used to directly read and write memory, allocate memory and other operations.By using the UNSAFE class, we can bypass Java's memory management mechanism to directly read and write operations on sharing memory, thereby achieving low delayed concurrency queues.
ConcurrentlinkedQueue is a thread security queue implementation class provided in the Java class library.It uses CAS (Compaare and Swap) operation to implement thread security data insertion and delete operations.CAS operation is a lock -free atomic operation that can achieve multi -threaded concurrent operation, avoiding locking competition and context switching, thereby improving the performance and response time of the queue.
Below is a simple example code, which demonstrates the application of low delayed original concurrent queue technology:
import sun.misc.Unsafe;
import java.lang.reflect.Field;
import java.util.concurrent.atomic.AtomicReference;
public class LowLatencyConcurrentQueue<T> {
private static final Unsafe unsafe;
private static final long headOffset;
private static final long tailOffset;
static {
try {
Field field = Unsafe.class.getDeclaredField("theUnsafe");
field.setAccessible(true);
unsafe = (Unsafe) field.get(null);
headOffset = unsafe.objectFieldOffset(LowLatencyConcurrentQueue.class.getDeclaredField("head"));
tailOffset = unsafe.objectFieldOffset(LowLatencyConcurrentQueue.class.getDeclaredField("tail"));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
private static class Node<T> {
private final T value;
private volatile Node<T> next;
private Node(T value) {
this.value = value;
}
}
private volatile Node<T> head;
private volatile Node<T> tail;
public void enqueue(T value) {
Node<T> newNode = new Node<>(value);
while (true) {
Node<T> currentTail = tail;
Node<T> tailNext = currentTail.next;
if (currentTail == tail) {
if (tailNext == null) {
if (unsafe.compareAndSwapObject(this, tailOffset, currentTail, newNode)) {
unsafe.compareAndSwapObject(this, headOffset, null, newNode);
return;
}
} else {
unsafe.compareAndSwapObject(this, tailOffset, currentTail, tailNext);
}
}
}
}
public T dequeue() {
while (true) {
Node<T> currentHead = head;
Node<T> currentTail = tail;
Node<T> headNext = currentHead.next;
if (currentHead == head) {
if (currentHead == currentTail) {
if (headNext == null) {
return null;
}
unsafe.compareAndSwapObject(this, tailOffset, currentTail, headNext);
} else {
if (unsafe.compareAndSwapObject(this, headOffset, currentHead, headNext)) {
return headNext.value;
}
}
}
}
}
}
In the above code, we use the UNSAFE class CompareAreandswapobject method to implement the lock -free atomic operation.It can compare the current value with the expected value under a thread security method, and update the value when the result is true.In this way, a high -performance low -delay primitive concurrent queue is achieved.
To sum up, the low -delayed original concurrent queue technology uses the multi -core processing capacity and memory barrier mechanism of the computer to achieve excellent performance and low latency in high concurrent scenes.In the Java class library, by using the UNSAFE class and the ConcurrentLinkedQueue classes, we can easily implement the low -delayed concurrency queue and improve the performance and response time of the program.
