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https://issues.apache.org/jira/browse/MAPREDUCE-1129?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12768530#action_12768530
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Zheng Shao commented on MAPREDUCE-1129:
---------------------------------------
One simple idea is to change the interface of LoadManager:
From:
[code}
boolean LoadManager.canAssignMap(...)
boolean LoadManager.canAssignReduce(...)
{code}
To:
[code}
int LoadManager.canAssignMapCount(...)
int LoadManager.canAssignReduceCount(...)
{code}
The LoadManager returns the number of map(or reduce) tasks that can be assigned
to this TaskTracker, so we can assign multiple tasks in a single heartbeat.
The default implementation of the new functions can directly call the old
functions to return 0 or 1, to provide backward compatibility with user-defined
LoadManagers.
> Assign multiple Map and Reduce tasks in Fairscheduler
> -----------------------------------------------------
>
> Key: MAPREDUCE-1129
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1129
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: contrib/fair-share
> Affects Versions: 0.20.1
> Reporter: Scott Chen
>
> In Hadoop-0.20, the period of heartbeat becomes much longer.
> Fairscheduler assigns at most one Map and one Reduce task per heartbeat.
> This makes the cluster become very inefficient. Often time only half of the
> slots are used.
> One idea is that we make Fairscheduler detect this situation (cluster under
> used) and scheduler more tasks in a heartbeat.
> Thoughts?
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