[
https://issues.apache.org/jira/browse/HIVE-10128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14385060#comment-14385060
]
Sergey Shelukhin commented on HIVE-10128:
-----------------------------------------
Git is down, so merge won't propagate. I will attach the patch here for now, to
commit I need to merge and I cannot deal with SVN anymore
> 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
> Attachments: hashmap-sync-source.png, hashmap-sync.png
>
>
> 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.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
