RAM Management #

Freeing Stale Caches (drop_caches) #

On a Linux system, a fraction of the system memory can be reclaimed by dropping kernel caches.[1] We can use the following commands to achieve this.

To free pagecache:

sync && echo 1 > /proc/sys/vm/drop_caches

To free reclaimable slab objects (includes dentries and inodes):

sync && echo 2 > /proc/sys/vm/drop_caches

To free slab objects and pagecache:

sync && echo 3 > /proc/sys/vm/drop_caches

So, the last one combines the effect of commands 1 and 2.

These commands must be executed under the root shell. With sudo we can either need to enter the root shell first or execute the commands with sh [2]

sudo sh -c 'sync && echo 1 >/proc/sys/vm/drop_caches'

Refs #

• [1] https://www.kernel.org/doc/html/latest/admin-guide/sysctl/vm.html#drop-caches
• [2] https://unix.stackexchange.com/a/87909