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https://issues.apache.org/jira/browse/FLINK-10727?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16670149#comment-16670149
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ASF GitHub Bot commented on FLINK-10727:
----------------------------------------

NicoK closed pull request #6974: [FLINK-10727][network] remove unnecessary 
synchronization in SingleInputGate#requestPartitions()
URL: https://github.com/apache/flink/pull/6974
 
 
   

This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:

As this is a foreign pull request (from a fork), the diff is supplied
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diff --git 
a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
 
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
index f51dc7417ab..2856ca1c33a 100644
--- 
a/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
+++ 
b/flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
@@ -477,26 +477,28 @@ public boolean isFinished() {
 
        @Override
        public void requestPartitions() throws IOException, 
InterruptedException {
-               synchronized (requestLock) {
-                       if (!requestedPartitionsFlag) {
-                               if (isReleased) {
-                                       throw new 
IllegalStateException("Already released.");
-                               }
+               if (requestedPartitionsFlag) {
+                       return;
+               }
 
-                               // Sanity checks
-                               if (numberOfInputChannels != 
inputChannels.size()) {
-                                       throw new IllegalStateException("Bug in 
input gate setup logic: mismatch between" +
-                                                       "number of total input 
channels and the currently set number of input " +
-                                                       "channels.");
-                               }
+               synchronized (requestLock) {
+                       if (isReleased) {
+                               throw new IllegalStateException("Already 
released.");
+                       }
 
-                               for (InputChannel inputChannel : 
inputChannels.values()) {
-                                       
inputChannel.requestSubpartition(consumedSubpartitionIndex);
-                               }
+                       // Sanity checks
+                       if (numberOfInputChannels != inputChannels.size()) {
+                               throw new IllegalStateException("Bug in input 
gate setup logic: mismatch between" +
+                                               "number of total input channels 
and the currently set number of input " +
+                                               "channels.");
                        }
 
-                       requestedPartitionsFlag = true;
+                       for (InputChannel inputChannel : 
inputChannels.values()) {
+                               
inputChannel.requestSubpartition(consumedSubpartitionIndex);
+                       }
                }
+
+               requestedPartitionsFlag = true;
        }
 
        // 
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> Remove unnecessary synchronization in SingleInputGate#requestPartitions()
> -------------------------------------------------------------------------
>
>                 Key: FLINK-10727
>                 URL: https://issues.apache.org/jira/browse/FLINK-10727
>             Project: Flink
>          Issue Type: Improvement
>          Components: Network
>    Affects Versions: 1.5.5, 1.6.2, 1.7.0
>            Reporter: Nico Kruber
>            Assignee: Nico Kruber
>            Priority: Major
>              Labels: pull-request-available
>
> For every {{SingleInputGate#getNextBufferOrEvent()}}, 
> {{SingleInputGate#requestPartitions()}} is called and this always 
> synchronizes on the {{requestLock}} before checking the 
> {{requestedPartitionsFlag}}. Since {{SingleInputGate#requestPartitions()}} is 
> only called from the same thread (the task thread getting the record), it is 
> enough to check the {{requestedPartitionsFlag}} first before synchronizing 
> for the actual requests (if needed). {{UnionInputGate}} already goes the same 
> way in its {{requestPartitions()}} implementation.



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