Redis淘汰策略及LRU算法

一.Redis查看内存大小

1.查看配置文件,里面找 maxmemory ,如果注释或者配置0,64位默认不限制,32位为3g

2.命令方式: info memory

 

二.Redis满了继续存数据会出现什么异常?

报OOM

三.Redis的删除策略

1.定时删除:对cpu不友好,用处理器性能换取存储时间,(拿时间换空间)

2.惰性删除: 对内存不友好,用存储空间换取处理器性能(拿空间换时间)

 3.定期删除

八种淘汰策略:

一般会选择allkeys-lru 淘汰策略.

public class LRUCacheDemo<K,V> extends LinkedHashMap<K,V> {
    private int capacity;//缓存坑位

    public LRUCacheDemo(int capacity) {
        super(capacity, 0.75F, true);
        this.capacity = capacity;
    }

    protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
        return super.size() > capacity;
    }

    public static void main(String[] args) {
        LRUCacheDemo lruCacheDemo = new LRUCacheDemo(3);
        lruCacheDemo.put(1,"a");
        lruCacheDemo.put(2,"b");
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());

        lruCacheDemo.put(4,"d");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(5,"x");
        System.out.println(lruCacheDemo.keySet());

    }
}

public class LRUCacheDemo<K,V> extends LinkedHashMap<K,V> {
    private int capacity;//缓存坑位

    public LRUCacheDemo(int capacity) {
        super(capacity, 0.75F, false);
        this.capacity = capacity;
    }

    protected boolean removeEldestEntry(Map.Entry<K,V> eldest) {
        return super.size() > capacity;
    }

    public static void main(String[] args) {
        LRUCacheDemo lruCacheDemo = new LRUCacheDemo(3);
        lruCacheDemo.put(1,"a");
        lruCacheDemo.put(2,"b");
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());

        lruCacheDemo.put(4,"d");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(3,"c");
        System.out.println(lruCacheDemo.keySet());
        lruCacheDemo.put(5,"x");
        System.out.println(lruCacheDemo.keySet());

    }
}