runtime: use cpuset_getaffinity for runtime.NumCPU() on FreeBSD

In FreeBSD when run Go proc under a given sub-list of
processors(e.g. 'cpuset -l 0 ./a.out' in multi-core system),
runtime.NumCPU() still return all physical CPUs from sysctl
hw.ncpu instead of account from sub-list.

Fix by use syscall cpuset_getaffinity to account the number of sub-list.

Fixes #15206

Change-Id: If87c4b620e870486efa100685db5debbf1210a5b
Reviewed-on: https://go-review.googlesource.com/29341
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

1 files changed, 126 insertions, 0 deletions

diff --git a/src/runtime/testdata/testprog/numcpu_freebsd.go b/src/runtime/testdata/testprog/numcpu_freebsd.go
new file mode 100644
index 0000000000..035c53470b
--- /dev/null
+++ b/src/runtime/testdata/testprog/numcpu_freebsd.go
@@ -0,0 +1,126 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"runtime"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+func init() {
+	register("FreeBSDNumCPU", FreeBSDNumCPU)
+	register("FreeBSDNumCPUHelper", FreeBSDNumCPUHelper)
+}
+
+func FreeBSDNumCPUHelper() {
+	fmt.Printf("%d\n", runtime.NumCPU())
+}
+
+func FreeBSDNumCPU() {
+	_, err := exec.LookPath("cpuset")
+	if err != nil {
+		// Can not test without cpuset command.
+		fmt.Println("OK")
+		return
+	}
+	_, err = exec.LookPath("sysctl")
+	if err != nil {
+		// Can not test without sysctl command.
+		fmt.Println("OK")
+		return
+	}
+	cmd := exec.Command("sysctl", "-n", "kern.smp.active")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		fmt.Printf("fail to launch '%s', error: %s, output: %s\n", strings.Join(cmd.Args, " "), err, output)
+		return
+	}
+	if bytes.Equal(output, []byte("1\n")) == false {
+		// SMP mode deactivated in kernel.
+		fmt.Println("OK")
+		return
+	}
+
+	list, err := getList()
+	if err != nil {
+		fmt.Printf("%s\n", err)
+		return
+	}
+	err = checkNCPU(list)
+	if err != nil {
+		fmt.Printf("%s\n", err)
+		return
+	}
+	if len(list) >= 2 {
+		err = checkNCPU(list[:len(list)-1])
+		if err != nil {
+			fmt.Printf("%s\n", err)
+			return
+		}
+	}
+	fmt.Println("OK")
+	return
+}
+
+func getList() ([]string, error) {
+	pid := syscall.Getpid()
+
+	// Launch cpuset to print a list of available CPUs: pid <PID> mask: 0, 1, 2, 3.
+	cmd := exec.Command("cpuset", "-g", "-p", strconv.Itoa(pid))
+	cmdline := strings.Join(cmd.Args, " ")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return nil, fmt.Errorf("fail to execute '%s': %s", cmdline, err)
+	}
+	pos := bytes.IndexRune(output, ':')
+	if pos == -1 {
+		return nil, fmt.Errorf("invalid output from '%s', ':' not found: %s", cmdline, output)
+	}
+
+	var list []string
+	for _, val := range bytes.Split(output[pos+1:], []byte(",")) {
+		index := string(bytes.TrimSpace(val))
+		if len(index) == 0 {
+			continue
+		}
+		list = append(list, index)
+	}
+	if len(list) == 0 {
+		return nil, fmt.Errorf("empty CPU list from '%s': %s", cmdline, output)
+	}
+	return list, nil
+}
+
+func checkNCPU(list []string) error {
+	listString := strings.Join(list, ",")
+	if len(listString) == 0 {
+		return fmt.Errorf("could not check against an empty CPU list")
+	}
+
+	// Launch FreeBSDNumCPUHelper() with specified CPUs list.
+	cmd := exec.Command("cpuset", "-l", listString, os.Args[0], "FreeBSDNumCPUHelper")
+	cmdline := strings.Join(cmd.Args, " ")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("fail to launch child '%s', error: %s, output: %s", cmdline, err, output)
+	}
+
+	// NumCPU from FreeBSDNumCPUHelper come with '\n'.
+	output = bytes.TrimSpace(output)
+	n, err := strconv.Atoi(string(output))
+	if err != nil {
+		return fmt.Errorf("fail to parse output from child '%s', error: %s, output: %s", cmdline, err, output)
+	}
+	if n != len(list) {
+		return fmt.Errorf("runtime.NumCPU() expected to %d, got %d when run with CPU list %s", len(list), n, listString)
+	}
+	return nil
+}