[jira] Updated: (HADOOP-4788) Set mapred.fairscheduler.assignmultiple to true by default

["Matei Zaharia (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-4788?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Matei Zaharia updated HADOOP-4788:
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    Attachment: hadoop-4788-v0.patch

Here's a patch that fixes this. It leaves assignmultiple off in the unit tests for ease of testing however.

> Set mapred.fairscheduler.assignmultiple to true by default
> ----------------------------------------------------------
>
>                 Key: HADOOP-4788
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4788
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: contrib/fair-share
>            Reporter: Matei Zaharia
>            Priority: Trivial
>         Attachments: hadoop-4788-v0.patch
>
>
> Pretty much all users of the fair scheduler are using the "assignmultiple" feature which lets it launch reduce tasks at the same time as map tasks (on the same heartbeats), leading to reduces starting faster. This is also going to happen in Hadoop by default in HADOOP-3136. So we should set it to true by default and perhaps even remove the config parameter.

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