Details
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Improvement
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Status: Closed
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Major
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Resolution: Fixed
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0.2.0
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None
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None
Description
When a job first starts, all task trackers ask the job tracker for jobs at once. With lots of task trackers, the job tracker gets very slow. The first type of task that the job tracker attempts to find is one with some of its input data stored on the same node as the task tracker. This case currently loops through tasks blindly, which, on average, requires numHosts/(replication*2) iterations to find a match (I think). This could be optimized by adding a table mapping from host to task.