Debugging high JNI Weak Reference times

[Tao Mao]

Hi Bharat,

Please attach your gc log with at least the following options "-verbose:gc
-XX:+PrintGCDetails -XX:+PrintGCTimeStamps"

Regards,
Tao Mao


On Tue, Feb 3, 2015 at 4:31 PM, bharat naik <bharat.2511 at gmail.com> wrote:

> 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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