Big GC with unknow reason dragonken at
Tue Jun 24 07:59:30 UTC 2008

First of all, I dunno is it appropriate to ask gc tuning question here.
Please forgive me if I post in wrong place.

Well, I was chat with Sun GC Tuning Team long time ago and seek for gc
tuning advise. The team was dismissed. Today, I google Jon Masamitsu and
finally get here. :>

So, my question is: Any idea why there was a big gc at 51789?

We are using jdk1.6.0_04 on windows32 with this set of vm option:

c:\progra~1\Java\jdk1.6.0_04\bin\java -server -verbose:gc
-XX:+PrintGCDetails -Xloggc:itrade_gc_gc.log -Xms1024M -Xmx1612M
-XX:NewSize=128M -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC
-XX:+UseParNewGC -XX:SurvivorRatio=6 -XX:CMSInitiatingOccupancyFraction=80

51789.930: [Full GC 51789.930: [CMS: 403366K->126465K(917504K), 19.1967956
secs] 430862K->126465K(1032192K), [CMS Perm : 23152K->23072K(23296K)],
19.1972027 secs] [Times: user=0.94 sys=0.17, real=19.19 secs] 

The heap is around 4x% full at that time and the machine has 8G physical
memory. From the logs, it show that it spend 19.19 secs (real), what is
user/sys/real? Any info about it? I guess the vm is spending many time on
memory swapping but task mgr show that the peak is around 4G.

Thanks and Regards,

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