Analysis of the technical principles of the low -delayed primitive concurrency queue in the java class library
Analysis of the technical principles of the low -delayed primitive concurrency queue in the java class library
Low -delayed original concurrent queue is a data structure in the Java class library to solve the thread security problem in high concurrency.It provides an efficient way to achieve data exchange between multi -threaded to meet the needs of high -time requirements.
Before understanding the technical principles of the low delayed original concurrent queue, let's first understand the common concurrent queue in the Java class library:
1. The blocking queue: The blocking queue is a thread security queue. It provides a thread blocking mechanism. When the queue is full, the thread that try to insert the element will be blocked until the queue has space for free; when the queue is empty, try to tryThe thread that obtains elements will be blocked until the queue has available elements.Common blocking queues are ArrayBlockingQueue and LinkedBlockingQueue.
2. No lock queue: The lock -free queue achieves thread security by using CAS (Compare and Swap) operation.CAS is a lightweight synchronization mechanism that uses atomic operation to ensure thread safety.Common lock -free queues are ConcurrentLINKEDQUEUE.
However, in some high concurrency scenes, the above queues often cannot meet the requirements of applications for low latency.To this end, the Java class library provides a special queue, namely low delayed original concurrent queue.
The technical principles of low latency original concurrent queue mainly involve the following aspects:
1. No lock design: Low latency The original concurrent queue uses a lock -free design, that is, the traditional mutual lock mechanism is used to ensure the security of the thread.In contrast, the lock -free design reduces the competition between threads and context switching, and improves concurrent performance.
2. Ring Buffer: Low latency Primitive concurrent queue is implemented based on ring buffer.The ring buffer is an efficient cycle array structure that provides fast insertion and deletion operations.It stores queue elements in continuous memory blocks, eliminates frequent memory allocation and recycling, and reduces the pressure of garbage collection.
3. Memory Barrier: Low delayed original concurrent queue uses memory barriers to ensure the visibility and order of data.Memory barrier is a synchronous language provided by hardware and compiler, which is used to control the execution order of memory operation and data synchronization between different threads.
Below is a simple low -delayed primitive java code example:
import java.util.concurrent.atomic.AtomicInteger;
public class LowLatencyQueue<T> {
private T[] ringBuffer;
private final int capacity;
private AtomicInteger head = new AtomicInteger();
private AtomicInteger tail = new AtomicInteger();
public LowLatencyQueue(int capacity) {
this.capacity = capacity;
ringBuffer = (T[]) new Object[capacity];
}
public boolean enqueue(T element) {
int currentTail = tail.get();
int nextTail = (currentTail + 1) % capacity;
if (nextTail == head.get()) {
return false; // Queue is full
}
ringBuffer[currentTail] = element;
tail.lazySet(nextTail);
return true;
}
public T dequeue() {
int currentHead = head.get();
if (currentHead == tail.get()) {
return null; // Queue is empty
}
T element = ringBuffer[currentHead];
ringBuffer[currentHead] = null;
head.lazySet((currentHead + 1) % capacity);
return element;
}
// Other methods
}
In the above examples, we use the Head and TAIL to implement thread security by using the AtomicInteger class, and store the element in the continuous position of the ring buffer array.
The Enqueue method checks whether the queue is full before inserting the element.If the queue is full, return False.Otherwise, insert the element to the current TAIL position and use LazySet to update the TAIL index.
The Dequeue method checks whether the queue is empty before obtaining the element.If the queue is empty, return NULL.Otherwise, obtain elements from the current head position and use LazySet to update the HEAD index.
In this way, the low -delayed primitive concurrent queue has achieved efficient multi -threaded data exchange, which meets the needs of high -time real -time requirements in high concurrency.
