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Koerr
Asked: 2012-12-05 03:05:11 +0800 CST

Why does the java -Xmx not working? [duplicate]

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Possible Duplicate:
Linux out of memory on VPS

In my Ubuntu 11.10 VPS, Before I run the jar file:

# free -m
             total       used       free     shared    buffers     cached
Mem:           256          5        250          0          0          0
-/+ buffers/cache:          5        250
Swap:            0          0          0

Run a jar file that limited to maximum of 32M memory:

java -Xms8m -Xmx32m -jar ./my.jar

Now the memory state as follows:

# free -m
             total       used       free     shared    buffers     cached
Mem:           256        155        100          0          0          0
-/+ buffers/cache:        155        100
Swap:            0          0          0

This jar occupied 150M memory.

And I can't run any other java command:

# java -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

# java -Xmx8m -version  
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

I want to know why the -Xmx parameter does not take effect?

How can I limit the jar file using the memory?

linux

2 Answers

  1. The -Xmx parameter defines the heap size, aka the memory you can allocate in the program. The java binary and the loaded jar file each needs additional space, naturally.

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  2. It's not Java who used up all the memory, the system also consumes RAM to cache data (look at the cache output from free -m and top)

    You're running Java (BLOATED software) on a 256MB RAM VPS without swap. Are you really really sure you want to go down this path?

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