to run or not to run goroutine

exp-goroutine.go

package pool

import (
	"os"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

var (
	jobDuration       = 10 * time.Millisecond
	maxJobLimit       = 10000
	jobNumber   int64 = 0
	job               = make(chan struct{}, maxJobLimit)
	done              = make(chan struct{}, maxJobLimit)
)

func TestMain(m *testing.M) {
	// start pool of goroutines
	gopool(maxJobLimit, job, done)
	os.Exit(m.Run())
}

func BenchmarkGoroutineCreation(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		go func(n int) {
			if n < 0 {
				return
			}
		}(i)
	}

}

func BenchmarkNoGoroutineCreation(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		func(n int) {
			if n < 0 {
				return
			}
		}(i)

	}

}

func BenchmarkConcurOp(b *testing.B) {
	var wg sync.WaitGroup

	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		wg.Add(1)
		go func() {
			time.Sleep(jobDuration)
			wg.Done()
		}()
	}

	wg.Wait()

}

func BenchmarkSeqOp(b *testing.B) {

	f := func() {
		time.Sleep(jobDuration)
	}

	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		f()
	}

}

func BenchmarkConcurOpInPool(b *testing.B) {
	b.ReportAllocs()

	for i := 0; i < b.N; i++ {
		job <- struct{}{}
		//		log.Println("job started", i)
		atomic.AddInt64(&jobNumber, 1)
		if atomic.LoadInt64(&jobNumber) > int64(maxJobLimit-2) {
			select {
			case <-done:
				atomic.AddInt64(&jobNumber, -1)

			}
		}

	}

}

func gopool(n int, job, done chan struct{}) {
	for i := 0; i < n; i++ {
		go func() {
			for {
				select {
				case <-job:
					time.Sleep(jobDuration)
					done <- struct{}{}
					break
				}
			}
		}()
	}
}
/*
PASS
BenchmarkGoroutineCreation-4   	 5000000	       510 ns/op	       0 B/op	       0 allocs/op
BenchmarkNoGoroutineCreation-4 	2000000000	         2.14 ns/op	       0 B/op	       0 allocs/op
BenchmarkConcurOp-4      	 1000000	      2913 ns/op	     250 B/op	       1 allocs/op
BenchmarkSeqOp-4         	     300	  10096241 ns/op	      64 B/op	       1 allocs/op
BenchmarkConcurOpInPool-4	 2000000	      1288 ns/op	      64 B/op	       1 allocs/op
ok  	tests/goroutines	19.651s
*/