Sergey Shelukhin created HIVE-10772:
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Summary: LLAP: perf dips with IO elevator disabled
Key: HIVE-10772
URL: https://issues.apache.org/jira/browse/HIVE-10772
Project: Hive
Issue Type: Sub-task
Reporter: Sergey Shelukhin
If Q1 TPCH is run 10 times in a row on the same cluster, with IO elevator,the
perf stays relatively consistent (or improves due to JIT and stuff). Without,
there's a large perf dip in the middle (usually dag #3 or so for me), then
recovery.
This dip is not caused directly by GC time, and at least in my case I cannot
see any particular part becoming slower in YK profiles, or any obvious
correlates. One can easily see tasks slow down from 3-7 to 10-30 seconds (up to
60 with slow HDFS reads). One thing that happens is that kernel CPU time goes
up to 9-12% on all the daemons when the slowdown is "ramping up" and occuring,
compared to usual 0-3% levels. I didn't investigate much where that comes from
since this is not a mainline scenario.
Still, interesting to learn what causes this.
YK dumps provided upon request.
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