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Nicolas Poggi commented on SPARK-23310: --------------------------------------- [~sitalke...@gmail.com] we have found around 18% higher time in [Q95|https://github.com/databricks/spark-sql-perf/blob/master/src/main/resources/tpcds_2_4/q95.sql] of TPC-DS at least at scale factor 1000 (1TB). From 348.3. to 422.6s with the setting ON. The regression is in {{{color:#24292e}ReadAheadInputStream.read}}, and {color}seems to happen when reading a small amounts of data due to checks and locks. [~juliuszsompolski] can provide more internal details. Overall for TPC-DS SF 1000, we don't see any significat improvement (over 5%) with the feature ON in the rest of the queries. But of course other workloads can probably improve. > Perf regression introduced by SPARK-21113 > ----------------------------------------- > > Key: SPARK-23310 > URL: https://issues.apache.org/jira/browse/SPARK-23310 > Project: Spark > Issue Type: Bug > Components: Spark Core > Affects Versions: 2.3.0 > Reporter: Yin Huai > Priority: Blocker > > 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. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org