1、将内存的数据写回硬盘
sync
2、清除缓存
echo 3 > /proc/sys/vm/drop_caches
完成！
drop_caches 的解释：
To free pagecache, use echo 1 > /proc/sys/vm/drop_caches;
to free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
to free pagecache, dentries and inodes, use echo 3 >/proc/sys/vm/drop_caches.