Debugging high JNI Weak Reference times

[bharat naik]

Hi all,

We used to see a high amount of time spent during the rescan phase of GC,
i..e the weak refs processing part used to take around 140 seconds. This
would occur about 3-4 times for every 70 runs.

We set the following options:  -XX:+ParallelRefProcEnabled  and
 -XX:+PrintReferenceGC to get more details and as a workaround. The time
reduced to ~10 seconds and we see that most of it is spent in resolving JNI
weak references.

I did see a few similar problems on the net but they were all related to
the G1 GC and we use CMS. How does one usually go about debugging further
in this scenario and are there any other options that we could try to help
mitigate this problem?

Java version is:
java version "1.7.0_45"

Java(TM) SE Runtime Environment (build 1.7.0_45-b18)

Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)

These are the relevant GC options:

-XX:+UseCompressedOops

-XX:SurvivorRatio=3

-XX:+UseLargePages

-XX:TargetSurvivorRatio=90

 -XX:+AlwaysPreTouch

-XX:+AggressiveOpts

-XX:+UseNUMA

-XX:+UseTLAB

-XX:+UseParNewGC

-XX:+UseConcMarkSweepGC -

-XX:CMSWaitDuration=90000

-XX:+ParallelRefProcEnabled

-XX:+PrintReferenceGC

-XX:+PrintJNIGCStalls

-XX:ParallelCMSThreads=16

-XX:+CMSScavengeBeforeRemark

-XX:-CMSConcurrentMTEnabled

-XX:CMSInitiatingOccupancyFraction=10

-XX:+UseCMSInitiatingOccupancyOnly


Any help is appreciated!


Thanks,

Bharat.
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