command-center/omp-docs/tools/linux-power-management.md

type, title, description, tags, timestamp

type	title	description	tags	timestamp
reference	Linux Power Management	Sleep/wake troubleshooting, NVIDIA GPU power management, and diagnostics for Linux systems.	power-management sleep nvidia	2026-08-06

General sleep/wake configuration and diagnostics for Linux systems: systemd sleep, kernel states, NVIDIA GPU power management, wake sources, and diagnostic tools. Fleet scope: the dev workstation blankpad is an AMD Cezanne APU exposing s2idle only (/sys/power/mem_sleep shows no deep); the NVIDIA section applied to the retired dankware Alienware m16 R2 (see Sleep/Wake Research) and to any future NVIDIA box.

---

Systemd Sleep Configuration

logind.conf (/etc/systemd/logind.conf)

Controls login manager behavior around sleep:

[Login]
HandlePowerKey=poweroff
HandleSleepKey=suspend
HandleHibernateKey=hibernate
HandleLidSwitch=suspend
HandleLidSwitchDocked=ignore
HoldoffTimeoutSec=5s
IdleAction=hibernate
IdleActionSec=30min

Key setting: HoldoffTimeoutSec — increase if sleep triggers are too aggressive.

sleep.conf (/etc/systemd/sleep.conf)

Controls the actual sleep behavior:

[Sleep]
AllowSuspend=yes
AllowHibernation=yes
AllowHybridSleep=yes
HibernateMode=platform+shutdown
HibernateDelaySec=1800

HibernateMode options:

• platform — ACPI platform sleep (faster, firmware-dependent)
• shutdown — classic shutdown-to-disk (slower, more compatible)
• shutdown+platform — try platform first, fall back to shutdown

Suspend-Then-Hibernate Flow

Suspend (RAM) --timeout--> Hibernate (disk)
    |
    +-- wake event --> Resume

Custom Sleep Hooks

Create /etc/systemd/system-sleep/ scripts for pre/post sleep actions:

#!/bin/bash
# /etc/systemd/system-sleep/hook
case "$1" in
    pre)  echo "Suspending..." ;;
    post) echo "Resumed!" ;;
esac

---

Kernel Sleep States

ACPI Sleep States

State	Name	Power	Wake Time	Description
S0	Working	Full	Instant	System is running
S1	Sleep (halted)	~10-20W	<1s	CPU halted, RAM refresh
S2	Sleep	~5-10W	~1s	CPU cache flushed
S3	Sleeping Standby	~1-5W	~1-2s	RAM retained, most power off
S4	Hibernate	0W	~10-30s	RAM written to disk
S5	Soft Off	0W	~5-10s	Powered off but can wake

Modern ACPI Sleep States (s2idle)

Modern laptops often only support s2idle (S0 idle):

$ cat /sys/power/mem_sleep
[s2idle] deep

Mode	Name	Power	Characteristics
s2idle	"Suspend to Idle"	3-8W	Shallow, firmware-managed, fast wake, higher drain
deep	S3	1-3W	Deeper sleep, slower wake, better battery

Setting Default Sleep State

Add to kernel command line (GRUB or systemd-boot):

mem_sleep_default=deep      # Prefer S3 deep sleep
mem_sleep_default=s2idle    # Force s2idle

For GRUB: Edit /etc/default/grub, add to GRUB_CMDLINE_LINUX_DEFAULT:

GRUB_CMDLINE_LINUX_DEFAULT="... mem_sleep_default=deep"

---

NVIDIA GPU Power Management

Enable NVIDIA Suspend Support

sudo systemctl enable nvidia-suspend.service
sudo systemctl enable nvidia-suspend-then-hibernate.service
sudo systemctl enable nvidia-hibernate.service

NVIDIA Module Parameters

Edit /etc/modprobe.d/nvidia.conf:

options nvidia NVreg_PreserveVideoMemoryAllocations=1
options nvidia NVreg_EnableS0ixPowerManagement=1

Check NVIDIA GPU State

# Is the NVIDIA GPU active?
lspci -vnn | grep -A 12 -i "vga"

# Force NVIDIA GPU to D3hot (fully off) before suspend
sudo tee /sys/bus/pci/devices/0000:01:00.0/power/control <<< auto

---

Diagnostic Tools

journalctl

# All sleep-related events in the last boot
journalctl -b -0 | grep -iE 'suspend|resume|sleep|wake|acpi'

# Real-time monitoring during a suspend attempt
journalctl -f &
systemctl suspend
# Wait for failure, then Ctrl+C

powertop

sudo powertop          # Interactive view
sudo powertop --calibrate   # One-time setup
sudo powertop --auto-tune   # Apply recommendations
sudo powertop --html=/tmp/report.html --csv=/tmp/report.csv

tlp — Advanced Power Management

sudo pacman -S tlp tlp-rdw   # Arch
sudo apt install tlp         # Debian/Ubuntu
sudo systemctl enable --now tlp
sudo tlp-stat

dmesg

dmesg | grep -iE 'suspend|resume|acpi|pm_'
dmesg -wH                    # Watch mode, human-readable

---

Wake Source Management

Checking Wake Sources

# What can wake the system?
cat /proc/acpi/wakeup | grep enabled

# What woke the system last time?
journalctl -b -1 | grep -iE 'PM: wakeup|wakeup source|acpi: wakeup'

Toggling Wake Sources

# Toggle a device's wake capability
echo XHCI | sudo tee /proc/acpi/wakeup
echo RP01 | sudo tee /proc/acpi/wakeup

Persistent Wake Source Configuration

Create a systemd service:

# /etc/systemd/system/config-wake-sources.service
[Unit]
Description=Configure ACPI wake sources
Before=sleep.target

[Service]
Type=oneshot
ExecStart=/bin/bash -c 'echo XHCI > /proc/acpi/wakeup'
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

---

Common Kernel Parameters

Parameter	Description
mem_sleep_default=deep	Prefer S3 deep sleep
pcie_aspm=force	Force ASPM (aggressive power saving)
pcie_aspm.policy=performance	Disable ASPM (fixes some issues)
acpi_osi=!	Hide OS identity from ACPI
usbcore.autosuspend=-1	Disable USB autosuspend

---

Testing Sleep Modes

# Suspend to RAM
systemctl suspend

# Hibernate to disk
systemctl hibernate

# Suspend then hibernate
systemctl suspend-then-hibernate

# Freeze (CPUs idle, RAM on)
systemctl freeze

Automated Stress Test

#!/bin/bash
for i in $(seq 1 10); do
    echo "=== Cycle $i ==="
    date
    echo mem | sudo tee /sys/power/state 2>/dev/null || systemctl suspend
    echo "Resume $i: SUCCESS"
    sleep 5
done

---

Quick Reference: Action Items

# 1. Enable NVIDIA suspend support
sudo systemctl enable nvidia-suspend.service
sudo systemctl enable nvidia-suspend-then-hibernate.service

# 2. Add NVIDIA power management module parameter
echo 'options nvidia NVreg_PreserveVideoMemoryAllocations=1' | sudo tee /etc/modprobe.d/nvidia-preserve.conf

# 3. Reboot
sudo reboot

# 4. Test suspend
systemctl suspend

# 5. After resume, check for errors
dmesg | tail -30
journalctl -b -0 | grep -iE 'error|fail|nvidia' | tail -20