You could run pprof to get a full breakdown.
But just looking at your code, it occurs to me that you have goroutines
that do pretty much no actual computation. It is basically testing the
concurrent performance of *append()*. Without looking at pprof, I can not
say for sure where the bottleneck is, but I suspect it would be in the
memory allocation. If you modify the program slightly (see
https://play.golang.org/p/5rUktxMGAf) to use the same memory for the
*[]string* after the first run (line 64), and actually do some computation
instead (lines 66-68), then you get the kind of threading performance you
would expect:
2017/10/27 13:57:05 Starting 1 threads
2017/10/27 13:57:15 Id routine: 0 rate: 192.307692
2017/10/27 13:57:15 Current total rate was 192.31 K/s
2017/10/27 13:57:46 Starting 2 threads
2017/10/27 13:57:56 Id routine: 0 rate: 196.078431
2017/10/27 13:57:56 Id routine: 1 rate: 196.078431
2017/10/27 13:57:56 Current total rate was 392.16 K/s
2017/10/27 13:58:32 Starting 3 threads
2017/10/27 13:58:42 Id routine: 1 rate: 192.307692
2017/10/27 13:58:42 Id routine: 2 rate: 192.307692
2017/10/27 13:58:42 Id routine: 0 rate: 196.078431
2017/10/27 13:58:42 Current total rate was 580.69 K/s
2017/10/27 13:56:53 Id routine: 1 rate: 192.307692
2017/10/27 13:56:53 Id routine: 3 rate: 192.307692
2017/10/27 13:56:53 Id routine: 0 rate: 192.307692
2017/10/27 13:56:53 Id routine: 2 rate: 188.679245
2017/10/27 13:56:53 Current total rate was 765.60 K/s
Hope this helps a bit.
Jake
On Friday, October 27, 2017 at 8:38:00 AM UTC-4, Christian LeMoussel wrote:
>
> Hi, I am studying about golang and use of goroutine.
> With this sample code, on my PC with 4 logical CPUs, I can't understand
> why I don't have any performance improvement.
>
> If I add in concurrency, the time it takes to do tends to slow down by the
> original without concurrency.
>
> 2017/10/27 13:57:17 Starting 1 threads
> 2017/10/27 13:57:27 Id routine: 0 rate: 232.558140
> 2017/10/27 13:57:27 Current total rate was 232.56 K/s
> 2017/10/27 13:57:27 Starting 1 threads
> 2017/10/27 13:57:37 Id routine: 0 rate: 357.142857
> 2017/10/27 13:57:37 Current total rate was 357.14 K/s
>
> 2017/10/27 13:58:04 Starting 2 threads
> 2017/10/27 13:58:14 Id routine: 0 rate: 131.578947
> 2017/10/27 13:58:14 Id routine: 1 rate: 129.870130
> 2017/10/27 13:58:14 Current total rate was 261.45 K/s
> 2017/10/27 13:58:14 Starting 2 threads
> 2017/10/27 13:58:24 Id routine: 1 rate: 144.927536
> 2017/10/27 13:58:24 Id routine: 0 rate: 151.515152
> 2017/10/27 13:58:24 Current total rate was 296.44 K/s
>
> 2017/10/27 13:59:15 Starting 3 threads
> 2017/10/27 13:59:25 Id routine: 2 rate: 94.339623
> 2017/10/27 13:59:25 Id routine: 0 rate: 92.592593
> 2017/10/27 13:59:25 Id routine: 1 rate: 90.090090
> 2017/10/27 13:59:25 Current total rate was 277.02 K/s
> 2017/10/27 13:59:25 Starting 3 threads
> 2017/10/27 13:59:35 Id routine: 2 rate: 92.592593
> 2017/10/27 13:59:35 Id routine: 0 rate: 90.090090
> 2017/10/27 13:59:35 Id routine: 1 rate: 101.010101
> 2017/10/27 13:59:35 Current total rate was 283.69 K/s
>
> 2017/10/27 14:00:12 Starting 4 threads
> 2017/10/27 14:00:22 Id routine: 1 rate: 56.818182
> 2017/10/27 14:00:22 Id routine: 3 rate: 56.818182
> 2017/10/27 14:00:22 Id routine: 0 rate: 61.349693
> 2017/10/27 14:00:22 Id routine: 2 rate: 62.500000
> 2017/10/27 14:00:22 Current total rate was 237.49 K/s
> 2017/10/27 14:00:22 Starting 4 threads
> 2017/10/27 14:00:32 Id routine: 1 rate: 67.114094
> 2017/10/27 14:00:32 Id routine: 3 rate: 61.349693
> 2017/10/27 14:00:32 Id routine: 0 rate: 57.803468
> 2017/10/27 14:00:32 Id routine: 2 rate: 65.789474
> 2017/10/27 14:00:32 Current total rate was 252.06 K/s
>
> And, here is the concurrent code with the goroutines:
>
> package main
>
> import (
> "fmt"
> "log"
> "sync"
> "time"
> )
>
> var (
> tryArr []string
> goroutineQuit = make(chan struct{})
> concurrencyMapHQ = struct {
> sync.RWMutex
> HQ map[int]float64
> }{HQ: make(map[int]float64)}
> )
>
> func rateStats() {
> var totalRate float64
> for i, rate := range concurrencyMapHQ.HQ {
> log.Printf("Id routine: %d rate: %f", i, rate)
> totalRate += rate
> }
>
> log.Printf("Current total rate was %.2f K/s", totalRate)
> }
>
> func stopThreads(threads int) {
> for i := 0; i < threads; i++ {
> goroutineQuit <- struct{}{}
> }
>
> rateStats()
> }
>
> func runThreads(threads int, steps int) {
> log.Printf("Starting %d threads", threads)
>
> for i := 0; i < threads; i++ {
> i := i
> go func(id int, steps int) {
> calculate(i, steps)
> }(i, steps)
> }
> }
>
> func calculate(idRoutine int, steps int) {
> var (
> possibles []string
> numBatchs = 0
> t1 = time.Now()
> )
>
> for {
> select {
> case <-goroutineQuit:
> return
> default:
> possibles = nil
>
> for _, nonce := range tryArr {
> possibles = append(possibles, nonce)
> }
>
> numBatchs++
> if numBatchs == 99 {
> t2 := time.Now()
>
> timeExecution := t2.Sub(t1) / time.Millisecond
>
> concurrencyMapHQ.Lock()
> concurrencyMapHQ.HQ[idRoutine] = float64(steps) /
> float64(timeExecution)
> concurrencyMapHQ.Unlock()
>
> numBatchs = 0
> t1 = t2
>
> }
> }
> }
> }
>
> func main() {
> threads := 4
> steps := 10000
>
> tryArr = make([]string, steps)
> for i := 0; i < steps; i++ {
> tryArr[i] = fmt.Sprintf("indice: %d", i)
> }
>
> for {
> runThreads(threads, steps)
> time.Sleep(10 * time.Second)
> stopThreads(threads)
>
> runThreads(threads, steps)
> time.Sleep(10 * time.Second)
> stopThreads(threads)
> }
> }
>
>
>
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