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From "Apache Spark (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (SPARK-21799) KMeans performance regression (5-6x slowdown) in Spark 2.2
Date Sat, 02 Sep 2017 04:34:02 GMT

     [ https://issues.apache.org/jira/browse/SPARK-21799?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Apache Spark reassigned SPARK-21799:
------------------------------------

    Assignee:     (was: Apache Spark)

> KMeans performance regression (5-6x slowdown) in Spark 2.2
> ----------------------------------------------------------
>
>                 Key: SPARK-21799
>                 URL: https://issues.apache.org/jira/browse/SPARK-21799
>             Project: Spark
>          Issue Type: Bug
>          Components: MLlib
>    Affects Versions: 2.2.0
>            Reporter: Siddharth Murching
>
> I've been running KMeans performance tests using [spark-sql-perf|https://github.com/databricks/spark-sql-perf/]
and have noticed a regression (slowdowns of 5-6x) when running tests on large datasets in
Spark 2.2 vs 2.1.
> The test params are:
> * Cluster: 510 GB RAM, 16 workers
> * Data: 1000000 examples, 10000 features
> After talking to [~josephkb], the issue seems related to the changes in [SPARK-18356|https://issues.apache.org/jira/browse/SPARK-18356]
introduced in [this PR|https://github.com/apache/spark/pull/16295].
> It seems `df.cache()` doesn't set the storageLevel of `df.rdd`, so `handlePersistence`
is true even when KMeans is run on a cached DataFrame. This unnecessarily causes another copy
of the input dataset to be persisted.
> As of Spark 2.1 ([JIRA link|https://issues.apache.org/jira/browse/SPARK-16063]) `df.storageLevel`
returns the correct result after calling `df.cache()`, so I'd suggest replacing instances
of `df.rdd.getStorageLevel` with df.storageLevel` in MLlib algorithms (the same pattern shows
up in LogisticRegression, LinearRegression, and others). I've verified this behavior in [this
notebook|https://databricks-prod-cloudfront.cloud.databricks.com/public/4027ec902e239c93eaaa8714f173bcfc/5211178207246023/950505630032626/7788830288800223/latest.html]



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