Merge pull request #860 from bgray/806-set_cgroup_cpu_rt_before_joining

Set the cpu cgroup RT sched params before joining.

libcontainer/cgroups/fs/cpu.go

@@ -22,10 +22,48 @@ func (s *CpuGroup) Name() string {
 func (s *CpuGroup) Apply(d *cgroupData) error {
 	// We always want to join the cpu group, to allow fair cpu scheduling
 	// on a container basis
-	_, err := d.join("cpu")
+	path, err := d.path("cpu")
 	if err != nil && !cgroups.IsNotFound(err) {
 		return err
 	}
+	return s.ApplyDir(path, d.config, d.pid)
+}
+
+func (s *CpuGroup) ApplyDir(path string, cgroup *configs.Cgroup, pid int) error {
+	// This might happen if we have no cpu cgroup mounted.
+	// Just do nothing and don't fail.
+	if path == "" {
+		return nil
+	}
+	if err := os.MkdirAll(path, 0755); err != nil {
+		return err
+	}
+	// We should set the real-Time group scheduling settings before moving
+	// in the process because if the process is already in SCHED_RR mode
+	// and no RT bandwidth is set, adding it will fail.
+	if err := s.SetRtSched(path, cgroup); err != nil {
+		return err
+	}
+	// because we are not using d.join we need to place the pid into the procs file
+	// unlike the other subsystems
+	if err := writeFile(path, "cgroup.procs", strconv.Itoa(pid)); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (s *CpuGroup) SetRtSched(path string, cgroup *configs.Cgroup) error {
+	if cgroup.Resources.CpuRtPeriod != 0 {
+		if err := writeFile(path, "cpu.rt_period_us", strconv.FormatInt(cgroup.Resources.CpuRtPeriod, 10)); err != nil {
+			return err
+		}
+	}
+	if cgroup.Resources.CpuRtRuntime != 0 {
+		if err := writeFile(path, "cpu.rt_runtime_us", strconv.FormatInt(cgroup.Resources.CpuRtRuntime, 10)); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
@@ -45,15 +83,8 @@ func (s *CpuGroup) Set(path string, cgroup *configs.Cgroup) error {
 			return err
 		}
 	}
-	if cgroup.Resources.CpuRtPeriod != 0 {
-		if err := writeFile(path, "cpu.rt_period_us", strconv.FormatInt(cgroup.Resources.CpuRtPeriod, 10)); err != nil {
-			return err
-		}
-	}
-	if cgroup.Resources.CpuRtRuntime != 0 {
-		if err := writeFile(path, "cpu.rt_runtime_us", strconv.FormatInt(cgroup.Resources.CpuRtRuntime, 10)); err != nil {
-			return err
-		}
+	if err := s.SetRtSched(path, cgroup); err != nil {
+		return err
 	}
 
 	return nil

libcontainer/cgroups/fs/cpu_test.go

@@ -161,3 +161,49 @@ func TestInvalidCpuStat(t *testing.T) {
 		t.Fatal("Expected failed stat parsing.")
 	}
 }
+
+func TestCpuSetRtSchedAtApply(t *testing.T) {
+	helper := NewCgroupTestUtil("cpu", t)
+	defer helper.cleanup()
+
+	const (
+		rtRuntimeBefore = 0
+		rtRuntimeAfter  = 5000
+		rtPeriodBefore  = 0
+		rtPeriodAfter   = 7000
+	)
+
+	helper.writeFileContents(map[string]string{
+		"cpu.rt_runtime_us": strconv.Itoa(rtRuntimeBefore),
+		"cpu.rt_period_us":  strconv.Itoa(rtPeriodBefore),
+	})
+
+	helper.CgroupData.config.Resources.CpuRtRuntime = rtRuntimeAfter
+	helper.CgroupData.config.Resources.CpuRtPeriod = rtPeriodAfter
+	cpu := &CpuGroup{}
+	if err := cpu.ApplyDir(helper.CgroupPath, helper.CgroupData.config, 1234); err != nil {
+		t.Fatal(err)
+	}
+
+	rtRuntime, err := getCgroupParamUint(helper.CgroupPath, "cpu.rt_runtime_us")
+	if err != nil {
+		t.Fatalf("Failed to parse cpu.rt_runtime_us - %s", err)
+	}
+	if rtRuntime != rtRuntimeAfter {
+		t.Fatal("Got the wrong value, set cpu.rt_runtime_us failed.")
+	}
+	rtPeriod, err := getCgroupParamUint(helper.CgroupPath, "cpu.rt_period_us")
+	if err != nil {
+		t.Fatalf("Failed to parse cpu.rt_period_us - %s", err)
+	}
+	if rtPeriod != rtPeriodAfter {
+		t.Fatal("Got the wrong value, set cpu.rt_period_us failed.")
+	}
+	pid, err := getCgroupParamUint(helper.CgroupPath, "cgroup.procs")
+	if err != nil {
+		t.Fatalf("Failed to parse cgroup.procs - %s", err)
+	}
+	if pid != 1234 {
+		t.Fatal("Got the wrong value, set cgroup.procs failed.")
+	}
+}