goroutine schedule and memory co

goroutines schedule by os,nobody can detertine how one goroutine run,you can run this code:

package main

import (
    "fmt"
    "os"
    "sync"
)

func data_init(size int) []int {
    ints := make([]int, 0)
    for i := 0; i < size; i++ {
        ints = append(ints, i)
    }
    return ints
}
//just go func in loop without  parameter
func data_handle1(wgp *sync.WaitGroup, data *[]int) {
    actual_data := *data
    wg := *wgp
    for _, value := range actual_data {
        wg.Add(1)
        go func() { // schedule this goroutine by os,but last value in actual_data can pass to heap memory,fucntion can get this data 
            wg.Done()
            fmt.Println(value, ",pid=", os.Getpid())
        }()
    }
    wg.Wait()
}

//run in for loop scop,but goroutine function passed by  string type of value
func data_handle2(wgp *sync.WaitGroup, data *[]int) {
    actual_data := *data
    wg := *wgp
    for _, value := range actual_data {
        wg.Add(1)
        go func(value int) {
            wg.Done()
            fmt.Println(value, ",pid=", os.Getpid())
        }(value)
    }
    wg.Wait()
}
func main() {
    size := 6
    var wg sync.WaitGroup
    data := data_init(size)
    fmt.Println("data:", data)
    fmt.Println("--------------go func() in loop-----------")
    data_handle1(&wg, &data)
    fmt.Println("--------------go func(string) in loop-----------")
    data_handle2(&wg, &data)
}

Jietu20171114-160122@2x.jpg

gorooutine just cost a few kb,just run that code:

package main

import (
    "fmt"
    "runtime"
    "sync"
)

func main() {
    memConsumed := func() uint64 {
        runtime.GC()
        var s runtime.MemStats
        runtime.ReadMemStats(&s)
        return s.Sys
    }
    var c <-chan interface{}
    var wg sync.WaitGroup
    noop := func() {
        wg.Done()
        <-c
    }
    const numGoroutines = 1000000
    wg.Add(numGoroutines)
    before := memConsumed()
    for i := numGoroutines; i > 0; i-- {
        go noop()  //noop already block,but every runing in own goroutine
    }
    wg.Wait()
    after := memConsumed()
    fmt.Printf("total %d goroutines,each consumed memory %.3fkb\n", numGoroutines, float64(after-before)/numGoroutines/1000)
}

Jietu20171114-160633@2x.jpg