Adding oom_score_adj as a container config param.

Signed-off-by: Vishnu Kannan <vishnuk@google.com>

libcontainer/configs/config.go

@@ -127,6 +127,12 @@ type Config struct {
 	// If Rlimits are not set, the container will inherit rlimits from the parent process
 	Rlimits []Rlimit `json:"rlimits"`
 
+	// OomScoreAdj specifies the adjustment to be made by the kernel when calculating oom scores
+	// for a process. Valid values are between the range [-1000, '1000'], where processes with
+	// higher scores are preferred for being killed.
+	// More information about kernel oom score calculation here: https://lwn.net/Articles/317814/
+	OomScoreAdj int `json:"oom_score_adj"`
+
 	// AdditionalGroups specifies the gids that should be added to supplementary groups
 	// in addition to those that the user belongs to.
 	AdditionalGroups []string `json:"additional_groups"`

libcontainer/init_linux.go

@@ -5,7 +5,9 @@ package libcontainer
 import (
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
 	"os"
+	"strconv"
 	"strings"
 	"syscall"
 
@@ -238,6 +240,11 @@ func setupRlimits(config *configs.Config) error {
 	return nil
 }
 
+func setOomScoreAdj(oomScoreAdj int) error {
+	path := "/proc/self/oom_score_adj"
+	return ioutil.WriteFile(path, []byte(strconv.Itoa(oomScoreAdj)), 0700)
+}
+
 // killCgroupProcesses freezes then iterates over all the processes inside the
 // manager's cgroups sending a SIGKILL to each process then waiting for them to
 // exit.

libcontainer/integration/exec_test.go

@@ -878,3 +878,45 @@ func TestMountCgroupRW(t *testing.T) {
 		}
 	}
 }
+
+func TestOomScoreAdj(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+	root, err := newTestRoot()
+	ok(t, err)
+	defer os.RemoveAll(root)
+
+	rootfs, err := newRootfs()
+	ok(t, err)
+	defer remove(rootfs)
+
+	config := newTemplateConfig(rootfs)
+	config.OomScoreAdj = 200
+
+	factory, err := libcontainer.New(root, libcontainer.Cgroupfs)
+	ok(t, err)
+
+	container, err := factory.Create("test", config)
+	ok(t, err)
+	defer container.Destroy()
+
+	var stdout bytes.Buffer
+	pconfig := libcontainer.Process{
+		Args:   []string{"sh", "-c", "cat /proc/self/oom_score_adj"},
+		Env:    standardEnvironment,
+		Stdin:  nil,
+		Stdout: &stdout,
+	}
+	err = container.Start(&pconfig)
+	ok(t, err)
+
+	// Wait for process
+	waitProcess(&pconfig, t)
+	outputOomScoreAdj := strings.TrimSpace(string(stdout.Bytes()))
+
+	// Check that the oom_score_adj matches the value that was set as part of config.
+	if outputOomScoreAdj != strconv.Itoa(config.OomScoreAdj) {
+		t.Fatalf("Expected oom_score_adj %d; got %q", config.OomScoreAdj, outputOomScoreAdj)
+	}
+}

libcontainer/integration/execin_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"io"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -332,3 +333,49 @@ func TestExecinPassExtraFiles(t *testing.T) {
 		t.Fatalf("expected second pipe to receive '2', got '%s'", out2)
 	}
 }
+
+func TestExecInOomScoreAdj(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+	rootfs, err := newRootfs()
+	ok(t, err)
+	defer remove(rootfs)
+	config := newTemplateConfig(rootfs)
+	config.OomScoreAdj = 200
+	container, err := newContainer(config)
+	ok(t, err)
+	defer container.Destroy()
+
+	stdinR, stdinW, err := os.Pipe()
+	ok(t, err)
+	process := &libcontainer.Process{
+		Args:  []string{"cat"},
+		Env:   standardEnvironment,
+		Stdin: stdinR,
+	}
+	err = container.Start(process)
+	stdinR.Close()
+	defer stdinW.Close()
+	ok(t, err)
+
+	buffers := newStdBuffers()
+	ps := &libcontainer.Process{
+		Args:   []string{"/bin/sh", "-c", "cat /proc/self/oom_score_adj"},
+		Env:    standardEnvironment,
+		Stdin:  buffers.Stdin,
+		Stdout: buffers.Stdout,
+		Stderr: buffers.Stderr,
+	}
+	err = container.Start(ps)
+	ok(t, err)
+	waitProcess(ps, t)
+
+	stdinW.Close()
+	waitProcess(process, t)
+
+	out := buffers.Stdout.String()
+	if oomScoreAdj := strings.TrimSpace(out); oomScoreAdj != strconv.Itoa(config.OomScoreAdj) {
+		t.Fatalf("expected oomScoreAdj to be %d, got %s", config.OomScoreAdj, oomScoreAdj)
+	}
+}

libcontainer/setns_init_linux.go

@@ -21,6 +21,9 @@ func (l *linuxSetnsInit) Init() error {
 	if err := setupRlimits(l.config.Config); err != nil {
 		return err
 	}
+	if err := setOomScoreAdj(l.config.Config.OomScoreAdj); err != nil {
+		return err
+	}
 	if l.config.Config.Seccomp != nil {
 		if err := seccomp.InitSeccomp(l.config.Config.Seccomp); err != nil {
 			return err

libcontainer/standard_init_linux.go

@@ -47,6 +47,10 @@ func (l *linuxStandardInit) Init() error {
 	if err := setupRlimits(l.config.Config); err != nil {
 		return err
 	}
+	if err := setOomScoreAdj(l.config.Config.OomScoreAdj); err != nil {
+		return err
+	}
+
 	label.Init()
 	// InitializeMountNamespace() can be executed only for a new mount namespace
 	if l.config.Config.Namespaces.Contains(configs.NEWNS) {