cgroups: add support for blkio.weight_device

Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

cgroups/fs/blkio.go

@@ -35,6 +35,12 @@ func (s *BlkioGroup) Set(path string, cgroup *configs.Cgroup) error {
 		}
 	}
 
+	if cgroup.BlkioWeightDevice != "" {
+		if err := writeFile(path, "blkio.weight_device", cgroup.BlkioWeightDevice); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 

cgroups/fs/blkio_test.go

@@ -102,6 +102,35 @@ func TestBlkioSetWeight(t *testing.T) {
 	}
 }
 
+func TestBlkioSetWeightDevice(t *testing.T) {
+	helper := NewCgroupTestUtil("blkio", t)
+	defer helper.cleanup()
+
+	const (
+		weightDeviceBefore = "8:0 400"
+		weightDeviceAfter  = "8:0 500"
+	)
+
+	helper.writeFileContents(map[string]string{
+		"blkio.weight_device": weightDeviceBefore,
+	})
+
+	helper.CgroupData.c.BlkioWeightDevice = weightDeviceAfter
+	blkio := &BlkioGroup{}
+	if err := blkio.Set(helper.CgroupPath, helper.CgroupData.c); err != nil {
+		t.Fatal(err)
+	}
+
+	value, err := getCgroupParamString(helper.CgroupPath, "blkio.weight_device")
+	if err != nil {
+		t.Fatalf("Failed to parse blkio.weight_device - %s", err)
+	}
+
+	if value != weightDeviceAfter {
+		t.Fatal("Got the wrong value, set blkio.weight_device failed.")
+	}
+}
+
 func TestBlkioStats(t *testing.T) {
 	helper := NewCgroupTestUtil("blkio", t)
 	defer helper.cleanup()

cgroups/systemd/apply_systemd.go

@@ -216,6 +216,13 @@ func (m *Manager) Apply(pid int) error {
 		return err
 	}
 
+	// FIXME: Systemd does have `BlockIODeviceWeight` property, but we got problem
+	// using that (at least on systemd 208, see https://github.com/docker/libcontainer/pull/354),
+	// so use fs work around for now.
+	if err := joinBlkio(c, pid); err != nil {
+		return err
+	}
+
 	paths := make(map[string]string)
 	for sysname := range subsystems {
 		subsystemPath, err := getSubsystemPath(m.Cgroups, sysname)
@@ -417,3 +424,20 @@ func joinCpuset(c *configs.Cgroup, pid int) error {
 
 	return s.ApplyDir(path, c, pid)
 }
+
+// `BlockIODeviceWeight` property of systemd does not work properly, and systemd
+// expects device path instead of major minor numbers, which is also confusing
+// for users. So we use fs work around for now.
+func joinBlkio(c *configs.Cgroup, pid int) error {
+	path, err := getSubsystemPath(c, "blkio")
+	if err != nil {
+		return err
+	}
+	if c.BlkioWeightDevice != "" {
+		if err := writeFile(path, "blkio.weight_device", c.BlkioWeightDevice); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

configs/cgroup.go

@@ -46,6 +46,9 @@ type Cgroup struct {
 	// Specifies per cgroup weight, range is from 10 to 1000.
 	BlkioWeight int64 `json:"blkio_weight"`
 
+	// Weight per cgroup per device, can override BlkioWeight.
+	BlkioWeightDevice string `json:"blkio_weight_device"`
+
 	// set the freeze value for the process
 	Freezer FreezerState `json:"freezer"`