[jira] [Created] (SPARK-20776) Fix performance problems in TaskMetrics.nameToAccums map initialization

["Josh Rosen (JIRA)" <ji...@apache.org>]

Josh Rosen created SPARK-20776:
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             Summary: Fix performance problems in TaskMetrics.nameToAccums map initialization
                 Key: SPARK-20776
                 URL: https://issues.apache.org/jira/browse/SPARK-20776
             Project: Spark
          Issue Type: Improvement
          Components: Spark Core
    Affects Versions: 2.2.0
            Reporter: Josh Rosen
            Assignee: Josh Rosen
         Attachments: screenshot-1.png

In 

{code}
./bin/spark-shell --master=local[64]
{code}

I ran 

{code}
  sc.parallelize(1 to 100000, 100000).count()
{code}

and profiled the time spend in the LiveListenerBus event processing thread. I discovered that the majority of the time was being spent initializing the {{TaskMetrics.nameToAccums}} map (see attached screenshot). By replacing the use of Scala's LinkedHashMap with a pre-sized Java hashmap I was able to remove this bottleneck and prevent dropped listener events.



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