Siddharth Murching created SPARK-21799:
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Summary: 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].
`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.cache()` does set the public `df.storageLevel` member properly, so I'd
suggest replacing instances of `df.rdd.storageLevel` with df.storageLevel` in
MLlib algorithms (the same pattern shows up in LogisticRegression,
LinearRegression, and others).
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