BQP/srcs/RobotNet10/Commons/RobotNet10.Realtime

RobotNet10.Realtime

Overview / Tổng quan

RobotNet10.Realtime là một wrapper library cho các tính năng realtime của Linux preempt_rt kernel. Library này cung cấp các API .NET để sử dụng các tính năng realtime như scheduling policies, CPU affinity, memory locking, và high-resolution timers.

Features / Tính năng

• Real-time Scheduling: SCHED_FIFO, SCHED_RR scheduling policies
• CPU Affinity: Pin threads to specific CPU cores
• Memory Locking: Prevent memory from being swapped to disk
• High-resolution Timers: timerfd-based timers for precise timing
• High-resolution Clocks: Access to CLOCK_MONOTONIC and other Linux clocks

Requirements / Yêu cầu

• Linux kernel with preempt_rt patch
• .NET 10.0 runtime
• Root privileges may be required for some operations (scheduling policies, memory locking)

Usage Examples / Ví dụ Sử dụng

Real-time Scheduling

using RobotNet10.Realtime;

// Set SCHED_FIFO policy with priority 50
RealtimeScheduler.SetSchedulingPolicy(RealtimeSchedulingPolicy.Fifo, 50);

// Get current policy and priority
var policy = RealtimeScheduler.GetSchedulingPolicy();
var priority = RealtimeScheduler.GetPriority();

// Change priority only
RealtimeScheduler.SetPriority(75);

CPU Affinity

using RobotNet10.Realtime;

// Pin current thread to CPU 0 and 1
CpuAffinity.SetAffinity(0, 1);

// Or use CpuAffinity class for more control
var affinity = new CpuAffinity();
affinity.AddCpu(0);
affinity.AddCpu(2);
affinity.Apply();

// Get current affinity
var currentAffinity = CpuAffinity.GetAffinity();
var cpus = currentAffinity.GetCpus(); // List of CPU numbers

Memory Locking

using RobotNet10.Realtime;

// Lock all current and future memory pages
MemoryLock.LockAll(MemoryLockFlags.Current | MemoryLockFlags.Future);

// Lock a specific array
var array = new byte[1024 * 1024];
var handle = MemoryLock.LockArray(array);
try
{
    // Use array...
}
finally
{
    handle.Free();
    MemoryLock.Unlock(handle.AddrOfPinnedObject(), new IntPtr(array.Length));
}

High-resolution Timer

using RobotNet10.Realtime;

// Create a periodic timer
using var timer = new RealtimeTimer(RealtimeClockType.Monotonic);
timer.SetPeriodic(TimeSpan.FromMilliseconds(10)); // 10ms interval

// In a loop, read expirations
while (running)
{
    ulong expirations = timer.ReadExpirations();
    if (expirations > 0)
    {
        // Timer expired, do work
        DoWork();
    }
}

// One-shot timer
timer.SetOneShot(TimeSpan.FromSeconds(5)); // Fire once after 5 seconds

High-resolution Clock

using RobotNet10.Realtime;

// Use monotonic clock for measuring elapsed time
var clock = new RealtimeClock(RealtimeClockType.Monotonic);
var startTime = clock.GetTimeSpan();

// Do work...

var elapsed = clock.GetTimeSpan() - startTime;
Console.WriteLine($"Elapsed: {elapsed.TotalMilliseconds} ms");

// Get clock resolution
var resolution = clock.GetResolution();
Console.WriteLine($"Clock resolution: {resolution.TotalNanoseconds} ns");

Important Notes / Lưu Ý Quan trọng

1. Root Privileges: Many real-time operations require root privileges. Run your application with sudo or set capabilities:

   sudo setcap cap_sys_nice+ep /path/to/your/app
   

2. Memory Locking Limits: The system has limits on how much memory can be locked. Check /proc/sys/vm/max_locked_memory.

3. Priority Range: Real-time priorities range from 1-99. Higher numbers = higher priority.

4. Platform Specific: This library only works on Linux. Use #if directives or runtime checks for cross-platform code.

5. Thread Safety: Most operations affect the current thread only. Use appropriate synchronization for multi-threaded applications.

Error Handling / Xử lý Lỗi

All operations throw RealtimeException on failure:

try
{
    RealtimeScheduler.SetSchedulingPolicy(RealtimeSchedulingPolicy.Fifo, 50);
}
catch (RealtimeException ex)
{
    Console.WriteLine($"Failed: {ex.Message}, errno: {ex.Errno}");
}

Related Documents / Tài liệu Liên quan

• Linux man pages: man 2 sched_setscheduler, man 2 timerfd_create, etc.
• Linux RT Wiki
• PREEMPT_RT Patch Documentation