How to manage Goroutine affinity to CPU cores using runtime.LockOSThread()?

To manage Goroutine affinity to CPU cores using runtime.LockOSThread(), you can follow these steps:

Import the "runtime" package in your Go program: import "runtime"
Use the runtime.LockOSThread() function to lock the current Goroutine to the operating system thread it is already executing on.
Perform any necessary operations within this Goroutine to ensure it stays on the same CPU core.

Here's an example to demonstrate this:

package main

import (
	"fmt"
	"runtime"
	"sync"
)

func main() {
	// Specify the number of CPU cores to use
	numCores := runtime.NumCPU()
	runtime.GOMAXPROCS(numCores)

	var wg sync.WaitGroup

	// Create Goroutines
	for i := 0; i < 10; i++ {
		wg.Add(1)
		go func(index int) {
			defer wg.Done()

			// Lock this Goroutine to the operating system thread
			runtime.LockOSThread()

			// Perform any CPU-bound operations here

			fmt.Printf("Goroutine %d executed on CPU core %d\n", index, getCPUID())
		}(i)
	}

	wg.Wait()
}

// Utility function to get the ID of the current CPU core
func getCPUID() int {
	runtime.LockOSThread()
	defer runtime.UnlockOSThread()
	return runtime.GOMAXPROCS(-1) - runtime.NumGoroutine()%runtime.GOMAXPROCS(-1)
}

In this example, we first set the maximum number of CPU cores to use with runtime.GOMAXPROCS(numCores).

Inside each Goroutine, we call runtime.LockOSThread() to lock the Goroutine to the current operating system thread it is executing on. This ensures that the Goroutine will stay mapped to the CPU core it is currently running on.

Finally, we use the getCPUID() utility function to retrieve the ID of the CPU core that executes each Goroutine. This function uses runtime.GOMAXPROCS(-1) to get the number of CPU cores and runtime.NumGoroutine() to get the number of Goroutines.