How to Use Real-Time Kernels for Better Audio Performance

Real-time kernels can dramatically reduce latency and improve stability for audio production on Linux. For musicians, producers, and audio engineers, this difference means fewer dropouts, tighter synchronization, and smoother live performance. Understanding how to install, configure, and optimize a real-time kernel can help you achieve professional-grade audio responsiveness.

What is a Real-Time Kernel

A real-time (RT) kernel is a variant of the standard Linux kernel designed to process tasks with predictable timing. It prioritizes time-critical operations, ensuring that audio processing tasks are executed with minimal delay. In audio production, this allows sound servers, plugins, and DAWs to handle buffer operations without interruption.

Why Real-Time Kernels Improve Audio Performance

• Lower Latency
  Real-time kernels reduce scheduling delays, allowing audio threads to respond faster to system events.
• Stable Buffer Processing
  Reduced jitter prevents XRUNs (buffer overruns or underruns) in JACK and ALSA.
• Improved Multithreading for Audio
  Prioritizing audio threads ensures consistent performance when running multiple plugins or virtual instruments.
• Better for Live and Recording Workflows
  Real-time processing keeps synchronization tight during live performances or when recording multi-track sessions.

Installing a Real-Time Kernel

On Ubuntu and Debian-Based Systems

1. Update the package lists
   sudo apt update
2. Install the low-latency or RT kernel
   • Low-latency (recommended for most users):
     sudo apt install linux-lowlatency
   • Full real-time kernel:
     sudo apt install linux-image-rt-amd64 (Debian) or equivalent package on Ubuntu Studio.
3. Reboot and select the new kernel from GRUB.

On Arch Linux

1. Install the RT kernel
   sudo pacman -S linux-rt
2. Regenerate boot entries
   sudo grub-mkconfig -o /boot/grub/grub.cfg
3. Reboot to apply changes.

On Fedora

1. Install the RT kernel package
   sudo dnf install kernel-rt
2. Update the bootloader and reboot.

Configuring the System for Real-Time Audio

After installing the kernel, further tuning is required to fully benefit from its capabilities.

User Permissions

1. Add your user to the audio group
   sudo usermod -aG audio yourusername
2. Log out and back in to apply changes.

JACK or PipeWire Real-Time Settings

• JACK
  In qjackctl, enable real-time processing and set the priority between 70 and 90.
• PipeWire
  PipeWire uses systemd configuration. Ensure pipewire.conf allows real-time scheduling.

PAM Limits Configuration

Edit /etc/security/limits.d/audio.conf:

@audio   -  rtprio     95
@audio   -  memlock    unlimited

This gives audio applications permission to use high-priority threads and lock memory, preventing swap-related dropouts.

Optimizing Buffer Sizes and Sample Rates

• Lower buffer sizes reduce latency but increase CPU demand. Start with 128 or 256 frames and test stability.
• Use sample rates that match your audio interface. 48kHz or 96kHz works best for real-time processing.
• Monitor XRUNs in JACK or PipeWire. If they occur, raise the buffer size incrementally.

CPU and Power Settings

• Use a performance CPU governor:
  sudo cpupower frequency-set -g performance
• Disable C-states or deep sleep modes in BIOS if low latency is critical.
• Avoid running heavy background processes during sessions.

Testing Real-Time Performance

Using JACK

1. Start JACK with real-time scheduling enabled.
2. Gradually reduce buffer size and monitor for XRUNs.
3. If dropouts occur, check system logs for priority issues.

Using Stress Tests

Install rt-tests:

sudo apt install rt-tests
cyclictest -n -p99 -i1000 -l10000

This measures latency under real-time conditions. Look for minimal maximum latency.

When to Use a Real-Time Kernel

• Live performance with MIDI controllers or digital instruments
• Recording sessions requiring ultra-low latency monitoring
• Complex plugin chains in a DAW where stable timing is critical
• Experimental setups like modular software synthesis

Alternatives to Full Real-Time Kernels

Not all systems need a full RT kernel. Many users achieve reliable low-latency audio with a low-latency kernel or by fine-tuning system settings. Test both before committing to real-time-only workflows.

Maintenance and Updates

• Keep the kernel updated to ensure compatibility with audio applications.
• After major updates, retest real-time performance settings.
• Backup configurations for JACK or PipeWire to restore quickly after system changes.