缓存命中率

转载：https://www.baidu.com/s?wd=%E7%BC%93%E5%AD%98%E5%91%BD%E4%B8%AD%E7%8E%87&rsv_spt=1&rsv_iqid=0xbbc679fa00a4af52&issp=1&f=8&rsv_bp=1&rsv_idx=2&ie=utf-8&tn=baiduhome_pg&rsv_enter=1&rsv_dl=tb&rsv_n=2&rsv_sug3=1&rsv_sug1=1&rsv_sug7=100&rsv_sug2=0&rsv_btype=i&inputT=673&rsv_sug4=673