Uploaded image for project: 'Spark'
  1. Spark
  2. SPARK-2469

Lower shuffle compression buffer memory usage (replace LZF with Snappy for default compression codec)

    XMLWordPrintableJSON

    Details

    • Type: Improvement
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 1.1.0
    • Component/s: Shuffle, Spark Core
    • Labels:
    • Target Version/s:

      Description

      I was looking into the memory usage of shuffle and one annoying thing is the default compression codec (LZF) is that the implementation we use allocates buffers pretty generously. I did a simple experiment and found that creating 1000 LZFOutputStream allocated 198976424 bytes (~190MB). If we have a shuffle task that uses 10k reducers and 32 threads running currently, the memory used by the lzf stream alone would be ~ 60GB.

      In comparison, Snappy only allocates ~ 65MB for every 1k SnappyOutputStream. However, Snappy's compression is slightly lower than LZF's. In my experience, it leads to 10 - 20% increase in size. Compression ratio does matter here because we are sending data across the network.

        Attachments

          Issue Links

            Activity

              People

              • Assignee:
                rxin Reynold Xin
                Reporter:
                rxin Reynold Xin
              • Votes:
                0 Vote for this issue
                Watchers:
                2 Start watching this issue

                Dates

                • Created:
                  Updated:
                  Resolved: