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POgoroutines causing major slowdowns and headaches
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  1. POgoroutines causing major slowdowns and headaches
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    copied!<p>I'm having something of a problem with goroutines. Why is it that this code executes in ~125ms (note sequential execution):</p> <pre><code>package main import ( "os/exec" "time" "fmt" ) func main() { cmd := exec.Command("lessc", "--yui-compress", "test.less") n := 2000 start := time.Now() for i := 0; i &lt; n; i++ { cmd.Run() } finish := time.Now() fmt.Printf("Program took %v to run\n", finish.Sub(start)) } </code></pre> <p>When this code takes about 20 seconds (concurrent execution using goroutines):</p> <pre><code>package main import ( "os/exec" "time" "fmt" ) func main() { cmd := exec.Command("lessc", "--yui-compress", "test.less") ch := make(chan bool) n := 2000 start := time.Now() for i := 0; i &lt; n; i++ { go lessc(ch, cmd) } fmt.Println(n, " goroutines started.") for i := 0; i &lt; n; i++ { _ = &lt;-ch } finish := time.Now() fmt.Printf("Program took %v to run\n", finish.Sub(start)) } func lessc(ch chan bool, c *exec.Cmd) { c.Run() ch &lt;- true } </code></pre> <p>Using go 1.0.3 on i7 720QM (4C/8T) 8GB RAM linux/x86-64 Also built and tested using 1.0.2 and got the same problem on the same machine.</p> <p>Edit: Solved by @jnml below. If anyone cares about the new fixed concurrent code here it is:</p> <pre><code>package main import ( "os/exec" "time" "fmt" ) func main() { ch := make(chan bool) n := 2000 start := time.Now() for i := 0; i &lt; n; i++ { go lessc(ch) } fmt.Println(n, " goroutines started.") for i := 0; i &lt; n; i++ { _ = &lt;-ch } finish := time.Now() fmt.Printf("Program took %v to run\n", finish.Sub(start)) } func lessc(ch chan bool) { cmd := exec.Command("lessc", "--yui-compress", "test.less") cmd.Run() ch &lt;- true } </code></pre>
 

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