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  1. Spark
  2. SPARK-23310

Perf regression introduced by SPARK-21113

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Blocker
    • Resolution: Done
    • Affects Version/s: 2.3.0
    • Fix Version/s: 2.3.0
    • Component/s: Spark Core
    • Labels:
      None
    • Target Version/s:

      Description

      While running all TPC-DS queries with SF set to 1000, we noticed that Q95 (https://github.com/databricks/spark-sql-perf/blob/master/src/main/resources/tpcds_2_4/q95.sql) has noticeable regression (11%). After looking into it, we found that the regression was introduced by SPARK-21113. Specially, ReadAheadInputStream gets lock congestion. After setting spark.unsafe.sorter.spill.read.ahead.enabled set to false, the regression disappear and the overall performance of all TPC-DS queries has improved.

       

      I am proposing that we set spark.unsafe.sorter.spill.read.ahead.enabled to false by default for Spark 2.3 and re-enable it after addressing the lock congestion issue. 

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              • Assignee:
                sitalkedia@gmail.com Sital Kedia
                Reporter:
                yhuai Yin Huai
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                • Created:
                  Updated:
                  Resolved: