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From "Devaraj Das (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3136) Assign multiple tasks per TaskTracker heartbeat
Date Mon, 31 Mar 2008 13:08:24 GMT
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
             Fix For: 0.18.0

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, we
try to schedule ~70% of the reducers there.


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