How to release cache in linux

How to release cache in linux [root @ master ~] # Free-m total used free shared buffers cachedMem: 2009 1999 9 0 1308 437-/+ buffers/cache: 253 1756 5951 Swap: 5951 0 [root @ master ~] # Cat/proc/sys/vm/drop_caches 0 [root @ master ~] # Echo 3>/proc/sys/vm/drop_caches [root @ master ~] # Cat/proc/sys/vm/drop_caches 3 [root @ master ~] # Sync [root @ master ~] # Free-m total used free shared buffers cachedMem: 2009 463 1545 0 176 49-/+ buffers/cache: 236 1772 Swap: 5951 0 5951 the usage of/proc/sys/vm/drop_caches is described below/proc/sys/vm/drop_caches (since Linux 2.6.16) writing to this file causes the kernel to drop clean caches, dentries and inodes from memory, causing that memory to becomefree. to free pagecache, use echo 1>/proc/sys/vm/drop_caches; tofree 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. because this is a non-destructive operation and dirty objectsare not freeable, the user shocould run sync (8) first.