バージョン別にgoroutineの中の処理が始まる遅延とgoステートメントの次の処理が始まる遅延を測ってみた。

goroutinebench.go

package main

import (
	"fmt"
	"sync"
	"time"
)

func BenchmarkGo(n int) time.Duration {
	ch := make(chan time.Duration, n)
	wg := sync.WaitGroup{}
	wg.Add(n)
	for i := 0; i < n; i++ {
		now := time.Now()
		go func(t time.Time) {
			d := time.Since(t)
			ch <- d
			wg.Done()
			time.Sleep(1000 * time.Millisecond)
		}(now)
	}
	wg.Wait()
	close(ch)
	tms := time.Duration(0)
	for d := range ch {
		tms += d
	}
	return time.Duration(int(tms) / n)
}

func BenchmarkGoNext(n int) time.Duration {
	tms := time.Duration(0)
	for i := 0; i < n; i++ {
		now := time.Now()
		go func(t time.Time) {
			time.Sleep(100 * time.Millisecond)
		}(now)
		tms += time.Since(now)
	}
	return time.Duration(int(tms) / n)
}

const N = 1000

func main() {
	time.Sleep(200 * time.Millisecond)
	fmt.Println("goroutine start deley:", BenchmarkGo(N))
	time.Sleep(200 * time.Millisecond)
	fmt.Println("goroutine next deley:", BenchmarkGoNext(N))
}

memo.txt

Now using version go1.4.3> go run goroutinebench.go
goroutine start deley: 818.705µs
goroutine next deley: 749ns

Now using version go1.5.3> go run goroutinebench.go
goroutine start deley: 50.511µs
goroutine next deley: 1.067µs

Now using version go1.6> go run goroutinebench.go
goroutine start deley: 75.578µs
goroutine next deley: 916ns