ConcurrentHashMap 的分割
it1352
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问题说明
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.
正确答案
#1
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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