[HDFS-8795] Improve InvalidateBlocks#node2blocks

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.8.0, 3.0.0-alpha1
• Target Version/s: 2.8.0
• Hadoop Flags: Reviewed
• Assignee: Yi Liu
• Reporter: Yi Liu
• Created: 17/Jul/15 08:48
• Updated: 30/Aug/16 01:31
• Resolved: 22/Jul/15 07:29

Description

Currently we use TreeMap for node2blocks, actually there are only two place may need sorted: dump, getDatanodes. But getDatanodes is called by computeInvalidateWork, and we do a shuffle there, so the sort is unnecssary. For dump, certainly we need to make few modification.
So we can use HashMap.

From memory and performance view, HashMap is better than TreeMap, a simliar optimization HDFS-7433.