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os/exec: "fork/exec ... cannot allocate memory" on linux,!amd64 #31936

4a6f656c opened this issue May 9, 2019 · 1 comment


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commented May 9, 2019

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

$ go version
go version devel +5286b2a Thu May 9 14:58:03 2019 +0000 linux/s390x

Does this issue reproduce with the latest release?


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


What did you do?

On a linux/s390x LPAR with 12GB of RAM:

package main

import (

func main() {
        c := 8 * 1024 * 1024 * 1024
        a := make([]byte, c, c)
        for i := range a {
                a[i] = byte(i % 255)

        log.Print(exec.Command("sleep", "1").Run())
$ go build -o fork fork.go

What did you expect to see?

$ ./fork
2019/05/07 04:21:46 <nil>

What did you see instead?

$ ./fork
2019/05/07 03:59:54 fork/exec /bin/sleep: cannot allocate memory

This causes a production impact since various Go programs cannot fork/exec (including the Go compiler at times).

This is reproducable under Linux on most architectures aside from linux/amd64, where the problem has been addressed via issue #5838. The memory consumption will need to be altered depending on the available host memory.

@bradfitz bradfitz added the NeedsFix label May 9, 2019

@bradfitz bradfitz added this to the Go1.14 milestone May 9, 2019


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commented May 9, 2019

Change mentions this issue: syscall: implement rawVforkSyscall for remaining linux platforms

gopherbot pushed a commit that referenced this issue May 15, 2019

syscall: implement rawVforkSyscall for linux/ppc64x and linux/s390x
This allows the use of CLONE_VFORK and CLONE_VM for fork/exec, preventing
"fork/exec ...: cannot allocate memory" failures from occuring when attempting
to execute commands from a Go process that has a large memory footprint.
Additionally, this should reduce the latency of fork/exec on these platforms.

The same problem was addressed on linux/amd64 via issue #5838.

Updates #31936

Change-Id: I7ae0fbbeaa29cab944a49a11272a380d497eb2d0
Run-TryBot: Ian Lance Taylor <>
TryBot-Result: Gobot Gobot <>
Reviewed-by: Ian Lance Taylor <>
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