justjavac/moonbit-core-affinity

A MoonBit library for managing CPU core affinities to control thread-to-core binding.

moonbit-core-affinity

A MoonBit library for managing CPU core affinities to control thread-to-core binding.

This library enables precise control over CPU core affinity, allowing you to bind threads to specific cores. It's particularly useful for high-performance applications, real-time systems, and scenarios where you need to optimize CPU cache locality, reduce context switching overhead, or isolate workloads on dedicated cores.

Installation

Add justjavac/core_affinity to your dependencies:

moon update
moon add justjavac/core_affinity

Usage

fn main {
  // Get available core IDs
  let core_ids = @core_affinity.get_core_ids()
  println("Available core IDs: \{core_ids}")
  
  // Early return if no cores are available
  if core_ids.length() == 0 {
    println("No available cores found.")
    return
  }
  
  let first_core_id = core_ids[0]
  println("Setting affinity to core: \{first_core_id}")
  
  let success = @core_affinity.set_for_current([first_core_id])
  if not(success) {
    println("Failed to set affinity to core: \{first_core_id}")
    return
  }

  println("Successfully set affinity to core: \{first_core_id}")
}

Platform Support

Platform	get_core_ids()	set_for_current()	Implementation
Windows	✅	✅	Win32 API (GetProcessAffinityMask, SetThreadAffinityMask)
Linux	✅	✅	POSIX (sched_getaffinity, sched_setaffinity)
macOS	✅	✅	BSD/Darwin thread affinity APIs
Other Unix	⚠️	⚠️	Limited support, platform-dependent

• ✅ = Full support
• ⚠️ = Limited/platform-dependent support

Examples

Basic Usage

fn main {
  let cores = @core_affinity.get_core_ids()
  println("Available cores: \{cores}")
}

Single Core Binding

fn bind_to_first_core() -> Bool {
  let cores = @core_affinity.get_core_ids()
  if cores.length() > 0 {
    @core_affinity.set_for_current([cores[0]])
  } else {
    false
  }
}

Multi-Core Binding

fn bind_to_even_cores() -> Bool {
  let cores = @core_affinity.get_core_ids()
  let even_cores = []
  
  for core in cores {
    if core % 2 == 0 {
      even_cores.push(core)
    }
  }
  
  if even_cores.length() > 0 {
    @core_affinity.set_for_current(even_cores)
  } else {
    false
  }
}

Examples

You can find example usage in the example/ directory:

moon run --target native -C example .

License

MIT License - see LICENSE file for details.