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courses:mapreduce-tutorial:step-26 [2012/01/28 15:45] straka |
courses:mapreduce-tutorial:step-26 [2012/01/28 20:21] straka |
====== MapReduce Tutorial : Counters and job configuration ====== | ====== MapReduce Tutorial : Counters, compression and job configuration ====== |
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===== Counters ===== | ===== Counters ===== |
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Apart from already mentioned [[.:step-9#a-brief-list-of-hadoop-options|brief list of Hadoop properties]], there is one important Java-specific property: | Apart from already mentioned [[.:step-9#a-brief-list-of-hadoop-options|brief list of Hadoop properties]], there is one important Java-specific property: |
* **''mapred.child.java.opts''** with default value **''-Xmx200m''**. This property sets the Java options used for every task attempt (mapper, reducer, combiner, partitioner). The default value ''-Xmx200m'' sets the size of | * **''mapred.child.java.opts''** with default value **''-Xmx200m''**. This property sets the Java options used for every task attempt (mapper, reducer, combiner, partitioner). The default value ''-Xmx200m'' specifies the maximum size of memory allocation pool. If your mappers and reducers need 1GB memory, use ''-Xmx1024m''. Other Java options can be found in ''man java''. |