Added a new method cgroups.GetStats() which will return a cgroups.Stats object which will contain all the available cgroup Stats.

Remove old Stats interface in libcontainers cgroups package.
Changed Stats to use unit64 instead of int64 to prevent integer overflow issues.
Updated unit tests.

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)

libcontainer/cgroups/fs/memory.go

@@ -2,10 +2,11 @@ package fs
 
 import (
 	"bufio"
-	"fmt"
 	"os"
 	"path/filepath"
 	"strconv"
+
+	"github.com/dotcloud/docker/pkg/libcontainer/cgroups"
 )
 
 type memoryGroup struct {
@@ -50,17 +51,16 @@ func (s *memoryGroup) Remove(d *data) error {
 	return removePath(d.path("memory"))
 }
 
-func (s *memoryGroup) Stats(d *data) (map[string]int64, error) {
-	paramData := make(map[string]int64)
+func (s *memoryGroup) GetStats(d *data, stats *cgroups.Stats) error {
 	path, err := d.path("memory")
 	if err != nil {
-		return nil, err
+		return err
 	}
 
 	// Set stats from memory.stat.
 	statsFile, err := os.Open(filepath.Join(path, "memory.stat"))
 	if err != nil {
-		return nil, err
+		return err
 	}
 	defer statsFile.Close()
 
@@ -68,23 +68,22 @@ func (s *memoryGroup) Stats(d *data) (map[string]int64, error) {
 	for sc.Scan() {
 		t, v, err := getCgroupParamKeyValue(sc.Text())
 		if err != nil {
-			return nil, err
+			return err
 		}
-		paramData[t] = v
+		stats.MemoryStats.Stats[t] = v
 	}
 
 	// Set memory usage and max historical usage.
-	params := []string{
-		"usage_in_bytes",
-		"max_usage_in_bytes",
+	value, err := getCgroupParamInt(path, "memory.usage_in_bytes")
+	if err != nil {
+		return err
 	}
-	for _, param := range params {
-		value, err := getCgroupParamInt(path, fmt.Sprintf("memory.%s", param))
-		if err != nil {
-			return nil, err
-		}
-		paramData[param] = value
+	stats.MemoryStats.Usage = value
+	value, err = getCgroupParamInt(path, "memory.max_usage_in_bytes")
+	if err != nil {
+		return err
 	}
+	stats.MemoryStats.MaxUsage = value
 
-	return paramData, nil
+	return nil
 }