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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3136) Assign multiple tasks per TaskTracker heartbeat
Date Sun, 13 Jul 2008 06:35:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12613157#action_12613157
] 

Hemanth Yamijala commented on HADOOP-3136:
------------------------------------------

HADOOP-657 seems related in the sense that we report free disk space to the JobTracker from
the TaskTrackers and help it pick appropriate tasks. So, if we treat all these as resources
- slots, memory, disk space etc, maybe we should look at a uniform way of describing these.

> Assign multiple tasks per TaskTracker heartbeat
> -----------------------------------------------
>
>                 Key: HADOOP-3136
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3136
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Devaraj Das
>
> In today's logic of finding a new task, we assign only one task per heartbeat.
> We probably could give the tasktracker multiple tasks subject to the max number of free
slots it has - for maps we could assign it data local tasks. We could probably run some logic
to decide what to give it if we run out of data local tasks (e.g., tasks from overloaded racks,
tasks that have least locality, etc.). In addition to maps, if it has reduce slots free, we
could give it reduce task(s) as well. Again for reduces we could probably run some logic to
give more tasks to nodes that are closer to nodes running most maps (assuming data generated
is proportional to the number of maps). For e.g., if rack1 has 70% of the input splits, and
we know that most maps are data/rack local, we try to schedule ~70% of the reducers there.
> Thoughts?

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