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Kamran Khan
Kamran Khan

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😴 Get Deeper Sleep on Fedora: Optimizing Suspend-to-RAM

#linux

If you're running Fedora on a laptop or desktop, you might have noticed your system defaulting to a lighter sleep state (s2idle) instead of the power-saving "deep sleep" (S3 Suspend-to-RAM). This can lead to faster battery drain and more warmth when suspended.

In this guide, you'll learn how to:

  • ✅ Verify if your system supports "deep" suspend
  • ⚙️ Configure Fedora to use "deep" suspend by default
  • 🛠️ Add NVIDIA suspend/resume fix (optional)
  • 🛠️ Apply MSI/ASUS-specific ACPI tweak (optional)
  • 🔍 Understand the difference between sleep states

🎯 What is "Deep Sleep" (S3 Suspend)?

In the world of ACPI (Advanced Configuration and Power Interface), "deep sleep" typically refers to the S3 suspend state (Suspend-to-RAM). In this state:

  • The CPU, chipset, and most other components are powered down.
  • The RAM (Random Access Memory) remains powered to retain your session data.
  • The system consumes minimal power, making it ideal for battery life.
  • Resuming from S3 is fast, usually taking only a few seconds.

Fedora, by default, often uses s2idle (Suspend-to-Idle), which keeps more components powered on, consuming more energy, especially in modern hardware. While it's slightly faster to resume, S3 offers better power savings for true "deep sleep."

✅ Step 1: Verify "Deep Sleep" Support

Run:

cat /sys/power/mem_sleep
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Example output:

[s2idle] deep
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  • If deep is present, your system supports S3 suspend.
  • If it’s missing, check your BIOS/UEFI for power settings (sometimes called ACPI S3 or Legacy Sleep).

✅ Step 2: Configure Fedora for "Deep Sleep"

  1. Edit the sleep config: 
   sudo nano /etc/systemd/sleep.conf
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  1. Add the lines: 
   [Sleep]
   SuspendState=mem
   MemorySleepMode=deep
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  1. Save & exit, then reboot: 
   sudo reboot
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After this, suspend should now default to deep sleep (S3).

🟢 Step 3 (Optional, NVIDIA users): Add GPU Resume Fix

On systems with NVIDIA GPUs, you may experience black screens after resume. NVIDIA provides a kernel option to preserve VRAM allocations across suspend.

  1. Open GRUB config: 
   sudo nano /etc/default/grub
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  1. Find the line starting with GRUB_CMDLINE_LINUX= and add this at the end (inside the quotes): 
   nvidia.NVreg_PreserveVideoMemoryAllocations=1
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Example:

   GRUB_CMDLINE_LINUX="rhgb quiet mem_sleep_default=deep nvidia.NVreg_PreserveVideoMemoryAllocations=1"
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  1. Rebuild GRUB and reboot: 
   sudo grub2-mkconfig -o /boot/grub2/grub.cfg
   sudo reboot
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This helps the NVIDIA driver restore graphics properly after suspend.

🟠 Step 4 (Optional, MSI/ASUS laptops): ACPI Compatibility Tweak

Some MSI and ASUS laptops expose different suspend/resume behaviors depending on which OS they think is running. By default, Linux identifies itself as “Linux”, which may not unlock all ACPI features.

You can trick the firmware into using the same code paths as Windows 10/11 by adding:

acpi_osi=! acpi_osi="Windows 2020"
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to your kernel command line.

  1. Open GRUB config: 
   sudo nano /etc/default/grub
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  1. Update GRUB_CMDLINE_LINUX, for example: 
   GRUB_CMDLINE_LINUX="rhgb quiet mem_sleep_default=deep nvidia.NVreg_PreserveVideoMemoryAllocations=1 acpi_osi=! acpi_osi=\"Windows 2020\""
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  1. Rebuild GRUB and reboot: 
   sudo grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
   sudo reboot
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⚠️ Note:
This tweak is most useful on MSI and ASUS laptops that have issues resuming from suspend. If it causes problems (rare), just remove it again.

🔒 Understanding Sleep States (Briefly)

  • S0 (Working): Fully on.
  • S0ix (Modern Standby / s2idle): Low-power idle; fast resume but higher drain.
  • S3 (Suspend-to-RAM): Only RAM stays powered; lowest power, fast resume.
  • S4 (Hibernate): Saves memory to disk; no power use, slower resume.
  • S5 (Soft Off): Full shutdown.

📌 TL;DR Cheatsheet

Task Command Description
Check deep sleep support cat /sys/power/mem_sleep Shows if deep is available
Configure deep sleep Edit /etc/systemd/sleep.conf Sets S3 as the default
NVIDIA resume fix Add nvidia.NVreg_PreserveVideoMemoryAllocations=1 in GRUB Prevents black screen after resume
MSI/ASUS ACPI tweak Add acpi_osi=! acpi_osi="Windows 2020" in GRUB Improves suspend/resume on some laptops
Apply changes sudo reboot Reboot to apply settings
Test suspend systemctl suspend Puts the system into configured suspend state

🚀 Final Thoughts

By enabling deep sleep, you ensure your Fedora system consumes less power when suspended. If you’re on NVIDIA hardware, the extra kernel option makes suspend/resume more reliable. On MSI/ASUS laptops, the acpi_osi="Windows 2020" tweak can further stabilize wake-up.

Together, these tweaks give you cooler standby, longer battery life, and a more stable wake-up experience.

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