1. swapon -s # 查看内存信息
2. mkswap /dev/sdb8 # 将sdb8分区添加作为另一个内存
3. swapon -a /dev/sdb8 # 在2的基础上，激活sdb8作为内存，此时查看内存可以看到这个信息
4. swapoff /dev/sdb8 # 关闭sdb8内存
5. buffer: a buffer is something that has yet to be "written" to disk # 还没有写到硬盘
6. cache: a cache is something that has been "read" from the disk and stored for later use # 读到内存保留一段时间，供后面使用
7. echo 3 > /proc/sys/vm/drop_caches # 清理cache
8. free -m