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https://issues.apache.org/jira/browse/FLINK-10142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16583984#comment-16583984
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ASF GitHub Bot commented on FLINK-10142:
----------------------------------------
pnowojski commented on a change in pull request #6555: [FLINK-10142][network]
reduce locking around credit notification
URL: https://github.com/apache/flink/pull/6555#discussion_r210916528
##########
File path:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannel.java
##########
@@ -191,15 +191,15 @@ void retriggerSubpartitionRequest(int subpartitionIndex)
throws IOException, Int
checkError();
final Buffer next;
- final int remaining;
+ final boolean moreAvailable;
synchronized (receivedBuffers) {
next = receivedBuffers.poll();
- remaining = receivedBuffers.size();
+ moreAvailable = !receivedBuffers.isEmpty();
}
numBytesIn.inc(next.getSizeUnsafe());
- return Optional.of(new BufferAndAvailability(next, remaining >
0, getSenderBacklog()));
+ return Optional.of(new BufferAndAvailability(next,
moreAvailable, getSenderBacklog()));
Review comment:
This has also nothing to do with `optimisations reducing lock contention`.
Can you extract those changes to separate hotfix? If someone in the future will
be looking at `git blame` regarding real `optimisations reducing lock
contention` he will have the same "wtf" moments as me right now ;)
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> Reduce synchronization overhead for credit notifications
> --------------------------------------------------------
>
> Key: FLINK-10142
> URL: https://issues.apache.org/jira/browse/FLINK-10142
> Project: Flink
> Issue Type: Bug
> Components: Network
> Affects Versions: 1.5.2, 1.6.0, 1.7.0
> Reporter: Nico Kruber
> Assignee: Nico Kruber
> Priority: Major
> Labels: pull-request-available
>
> When credit-based flow control was introduced, we also added some checks and
> optimisations for uncommon code paths that make common code paths
> unnecessarily more expensive, e.g. checking whether a channel was released
> before forwarding a credit notification to Netty. Such checks would have to
> be confirmed by the Netty thread anyway and thus only add additional load for
> something that happens only once (per channel).
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