Golang Goroutine内存泄漏

Question

I can't understand why memory is not freed. Memory profile shows that almost all of the memory used by runtime.malg. If I remove range over channel in DoSomeWork everything works fine.

Here of the output of fmt.Println:

Memory Acquired:  4196600
Memory Used    :  745192

Memory Acquired:  2651299576
Memory Used    :  393923440

Source code:

func DoSomeWork(work chan int) {
    for _ = range work {
    }
}

func main() {
    k := make(chan int)
    m := &runtime.MemStats{}
    runtime.ReadMemStats(m)
    fmt.Println("Memory Acquired: ", m.Sys)
    fmt.Println("Memory Used    : ", m.Alloc)

    wg := new(sync.WaitGroup)
    // generate a lot of goroutines that reads from channel
    for i:=0;i<1000000;i++ {
        wg.Add(1)
        go func() {
            DoSomeWork(k)
            wg.Done()
        }()
    }

    close(k)
    wg.Wait()

    // make GC
    runtime.GC()

    // show memory after garbage collector
    runtime.ReadMemStats(m)
    fmt.Println("Memory Acquired: ", m.Sys)
    fmt.Println("Memory Used    : ", m.Alloc)
}

Answer 1

There is no memory leak in your code. However you do cause a lot of memory to be reserved and that's what you see.

When i look for any kind of leak i prefer to do the test more then once. This is easily done whit your code. Just add:

func init(){
    for{
        main()
    }
}

The new output will reveal that no memory was lost during the run:

Memory Acquired:  2885880
Memory Used    :  14848
Memory Acquired:  2594885728
Memory Used    :  297108312
Memory Acquired:  2594885728
Memory Used    :  297108984
Memory Acquired:  2624143456
Memory Used    :  297108312
Memory Acquired:  2624143456
Memory Used    :  297108984
Memory Acquired:  2624143456
Memory Used    :  297108312
Memory Acquired:  2624143456
Memory Used    :  297108984
Memory Acquired:  2624143456
Memory Used    :  297108312
Memory Acquired:  2624143456
Memory Used    :  297108984
Memory Acquired:  2624143456
Memory Used    :  297108312