Limit the amount of goroutnes started

main.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
 )
@@ -40,7 +41,10 @@ func main() {
 	to := flag.String("to", ".jpg", "Extension to transcode to")
 	nosafe := flag.Bool("nosafe", false, "Prevents backup of the original before encoding")
 	rm := flag.Bool("rm", false, "Removes the original after transcoding")
+	w := flag.Int("w", 8, "Workers")
 	flag.Parse()
+	
+	workers := make(chan struct{}, *w)
 
 	if _, ok := codecs[*to]; !ok {
 		Error.Println("Invalid extension")
@@ -55,7 +59,9 @@ func main() {
 	var wg sync.WaitGroup
 	for _, file := range flag.Args() {
 		wg.Add(1)
+		workers <- struct{}{}
 		go func(file string) {
+			defer func() { <-workers }()
 			defer wg.Done()
 			file = filepath.ToSlash(file)
 			file = filepath.Clean(file)
@@ -138,3 +144,27 @@ func main() {
 	}
 	wg.Wait()
 }
+
+func instrument() {
+	numGoroutines := runtime.NumGoroutine()
+
+	var m runtime.MemStats
+	runtime.ReadMemStats(&m)
+	// log.Printf("%+v", m)
+
+	sys := float64(m.Sys)
+	ramUsedMB := sys / 1024 / 1024
+	kbPerGoroutine := sys / 1024 / float64(numGoroutines)
+
+	var numGoroutinesPretty string
+	switch {
+	case numGoroutines >= 1_000_000:
+		numGoroutinesPretty = fmt.Sprintf("%.2fM", float64(numGoroutines)/1_000_000)
+	case numGoroutines >= 1_000:
+		numGoroutinesPretty = fmt.Sprintf("%.2fk", float64(numGoroutines)/1_000)
+	default:
+		numGoroutinesPretty = fmt.Sprintf("%d", numGoroutines)
+	}
+
+	fmt.Printf("\rNumber of active goroutines: %d (%s); RAM used: %.2f MB; KB per goroutine: %.2f", numGoroutines, numGoroutinesPretty, ramUsedMB, kbPerGoroutine)
+}