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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9913) Improve output serialization only once in RecordWriter
Date Fri, 14 Sep 2018 09:54:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9913?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16614604#comment-16614604
] 

ASF GitHub Bot commented on FLINK-9913:
---------------------------------------

zhijiangW commented on a change in pull request #6417: [FLINK-9913][runtime] Improve output
serialization only once in RecordWriter
URL: https://github.com/apache/flink/pull/6417#discussion_r217661048
 
 

 ##########
 File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/api/writer/RecordWriter.java
 ##########
 @@ -113,11 +113,7 @@ public void broadcastEmit(T record) throws IOException, InterruptedException
{
 	 * This is used to send LatencyMarks to a random target channel.
 	 */
 	public void randomEmit(T record) throws IOException, InterruptedException {
-		serializer.serializeRecord(record);
-
-		if (copyFromSerializerToTargetChannel(rng.nextInt(numChannels))) {
-			serializer.prune();
-		}
+		emit(record, new int[] { rng.nextInt(numChannels) });
 
 Review comment:
   got it

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> Improve output serialization only once in RecordWriter
> ------------------------------------------------------
>
>                 Key: FLINK-9913
>                 URL: https://issues.apache.org/jira/browse/FLINK-9913
>             Project: Flink
>          Issue Type: Improvement
>          Components: Network
>    Affects Versions: 1.6.0
>            Reporter: zhijiang
>            Assignee: zhijiang
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.7.0
>
>
> Currently the {{RecordWriter}} emits output into multi channels via {{ChannelSelector}} 
or broadcasts output to all channels directly. Each channel has a separate {{RecordSerializer}}
for serializing outputs, that means the output will be serialized as many times as the number
of selected channels.
> As we know, data serialization is a high cost operation, so we can get good benefits
by improving the serialization only once.
> I would suggest the following changes for realizing it.
>  # Only one {{RecordSerializer}} is created in {{RecordWriter}} for all the channels.
>  # The output is serialized into the intermediate data buffer only once for different
channels.
>  # The intermediate serialization results are copied into different {{BufferBuilder}}s
for different channels.
> An additional benefit by using a single serializer for all channels is that we get a
potentially significant reduction on heap space overhead from fewer intermediate serialization
buffers (only once we got over 5MiB, these buffers were pruned back to 128B!).



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