Use zswap instead of swap in zram (#2420)

* Use zswap instead of swap in zram

This requires a swap file which will get generated automatically on
startup.

* Fix file size and free disk space comparison

* Set zswap factor to 33%

* Set vm.swappiness to 1

Decrease swapping to a minimum. This is also recommended for database
work loads by the MariaDB documentation. In practice it causes the least
amount of writes to disk when under memory pressure, while still making
swap available when needed.

buildroot-external/rootfs-overlay/usr/lib/systemd/system/dev-zram0.swap

@@ -1,10 +0,0 @@
-[Unit]
-Description=HassOS ZRAM swap
-Requires=zram-swap.service
-After=zram-swap.service
-
-[Swap]
-What=/dev/zram0
-
-[Install]
-WantedBy=swap.target

buildroot-external/rootfs-overlay/usr/lib/systemd/system/haos-swapfile.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=HAOS swap
+DefaultDependencies=no
+Requires=mnt-data.mount
+After=mnt-data.mount systemd-growfs@mnt-data.service
+Before=mnt-data-swapfile.swap
+
+[Service]
+Type=oneshot
+ExecStart=/usr/libexec/haos-swapfile
+
+[Install]
+WantedBy=multi-user.target

buildroot-external/rootfs-overlay/usr/lib/systemd/system/mnt-data-swapfile.swap

@@ -0,0 +1,8 @@
+[Unit]
+Description=HAOS swap file
+
+[Swap]
+What=/mnt/data/swapfile
+
+[Install]
+WantedBy=swap.target

buildroot-external/rootfs-overlay/usr/lib/systemd/system/zram-swap.service

@@ -1,15 +0,0 @@
-[Unit]
-Description=HassOS ZRAM swap
-DefaultDependencies=no
-Before=dev-zram0.swap
-RefuseManualStart=true
-RefuseManualStop=true
-
-[Service]
-Type=oneshot
-ExecStart=/usr/libexec/hassos-zram -t swap
-RemainAfterExit=true
-StandardOutput=null
-
-[Install]
-WantedBy=hassos-zram.target