@@ -3,6 +3,7 @@ package snapshot

 import (

 	"context"

 	"path/filepath"

+	"strconv"

 	"strings"

 	"sync"

@@ -331,7 +332,69 @@ func (s *snapshotter) Update(ctx context.Context, info snapshots.Info, fieldpath

 }

 func (s *snapshotter) Usage(ctx context.Context, key string) (snapshots.Usage, error) {

-	return snapshots.Usage{}, nil

+	usage := snapshots.Usage{}

+	if l, err := s.getLayer(key); err != nil {

+		return usage, err

+	} else if l != nil {

+		s, err := l.DiffSize()

+		if err != nil {

+			return usage, err

+		}

+		usage.Size = s

+		return usage, nil

+	}

+

+	size := int64(-1)

+	if err := s.db.View(func(tx *bolt.Tx) error {

+		b := tx.Bucket([]byte(key))

+		if b == nil {

+			return nil

+		}

+		v := b.Get(keySize)

+		if v != nil {

+			s, err := strconv.Atoi(string(v))

+			if err != nil {

+				return err

+			}

+			size = int64(s)

+		}

+		return nil

+	}); err != nil {

+		return usage, err

+	}

+

+	if size != -1 {

+		usage.Size = size

+		return usage, nil

+	}

+

+	id, _ := s.getGraphDriverID(key)

+

+	info, err := s.Stat(ctx, key)

+	if err != nil {

+		return usage, err

+	}

+	var parent string

+	if info.Parent != "" {

+		parent, _ = s.getGraphDriverID(info.Parent)

+	}

+

+	diffSize, err := s.opt.GraphDriver.DiffSize(id, parent)

+	if err != nil {

+		return usage, err

+	}

+

+	if err := s.db.Update(func(tx *bolt.Tx) error {

+		b, err := tx.CreateBucketIfNotExists([]byte(key))

+		if err != nil {

+			return err

+		}

+		return b.Put(keySize, []byte(strconv.Itoa(int(diffSize))))

+	}); err != nil {

+		return usage, err

+	}

+	usage.Size = int64(diffSize)

+	return usage, nil

 }

 func (s *snapshotter) Close() error {