You might want to take a look at this video https://youtu.be/ySy3sR1LFCQ which
shows some common issues with concurrency in go and how to use pprof and
the go tracer to inspect and fix them.
Hope this helps a bit.
Yannic
On Friday, October 27, 2017 at 2:38:00 PM UTC+2, 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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