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From "salim achouche (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (DRILL-6301) Parquet Performance Analysis
Date Mon, 07 May 2018 20:51:00 GMT

     [ https://issues.apache.org/jira/browse/DRILL-6301?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

salim achouche resolved DRILL-6301.
    Resolution: Fixed
      Reviewer: Pritesh Maker

This is an analytical task.

> Parquet Performance Analysis
> ----------------------------
>                 Key: DRILL-6301
>                 URL: https://issues.apache.org/jira/browse/DRILL-6301
>             Project: Apache Drill
>          Issue Type: Task
>          Components: Storage - Parquet
>            Reporter: salim achouche
>            Assignee: salim achouche
>            Priority: Major
>             Fix For: 1.14.0
> _*Description -*_
>  * DRILL-5846 is meant to improve the Flat Parquet reader performance
>  * The associated implementation resulted in a 2x - 4x performance improvement
>  * Though during the review process ([pull request|[https://github.com/apache/drill/pull/1060])] few
key questions arised
> *_Intermediary Processing via Direct Memory vs Byte Arrays_*
>  * The main reasons for using byte arrays for intermediary processing is to a) avoid
the high cost of the DrillBuf checks (especially the reference counting) and b) benefit from
some observed Java optimizations when accessing byte arrays
>  * Starting with version 1.12.0, the DrillBuf enablement checks have been refined so
that memory access and reference counting checks can be enabled independently
>  * Benchmarking of Java's Direct Memory unsafe method using JMH indicates the performance
gap between heap vs direct memory  is very narrow except for few use-cases
>  * There are also concerns that the extra copy step (from direct memory into byte arrays)
will have a negative effect on performance; note that this overhead was not observed using
Intel's Vtune as the intermediary buffer were a) pinned to a single CPU, b) reused, and c)
small enough to remain in the L1 cache during columnar processing.
> _*Goal*_ 
>  * The Flat Parquet reader is amongst the few Drill columnar operators
>  * It is imperative that we agree on the most optimal processing pattern so that the
decisions that we take within this Jira are not only applied to Parquet but to all Drill columnar
> _*Methodology*_ 
>  # Assess the performance impact of using intermediary byte arrays (as described above)
>  # Prototype a solution using Direct Memory and DrillBuf checks off, access checks on,
all checks on
>  # Make an educated decision on which processing pattern should be adopted
>  # Decide whether it is ok to use Java's unsafe API (and through what mechanism) on byte
arrays (when the use of byte arrays is a necessity)

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