Todd Lipcon created MAPREDUCE-5821:
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Summary: IFile merge allocates new byte array for every value
Key: MAPREDUCE-5821
URL: https://issues.apache.org/jira/browse/MAPREDUCE-5821
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: performance, task
Affects Versions: 2.4.1
Reporter: Todd Lipcon
Assignee: Todd Lipcon
I wrote a standalone benchmark of the MapOutputBuffer and found that it did a
lot of allocations during the merge phase. After looking at an allocation
profile, I found that IFile.Reader.nextRawValue() would always allocate a new
byte array for every value, so the allocation rate goes way up during the merge
phase of the mapper. I imagine this also affects the reducer input, though I
didn't profile that.
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