hadoop的内存heap大小的配置参数 .

此为小知识点，相信大家一看就明白，一般heap大小的表示为-Xmx。。


1、tasktracker的heapsize的大小设置

<property>
  <name>mapred.child.java.opts</name>
  <value>-Xmx200m</value>
  <description>Java opts for the task tracker child processes.  
  The following symbol, if present, will be interpolated: @taskid@ is replaced 
  by current TaskID. Any other occurrences of '@' will go unchanged.
  For example, to enable verbose gc logging to a file named for the taskid in
  /tmp and to set the heap maximum to be a gigabyte, pass a 'value' of:
        -Xmx1024m -verbose:gc -Xloggc:/tmp/@taskid@.gc
  
  The configuration variable mapred.child.ulimit can be used to control the
  maximum virtual memory of the child processes. 
  </description>
</property>
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2、namenode、datanode和jobtracker的heapsize的设置：
hadoop-env.sh中的HADOOP_HEAPSIZE的变量来制定