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Java 1.3 memory SIZE

 
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Timo J
Frequent Advisor

Java 1.3 memory SIZE

HP-UX 1100 & Java 1.3.1.13

When starting even a few lines "Hello World"-type Java application, the SIZE-field of 'top' jumps right over 200M. OS is patched according to instructions found from http://www.hp.com/go/java. Also kernel parameters are set to fill the requisities.

The output of top looks a little bit ugly at least if you look at the SIZE-field of Java-processes. But on the other hand, Glance shows not-so-critical memory consumption. So should I trust Glance on this issue, or what?
As far as I remember, with the older Java 1.3.x-versions and older QPK:s we didn't had this problem. Attachment contains a snippet from 'top'-output.
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4 REPLIES 4
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Shaikh Imran
Honored Contributor

Re: Java 1.3 memory SIZE

Hi,

You will have to rely on the glane report
only as the SIZE column in the top command
is not exactly the size of memory used but...
it's
""Total size of the process in kilobytes. This includes text, data, and stack.""

BTW i saw java running from 2 terminals
ttyp2 & ttyp5 .. Pls try to run it from 1 terminal.

If at all you are really concerned about the memory then i will advise you to use
vmstat & see if the po ( page out ) values are high..

Rest all seems OK to me..


Regards,











I'll sleep when i am dead.
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Steve Steel
Honored Contributor

Re: Java 1.3 memory SIZE

Hi


Indeed top is a bad choice for this

Glance is better

Memory Usage - â What is using all of the memoryâ ?

by:eric.herberholz@hp.com

Last modified: July 26, 2004

Latest version available at external ftp site:

ftp://eh:spear9@hprc.external.hp.com/memory.htm


This site gives you access to some real memory toys to see what is happening.Unsupported but good

Steve
If you want truly to understand something, try to change it. (Kurt Lewin)
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Don Morris_1
Honored Contributor

Re: Java 1.3 memory SIZE

SIZE isn't something that you should really be overly concerned about anyway. That's the *virtual* size of the process -- and I'll bet Java just did a 200Mb+ mmap to set up a data space for the application. RES is the real physical memory used (which is much more important).

SIZE can matter since virtual address space usually directly correlates with swap space reservation (so if you don't have much swap, you're not going to be thrilled if some apps go chewing up the virtual address space), but if I recall correctly - Java uses lazy swap, so you're only going to consume what swap you really need.

In summary -- keep an eye on your swapinfo output, but unless RES also shows a similar large chunk I wouldn't worry about it.
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Mike Stroyan
Honored Contributor
Solution

Re: Java 1.3 memory SIZE

You may be seeing differences in 'top' output that result from changes to top rather than changes to java. Patch PHCO_26020 changed top to report a SIZE based on the total size of more memory regions than before. The change corrects complaints that top sometimes reported a larger "RES" resident size than the "SIZE" virtual memory size.