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moby--moby/pkg/cgroups/cgroups.go

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package cgroups
import (
"bufio"
"fmt"
"github.com/dotcloud/docker/pkg/mount"
"io"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"strings"
)
type Cgroup struct {
Name string `json:"name,omitempty"`
Parent string `json:"parent,omitempty"`
DeviceAccess bool `json:"device_access,omitempty"` // name of parent cgroup or slice
Memory int64 `json:"memory,omitempty"` // Memory limit (in bytes)
MemorySwap int64 `json:"memory_swap,omitempty"` // Total memory usage (memory + swap); set `-1' to disable swap
CpuShares int64 `json:"cpu_shares,omitempty"` // CPU shares (relative weight vs. other containers)
}
// https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
func FindCgroupMountpoint(subsystem string) (string, error) {
mounts, err := mount.GetMounts()
if err != nil {
return "", err
}
for _, mount := range mounts {
if mount.Fstype == "cgroup" {
for _, opt := range strings.Split(mount.VfsOpts, ",") {
if opt == subsystem {
return mount.Mountpoint, nil
}
}
}
}
return "", fmt.Errorf("cgroup mountpoint not found for %s", subsystem)
}
// Returns the relative path to the cgroup docker is running in.
func GetThisCgroupDir(subsystem string) (string, error) {
f, err := os.Open("/proc/self/cgroup")
if err != nil {
return "", err
}
defer f.Close()
return parseCgroupFile(subsystem, f)
}
func GetInitCgroupDir(subsystem string) (string, error) {
f, err := os.Open("/proc/1/cgroup")
if err != nil {
return "", err
}
defer f.Close()
return parseCgroupFile(subsystem, f)
}
func (c *Cgroup) Path(root, subsystem string) (string, error) {
cgroup := c.Name
if c.Parent != "" {
cgroup = filepath.Join(c.Parent, cgroup)
}
initPath, err := GetInitCgroupDir(subsystem)
if err != nil {
return "", err
}
return filepath.Join(root, subsystem, initPath, cgroup), nil
}
func (c *Cgroup) Join(root, subsystem string, pid int) (string, error) {
path, err := c.Path(root, subsystem)
if err != nil {
return "", err
}
if err := os.MkdirAll(path, 0755); err != nil && !os.IsExist(err) {
return "", err
}
if err := writeFile(path, "tasks", strconv.Itoa(pid)); err != nil {
return "", err
}
return path, nil
}
func (c *Cgroup) Cleanup(root string) error {
get := func(subsystem string) string {
path, _ := c.Path(root, subsystem)
return path
}
for _, path := range []string{
get("memory"),
get("devices"),
get("cpu"),
} {
os.RemoveAll(path)
}
return nil
}
func parseCgroupFile(subsystem string, r io.Reader) (string, error) {
s := bufio.NewScanner(r)
for s.Scan() {
if err := s.Err(); err != nil {
return "", err
}
text := s.Text()
parts := strings.Split(text, ":")
for _, subs := range strings.Split(parts[1], ",") {
if subs == subsystem {
return parts[2], nil
}
}
}
return "", fmt.Errorf("cgroup '%s' not found in /proc/self/cgroup", subsystem)
}
func writeFile(dir, file, data string) error {
return ioutil.WriteFile(filepath.Join(dir, file), []byte(data), 0700)
}
func (c *Cgroup) Apply(pid int) error {
// We have two implementation of cgroups support, one is based on
// systemd and the dbus api, and one is based on raw cgroup fs operations
// following the pre-single-writer model docs at:
// http://www.freedesktop.org/wiki/Software/systemd/PaxControlGroups/
//
// we can pick any subsystem to find the root
cgroupRoot, err := FindCgroupMountpoint("cpu")
if err != nil {
return err
}
cgroupRoot = filepath.Dir(cgroupRoot)
if _, err := os.Stat(cgroupRoot); err != nil {
return fmt.Errorf("cgroups fs not found")
}
if err := c.setupDevices(cgroupRoot, pid); err != nil {
return err
}
if err := c.setupMemory(cgroupRoot, pid); err != nil {
return err
}
if err := c.setupCpu(cgroupRoot, pid); err != nil {
return err
}
return nil
}
func (c *Cgroup) setupDevices(cgroupRoot string, pid int) (err error) {
if !c.DeviceAccess {
dir, err := c.Join(cgroupRoot, "devices", pid)
if err != nil {
return err
}
defer func() {
if err != nil {
os.RemoveAll(dir)
}
}()
if err := writeFile(dir, "devices.deny", "a"); err != nil {
return err
}
allow := []string{
// /dev/null, zero, full
"c 1:3 rwm",
"c 1:5 rwm",
"c 1:7 rwm",
// consoles
"c 5:1 rwm",
"c 5:0 rwm",
"c 4:0 rwm",
"c 4:1 rwm",
// /dev/urandom,/dev/random
"c 1:9 rwm",
"c 1:8 rwm",
// /dev/pts/ - pts namespaces are "coming soon"
"c 136:* rwm",
"c 5:2 rwm",
// tuntap
"c 10:200 rwm",
}
for _, val := range allow {
if err := writeFile(dir, "devices.allow", val); err != nil {
return err
}
}
}
return nil
}
func (c *Cgroup) setupMemory(cgroupRoot string, pid int) (err error) {
if c.Memory != 0 || c.MemorySwap != 0 {
dir, err := c.Join(cgroupRoot, "memory", pid)
if err != nil {
return err
}
defer func() {
if err != nil {
os.RemoveAll(dir)
}
}()
if c.Memory != 0 {
if err := writeFile(dir, "memory.limit_in_bytes", strconv.FormatInt(c.Memory, 10)); err != nil {
return err
}
if err := writeFile(dir, "memory.soft_limit_in_bytes", strconv.FormatInt(c.Memory, 10)); err != nil {
return err
}
}
// By default, MemorySwap is set to twice the size of RAM.
// If you want to omit MemorySwap, set it to `-1'.
if c.MemorySwap != -1 {
if err := writeFile(dir, "memory.memsw.limit_in_bytes", strconv.FormatInt(c.Memory*2, 10)); err != nil {
return err
}
}
}
return nil
}
func (c *Cgroup) setupCpu(cgroupRoot string, pid int) (err error) {
// We always want to join the cpu group, to allow fair cpu scheduling
// on a container basis
dir, err := c.Join(cgroupRoot, "cpu", pid)
if err != nil {
return err
}
if c.CpuShares != 0 {
if err := writeFile(dir, "cpu.shares", strconv.FormatInt(c.CpuShares, 10)); err != nil {
return err
}
}
return nil
}