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I am using a 32bit WinXP with no upgrade in sight, is there a way to limit how much memory Eclipse allocates throughout the day? I am also running Weblogic 10 server in debug mode inside eclipse. After a few hours I have an 700mb STS.exe (eclipse) and 400mb java.exe (server). Is there at least a way to force a GC on eclipse? Here are the settings i surrently use, which seem to me are not being observed.

-vm
C:\bea\jdk160_05\bin\javaw.exe
-showsplash
--launcher.XXMaxPermSize
128M
-vmargs
-Dosgi.requiredJavaVersion=1.5
-Xms40m -Xmx512m
-Dsun.lang.ClassLoader.allowArraySyntax=true

EDIT: here's the monster of a project: Eclipse and Firefox 4. enter image description here

Elijah
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5 Answers5

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is there a way to limit how much memory Eclipse allocates throughout the day?

The values of -Xmx and -XX:MaxPermSize place an upper bound on the memory that the JVM will use.

Is there at least a way to force a GC on eclipse?

AFAIK, no. Even if there was, it probably wouldn't help. The JVM is unlikely to give the memory back to the operating system.

Here are the settings i currently use, which seem to me are not being observed.

Based on what you've said (memory usage 700Mb for eclipse.exe), I'd say the settings ARE being observed.

What can you do to get Eclipse to use less memory?

  • Trim the values of -Xmx and -XX:MaxPermSize. However, if you do this too much you are liable to make Eclipse sluggish ('cos it has to GC more frequently) and ultimately flakey ('cos it will run out of memory and things will start failing with OOMEs)

  • Get rid of superfluous plugins.

  • Switch to a "smaller" Eclipse (e.g. the "Classic" distro) ... though you'll lose some of the J2EE support that you are probably using.

  • Close projects.

  • Close files.

  • Restart Eclipse more often.

But the best solution is to upgrade your platform:

  • Buy some more memory for your PC / laptop. You can probably max it out for a couple of hundred dollars. It is worth it.

  • Switch the OS to Linux. In my experience, Linux is a much better platform for doing Java software development than Windows XP. It seems to do a much better job in terms of both memory and file system management. The performance difference on identical hardware is significant.

    You can always set up your machine to dual boot, so that you can still run XP for other things.

Stephen C
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  • Thanks Stephen for that detailed response. I did get a chuckle about upgrading my PC tho :) I have a corporate noose, with no hope of getting a 64bit OS. That's the crux of my grief. The laptop has plenty of RAM, it's just isn't visible under 32bit os. Sigh. – Elijah Mar 30 '11 at 01:15
  • @Yev - IIRC, upgrading to Linux will help there too ... even with the 32bit version. Another thing you could do is ask for a second PC and offload some of your other stuff (browser, email, MS Office etc) to that machine. – Stephen C Mar 30 '11 at 01:23
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The 700MB of OS level process usuage is consistent with your memory settings. Take 512m for heap + 128m for permgen space + a bit of overhead for the JVM itself.

You cannot force GC. If memory was releasable, JVM would release it. Note that you cannot simply look at OS level process usage as that represents the point where the JVM memory usage peaked. JVM never releases heap or permgen space once it expands to a certain size. It is simply too expensive and not really necessary. The allocated space is in virtual address space of the JVM process. It doesn't represent actual physical memory usage. As physical memory gets tight, the OS will agressively swap out to disk memory pages that haven't been used recently.

So... You need specialized memory analysis tools to get accurate representation of Eclipse memory usage.

If you are seeing a lot of disk activity when there shouldn't be any, the OS may be indeed out of physical memory and doing a lot of swapping. Try closing a few projects or restarting Eclipse. It only takes one plugin with a memory leak to consume all of your available memory.

Konstantin Komissarchik
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1

The ini file memory settings won't help for the Virtual machine. Change VM arguments, as here

Community
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Gangnus
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I'm assuming that you are running BEA JRockit judging by the path to javaw.exe. Note that the -X... options are JVM-specific, so they may not work the same way for JRockit as in Sun's JVM. This link seems to indicate that you should be using

... -Xms:40m -Xmx:512m ...

But setting a heap size limit will only cause Eclipse to fail once it reaches the limit, so you won't solve the real problem. Forcing a GC usually doesn't help; any sane VM will GC periodically or when needed.

Having a 700Mb Eclipse sounds like your Eclipse is either processing large amounts of data, or it is leaking memory. JRockit seems to have a memory leak detector which may be able to give you a hint of where the problem lies.

JesperE
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  • Hi JesperE, i am using Java(TM) SE Runtime Environment (build 1.6.0_05-b13) Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode) – Elijah Mar 30 '11 at 01:07
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Eclipse is very thirsty. Limiting it is most likely to crash it. You really need a new computer.

bmargulies
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