Linux - Memory/Swap

Commandes

Display available memory:

free -m

Display consumed swap:

swapon -s

Disable swap:

# For a specific swap lv
swapoff {lv-swap}

# For all
swapoff -a

Enable swap:

# For a specific swap lv
swapon {lv-swap}

# For all
swapon -a

Flush the swap:

swapoff -a && swapon -a

Display vm.swappiness value:

sysctl -n vm.swappiness

Set new value of vm.swappiness:

sysctl -w vm.swappiness={value}
# Ex: sysctl -w vm.swappiness=5

Create swap:

mkswap {lv-swap}
# Ex:
#   lvcreate -L 2G -n lv_swap2 rootvg
#   mkswap /dev/rootvg/lv_swap2 

Memory stats:

vmstat 1

Display process that use swap:

for f in /proc/*/status ; do swp=$(awk '/VmSwap|Name/ {printf "%s %s\n", $2, $3}' $f); echo $swp; done | grep -E 'B$' | sort -k 2 -nr

Procedures

Drop Memory Cache

# Display memory
free -m

# Flush FS buffers
sync; sync; sync

# Drop cache
echo 1 > /proc/sys/vm/drop_caches

Add Swap

# Create swap 
lvcreate -L 2G -n lv_swap2 rootvg 
mkswap /dev/rootvg/lv_swap2 

# Add new entry in /etc/fstab 
/dev/mapper/rootvg-lv_swap2 swap swap defaults 0 0 

# Activate swap
swapon -v /dev/mapper/rootvg-lv_swap2

# Verify the swap
free -m