Add and configure 20% of memory as zram swap with a low agressive swappiness

buildroot-external/board/raspberrypi/kernel.config

@@ -1,3 +1,6 @@
 CONFIG_SND_SOC_WM8960=m
 # CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE is not set
 CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
+
+CONFIG_ZRAM=y
+CONFIG_ZSMALLOC=y

buildroot-external/configs/rpi4_64-gui_defconfig

@@ -465,6 +465,7 @@ BR2_PACKAGE_UTIL_LINUX_BINARIES=y
 BR2_PACKAGE_UTIL_LINUX_HWCLOCK=y
 BR2_PACKAGE_UTIL_LINUX_KILL=y
 BR2_PACKAGE_UTIL_LINUX_MORE=y
+BR2_PACKAGE_UTIL_LINUX_ZRAMCTL=y
 BR2_PACKAGE_NANO=y
 BR2_PACKAGE_VIM=y
 # BR2_PACKAGE_VIM_RUNTIME is not set

buildroot-external/rootfs-overlay/etc/sysctl.conf

@@ -0,0 +1 @@
+vm.swappiness = 20

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

@@ -0,0 +1,10 @@
+[Unit]
+Description=OVOS 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/ovos-zram.target

@@ -0,0 +1,6 @@
+[Unit]
+Description=OVOS zram targets
+Documentation=man:systemd.target(5)
+
+[Install]
+WantedBy=multi-user.target

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

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

buildroot-external/rootfs-overlay/usr/libexec/ovos-zram

@@ -0,0 +1,66 @@
+#!/bin/sh
+# Credits go to: https://github.com/home-assistant/operating-system/
+set -e
+
+#### Options ####
+
+TYPE=""
+MOUNT=""
+DEVICE=""
+SIZE=0
+
+#### Parse arguments ####
+
+while [ "$1" != "" ]; do
+    key=$1
+    case $key in
+        -t|--type)
+            TYPE=$2
+            shift
+            ;;
+        -s|--size)
+            SIZE=$2
+            shift
+            ;;
+        -m|--mount)
+            MOUNT=$2
+            shift
+            ;;
+        *)
+            echo "[Error] $0 : Argument '$1' unknown"
+            exit 1
+            ;;
+    esac
+    shift
+done
+
+# Valide Type
+if [ "$TYPE" != "swap" ]; then
+    echo "[Error] Type unknown!"
+    exit 1
+fi
+
+# Lookup device
+if [ "$TYPE" = "swap" ]; then
+    DEVICE="/dev/zram0"
+#elif [ "$MOUNT" = "var" ]; then
+#    DEVICE="/dev/zram1"
+#elif [ "$MOUNT" = "tmp" ]; then
+#    DEVICE="/dev/zram2"
+else
+    echo "[Error] No device for lookup!"
+    exit 1
+fi
+
+# Calc 20% of memory for ZRAM swap partition
+if [ "$TYPE" = "swap" ] && [ "$SIZE" -eq "0" ]; then
+    SIZE="$(awk '/MemTotal/{ print $2 * 0.20 }' /proc/meminfo)K"
+fi
+
+# Init device
+zramctl "$DEVICE" -s "$SIZE" -a lz4
+
+# Swap
+if [ "$TYPE" = "swap" ]; then
+    mkswap -L "ovos-zramswap" "$DEVICE"
+fi