systemd-swap

Script for manage swap on:

• zswap - Enable/Configure
• zram - Autoconfigurating for swap
• files - (sparse files for saving space, support btrfs)
• block devices - auto find and do swapon

ℹ️ It is configurable in /etc/systemd/swap.conf.

Additional terms:

• SwapFC (File Chunked) - provide a dynamic swap file allocation/deallocation

Files placed

/etc/systemd/swap.conf
/usr/lib/systemd/system/systemd-swap.service
/usr/bin/systemd-swap

Please not forget to enable by

sudo systemctl enable systemd-swap

Install

• Arch: in the community.

• Debian: use package.sh in git repo

  git clone https://github.com/Nefelim4ag/systemd-swap.git
  ./systemd-swap/package.sh debian
  sudo dpkg -i ././systemd-swap/systemd-swap_*_all.deb

• Fedora: use package.sh

  git clone https://github.com/Nefelim4ag/systemd-swap.git
  ./systemd-swap/package.sh fedora f28
  sudo dnf install ./systemd-swap/systemd-swap-*noarch.rpm

• Manual

  git clone https://github.com/Nefelim4ag/systemd-swap.git
  sudo make install

About configuration

Q: WTF?! Why you merge swapFC and swapFU?
A: That simplify testing of swapFC code and make code more generic

Q: How can i migrate config swapFU from 3.X to 4.X?
A: Most of switches are same, to get configuration like swapFU from swapFC, set swapfc_max_count to 1 and swapfc_chunk_size to size of swapFU.

Q: Do we need to activate both zram and zswap?
A: Nope, it's useless, as zram is a compressed RAM DISK, but zswap is a compressed "writeback" CACHE on swap file/disk.

Q: Do i need use swapfc_force_use_loop on swapFC?
A: Nope, as you wish really, native swapfile must work faster and it's more safe in OOM condition in comparison to loop backed scenario.

Q: When would we want a certain configuration?
A: In most cases (Notebook, Desktop, Server) it's enough to enable zswap + swapfc (On server tuning of swapfc can be needed). In case where SSD used, and you care about flash wear, use only ZRam.

Q: Where is the swap file located?
A: Read carefully swap.conf

Q: Can we use this to enable hibernation?
A: Nope as hibernation wants a persistent fs blocks and wants access to swap data directly from disk, this will not work on: zram, swapfu, swapfc (without some magic of course).

Note

• ℹ️ Zram dependence: util-linux >= 2.26

• ℹ️ If you use zram not for only swap, use kernel 4.2+ or please add rule for modprobe like:

  options zram max_devices=32

Switch On Systemd Swap

• For check your configuration:

  cat /proc/sys/vm/swappiness
  cat /proc/sys/vm/vfs_cache_pressure

• Recomended configuration for Desktop:

  echo vm.swappiness=5 | sudo tee -a /etc/sysctl.d/99-sysctl.conf
  echo vm.vfs_cache_pressure=50 | sudo tee -a /etc/sysctl.d/99-sysctl.conf
  sudo sysctl -p /etc/sysctl.d/99-sysctl.conf

• If you have install Systemd Swap check configuration:

  nano /etc/systemd/swap.conf

  zram_enabled=0
  zswap_enabled=1
  swapfc_enabled=1

• Stop your swap:

  sudo swapoff -a

• Need to remove swap from fstab:

  nano /etc/fstab

• Remove your swap

  # For Ubuntu
  sudo rm -f /swapfile
  
  # For Centos 7
  lvremove -Ay /dev/centos/swap
  lvextend -l +100%FREE centos/root

• Remove swap from Grub:

  # For Ubuntu remove resume* in grub
  nano /etc/default/grub
  
  # For Centos 7 remove rd.lvm.lv=centos/swap*
  nano /etc/default/grub
  
  # For Manjaro remove resume* in grub & mkinitcpio
  nano /etc/default/grub
  nano /etc/mkinitcpio.conf

  # For Ubuntu
  update-grub
  
  # For Centos 7
  update-grub
  
  # For Manjaro
  update-grub
  mkinitcpio -P