Redis 的内存淘汰策略问题

//设置Redis最大占用内存大小为100Mmaxmemory 100mb

//设置Redis最大占用内存大小为100M127.0.0.1:6379> config set maxmemory 100mb//获取设置的Redis能使用的最大内存大小127.0.0.1:6379> config get maxmemory

127.0.0.1:6379> config get maxmemory-policy

maxmemory-policy allkeys-lru

127.0.0.1:6379> config set maxmemory-policy allkeys-lru

public class LRUCache {    //容量    private int capacity;    //当前有多少节点的统计    private int count;    //缓存节点    private Map> nodeMap;    private Node head;    private Node tail;
    public LRUCache(int capacity) {        if (capacity < 1) {            throw new IllegalArgumentException(String.valueOf(capacity));        }        this.capacity = capacity;        this.nodeMap = new HashMap<>();        //初始化头节点和尾节点，利用哨兵模式减少判断头结点和尾节点为空的代码        Node headNode = new Node(null, null);        Node tailNode = new Node(null, null);        headNode.next = tailNode;        tailNode.pre = headNode;        this.head = headNode;        this.tail = tailNode;    }
    public void put(k key, v value) {        Node node = nodeMap.get(key);        if (node == null) {            if (count >= capacity) {                //先移除一个节点                removeNode();            }            node = new Node<>(key, value);            //添加节点            addNode(node);        } else {            //移动节点到头节点            moveNodeToHead(node);        }    }
    public Node get(k key) {        Node node = nodeMap.get(key);        if (node != null) {            moveNodeToHead(node);        }        return node;    }
    private void removeNode() {        Node node = tail.pre;        //从链表里面移除        removeFromList(node);        nodeMap.remove(node.key);        count--;    }
    private void removeFromList(Node node) {        Node pre = node.pre;        Node next = node.next;
        pre.next = next;        next.pre = pre;
        node.next = null;        node.pre = null;    }
    private void addNode(Node node) {        //添加节点到头部        addToHead(node);        nodeMap.put(node.key, node);        count++;    }
    private void addToHead(Node node) {        Node next = head.next;        next.pre = node;        node.next = next;        node.pre = head;        head.next = node;    }
    public void moveNodeToHead(Node node) {        //从链表里面移除        removeFromList(node);        //添加节点到头部        addToHead(node);    }
    class Node {        k key;        v value;        Node pre;        Node next;
        public Node(k key, v value) {            this.key = key;            this.value = value;        }    }}