From 75dcb932f8b511bee5556a40ef15b50a92dd2d65 Mon Sep 17 00:00:00 2001
From: Stefan Agner <stefan@agner.ch>
Date: Wed, 22 Mar 2023 11:08:05 +0100
Subject: [PATCH] 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/kernel/hassos.config       |  3 +++
 .../rootfs-overlay/etc/sysctl.d/15-vm.conf    |  2 ++
 .../usr/lib/systemd/system/dev-zram0.swap     | 10 ---------
 .../lib/systemd/system/haos-swapfile.service  | 13 ++++++++++++
 .../lib/systemd/system/mnt-data-swapfile.swap |  8 +++++++
 .../usr/lib/systemd/system/zram-swap.service  | 15 -------------
 .../rootfs-overlay/usr/libexec/haos-swapfile  | 21 +++++++++++++++++++
 7 files changed, 47 insertions(+), 25 deletions(-)
 create mode 100644 buildroot-external/rootfs-overlay/etc/sysctl.d/15-vm.conf
 delete mode 100644 buildroot-external/rootfs-overlay/usr/lib/systemd/system/dev-zram0.swap
 create mode 100644 buildroot-external/rootfs-overlay/usr/lib/systemd/system/haos-swapfile.service
 create mode 100644 buildroot-external/rootfs-overlay/usr/lib/systemd/system/mnt-data-swapfile.swap
 delete mode 100644 buildroot-external/rootfs-overlay/usr/lib/systemd/system/zram-swap.service
 create mode 100755 buildroot-external/rootfs-overlay/usr/libexec/haos-swapfile

diff --git a/buildroot-external/kernel/hassos.config b/buildroot-external/kernel/hassos.config
index 31e076ef7..800d0b037 100644
--- a/buildroot-external/kernel/hassos.config
+++ b/buildroot-external/kernel/hassos.config
@@ -8,6 +8,9 @@ CONFIG_IKCONFIG_PROC=y
 CONFIG_MODULE_COMPRESS_NONE=y
 
 CONFIG_ZRAM=y
+CONFIG_ZSWAP=y
+CONFIG_ZSWAP_DEFAULT_ON=y
+CONFIG_ZSWAP_COMPRESSOR_DEFAULT_LZ4=y
 CONFIG_ZSMALLOC=y
 
 CONFIG_LRU_GEN=y
diff --git a/buildroot-external/rootfs-overlay/etc/sysctl.d/15-vm.conf b/buildroot-external/rootfs-overlay/etc/sysctl.d/15-vm.conf
new file mode 100644
index 000000000..8bd5d9135
--- /dev/null
+++ b/buildroot-external/rootfs-overlay/etc/sysctl.d/15-vm.conf
@@ -0,0 +1,2 @@
+# Decrease swapping to a minimum
+vm.swappiness=1
diff --git a/buildroot-external/rootfs-overlay/usr/lib/systemd/system/dev-zram0.swap b/buildroot-external/rootfs-overlay/usr/lib/systemd/system/dev-zram0.swap
deleted file mode 100644
index 8b12ac06d..000000000
--- a/buildroot-external/rootfs-overlay/usr/lib/systemd/system/dev-zram0.swap
+++ /dev/null
@@ -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
diff --git a/buildroot-external/rootfs-overlay/usr/lib/systemd/system/haos-swapfile.service b/buildroot-external/rootfs-overlay/usr/lib/systemd/system/haos-swapfile.service
new file mode 100644
index 000000000..6d6b49646
--- /dev/null
+++ b/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
diff --git a/buildroot-external/rootfs-overlay/usr/lib/systemd/system/mnt-data-swapfile.swap b/buildroot-external/rootfs-overlay/usr/lib/systemd/system/mnt-data-swapfile.swap
new file mode 100644
index 000000000..e7eca95db
--- /dev/null
+++ b/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
diff --git a/buildroot-external/rootfs-overlay/usr/lib/systemd/system/zram-swap.service b/buildroot-external/rootfs-overlay/usr/lib/systemd/system/zram-swap.service
deleted file mode 100644
index 8ec712237..000000000
--- a/buildroot-external/rootfs-overlay/usr/lib/systemd/system/zram-swap.service
+++ /dev/null
@@ -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
diff --git a/buildroot-external/rootfs-overlay/usr/libexec/haos-swapfile b/buildroot-external/rootfs-overlay/usr/libexec/haos-swapfile
new file mode 100755
index 000000000..8a3eb399a
--- /dev/null
+++ b/buildroot-external/rootfs-overlay/usr/libexec/haos-swapfile
@@ -0,0 +1,21 @@
+#!/bin/sh
+set -e
+
+swapfile="/mnt/data/swapfile"
+swapsize="$(awk '/MemTotal/{ print $2 * 0.33 }' /proc/meminfo)"
+
+
+if [ ! -s "${swapfile}" ] || [ "$(stat "${swapfile}" -c '%s')" -lt $((swapsize * 1024)) ]; then
+	# Check free space (in 4k blocks)
+	if [ "$(stat -f /mnt/data -c '%f')" -lt $((swapsize / 4)) ]; then
+		echo "[WARNING] Not enough space to allocate swapfile"
+		exit 1
+	fi
+
+	dd if=/dev/zero of="${swapfile}" bs=1k count="${swapsize}"
+fi
+
+if ! swaplabel "${swapfile}" > /dev/null 2>&1; then
+	/usr/lib/systemd/systemd-makefs swap "${swapfile}"
+fi
+