os/exec: exec.Command("cat", "/proc/uptime") memory leak in golang 1.9

[yxdming]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.9

What operating system and processor architecture are you using (go env)?

SuSE

What did you do?

When i use exec.Command("cat", "/proc/uptime") in my programe, i found that there is a memory leak in this call. The memory used by program goes high after 2 hours from initial 20MB to 105MB and increasing continuously unless i restart the programe. The code as below.

func GetSecondFromSystemStart() int {
	out, err := exec.Command("cat", "/proc/uptime").Output()
	if(err != nil){
		logger.ErrorLog(MODULE_NAME, "get time from start fail:%s", err.Error())
	}else{
		vTimeString := strings.Split(string(out), ".")
		if(len(vTimeString) == 0){
			logger.ErrorLog(MODULE_NAME, "get time from start fail")
		}else{
			sed, e := strconv.Atoi(vTimeString[0])
			if(e != nil){
				logger.ErrorLog(MODULE_NAME, "get time from start fail:%s", e.Error())
			}else{
				logger.DebugLog(MODULE_NAME, "get time from start:%d", sed)
				return sed
			}
		}
	}
	return 0
}

[ALTree]

Can you reproduce this with Go 1.11 (https://golang.org/dl)? Go1.9 is quite old and it's no longer maintained.

[mvdan]

Also please check your pprof memory profiles. If the number of in-use heap objects keeps increasing over time, it will tell you where the allocations are coming from.

[bradfitz]

Unrelated: it's much more efficient to use ioutil.ReadFile to read /proc/uptime instead of starting a child process.

But in any case, the code above shouldn't leak anything. Please provide a minimal repro to demonstrate the problem.

[yxdming]

@ALTree
Thanks.
When i use Go 1.11, it seam that everything works better. I will test more times and close this issue if the memory doesn't increase any more.