To free pagecache: echo 1 > /proc/sys/vm/drop_caches;
to free dentries and inodes: echo 2 > /proc/sys/vm/drop_caches;
to free pagecache, dentries and inodes: echo 3 >/proc/sys/vm/drop_caches.
原文地址：http://www.cnblogs.com/chegnshi-coding/p/3804145.html
