yarn-site.xml

  <property>

    <name>yarn.nodemanager.resource.memory-mb</name>

    <value>22528</value>

    <discription>每个节点可用内存,单位MB,默认9182MB</discription>

  </property>

  <property>

    <name>yarn.scheduler.minimum-allocation-mb</name>

    <value>1500</value>

    <discription>单个任务可申请最少内存，默认1024MB</discription>

  </property>

  <property>

    <name>yarn.scheduler.maximum-allocation-mb</name>

    <value>16384</value>

    <discription>单个任务可申请最大内存，默认8192MB</discription>

  </property>

  mapred-site.xml

  <property>

    <name>mapreduce.map.memory.mb</name>

    <value>1500</value>

    <description>每个Map任务的物理内存限制</description>

  </property>

  <property>

    <name>mapreduce.reduce.memory.mb</name>

    <value>3000</value>

    <description>每个Reduce任务的物理内存限制</description>

  </property>

  <property>

    <name>mapreduce.map.java.opts</name>

    <value>-Xmx1200m</value>

  </property>

  <property>

    <name>mapreduce.reduce.java.opts</name>

    <value>-Xmx2600m</value>

  </property>

mapreduce.map.memory.mb：每个map任务的内存，应该是大于或者等于Container的最小内存。

22528在yarn-site.xml配置的所有可用内存

按照上面的配置：每个slave可以运行map的数据<= 22528/1500,reduce任务的数量<=22528/3000

系统优化、jvm优化，hadoop配置优化