In this file, we are adding and deleting 10 million elements in a map and see how it works.

mapswithoutpointer.go

package main

import (
	"fmt"
	"runtime"
)

func main() {
	n := 10000000
	m := make(map[int][128]byte)

	// It will return 0 hence, at this point nothing is added it allocate elements after this
	printAlloc()

	// Adding 10 million elements
	for i := 0; i < n; i++ {
		m[i] = [128]byte{}
	}
	// It will return the output in MB, that how much memory it took to store 10 million element in memory
	printAlloc()

	// Deleting 10 million elements
	for i := 0; i < n; i++ {
		// https://pkg.go.dev/builtin#delete
		delete(m, i)
	}

	// Triggers a manual GC
	runtime.GC()

	// Here, it will return the memory after the deallocation of KV pairs in a map
	printAlloc()

	// Keeps a reference to m so that the map isn’t collected
	runtime.KeepAlive(m)
}

func printAlloc() {
	var m runtime.MemStats
	var convertToMB uint64 = 1048576
	runtime.ReadMemStats(&m)
	fmt.Printf("%d MB\n", m.Alloc/convertToMB)
}



// Output -
0 MB
3694 MB
2347 MB