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Java Heap Size

kodi pitta
Greenhorn

Joined: Sep 30, 2003
Posts: 1
I have set the max heap size for my java program to 512m, by specifying
java -Xmx512m.
However, when I run a test program that invokes java.lang.Runtime.maxMemory(), which is the amount of memory that the JVM will attempt to use, I don't see 512m, instead I only see about 510MB.
How does one explain the difference ?
Mani Ram
Ranch Hand

Joined: Mar 11, 2002
Posts: 1140
Which java version are you using.
When I tested, it is giving 576 MB! In fact, it is actually giving 64MB more than what ever I specify.


Mani
Quaerendo Invenietis
Mani Ram
Ranch Hand

Joined: Mar 11, 2002
Posts: 1140
Okay...the problem I posted is a bug, which was fixed in 1.4.2.
Here are the details.
But I don't have any answer to the initial question.
John Smith
Ranch Hand

Joined: Oct 08, 2001
Posts: 2937
But I don't have any answer to the initial question.
Turns out to be another reported bug:
Bug Id 4391499: java.lang.Runtime.maxMemory() returns value different from -Xmx option.
However, Sun set the status to "closed, will not be fixed" with the following explanation:
Not a bug. The interpretation of the -Xmx flag is VM-dependent. Some VMs, including HotSpot, enforce a lower bound on the effective value of this option.
 
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subject: Java Heap Size