为什么在对象上使用new（）不会包含在Go的内存配置文件中？

Question

This is the code I am profiling:

package main

import (
    "testing"
)

type T struct {
    a int
    b int
}

func TestA(t *testing.T) {
    Add(1, 2)
}

func (t *T) Add() int {
    return t.a + t.b
}

func Add(a, b int) *T {
    t := new(T)
    t.a = a
    t.b = b
    return t
}

I ran the test using:

go test -memprofile mem.prof abc_test.go

But I can't find any allocation in the profiling file:

$ go tool pprof --alloc_objects main.test mem.prof
File: main.test
Type: alloc_objects
Time: Jul 9, 2018 at 9:40am (UTC)
Entering interactive mode (type "help" for commands, "o" for options)
(pprof) top
Showing nodes accounting for 0, 0% of 0 total
  flat  flat%   sum%        cum   cum%

Is there something wrong? To my understanding, the line t:= new(T) will cause an allocation.

Answer 1

First of all is better if you split your test and core function into two file. By that I mean in your main.go file should have

package main

type T struct {
    a int
    b int
}

func (t *T) Add() int {
    return t.a + t.b
}

func Add(a, b int) *T {
    t := new(T)
    t.a = a
    t.b = b
    return t
}

and main_test.go

package main

import "testing"

func TestA(t *testing.T) {
    Add(1, 2)
}

Then to resolve your anserw. Memprofiling is build into bench tool https://golang.org/pkg/runtime/pprof/ so you need to run your pprof profiling by using

go test -memprofile mem.prof -bench .

As you can see there was -bench flag missing in your command