[jira] Commented: (MAPREDUCE-1333) Parallel running tasks on one single node may slow down the performance

["Hong Tang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-1333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796446#action_12796446 ] 

Hong Tang commented on MAPREDUCE-1333:
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Could you provide more details? hardware spec, your benchmark program, and what do you observe as the bottleneck resource?

> Parallel running tasks on one single node may slow down the performance
> -----------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1333
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1333
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker, task, tasktracker
>    Affects Versions: 0.20.1
>            Reporter: Zhaoning Zhang
>
> When I analysis running tasks performance, I found that parallel running tasks on one single node will not be better performance than the serialized ones.
> We can set mapred.tasktracker.{map|reduce}.tasks.maximum = 1 individually, but there will be parallel map AND reduce tasks.
> And I wonder it's true in the real commercial clusters?

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