[MAPREDUCE-3511] Counters occupy a good part of AM heap

• Type: Sub-task
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.23.0
• Fix Version/s: 0.23.1
• Component/s: mr-am, mrv2
• Hadoop Flags: Reviewed
• Release Note: Removed a multitude of cloned/duplicate counters in the AM thereby reducing the AM heap size and preventing full GCs.
• Assignee: Vinod Kumar Vavilapalli
• Reporter: Siddharth Seth
• Created: 06/Dec/11 00:27
• Updated: 05/Mar/12 02:49
• Resolved: 09/Jan/12 21:08

Description

Per task counters seem to be occupying a good part of an AMs heap. Looks like more than 50% of what's used by a TaskAttemptImpl object.
This could be optimized by interning strings or possibly using mrv1 counters which are optimized. Currently counters are converted from mrv1 to mrv2 format for in memory storage. The conversion could be delayed till it's actually required for RPC transfers.