How to get Resident Set Size (RSS)

I need to know physical memory consumption of my Go process in Linux. What I need is Resident Set Size (RSS).

runtime.ReadMemStats is not suitable because there is no way to get a size of a portion of a virtual memory that is resident.

syscall.Getrusage is not suitable because it returns only Maxrss that is maximal RSS during process life.

How can I query RSS in Go?

Answer

You can parse /proc/self/statm file. It contains only integers so it is easy to parse. Second field is RSS measured in pages.

func getRss() (int64, error) {
    buf, err := ioutil.ReadFile("/proc/self/statm")
    if err != nil {
        return 0, err
    }

    fields := strings.Split(string(buf), " ")
    if len(fields) < 2 {
        return 0, errors.New("Cannot parse statm")
    }

    rss, err := strconv.ParseInt(fields[1], 10, 64)
    if err != nil {
        return 0, err
    }

    return rss * int64(os.Getpagesize()), err
}