realtime-core

Deterministic timing primitives for real-time systems in Rust

realtime-core provides hardware-level timing precision for Rust applications requiring sub-millisecond jitter guarantees. Built on Linux PREEMPT_RT, io_uring, and SCHED_DEADLINE, it delivers the deterministic timing needed by real-time systems like audio processing, high-frequency trading, and robotics.

Key Features

• <2ms jitter guarantee on properly configured PREEMPT_RT systems
• Hardware-level timing using timerfd and io_uring backends
• SCHED_DEADLINE support for hard real-time scheduling
• CPU isolation to prevent scheduling interference
• Graceful fallback for systems without PREEMPT_RT
• Async-first with native tokio integration
• Zero-copy networking via io_uring for cross-language IPC

Quick Start

Installation

Add to your Cargo.toml:

[dependencies]
realtime-core = "0.1"
tokio = { version = "1.0", features = ["full"] }

Basic Usage

use realtime_core::{Timer, RealtimeExecutor};
use std::time::Duration;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Create a timer for 2 Hz (2 tokens per second)
    let mut timer = Timer::new(2.0)?;

    // Spawn a real-time task
    let executor = RealtimeExecutor::new()?;

    executor.spawn_realtime(async move {
        loop {
            timer.wait_for_tick().await?;
            // Process token at precise interval
            println!("Tick: {:?}", std::time::Instant::now());
        }
        #[allow(unreachable_code)]
        Ok::<_, realtime_core::TimerError>(())
    }).await?;

    Ok(())
}

Timeless Principle

// This is physics: time intervals are measured in nanoseconds
// The relationship between rate and interval is mathematical truth
let interval_ns = (1_000_000_000.0 / target_rate_hz) as u64;

This mathematical relationship never changes. Whether you're using PREEMPT_RT, io_uring, or a simple timerfd, the physics remains: rate (Hz) and interval (ns) are inversely proportional.

Performance Characteristics

On a properly configured PREEMPT_RT system (Linux 6.12+):

Metric	Target	Typical
P50 Latency	<500µs	~300µs
P95 Latency	<1ms	~700µs
P99 Latency	<2ms	~1.2ms
Worst-case Jitter	<2ms	~1.5ms
CPU Usage	<10%	~5%

On standard Linux (no PREEMPT_RT):

• P99 Latency: 5-10ms (higher jitter due to scheduling)
• CPU Usage: 15-20% (more context switches)

System Requirements

Minimum Requirements

• Linux 5.1+ (for io_uring support)
• Rust 1.75+
• CAP_SYS_NICE capability (for SCHED_DEADLINE)

For <2ms Jitter Guarantee

• Linux 6.12+ with PREEMPT_RT enabled
• Isolated CPU cores (kernel parameter: isolcpus=1)
• IRQ affinity configured to avoid RT cores
• SCHED_DEADLINE support (kernel 3.14+)

See System Configuration for detailed setup.

Core Abstractions

Timer

Hardware-level timing precision with nanosecond accuracy:

let mut timer = Timer::new(2.0)?; // 2 Hz
timer.wait_for_tick().await?; // Await precise interval

Scheduler

Real-time task scheduling with CPU isolation:

let scheduler = Scheduler::new()?;
scheduler.set_cpu_affinity([1])?; // Isolate to CPU 1
scheduler.set_deadline(1_000_000, 500_000, 500_000_000)?; // runtime, deadline, period (ns)

RealtimeExecutor

Async executor for real-time tasks:

let executor = RealtimeExecutor::with_config(ExecutorConfig {
    cpu_affinity: Some(vec![1]),
    scheduling_policy: SchedulingPolicy::Deadline,
    ..Default::default()
})?;

Integration with Equilibrium Tokens

realtime-core is the timing foundation for the equilibrium-tokens rate control system:

use equilibrium_tokens::RateEquilibrium;
use realtime_core::Timer;

// Rate equilibrium surface with <2ms jitter
let rate_surface = RateEquilibrium::new(
    2.0,  // 2 tokens/second
    0.5,  // min 0.5 Hz
    5.0,  // max 5 Hz
)?;

// Realtime-core ensures precise token emission
let mut timer = Timer::new(2.0)?;
loop {
    timer.wait_for_tick().await?;
    rate_surface.emit_token()?;
}

Use Cases

• Audio Processing: Sub-millisecond timing for VAD, noise suppression, ASR
• Rate Limiting: Precise token emission for conversation control
• Robotics: Hard real-time constraints for motor control
• High-Frequency Trading: Deterministic order execution
• Cross-Language IPC: Zero-copy message passing via io_uring

Documentation

• Architecture - System design, timeless principles, performance
• User Guide - Installation, usage, troubleshooting
• Developer Guide - Contributing, testing, benchmarking

Research Foundation

This library is based on comprehensive research into real-time processing systems:

• Linux PREEMPT_RT (6.12+): Sub-100µs worst-case latency, 8.7× jitter reduction
• io_uring: 30-50% jitter reduction vs. timerfd
• CUDA Graphs: Constant-time GPU kernel launch
• SCHED_DEADLINE: Hard real-time scheduling

See the research findings for details.

License

MIT License - see LICENSE for details.

Acknowledgments

Built on the shoulders of giants:

• Linux PREEMPT_RT developers (20-year milestone achievement)
• Tokio async runtime team
• io_uring and kernel contributors
• Real-time Linux community

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