linux-rt

Ubuntu lowlatency kernel runtime profile for a dedicated RT core.

What this does

• Reserves one CPU (optionally with SMT sibling) as RT target.
• Moves IRQ affinity to non-RT CPUs.
• Stops irqbalance while profile is active.
• Sets CPU governors to performance.
• Sets kernel.sched_rt_runtime_us=-1 during profile.
• Restores previous settings with revert.

Files

• scripts/rt-core-profile.sh: apply/revert/status runtime tuning.
• scripts/run-cyclictest.sh: run latency benchmark and save results.
• scripts/benchmark-all.sh: run baseline + profiled tests and generate report.
• scripts/grub-rt-kargs.sh: persist RT kernel args in GRUB (reboot required).
• scripts/irq-map-advanced.sh: advanced IRQ mapping by action regex.
• scripts/plot-history.py: generate SVG trend graph from benchmark history CSV.
• scripts/rtos-like-profile.sh: aggressive runtime RT profile (single RT CPU island).
• scripts/run-rtos-like-validation.sh: stress + cyclictest validation for RTOS-like profile.

Quick start

cd linux-rt
chmod +x scripts/*.sh

# Show current status (no changes)
./scripts/rt-core-profile.sh status --rt-cpu 15

# Apply profile
sudo ./scripts/rt-core-profile.sh apply --rt-cpu 15

# Run 30s latency test on RT cpu 15
./scripts/run-cyclictest.sh 30 15

# Run baseline vs profiled in one shot and create report
./scripts/benchmark-all.sh 30 15

# Generate SVG graph from history CSV
./scripts/plot-history.py

# Revert profile
sudo ./scripts/rt-core-profile.sh revert

Advanced

# Show current GRUB/default cmdline and RT state
./scripts/grub-rt-kargs.sh status

# Persist RT boot args (reboot required)
sudo ./scripts/grub-rt-kargs.sh apply --rt-cpus 15

# Revert GRUB boot args to backup
sudo ./scripts/grub-rt-kargs.sh revert

# Preview IRQ map changes without applying
./scripts/irq-map-advanced.sh show --rt-pattern 'eth|enp|igc|ptp'
sudo ./scripts/irq-map-advanced.sh apply --rt-cpus 15 --rt-pattern 'eth|enp|igc|ptp' --dry-run

# Apply IRQ map and later restore
sudo ./scripts/irq-map-advanced.sh apply --rt-cpus 15 --rt-pattern 'eth|enp|igc|ptp'
sudo ./scripts/irq-map-advanced.sh restore

RTOS-Like Runtime Mode

# Check current runtime knobs
./scripts/rtos-like-profile.sh status --rt-cpu 15

# Apply aggressive runtime profile
sudo ./scripts/rtos-like-profile.sh apply --rt-cpu 15

# Validate under heavy non-RT load
./scripts/run-rtos-like-validation.sh 30 15

# Revert runtime profile
sudo ./scripts/rtos-like-profile.sh revert

Notes

• rt-core-profile.sh is runtime-only tuning (no reboot).
• grub-rt-kargs.sh is persistent boot-time tuning (reboot required).
• Recommended kernel: Ubuntu lowlatency.
• If RT workload and noise still interfere, isolate more than one core.