[jira] [Created] (HBASE-15493) Default ArrayList size may not be optimal for Mutation

["Vladimir Rodionov (JIRA)" <ji...@apache.org>]

Vladimir Rodionov created HBASE-15493:
-----------------------------------------

             Summary: Default ArrayList size may not be optimal for Mutation
                 Key: HBASE-15493
                 URL: https://issues.apache.org/jira/browse/HBASE-15493
             Project: HBase
          Issue Type: Improvement
          Components: Client, regionserver
    Affects Versions: 2.0.0
            Reporter: Vladimir Rodionov
            Assignee: Vladimir Rodionov
             Fix For: 2.0.0


{code}
  List<Cell> getCellList(byte[] family) {
    List<Cell> list = this.familyMap.get(family);
    if (list == null) {
      list = new ArrayList<Cell>();
    }
    return list;
  }
{code}

Creates list of size 10, this is up to 80 bytes per column family in mutation object. 

Suggested:
{code}
  List<Cell> getCellList(byte[] family) {
    List<Cell> list = this.familyMap.get(family);
    if (list == null) {
      list = new ArrayList<Cell>(CELL_LIST_INITIAL_CAPACITY);
    }
    return list;
  }
{code}

CELL_LIST_INITIAL_CAPACITY = 2 in the patch, this is debatable. For mutation where every CF has 1 cell, this gives decent reduction in memory allocation rate in both client and server during write workload. ~2%, not a big number, but as I said, already, memory optimization will include many small steps.





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