java-OpenJDK的LinkedBlockingQueue实现：节点类和GC

这个问题已经在这里有了答案：            >            Strange code in java.util.concurrent.LinkedBlockingQueue                                    4个
OpenJDK的LinkedBlockingQueue实现(在java.util.concurrent中)对Node类的结构感到有些困惑.

我已经复制了以下节点类的描述：

static class Node<E> {
    E item;

    /**
     * One of:
     * - the real successor Node
     * - this Node, meaning the successor is head.next
     * - null, meaning there is no successor (this is the last node)
     */
    Node<E> next;

    Node(E x) { item = x; }
}

具体来说,我对下一个第二选择感到困惑(“此节点,意味着后继者是head.next”).

这似乎与出队方法直接相关,如下所示：

private E dequeue() {
    // assert takeLock.isHeldByCurrentThread();
    // assert head.item == null;
    Node<E> h = head;
    Node<E> first = h.next;
    h.next = h; // help GC
    head = first;
    E x = first.item;
    first.item = null;
    return x;
}

因此,我们已删除了当前标题,并将其下一个设置为“ help GC”.

这如何帮助GC？对GC有多大帮助？

解决方法:

我问了代码作者Doug Lea教授,他说这可以减少
GC留下漂浮垃圾的机会.

一些有关浮动垃圾的有用资源：

http://www.memorymanagement.org/glossary/f.html#floating.garbage

http://java.sun.com/docs/hotspot/gc1.4.2/#4.4.4.%20Floating%20Garbage|outline

http://blog.johantibell.com/2010/04/generational-garbage-collection-and.html

标签：java,concurrency,garbage-collection,queue,java-util-concurrent
来源： https://codeday.me/bug/20191011/1891115.html