释放网页缓存(To free pagecache):

sync; echo 1 > /proc/sys/vm/drop_caches

释放目录项和索引(To free dentries and inodes):

sync; echo 2 > /proc/sys/vm/drop_caches

释放网页缓存，目录项和索引（To free pagecache, dentries and inodes）:

sync; echo 3 > /proc/sys/vm/drop_caches

实测结果：