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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2016/12/07 10:43:59 UTC
[jira] [Commented] (SPARK-18231) Optimise SizeEstimator
implementation
[ https://issues.apache.org/jira/browse/SPARK-18231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15728425#comment-15728425 ]
Apache Spark commented on SPARK-18231:
--------------------------------------
User 'a-roberts' has created a pull request for this issue:
https://github.com/apache/spark/pull/16196
> Optimise SizeEstimator implementation
> -------------------------------------
>
> Key: SPARK-18231
> URL: https://issues.apache.org/jira/browse/SPARK-18231
> Project: Spark
> Issue Type: Improvement
> Affects Versions: 1.6.2, 2.0.1
> Reporter: Adam Roberts
>
> The SizeEstimator is used in Spark to determine whether or not we need to spill -- we know spilling typically has an adverse impact on performance and it's something we want to minimise
> We can improve the implementation of SizeEstimator in a variety of ways to gain a performance and increase and ultimately a reduction in footprint by spilling less
> There are two phases involved here
> 1) refactor to use more efficient data structures, to avoid some reflection calls (expensive), to remove the use of ScalaRunTime.array_apply, to use ThreadLocalRandom, to store an array of field offsets instead of a list of pointer fields and to improve the performance of the sample method
> 2) add JDK specialisms to use exact object sizes to reduce overestimations for both Open/Oracle JDK users and IBM Java users. With an accurate estimator we can therefore spill less (--footprint, ++performance -- we have observed a 15% reduction in RDD sizes leading to potentially double digit performance gains on HiBench and micro benchmarks)
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