TIP: Flush Memory Caches

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TIP: Flush Memory Caches

Postby Randy » Tue Jul 28, 2009 1:48 pm

If you're looking for a quick way to flush the memory cache under Linux without rebooting, here's the ticket! :)

Found at http://www.linuxinsight.com/proc_sys_vm ... aches.html
Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.

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

As this is a non-destructive operation, and dirty objects are not freeable, the user should run "sync" first in order to make sure all cached objects are freed.

This tunable was added in 2.6.16.
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