A test for Go map growth issue #20135

map_growth_test.go

package main

import (
    "fmt"
    "runtime"
)

func main() {
    mymap := make(map[string]*string)
    for i := 0; i < 1000000001; i++ {
        newkey := fmt.Sprintf("key_%d", i)
        mymap[newkey] = &newkey
        oldkey := fmt.Sprintf("key_%d", i-25)
        delete(mymap, oldkey)
        if i%1000000 == 0 {
            runtime.GC()
            var m runtime.MemStats
            runtime.ReadMemStats(&m)
            fmt.Printf("map = %v, alloc = %v, heap = %v, sys = %v\n", len(mymap), m.Alloc, m.HeapAlloc, m.Sys)
        }
    }

}