Ability to thread task execution
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Key: HADOOP-2990
URL: https://issues.apache.org/jira/browse/HADOOP-2990
Project: Hadoop Core
Issue Type: Improvement
Components: mapred
Environment: All
Reporter: Holden Robbins
Currently Hadoop spawns a single threaded JVM for each task. While good for
many tasks, this does not maximize resource usage for slaves that have many
cores (machines with more cores are getting more cost effective everyday) _and_
are running jobs that require many gigabytes of read-only in-memory resources
to maximize throughput. Running in separate JVMs requires redundantly loading
large amounts of data, reducing the possible number of parallel tasks that can
run per a machine even though more cpus are available.
Adding this ability will give hadoop users the flexibility to balance their
need for maximizing memory usage & throughput and task segmentation.
Note: This is a blocking bug in porting processes over to hadoop for my own
organization. I am testing a patch for this now that leaves the existing
behavior for single threaded operation in-tact. All synchronization is done
through wrapper classes and helper methods and should not add any overhead to
non-threaded processes.
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