MapR 5.1 is at End of Life (EOL) and no longer supported. Please see the latest documentation. This documentation is not being updated.

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5.1 Administration
This section contains administration information such as managing your cluster, data, users, jobs and security information such as configuring your security environment and auditing.
Administrator Guide
Performance Tuning
MapReduce v1 Performance Tuning
Tune the Map Phase For MapReduce v1
Reuse JVMs

MapR 5.1 Documentation

Reuse JVMs

When the TaskTracker is instructed to start a map task, it tries to find an available JVM. Re-using JVMs is very important for performance, because it takes approximately one second and uses a lot of CPU. Set the value of the mapred.job.reuse.jvm.num.tasks parameter to -1 so that JVMs don't restart after a set number of tasks.