Major problems with frequent Full GCs

[gcrookie]

Hey community,

i have major Full GC problems on one of my jboss machines. Two month ago we thought it is a memory leak or other application issue and changed many parts (corresp. hibernate session and caching).

This time the machine runs 12 days without "bigger" performance and response issues. But today the response time became periodically higher and we had to restart the server.

In GC Log we see - just before restarting the machine - full gc running up to 7 times a minute with up to 6 seconds duration.

We made sure that out application does not call System.gc().

Here the Start Params:

-Xms=3520m -Xmx=3520m -XX:PermSize=128m -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled

I did not find out why the full gc is called (so frequently). Hopefully you can help me with my gc log...

Joe GC rookie

Message was edited by: Jörg Kethur - added gc viewer grafic

Message was edited by: Jörg Kethur added jboss startup params

[jamezp]

What version of JBoss AS, JBoss EAP or WildFly are you using?

--

James R. Perkins

[wdfink]

Sometimes the GC is not the real problem. I've seen often that there is a threshold for number of requests or DB response times, if you reach it the GC becomes crazy because the objects are keept too long in memory and you run out of mem-space which end in a frequent full-GC.

In such situation a bit more memory will help to survive this peak.

In any case I would recommend to monitor as much as possible around that, it often will give you a better understanding why you run into this issue

[gcrookie]

We are using JBoss EAP 6.0.1 GA.

We began to monitor application via java agent - hopefully we see which classes were not able to be Full GCed and resist in old generation.

gc rookie

[wdfink]

As you use EAP you might have access to the knowledgebase, there you might find some helpful articles.

Often it is related to a threshold and after that point the old gen get swamped. If there is no memory leak you may have to adjust the heap sizes and GC strategy.