Add the memory swappiness tuning support to libcontainer

Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>

cgroups/fs/memory.go

@@ -62,6 +62,11 @@ func (s *MemoryGroup) Set(path string, cgroup *configs.Cgroup) error {
 			return err
 		}
 	}
+	if cgroup.MemorySwappiness >= 0 && cgroup.MemorySwappiness <= 100 {
+		if err := writeFile(path, "memory.swappiness", strconv.FormatInt(cgroup.MemorySwappiness, 10)); err != nil {
+			return err
+		}
+	}
 
 	return nil
 }

cgroups/fs/memory_test.go

@@ -113,6 +113,34 @@ func TestMemorySetKernelMemory(t *testing.T) {
 	}
 }
 
+func TestMemorySetMemorySwappinessDefault(t *testing.T) {
+	helper := NewCgroupTestUtil("memory", t)
+	defer helper.cleanup()
+
+	const (
+		swappinessBefore = 60 //deafult is 60
+		swappinessAfter  = 0
+	)
+
+	helper.writeFileContents(map[string]string{
+		"memory.swappiness": strconv.Itoa(swappinessBefore),
+	})
+
+	helper.CgroupData.c.Memory = swappinessAfter
+	memory := &MemoryGroup{}
+	if err := memory.Set(helper.CgroupPath, helper.CgroupData.c); err != nil {
+		t.Fatal(err)
+	}
+
+	value, err := getCgroupParamUint(helper.CgroupPath, "memory.swappiness")
+	if err != nil {
+		t.Fatalf("Failed to parse memory.swappiness - %s", err)
+	}
+	if value != swappinessAfter {
+		t.Fatal("Got the wrong value, set memory.swappiness failed.")
+	}
+}
+
 func TestMemoryStats(t *testing.T) {
 	helper := NewCgroupTestUtil("memory", t)
 	defer helper.cleanup()

cgroups/systemd/apply_systemd.go

@@ -482,6 +482,12 @@ func joinMemory(c *configs.Cgroup, pid int) error {
 			return err
 		}
 	}
+	if c.MemorySwappiness >= 0 && c.MemorySwappiness <= 100 {
+		err = writeFile(path, "memory.swappiness", strconv.FormatInt(c.MemorySwappiness, 10))
+		if err != nil {
+			return err
+		}
+	}
 
 	return nil
 }

configs/cgroup.go

@@ -87,6 +87,9 @@ type Cgroup struct {
 	// Whether to disable OOM Killer
 	OomKillDisable bool `json:"oom_kill_disable"`
 
+	// Tuning swappiness behaviour per cgroup
+	MemorySwappiness int64 `json:"memory_swappiness"`
+
 	// Set priority of network traffic for container
 	NetPrioIfpriomap []*IfPrioMap `json:"net_prio_ifpriomap"`