Debugging high JNI Weak Reference times

[bharat naik]

Hi Tao,

Thanks for the reply,but this occurrence was because JNI weak reference
processing isn't done in parallel currently.
A bug has been filed regarding this: JDK-8072498
<https://bugs.openjdk.java.net/browse/JDK-8072498>

Thanks,
Bharat.

On Wed, Feb 25, 2015 at 3:01 PM, Tao Mao <yiyeguhu at gmail.com> wrote:

> 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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>> hotspot-gc-use at openjdk.java.net
>> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>>
>>
>
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