YARN-2768. Avoid cloning Resource in FSAppAttempt#updateDemand. (Hong Zhiguo via kasha)

(cherry picked from commit 5205a330b387d2e133ee790b9fe7d5af3cd8bccc)

hadoop-yarn-project/CHANGES.txt

@@ -326,6 +326,9 @@ Release 2.8.0 - UNRELEASED
     YARN-3259. FairScheduler: Trigger fairShare updates on node events. 
     (Anubhav Dhoot via kasha)
 
+    YARN-2768. Avoid cloning Resource in FSAppAttempt#updateDemand.
+    (Hong Zhiguo via kasha)
+
   BUG FIXES
 
     YARN-3197. Confusing log generated by CapacityScheduler. (Varun Saxena 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/resource/Resources.java

@@ -150,7 +150,19 @@ public class Resources {
   public static Resource multiply(Resource lhs, double by) {
     return multiplyTo(clone(lhs), by);
   }
-  
+
+  /**
+   * Multiply @param rhs by @param by, and add the result to @param lhs
+   * without creating any new {@link Resource} object
+   */
+  public static Resource multiplyAndAddTo(
+      Resource lhs, Resource rhs, double by) {
+    lhs.setMemory(lhs.getMemory() + (int)(rhs.getMemory() * by));
+    lhs.setVirtualCores(lhs.getVirtualCores()
+        + (int)(rhs.getVirtualCores() * by));
+    return lhs;
+  }
+
   public static Resource multiplyAndNormalizeUp(
       ResourceCalculator calculator,Resource lhs, double by, Resource factor) {
     return calculator.multiplyAndNormalizeUp(lhs, by, factor);

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FSAppAttempt.java

@@ -801,8 +801,8 @@ public class FSAppAttempt extends SchedulerApplicationAttempt
     synchronized (this) {
       for (Priority p : getPriorities()) {
         for (ResourceRequest r : getResourceRequests(p).values()) {
-          Resource total = Resources.multiply(r.getCapability(), r.getNumContainers());
-          Resources.addTo(demand, total);
+          Resources.multiplyAndAddTo(demand,
+              r.getCapability(), r.getNumContainers());
         }
       }
     }