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https://issues.apache.org/jira/browse/SPARK-22147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-22147:
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Assignee: (was: Apache Spark)
> BlockId.hashCode allocates a StringBuilder/String on each call
> --------------------------------------------------------------
>
> Key: SPARK-22147
> URL: https://issues.apache.org/jira/browse/SPARK-22147
> Project: Spark
> Issue Type: Bug
> Components: Block Manager
> Affects Versions: 2.2.0
> Reporter: Sergei Lebedev
> Priority: Minor
>
> The base class {{BlockId}}
> [defines|https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/storage/BlockId.scala#L44]
> {{hashCode}} and {{equals}} for all its subclasses in terms of {{name}}.
> This makes the definitions of different ID types [very
> concise|https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/storage/BlockId.scala#L52].
> The downside, however, is redundant allocations. While I don't think this
> could be the major issue, it is still a bit disappointing to increase GC
> pressure on the driver for nothing. For our machine learning workloads, we've
> seen as much as 10% of all allocations on the driver coming from
> {{BlockId.hashCode}} calls done for
> [BlockManagerMasterEndpoint.blockLocations|https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/storage/BlockManagerMasterEndpoint.scala#L54].
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