golang runtime内存信息和回收

runtime包提供了操作runtime的一些函数，控制协程等。

package main

import (
	"runtime"
	"fmt"
	"time"
)
const COLS = 10000000
func main() {
	PrintMemUsage()

	var data [][]int
	for i := 0; i<5; i++ {
		a := make([]int, 0, COLS)
		data = append(data, a)
		PrintMemUsage()
		time.Sleep(time.Second)
	}
	//并不会强制内存回收
	data = nil
	PrintMemUsage()

	// 强制内存回收
	runtime.GC()
	PrintMemUsage()
}

func PrintMemUsage() {
	var m runtime.MemStats
	runtime.ReadMemStats(&m)
	fmt.Printf("Alloc = %v MiB", MB(m.Alloc))
	fmt.Printf("\tTotalAlloc = %v MiB", MB(m.TotalAlloc))
	fmt.Printf("\tSys = %v MiB", MB(m.Sys))
	fmt.Printf("\tNumGC = %v\n", m.NumGC)
}

func MB(b uint64) uint64 {
	return b / 1024 / 1024
}

运行结果如下:

Alloc = 0 MiB   TotalAlloc = 0 MiB      Sys = 67 MiB    NumGC = 0
Alloc = 76 MiB  TotalAlloc = 76 MiB     Sys = 201 MiB   NumGC = 0
Alloc = 152 MiB TotalAlloc = 152 MiB    Sys = 201 MiB   NumGC = 1
Alloc = 228 MiB TotalAlloc = 228 MiB    Sys = 333 MiB   NumGC = 2
Alloc = 305 MiB TotalAlloc = 305 MiB    Sys = 465 MiB   NumGC = 2
Alloc = 381 MiB TotalAlloc = 381 MiB    Sys = 466 MiB   NumGC = 3
Alloc = 381 MiB TotalAlloc = 381 MiB    Sys = 466 MiB   NumGC = 3
Alloc = 0 MiB   TotalAlloc = 381 MiB    Sys = 466 MiB   NumGC = 4

需要注意的是，GC调用会阻塞当前调用者，有可能会阻塞整个go进程。