int map vs *int map

benchmark.txt

$ gotest -v ./ -bench=Benchmark -test.run=^$ -benchtime=100000000x
goos: linux
goarch: amd64
pkg: maptest
cpu: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
BenchmarkIntMap
BenchmarkIntMap-8          	100000000	        55.85 ns/op	       0 B/op	       0 allocs/op
BenchmarkIntPointerMap
BenchmarkIntPointerMap-8   	100000000	        24.43 ns/op	       0 B/op	       0 allocs/op

maps.go

package main

type mapType interface {
	Inc(string) int
	Dec(string) int
}

type intPointerMap map[string]*int

func (tqs intPointerMap) Inc(tenant string) int {
	ptr, ok := tqs[tenant]
	if !ok {
		size := 1
		tqs[tenant] = &size
		return size
	}
	(*ptr)++
	return *ptr
}

func (tqs intPointerMap) Dec(tenant string) int {
	ptr, ok := tqs[tenant]
	if !ok {
		return 0
	}
	(*ptr)--
	if *ptr == 0 {
		delete(tqs, tenant)
	}
	return *ptr
}

type intMap map[string]int

func (tqs intMap) Inc(tenant string) int {
	ptr, ok := tqs[tenant]
	if !ok {
		tqs[tenant] = 1
		return 1
	}
	ptr++
	tqs[tenant] = ptr
	return ptr
}

func (tqs intMap) Dec(tenant string) int {
	ptr, ok := tqs[tenant]
	if !ok {
		return 0
	}
	ptr--
	if ptr == 0 {
		delete(tqs, tenant)
	} else {
		tqs[tenant] = ptr
	}
	return ptr
}

maps_test.go

package main

import "testing"

func BenchmarkIntMap(b *testing.B) {
	m := make(intMap)
	benchmarkMap(b, m)
}

func BenchmarkIntPointerMap(b *testing.B) {
	m := make(intPointerMap)
	benchmarkMap(b, m)
}

func benchmarkMap(b *testing.B, m mapType) {
	b.ReportAllocs()
	for i := 0; i < b.N; i++ {
		m.Inc("a")
		m.Inc("b")
	}
	for i := 0; i < b.N; i++ {
		m.Dec("b")
		m.Dec("a")
	}
}