添加Capacity调度器的源码注释

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

@@ -232,6 +232,12 @@ public static Resource clone(Resource res) {
     return Resource.newInstance(res);
   }
 
+  /**
+   * lhs = lhs + ths
+   * @param lhs
+   * @param rhs
+   * @return
+   */
   public static Resource addTo(Resource lhs, Resource rhs) {
     int maxLength = ResourceUtils.getNumberOfCountableResourceTypes();
     for (int i = 0; i < maxLength; i++) {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/ParentQueue.java

@@ -755,6 +755,15 @@ private boolean canAssign(Resource clusterResource, FiCaSchedulerNode node) {
     return accept;
   }
 
+  /**
+   * 获取子队列的队列限制,计算公式:
+   *   <p>子队列的限制 = min(父队列的可用资源 + 子队列的已使用资源, 子队列的限制)<p/>
+   * @param child
+   * @param clusterResource
+   * @param parentLimits
+   * @param nodePartition
+   * @return
+   */
   private ResourceLimits getResourceLimitsOfChild(CSQueue child,
       Resource clusterResource, Resource parentLimits,
       String nodePartition) {