jaehoon ko created MAPREDUCE-5946:
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Summary: Last spill of map task is not necessary for final merge
Key: MAPREDUCE-5946
URL: https://issues.apache.org/jira/browse/MAPREDUCE-5946
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: performance, security
Affects Versions: 2.4.0
Reporter: jaehoon ko
Assignee: jaehoon ko
In map task, merge starts only after the last spill is completely written to
disk. This is not necessary nor efficient because the last spill should to be
reloaded soon for merge, probably immediately because spills are merged in the
order of their sizes and the last spill is likely smallest. OS page cache is
not the answer due to its opportunistic nature.
I'm starting to work on it. Please give me your thoughts.
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