diff --git a/linux/runtime.go b/linux/runtime.go
index 4e45cbbe9..4b4267152 100644
--- a/linux/runtime.go
+++ b/linux/runtime.go
@@ -5,12 +5,14 @@ package linux
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/containerd/containerd/api/services/shim"
@@ -25,6 +27,11 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+var (
+	ErrTaskNotExists     = errors.New("task does not exist")
+	ErrTaskAlreadyExists = errors.New("task already exists")
+)
+
 const (
 	runtimeName    = "linux"
 	configFilename = "config.json"
@@ -54,6 +61,71 @@ type Config struct {
 	NoShim bool `toml:"no_shim,omitempty"`
 }
 
+func newTaskList() *taskList {
+	return &taskList{
+		tasks: make(map[string]map[string]*Task),
+	}
+}
+
+type taskList struct {
+	mu    sync.Mutex
+	tasks map[string]map[string]*Task
+}
+
+func (l *taskList) get(ctx context.Context, id string) (*Task, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	namespace, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return nil, err
+	}
+	tasks, ok := l.tasks[namespace]
+	if !ok {
+		return nil, ErrTaskNotExists
+	}
+	t, ok := tasks[id]
+	if !ok {
+		return nil, ErrTaskNotExists
+	}
+	return t, nil
+}
+
+func (l *taskList) add(ctx context.Context, t *Task) error {
+	namespace, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return err
+	}
+	return l.addWithNamespace(namespace, t)
+}
+
+func (l *taskList) addWithNamespace(namespace string, t *Task) error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	id := t.containerID
+	if _, ok := l.tasks[namespace]; !ok {
+		l.tasks[namespace] = make(map[string]*Task)
+	}
+	if _, ok := l.tasks[namespace][id]; ok {
+		return ErrTaskAlreadyExists
+	}
+	l.tasks[namespace][id] = t
+	return nil
+}
+
+func (l *taskList) delete(ctx context.Context, t *Task) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	namespace, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return
+	}
+	tasks, ok := l.tasks[namespace]
+	if ok {
+		delete(tasks, t.containerID)
+	}
+}
+
 func New(ic *plugin.InitContext) (interface{}, error) {
 	path := filepath.Join(ic.State, runtimeName)
 	if err := os.MkdirAll(path, 0700); err != nil {
@@ -70,9 +142,20 @@ func New(ic *plugin.InitContext) (interface{}, error) {
 		eventsContext: c,
 		eventsCancel:  cancel,
 		monitor:       ic.Monitor,
+		tasks:         newTaskList(),
 	}
 	// set the events output for a monitor if it generates events
 	ic.Monitor.Events(r.events)
+	tasks, err := r.loadAllTasks(ic.Context)
+	if err != nil {
+		return nil, err
+	}
+	for _, t := range tasks {
+		if err := r.tasks.addWithNamespace(t.namespace, t); err != nil {
+			return nil, err
+		}
+	}
+	// load all tasks from disk
 	return r, nil
 }
 
@@ -86,6 +169,7 @@ type Runtime struct {
 	eventsContext context.Context
 	eventsCancel  func()
 	monitor       plugin.TaskMonitor
+	tasks         *taskList
 }
 
 func (r *Runtime) Create(ctx context.Context, id string, opts plugin.CreateOpts) (t plugin.Task, err error) {
@@ -134,6 +218,9 @@ func (r *Runtime) Create(ctx context.Context, id string, opts plugin.CreateOpts)
 		return nil, err
 	}
 	c := newTask(id, namespace, opts.Spec, s)
+	if err := r.tasks.add(ctx, c); err != nil {
+		return nil, err
+	}
 	// after the task is created, add it to the monitor
 	if err = r.monitor.Monitor(c); err != nil {
 		return nil, err
@@ -160,6 +247,7 @@ func (r *Runtime) Delete(ctx context.Context, c plugin.Task) (*plugin.Exit, erro
 		return nil, err
 	}
 	lc.shim.Exit(ctx, &shim.ExitRequest{})
+	r.tasks.delete(ctx, lc)
 	return &plugin.Exit{
 		Status:    rsp.ExitStatus,
 		Timestamp: rsp.ExitedAt,
@@ -167,11 +255,27 @@ func (r *Runtime) Delete(ctx context.Context, c plugin.Task) (*plugin.Exit, erro
 }
 
 func (r *Runtime) Tasks(ctx context.Context) ([]plugin.Task, error) {
-	dir, err := ioutil.ReadDir(r.root)
+	namespace, err := namespaces.NamespaceRequired(ctx)
 	if err != nil {
 		return nil, err
 	}
 	var o []plugin.Task
+	tasks, ok := r.tasks.tasks[namespace]
+	if !ok {
+		return o, nil
+	}
+	for _, t := range tasks {
+		o = append(o, t)
+	}
+	return o, nil
+}
+
+func (r *Runtime) loadAllTasks(ctx context.Context) ([]*Task, error) {
+	dir, err := ioutil.ReadDir(r.root)
+	if err != nil {
+		return nil, err
+	}
+	var o []*Task
 	for _, fi := range dir {
 		if !fi.IsDir() {
 			continue
@@ -186,19 +290,15 @@ func (r *Runtime) Tasks(ctx context.Context) ([]plugin.Task, error) {
 }
 
 func (r *Runtime) Get(ctx context.Context, id string) (plugin.Task, error) {
-	namespace, err := namespaces.NamespaceRequired(ctx)
-	if err != nil {
-		return nil, err
-	}
-	return r.loadTask(ctx, filepath.Join(r.root, namespace, id))
+	return r.tasks.get(ctx, id)
 }
 
-func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]plugin.Task, error) {
+func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]*Task, error) {
 	dir, err := ioutil.ReadDir(filepath.Join(r.root, ns))
 	if err != nil {
 		return nil, err
 	}
-	var o []plugin.Task
+	var o []*Task
 	for _, fi := range dir {
 		if !fi.IsDir() {
 			continue
@@ -206,7 +306,7 @@ func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]plugin.Task, erro
 		id := fi.Name()
 		// TODO: optimize this if it is call frequently to list all containers
 		// i.e. dont' reconnect to the the shim's ever time
-		c, err := r.loadTask(ctx, filepath.Join(r.root, ns, id))
+		c, err := r.loadTask(ns, filepath.Join(r.root, ns, id))
 		if err != nil {
 			log.G(ctx).WithError(err).Warnf("failed to load container %s/%s", ns, id)
 			// if we fail to load the container, connect to the shim, make sure if the shim has
@@ -291,11 +391,7 @@ func (r *Runtime) deleteBundle(namespace, id string) error {
 	return os.RemoveAll(filepath.Join(r.root, namespace, id))
 }
 
-func (r *Runtime) loadTask(ctx context.Context, path string) (*Task, error) {
-	namespace, err := namespaces.NamespaceRequired(ctx)
-	if err != nil {
-		return nil, err
-	}
+func (r *Runtime) loadTask(namespace, path string) (*Task, error) {
 	id := filepath.Base(path)
 	s, err := loadShim(path, namespace, r.remote)
 	if err != nil {
diff --git a/metrics/cgroups/cgroups.go b/metrics/cgroups/cgroups.go
index 6752a0f24..6d1750205 100644
--- a/metrics/cgroups/cgroups.go
+++ b/metrics/cgroups/cgroups.go
@@ -47,7 +47,7 @@ type cgroupsMonitor struct {
 }
 
 func getID(t plugin.Task) string {
-	return fmt.Sprintf("%s-%s", t.Info().ID, t.Info().Namespace)
+	return fmt.Sprintf("%s-%s", t.Info().Namespace, t.Info().ID)
 }
 
 func (m *cgroupsMonitor) Monitor(c plugin.Task) error {
diff --git a/windows/runtime.go b/windows/runtime.go
index 4b148ad5f..3c912f992 100644
--- a/windows/runtime.go
+++ b/windows/runtime.go
@@ -159,7 +159,7 @@ func (r *Runtime) Get(ctx context.Context, id string) (plugin.Task, error) {
 	defer r.Unlock()
 	c, ok := r.containers[id]
 	if !ok {
-		return fmt.Errorf("container %s does not exit", id)
+		return nil, fmt.Errorf("container %s does not exit", id)
 	}
 	return c, nil
 }