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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4103) Remove System.gc() call from the map-join local-task loop
Date Fri, 01 Mar 2013 22:03:14 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13590988#comment-13590988
] 

Gopal V commented on HIVE-4103:
-------------------------------

On a run, the difference was 

{code}
2013-03-01 04:57:21	Upload 1 File to: file:/tmp/root/hive_2013-03-01_16-56-53_785_1192800933446838868/-local-10002/HashTable-Stage-1/MapJoin-demographics-01--.hashtable
File size: 18426794
2013-03-01 04:57:21	End of local task; Time Taken: 22.426 sec.
{code}

versus, after-fix

{code}
2013-03-01 04:56:26	Upload 1 File to: file:/tmp/root/hive_2013-03-01_16-56-01_539_5116929752955084952/-local-10002/HashTable-Stage-1/MapJoin-demographics-01--.hashtable
File size: 18426794
2013-03-01 04:56:26	End of local task; Time Taken: 19.874 sec.
{code}
                
> Remove System.gc() call from the map-join local-task loop
> ---------------------------------------------------------
>
>                 Key: HIVE-4103
>                 URL: https://issues.apache.org/jira/browse/HIVE-4103
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Gopal V
>            Priority: Minor
>         Attachments: HIVE-4103.patch
>
>
> Hive's HashMapWrapper calls System.gc() twice within the HashMapWrapper::isAbort() which
produces a significant slow-down during the loop.
> {code}
> 2013-03-01 04:54:28 The gc calls took 677 ms
> 2013-03-01 04:54:28     Processing rows:        200000  Hashtable size: 199999  Memory
usage:   62955432        rate:   0.033
> 2013-03-01 04:54:31 The gc calls took 956 ms
> 2013-03-01 04:54:31     Processing rows:        300000  Hashtable size: 299999  Memory
usage:   90826656        rate:   0.048
> 2013-03-01 04:54:33 The gc calls took 967 ms
> 2013-03-01 04:54:33     Processing rows:        384160  Hashtable size: 384160  Memory
usage:   114412712       rate:   0.06
> {code}

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