Sometimes it's necessary to have a little bit more more memory for heavy duty or occasional tasks (emerge chrome.. openoffice...) if you've some free disk it's possible to create a temp swap file from it.
# Create a 5Gb file
fallocate -l 5G /mnt/5GB.swap
# Chmod
chmod 600 /mnt/5GB.swap
# Making a swap file from it
mkswap /mnt/5GB.swap
# Mounting/adding it to system memory
swapon /mnt/5GB.swap
# Umount it when done
swapoff /mnt/5GB.swap
~ # free
total used free shared buff/cache available
Mem: 8053300 4423404 1878272 61200 1751624 3467344
Swap: 4194300 0 4194300
~ # sync; echo 3 > /proc/sys/vm/drop_caches
~ # free
total used free shared buff/cache available
Mem: 8053300 4523964 2968264 144388 561072 3286236
Swap: 4194300 0 4194300
As you can see buffer mem is cleared with drop_cache
- Clear pagecache only.
# sync; echo 1 > /proc/sys/vm/drop_caches
- Clear dentries and inodes
# sync; echo 2 > /proc/sys/vm/drop_caches
- Clear pagecache, dentries, and inodes
# sync; echo 3 > /proc/sys/vm/drop_caches