Gopal V created HIVE-10128:
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Summary: LLAP: BytesBytesMultiHashMap does not allow concurrent
read-only access
Key: HIVE-10128
URL: https://issues.apache.org/jira/browse/HIVE-10128
Project: Hive
Issue Type: Sub-task
Reporter: Gopal V
Assignee: Sergey Shelukhin
The multi-threaded performance takes a serious hit when LLAP shares hashtables
between the probe threads running in parallel.
!hashmap-sync.png!
This is an explicit synchronized block inside ReusableRowContainer which
triggers this particular pattern.
!hashmap-sync-source.png!
Looking deeper into the code, the synchronization seems to be caused due to the
fact that WriteBuffers.setReadPoint modifies the otherwise read-only hashtable.
To generate this sort of result, run LLAP at a WARN log-level, to avoid all the
log synchronization that otherwise affects the thread sync.
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