From ab93bf5b00fa090d7a78ccc13f0d1529439f0b83 Mon Sep 17 00:00:00 2001
From: Daniel Templeton <templedf@apache.org>
Date: Sat, 28 Oct 2017 09:13:13 -0700
Subject: [PATCH] YARN-7397. Reduce lock contention in
 FairScheduler#getAppWeight()

(cherry picked from commit e62bbbca7adafa0e050212e99c41c95a844700ff)
---
 .../scheduler/fair/FairScheduler.java             | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

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 04418598bf8..8ea07ab8b1e 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
@@ -369,17 +369,20 @@ public class FairScheduler extends
   }
 
   public float getAppWeight(FSAppAttempt app) {
-    try {
+    double weight = 1.0;
+
+    if (sizeBasedWeight) {
       readLock.lock();
-      double weight = 1.0;
-      if (sizeBasedWeight) {
+
+      try {
         // Set weight based on current memory demand
         weight = Math.log1p(app.getDemand().getMemorySize()) / Math.log(2);
+      } finally {
+        readLock.unlock();
       }
-      return (float)weight * app.getPriority().getPriority();
-    } finally {
-      readLock.unlock();
     }
+
+    return (float)weight * app.getPriority().getPriority();
   }
 
   public Resource getIncrementResourceCapability() {