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Posted to mapreduce-dev@hadoop.apache.org by "zhihai xu (JIRA)" <ji...@apache.org> on 2014/09/02 11:56:21 UTC
[jira] [Created] (MAPREDUCE-6063) In sortAndSpill of MapTask.java,
size is calculated wrongly when bufend < bufstart.
zhihai xu created MAPREDUCE-6063:
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Summary: In sortAndSpill of MapTask.java, size is calculated wrongly when bufend < bufstart.
Key: MAPREDUCE-6063
URL: https://issues.apache.org/jira/browse/MAPREDUCE-6063
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: mrv1, mrv2
Reporter: zhihai xu
Assignee: zhihai xu
In sortAndSpill of MapTask.java, size is calculated wrongly when bufend < bufstart. we should change (bufvoid - bufend) + bufstart to (bufvoid - bufstart) + bufend.
Should change
{code}
long size = (bufend >= bufstart
? bufend - bufstart
: (bufvoid - bufend) + bufstart) +
partitions * APPROX_HEADER_LENGTH;
{code}
to:
{code}
long size = (bufend >= bufstart
? bufend - bufstart
: (bufvoid - bufstart) + bufend) +
partitions * APPROX_HEADER_LENGTH;
{code}
It is because when wraparound happen (bufend < bufstart) , the size should
bufvoid - bufstart (bigger one) + bufend(small one).
You can find similar code implementation in MapTask.java:
{code}
mapOutputByteCounter.increment(valend >= keystart
? valend - keystart
: (bufvoid - keystart) + valend);
{code}
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