#!/usr/bin/env bash
#
# Fix high swap usage on Proxmox without buying RAM
# https://www.zadran.net/guides/fix-high-swap-usage-on-proxmox
# Generated from the guide, last updated 2026-09-16.
#
# NO WARRANTY. This script is provided as is. You are responsible for
# understanding what it does before running it, and for the consequences.
# Take a backup first. See https://www.zadran.net/disclaimer
#
# Destructive steps are left commented out on purpose -- uncomment them
# only once you have understood what they do.

set -euo pipefail

# ---- Set these for your environment ----
# The VM or container you are working on, as shown by qm list or pct list.
VMID='100'
# What you are resizing that guest to. 6144 is 6 GiB.
NEW_MEM='6144'

free -h
swapon --show

{ for id in $(qm list | awk "NR>1 {print \$1}"); do qm config $id; done; \
  for id in $(pct list | awk "NR>1 {print \$1}"); do pct config $id; done; } \
| awk "/^memory:/ {sum += \$2} END {printf \"assigned to guests: %.1f GiB\n\", sum/1024}"

awk "/MemTotal/ {printf \"installed: %.1f GiB\n\", \$2/1048576}" /proc/meminfo

qm agent ${VMID} ping && qm config ${VMID} | grep -E "^(memory|balloon|agent):"

Get-Counter "\Memory\Committed Bytes" | Select-Object -ExpandProperty CounterSamples

free -h

qm set ${VMID} --memory ${NEW_MEM}

qm set ${VMID} --balloon 0

pct set ${VMID} --memory ${NEW_MEM}

qm set ${VMID} --onboot 0

qm shutdown ${VMID}

systemctl status ksmtuned

systemctl enable --now ksmtuned

cat /sys/kernel/mm/ksm/pages_sharing

# !! DESTRUCTIVE -- review, then uncomment to run:
# swapoff -a && swapon -a

free -h

cat /sys/module/zfs/parameters/zfs_arc_max

free -h

{ for id in $(qm list | awk "NR>1 {print \$1}"); do qm config $id; done; \
  for id in $(pct list | awk "NR>1 {print \$1}"); do pct config $id; done; } \
| awk "/^memory:/ {sum += \$2} END {printf \"assigned: %.1f GiB\n\", sum/1024}"