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From nagarjuna kanamarlapudi <nagarjuna.kanamarlap...@gmail.com>
Subject Child JVM memory allocation / Usage
Date Sun, 24 Mar 2013 10:10:53 GMT

I configured  my child jvm heap to 2 GB. So, I thought I could really read
1.5GB of data and store it in memory (mapper/reducer).

I wanted to confirm the same and wrote the following piece of code in the
configure method of mapper.


public void configure(JobConf job) {

System.out.println("FREE MEMORY -- "

+ Runtime.getRuntime().freeMemory());

System.out.println("MAX MEMORY ---" + Runtime.getRuntime().maxMemory());


Surprisingly the output was

FREE MEMORY -- 341854864  = 320 MB
MAX MEMORY ---1908932608  = 1.9 GB

I am just wondering what processes are taking up that extra 1.6GB of
heap which I configured for the child jvm heap.

Appreciate in helping me understand the scenario.


Nagarjuna K

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