Usually the kernel handles memory utilization pretty well it caches memory for dentry cache, page cache and inodes which improves IO speed and performance generally. But in some cases user applications needs lots of memory and we need to clear what’s called dirty memory which could be inodes already written to the disk, so now the kernel given us the option to manage this manually.

First of all Run sync command to flush all file system buffers

Then run one of this commands :

echo 1 > /proc/sys/vm/drop_caches

This will free only page caches

echo 2 > /proc/sys/vm/drop_caches

This will free inodes and dentry caches

echo 3 > /proc/sys/vm/drop_caches

This will free ALL