diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java
index f8c99f4857d..aa34fcfaa22 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/MRAppMaster.java
@@ -245,7 +245,7 @@ public class MRAppMaster extends CompositeService {
       ContainerId containerId, String nmHost, int nmPort, int nmHttpPort,
       long appSubmitTime) {
     this(applicationAttemptId, containerId, nmHost, nmPort, nmHttpPort,
-        new SystemClock(), appSubmitTime);
+        SystemClock.getInstance(), appSubmitTime);
   }
 
   public MRAppMaster(ApplicationAttemptId applicationAttemptId,
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/TaskAttemptFinishingMonitor.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/TaskAttemptFinishingMonitor.java
index f6033988a4b..8b3073bad57 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/TaskAttemptFinishingMonitor.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/main/java/org/apache/hadoop/mapreduce/v2/app/TaskAttemptFinishingMonitor.java
@@ -38,7 +38,7 @@ public class TaskAttemptFinishingMonitor extends
   private EventHandler eventHandler;
 
   public TaskAttemptFinishingMonitor(EventHandler eventHandler) {
-    super("TaskAttemptFinishingMonitor", new SystemClock());
+    super("TaskAttemptFinishingMonitor", SystemClock.getInstance());
     this.eventHandler = eventHandler;
   }
 
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptFinishingMonitor.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptFinishingMonitor.java
index 800f0e2f5ee..521c2f43acd 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptFinishingMonitor.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptFinishingMonitor.java
@@ -47,7 +47,7 @@ public class TestTaskAttemptFinishingMonitor {
   @Test
   public void testFinshingAttemptTimeout()
       throws IOException, InterruptedException {
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
     Configuration conf = new Configuration();
     conf.setInt(MRJobConfig.TASK_EXIT_TIMEOUT, 100);
     conf.setInt(MRJobConfig.TASK_EXIT_TIMEOUT_CHECK_INTERVAL_MS, 10);
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptListenerImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptListenerImpl.java
index 2c81cf06d2d..8547be4f358 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptListenerImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapred/TestTaskAttemptListenerImpl.java
@@ -258,7 +258,7 @@ public class TestTaskAttemptListenerImpl {
 
   @Test (timeout=10000)
   public void testCommitWindow() throws IOException {
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
 
     org.apache.hadoop.mapreduce.v2.app.job.Task mockTask =
         mock(org.apache.hadoop.mapreduce.v2.app.job.Task.class);
@@ -309,7 +309,7 @@ public class TestTaskAttemptListenerImpl {
   public void testCheckpointIDTracking()
     throws IOException, InterruptedException{
 
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
 
     org.apache.hadoop.mapreduce.v2.app.job.Task mockTask =
         mock(org.apache.hadoop.mapreduce.v2.app.job.Task.class);
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/MRApp.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/MRApp.java
index f0c10d3ed3a..fd0e8e2b9b6 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/MRApp.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/MRApp.java
@@ -153,7 +153,7 @@ public class MRApp extends MRAppMaster {
   public MRApp(int maps, int reduces, boolean autoComplete, String testName,
       boolean cleanOnStart, String assignedQueue) {
     this(maps, reduces, autoComplete, testName, cleanOnStart, 1,
-        new SystemClock(), assignedQueue);
+        SystemClock.getInstance(), assignedQueue);
   }
 
   public MRApp(int maps, int reduces, boolean autoComplete, String testName,
@@ -187,13 +187,13 @@ public class MRApp extends MRAppMaster {
   public MRApp(int maps, int reduces, boolean autoComplete, String testName,
       boolean cleanOnStart, int startCount) {
     this(maps, reduces, autoComplete, testName, cleanOnStart, startCount,
-        new SystemClock(), null);
+        SystemClock.getInstance(), null);
   }
 
   public MRApp(int maps, int reduces, boolean autoComplete, String testName,
       boolean cleanOnStart, int startCount, boolean unregistered) {
     this(maps, reduces, autoComplete, testName, cleanOnStart, startCount,
-        new SystemClock(), unregistered);
+        SystemClock.getInstance(), unregistered);
   }
 
   public MRApp(int maps, int reduces, boolean autoComplete, String testName,
@@ -214,14 +214,14 @@ public class MRApp extends MRAppMaster {
       int maps, int reduces, boolean autoComplete, String testName,
       boolean cleanOnStart, int startCount, boolean unregistered) {
     this(appAttemptId, amContainerId, maps, reduces, autoComplete, testName,
-        cleanOnStart, startCount, new SystemClock(), unregistered, null);
+        cleanOnStart, startCount, SystemClock.getInstance(), unregistered, null);
   }
 
   public MRApp(ApplicationAttemptId appAttemptId, ContainerId amContainerId,
       int maps, int reduces, boolean autoComplete, String testName,
       boolean cleanOnStart, int startCount) {
     this(appAttemptId, amContainerId, maps, reduces, autoComplete, testName,
-        cleanOnStart, startCount, new SystemClock(), true, null);
+        cleanOnStart, startCount, SystemClock.getInstance(), true, null);
   }
 
   public MRApp(ApplicationAttemptId appAttemptId, ContainerId amContainerId,
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRecovery.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRecovery.java
index 0e07bcf969e..504a5f7c71d 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRecovery.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRecovery.java
@@ -1785,7 +1785,7 @@ public class TestRecovery {
     Token<JobTokenIdentifier> jobToken =
         (Token<JobTokenIdentifier>) mock(Token.class);
     Credentials credentials = null;
-    Clock clock = new SystemClock();
+    Clock clock = SystemClock.getInstance();
     int appAttemptId = 3;
     MRAppMetrics metrics = mock(MRAppMetrics.class);
     Resource minContainerRequirements = mock(Resource.class);
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRuntimeEstimators.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRuntimeEstimators.java
index 0b7d1b18aa8..7f9a3b95391 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRuntimeEstimators.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestRuntimeEstimators.java
@@ -788,7 +788,7 @@ public class TestRuntimeEstimators {
       public MyAppMaster(Clock clock) {
         super(MyAppMaster.class.getName());
         if (clock == null) {
-          clock = new SystemClock();
+          clock = SystemClock.getInstance();
         }
       this.clock = clock;
       LOG.info("Created MyAppMaster");
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestTaskHeartbeatHandler.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestTaskHeartbeatHandler.java
index 62e96cb5afd..e9a09895ec0 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestTaskHeartbeatHandler.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/TestTaskHeartbeatHandler.java
@@ -44,7 +44,7 @@ public class TestTaskHeartbeatHandler {
   @Test
   public void testTimeout() throws InterruptedException {
     EventHandler mockHandler = mock(EventHandler.class);
-    Clock clock = new SystemClock();
+    Clock clock = SystemClock.getInstance();
     TaskHeartbeatHandler hb = new TaskHeartbeatHandler(mockHandler, clock, 1);
     
     
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/commit/TestCommitterEventHandler.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/commit/TestCommitterEventHandler.java
index a553bbdab2d..a4853d5e428 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/commit/TestCommitterEventHandler.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/commit/TestCommitterEventHandler.java
@@ -127,7 +127,7 @@ public class TestCommitterEventHandler {
     TestingJobEventHandler jeh = new TestingJobEventHandler();
     dispatcher.register(JobEventType.class, jeh);
 
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
     AppContext appContext = mock(AppContext.class);
     ApplicationAttemptId attemptid = 
       ConverterUtils.toApplicationAttemptId("appattempt_1234567890000_0001_0");
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java
index 33c5c48ecfe..fa0aef3bc86 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestJobImpl.java
@@ -723,7 +723,7 @@ public class TestJobImpl {
         .newRecord(ApplicationAttemptId.class), new Configuration(),
         mock(EventHandler.class),
         null, mock(JobTokenSecretManager.class), null,
-        new SystemClock(), null,
+        SystemClock.getInstance(), null,
         mrAppMetrics, null, true, null, 0, null, mockContext, null, null);
     job.handle(diagUpdateEvent);
     String diagnostics = job.getReport().getDiagnostics();
@@ -734,7 +734,7 @@ public class TestJobImpl {
         .newRecord(ApplicationAttemptId.class), new Configuration(),
         mock(EventHandler.class),
         null, mock(JobTokenSecretManager.class), null,
-        new SystemClock(), null,
+        SystemClock.getInstance(), null,
         mrAppMetrics, null, true, null, 0, null, mockContext, null, null);
     job.handle(new JobEvent(jobId, JobEventType.JOB_KILL));
     job.handle(diagUpdateEvent);
@@ -926,7 +926,7 @@ public class TestJobImpl {
 
   private static CommitterEventHandler createCommitterEventHandler(
       Dispatcher dispatcher, OutputCommitter committer) {
-    final SystemClock clock = new SystemClock();
+    final SystemClock clock = SystemClock.getInstance();
     AppContext appContext = mock(AppContext.class);
     when(appContext.getEventHandler()).thenReturn(
         dispatcher.getEventHandler());
@@ -1105,7 +1105,7 @@ public class TestJobImpl {
         String user, int numSplits, AppContext appContext) {
       super(jobId, applicationAttemptId, conf, eventHandler,
           null, new JobTokenSecretManager(), new Credentials(),
-          new SystemClock(), Collections.<TaskId, TaskInfo> emptyMap(),
+          SystemClock.getInstance(), Collections.<TaskId, TaskInfo> emptyMap(),
           MRAppMetrics.create(), null, newApiCommitter, user,
           System.currentTimeMillis(), null, appContext, null, null);
 
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestShuffleProvider.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestShuffleProvider.java
index cb936c285c5..eda16a4f1d6 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestShuffleProvider.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestShuffleProvider.java
@@ -99,7 +99,7 @@ public class TestShuffleProvider {
         new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
             mock(TaskSplitMetaInfo.class), jobConf, taListener,
             jobToken, credentials,
-            new SystemClock(), null);
+            SystemClock.getInstance(), null);
 
     jobConf.set(MRJobConfig.APPLICATION_ATTEMPT_ID, taImpl.getID().toString());
 
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttempt.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttempt.java
index 1ed8098988a..5a660617661 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttempt.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttempt.java
@@ -257,7 +257,7 @@ public class TestTaskAttempt{
 
   public void verifyMillisCounters(int mapMemMb, int reduceMemMb,
       int minContainerSize) throws Exception {
-    Clock actualClock = new SystemClock();
+    Clock actualClock = SystemClock.getInstance();
     ControlledClock clock = new ControlledClock(actualClock);
     clock.setTime(10);
     MRApp app =
@@ -320,7 +320,7 @@ public class TestTaskAttempt{
 
   private TaskAttemptImpl createMapTaskAttemptImplForTest(
       EventHandler eventHandler, TaskSplitMetaInfo taskSplitMetaInfo) {
-    Clock clock = new SystemClock();
+    Clock clock = SystemClock.getInstance();
     return createMapTaskAttemptImplForTest(eventHandler, taskSplitMetaInfo, clock);
   }
 
@@ -512,7 +512,7 @@ public class TestTaskAttempt{
       new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
           splits, jobConf, taListener,
           new Token(), new Credentials(),
-          new SystemClock(), null);
+          SystemClock.getInstance(), null);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -569,7 +569,7 @@ public class TestTaskAttempt{
       new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
           splits, jobConf, taListener,
           new Token(), new Credentials(),
-          new SystemClock(), appCtx);
+          SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.2", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -627,7 +627,7 @@ public class TestTaskAttempt{
       new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
           splits, jobConf, taListener,
           new Token(), new Credentials(),
-          new SystemClock(), appCtx);
+          SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -691,7 +691,7 @@ public class TestTaskAttempt{
       new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
           splits, jobConf, taListener,
           new Token(), new Credentials(),
-          new SystemClock(), appCtx);
+          SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -759,7 +759,7 @@ public class TestTaskAttempt{
 
     TaskAttemptImpl taImpl = new MapTaskAttemptImpl(taskId, 1, eventHandler,
         jobFile, 1, splits, jobConf, taListener,
-        new Token(), new Credentials(), new SystemClock(), appCtx);
+        new Token(), new Credentials(), SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -818,7 +818,7 @@ public class TestTaskAttempt{
       new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
         splits, jobConf, taListener,
         mock(Token.class), new Credentials(),
-        new SystemClock(), appCtx);
+        SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -884,7 +884,7 @@ public class TestTaskAttempt{
 
     TaskAttemptImpl taImpl = new MapTaskAttemptImpl(taskId, 1, eventHandler,
         jobFile, 1, splits, jobConf, taListener,
-        new Token(), new Credentials(), new SystemClock(), appCtx);
+        new Token(), new Credentials(), SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -934,7 +934,7 @@ public class TestTaskAttempt{
     TaskAttemptImpl taImpl =
       new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
       splits, jobConf, taListener,mock(Token.class), new Credentials(),
-      new SystemClock(), appCtx);
+      SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -1004,7 +1004,7 @@ public class TestTaskAttempt{
 
     TaskAttemptImpl taImpl = new MapTaskAttemptImpl(taskId, 1, eventHandler,
         jobFile, 1, splits, jobConf, taListener, new Token(),
-        new Credentials(), new SystemClock(), appCtx);
+        new Credentials(), SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.2", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -1058,7 +1058,7 @@ public class TestTaskAttempt{
 
     TaskAttemptImpl taImpl = new MapTaskAttemptImpl(taskId, 1, eventHandler,
         jobFile, 1, splits, jobConf, taListener, new Token(),
-        new Credentials(), new SystemClock(), appCtx);
+        new Credentials(), SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.2", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -1115,7 +1115,7 @@ public class TestTaskAttempt{
 
     TaskAttemptImpl taImpl = new MapTaskAttemptImpl(taskId, 1, eventHandler,
         jobFile, 1, splits, jobConf, taListener, new Token(),
-        new Credentials(), new SystemClock(), appCtx);
+        new Credentials(), SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.2", 0);
     ContainerId contId = ContainerId.newContainerId(appAttemptId, 3);
@@ -1376,7 +1376,7 @@ public class TestTaskAttempt{
         new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
             splits, jobConf, taListener,
             mock(Token.class), new Credentials(),
-            new SystemClock(), appCtx);
+            SystemClock.getInstance(), appCtx);
 
     NodeId nid = NodeId.newInstance("127.0.0.1", 0);
     ContainerId contId = ContainerId.newInstance(appAttemptId, 3);
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttemptContainerRequest.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttemptContainerRequest.java
index 68294af0b9d..b151c8afb08 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttemptContainerRequest.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskAttemptContainerRequest.java
@@ -104,7 +104,7 @@ public class TestTaskAttemptContainerRequest {
         new MapTaskAttemptImpl(taskId, 1, eventHandler, jobFile, 1,
             mock(TaskSplitMetaInfo.class), jobConf, taListener,
             jobToken, credentials,
-            new SystemClock(), null);
+            SystemClock.getInstance(), null);
 
     jobConf.set(MRJobConfig.APPLICATION_ATTEMPT_ID, taImpl.getID().toString());
 
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java
index af5181742ed..84576712b44 100755
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/job/impl/TestTaskImpl.java
@@ -243,7 +243,7 @@ public class TestTaskImpl {
     jobToken = (Token<JobTokenIdentifier>) mock(Token.class);
     remoteJobConfFile = mock(Path.class);
     credentials = null;
-    clock = new SystemClock();
+    clock = SystemClock.getInstance();
     metrics = mock(MRAppMetrics.class);  
     dataLocations = new String[1];
     
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/rm/TestRMContainerAllocator.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/rm/TestRMContainerAllocator.java
index 0a1043419d3..a2aaa9d704b 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/rm/TestRMContainerAllocator.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-app/src/test/java/org/apache/hadoop/mapreduce/v2/app/rm/TestRMContainerAllocator.java
@@ -431,7 +431,7 @@ public class TestRMContainerAllocator {
         MRBuilderUtils.newJobReport(jobId, "job", "user", JobState.RUNNING, 0,
             0, 0, 0, 0, 0, 0, "jobfile", null, false, ""));
     final MyContainerAllocator allocator = new MyContainerAllocator(rm, conf,
-        appAttemptId, mockJob, new SystemClock());
+        appAttemptId, mockJob, SystemClock.getInstance());
     // add resources to scheduler
     dispatcher.await();
 
@@ -485,7 +485,7 @@ public class TestRMContainerAllocator {
         MRBuilderUtils.newJobReport(jobId, "job", "user", JobState.RUNNING, 0,
             0, 0, 0, 0, 0, 0, "jobfile", null, false, ""));
     MyContainerAllocator allocator = new MyContainerAllocator(rm, conf,
-        appAttemptId, mockJob, new SystemClock());
+        appAttemptId, mockJob, SystemClock.getInstance());
     allocator.setMapResourceRequest(BuilderUtils.newResource(1024, 1));
     allocator.setReduceResourceRequest(BuilderUtils.newResource(1024, 1));
     RMContainerAllocator.AssignedRequests assignedRequests =
@@ -653,7 +653,7 @@ public class TestRMContainerAllocator {
         MRBuilderUtils.newJobReport(jobId, "job", "user", JobState.RUNNING, 0,
             0, 0, 0, 0, 0, 0, "jobfile", null, false, ""));
     final MyContainerAllocator allocator = new MyContainerAllocator(rm, conf,
-        appAttemptId, mockJob, new SystemClock());
+        appAttemptId, mockJob, SystemClock.getInstance());
 
     // request to allocate two reduce priority containers
     final String[] locations = new String[] { host };
@@ -698,7 +698,7 @@ public class TestRMContainerAllocator {
     final MockScheduler mockScheduler = new MockScheduler(appAttemptId);
     MyContainerAllocator allocator =
         new MyContainerAllocator(null, conf, appAttemptId, mockJob,
-            new SystemClock()) {
+            SystemClock.getInstance()) {
           @Override
           protected void register() {
           }
@@ -790,7 +790,7 @@ public class TestRMContainerAllocator {
         MRBuilderUtils.newJobReport(jobId, "job", "user", JobState.RUNNING, 0,
             0, 0, 0, 0, 0, 0, "jobfile", null, false, ""));
     MyContainerAllocator allocator = new MyContainerAllocator(rm, conf,
-        appAttemptId, mockJob, new SystemClock());
+        appAttemptId, mockJob, SystemClock.getInstance());
 
     // add resources to scheduler
     MockNM nodeManager1 = rm.registerNode("h1:1234", 1024);
@@ -2265,7 +2265,7 @@ public class TestRMContainerAllocator {
 
     Configuration conf = new Configuration();
     conf.setInt(MRJobConfig.MR_AM_TO_RM_HEARTBEAT_INTERVAL_MS, 1);
-    ControlledClock clock = new ControlledClock(new SystemClock());
+    ControlledClock clock = new ControlledClock();
     AppContext appContext = mock(AppContext.class);
     when(appContext.getClock()).thenReturn(clock);
     when(appContext.getApplicationID()).thenReturn(
@@ -2751,7 +2751,7 @@ public class TestRMContainerAllocator {
             0, 0, 0, 0, 0, 0, "jobfile", null, false, ""));
     final MockScheduler mockScheduler = new MockScheduler(appAttemptId);
     MyContainerAllocator allocator = new MyContainerAllocator(null, conf,
-        appAttemptId, mockJob, new SystemClock()) {
+        appAttemptId, mockJob, SystemClock.getInstance()) {
           @Override
           protected void register() {
           }
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/HistoryFileManager.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/HistoryFileManager.java
index a21045b7462..6be0d274534 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/HistoryFileManager.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/HistoryFileManager.java
@@ -536,7 +536,7 @@ public class HistoryFileManager extends AbstractService {
     long maxFSWaitTime = conf.getLong(
         JHAdminConfig.MR_HISTORY_MAX_START_WAIT_TIME,
         JHAdminConfig.DEFAULT_MR_HISTORY_MAX_START_WAIT_TIME);
-    createHistoryDirs(new SystemClock(), 10 * 1000, maxFSWaitTime);
+    createHistoryDirs(SystemClock.getInstance(), 10 * 1000, maxFSWaitTime);
 
     this.aclsMgr = new JobACLsManager(conf);
 
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/test/java/org/apache/hadoop/mapreduce/v2/hs/TestHistoryFileManager.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/test/java/org/apache/hadoop/mapreduce/v2/hs/TestHistoryFileManager.java
index 7694de93e08..18e3e6a38ac 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/test/java/org/apache/hadoop/mapreduce/v2/hs/TestHistoryFileManager.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/test/java/org/apache/hadoop/mapreduce/v2/hs/TestHistoryFileManager.java
@@ -185,7 +185,8 @@ public class TestHistoryFileManager {
         }
       }
     }.start();
-    testCreateHistoryDirs(dfsCluster.getConfiguration(0), new SystemClock());
+    testCreateHistoryDirs(dfsCluster.getConfiguration(0),
+        SystemClock.getInstance());
   }
 
   @Test(expected = YarnRuntimeException.class)
@@ -194,7 +195,7 @@ public class TestHistoryFileManager {
     dfsCluster.getFileSystem().setSafeMode(
         HdfsConstants.SafeModeAction.SAFEMODE_ENTER);
     Assert.assertTrue(dfsCluster.getFileSystem().isInSafeMode());
-    final ControlledClock clock = new ControlledClock(new SystemClock());
+    final ControlledClock clock = new ControlledClock();
     clock.setTime(1);
     new Thread() {
       @Override
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/v2/TestSpeculativeExecutionWithMRApp.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/v2/TestSpeculativeExecutionWithMRApp.java
index 5ce27612ba7..e8003c0be73 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/v2/TestSpeculativeExecutionWithMRApp.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-jobclient/src/test/java/org/apache/hadoop/mapreduce/v2/TestSpeculativeExecutionWithMRApp.java
@@ -57,7 +57,7 @@ public class TestSpeculativeExecutionWithMRApp {
   @Test
   public void testSpeculateSuccessfulWithoutUpdateEvents() throws Exception {
 
-    Clock actualClock = new SystemClock();
+    Clock actualClock = SystemClock.getInstance();
     final ControlledClock clock = new ControlledClock(actualClock);
     clock.setTime(System.currentTimeMillis());
 
@@ -128,7 +128,7 @@ public class TestSpeculativeExecutionWithMRApp {
   @Test
   public void testSepculateSuccessfulWithUpdateEvents() throws Exception {
 
-    Clock actualClock = new SystemClock();
+    Clock actualClock = SystemClock.getInstance();
     final ControlledClock clock = new ControlledClock(actualClock);
     clock.setTime(System.currentTimeMillis());
 
diff --git a/hadoop-yarn-project/CHANGES.txt b/hadoop-yarn-project/CHANGES.txt
index d6fa271d0fa..7b88e4e2679 100644
--- a/hadoop-yarn-project/CHANGES.txt
+++ b/hadoop-yarn-project/CHANGES.txt
@@ -95,6 +95,9 @@ Release 2.9.0 - UNRELEASED
     YARN-4553. Add cgroups support for docker containers.
     (Sidharta Seethana via vvasudev)
 
+    YARN-4526. Make SystemClock singleton so AppSchedulingInfo could use it. 
+    (kasha)
+
   OPTIMIZATIONS
 
   BUG FIXES
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/ProcfsBasedProcessTree.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/ProcfsBasedProcessTree.java
index 2345c6273ad..c0c935667fc 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/ProcfsBasedProcessTree.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/ProcfsBasedProcessTree.java
@@ -122,7 +122,7 @@ public class ProcfsBasedProcessTree extends ResourceCalculatorProcessTree {
     new HashMap<String, ProcessInfo>();
 
   public ProcfsBasedProcessTree(String pid) {
-    this(pid, PROCFS, new SystemClock());
+    this(pid, PROCFS, SystemClock.getInstance());
   }
 
   @Override
@@ -136,7 +136,7 @@ public class ProcfsBasedProcessTree extends ResourceCalculatorProcessTree {
   }
 
   public ProcfsBasedProcessTree(String pid, String procfsDir) {
-    this(pid, procfsDir, new SystemClock());
+    this(pid, procfsDir, SystemClock.getInstance());
   }
 
   /**
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/SystemClock.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/SystemClock.java
index ad377272e6f..c60368f1fde 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/SystemClock.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/SystemClock.java
@@ -30,7 +30,17 @@ import org.apache.hadoop.classification.InterfaceStability.Stable;
  */
 @Public
 @Stable
-public class SystemClock implements Clock {
+public final class SystemClock implements Clock {
+
+  private static final SystemClock INSTANCE = new SystemClock();
+
+  public static SystemClock getInstance() {
+    return INSTANCE;
+  }
+
+  private SystemClock() {
+    // do nothing
+  }
 
   public long getTime() {
     return System.currentTimeMillis();
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/WindowsBasedProcessTree.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/WindowsBasedProcessTree.java
index 30add01304c..7d5e7f933a1 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/WindowsBasedProcessTree.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/WindowsBasedProcessTree.java
@@ -83,7 +83,7 @@ public class WindowsBasedProcessTree extends ResourceCalculatorProcessTree {
    * @param pid Identifier of the job object.
    */
   public WindowsBasedProcessTree(final String pid) {
-    this(pid, new SystemClock());
+    this(pid, SystemClock.getInstance());
   }
 
   /**
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/ControlledClock.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/ControlledClock.java
index 6dcb1ddb806..737f36180ed 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/ControlledClock.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/ControlledClock.java
@@ -23,7 +23,7 @@ public class ControlledClock implements Clock {
   private final Clock actualClock;
   // Convenience for getting a controlled clock with overridden time
   public ControlledClock() {
-    this(new SystemClock());
+    this(SystemClock.getInstance());
     setTime(0);
   }
   public ControlledClock(Clock actualClock) {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestProcfsBasedProcessTree.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestProcfsBasedProcessTree.java
index 59cef07d28c..4a7e6fff9c9 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestProcfsBasedProcessTree.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestProcfsBasedProcessTree.java
@@ -395,7 +395,7 @@ public class TestProcfsBasedProcessTree {
 
     // test processes
     String[] pids = { "100", "200", "300", "400" };
-    ControlledClock testClock = new ControlledClock(new SystemClock());
+    ControlledClock testClock = new ControlledClock();
     testClock.setTime(0);
     // create the fake procfs root directory.
     File procfsRootDir = new File(TEST_ROOT_DIR, "proc");
@@ -575,7 +575,7 @@ public class TestProcfsBasedProcessTree {
       // crank up the process tree class.
       ProcfsBasedProcessTree processTree =
           createProcessTree("100", procfsRootDir.getAbsolutePath(),
-              new SystemClock());
+              SystemClock.getInstance());
       setSmapsInProceTree(processTree, smapEnabled);
 
       // verify virtual memory
@@ -774,7 +774,8 @@ public class TestProcfsBasedProcessTree {
       setupProcfsRootDir(procfsRootDir);
 
       // crank up the process tree class.
-      createProcessTree(pid, procfsRootDir.getAbsolutePath(), new SystemClock());
+      createProcessTree(pid, procfsRootDir.getAbsolutePath(),
+          SystemClock.getInstance());
 
       // Let us not create stat file for pid 100.
       Assert.assertTrue(ProcfsBasedProcessTree.checkPidPgrpidForMatch(pid,
@@ -844,7 +845,7 @@ public class TestProcfsBasedProcessTree {
 
       ProcfsBasedProcessTree processTree =
           createProcessTree("100", procfsRootDir.getAbsolutePath(),
-              new SystemClock());
+              SystemClock.getInstance());
       // build the process tree.
       processTree.updateProcessTree();
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestWindowsBasedProcessTree.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestWindowsBasedProcessTree.java
index c28915c8fae..290caa6938d 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestWindowsBasedProcessTree.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestWindowsBasedProcessTree.java
@@ -51,7 +51,7 @@ public class TestWindowsBasedProcessTree {
     }
     assertTrue("WindowsBasedProcessTree should be available on Windows", 
                WindowsBasedProcessTree.isAvailable());
-    ControlledClock testClock = new ControlledClock(new SystemClock());
+    ControlledClock testClock = new ControlledClock();
     long elapsedTimeBetweenUpdatesMsec = 0;
     testClock.setTime(elapsedTimeBetweenUpdatesMsec);
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/container/ContainerImpl.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/container/ContainerImpl.java
index e16ea93bcd9..3c49489fdb9 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/container/ContainerImpl.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/container/ContainerImpl.java
@@ -99,7 +99,7 @@ public class ContainerImpl implements Container {
   private boolean wasLaunched;
   private long containerLocalizationStartTime;
   private long containerLaunchStartTime;
-  private static Clock clock = new SystemClock();
+  private static Clock clock = SystemClock.getInstance();
 
   /** The NM-wide configuration - not specific to this container */
   private final Configuration daemonConf;
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsHandlerImpl.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsHandlerImpl.java
index 0d71a9da83c..1ee0f8ababd 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsHandlerImpl.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/linux/resources/CGroupsHandlerImpl.java
@@ -88,7 +88,7 @@ class CGroupsHandlerImpl implements CGroupsHandler {
     this.controllerPaths = new HashMap<>();
     this.rwLock = new ReentrantReadWriteLock();
     this.privilegedOperationExecutor = privilegedOperationExecutor;
-    this.clock = new SystemClock();
+    this.clock = SystemClock.getInstance();
 
     init();
   }
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/util/CgroupsLCEResourcesHandler.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/util/CgroupsLCEResourcesHandler.java
index 6994fc3f8c6..da39fa2b018 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/util/CgroupsLCEResourcesHandler.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/util/CgroupsLCEResourcesHandler.java
@@ -87,7 +87,7 @@ public class CgroupsLCEResourcesHandler implements LCEResourcesHandler {
 
   public CgroupsLCEResourcesHandler() {
     this.controllerPaths = new HashMap<String, String>();
-    clock = new SystemClock();
+    clock = SystemClock.getInstance();
   }
 
   @Override
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/NodesListManager.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/NodesListManager.java
index 4d9922b70d3..96307a78365 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/NodesListManager.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/NodesListManager.java
@@ -83,7 +83,8 @@ public class NodesListManager extends CompositeService implements
     if (nodeIpCacheTimeout <= 0) {
       resolver = new DirectResolver();
     } else {
-      resolver = new CachedResolver(new SystemClock(), nodeIpCacheTimeout);
+      resolver =
+          new CachedResolver(SystemClock.getInstance(), nodeIpCacheTimeout);
       addIfService(resolver);
     }
 
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/RMActiveServiceContext.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/RMActiveServiceContext.java
index dd2153ac05b..b0f4b322c0f 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/RMActiveServiceContext.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/RMActiveServiceContext.java
@@ -97,7 +97,7 @@ public class RMActiveServiceContext {
   private RMNodeLabelsManager nodeLabelManager;
   private RMDelegatedNodeLabelsUpdater rmDelegatedNodeLabelsUpdater;
   private long epoch;
-  private Clock systemClock = new SystemClock();
+  private Clock systemClock = SystemClock.getInstance();
   private long schedulerRecoveryStartTime = 0;
   private long schedulerRecoveryWaitTime = 0;
   private boolean printLog = true;
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java
index c68bb8e1337..35376e8e7c0 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/capacity/ProportionalCapacityPreemptionPolicy.java
@@ -136,12 +136,12 @@ public class ProportionalCapacityPreemptionPolicy implements SchedulingEditPolic
   private RMNodeLabelsManager nlm;
 
   public ProportionalCapacityPreemptionPolicy() {
-    clock = new SystemClock();
+    clock = SystemClock.getInstance();
   }
 
   public ProportionalCapacityPreemptionPolicy(Configuration config,
       RMContext context, CapacityScheduler scheduler) {
-    this(config, context, scheduler, new SystemClock());
+    this(config, context, scheduler, SystemClock.getInstance());
   }
 
   public ProportionalCapacityPreemptionPolicy(Configuration config,
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/RMAppImpl.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/RMAppImpl.java
index 38455620d9b..6ecc7d321ce 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/RMAppImpl.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/RMAppImpl.java
@@ -399,7 +399,7 @@ public class RMAppImpl implements RMApp, Recoverable {
       String applicationType, Set<String> applicationTags, 
       ResourceRequest amReq) {
 
-    this.systemClock = new SystemClock();
+    this.systemClock = SystemClock.getInstance();
 
     this.applicationId = applicationId;
     this.name = name;
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AllocationFileLoaderService.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AllocationFileLoaderService.java
index 9049525cd72..9a31be36242 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AllocationFileLoaderService.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/AllocationFileLoaderService.java
@@ -88,7 +88,7 @@ public class AllocationFileLoaderService extends AbstractService {
   private volatile boolean running = true;
 
   public AllocationFileLoaderService() {
-    this(new SystemClock());
+    this(SystemClock.getInstance());
   }
   
   public AllocationFileLoaderService(Clock clock) {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java
index 4df47cc8445..a36dd8c6ad2 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FairScheduler.java
@@ -215,7 +215,7 @@ public class FairScheduler extends
 
   public FairScheduler() {
     super(FairScheduler.class.getName());
-    clock = new SystemClock();
+    clock = SystemClock.getInstance();
     allocsLoader = new AllocationFileLoaderService();
     queueMgr = new QueueManager(this);
     maxRunningEnforcer = new MaxRunningAppsEnforcer(this);
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestWorkPreservingRMRestart.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestWorkPreservingRMRestart.java
index 05713877c25..f0aa4703535 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestWorkPreservingRMRestart.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/TestWorkPreservingRMRestart.java
@@ -1163,7 +1163,7 @@ public class TestWorkPreservingRMRestart extends ParameterizedSchedulerTestBase
     rm2.start();
     nm1.setResourceTrackerService(rm2.getResourceTrackerService());
     nm1.registerNode();
-    ControlledClock clock = new ControlledClock(new SystemClock());
+    ControlledClock clock = new ControlledClock();
     long startTime = System.currentTimeMillis();
     ((RMContextImpl)rm2.getRMContext()).setSystemClock(clock);
     am1.setAMRMProtocol(rm2.getApplicationMasterService(), rm2.getRMContext());
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/applicationsmanager/TestAMRestart.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/applicationsmanager/TestAMRestart.java
index 3d0c82307cb..5035afe4a11 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/applicationsmanager/TestAMRestart.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/applicationsmanager/TestAMRestart.java
@@ -820,7 +820,7 @@ public class TestAMRestart {
     // current app should be failed.
     rm1.waitForState(app.getApplicationId(), RMAppState.FAILED);
 
-    ControlledClock clock = new ControlledClock(new SystemClock());
+    ControlledClock clock = new ControlledClock();
     // set window size to 10s
     RMAppImpl app1 = (RMAppImpl)rm1.submitApp(200, 10000);;
     app1.setSystemClock(clock);
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java
index 2f57dbf9329..e747df40753 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/TestNodesListManager.java
@@ -136,7 +136,7 @@ public class TestNodesListManager {
   public void testCachedResolver() throws Exception {
     Logger rootLogger = LogManager.getRootLogger();
     rootLogger.setLevel(Level.DEBUG);
-    ControlledClock clock = new ControlledClock(new SystemClock());
+    ControlledClock clock = new ControlledClock();
     clock.setTime(0);
     final int CACHE_EXPIRY_INTERVAL_SECS = 30;
     NodesListManager.CachedResolver resolver =
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/attempt/TestAMLivelinessMonitor.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/attempt/TestAMLivelinessMonitor.java
index e0e6aee0228..14c14df0afb 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/attempt/TestAMLivelinessMonitor.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/rmapp/attempt/TestAMLivelinessMonitor.java
@@ -41,7 +41,7 @@ public class TestAMLivelinessMonitor {
     conf.set(YarnConfiguration.RM_STORE, MemoryRMStateStore.class.getName());
     conf.setBoolean(YarnConfiguration.RM_WORK_PRESERVING_RECOVERY_ENABLED, true);
     conf.setInt(YarnConfiguration.RM_AM_EXPIRY_INTERVAL_MS, 6000);
-    final ControlledClock clock = new ControlledClock(new SystemClock());
+    final ControlledClock clock = new ControlledClock();
     clock.setTime(0);
     MemoryRMStateStore memStore = new MemoryRMStateStore() {
       @Override
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestFSParentQueue.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestFSParentQueue.java
index f3e9e0cf8c3..3ae8f832150 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestFSParentQueue.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestFSParentQueue.java
@@ -42,7 +42,7 @@ public class TestFSParentQueue {
     AllocationConfiguration allocConf = new AllocationConfiguration(conf);
     when(scheduler.getAllocationConfiguration()).thenReturn(allocConf);
     when(scheduler.getConf()).thenReturn(conf);
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
     when(scheduler.getClock()).thenReturn(clock);
     notEmptyQueues = new HashSet<FSQueue>();
     queueManager = new QueueManager(scheduler) {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestQueueManager.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestQueueManager.java
index b3ed542b53d..a9b27a1a44e 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestQueueManager.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/TestQueueManager.java
@@ -41,7 +41,7 @@ public class TestQueueManager {
     AllocationConfiguration allocConf = new AllocationConfiguration(conf);
     when(scheduler.getAllocationConfiguration()).thenReturn(allocConf);
     when(scheduler.getConf()).thenReturn(conf);
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
     when(scheduler.getClock()).thenReturn(clock);
     notEmptyQueues = new HashSet<FSQueue>();
     queueManager = new QueueManager(scheduler) {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/dao/TestFairSchedulerQueueInfo.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/dao/TestFairSchedulerQueueInfo.java
index 973afcfb99f..67d73409466 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/dao/TestFairSchedulerQueueInfo.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/webapp/dao/TestFairSchedulerQueueInfo.java
@@ -43,7 +43,7 @@ public class TestFairSchedulerQueueInfo {
     when(scheduler.getAllocationConfiguration()).thenReturn(allocConf);
     when(scheduler.getConf()).thenReturn(conf);
     when(scheduler.getClusterResource()).thenReturn(Resource.newInstance(1, 1));
-    SystemClock clock = new SystemClock();
+    SystemClock clock = SystemClock.getInstance();
     when(scheduler.getClock()).thenReturn(clock);
     QueueManager queueManager = new QueueManager(scheduler);
     queueManager.initialize(conf);