System hangs/freezes for a period during a long running test of Java Application - GC logs show gaps

Oracle reports system freeze/hang during stress testing of their OCMS server for a period of 15-30 seconds. The tests run for a period of upto 120 hours.

System has enough memory and only a portion of it is allocated to heap.

Details are provided as follows - the first set of JVM options are the default and the second set are the tuned options.

I have already suggested testing with JDK6 and comparing the results.

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JDK: 1.5.0_12


JVM settings 1:

-Xloggc:$ORACLE_HOME/gc.log
-XX:+PrintGCDetails
-XX:NewRatio=3
-XX:+UseConcMarkSweepGC
-XX:+UseParNewGC
-XX:PermSize=128m
-XX:MaxPermSize=128m
-Xss128k
-Xmx1280M
-Xms1280M


JVM settings 2:

-Xloggc:$ORACLE_HOME/gc.log
-XX:+PrintGCDetails
-XX:NewSize=32m
-XX:MaxNewSize=32m
-XX:+UseConcMarkSweepGC
-XX:+CMSIncrementalMode
-XX:+CMSIncrementalPacing
-XX:CMSIncrementalDutyCycleMin=0
-XX:CMSIncrementalDutyCycle=10
-XX:+UseTLAB
-XX:+UseParNewGC
-XX:MaxTenuringThreshold=0
-XX:SurvivorRatio=128
-XX:+UseCMSCompactAtFullCollection
-XX:CMSFullGCsBeforeCompaction=0
-XX:PermSize=64m
-XX:MaxPermSize=64m
-Xss128k
-Xmx1280M
-Xms1280M


Configiguration:


Server: (2 CPU, 3.2 GHz, both hyperthreading, with 6 GB RAM)

OS: Linux, RHEL Release 4, update 3, Kernel 2.6.9-34.0.1.0.11.ELsmp

Load: 225 calls/s, approximately 2800 SIP messages/s

CPU Average: 37.21%

Mem Usage: approx 650 - 1000 MB

Max GC Pause: 0.98551 s (from GC Viewer)

Avg GC Pause: 0.052 s