Linux Distributions & Architectural Deep Dives
Real-Time Linux Kernels with PREEMPT_RT
PREEMPT_RT makes most kernel code preemptible and converts spinlocks into sleeping locks, which bounds worst-case scheduling latency. That matters for industrial control, robotics, and trading systems where a late response is a failure, not a slowdown. Throughput drops slightly and driver behavior changes, so validation has to focus on tail latency under real load.
Points clés
- Set an explicit latency target and measure it with cyclictest under production-like load.
- Enable PREEMPT_RT through the distribution kernel or a maintained patch set, not a hand-merged tree.
- Isolate CPUs and pin real-time threads so housekeeping work cannot preempt them.
- Disable power management and frequency scaling features that introduce wake-up jitter.
- Audit drivers for long non-preemptible sections, since vendor code often breaks latency guarantees.
- Use trace tools such as ftrace and perf to locate the sources of latency spikes.
- Test thermal throttling and worst-case I/O because both can erase scheduling gains.
- Document the measured distribution, not just the average, and monitor tails in production.
Questions fréquentes
Is PREEMPT_RT fully merged upstream?
Most of it is. Check your kernel version and distribution backports before assuming behavior.
Does real-time mean faster?
No. It means more predictable. Average throughput often falls slightly.
Which workloads need it?
Control loops, robotics, audio, and trading paths with hard deadlines in the sub-millisecond range.
Can I run it in a container?
The host kernel provides the scheduling behavior; container configuration still has to avoid interference.
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