Linux memory management
(flush cache, dump cache, drop cache)
This should only be used for performance testing where you want to be sure caching is not distorting run times between runs. Note that this does not give your applications more memory, despite what free might say. This is a common beginner's mistake.
This action is guaranteed to be harmless and non-destructive. This will only free non-dirty pages, so if you want to be sure you free as much as possible you should run sync before dropping caches.
To free pagecache: echo 1 > /proc/sys/vm/drop_caches To free dentries and inodes: echo 2 > /proc/sys/vm/drop_caches To free everything -- pagecache, dentries and inodes: echo 3 > /proc/sys/vm/drop_caches