Robert Joseph Evans created MAPREDUCE-4752:
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Summary: Reduce MR AM memory usage through String Interning
Key: MAPREDUCE-4752
URL: https://issues.apache.org/jira/browse/MAPREDUCE-4752
Project: Hadoop Map/Reduce
Issue Type: Improvement
Components: mrv2
Reporter: Robert Joseph Evans
Assignee: Robert Joseph Evans
There are a lot of strings that are duplicates of one another in the AM. This
comes from all of the PB events the come across the wire and also tasks
heart-beating in through the umbilical. There are even several duplicates from
Configuration. By "interning" all of these strings on the Heap I have been
able to reduce the resting memory usage of the AM to be about 5KB per task
attempt. With about half of this coming from counters. This results in a 5MB
heap for a typical 1000 task job, or a 500MB heap for a 100,000 task attempt
job. I think I could cut the size of the counters in half by completely
rewriting how counters work in the AM and History Server, but I don't think it
is worth it at this point.
I am still investigating what the memory usage of the AM is like when running
very large jobs, and I will probably have a follow-up JIRA for reducing that
memory usage as well.
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