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Experimental Host Tuning

Experimental Content

The settings on this page are untested with ServoBox and provided as potential future directions for users who want to experiment.

Purpose

ServoBox's balanced mode already achieves excellent RT performance (~4μs avg, ~100-120μs max). The settings below are for:

  • Experimentation - Understanding latency sources in your system
  • 99.99% guarantees - Reducing spike latencies and frequency from ~1 per 10k to ~1 per 100k cycles
  • Future research - Community testing of advanced tuning approaches

If you try these and have interesting results, please share them on GitHub!

BIOS/UEFI Settings

Access your system BIOS (usually F2, Del, or F12 during boot). Settings vary by manufacturer:

1. Disable C-States

  • C-States → Disabled or C0/C1 Only
  • Package C-State Limit → C0/C1

Impact: System idles at 40-60W instead of 5-10W

2. Disable Turbo Boost

  • Intel: Intel Turbo Boost Technology → Disabled
  • AMD: Core Performance Boost → Disabled

Impact: CPU runs at base frequency (e.g., 3.4GHz instead of 5.0GHz boost)

3. Disable Hyper-Threading / SMT

  • Intel: Hyper-Threading Technology → Disabled
  • AMD: SMT Mode → Disabled

Impact: Available threads cut in half (16-core → 8 threads)

4. Disable Power Management

  • Intel SpeedStep / AMD Cool'n'Quiet → Disabled
  • EIST → Disabled

5. Reduce SMI Sources

  • PCIe ASPM → Disabled
  • USB Legacy Support → Disabled (⚠️ USB keyboard won't work until OS loads)

Runtime Configuration

If BIOS access isn't available:

Disable Turbo Boost:

# Intel
echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo

# AMD
echo 0 | sudo tee /sys/devices/system/cpu/cpufreq/boost

Limit C-States (add to /etc/default/grub):

intel_idle.max_cstate=1 processor.max_cstate=1

Most aggressive (prevents any idle):

idle=poll

Then:

sudo update-grub
sudo reboot

Disable SMT:

echo off | sudo tee /sys/devices/system/cpu/smt/control

Monitor Power and Temperature

# Install tools
sudo apt install lm-sensors

# Check temperatures
watch -n 1 sensors

# Check CPU package power (if supported)
sensors | grep Package

Expected power increase:

  • Turbo OFF: +5-10W
  • C-States OFF: +30-50W idle
  • idle=poll: +60-100W idle

Expected Results

In VMs (ServoBox):

  • Max latency: Still ~100-120μs
  • Spike frequency: May improve slightly
  • Average: Minimal change

On Bare-Metal RT Linux:

These settings can achieve <50μs max latency on bare-metal RT Linux systems.

Alternative: Bare-Metal RT

If you need <50μs consistently, consider bare-metal RT Linux instead of ServoBox:

Trade-offs: Lose GPU compatibility (NVIDIA), lose VM isolation, reduce host throughput

Share Your Results

Tried these settings? We'd love to hear about it!

  • Found improvements? Share your configuration and test results
  • Hit issues? Help others avoid pitfalls
  • Different hardware? AMD results especially welcome

Open a discussion on GitHub →