centos clear the cache

Release Web cache (the To Free pagecache): 
echo. 1> / proc / SYS / VM / drop_caches 


release directory entries and the index (the To Free DEntries and of inodes): 
echo 2> / proc / SYS / VM / drop_caches 

release web caching, directory entry and index (the To Free pagecache, and DEntries of inodes): 
echo. 3> / proc / SYS / VM / drop_caches