Redundant memory copying in StreamKeyValUtil
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Key: MAPREDUCE-1248
URL: https://issues.apache.org/jira/browse/MAPREDUCE-1248
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: contrib/streaming
Reporter: Ruibang He
Priority: Minor
I found that when MROutputThread collecting the output of Reducer, it calls
StreamKeyValUtil.splitKeyVal() and two local byte-arrays are allocated there
for each line of output. Later these two byte-arrays are passed to variable key
and val. There are twice memory copying here, one is the System.arraycopy()
method, the other is inside key.set() / val.set().
This causes double times of memory copying for the whole output (may lead to
higher CPU consumption), and frequent temporay object allocation.
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