Re: JBoss-related question

Hi all,

I tried jmap on the Jboss process id and below is the result.

---------------------------------------------

Attaching to process ID 11217, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 1.6.0_03-b05

using thread-local object allocation.
Parallel GC with 2 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 2147483648 (2048.0MB)
   NewSize          = 2686976 (2.5625MB)
   MaxNewSize       = -65536 (-0.0625MB)
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 21757952 (20.75MB)
   MaxPermSize      = 88080384 (84.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 517079040 (493.125MB)
   used     = 86750448 (82.73167419433594MB)
   free     = 430328592 (410.39332580566406MB)
   16.777018848027566% used
From Space:
   capacity = 70189056 (66.9375MB)
   used     = 1130536 (1.0781631469726562MB)
   free     = 69058520 (65.85933685302734MB)
   1.6107012466444912% used
To Space:
   capacity = 89260032 (85.125MB)
   used     = 0 (0.0MB)
   free     = 89260032 (85.125MB)
   0.0% used
PS Old Generation
   capacity = 1431699456 (1365.375MB)
   used     = 122750176 (117.06369018554688MB)
   free     = 1308949280 (1248.3113098144531MB)
   8.573739096259041% used
PS Perm Generation
   capacity = 86114304 (82.125MB)
   used     = 86077472 (82.08987426757812MB)
   free     = 36832 (0.035125732421875MB)
   99.9572289407344% used

-------------------------------------------------

I'm not 100% on how to interpret the result - but looking at the last entry 'PS Perm Generation': 99.9%
used, it doesn't look all that good.
I did restart JBoss and then I tested some stuff, before running jmap. So, this hasn't got to do with re-deployment
withoutrestarting Jboss. 


Håkan Jacobsson - System Developer
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-----Ursprungligt meddelande-----
Från: Guillaume Cottenceau [mailto:gc@mnc.ch]
Skickat: den 8 januari 2008 14:43
Till: Håkan Jacobsson
Kopia: Michael Goldner; pgsql-jdbc@postgresql.org
Ämne: Re: [JDBC] JBoss-related question

Håkan Jacobsson <hakan.jacobsson 'at' relevanttraffic.com> writes:

> Hi all,
>
> Thanx for your comments.
> Actually, yes, I've deployed without restarting JBoss a couple of times. It might be the cause.
> I've restarted the server now and doing some general testing.
>
> This might not solve the problem entirely though, since I tested stuff yesterday and all was fine.
> But today when doing some more testing - the exception suddenly
> was thrown. Without any 'hot re-deployments' (without any
> deployment actually) since I tested yesterday.

Notice that you can easily monitor the size of the permanent
generation with jmap[1]. It will be then very easy to confirm or
not that the deployment process is the rootcause of the out of
memory in the permanent generation space (whether by design -
normally IIRC a class is never unloaded from the permanent
generation - or because of a bug).

In our experience using Tomcat, for which we do *not*
undeploy/deploy applications but rather restart java altogether,
we had to raise the permanent generation (and it's been a stable
fix - it does not delay the problem). Seems that having a lot of
web applications contexts, each with its own jars (hence with
classes loaded separately), and using quite a few struts and jsp
classes, brings a significant amount of data in the permanent
generation.

Notice that even Sun's documentation specifically talks about the
potential need to increase the permanent generation when using
some JSP implementations[2].

Could you please return to this list about the results of your
investigations, whether there is a bug or an issue with
undeploying/deploying in jboss? Don't forget to tell the versions
of java and jboss you're using.

This is a bit offtopic but still quite interesting, I think.

Ref:
[1] http://zarb.org/~gc/html/doc-misc.html#2007-06-06

[2] http://java.sun.com/docs/hotspot/gc5.0/gc_tuning_5.html#1.1.Other%20Considerations%7Coutline

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