Memory

Configure Swap

• Review: sudo swapon --show
• Resize:

1. disable: sudo swapoff /swap.img
2. resize: sudo fallocate -l 32G /swap.img
3. mark the file as swap: sudo mkswap /swap.img
4. enable swap file: sudo swapon /swap.img

• Deprioritize:

1. Check the current swappiness: cat /proc/sys/vm/swappiness
2. Temporarily lower the swap priority: sudo sysctl vm.swappiness=10
3. Permanently lower the swap priority:
   1. Add vm.swappiness = 10 to /etc/sysctl.conf
   2. Reload the configuration: sudo sysctl -p
   3. Confirm that the swap is active: swapon --show

• Disable:

1. Identify the swap file sudo swapon --show.
2. Disable swapping until the next reboot: sudo swapoff <SWAP_FILE>.
3. Comment out the swap configuration line in /etc/fstab to permanently disable swapping.

• Clear swap manually:

1. sudo swapoff -a
2. sudo swapon -a
3. Check the swap status, it should on bu empty. In case if it is off, re-enable: sudo swapon /swap.img

Memory mapped files limit

• Check the current limit: sysctl vm.max_map_count
• Increase:

1. Search for the vm.max_map_count parameter the sysctl configuration files:
   • sudo grep max_map_count /etc/sysctl.conf
   • sudo grep max_map_count /etc/sysctl.d/*
2. Update the existing or insert the new map count parameter to /etc/sysctl.conf: vm.max_map_count = 1000000
3. Reload the sysctl service: sudo sysctl -p
4. Confirm that the files limit was updated: sysctl vm.max_map_count

Stress Testing

• Use stress-ng

CLI

• Free memory: free -th or cat /proc/meminfo | grep MemFree
  • refresh every second: free -th -s 1
• Top 10 processes that use most memory: ps aux --sort=-%mem | head -10