Re: Getting starnge memory error

From:

Lew <noone@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 22 Jun 2009 19:07:50 -0400

Message-ID:

<h1p2s8$dhr$1@news.albasani.net>

zigzagdna wrote:

1. Keep in mind -Xmx is the maximum memory which process can have not
necssarily the memory used by the heap.

According to the documentation for 'java',
<http://java.sun.com/javase/6/docs/technotes/tools/windows/java.html>

-Xmxn
Specify the maximum size, in bytes, of the memory allocation pool.

The "memory allocation pool" is the heap, and does not include, for example,
the memory used by the JVM itself. So the amount specified by "-Xmx" is not
the whole process's but just that part dedicated to memory allocation.

<http://java.sun.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html>
reinforces this point:

initial heap size:

Larger of 1/64th of the machine's physical memory on the machine
or some reasonable minimum. Before J2SE 5.0, the default initial
heap size was a reasonable minimum, which varies by platform.
You can override this default using the -Xms command-line option.

maximum heap size:

Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0,
the default maximum heap size was 64MB. You can override this
default using the -Xmx command-line option.

--
Lew