cpu
IO

连接数
    配置:SHOW VARIABLES LIKE '%connec%';
        max_connections
        max_user_connections
    状态:SHOW STATUS LIKE '%connec%';
        Connections
        Max_used_connections

线程池
    配置:SHOW VARIABLES LIKE 'thread%';
        thread_cache_size
        thread_concurrency
    状态:SHOW STATUS LIKE 'thread%';
        Threads_cached
        Threads_connected
        Threads_created
        Threads_running