[jira] [Updated] (HIVE-10128) BytesBytesMultiHashMap does not allow concurrent read-only access

["Sergey Shelukhin (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-10128?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sergey Shelukhin updated HIVE-10128:
------------------------------------
    Summary: BytesBytesMultiHashMap does not allow concurrent read-only access  (was: LLAP: BytesBytesMultiHashMap does not allow concurrent read-only access)

> 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
>             Fix For: llap
>
>         Attachments: HIVE-10128.01.patch, HIVE-10128.patch, hashmap-after.png, 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.



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