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

[4a6f656c]

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?

Yes.

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

linux/s390x

What did you do?

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

package main

import (
        "log"
        "os/exec"
)

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.

[gopherbot]

Change https://golang.org/cl/175697 mentions this issue: syscall: implement rawVforkSyscall for remaining linux platforms

[gopherbot]

Change https://golang.org/cl/189418 mentions this issue: syscall: implement rawVforkSyscall for linux/arm64

[acls]

It would be nice to also have this fixed in linux/arm. There was a fix in https://go-review.googlesource.com/c/go/+/175697/5 but was removed.