忽然遇到报错：ERROR spark.SparkContext: Error initializing SparkContext.

java.lang.IllegalArgumentException: System memory 100663296 must be at least 4.718592E8. Please use a larger heap size.

在Eclipse里开发Spark项目，尝试直接在spark里运行程序的时候，遇到下面这个报错：

很明显，这是JVM申请的memory不够导致无法启动SparkContext。但是该怎么设呢？

但是检查了一下启动脚本

#!/bin/bash
/usr/local/spark-1.6.0/bin/spark-submit  \
--class cn.spark.study.Opt17_WordCount \
--num-executors 3 \
--driver-memory 100m \ 
--executor-memory 100m \
--executor-cores 3 \
/root/sparkstudy/Java/spark-study-java-0.0.1-SNAPSHOT-jar-with-dependencies.jar \
--master  spark://yun01:7077

看来是driver内存不足，当给了 driver的内存尝试着增大到400M 时候

 仍旧是爆出如下错
 Exception in thread "main" java.lang.IllegalArgumentException: System memory 402128896 must be at least 4.718592E8. Please use a larger heap size.

 此时就可以再次调大一些 给了1g（应该是从spark升级1.5或者1.6之后才出现这样的问题，）
 然后再次运行之后正常得出结果
 还可以指定在代码中 ：
  val conf = new SparkConf().setAppName("word count")
 conf.set("spark.testing.memory", "1g")//后面的值大于512m即可
 
 /**
    * Return the total amount of memory shared between execution and storage, in bytes.
    */
   private def getMaxMemory(conf: SparkConf): Long = {
     val systemMemory = conf.getLong("spark.testing.memory", Runtime.getRuntime.maxMemory)
     val reservedMemory = conf.getLong("spark.testing.reservedMemory",
       if (conf.contains("spark.testing")) 0 else RESERVED_SYSTEM_MEMORY_BYTES)
     val minSystemMemory = reservedMemory * 1.5
     if (systemMemory < minSystemMemory) {
       throw new IllegalArgumentException(s"System memory $systemMemory must " +
         s"be at least $minSystemMemory. Please use a larger heap size.")
     }
     val usableMemory = systemMemory - reservedMemory
     val memoryFraction = conf.getDouble("spark.memory.fraction", 0.75)
     (usableMemory * memoryFraction).toLong
   }


 
 所以，这里主要是val systemMemory = conf.getLong("spark.testing.memory", Runtime.getRuntime.maxMemory)。
 conf.getLong()的定义和解释是
  
 getLong(key: String, defaultValue: Long): Long
 Get a parameter as a long, falling back to a default if not set