[HBASE-15493] Default ArrayList size may not be optimal for Mutation

• Type: Improvement
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.0.0
• Component/s: Client, regionserver
• Assignee: Vladimir Rodionov
• Reporter: Vladimir Rodionov
• Created: 21/Mar/16 05:05
• Updated: 30/Jun/17 10:51

Description

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

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

Suggested:

  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;
  }

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.

Issue Links

• is part of: HBASE-15492 Memory usage optimizations