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Editorial Team
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Asked: 2026-05-26T05:50:55+00:00

This problem is specifically about Sun Java JVM running on Linux x86-64 . I’m

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This problem is specifically about Sun Java JVM running on Linux x86-64. I’m trying to figure out why the Sun JVM takes so much of system’s physical memory even when I have set Heap and Non-Heap limits.

The program I’m running is Eclipse 3.7 with multiple plugins/features. The most used features are PDT, EGit and Mylyn. I’m starting the Eclipse with the following command line switches:

-nosplash -vmargs -Xincgc -Xms64m -Xmx200m -XX:NewSize=8m -XX:PermSize=80m -XX:MaxPermSize=150m -XX:MaxPermHeapExpansion=10m -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSInitiatingOccupancyOnly -XX:+UseParNewGC -XX:+CMSIncrementalMode -XX:+CMSIncrementalPacing -XX:CMSIncrementalDutyCycleMin=0 -XX:CMSIncrementalDutyCycle=5 -XX:GCTimeRatio=49 -XX:MaxGCPauseMillis=50 -XX:GCPauseIntervalMillis=1000 -XX:+UseCMSCompactAtFullCollection -XX:+CMSClassUnloadingEnabled -XX:+DoEscapeAnalysis -XX:+UseCompressedOops -XX:+AggressiveOpts -Dorg.eclipse.swt.internal.gtk.disablePrinting

Worth noting are especially the switches: 

-Xms64m -Xmx200m -XX:NewSize=8m -XX:PermSize=80m -XX:MaxPermSize=150m

These switches should limit the JVM Heap to maximum of 200 MB and Non-Heap to 150 MB (“CMS Permanent generation” and “Code Cache” as labeled by JConsole). Logically the JVM should take total of 350 MB plus the internal overhead required by the JVM.

In reality, the JVM takes 544.6 MB for my current Eclipse process as computed by ps_mem.py (http://www.pixelbeat.org/scripts/ps_mem.py) which computes the real physical memory pages reserved by the Linux 2.6+ kernel. That’s internal Sun JVM overhead of 35% or roughly 200MB!

Any hints about how to decrease this overhead?

Here’s some additional info:

$ ps auxw
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
me       23440  2.4 14.4 1394144 558440 ?      Sl   Oct12 210:41 /usr/bin/java ...

And according to JConsole, the process has used 160 MB of heap and 151 MB of non-heap.

I’m not saying that I cannot afford using extra 200MB for running Eclipse, but if there’s a way to reduce this waste, I’d rather use that 200MB for kernel block device buffers or file cache. In addition, I have similar experience with other Java programs — perhaps I could reduce the overhead for all of them with similar tweaks.

Update: After posting the question, I found previous post to SO:
Why does the Sun JVM continue to consume ever more RSS memory even when the heap, etc sizes are stable?
It seems that I should use pmap to investigate the problem.

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1 Answer

  1. Editorial Team

    I think the reason for the high memory consumption of your Eclipse Environment is the use of SWT. SWT is a native graphic library living outside of the heap of the JVM, and to worsen the situation, the implementation on Linux is not really optimized.

    I don’t think there’s really a chance to reduce the memory consumption of your eclipse environment concerning the memory outside the heap.

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