[GitHub] [helix] jiajunwang commented on a change in pull request #586: Improve the WAGED rebalancer performance.

[GitBox <gi...@apache.org>]

jiajunwang commented on a change in pull request #586: Improve the WAGED rebalancer performance.
URL: https://github.com/apache/helix/pull/586#discussion_r345509783
 
 

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 File path: helix-core/src/main/java/org/apache/helix/controller/rebalancer/waged/WagedRebalancer.java
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 @@ -296,27 +332,21 @@ public void close() {
       Set<String> activeNodes, final CurrentStateOutput currentStateOutput)
       throws HelixRebalanceException {
     getChangeDetector().updateSnapshots(clusterData);
-    // Get all the changed items' information
-    Map<HelixConstants.ChangeType, Set<String>> clusterChanges =
+    // Get all the changed items' information. Filter for the items that have content changed.
+    final Map<HelixConstants.ChangeType, Set<String>> clusterChanges =
 
 Review comment:
   As Yi pointed out, parallelStream is costly. So I tested multiple places. The conclusion is that only high-level parallelism is worthwhile. Doing it too much slow things down.
   
   For this one, the change types are not a long list. So the gain won't beat the thread managing overhead.

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