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Kernels 2.6.16 and newer provide a mechanism to have the kernel drop the page cache and/or inode and dentry caches on command, which can help free up a lot of memory. Now you can throw away that script that allocated a ton of memory just to get rid of the cache...

To use /proc/sys/vm/drop_caches, just echo a number to it.

To free pagecache:

<verbatim>
# echo 1 > /proc/sys/vm/drop_caches
</verbatim>

To free dentries and inodes:

<verbatim>
# echo 2 > /proc/sys/vm/drop_caches
</verbatim>

To free pagecache, dentries and inodes:

<verbatim>
echo 3 > /proc/sys/vm/drop_caches
</verbatim>

As this is a non-destructive operation and dirty objects are not freeable, the user should run "sync" first!

bin/dropcache:
<verbatim>
#!/bin/sh

exec sudo /bin/sh -c 'sync; sync; sync; sync; echo 3 > /proc/sys/vm/drop_caches'
</verbatim>