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From mateiz <...@git.apache.org>
Subject [GitHub] spark pull request: SPARK-2045 Sort-based shuffle
Date Mon, 28 Jul 2014 03:42:33 GMT
Github user mateiz commented on the pull request:

    https://github.com/apache/spark/pull/1499#issuecomment-50297730
  
    Are map tasks spilling by any chance? There is one issue in this right now, which is that
if your map task spills to disk, you need to spill multiple times with the sort-based shuffle,
whereas with the old code you would directly open one file for each reduce task and write
data to it. I think we can add the same behavior here if the # of reduce tasks is small enough
(the problem before was that you'd open 10,000 files for 10,000 reduce tasks and allocate
lots of space for buffers, not to mention do lots of random I/O). I would do that in a separate
pull request though. For other things, like reduceByKey, this should have similar performance
to the hash-based shuffle.


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