Inside the RT Patch
summary
Explains that CONFIG_PREEMPT_RT turns Linux into a mostly preemptible, deterministic kernel by converting many spinlocks to sleeping mutexes, pushing hard IRQs into threaded IRQs, and adding priority inheritance plus adaptive spinlocks; claims worst‑case jitter drops from milliseconds to microseconds (examples: mainline spikes to 2–40 ms, RT often 25–40 µs; presenter reports a cyclic test max ~31 µs). Notes maintenance status (3.2/3.4 RT trees), uses ftrace and ktest for measurement, and says preempt_lazy recovers throughput while preserving bounded priority inversion.
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chapters (20)
- 0:00Inside The RT Patch
- 1:49Understanding PREEMPT_RT
- 4:33Trebuchet
- 4:52Where to get the RT patch
- 6:23What is a Real-time OS?
- 9:27The Goal of PREEMPT_RT
- 11:14No Preemption
- 12:10Voluntary Preemption
- 16:35Fully Preemptible Kernel The RT Patch
- 20:06PREEMPT_LAZY
- 22:23Priority Inheritance
- 24:00Unbounded Priority Inversion
- 28:42Interrupt Latency
- 29:10Interrupt Thread
- 29:42Non-Thread IROS
- 34:09Threaded Interrupts
- 39:48preempt disable
- 41:59per_cpu
- 47:55Real-Time User Space
- 48:31Questions?
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38mThe Status of the Preempt-RT Patch
36mJourney of improving RT performance on Single CPU equipped PREEMPT_RT Linux- 36mJourney of improving RT performance on Single CPU equipped PREEMPT_RT Linux
42mBoF: Realtime Linux