ConcurrentHashMap 中的分割 [英] Segmentation in ConcurrentHashMap

问题描述

我是 Java 世界的新手，我在探索 ConcurrentHashMap API 时发现了这一点:

I am a newbie to the world of Java and I was exploring the ConcurrentHashMap API in which I discovered this:

static final int DEFAULT_INITIAL_CAPACITY = 16;
  static final float DEFAULT_LOAD_FACTOR = 0.75F;
  static final int DEFAULT_CONCURRENCY_LEVEL = 16;
  static final int MAXIMUM_CAPACITY = 1073741824;
  static final int MAX_SEGMENTS = 65536;
  static final int RETRIES_BEFORE_LOCK = 2;
  final Segment<K, V>[] segments;
final Segment<K, V> segmentFor(int paramInt)
  {
    return this.segments[(paramInt >>> this.segmentShift & this.segmentMask)];
  }

ConcurrentHashMap 中分割的基本原理是什么，为什么要使用它?请就细分概念提供更多建议.

What are the fundamentals of segmentation in ConcurrentHashMap and why it is used? Please advise more on the segmentation concept.

推荐答案

并发散列映射将其内容划分为段，以减少写锁争用.

The concurrent hash map divides its contents into segments, to reduce writer lock contention.

concurrencyLevel 参数定义段数.默认为 16.

The concurrencyLevel parameter defines the number of segments. It's 16 by default.

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