为什么Golang结构体有时要用指针 分析大型结构体的拷贝开销

package main

import (
    "fmt"
    "time"
)

type BigStruct struct {
    ID          int
    Name        string
    Description string
    Data        [1000]int // Large data
}

func byValue(s BigStruct) {
    // Do something with s
    _ = s.ID
}

func byPointer(s *BigStruct) {
    // Do something with s
    _ = s.ID
}

func main() {
    bigStruct := BigStruct{
        ID:          1,
        Name:        "Large Structure",
        Description: "This is a large structure for testing.",
    }

    // By Value
    startTime := time.Now()
    for i := 0; i < 100000; i++ {
        byValue(bigStruct)
    }
    duration := time.Since(startTime)
    fmt.Printf("By Value: %v\n", duration)

    // By Pointer
    startTime = time.Now()
    for i := 0; i < 100000; i++ {
        byPointer(&bigStruct)
    }
    duration = time.Since(startTime)
    fmt.Printf("By Pointer: %v\n", duration)
}

package main

import (
    "fmt"
    "unsafe"
)

type SmallStruct struct {
    ID   int
    Name string
}

type BigStruct struct {
    ID          int
    Name        string
    Description string
    Data        [1000]int
}

func main() {
    small := SmallStruct{ID: 1, Name: "Small"}
    big := BigStruct{ID: 1, Name: "Big"}

    fmt.Printf("Size of SmallStruct: %d bytes\n", unsafe.Sizeof(small))
    fmt.Printf("Size of BigStruct: %d bytes\n", unsafe.Sizeof(big))
}

package main

import "fmt"

type Counter struct {
    Value int
}

// 值接收者
func (c Counter) IncrementByValue() {
    c.Value++ // 修改的是副本
}

// 指针接收者
func (c *Counter) IncrementByPointer() {
    c.Value++ // 修改的是原始值
}

func main() {
    counter1 := Counter{Value: 0}
    counter1.IncrementByValue()
    fmt.Printf("Counter1 Value (By Value): %d\n", counter1.Value) // Output: 0

    counter2 := Counter{Value: 0}
    counter2.IncrementByPointer()
    fmt.Printf("Counter2 Value (By Pointer): %d\n", counter2.Value) // Output: 1
}