# Everything that lands on the kernel cmdline goes in one marked block, leaving
# the existing KERNEL_CMDLINE[default]+= line untouched.
#
# systemd.zram=0      - stop zram-generator creating the zram device
# zswap.*             - module params, must be set before first swap-out
# ttm.pages_limit     - hard cap on GTT allocation, lifted from the ~50% of RAM
#                       default. 3959290 pages of 4K = ~15.1 GiB
# ttm.page_pool_size  - must match pages_limit or allocations can fail
- name: Add BC-250 kernel parameters
  become: true
  ansible.builtin.blockinfile:
    path: /etc/default/limine
    marker: '# {mark} ANSIBLE bc250 memory'
    block: |
      KERNEL_CMDLINE[default]+=" systemd.zram=0 zswap.enabled=1 zswap.shrinker_enabled=1 zswap.compressor=lz4 zswap.max_pool_percent=20 ttm.pages_limit=3959290 ttm.page_pool_size=3959290"
  notify: Rebuild initramfs and limine entries

# lz4 must be in the initramfs for zswap to use it from early boot.
- name: Add lz4 to the initramfs modules
  become: true
  ansible.builtin.lineinfile:
    path: /etc/mkinitcpio.conf
    regexp: '^MODULES='
    line: 'MODULES=(lz4)'
  notify: Rebuild initramfs and limine entries

# CachyOS ships a udev rule that disables zswap when zram comes up.
# An empty file with the same name overrides it.
- name: Neutralise the CachyOS zram udev rule
  become: true
  ansible.builtin.copy:
    content: ''
    dest: /etc/udev/rules.d/30-zram.rules
    mode: '0644'

- name: Lower swappiness
  become: true
  ansible.builtin.copy:
    content: vm.swappiness=10
    dest: /etc/sysctl.d/99-bc250.conf
    mode: '0644'
  register: sysctl_conf

- name: Apply swappiness now
  become: true
  ansible.builtin.command:
    argv:
      - sysctl
      - --system
  when: sysctl_conf.changed
  changed_when: true

- name: Create the swap subvolume
  become: true
  ansible.builtin.command:
    argv:
      - btrfs
      - subvolume
      - create
      - /swap
  args:
    creates: /swap

- name: Create the swapfile
  become: true
  ansible.builtin.command:
    argv:
      - btrfs
      - filesystem
      - mkswapfile
      - --size
      - 8g
      - --uuid
      - clear
      - /swap/swapfile
  args:
    creates: /swap/swapfile

- name: Add the swapfile to fstab
  become: true
  ansible.builtin.lineinfile:
    path: /etc/fstab
    regexp: '^/swap/swapfile'
    line: '/swap/swapfile none swap defaults 0 0'

- name: Apply pending initramfs changes
  ansible.builtin.meta: flush_handlers

- name: Reboot to apply the new kernel parameters
  become: true
  ansible.builtin.reboot:
    reboot_timeout: 600