You are viewing a plain text version of this content. The canonical link for it is here.
Posted to mapreduce-dev@hadoop.apache.org by "Binglin Chang (JIRA)" <ji...@apache.org> on 2011/08/30 05:48:38 UTC
[jira] [Created] (MAPREDUCE-2910) Allow empty MapOutputFile
segments
Allow empty MapOutputFile segments
----------------------------------
Key: MAPREDUCE-2910
URL: https://issues.apache.org/jira/browse/MAPREDUCE-2910
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: task, tasktracker
Affects Versions: 0.20.2, 0.23.0
Reporter: Binglin Chang
Priority: Minor
Fix For: 0.23.0
As the scale of cluster and job get larger, we see a lot of empty partitions in MapOutputFile due to large reduce numbers or partition skew. When map output compression is enabled, empty map output partitions gets larger & has additional compressor/decompressor initialization overhead.
This can be optimized by allowing empty MapOutputFile segments, where the rawLength & partLength of IndexRecord all equal to 0. Corresponding support need to be added to IFile reader, writer, and reduce shuffle copier.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira